László Lendvai
56611960900
Publications - 36
Optimal design of agro-residue filled poly(lactic acid) biocomposites using an integrated CRITIC-CoCoSo multi-criteria decision-making approach
Publication Name: Scientific Reports
Publication Date: 2025-12-01
Volume: 15
Issue: 1
Page Range: Unknown
Description:
In recent years, there has been a rise in environmental awareness, leading to increased efforts to develop eco-friendly materials as alternatives to petroleum-based polymers. This study examined the performance optimization of poly(lactic acid) (PLA) biocomposites filled with agricultural byproducts at concentrations ranging from 0 to 20% by weight, highlighting their potential as substitutes for commodity plastics. The agro-residues used as fillers were flax seed meal and rapeseed straw. A hybrid decision-making algorithm was proposed, utilizing the “criteria importance through inter-criteria correlation” (CRITIC) alongside the “combined compromise solution” (CoCoSo), aimed at identifying the optimal alternative among the evaluated samples. The algorithm considered several attributes, including mechanical traits evaluated via tensile, flexural, and impact tests, hardness, water absorption, biodegradation, and production cost. The findings revealed that the strength properties, including tensile, flexural, impact, and water absorption, were most advantageous for neat PLA. In contrast, the highest modulus values were recorded for the biocomposite filled with 20 wt% rapeseed straw. The biocomposites exhibit increased hardness as agro-waste content rose, with the highest hardness observed in the biocomposite filled with 20 wt% flax seed meal. The study on biodegradation indicates that a higher content of agro-waste promotes disintegration, with flax seed meal emerging as the most effective additive in this context. The findings show that adding various agricultural byproducts in varying amounts affects the evaluated properties differently. Hence, the hybrid CRITIC-CoCoSo optimization approach is utilized to choose the optimal biocomposite. The findings show that the biocomposite with 20 wt% rapeseed straw demonstrated optimal physico-mechanical and biodegradation properties, making it a promising eco-friendly alternative for future applications.
Open Access: Yes
Synergistic effects of annealing heat treatment and lignocellulose fiber incorporation on the thermal, mechanical, and water absorption properties of poly(lactic acid)-based biocomposites
Publication Name: Polymer Composites
Publication Date: 2025-10-10
Volume: 46
Issue: 14
Page Range: 12790-12804
Description:
This study investigates the effect of annealing heat treatment on polymer composites composed entirely of biodegradable components. Poly(lactic acid) (PLA) was used as the matrix material paired with three different types of commercial lignocellulose fibers of varying sizes. Composites containing 10 wt.% fibers were processed through extrusion followed by injection molding. The amorphous (unannealed) and semi-crystalline (annealed) samples were characterized for their morphological, thermal, mechanical, and water absorption properties. Scanning electron microscopic analysis revealed a homogenous distribution of cellulose fibers within the PLA matrix, even though the composite with the smallest fiber size exhibited slight agglomeration. Differential scanning calorimetric measurements indicated that the annealing heat treatment successfully induced crystallization, with the filler particles capable of increasing the extent of crystallinity formed during the annealing heat treatment from 28% to 36%. Based on the tensile tests, as a result of annealing heat treatment, the composites' strength increased from 48–50 to 53–56 MPa, while their Young's modulus increased from 3.1 GPa to 3.3-3.5 GPa. The Charpy impact tests also revealed an enhanced toughness for the samples exposed to the annealing heat treatment. In terms of water absorption, annealing enhanced the hydrophobic nature of PLA. In addition, the semi-crystalline structure formed during the heat treatment also inhibited the highly hydrophilic cellulose fibers from absorbing as much moisture as they did when incorporated inside amorphous PLA; cellulose fibers embedded in the semi-crystalline PLA matrix consequently exhibited less moisture absorption than the ones in amorphous PLA. Highlights: Through annealing, crystallinity was developed in PLA/lignocellulose composites. Lignocellulose fibers facilitated crystallization by acting as a nucleating agent. Crystallized biocomposites exhibited superior mechanical properties Crystalline segments hindered the water absorption of embedded lignocellulose.
Open Access: Yes
DOI: 10.1002/pc.29898
Effect of filament humidity on the properties of material extrusion 3D-printed acrylonitrile butadiene styrene/hexagonal boron nitride composites
Publication Name: Emergent Materials
Publication Date: 2025-01-01
Volume: Unknown
Issue: Unknown
Page Range: Unknown
Description:
This study investigates the effect of filament moisture content on material extrusion (MEX) 3D-printed composites using acrylonitrile butadiene styrene (ABS) as the polymer matrix and 0–10 vol% hexagonal boron nitride (BN) as reinforcement. ABS/BN composites were prepared through batchwise compounding and extruded into MEX-suitable filaments. The filaments were conditioned at 30 °C and 10% or 90% relative humidity (RH) before/during direct feeding into the 3D printer. Specimens were fabricated with raster angles parallel (0°) and perpendicular (90°) to their length. Micro- and macrostructural analyses using scanning electron microscopy and computed tomography revealed intensive void formation, especially in BN-filled composites 3D-printed from humid filaments. This was attributed to BN acting as a physical barrier, hindering the outgassing of evaporated water during 3D printing. Mechanical properties were evaluated using tensile and Charpy impact tests. Based on the tensile test results, neat ABS was the least sensitive to filament moisture, with tensile strength at 0° raster angle dropping from 40.5 MPa to 36.7 MPa as storage RH was increased from 10 to 90%. For composites with 10 vol% BN loading, tensile strength dropped from 34.1 MPa to 22.3 MPa. Charpy impact strength exhibited similar reductions, ascribed to the porous structure of the BN-filled composites caused by the evaporated moisture. Thermal conductivity was also examined, showing slightly superior performance for samples 3D-printed from filaments stored in less humid conditions. For unfilled ABS, the conductivity slightly decreased from 0.188 to 0.185 W/mK, while for 10 vol% BN-filled composite, it dropped from 0.778 to 0.617 W/mK.
