Properties of flat-pressed wood plastic composites as a function of particle size and mixing ratio

Abstract

This paper presents the effects of particle size and mixing ratio on the properties including physical, mechanical, and decay resistance of wood plastic composites (WPCs). In addition, it also presents the effects of immersion temperatures on water absorption (WA) and thickness swelling (TS) of the WPCs. WPCs with a thickness of 6 mm were fabricated from Albizia richardiana King & Prain wood particles and recycled polyethylene terephthalate (PET) by the flat-press method. To prepare the WPCs, two different wood particle sizes (0.5-1.0 and 1.01-2.0 mm) were used along with four different mixing ratios (w/w). Subsequently, the physical properties include density, moisture content, WA, and TS, and mechanical properties include modulus of elasticity (MOE) and modulus of rupture (MOR) of the produced WPCs was evaluated. Furthermore, decay resistance was evaluated by the weight loss percentage method. Moreover, the effects of immersion temperatures on WA and TS of WPCs after 24 h of immersion in water at three different temperatures, i.e., 25, 50, and 75 °C were investigated. Results showed that the wood particle size had impact on WPC's density (only 6% decreased with the increase of particle size); however, the density decreased by 29% when the wood particle content increased from 40 to 70%. The WA and TS gradually increased with the increase of particle content and decrease of particle size. In addition, WA and TS increased proportionately with increasing immersion temperature from 25 to 75 °C. Furthermore, the highest MOE (2570 N/mm 2) was found for the WPCs fabricated from large wood particles having the ration of 50:50 (wood particle:PET). For decay resistance, WPCs consisted of larger particles and higher PET content showed greater resistance against decay. Therefore, it is comprehensible that fabrication of the WPCs from 50% large particles and 50% PET is technically feasible and further improvement of WPC performance like enhancement of MOE and reduction of density using coupling agent and agricultural waste fibers, respectively, in the WPC formulation is recommended.

Comparison of the Physico-Mechanical and Weathering Properties of Wood–Plastic Composites Made of Wood Fibers from Discarded Parts of Pomelo Trees and Polypropylene

“…In addition, the moisture content of the WPCs decreased with decreasing WF size, and the WPCs with less than 60 mesh WFs (WPC S60 ) exhibited the lowest moisture content (0.90%). This trend is similar to that reported by Rahman et al [45] for composites made of recycled polyethylene terephthalate (PET) and different sizes of WFs. Rahman et al [45] found that there were more voids in the WPCs that contained larger WFs, which made it easier for moisture to penetrate through the openings of the composites.…”

“…This trend is similar to that reported by Rahman et al [45] for composites made of recycled polyethylene terephthalate (PET) and different sizes of WFs. Rahman et al [45] found that there were more voids in the WPCs that contained larger WFs, which made it easier for moisture to penetrate through the openings of the composites. Moreover, the WPCs with the smallest WFs (WPC S60 ) showed the lowest MOR (39 MPa) and MOE (2.3 GPa) values among WPCs with different sizes of WFs.…”

“…Moreover, the WPCs with the smallest WFs (WPC S60 ) showed the lowest MOR (39 MPa) and MOE (2.3 GPa) values among WPCs with different sizes of WFs. A similar result was also observed in studies by Rahman et al [45] and Chen et al [46]. However, the tensile properties of WPC S16 were lower than those of other WPCs.…”

“…These results are consistent with the results reported by Ashori and Nourbakhsh [47], Feng et al [48], and Onuoha [49] for the changes in tensile properties with WF sizes. A possible reason is that the smaller WFs were dispersed more thoroughly and provided a larger contact area with the PP matrix, thereby promoting better interfacial adhesion and lower stress concentrations [45,48,49]. On the other hand, large WFs had rougher surfaces and looser structures, which resulted in poorer compatibility between the PP matrix and WFs.…”

Research Progress of Wood-Based Panels Made of Thermoplastics as Wood Adhesives

“…A general rule for mixing is that large pieces of wood shavings should be matched with large pieces of thermoplastic, and small pieces of shavings matched with small pieces of thermoplastic. Increasing the fiber aspect ratio can produce a larger contact area between the fiber and plastic matrix, which is able to improve the composites’ performance [ 55 , 56 ]. Qi [ 31 , 57 ] prepared cotton stalk–HDPE-oriented composites.…”