Lignocellulosic Filler Research Articles

Effects of MA-g-PP and lignocellulosic filler addition on several properties of poly(L-lactic acid)/polypropylene composites

ABSTRACTThe aim of this study was to investigate the effects of maleic anhydride-graft-polypropylene (MA-g-PP) as a compatibilizer and wood fiber as a lignocellulosic filler on technical properties of poly(l-lactic acid) (PLLA)/polypropylene composites. The obtained composites were characterized through mechanical tests, thermogravimetric analysis, differential scanning analyzer, and chemical analysis via Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM). The obtained results showed that the mechanical properties of the composites containing MA-g-PP were higher than those of the composites without MA-g-PP. SEM images revealed that the morphological properties of the composites including PP and PLLA were improved. The chemical interactions between PP and PLLA were demonstrated through FTIR results of composites with MA-g-PP.

Ionic liquid pretreatment of bagasse improves mechanical property of bagasse/polypropylene composites

For preparation of wood-plastic composites, pretreatment of lignocellulosic material is important to increase compatibility between matrix polymers and lignocellulosic fillers. In this study, choline acetate (ChOAc, a cholinium ionic liquid)–assisted pretreatment of bagasse powder could improve properties of chemically modified bagasse/polypropylene composites. The composites had fewer voids derived from vascular bundles of the bagasse tissue when using ChOAc-pretreated bagasse powder compared with the case when using untreated bagasse powder. The tensile strength of the composites was 20MPa, 35MPa, and 40MPa in the cases of polypropylene only, untreated bagasse powder, and ChOAc-pretreated bagasse powder, respectively. The elastic modulus was 0.7GPa, 2.0GPa, and 2.6GPa in the case of polypropylene only, the case using untreated bagasse powder, and the case using ChOAc-pretreated bagasse powder, respectively. Thus, ChOAc pretreatment of bagasse powder could enhance the blending and the tensile property of propionylated bagasse/polypropylene composites compared with those of the composites made using untreated bagasse powder.

Biodegradation properties of wood-plastic composites containing high content of lignocellulosic filler and zinc borate exposed to two different brown-rot fungi

The decay resistance of zinc borate-reinforced wood-plastic composites (WPCs) was studied against two types of brown-rot fungi (Rhodonia placenta and Coniophora puteana). The WPCs with 70% wood fibers (Pinus sylvestris L.) were reinforced with 1% and 2% zinc borate. The reinforced WPCs were exposed to a decay test according to the EN 113 (1996) standard. The composite samples were characterized by their weight losses and water absorption capacity (WAC) as well as by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential thermal analysis (DTA). The weight losses and WAC results showed that zinc borate improved the decay resistance of the WPCs to a certain degree against brown rot fungi. The FTIR and SEM results showed that the brown rot fungi attacked the WPCs. It was concluded that the use of 1-2% zinc borate provided resistance to fungal attack on WPCs to a certain degree.

Thermal and dynamic mechanical thermal analysis of lignocellulosic material-filled polyethylene bio-composites

Thermal and rheological properties of plant-based natural filler-reinforced polyethylene bio-composites applying various filler loadings as well as the impacts of the different compatibilizers were investigated by means of differential scanning calorimetry and dynamic mechanical thermal analysis (DMTA). As lignocellulosic materials, such as rice-husk flour and wood flour, are eco-friendly biomaterials and a thermoplastic polymer, for example, high-density polyethylene, has good physico-mechanical and thermal properties, therefore their bio-composites can combine and utilize these two advantages at the same time. The temperature of the α-relaxation (T α) slightly increased and melting temperatures (T m) of the matrix polymer in the case of the studied bio-composites did not shift significantly as the filler loading changed, because the rigid interphase hinders the motion of polymer segments resulting in the increase in T α and only weak interactions developed at the interface between the matrix polymer and the reinforcement in the case of non-compatibilized composites. However, compatibility between the reinforcement and the matrix polymer was enhanced by incorporating compatibilizers, which further improved stiffness. From the DMTA experiment, the reinforcements result in composite samples having higher storage modulus (E′) than the neat polymer sample, indicating that incorporating lignocellulosic filler increased their stiffness.