Open Access: Yes
Experimental study on the effect of filament-extrusion rate on the structural, mechanical and thermal properties of material extrusion 3D-printed polylactic acid (PLA) products
Publication Name: Progress in Additive Manufacturing
Publication Date: 2025-01-01
Volume: 10
Issue: 1
Page Range: 619-629
Description:
Material extrusion (MEX), also commonly referred to as fused deposition modeling (FDM) or fused filament fabrication (FFF) is currently one of the most commonly used additive manufacturing techniques. The quality of the 3D-printed objects fabricated by MEX methods highly relies on various printing parameters, one of which is the so-called filament extrusion multiplier (k). In this study, 3D-printed parts were prepared by MEX technique during which the material feeding rate was adjusted by varying the extrusion multiplier in the range of 97–105% (k = 0.97–1.05). The fabricated parts were tested for their geometrical, structural, mechanical, and thermal conductivity properties. Based on computed tomographic analysis and scanning electron microscopic images, increasing the k parameter resulted in smaller voids, along with gradually decreasing porosity (from 5.82 to 0.05%). Parallel to the decreasing defects, the thermal conductivity of the parts improved from 0.157 to 0.188 W/mK as determined by light-flash analysis technique. On the other hand, when k was set to ≥ 1.03 the geometrical accuracy declined, the size of the specimens considerably increased relative to the nominal values, especially in the X–Y directions due to excess material getting “squeezed” on the sides of the specimens. This latter phenomenon also resulted in the formation of a number of stress concentration sites, which manifested in the decrease of mechanical properties. Accordingly, the tensile, flexural, and impact strength of the samples improved up to k = 1.03; however, above that it dropped considerably.
Open Access: Yes
Influence of environmental humidity during filament storage on the structural and mechanical properties of material extrusion 3D-printed poly(lactic acid) parts
Publication Name: Results in Engineering
Publication Date: 2024-12-01
Volume: 24
Issue: Unknown
Page Range: Unknown
Description:
Material extrusion (MEX) is one of the most widely used additive manufacturing techniques these days. This study investigates how the properties of MEX 3D-printed objects depend on the relative humidity (RH) conditions in which filaments are stored before and during the manufacturing process. Poly(lactic acid) (PLA) filament was drawn directly from a humidity-controlled chamber into the MEX 3D printer's nozzle. For each set of samples, the filaments were conditioned under different RH conditions, ranging from 10 % to 90 %. The macrostructure of the fabricated products was characterized using computed tomography, revealing increased porosity at higher RH values (from 0.84 % to 4.42 %). The increased porosity at higher storage RH is attributed to under-extrusion and volatile entrapment due to excess moisture. With growing storage RH, the melt flow rate of PLA also gradually increased, indicating a plasticizing effect of humidity on the biopolymer. Gel permeation chromatography and differential scanning calorimetry analyses were conducted to determine whether hydrolytic chain scission took place when PLA was processed in the presence of excessive moisture. Neither measurement indicated any considerable alteration in molecular integrity and crystalline structure as a function of storage RH. Mechanical tests, however, revealed a reduced load-bearing capacity of the manufactured PLA specimens. Flexural strength decreased from 103.0 to 99.6 MPa, and the impact strength dropped from 18.2 to 16.2 kJ/m2, which is ascribed to the increasing size of pores inside the specimens with increasing storage RH. These findings should be taken into account when designing and processing PLA products by MEX-based additive manufacturing.
Open Access: Yes
The rise of interdisciplinarity: A new era in polymer research?
Publication Name: Express Polymer Letters
Publication Date: 2024-10-01
Volume: 18
Issue: 10
Page Range: 962-963
Description:
No description provided
Open Access: Yes
Thermoplastic Starch Processed under Various Manufacturing Conditions: Thermal and Electrical Properties
Publication Name: Biomacromolecules
Publication Date: 2024-09-09
Volume: 25
Issue: 9
Page Range: 5938-5948
Description:
Eco-friendly materials like carbohydrate-based polymers are important for a sustainable future. Starch is particularly promising because of its biodegradability and abundance but its processing to thermoplastic starch requires optimization. Here we developed thermoplastic maize starch materials based on three manufacturing protocols, namely: (1) starch/glycerol manual mixing and extrusion, (2) starch/glycerol manual mixing, extrusion, and kneading, (3) starch/glycerol/water manual mixing and kneading. The physical properties were investigated by differential scanning calorimetry, thermogravimetric analysis, and broadband dielectric spectroscopy. As expected from a partially miscible blend, the dielectric spectra revealed two distinct α-relaxations for the glycerol-rich and the starch-rich phases, respectively. By employing kneading after extrusion, the miscibility between the two phases was found to improve based on thermal and dielectric methods. Moreover, the addition of water during the premixing stage was observed to facilitate phase separation between starch and glycerol, with the α-relaxation dynamics of the latter being comparable to pure glycerol.
Open Access: Yes
Selection of straw waste reinforced sustainable polymer composite using a multi-criteria decision-making approach
Publication Name: Biomass Conversion and Biorefinery
Publication Date: 2024-09-01
Volume: 14
Issue: 17
Page Range: 21007-21017
Description:
The valorization of straw waste as a sustainable and eco-friendly resource in polymer composites is critical for resource recycling and environmental preservation. Therefore, many research works are being carried out regarding the development of wheat straw-based polymer composites to identify the reinforcing potential of these sustainable resources. In this study, three different sizes of wheat straw fibers (60–120 mesh, 35–60 mesh, and 18–35 mesh) were used, and their different ratios (0, 2.5, 5, 10, and 20% by weight) were systematically investigated for the physical and mechanical properties of polypropylene-based sustainable composites. The results indicated that the evaluated composites’ properties are strongly dependent on the quantity and size of the utilized wheat straw. Therefore, a preference selection index was applied to rank the developed sustainable polymer composites to select the best composition. Various properties of the composite materials were considered as criteria for ranking the alternatives, namely tensile strength and modulus, flexural stress at conventional deflection and flexural modulus, impact strength, density, water absorption, material cost, and carbon footprint. The decision-making analysis suggests the alternative with wheat straw content of 20 wt.% (35–60 mesh size) dominating the performance by maximizing the beneficial criteria and minimizing the non-beneficial criteria, making it the most suitable alternative. This study will significantly help formulation designers to deal with the amount and size issues when developing polymeric composites.
Open Access: Yes
Agricultural by-product filled poly(lactic acid) biocomposites with enhanced biodegradability: The effect of flax seed meal and rapeseed straw
Publication Name: Composites Part C Open Access
Publication Date: 2024-07-01
Volume: 14
Issue: Unknown
Page Range: Unknown
Description:
The purpose of this research was to develop “green” materials by combining poly(lactic acid) (PLA) with two agricultural by-products, namely flax seed meal (FSM) and rapeseed straw (RSS). The natural fillers (0–20 wt.%) were mixed with PLA through extrusion and then injection molded into specimens. The samples were analyzed for their thermal, morphological, mechanical, and physical features and biodegradability. Thermal properties and crystallinity were analyzed using Differential Scanning Calorimetry (DSC), while the morphology was investigated by Scanning Electron Microscopy (SEM). Mechanical properties were characterized through tensile, flexural, and impact measurements, while surface hardness was evaluated by Shore D tests. Water absorption and biodegradability of the samples were also examined. DSC measurements revealed a nucleating effect of both bio-fillers. Based on the tensile tests, major improvement in stiffness was found with the biocomposites having up to ∼16 % higher Young's modulus than neat PLA (2.5 GPa). It came, however, at the cost of tensile strength, which decreased from 56 to 51 MPa even in the presence of the lowest amount (2.5 wt.%) of FSM. Loss in strength was due to the limited adhesion between the components, as also supported by SEM images. The hardness slightly (1–2 %) improved in the presence of even 2.5 wt.% bio-filler and it remained at that level at higher filler loading as well. Laboratory-scale composting revealed that both fillers facilitated biodegradation with FSM being superior. In the presence of 10–20 wt.% FSM, the rate of decomposition was found to be twice as fast compared to neat PLA.
