Effects of alkaline and silane treatments on the water‐resistance properties of wood‐fiber‐reinforced recycled plastic composites

Abstract

The water-resistance properties of wood-fiber-reinforced recycled plastic composites (WRPCs) prepared from postconsumer high-density polyethylene (HDPE) and wood fibers from saw mills were studied. Three methods consisting of an alkaline method (AM), a silane method (SM), and a combination of the alkaline and silane methods (ASM) were used to modify the wood fibers. The effects of fiber/matrix mix ratio and surface treatment on the moisture content, thickness swelling, and flexural strength change of the WRPCs, before and after immersion in 608C water for 8 weeks, were studied and analyzed. The flexural fractured surfaces of the WRPCs before and after immersion in hot water were examined, and the fracture mechanism of the WRPCs was discussed. The results showed that the different surface treatments of the wood fibers had significant effects on the moisture content, thickness swelling, and flexural strength of the WRPCs after a long immersion time in hot water. For WRPCs treated by ASM, the moisture content was the lowest, the thickness swelling was at a minimum, and the flexural strength was the highest. Higher water absorption of composites with fiber treated by the AM or SM methods, as compared to those treated by ASM, could be attributed to the incomplete adhesion and wettability between the wood fibers and the polymer matrix, which may have caused more gaps and flaws at the interface.

Glass fiber/wood flour modified high density polyethylene composites

“…As shown in Figure 4, the addition of HDPE‐ g ‐MAH obviously lowered the water absorption to below 1.5% when compared with the water uptake at 4.7% in absence of any compatibilizer. At the loading of 25 phr (B‐6), the water absorption was less than 1%, which is nearly negligible for the applications, because the hydrophilic fibers are effectively coated with the hydrophobic matrix and a water‐resistant film is formed around the fibers 9, 23…”

“…Chemical coupling by using various coupling agents or polymer compatibilizers is proved the most effective way, the main function of chemical coupling is to react with the hydroxyl groups on the fiber surface, making the surface wettable by the polymer to promote covalent bonding with the matrix 6, 8. The reinforcing effects of physical or chemical methods alone are limited, other reinforcements such as synthetic fiber, metal inserts, and glass fiber5–10 have been added into WPCs, the advantages of one type of fiber could complement deficiencies in the others due to some physical or chemical synergetic reinforcing effects,6, 11, 12 among them, the incorporation of GF is most effective.…”

Effect of filler loading and coconut oil coupling agent on properties of low‐density polyethylene and palm kernel shell eco‐composites

“…Usually, the natural filler has abundant hydroxyl groups that lead to poor wettability and poor adhesion with hydrophobic thermoplastic. Many filler treatments have been used to improve filler dispersion and adhesion with the thermoplastic matrix, such as alkaline treatment , esterification , use of silane coupling agent , and compatibilizer . Perhaps the most important of these filler treatments is the coupling agent, which can enhance the interfacial compatibility of hydrophobic thermoplastic and highly hydrophilic natural filler.…”

Preparation of highly filled wood flour/recycled high density polyethylene composites byin situreactive extrusion

“…Lei et al17 prepared WF/RHDPE composites by melt compounding in rheometer chamber and compression molding, and then investigated the influence of coupling agent type and content on the compounding rheology, RHDPE crystallization behavior, and properties of composites. Other researchers18–22 also reported the preparation and properties of WF/RHDPE composites. In these studies, WF content was in the range of 30–50%, and composite samples were manufactured by compression molding or injection molding.…”