Influence of Filler Particle Size on Physical Properties and Biodegradation of Biocomposites Based on Low-Density Polyethylene and Lignocellulosic Fillers

This study examined biocomposites based on low-density polyethylene (LDPE) and lignocellulosic fillers [wood flour (WF) and oil flax straw (FS)] selecting four size fractions of each lignocellulosic material as fillers for the composites. The primary aim was to evaluate the influence of fraction size on the composites’ basic properties; to accomplish this, the composites’ mechanical properties, thermal oxidation, thermophysical characteristics, and water absorption capacity were examined. Then microphotographs of the samples were created and length-to-diameter (L/D) ratio of the fillers was calculated, finding that the L/D ratio increased with increasing particle size. The particle size influenced the oxidative degradation and water absorption processes in composites with oil flax but not in those with WF. Biodegradation tests performed on the recovered soil found that the loss of mass in composites based on LDPE and FS was higher than in the same composites with WF. Moreover, at the initial stage of composting, the biodegradation rate correlated with the size of filler particles (i.e., the larger the particles, the higher the degradation rate of the biocomposite).

Processing and Characterization of Environmentally Friendly Composites from Biobased Polyethylene and Natural Fillers from Thyme Herbs

The main aim of this research work is to assess the potential of a distillery waste from thyme as multifunctional filler in natural fiber reinforced plastics (NFRP) with biobased polyethylene matrix. Several ethylene-based copolymers with different co-monomers (vinyl alcohol, methyl methacrylate, glycidyl methacrylate and acrylic acid) were used as compatibilizer agents to overcome the lack of compatibility between the highly hydrophobic matrix and the highly hydrophilic lignocellulosic filler. The effect of the compatibilizer type and amount, as well as the lignocellulosic filler content was followed by thermal, mechanical, morphological and rheological characterizations. In addition to the typical filler effect, thyme also provides a remarkable increase in thermal stability at moderate temperatures with a positive effect on widening the processing window. The compatibilizer agent that offers best balanced properties is the glycidyl methacrylate copolymer with a noticeable increase in stiffness, flexural and tensile strength. Regarding processability, the viscosity increases with the filler content. This is highly important at low shear rates but the effect is almost negligible at high shear rates typical of injection molding processes.

Fire Retardation Mechanism of PVC Composite Filled with White Rice Husk Ash for Ceiling Board Applications

The rising concern towards environmental issue underscores the “greenproducts” based on natural resources for a wide range of applications. Theseefforts include white rice husk ash (WRHA) considering as an alternative rawmaterial for lignocellulosic filler in green composite. We present the propertiesevaluation of composite WRHA dispersing into polyvinyl-chloride (PVC) with di-isononyl-phthalate(DINP) as compatibilizing agent by compression molding method. The XRD analysisshows typical main peak of silica crystalline, the strengthening materials asreinforcement within the composite structure. The SEM demonstrated that WRHAfillers were well embedded in PVC matrix and better adhesion occurred between themand the matrix. Thus, the adhesion between the reinforcing fiber and the matrixplays an important role in the mechanical properties of the materials. The positiveachievement for fire resistance and its mechanism were specially discussed forceiling board in/outdoor environment applications.

Degradation studies and mechanical properties of treated curauá fibers and microcrystalline cellulose in composites with polyamide 6

The use of lignocellulosic fibers derived from renewable resources as a reinforcing phase in polymeric matrix composites provides positive environmental benefits with respect to ultimate disposability and raw material use. Despite the attractive properties, lignocellulosic fillers are used only to a limited extent in industrial practice due to the restriction to 200℃ in composites processing temperatures. Lignocellulosic materials start to degrade near 230℃. This limits the type of thermoplastics that can be used in association with polysaccharide fillers. To overcome these disadvantages, chemical treatments, i.e. alkaline treatment, were applied to curauá fibers to improve the thermal properties. Colorimetry was employed to evaluate the extension of darkening of composites prepared with treated curaua and Avicel. Fourier-transform infrared spectra of polyamide composites with treated curaua showed no differences when compared to pure polyamide. Moreover, no changes in molar mass were observed in microcrystalline cellulose processed in different temperatures.