Open Access: Yes
Thermal, thermomechanical and structural properties of recycled polyethylene terephthalate (rPET)/waste marble dust composites
Publication Name: Heliyon
Publication Date: 2024-02-15
Volume: 10
Issue: 3
Page Range: Unknown
Description:
The main objective of this work is to review the capability of using waste marble dust (MD) particles as reinforcing materials in recycled polymeric composites to achieve environmentally friendly materials. In the present study, polymer composites were fabricated from recycled polyethylene terephthalate (rPET) and MD and then analyzed for their structural and thermal properties. Preparation of rPET-based composites containing 0–20 wt% MD was carried out through extrusion and injection molding. For their characterization Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA) were applied. The DSC analysis revealed a nucleating effect of MD on rPET, which was manifested in a higher crystallization temperature (196.7 °C ⇒ 204.4 °C); however, the marble particles were also found to hamper chain mobility, thereby decreasing the crystallinity ratio (23.7 % ⇒ 19.2 %) of rPET and altering its crystalline structure. According to the TGA measurements, a slight increase occurred in the thermal stability of rPET, its major decomposition temperature increased from 446 °C to 451 °C when 20 wt% MD was incorporated into it. DMA showed an improved stiffness in the entire investigated temperature range for MD-filled composites versus neat rPET. Additionally, several factors were derived from the DMA data, including the effectiveness factor, degree of entanglement, and reinforcing efficiency factor which all suggested a decent interaction between the components indicating a proper reinforcing ability of marble powder. However, above 5 wt% MD content the reinforcing efficiency deteriorated due to the agglomeration of filler particles, which was also supported by scanning electron microscopic images.
Open Access: Yes
The Effect of Wood Flour Incorporation on the Properties of Injection Molded Poly(Lactic Acid) Products †
Publication Name: Engineering Proceedings
Publication Date: 2024-01-01
Volume: 79
Issue: 1
Page Range: Unknown
Description:
Wood flour-paired poly(lactic acid) (PLA)-based biocomposites were fabricated with filler contents of 0, 2.5, 5, 10, and 20 wt.%. The samples were processed through extrusion followed by injection molding. The injection-molded specimens were subjected to tensile tests, impact tests, and water absorption tests. Based on the results, increasing the amount of lignocellulose fibers effectively improved the modulus of PLA from 2.8 to 3.6 GPa at 20 wt.% wood flour loading; however, this came at the cost of strength, which dropped from 55.0 to 48.8 MPa. Additionally, the incorporation of lignocellulose increased the hydrophilicity of the composites, resulting in a threefold increase in water absorption at 10 wt.% filler content. These results provide insight into the effects of embedding lignocellulose fibers into PLA.
Open Access: Yes
Foam Injection Molding of Poly(Lactic Acid) with Azodicarbonamide-Based Chemical Blowing Agent †
Publication Name: Engineering Proceedings
Publication Date: 2024-01-01
Volume: 79
Issue: 1
Page Range: Unknown
Description:
In this study, poly(lactic acid) (PLA)-based biopolymer foams were prepared through injection molding using the high-pressure foam injection molding method, also referred to as “breathing mold” technique, with the addition of various amounts (0, 1, 2, and 4 wt.%) of azodicarbonamide-based chemical blowing agent (CBA). The prepared samples were analyzed for their macrostructure using computed tomography (CT) while the mechanical properties were determined by flexural and Charpy impact tests. CT analysis revealed a finer foam cell structure and decreasing shell thickness with increasing CBA content. Regarding the mechanical properties, the specific flexural strength and flexural modulus of PLA were improved as a result of foaming; however, this improvement came at the cost of a slight deterioration in impact strength.
Open Access: Yes
Comparison of Mechanical Properties of PLA-Based Biocomposites Filled with Different Agricultural By-Products
Publication Name: Advances in Transdisciplinary Engineering
Publication Date: 2024-01-01
Volume: 59
Issue: Unknown
Page Range: 486-493
Description:
In this study, biopolymer composites were developed using poly(lactic acid) (PLA) as a polymer matrix. Various agricultural by-products, including flax seed meal, rapeseed straw, and mustard seed meal, were added as a reinforcement. The research aimed to provide insight into the valorization of cheap, readily available residues generated in the agricultural industry and assess the mechanical properties of composites prepared using them. The experimental fabrication was conducted by compounding PLA with agro-waste particles in 10 and 20 wt% concentrations. These components were melt mixed with a twin-screw extruder and injection molded into standardized forms. The resulting fabricated composites were tested for tensile and flexural mechanical properties and hardness. Through scanning electron microscopy, images of the natural particles were taken to better understand their structure, geometry, and possible ways of interaction between them and the PLA matrix. The results of quasi-static mechanical tests suggest that using agricultural by-products can effectively improve Young's modulus and flexural modulus of PLA but at the cost of tensile and flexural strength, which decreased with the by-products' introduction. Of the three agro-waste options, rapeseed straw emerged as the superior choice because it only marginally reduced the mechanical strength of the PLA and enhanced its stiffness the most. Hardness was the least affected property, test results showed that the added fillers did not substantially change the polymer matrix's hardness.
Open Access: Yes
DOI: 10.3233/ATDE240584
Effect of Maleated Compatibilizer on the Mechanical Properties of PLA/Mustard Waste Biocomposites
Publication Name: Chemical Engineering Transactions
Publication Date: 2024-01-01
Volume: 114
Issue: Unknown
Page Range: 775-780
Description:
Natural fiber polymer composites of biodegradable poly(lactic acid) (PLA) and mustard waste were fabricated with the addition of various amounts (0.25-2.00 wt.%) of maleic anhydride grafted PLA (PLA-g-MA), which was used as a coupling agent to improve interfacial adhesion between the components and thereby enhance the mechanical features of the biocomposite. PLA-g-MA was synthesized in-house by reactive melt grafting using dicumyl peroxide as a free grafting initiator. Preparation of the biocomposite samples was carried out using a twin screw extruder and an injection molding machine. The effect of PLA-g-MA concentration on the samples’ mechanical traits and surface hardness was investigated. Mechanical properties were determined using uniaxial tensile tests, flexural tests, and Charpy impact tests; additionally, the surface hardness was tested with a Shore D indenter. The tensile tests revealed that even the lowest amount (0.25 wt.%) of PLA-g-MA was sufficient to effectively improve the interfacial adhesion between PLA and mustard waste, as manifested in an increased tensile strength (34 to 39 MPa). Similarly, the flexural and the Charpy impact strength also exceeded that of neat PLA/mustard waste biocomposite by 31 % and 45 %, respectively. The addition of compatibilizer in higher concentrations than 0.25 wt.% did not improve the mechanical properties further, ascribed to the excess PLA-g-MA plasticizing the composite. Based on Shore D testing, the compatibilization did not affect the surface hardness of the biocomposites significantly.
