Wood Fiber/plastic Composites Research Articles

Evaluation of the Mechanical, Thermal and Rheological Properties of Hop, Hemp and Wood Fiber Plastic Composites.

The aim of this study was to evaluate the use of waste natural fibers from milled hop bines and hemp stalks, without chemical treatment, and compare them to a commercial wood fiber for use in wood-plastic composite (WPC) materials. The fibers were characterized (density, fiber size and chemical composition). WPCs were produced by the extrusion of a blend of fibers (50%), high-density polyethylene (HDPE) and coupling agent (2%). The WPCs were characterized for their mechanical, rheological, thermal, viscoelastic and water resistance properties. Pine fiber was about half the size of hemp and hop fibers and thus had a higher surface area. The pine WPC melts had a higher viscosity than the other two WPCs. Additionally, the tensile and flexural strengths of the pine WPC were higher than those of hop and hemp WPCs. The pine WPC was also shown to have the least water absorption followed by hop and hemp WPCs. This study highlights that different lignocellulosic fibers influence their WPC properties. The properties of the hop- and hemp-based WPCs were comparable to commercial WPCs and can be improved by further milling/screening the fibers to a smaller particle size (volumetric mean of ~88 μm) to increase their surface area, fiber-matrix interactions and improve stress-transfer.

Density reduction behaviors and cell morphology in extrusion of LLDPE/wood fiber composites with physical and chemical blowing agents

ABSTRACTFoamed wood fiber/plastic composites (WPC) with a fine‐cell structure offer many benefits compared with the unfoamed WPC, such as the reduced material cost and density, the improved toughness, and the enhanced processability. However, it is extremely challenging to achieve the desired density reduction and obtain a fine‐cell structure simultaneously. One of the obstacles is that the volatiles released from the wood fiber (WF) during processing should be suppressed to ensure a fine‐cell structure. Linear low‐density polyethylene (LLDPE) has a relatively low melting temperature, and it can reduce the processing temperature and suppress volatiles when used as a polymer matrix for foamed WPC. This paper systematically investigates the foamability of LLDPE/WF composites in a continuous foam extrusion, with both a chemical blowing agent and a physical blowing agent (PBA). It turns out that the PBA‐based foaming led to a smaller cell size and a narrower cell size distribution. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48829.

Morpho-mechanical properties of wood fiber plastic composite (WFPC) based on three different recycled plastic codes

ABSTRACTThis study set out to explore the effect of different recycled plastic codes and plastic content on the mechanical and morphological properties of wood fiber plastic composites (WFPC). The combination of polypropylene (PP), high-density polyethylene (HDPE), low-density polyethylene (LDPE) and Acacia fibers was labeled as PP-WF, HDPE-WF and LDPE-WF with different plastic content at 100%, 90%, 80%, 70%, 60%, and 50%. Mechanical properties include tensile strength (TS), modulus of elasticity (MOE) and modulus of rupture (MOR). While morphological property tests were performed using scanning electron microscope (SEM). The result showed that the TS of PP-WF, HDPE-WF, and LDPE-WF was decreased by 68.5%, 68.6%, and 82%, respectively, with a 50% decrease in plastic content. Meanwhile, the MOE of PP-WF, HDPE-WF, and LDPE-WF was decreased by 48.9%, 58.37% and 56.32%, respectively. The MOR of PP-WF, HDPE-WF, and LDPE-WF was decreased by 77.8%, 84% and 77%, respectively. Generally, the trend result of TS, MOE, and MOR decreased as the plastic content decreased. The highest TS, MOE, and MOR were achieved by PP-WF compared to HDPE-WF and LDPE-WF at every combination. SEM results revealed the presence of voids and many pulled-out of wood fibers as the plastic content decreased.

Review: Numerical Simulation in Wood Plastic Composite Extrusion

This paper first introduces the latest application of numerical modeling method in polymer processing, and then discusses the related research problems and the main open issues. Finally, requirements and prospects are proposed for the realization of the development direction of Wood–fiber/Plastic Composites (WPCs).

Effects of wood fiber content on the rheological properties, crystallization behavior, and cell morphology of extruded wood fiber/HDPE composites foams

When increasing the wood fiber (WF) content in extruded wood fiber/plastic composites (WPC) foams, a good balance between reducing the cost and obtaining good cell morphology should be maintained. This study examines the relationship between WF content and the foam morphology in WPC foams. The role of WF as cell nucleating agent at low concentrations (10 wt.%) was observed, as WPC foam with 10 wt.% WF had lower average cell size and higher cell density than neat HDPE foams. Increasing the WF content further, decreased the average cell size and cell density, and increased the foam density of WPC foams. These results were linked to the rheological properties and crystallization behavior of HDPE and WPC with different WF content.

