Morphology and mechanical properties of reconstituted wood board waste-polyethylene composites

In this work, organoclay reinforced high density polyethylene (HDPE) nanocomposites were prepared at laboratory scale using a batch mixer. Processing conditions, maleic anhydride modified polyethylene (MAPE) type and MAPE/clay weight ratio were optimised. The microstructure of the resultant nanocomposites was analysed by X-ray diffraction and melt rheology tests, and flexural properties and thermal stability were evaluated. Three types of MAPEs with different melt flow indices (MFI) and maleic anhydride contents all improved the interaction between HDPE and clay and promoted clay dispersion. Nanocomposites where the MAPE with MFI most similar to HDPE was used showed the best exfoliation of clay and the strongest HDPE/clay interface. Mechanical properties were slightly improved, while thermal stability was distinctly enhanced in these HDPE nanocomposites compared with neat HDPE and HDPE nanocomposite without MAPE. The prepared HDPE nanocomposites show the potential to improve the thermal stability of wood–plastic composites for structural applications.

Biocomposites based on poly(hydroxybutyrate) and the mesocarp of babassu coconut (Orbignya phalerata Mart.): effect of wax removal and maleic anhydride-modified polyethylene addition

Polyethylene (PE) nanocomposite samples were prepared with Cloisite 25 A, 30B, and 93 A and Nanofil 5 and 3000 nanofillers. The amount of modified Na+ montmorillonite (MMT Na+) was fixed to 5 wt%. For the compounding of PE matrix and nanofillers, two different compounding equipments were used, KO Kneader Buss and APV twin-screw extruder. In all samples, maleic anhydride-modified PE (PEMa) was added as a compatibilizer. The content of PEMa in mixtures was always 5 wt%. The level of MMT exfoliation in the nanocomposite systems was studied by X-ray diffraction and by transmission electron microscopy observations. The properties of samples were evaluated by dynamical mechanical analysis ( E* modulus at 30°C) and by the measurement of tensile properties (stress and strain at break). Because of the possibility of usage of prepared materials in packaging industry, barrier properties were measured with focus on oxygen, carbon dioxide, and water vapor permeability. The influence of two different used compounding equipments on the prepared nanocomposite samples of PE nanocomposites was discussed.

In this study, flexural properties, impact strength, thermal performance, water absorption, biological durability, and morphology of wood-plastic composites (WPCs) filled with different filler types were investigated. Six different formulations of WPCs were fabricated from mixtures of carpenter waste and recycled high-density polyethylene (R-HDPE). The carpenter waste was derived from wood and particle board wastes, and R-HDPE was used as the polymer matrix, with and without addition of maleic anhydrite grafted polyethylene (MAPE). All formulations were compression moulded in a hot press for 3 min at 170 °C. Investigations on the compression moulded specimens revealed that water absorption values in the particleboard waste flour specimens were lower than in the wood-waste flour WPCs. However, the wood-waste flour-filled composites exhibited higher mechanical property values than the particleboard waste flour WPCs. Statistically, only the wood-waste flour-filled composites with MAPE were significantly different. The use of MAPE (3 wt%) had a positive effect on the water absorption, crystallinity degree, and flexural properties of the WPCs. In addition, the peak temperatures of the composites did not show any variation, while thermal decomposition of the composites showed minor variations under the thermogravimetric analysis. Furthermore, the decay resistance of the composites improved with the use of particleboard waste flour. The obtained results demonstrate that particleboard waste flour, such as wood-waste flour, is potentially suitable as a raw material in WPCs.

