Composites from recycled polypropylene and rubberwood flour

Abstract

The mechanical properties of composites from recycled waste plastic and waste sawdust are of interest in trying to convert these waste streams to useful products. The development of these composites from natural fiber is therefore receiving widespread attention due to the growing environmental awareness. The effects of compositions were investigated including different grades of plastic (virgin and recycled) and amounts of wood flour, coupling agent, and ultraviolet (UV) stabilizer on mechanical and physical properties of polypropylene/rubberwood flour (RWF) composites. Virgin polypropylene gave better mechanical properties than recycled (recycled polypropylene (rPP)), both in composites and as unfilled plastic. RWF content exceeding 25 wt% enhanced the strength of RWF-reinforced rPP composites. The modulus and hardness of composites increased linearly with wood flour loadings. Maleic anhydride-grafted polypropylene (MAPP) as a coupling agent increased the strength, modulus, and hardness of the composites. However, addition of 1 wt% UV stabilizer degraded the mechanical properties. Therefore, 4 wt% MAPP content is recommended to achieve good mechanical properties of rPP/RWF composites, while the amount of UV stabilizer should be as small as possible to avoid its negative influence.

Minimizing the creep of recycled polypropylene/rubberwood flour composites with mixture design experiments

“…High wood flour content increases the modulus of elasticity (MOE) of composites, 31 so that higher stress is required for the same deformation. 7,32 The choice of MAPP content between 3 and 5 wt% barely affected the C e . Generally, the addition of coupling agent in the WPCs decreases the creep strain due to the improved filler dispersion and improved interfacial adhesion between wood flour and polymer matrix, [33][34][35] whereas too much MAPP relative to wood flour will cause selfentanglement, resulting in slippage with the PP molecules.…”

“…6 Most of the wood waste can be used in medium-density fiberboard and particle board. 7 However, the use of wood waste as reinforcement in plastic composites is of great interest, with environmental and economic benefits. The advantages of wood particles include biodegradability, low health hazard during handling, and non-abrasive nature, 8,9 when substituted for synthetic fillers such as glass fiber, carbon fiber, and other inorganic fillers.…”

Optimizing the formulation of polypropylene and rubberwood flour composites for moisture resistance by mixture design

“…This may be attributed to the nonuniform spatial distribution of wood flour, polymer, and UV stabilizer. 9,34 When WPCs experienced with the nonuniform spatial distribution and poor interfacial adhesion between the compositions, it allows easier access of water into the structure. Figure 3 displays the numerically optimized composition, based on these model fits.…”

“…14,15 Natural fibers have successfully improved the mechanical properties of plastic composites, as the following examples demonstrate. Homkhiew et al 9 investigated the effects of rubberwood content on the mechanical properties of recycled PP composites and found that the modulus and hardness of composites increased linearly with an increase of wood flour loadings in the range of 25-45 wt% wood flour. Karmarkar et al 16 also reported that the tensile strength and modulus linearly increased with an increase of wood fiber from 10 to 50 wt% in PP composites.…”

“…Generally, rubberwood waste is dumped in landfills or burned, but some is used in medium-density fiberboard and particle board. 9 Rubberwood waste as reinforcement in plastic composites is of great interest both for economic and for environmental reasons. Natural fiber (wood waste)-reinforced thermoplastics also offers many advantages including biodegradability, renewable character, low cost, absence of associated health hazards, and low wear of processing equipment, [10][11][12][13] when compared with synthetic fibers.…”