Open Access: Yes
DOI: 10.3303/CET24114130
The Effect of Drying of Glycerol-Plasticized Starch upon Its Dielectric Relaxation Dynamics and Charge Transport
Publication Name: Journal of Polymers and the Environment
Publication Date: 2023-12-01
Volume: 31
Issue: 12
Page Range: 5389-5400
Description:
Carbohydrate polymers are promising materials for an eco-friendly future due to their biodegradability and abundance in nature. However, due to their molecular characteristics and hydrophilicity, are often complicated to be investigated via spectroscopic methods. Thermoplastic starch plasticized by glycerol was prepared through melt processing conditions using twin screw extruder. Here we show how the presence of water molecules affects the dielectric response and charge transport dynamics over broad frequency (10−1 to 107 Hz) and temperature (− 140 to 150 oC) ranges. Overall, 7 dielectric processes were observed and differentiation between electronic and ionic conductivities was achieved. Two segmental relaxation processes were observed for each sample, ascribed to the starch-rich and glycerol-rich phases. Although the timescales of the two segmental relaxations were found different, both arise from the same temperature, giving thus an alternative explanation on what is reported in the literature. The origin of the σ-relaxation was attributed to hydrogen ions and was found to be proportional to the ionic conductivity according to the Barton, Nakajima and Namikawa relation. The presence of water molecules was found to enhance the ionic conductivity, indicating that water contributes charge carriers when compared to the dried sample. Graphical Abstract: [Figure not available: see fulltext.]
Open Access: Yes
Lignocellulosic agro-residue/polylactic acid (PLA) biocomposites: Rapeseed straw as a sustainable filler
Publication Name: Cleaner Materials
Publication Date: 2023-09-01
Volume: 9
Issue: Unknown
Page Range: Unknown
Description:
The main objective of this study is to review the applicability of rapeseed straw (RSS) as a sustainable filler material in polylactic acid (PLA)-based biocomposites. The effect of different RSS particle sizes and concentrations (0–20 wt%) on the mechanical, morphological, thermal, and water absorption properties was investigated. The composites were fabricated by melt compounding using a twin-screw extruder followed by injection molding. The mechanical properties were analyzed through tensile and flexural tests and Charpy impact tests. The morphology of the samples was investigated by scanning electron microscopy (SEM). The thermal properties and the crystallinity of the composites were determined through differential scanning calorimetry (DSC). Mechanical properties revealed an increasing stiffness of PLA as a function of RSS loading, albeit at the cost of strength. SEM images have shown a limited interfacial adhesion between PLA and the straw, which was suggested to be responsible for the decreased strength values. Based on the DSC measurements, the RSS fibers facilitated the nucleation in the composites, thereby decreasing the cold crystallization temperature of PLA. The conducted experiments demonstrated that environmentally friendly and economically attractive biocomposites can be fabricated by substituting part of the PLA with RSS as a lignocellulosic by-product.
Open Access: Yes
Thermally conductive and electrically resistive acrylonitrile butadiene styrene (ABS)/boron nitride composites: Optimal design using a multi-criteria decision-making approach
Publication Name: Journal of Materials Research and Technology
Publication Date: 2023-09-01
Volume: 26
Issue: Unknown
Page Range: 8776-8788
Description:
The purpose of this work is to propose a decision-making algorithm to select the optimal composite material for thermally conductive but electrically insulating applications, such as microelectronic packaging heat sinks, diodes, and other electronic devices. In particular, an algorithm based on the criteria importance through inter-criteria correlation (CRITIC) and additive ratio assessment (ARAS) methods are used to evaluate several conflicting attributes. The evaluated samples were acrylonitrile butadiene styrene (ABS) composites filled with 0–30 vol% of boron nitride (BN) particles and prepared through melt compounding. The performance attributes considered through testing were heat conductivity, electrical resistivity, density, hardness, and tensile properties (Young's modulus, tensile strength, and elongation). As expected, the composite containing 30 vol% BN exhibited the highest heat conductivity, electrical resistivity, and Young's modulus. Meanwhile, unfilled ABS had the highest elongation at break, tensile strength, and lowest density. With respect to hardness, the 1 vol% BN-loaded composite proved to be superior. Therefore, the experimental data revealed a considerable compositional dependence with no obvious trend. The optimal composition was identified by adopting the CRITIC-ARAS multi-criteria decision-making algorithm, based on which the 30 vol% BN-containing composite was dominant among all the prepared samples. A validation through other decision-making techniques was performed to support the robustness of the proposed technique. Additionally, a sensitivity analysis was carried out on several weight exchange scenarios to see the stability of the ranking results.
Open Access: Yes
Mechanical and morphological properties of PP/XNBR blends produced with rubber latex
Publication Name: Journal of Polymer Research
Publication Date: 2023-07-01
Volume: 30
Issue: 7
Page Range: Unknown
Description:
In this work, polypropylene (PP)/carboxylated acrylonitrile butadiene rubber (XNBR) binary blends were prepared with the elastomer component dosed in its suspension (latex) form into the polymer matrix during melt compounding. For this purpose, samples containing 0-20 wt.% rubber were prepared using two different PP grades as matrices with lower and higher viscosity. Analogous reference samples with the same composition were also fabricated using traditional melt mixing by introducing the rubber in its dry, bulk form in order to analyze the efficiency of the latex route. Mechanical, thermomechanical and morphological analyses were used to investigate the structure-property relationships of the blends. Based on the SEM images the average domain size of the dispersed XNBR domains became markedly smaller when the rubber was introduced in its suspension form into the PP. Based on the Charpy impact tests and the tensile test results, the decreased rubber domain size led to improved ductility and toughness. The improvement was more prominent when the difference between the viscosity of the PP matrix and the XNBR rubber was higher.