The effects of clay dispersion on the mechanical, physical, and flame‐retarding properties of wood fiber/polyethylene/clay nanocomposites

AbstractIn this study, nanosized clay particles were introduced into wood fiber/plastic composites (WPCs) to improve their mechanical properties and flame retardancy, which are especially important in various automotive and construction applications. A high degree of exfoliation for nanoclay in the wood fiber/high density polyethylene (HDPE) composites was successfully achieved with the aid of maleated HDPE (PE‐g‐MAn), through a melt blending masterbatch process. The structures and morphologies of the composites were determined using X‐ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. This article presents the effects of clay content and degree of clay dispersion on the mechanical and physical properties and flame retardancy of wood fiber/HDPE composites that contained a small amount of clay, in the range of 3–5 wt %. We concluded that achieving a higher degree of dispersion for the nanosized clay particles is critical to enhance the mechanical properties and the flame retardancy of WPCs when small amounts of clay are used. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Characteristics of wood–fiber plastic composites made of recycled materials

This study investigates the feasibility of using recycled high density polyethylene (rHDPE), polypropylene (rPP) and old newspaper (rONP) fiber to manufacture experimental composite panels. The panels were made through air-forming and hot press. The effects of the fiber and coupling agent concentration on tensile, flexural, internal bond properties and water absorption and thickness swelling of wood-fiber plastic composites were studied. The use of maleated polypropylene as coupling agent improved the compatibility between the fiber and both plastic matrices and mechanical properties of the resultant composites compared well with those of non-coupled ones. Based on the findings in this work, it appears that recycled materials can be used to manufacture value-added panels without having any significant adverse influence on board properties. It was also found that composites with rHDPE provided moderately superior properties, compared with rPP samples.

Influence of wood fiber size on extrusion foaming of wood fiber/HDPE composites

AbstractFoaming of wood fiber/plastic composites (WPC) with a fine‐celled structure can offer benefits such as improved ductility and impact strength, lowered material cost, and lowered weight, which can enhance their utility in many applications. Although a great deal of attention is now being focused on these composites in the scientific literature, there are still numerous aspects of WPC processing that need elucidation. In this context, this article investigates the effects of wood fiber (WF) size on fine‐celled extrusion foaming of WPC in terms of cell size, cell size distribution, and foam density. The effects of WF size and coupling agent content on the viscosity of WPC are also investigated. The experimental results revealed that the small‐sized WF provides a better cell morphology, a smaller cell size, and a better cell uniformity in WPC foams. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Surface deterioration of wood-flour polypropylene composites by weathering trials

The market for wood-fiber plastic composites (WPCs) is expanding rapidly in many countries including Japan, where WPCs are mainly used for exterior products. In such applications, WPCs undergo undesirable color change, chalking, and shrinkage and swelling, and accordingly there is a need to better understand the mechanisms responsible for the weathering of WPC and develop methods of improving their weathering resistance. In this study, weatherability of WPC was assessed by natural and accelerated weathering trials. Discoloration (whitening) of WPC during exposure was caused by degradation of both wood and plastic. Darker color pigments as additives improved the color stability of WPC; however, chalking on the surfaces still occurred. The color stability of WPC was improved by application of exterior coatings. Preweathering of WPC (before coatings were applied) increased the absorption of coatings by the WPC and had a positive effect on the color stability and prevented chalking of the composites.

Flame retarding effects of nanoclay on wood–fiber composites

AbstractThis research article focuses on investigating the effects of nanoclay particles on the flame retarding characteristics of wood–fiber/plastic composites (WPC) using ASTM D635. The processing aspects of nanocomposites with WPC are presented. The processing techniques for controlling the degree of exfoliation and the cost aspect are also described. It turns out that the coupling agent used for wood–fibers is also effective for the exfoliation of clay, and therefore, no additional cost is required. This research indicates that the structure of nanocomposites (i.e., the degree of exfoliation) and the clay content used have a large impact on the flame retardancy of WPC. The flame retardancy is investigated as a function of these parameters. Based on this, a cost‐effective way to improve flame retardancy of WPC is presented. POLYM. ENG. SCI., 47:308–313, 2007. © 2007 Society of Plastics Engineers.

Critical Issues in Extrusion Foaming of Plastic/Woodfiber Composites

Foaming of wood-fiber/plastic composites (WPC) with a fine-celled structure can offer benefits such as improved ductility and impact strength, lowered material cost, and lowered weight, which can improve their utility in many applications. However, foaming of WPC is still a poorly understood art. This paper presents a review of material published, which address the various critical issues particularly in extrusion foaming of WPC, and the proposed processing techniques and strategies, for producing artificial wood with enhanced properties.