The Effects of Recycled Polypropylene/Wood Flour (r-PP/WF) Composites with and without Coupling Agent on Mechanical Properties

Plastic and wood have been indirectly causing global warming and developing
domestic waste. Plastic is massively produced every day, so it contributes in high
municipal waste generation rate and it is non-biodegradable. With depleting number
of trees and forests, wood wastes are either burned or disposed which resulting in
extra consumption, and pollution of nature. Therefore, by combining them into
Wood Plastic Composite, we can recycle and reuse the product to replace current
landscaping and furniture products. The main objective of this project is to study
effects of different compositions on the mechanical properties of r-PP/WF
composites and investigate the effects of coupling agent on the mechanical properties.
Therefore, the scope of this project was focused on finding the composition of r-
PP/WF that produces the best mechanical properties and investigating the effects of
coupling agent on the composites. Thus, the methodology started with drying the WF,
sieved the WF, granulated the r-PP, mixed r-PP and WF in the twin screw co-rotating
extruder machine, then the pellets were hot-pressed in compression molding machine
to create 20 cm x 15 cm x 0.4 mm plates, then cut into ASTM D638 (type I), ASTM
790 and ASTM 256 samples before proceed with the standard tensile, flexural and
Izod impact testing. Then, the fractured samples were examined under SEM to see its
microstructure. From the mechanical testing, the tensile strength of the composite
reduced about 15% - 49% if compared to r-PP, but with coupling agent, the tensile
strength improved 16% - 45%. While for flexural strength, the composites reduced
5% - 45% of its strength if compared to r-PP but improve 29% - 49% with coupling
agent. On the other hand, flexural modulus improved up to 135% if compared to r-PP
and the improvement by adding coupling agent is up to 80%. The impact strength
also reduces 26% - 38% if compared to r-PP and slightly improvement done by
coupling agent about only 2% - 12%. The best composite is 30% of WF, 65% of r-PP
and 5% of FB. The microstructural analysis done by using SEM explains the
mechanical properties behaviour. As a conclusion, the mechanical properties reduced
probably due to processing techniques and the improvement done by coupling agent.
The objectives of this project were achieved and this project proves that r-PP/WF
composites are one of comparable alternative material for furniture and landscaping
purposes.