The effect of lignocellulosic filler types and concentrations on the mechanical properties of wood plastic composites produced with polypropylene having various melt flowing index (MFI)

The effect of lignocellulosic filler types and concentrations on the mechanical properties of wood plastic composites produced with polypropylene having various melt flowing index (MFI)

Comparison on mechanical properties of lignocellulosic flour epoxy composites prepared by using coconut shell, rice husk and teakwood as fillers

The objective of this work was to investigate the feasibility of using lignocellulosic fillers (coconut shell, rice husk and teakwood) as alternative reinforcement for expensive non-renewable fillers used in conventional composites. Various concentrations of epoxy based bio-fillers composites were prepared and the influences of filler size (75–105 and 106–180 μm) and mass concentration (2.5 and 4.5 wt%) on the mechanical properties were investigated. Properties such as deformability, stiffness, elasticity and strain energy absorption ability of each material combination were determined using single indentation load control, single indentation displacement control and multi-cyclic indentation tests. The results showed that parameters such as filler size, volume content, filler type (chemical composition and shape) dispersion influenced these properties. It was revealed that high lignin content increased the stiffness whereas high cellulose content with high impregnation ability favoured deformability. High cellulose content and surface roughness supported better adhesion due to a large number of hydrogen bonds and high mechanical interlocking, respectively.

Bio-based composites from agricultural wastes: Polylactic acid and bamboo Guadua angustifolia

Biopolymers as polylactic acid (PLA) have some drawbacks in processing and the final product is characterized by a high permeability to steam/gases and low thermal and mechanical resistance. The addition of reinforcement materials in the biopolymer matrix provides opportunities to minimize these disadvantages. Thus, this research focuses on the inclusion of non-wooden lignocellulosic fillers from bamboo Guadua angustifolia in a polymer matrix obtained from PLA. Three types of fillers were applied: sawdust, fiber from a Kraft process, and fiber with low lignin content. The blends of PLA reinforced with 5% organic fillers were performed on a torque rheometer at temperatures between 170 to 200℃ with the addition of glycerol as plasticizer and viscosity reducer of the system and maleic anhydride as compatibilizer. The evaluation on rheological, thermal, mechanical and morphological properties were investigated by rotational rheometry, differential scanning calorimetry (DSC), universal testing machine, wide angle X-ray diffraction (WAXD) and scanning electron microscopy (SEM). The results showed that the inclusion of the lignocellulosic material generated a positive response in obtaining polymeric biocomposite. The use of fibers subjected to a process of delignification with bleaching sequences OQPoPWa resulted in a greater influence on the mechanical strength, an adequate distribution of the fibers in the PLA matrix and the viscosity of the mixture.

Eco-Friendly Constituents for Making Wood-Polymer Composites

The aim of this work was to obtain eco-friendly constituents for making wood-polymer composites (WPCs) by rational utilisation of hardwood residue with its mechanical processing and purposeful chemical modification. To reduce the energy input for residue milling for obtaining a lignocellulosic filler as well as to activate its surface for the further modification, the optimal parameters of low temperature acid hydrolysis of the hardwood residue under mild conditions were found. To enhance the wetting of the lignocellulosic filler with respect to recycled polypropylene, the milled hydrolysed wood particles were modified by ammoxidation. For obtaining a lignin-containing surface tension regulator (compatibiliser) that is able to reinforce the interaction between the constituents at the interface, soda lignin was obtained via delignification of the hydrolysed hardwood residue under laboratory conditions. The developed compatibiliser represented nanoparticles of a non-stoichiometric polyelectrolyte complex, incorporating soda lignin and synthetic polyamine - polyethylenimine. By using appropriate laboratory equipment and the determined technological regime, aspen wood-recycled polypropylene composites were made and tested.

