The effect of inorganic fillers on the properties of wood plastic composites

The effect of inorganic fillers including precipitated calcium carbonate (PCC), glass fiber (GF), and nano-clay on properties of structured WPCs was investigated. In PCC-bamboo-polymer hybrid composites, tensile and flexural moduli were improved with increasing PCC content. After silane treatment of bamboo, RBF-filled hybrid composites showed better mechanical properties compared to those of GBP-filled hybrid composites. The hybrid composites showed 3-4 times higher modulus than those of PCC-filled composites at high PCC levels. Various property differences were observed between weak- and strong-core coextruded systems with shell composition changes. While the weak-core systems showed improved flexural strengths compared to their core-only control, the strong-core systems had lowered flexural strengths. In both systems, impact strengths increased at low shell filling levels but decreased at high shell filling levels. Impact fracture types varied with core quality and shell filling composition. Coextruded composites with treated PCC-filled shell showed better water absorption (WA) property compared to core-only controls and coextruded composites with high WF-filled shell. Plastic-only shell increased overall coefficient of thermal expansion (CTE) of coextruded composites, but filled shells led to the CTE decreases of coextruded composites. GF in shell behaved as an effective reinforcement for coextruded composites. The comparisons of flexural property among different core systems show that GF reinforcements were optimized at high GF loadings in a shell layer and GF alignments in the shell layer also played an important role. In coextruded composites with different shell thicknesses, the flexural property enhanced with the increase of shell bending modulus and strength at a given shell thickness. When the flexural property of shell was less than that of core, the increase of shell thickness led to reduced flexural property. On the other hand, when the flexural property of shell was higher than that of core, the opposite was true. In sound transmission loss (TL) testing, the stiffness and surface density were major factors influencing the sound insulation property of materials. The experimental TL results showed that the addition of clay or PCC and/or wood fiber (WF) fillers led to the increases of general resonance frequencies and TL in filled composites. However, at high filling levels, composite stiffness decreases led to TL reduction. The experimental TL curves of filled HDPE and WPCs were well approximated with the combined TL predictions from their corresponding stiffness-1 and stiffness-2 TL for S-region and mass law TL for M-region

Recent Advances in the Sound Insulation Properties of Bio-based Materials

Many bio-based materials, which have lower environmental impact than traditional synthetic materials, show good sound absorbing and sound insulation performances. This review highlights progress in sound transmission properties of bio-based materials and provides a comprehensive account of various multiporous bio-based materials and multilayered structures used in sound absorption and insulation products. Furthermore, principal models of sound transmission are discussed in order to aid in an understanding of sound transmission properties of bio-based materials. In addition, the review presents discussions on the composite structure optimization and future research in using co-extruded wood plastic composite for sound insulation control. This review contributes to the body of knowledge on the sound transmission properties of bio-based materials, provides a better understanding of the models of some multiporous bio-based materials and multilayered structures, and contributes to the wider adoption of bio-based materials as sound absorbers

Effects of Methylenediphenyl 4,4\u27-Diisocyanate and Maleic Anhydride as Coupling Agents on the Properties of Polylactic Acid/Polybutylene Succinate/Wood Flour Biocomposites by Reactive Extrusion

Polylactic acid (PLA)/polybutylene succinate (PBS)/wood flour (WF) biocomposites were fabricated by in situ reactive extrusion with coupling agents. Methylenediphenyl 4,4\u27-diisocyanate (MDI) and maleic anhydride (MA) were used as coupling agents. To evaluate the effects of MDI and MA, various properties (i.e., interfacial adhesion, mechanical, thermal, and viscoelastic properties) were investigated. PLA/PBS/WF biocomposites without coupling agents revealed poor interfacial adhesion leading to deteriorated properties. However, the incorporation of MDI and/or MA into biocomposites showed high performances by increasing interfacial adhesion. For instance, the incorporation of MDI resulted in improved tensile, flexural, and impact strengths and an increase in tensile and flexural modulus was observed by the incorporation of MA. Specially, remarkably improved thermal stability was found in the PLA/PBS/WF biocomposites with 1 phr MDI and 1 phr MA. Also, the addition of MDI or MA into biocomposites increased the glass transition temperature and crystallinity, respectively. For viscoelastic property, the PLA/PBS/WF biocomposites with 1 phr MDI and 1 phr MA achieved significant enhancement in storage modulus compared to biocomposites without coupling agents. Therefore, the most balanced performances were evident in the PLA/PBS/WF biocomposites with the hybrid incorporation of small quantities of MDI and MA

Sound Transmission Properties of Mineral-filled High-Density Polyethylene (HDPE) and Wood-HDPE Composites

Wood plastic composites (WPCs) offer various advantages and potential as a competitive alternative to conventional noise barriers. For this purpose, the influence of composite formulation on the sound transmission loss (TL) of WPCs needs to be fully understood. In TL testing, stiffness and surface density are major factors influencing the sound insulation property of filled plastics and WPCs. Experimental TL values decreased as sound frequency increased; and the TL values increased after passing a certain frequency level. The comparison of experimental TL curves among filled composites showed that the addition of fillers led to an increase in resonance frequency and TL values. However, at high filling levels, the stiffness decrease led to TL reductions. The experimental TL curves of filled composites, composed of mass law and stiffness law predictions, were well approximated with their combined TL predictions

High Density Polyethylene Composites Reinforced with Hybrid Inorganic Fillers: Morphology, Mechanical and Thermal Expansion Performance

The effect of individual and combined talc and glass fibers (GFs) on mechanical and thermal expansion performance of the filled high density polyethylene (HDPE) composites was studied. Several published models were adapted to fit the measured tensile modulus and strength of various composite systems. It was shown that the use of silane-modified GFs had a much larger effect in improving mechanical properties and in reducing linear coefficient of thermal expansion (LCTE) values of filled composites, compared with the use of un-modified talc particles due to enhanced bonding to the matrix, larger aspect ratio, and fiber alignment for GFs. Mechanical properties and LCTE values of composites with combined talc and GF fillers varied with talc and GF ratio at a given total filler loading level. The use of a larger portion of GFs in the mix can lead to better composite performance, while the use of talc can help lower the composite costs and increase its recyclability. The use of 30 wt % combined filler seems necessary to control LCTE values of filled HDPE in the data value range generally reported for commercial wood plastic composites. Tensile modulus for talc-filled composite can be predicted with rule of mixture, while a PPA-based model can be used to predict the modulus and strength of GF-filled composites