Open Access: Yes
Waste marble dust-filled sustainable polymer composite selection using a multi-criteria decision-making technique
Publication Name: Arabian Journal of Chemistry
Publication Date: 2023-06-01
Volume: 16
Issue: 6
Page Range: Unknown
Description:
This research works with the optimal design of marble dust-filled polymer composites using a multi-criteria decision-making (MCDM) technique. Polylactic acid (PLA) and recycled polyethylene terephthalate (rPET)-based composites containing 0, 5, 10, and 20 wt% of marble dust were developed and evaluated for various physicomechanical and wear properties. The results showed that the incorporation of marble dust improved the modulus and hardness of both PLA and rPET. Moreover, a marginal improvement in flexural strength was noted while the tensile and impact strength of the matrices were deteriorating due to marble dust addition. The outcomes of wear analysis demonstrated an improvement in wear resistance up until 10 wt% filler reinforcement, after which the incidence of dust particles peeling off from the matrix was observed, thereby reducing its efficiency. The best tensile modulus of 3.23 GPa, flexural modulus of 4.39 GPa, and hardness of 83.95 Shore D were obtained for 20 wt% marble dust-filled PLA composites. The lowest density of 1.24 g/cc and the highest tensile strength of 57.94 MPa were recorded for neat PLA, while the highest impact strength of 30.94 kJ/m2 was recorded for neat rPET. The lowest wear of 0.01 g was obtained for the rPET containing 5 wt% marble dust content. The experimental results revealed that for the examined criteria, the order of composite preference is not the same. Therefore, the optimal composite was identified by adopting a preference selection index-based MCDM technique. The findings demonstrated that the 10 wt% marble dust-filled PLA composite appears to be the best solution with favorable physical, mechanical, and wear properties.
Open Access: Yes
Performance Optimization of Lignocellulosic Fiber-Reinforced Brake Friction Composite Materials Using an Integrated CRITIC-CODAS-Based Decision-Making Approach
Publication Name: Sustainability Switzerland
Publication Date: 2023-06-01
Volume: 15
Issue: 11
Page Range: Unknown
Description:
A hybrid multicriteria decision-making (MCDM) framework, namely “criteria importance through inter-criteria correlation-combinative distance-based assessment” (CRITIC-CODAS) is introduced to rank automotive brake friction composite materials based on their physical and tribological properties. The ranking analysis was performed on ten brake friction composite material alternatives that contained varying proportions (5% and 10% by weight) of hemp, ramie, pineapple, banana, and Kevlar fibers. The properties of alternatives such as density, porosity, compressibility, friction coefficient, fade-recovery performance, friction fluctuation, cost, and carbon footprint were used as selection criteria. An increase in natural fiber content resulted in a decrease in density, along with an increase in porosity and compressibility. The composite with 5 wt.% Kevlar fiber showed the highest coefficient of friction, while the 5 wt.% ramie fiber-based composites exhibited the lowest levels of fade and friction fluctuations. The wear performance was highest in the composite containing 10 wt.% Kevlar fiber, while the composite with 10 wt.% ramie fiber exhibited the highest recovery. The results indicate that including different fibers in varying amounts can affect the evaluated performance criteria. A hybrid CRITIC-CODAS decision-making technique was used to select the optimal brake friction composite. The findings of this approach revealed that adding 10 wt.% banana fiber to the brake friction composite can give the optimal combination of evaluated properties. A sensitivity analysis was performed on several weight exchange scenarios to see the stability of the ranking results. Using Spearman’s correlation with the ranking outcomes from other MCDM techniques, the suggested decision-making framework was further verified, demonstrating its effectiveness and stability.
Open Access: Yes
DOI: 10.3390/su15118880
Valorization of Waste Wood Flour and Rice Husk in Poly(Lactic Acid)-Based Hybrid Biocomposites
Publication Name: Journal of Polymers and the Environment
Publication Date: 2023-02-01
Volume: 31
Issue: 2
Page Range: 541-551
Description:
This study explores the possibility of developing a new class of hybrid particulate-filled biocomposites using wood flour and rice husk wastes as environmentally friendly additives to poly(lactic acid) (PLA) as matrix material. Samples were prepared with fillers of different concentrations (0, 2.5, 5, 7.5 and 10 wt %), while the ratio of wood flour and rice husk was fixed at 1:1 in all cases. The preparation of biocomposites was performed through extrusion using a twin-screw extruder. Subsequently, they were formed into specimens by injection molding. Mechanical, thermal, thermomechanical, and morphological properties were examined. The addition of natural waste particles resulted in a remarkable improvement both in tensile and flexural modulus; however at a cost of impact strength and tensile strength. Meanwhile, flexural stress at conventional strain values were barely affected by the presence of wood flour and rice husk. The SEM images confirmed that there is a limited interfacial adhesion between the components, which supports the results obtained during mechanical tests. Both the differential scanning calorimetry (DSC) and the dynamic mechanical analysis indicated that the glass transition temperature of PLA was not affected by the incorporation of filler particles; however, the crystalline structure was gradually altered with increasing filler loading according to the DSC. Additionally, the particles were observed acting as nucleating agents, thereby increasing the overall crystallinity of PLA.
Open Access: Yes
The effect of coupling agent on the mechanical properties of injection molded polypropylene/wheat straw composites
Publication Name: Acta Technica Jaurinensis
Publication Date: 2022-11-30
Volume: 15
Issue: 4
Page Range: 232-238
Description:
The objective of this work is to evaluate the effect of maleic anhydride-grafted polypropylene (MAPP) as coupling agent in polypropylene (PP)-based composites filled with ground wheat straw (WS) particles. The WS and the MAPP content in the composites was 10 wt% and 2 wt%, respectively. The samples were fabricated through melt compounding using a twin-screw extruder and then formed into dumbbell-shaped specimens by injection molding. The mechanical properties of neat PP and the composites with and without coupling were evaluated based on tensile and flexural tests and dynamic mechanical analyses (DMA). The experimental results showed that incorporating WS into the PP reduces its tensile strength by ~3 MPa, while improving its Young’s modulus by 0.14 GPa. The addition of MAPP compensated for the loss in tensile strength without affecting the modulus. Similar observations were made during the flexural tests as well, in which case, however, there was no loss revealed in the strength in the presence of WS due to the different types of load. The results of DMA analyses indicated an improved stiffness of WS-containing samples throughout the whole analyzed temperature range of 20-120 °C as a consequence of reduced chain mobility of PP caused by the stiff straw particles.