Composite materials based on low-density polyethylene loaded with date pits

This work is devoted to investigate the available agricultural Tunisian waste: the date pits as reinforcing filler for thermoplastic matrix. The chemical composition of this reinforcing filler is found to be comparable to nonwood plants: its content comprises of 13% of extractibles, 22% of lignin, and 61% of holocellulose. Then, the lignocellulosic filler was used to prepare different composites films using Brabender mixing device. A series of composite film was established by different loadings of the date pits waste with 10–50% of the filler in 10% as an interval. The ensuing composites materials were then characterized by several techniques such as the morphology of the composites, which was investigated using scanning electron microscopy. The thermal properties of prepared materials were studied using differential scanning calorimetry and thermogravimetric analysis. Finally, the mechanical and water absorption properties were involved. The obtained results indicated that date pits–based particles enhanced the thermomechanical properties of the thermoplastic matrix and demonstrated that this available lignocellulosic biomass can be considered to be a promising filler material.

Processing and characterization of high environmental efficiency composites based on PLA and hazelnut shell flour (HSF) with biobased plasticizers derived from epoxidized linseed oil (ELO)

Different amounts of epoxidized linseed oil (ELO) have been added to poly(lactic acid)-PLA composites with hazelnut shell flour (HSF) to provide a plasticizing effect and improve the low intrinsic ductile properties of PLA/HSF composites. Mechanical, thermal, thermo-mechanical and dynamic mechanical properties have been studied in terms of the weight percentage ELO. Mechanical resistant properties in both tensile and flexural tests decrease with wt.% ELO while a remarkable increase with wt.% ELO is obtained. These results reveal a clear plasticization effect of ELO but, in addition, internal structure of PLA/HSF/ELO composites shows good PLA-HSF (matrix-particle) interactions so that indicating that ELO also provides a coupling effect between PLA matrix and HSF filler. ELO addition leads to a decrease in storage modulus (G′) obtained by dynamic mechanical thermal analysis (DMTA) in torsion mode thus giving clear evidence of the plasticization effect of ELO. Overall, the use of ELO in PLA/HSF composites is an attracting way to improve the low intrinsic fragility of these green composites; furthermore, ELO provides an improvement on thermal stability and a coupling effect between the polymer matrix and the surrounding lignocellulosic filler.

English

This work deals with the design, preparation and characterization of composites based on Poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyvalerate] and lignocellulosic filler suitable for the production of compostable and biodegradable biocomposites that mimic the thermo-mechanical and processing characteristics commonly found in those polymeric materials specially designed for injection molding and blow extrusion. The best formulation in terms of processability, thermo-mechanical properties and biodegradation behavior under mature compost conditions was the biocomposite that contained 42.8 % by wt. of Poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyvalerate] as the major component, 5 % by wt. of lignocellulosic filler, 10 % by wt. of tributyl citrate plasticizer, 30 % by wt. of Poly(butylene adipate-co-terephthalate), 10 % by wt. of Poly(vinyl acetate), 0.2 % by wt. of Joncryl ADR-4368C a chain extender, 1 % by wt. of a primary antioxidant mix, and 1 % by wt. of nucleating agents.

The thermo-oxidative stability and flammability of wood/polypropylene composites

The main aim of the study was to evaluate the thermo-oxidative stability and flammability of wood/polypropylene composites. The composites were obtained by extrusion and compression moulding with chemical modification of wood in order to improve adhesion. The composites were characterised by differential scanning calorimetry and cone calorimetry, providing such parameters as the oxidation induction time and a few parameters describing flammability, e.g. time to ignition, heat release rate, mass loss rate, heat of combustion, specific extinction area and emission of toxic gases. The results illustrate a considerable effect of the presence of wood and chemical modifications of lignocellulosic filler on the thermo-oxidative stability and character of combustion of the composites studied. The information provided in the paper contributes towards the correct choice of chemical modification of wood that would improve mechanical properties of the composites and towards getting composite materials of target thermo-oxidative stability and flammability.