The study of fibre/matrix bond strength in short hemp polypropylene composites from dynamic mechanical analysis

The solid state self-healing system was obtained by employing a thermosetting epoxy resin, into which a thermoplastic is dissolved. The aim of this study is to investigate the homogeneous and heterogeneous solid state self-healing system by using thermoplastics comprised of poly(bisphenol-A-co-epichlorohydrin) (PDGEBA), polyvinyl chloride (PVC), polyvinyl alcohol (PVA), polyethylene (PE) and polypropylene (PP) as healing agents. PDGEBA produced homogenous resin blend which undergone random molecule diffusion healing process. A heterogeneous resin blend composed of 8 wt.% PVC, PVA PE, and PP, yielding a “bricks and mortar” morphology wherein the epoxy phase exists as a matrix (mortar) interpenetrated with a percolating thermoplastic (bricks). The healing process in heterogeneous resin blend is attributed to volumetric thermal expansion of healing agent above its melting point in excess of epoxy brick expansion. Healing was achieved by heating the fractured resins to a specific temperature; above their glass transition temperature ( Tg) which obtained from dynamic mechanical analysis (DMA) in order for diffusion process and thermal expansion to occur. The thermal properties and bonding formed in the epoxy resins were characterized by means of Fourier Transform Infrared Spectroscopy (FTIR) and dynamic mechanical thermal analysis (DMTA). Izod impact test and compact tension test were conducted to demonstrate details self-healing capability of different specimens. Results of Izod impact test are in agreement with the result of compact tension test. Under compact tension test, the healable resin with PDGEBA has the highest healing efficiency of 60% followed by PVC, PP, PE, and PVA with 39%, 37%, 28% and 21% of average percentage healing efficiencies in three healing cycle respectively. Morphological studies using optical microscope verified the fracture-healing process and morphological properties of the resins.

Tensile impact strength of blends of high-density polyethylene (HDPE) and acrylonitrile-butadiene-rubber (NBR) has been studied with special reference to the effect of blend ratio and com-patibilizer concentration. Even though the tensile impact strength of the blend is inferior to that of virgin plastic, a substantial improvement was observed in the tensile impact strength values of the compatibilized systems. The compatibilizers, phenolic modified polyethylene (PhPE) and maleic anhydride modified polyethylene (MAPE), act by locating at the interface due to their propensity to phase separation. By the addition of compatibilizers the interfacial tension is reduced and better mixing between components becomes possible, which results in finer and uniform morphology. The compatibilizers also improve the interfacial adhesion. The improvement in tensile impact strength has been explained on the basis of the blend morphology, that is, size, shape, and distribution of the rubber phase in the plastic matrix; tensile properties; and interfacial adhesion between the phases.

The purpose of this study was to investigate the characteristics of lignin fractionated from waste wood (WW) using a two-step process of ethanol organosolv pretreatment followed by ultrafiltration with membranes of different molecular weight cut-offs (1, 5 and 20 kDa). The different permeates obtained were characterized by fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA) and gel permeation chromatography (GPC). The analysis by FT-IR and NMR of these lignins showed that the lignin core was successfully separated from WW. TGA curves confirmed that the thermal properties of lignin fractionated by ultrafiltration were almost identical to each other. The results from GPC confirmed that fractionating of lignin was achieved by ultrafiltration. For the membrane fractionation process, values of molecular weight decreased as the cut-offs used to obtain the fractions became smaller. As a result, fractionating lignin by a two-step process allowed separating different fractions of lignin of different molecular weights yielded high purity without interference from existing pollutants in WW. The two-step process offers the possibility of using fractionated WW as an untapped source of lignin.