Open Access: Yes
Fabrication of Europium-Doped Barium Titanate/Polystyrene Polymer Nanocomposites Using Ultrasonication-Assisted Method: Structural and Optical Properties
Publication Name: Polymers
Publication Date: 2022-11-01
Volume: 14
Issue: 21
Page Range: Unknown
Description:
In the current work, europium-doped barium titanate particles were used as filler material and polystyrene was used as a matrix to fabricate Ba1−3x /2Eux TiO3 /PS polymer nanocomposites with x = 0, 0.005, 0.015 and 0.025. A solid-state reaction was used to synthesize filler particles and the solvent evaporation method was used to form polymer nanocomposites. The effects of ultrasonic treatment were also studied in the formation of nanocomposite materials. The quantitative and qualitative studies were conducted using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), and ultraviolet-visible (UV-Vis) characterization techniques. The XRD data and FTIR data confirm the incorporation of filler particles in the polymer matrix. FE-SEM data confirms that the particles are in the nanophase. The optical band gap was directly affected by the filler particles and it started to reduce as Eu concentration started to increase.
Open Access: Yes
Optimization on physicomechanical and wear properties of wood waste filled poly(lactic acid) biocomposites using integrated entropy-simple additive weighting approach
Publication Name: South African Journal of Chemical Engineering
Publication Date: 2022-07-01
Volume: 41
Issue: Unknown
Page Range: 193-202
Description:
The present research work develops an evaluation method based on the hybrid entropy-simple additive weighting approach to select the best biocomposite material based on several potentially conflicting criteria. Poly(lactic acid) (PLA) biocomposites with varying proportions of wood waste (0, 2.5, 5, 7.5, and 10 by weight) was developed and evaluated for physical, mechanical, and sliding wear properties. The biocomposite containing 10 wt.% wood waste exhibited the lowest density (1.183 g/cm3) and highest modulus properties (tensile modulus = 2.97 GPa; compressive modulus = 3.46 GPa; and flexural modulus = 4.03 GPa). The bare PLA exhibited the highest strength properties (tensile strength = 57.96 MPa; compressive strength = 105.67 MPa; impact strength = 15.25 kJ/m2), whereas flexural strength (100.43 MPa) was the highest for 5 wt.% wood waste filled biocomposite. The wear of PLA decreased with 2.5 wt.% wood waste incorporated and increased with further addition of wood waste. The experimental results revealed a high compositional dependence with no discernible trend. As a result, prioritizing biocomposites' performance to choose the best from various biocomposite alternatives becomes tough. Therefore, a multi-criteria decision-making process based on a hybrid entropy-simple additive weighting approach was applied to find the optimal biocomposite by taking the experimental results as the selection criterion. The results show that the 2.5 wt.% wood waste added PLA biocomposite proved to be the best solution with optimal physical, mechanical, and wear properties. The validation with other decision-making models supports the robustness of the proposed approach in that the 2.5 wt.% wood waste added PLA biocomposite is the most dominating. This study contributes by providing preferences for the selection criteria and assessing the best alternative from the available PLA biocomposites.
Open Access: Yes
Optimal Design of Wood/Rice Husk-waste-Filled PLA Biocomposites Using Integrated CRITIC–MABAC-Based Decision-Making Algorithm
Publication Name: Polymers
Publication Date: 2022-07-01
Volume: 14
Issue: 13
Page Range: Unknown
Description:
Based on the criteria importance through inter-criteria correlation (CRITIC) and the multi-attributive border approximation area comparison (MABAC), a decision-making algorithm was developed to select the optimal biocomposite material according to several conflicting attributes. Poly(lactic acid) (PLA)-based binary biocomposites containing wood waste and ternary biocompos-ites containing wood waste/rice husk with an overall additive content of 0, 2.5, 5, 7.5 and 10 wt.% were manufactured and evaluated for physicomechanical and wear properties. For the algorithm, the following performance attributes were considered through testing: the evaluated physical (density, water absorption), mechanical (tensile, flexural, compressive and impact) and sliding wear proper-ties. The water absorption and strength properties were found to be the highest for unfilled PLA, while modulus performance remained the highest for 10 wt.% rice husk/wood-waste-added PLA biocomposites. The density of PLA biocomposites increased as rice husk increased, while it decreased as wood waste increased. The lowest and highest density values were recorded for 10 wt.% wood waste and rice husk/wood-waste-containing PLA biocomposites, respectively. The lowest wear was exhibited by the 5 wt.% rice husk/wood-waste-loaded PLA biocomposite. The experimental results were composition dependent and devoid of any discernible trend. Consequently, prioritizing the performance of PLA biocomposites to choose the best one among a collection of alternatives became challenging. Therefore, a decision-making algorithm, called CRITIC–MABAC, was used to select the optimal composition. The importance of attributes was determined by assigning weight using the CRITIC method, while the MABAC method was employed to assess the complete ranking of the biocomposites. The results achieved from the hybrid CRITIC–MABAC approach demonstrated that the 7.5 wt.% wood-waste-added PLA biocomposite exhibited the optimal physicomechanical and wear properties.
Open Access: Yes
Thermal and Sliding Wear Properties of Wood Waste-Filled Poly(Lactic Acid) Biocomposites
Publication Name: Polymers
Publication Date: 2022-06-01
Volume: 14
Issue: 11
Page Range: Unknown
Description:
In our study, the effects of wood waste content (0, 2.5, 5, 7.5, and 10 wt.%) on thermal and dry sliding wear properties of poly(lactic acid) (PLA) biocomposites were investigated. The wear of developed composites was examined under dry contact conditions at different operating parameters, such as sliding velocity (1 m/s, 2 m/s, and 3 m/s) and normal load (10 N, 20 N, and 30 N) at a fixed sliding distance of 2000 m. Thermogravimetric analysis demonstrated that the inclusion of wood waste decreased the thermal stability of PLA biocomposites. The experimental results indicate that wear of biocomposites increased with a rise in load and sliding velocity. There was a 26–38% reduction in wear compared with pure PLA when 2.5 wt.% wood waste was added to composites. The Taguchi method with L25 orthogonal array was used to analyze the sliding wear behavior of the developed biocomposites. The results indicate that the wood waste content with 46.82% contribution emerged as the most crucial parameter affecting the wear of PLA biocomposites. The worn surfaces of the biocomposites were examined by scanning electron microscopy to study possible wear mechanisms and correlate them with the obtained wear results.