Olive stones flour as reinforcement in polypropylene composites: A step forward in the valorization of the solid waste from the olive oil industry

The usefulness of olive stone flour (OSF) from the solid residue of the olive oil extraction as a reinforcement for the preparation of a cost-effective polypropylene-based composite was investigated. The lignocellulosic filler consisted of acicular particles with a broad size distribution ranging from about 50 to 400μm, and is composed of lignin, hemicelluloses, and cellulose. Composites with filler loading up to 70wt% were prepared using a melt processing and injection molding. The evolution of the mechanical performance, impact properties, and water absorbance of the composites as a function of the filler content were investigated. The addition of a maleated polypropylene (MAPP) coupling agent at a level of 5%, with respect to the filler, was shown to be essential in bringing about a reinforcing effect. A steady increase in the modulus along with a preservation in the tensile strength was observed up to a content of 60% OSF. The obtained results have confirmed the viability of OSF as cheap reinforcing filler for the PP matrix; thus, opening new perspectives for the use of this agricultural by-product.

Preparation, structure, and properties of biocomposites based on low‐density polyethylene and lignocellulosic fillers

This article examines compositions based on low density polyethylene containing various lignocellulosic fillers–flax shive, sunflower husk, hay, birch leaves, lignosulfonate, and banana skin. The ethylene‐vinyl acetate copolymer is used as a compatibilizing component. The article is aimed at identifying the main factors determining biodegradation rate of the compositions. Thermal resistance and morphology of the fillers, mechanical and structural characteristics of the compositions, and their stability in aqueous media and ground soil were studied. The influence of the filler particle shape on the resistance of the compositions against various effects was shown. It was found that an increase in the length‐to‐diameter (L/D) ratio of the filler particles increases strength and water absorption, reduces melting viscosity, and accelerates biodegradation in soil. POLYM. COMPOS., 37:1461–1472, 2016. © 2014 Society of Plastics Engineers

Polypropylene composites based on lignocellulosic fillers: How the filler morphology affects the composite properties

In this research, composite materials were made from wood flour (WF) or olive stone flour (OSF) as reinforcement, polypropylene (PP) as polymer matrix, and maleated polypropylene (MAPP) as coupling agent, by using injection molding. The effects of the filler loading and coupling agent on the physical properties of the composites, in terms of tensile and impact strength, water absorption and wear resistance were studied. The macromechanical properties were explained by the morphological features of the reinforcements. Composites containing coupling agents exhibited the best mechanical properties, and reduced the negative impacts of water absorption. The difference in the morphology of the two lignocellulosic fillers was found to be a key factor controlling the properties of the composites and the evolution of their properties against water absorption.

Heat treated wood–nylon 6 composites

Heat treatment is a relatively benign modification method that is growing as an industrial process to improve hygroscopicity, dimensional stability and biological resistance of lignocellulosic fillers. There also has been increased interest in the use of lignocellulosic fillers in numerous automotive applications. This study investigated the influence of untreated and heat treated wood fillers on the mechanical and rheological properties of wood filled nylon 6 composites for possible under-the-hood applications in the automobile industry where conditions are too severe for commodity plastics to withstand. In this study, exposure of wood to high temperatures (212°C for 8h) improved the thermal stability and crystallinity of wood. Heat treated pine and maple filled nylon 6 composites (at 20wt.% loading) had higher tensile strengths among all formulations and increased tensile strength by 109% and 106% compared to neat nylon 6, respectively. Flexural modulus of elasticity (FMOE) of the neat nylon 6 was 2.34GPa. The FMOE increased by 101% and 82% with the addition of 30wt.% heat treated pine and 20wt.% heat treated maple, where it reached maximum values of 4.71GPa and 4.27GPa, respectively. The rheological properties of the composites correlated with the crystallinity of wood fillers after the heat treatment. Wood fillers with high crystallinity after heat treatment contributed to a higher storage modulus, complex viscosity and steady shear viscosity and low loss factor in the composites. This result suggests that heat treatment substantially affects the mechanical and rheological properties of wood filled nylon 6 composites. The mechanical properties and thermogravimetric analysis indicated that the heat treated wood did not show significant thermal degradation under 250°C, suggesting that the wood-filled nylon composites could be especially relevant in thermally challenging areas such as the manufacture of under-the-hood automobile components.