In this study, Wood Plastic Composites (WPCs) were produced from post-consumer bulky wastes of recycled plastic and wood in order to minimize waste, decrease environmental effects of plastics, reserve natural resources, and support circular economy for sustainable production and consumption. Five different types of polypropylene (PP) or polyethylene (PE) based recycled plastics and wood obtained from urban household bulky wastes were used in the production of recycled WPC composites, r-WPCs. Virgin WPC (v-WPC) and r-WPC compounds were prepared with wood flour (WF) and maleic anhydride grafted compatibilizer (MAPP or MAPE) to evaluate the effect of recycled polymer type and compatibilizer on the mechanical properties. It was found that tensile strength properties of r-WPCs produced from recycled PP (r-PP) were higher than that of the r-WPCs produced from mixed polyolefins and recycled PE. r-WPCs containing anti-oxidants, UV stabilizers, and compatibilizer with different WF compositions were produced from only recycled garden fraction PP (PPFGF) to determine the optimum composition and processing temperature for pilot scale manufacturing of r-WPCs. Based on tensile, impact, flexural, and water sorption properties of r-WPC compounds with different formulations, the optimum conditions of r-WPC compounds for industrial manufacturing process were determined. Surface morphology of fractured surfaces as well as tensile, flexural and density results of r-WPC compounds revealed the enhancement effect of MAPP on interfacial adhesion in r-WPCs. r-WPC products (crates and table/chair legs) based on bulky wastes were produced using an injection molding process at industrial scale by using 30 wt% WF-filled r-WPC compound. This study demonstrated that r-WPC compounds from recycled bulky plastic and wood wastes can be used as a potential raw material in plastic as well as WPC industry, contributing to circular economy.Graphic

Properties and structure of poly(3-hydroxybutyrate-co-4-hydroxybutyrate)/wood fiber biodegradable composites modified with maleic anhydride

Long glass fiber-reinforced polyamide 6 (LGF–PA6) composites were prepared by using self-designed impregnation device. Polypropylene grafted with maleic anhydride (PP-g-MAH) and polyolefin elastomer grafted with maleic anhydride (POE-g-MAH) were chosen as compatibilizers. Dynamic mechanical properties of LGF–PA6 composites were investigated by using dynamic mechanical analysis (DMA). The DMA measurement results showed that test frequency, long glass fiber content and compatibilizers had an influence on dynamic mechanical properties and glass transition temperature (Tg) of LGF–PA6 composites. The frequency had a complex influence on storage modulus (E′), loss modulus (E″) and loss tangent (tan δ). The Tg of the composites is shifted to high temperature with the increasing of test frequency and was affected insignificantly by the glass fiber content. Storage modulus and loss modulus (E″) increased with the increasing fiber content, while the tan δ decreased. The effect of the addition of PP-g-MAH and POE-g-MAH on the dynamic mechanical properties of LGF–PA6 composites was complex. Scanning electron microscopy (SEM) was used to investigate the morphology of the fractured composites surface. The SEM results suggested that the PP-g-MAH and POE-g-MAH both improved the fiber/matrix interface adhesion, which was consistent with the DMA measurement results.

Rice husk and nanoclay (montmorillonite)-filled low-density polyethylene composite films were prepared by extrusion blown film. Maleic anhydride-modified polyethylene was used as compatibiliser in various concentrations ranging from 0 to 8 parts per hundred. X-ray difractograms showed an increase in interlayer spacing of montmorillonite from the use of compatibiliser when compared to the uncompatibilised composites; an increase of 20, 33, 36 and 38% for 2, 4, 6 and 8 parts per hundred, respectively, of maleic anhydride-modified polyethylene. With the incorporation of maleic anhydride-modified polyethylene, a better dispersion of the fillers was also achieved, as confirmed by scanning electron microscopy. The compatibilised composite films showed improved tensile and barrier properties. The addition of 4 parts per hundred of the compatibiliser resulted in an improvement by 22% in tensile strength. Furthermore, oxygen barrier property of the composite films improved more than twofold by adding 4 parts per hundred of maleic anhydride-modified polyethylene. This improvement in tensile and barrier properties is due to an increase in the interfacial adhesion between the fibre and matrix and better dispersion of impermeable nanoparticles.