Open Access: Yes
Development and characterization of composites produced from recycled polyethylene terephthalate and waste marble dust
Publication Name: Polymer Composites
Publication Date: 2022-06-01
Volume: 43
Issue: 6
Page Range: 3951-3959
Description:
The current paper presents the results of a study on the processing and characterization of waste marble powder-reinforced recycled polyethylene terephthalate (rPET) composites. Samples with up to 20 wt% marble dust (MD) content were produced with twin-screw extrusion followed by injection molding. Subsequently, the morphological and mechanical features and the wear resistance of the developed composites were studied. In terms of mechanical properties, the incorporation of MD steadily improved both the tensile and flexural modulus of rPET, while the strength values showed an optimum at 2.5–5.0 wt%, depending on the mode of loading. Above the optimal MD concentration, the strength values deteriorated, however, even at maximum (20 wt%) marble content they were still similar to that of neat rPET, which proves the potential of utilizing waste MD in this specific polymer as filler material. The surface hardness of the fabricated samples also gradually improved with higher marble content, yet it came at the cost of impact toughness. The analysis of wear performance revealed an increasing resistance against wear up to 5.0 wt% filler loading, above which the dust particles got easily peeled off from the matrix, decreasing its efficiency.
Open Access: Yes
DOI: 10.1002/pc.26669
Optimal Design of Ceramic Based Hip Implant Composites Using Hybrid AHP-MOORA Approach
Publication Name: Materials
Publication Date: 2022-06-01
Volume: 15
Issue: 11
Page Range: Unknown
Description:
Designing excellent hip implant composite material with optimal physical, mechanical and wear properties is challenging. Improper hip implant composite design may result in a premature component and product failure. Therefore, a hybrid decision-making tool was proposed to select the optimal hip implant composite according to several criteria that are probably conflicting. In varying weight proportions, a series of hip implant composite materials containing different ceramics (magnesium oxide, zirconium oxide, chromium oxide, silicon nitride and aluminium oxide) were fabricated and evaluated for wear and physicomechanical properties. The density, void content, hardness, indentation depth, elastic modulus, compressive strength, wear, and fracture toughness values were used to rank the hip implant composites. It was found that the density and void content of the biocomposites remain in the range of 3.920–4.307 g/cm3 and 0.0021–0.0089%, respectively. The composite without zirconium oxide exhibits the lowest density (3.920 g/cm3), while the void content remains lowest for the composite having no chromium oxide content. The highest values of hardness (28.81 GPa), elastic modulus (291 GPa) and fracture toughness (11.97 MPa.m1/2) with the lowest wear (0.0071 mm3/million cycles) were exhibited by the composites having 83 wt.% of aluminium oxide and 10 wt.% of zirconium oxide. The experimental results are compositional dependent and without any visible trend. As a result, selecting the best composites among a group of composite alternatives becomes challenging. Therefore, a hybrid AHP-MOORA based multi-criteria decision-making approach was adopted to choose the best composite alternative. The AHP (analytic hierarchy process) was used to calculate the criteria weight, and MOORA (multiple objective optimisation on the basis of ratio analysis) was used to rank the composites. The outcomes revealed that the hip implant composite with 83 wt.% aluminium oxide, 10 wt.% zirconium oxide, 5 wt.% silicon nitride, 3 wt.% magnesium oxide, and 1.5 wt.% chromium oxide had the best qualities. Finally, sensitivity analysis was conducted to determine the ranking’s robustness and stability concerning the criterion weight.
Open Access: Yes
DOI: 10.3390/ma15113800
Physical, mechanical, and thermal properties of Dalbergia sissoo wood waste-filled poly(lactic acid) composites
Publication Name: Polymer Composites
Publication Date: 2021-09-01
Volume: 42
Issue: 9
Page Range: 4380-4389
Description:
The present work intended to investigate the effect of Dalbergia sissoo wood waste on physical, mechanical, and thermal properties of poly(lactic acid) (PLA)-based composites. The composite specimens, containing wood waste (2.5%, 5%, 7.5%, and 10% by weight) mixed with PLA granules, were prepared by melt compounding. It was found that increased wood waste content resulted in higher modulus, porosity, and water absorption with decreased density, tensile strength, impact strength, and stress at break. Nevertheless, the flexural strength values of the composites were similar to unfilled PLA and they remained almost constant irrespective of the wood waste content. Differential scanning calorimetry analysis revealed that the presence of wood waste content increased the glass transition and cold crystallization temperature of the PLA composites. Moreover, the fractured surfaces of the composites were examined with a scanning electron microscope to study the possible failure mechanisms. The conducted investigations demonstrated that low-cost wood waste-based composites can be used as an environmentally and economically attractive substitute for lightweight applications.
Open Access: Yes
DOI: 10.1002/pc.26155
Utilization of Waste Marble Dust in Poly(Lactic Acid)-Based Biocomposites: Mechanical, Thermal and Wear Properties
Publication Name: Journal of Polymers and the Environment
Publication Date: 2021-09-01
Volume: 29
Issue: 9
Page Range: 2952-2963
Description:
The aim of this present work was to study the applicability of waste marble dust (MD) in poly(lactic acid) (PLA)-based composites. Samples containing up to 20 wt% waste MD were prepared via melt blending. The attention was focused on the investigation of mechanical, morphological, thermal properties and the wear resistance of the PLA/MD composites. Regarding the mechanical properties, both the tensile and the flexural modulus improved remarkably, however, a slight loss was observed in strength and deformability. The impact toughness showed an increasing tendency up to 10 wt% MD loading, which was followed by a marginal decrease at higher concentration. With respect to the sliding wear rate, the composite with the highest MD content showed the best wear resistance. According to the DSC measurements, the MD hampered the chain mobility of PLA, thereby reducing the crystalline ratio. Overall, composites with improved properties were developed, while the reuse of waste MD is expected to reduce the production costs as well.
Open Access: Yes
Highly toughened blends of poly(lactic acid) (PLA) and natural rubber (NR) for FDM-based 3D printing applications: The effect of composition and infill pattern
Publication Name: Polymer Testing
Publication Date: 2021-07-01
Volume: 99
Issue: Unknown
Page Range: Unknown
Description:
In this study, the suitability of natural rubber (NR) toughened poly(lactic acid) (PLA)-based blends were investigated for additive manufacturing applications. Filaments for fused deposition modeling (FDM) were prepared with an NR concentration of 0 … 20 wt% using a twin-screw extruder. Subsequently, specimens were fabricated with a desktop 3D printer machine working on FDM principles. Besides the composition of PLA/NR blends, the effect of infill orientation was also analyzed by preparing two sets of specimens: i) one set prepared with an alternating raster angle of ±45° (3DGRID) and ii) another one with a linear infill parallel to the length of the specimens (3DPAR). Quasi-static and dynamic mechanical properties, morphology and thermal characteristics of the fabricated specimens were investigated. The tensile tests revealed that the presence of NR effectively enhances the ductility of PLA filaments, however, the achieved improvement was highly dependent on the applied infill pattern. Samples prepared using the 3DPAR infill exhibited an excellent deformability when paired with NR. On the other hand, the ones fabricated with the 3DGRID technique only showed a marginal improvement in elongation. Similarly, the Charpy impact tests indicated an outstanding impact resistance of NR-toughened 3DPAR specimens, while the 3DGRID types showed little to no improvement. Scanning electron microscopic analysis revealed a weaker interlayer adhesion in the specimens containing NR, which greatly contributed to the discrepancies observed between the mechanical properties of the samples prepared with different infill. The differential scanning calorimetry revealed an almost completely amorphous structure of 3D printed PLA due to the quite rapid cooling characteristic of the FDM technique, which was not affected by the embedded NR component.