In the pursuit of sustainability and reduced dependence on new plastic materials, this study explores the upcycling potential of high-density polyethylene (HDPE) milk bottles into high-stiffness, high-heat-distortion-temperature (HDT) composites. Recycled high-density polyethylene (rHDPE) sourced from used milk bottles serves as the composite matrix, while reinforcing fillers are derived from dried pineapple leaves, comprising fibers (PALF) and non-fibrous materials (NFM). A two-roll mixer is employed to prepare rHDPE/NFM and rHDPE/PALF mixtures, facilitating filler alignment in the resulting prepreg. The prepreg is subsequently stacked and pressed into composite sheets. The introduction of PALF as a reinforcing filler significantly enhances the flexural strength and modulus of the rHDPE composite. A 20 wt.% PALF content yields a remarkable 162% increase in flexural strength and a 204% increase in modulus compared to neat rHDPE. The rHDPE/NFM composite also shows improved mechanical properties, albeit to a lesser degree than fiber reinforcement. Both composites exhibit a slight reduction in impact resistance. Notably, the addition of NFM or PALF substantially elevates HDT, raising the HDT values of the composites to approximately 84 °C and 108 °C, respectively, in contrast to the 71 °C HDT of neat rHDPE. Furthermore, the overall properties of both the composites are further enhanced by improving their compatibility through maleic anhydride-modified polyethylene (MAPE) use. Impact fracture surfaces of both composites reveal higher compatibility and clear alignment of NFM and PALF fillers, underscoring the enhanced performance and environmental friendliness of composites produced from recycled plastics reinforced with pineapple leaf waste fillers.

A novel elastomer-modified multicomponent, multiphase waste-sourced biocomposites, was prepared for converting waste biomass and plastic into value-added products. The effects of blending elastomer–olefin block copolymer (OBC) and maleic anhydride (MAH), and divinylbenzene (DVB) co-grafting of recycled polypropylene (rPP) matrix on the adhesion interface, structure, and properties of high wood flour-filled (60 wt.%) composites were thoroughly investigated. The results indicated that DVB introduced branched structures into the polymer matrix molecular chain and increased the MAH grafting rate. Co-grafting rPP/OBC blends enhanced the interfacial adhesion among rPP, OBC, and wood flour. Additionally, MAH-grafted OBC was prone to encapsulating rigid wood flour, thereby forming an embedded structure. Notably, the tensile modulus and impact strength of the final three-component composites increased by 60% and 125%, respectively, compared with the unmodified composites. Additionally, dynamic mechanical analysis revealed that DVB-induced branching promoted the formation of microvoids in the OBC shell layer surrounding the wood, which in turn induced significant plastic deformation in the polymer matrix. This work offers a facile and efficient method for preparing high-toughness, high-stiffness, and low-cost waste PP-based composites for automotive interiors, and indoor and outdoor decoration.

The sorption kinetics and isothermal sorption of polybrominated diphenyl ethers (PBDEs) by virgin and aged polyethylene (PE) and polystyrene (PS) microplastics with irradiation by ultraviolet light were studied, with 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) as a representative compound. The influence of different environmental factors, including salinity and dissolved organic matter, on its sorption were analyzed. The virgin and aged microplastics were characterized by scanning electron microscopy, x-ray diffraction, and total reflection infrared spectroscopy. The different models of kinetics and sorption isotherm were used to fit the data, and the sorption mechanism of PBDEs by microplastics was analyzed. The results showed that the main sorption modes of virgin and aged PE were surface sorption and external liquid film diffusion. The virgin and aged PS presented the surface sorption. The sorption isotherm was consistent with the Freudlich model, indicating that the sorption of BDE-47 by microplastics was characterized by a multi-phase, multi-layer, and non-uniform sorption process. The equilibrium sorption capacities of BDE-47 on virgin PE, aged PE, virgin PS, and aged PS were 3.72, 3.76, 6.04, and 3.46 ng·g-1, respectively. There was no obvious difference in equilibrium sorption capacity between the aged and virgin PE. However, the equilibrium sorption capacity for the aged PS was decreased by 42.38% compared with that of the virgin PS. The partition of the outer liquid membrane diffusion was the main mechanism affecting sorption of PBDEs by PE. Compared with the virgin PS, the increase in crystallinity and surface oxygen-containing functional groups led to a decrease in the equilibrium sorption capacity of PBDEs on the aged PS. The sorption of BDE-47 was not significantly influenced by salinity. However, dissolved organic matter exerted a negative effect on the sorption of BDE-47.