Open Access: Yes
A novel preparation method of polypropylene/natural rubber blends with improved toughness
Publication Name: Polymer International
Publication Date: 2021-03-01
Volume: 70
Issue: 3
Page Range: 298-307
Description:
A novel melt compounding method – originally introduced for the preparation of nanocomposites – was adapted to produce polypropylene (PP) based blends toughened with up to 20 wt% natural rubber (NR). This water-assisted technique is based on batchwise melt mixing, where the additives are introduced as an aqueous dispersion into the matrix, drop by drop. The efficiency of this preparation technique was analyzed by comparing the resulting blends with reference samples produced by traditional melt mixing. Mechanical, thermomechanical and morphological properties were determined in order to investigate the structure–property relationships. According to SEM analyses, the average domain size of NR within the PP matrix became significantly smaller when the water-assisted method was applied. Charpy impact tests showed that the toughening efficiency of NR particles within the PP was enhanced as a result of their decreased size. This improvement was more prominent when the difference between the viscosity of PP and NR was higher. In addition, applying the water-assisted technique led to an enhanced deformability with similar strength and stiffness compared to common melt mixing. © 2020 The Author. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry.
Open Access: Yes
DOI: 10.1002/pi.6133
Antibacterial and anti-inflammatory activities of Cassia fistula fungal broth-capped silver nanoparticles
Publication Name: Materials Technology
Publication Date: 2021-01-01
Volume: 36
Issue: 14
Page Range: 883-893
Description:
The growing need for sustainable technologies has attracted considerable interest in the synthesis of ecofriendly materials. This paper reports the anti-inflammatory and antibacterial activities of sustainable silver nanoparticles (AgNPs) fabricated using endophytic fungus extracted from a medicinal plant, Cassia fistula. Fourier transform-infrared and UV-visible were used for AgNPs characterisation. X-ray diffraction, scanning electron microscope, energy dispersive X-ray analysis, atomic force microscope (AFM), transmission electron microscope and dynamic light scattering analysis revealed that the biosynthesised AgNPs were within the size of ~4–54 nm. The synthesised AgNPs displayed considerable antibacterial activity against Staphylococcus aureus, Escherichia coli and Klebsiella pneumonia bacterial strains. Additionally, synthesised AgNPs showed significant anti-inflammatory potential.
Open Access: Yes
Preparation and characterization of poly(lactic acid)/boehmite alumina composites for additive manufacturing
Publication Name: Iop Conference Series Materials Science and Engineering
Publication Date: 2020-08-25
Volume: 903
Issue: 1
Page Range: Unknown
Description:
The purpose of this work is to investigate the suitability of boehmite alumina (BA) reinforced poly(lactic acid) (PLA) for additive manufacturing with the fused filament fabrication method. PLA filaments with 0-10 wt.% BA content were produced via melt compounding using a twin-screw extruder. Dumbbell-shaped and prismatic specimens were manufactured then by feeding the prepared filaments into a desktop 3D printer. Mechanical, morphological and melt flow properties of the developed samples were determined. The addition of BA decreased the melt flow rate of PLA, however not so much that it would have hindered its suitability for 3D printing. With increasing BA content both the strength and the stiffness of the samples increased slightly at constant deformability and toughness. Scanning electron microscopic images revealed a homogenous dispersion of BA particles within the PLA matrix, although remaining agglomerates were also observed.
Open Access: Yes
Water-assisted production of polypropylene/boehmite composites
Publication Name: Periodica Polytechnica Mechanical Engineering
Publication Date: 2020-01-01
Volume: 64
Issue: 2
Page Range: 128-135
Description:
In this study polypropylene (PP) matrix-based boehmite alumina (BA) reinforced composites were prepared batchwise in an internal mixer. BA particles up to 10 wt.% were incorporated by 1. traditional melt mixing and 2. in a novel, Water-Assisted (WA) way, called fast evaporation mixing, during which BA was dispersed in PP with the use of an aqueous carrier medium. The WA way with pure water as medium proved to be ineffective because of the presence of the Leidenfrost effect. Therefore, an additional agent, carboxymethyl cellulose (CMC) was used to increase the boiling temperature of the water. Mechanical, morphological and thermal properties of the composites were determined. Scanning electron microscopy images revealed a partially dispersed structure of BA within the PP matrix in all cases, where aggregates and dispersed particles were identified as well. The size of the agglomerates observed was the smallest when BA was incorporated by being dispersed in water/CMC firstly. The mechanical tests results indicated that the reinforcing effect of BA was also most prominent in this case. However, CMC had an opposite effect on PP, than BA thus reducing the overall enhancement in mechanical properties. Differential scanning calorimetry showed an increase in the crystallinity ratio of PP with increasing BA content, which indicates a nucleating effect of BA.
Open Access: Yes
DOI: 10.3311/PPME.13981
Effect of Storage Time on the Structure and Mechanical Properties of Starch/Bentonite Nanocomposites
Publication Name: Starch Staerke
Publication Date: 2019-01-01
Volume: 71
Issue: 1-2
Page Range: Unknown
Description:
Thermoplastic starch (TPS), plasticized with glycerol and water, and its nanocomposites containing up to 7.5 parts per hundred resin (phr) pristine bentonite (BT) are prepared by melt compounding. Effects of the BT reinforcement and storage time on the morphology, water content, and mechanical properties of the related TPS nanocomposites are investigated on compression molded specimens. Morphology change is followed by wide-angle X-ray scattering (WAXS) measurements. The presence of BT increases the rate of transformation from A- to V-type crystalline form. It is also found that BT particles hinders the recrystallization (retrogradation) of TPS. BT becomes intercalated in TPS, which is supported by the water used as additional plasticizer for the compounding of maize starch. According to gravimetric measurements, TPS samples lose part of their water content during retrogradation/aging. Both the incorporation of BT and the time of aging result in increased strength and stiffness, however at the cost of elongation at break. This is associated with enhanced strength and stiffness, which is ascribed to a change (from more to less hydrated) in the interphase. According to scanning electron and atomic force microscopy analysis, the reinforcing BT particles are homogenously dispersed on nano and micron scale within the TPS matrix.
Open Access: Yes
