Natural Fiber-Plastic Composites for Construction Applications
Shafiee Monfared, Ehsan
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Natural fiber-plastic composites containing natural fibers as dispersed phase (filler) and polypropylene as matrix are an important and emerging type of compounds used in construction, automotive, consumer products, etc. To evaluate and understand the properties of NFPCs in construction industry, it is important to check the mechanical properties of laboratory prepared NFPCs with various fibers, polypropylene grades and additives. To achieve this goal, the fibers are needed to be ground and be thoroughly analyzed for fiber sizes distributions and aspect ratios distributions to identify the size and shape of fibers to correlate such information with mechanical properties of the NFPC. In this dissertation, it was found that oat hull fibers were smaller than bagasse fibers on average and had lower aspect ratios compared to bagasse fibers. Using Minitab software, two-level factorial experimental design was employed in three design of experiments (DOEs) to check the effect of fiber type, fiber content, coupling agent content, impact modifier type and impact modifier content on mechanical and impact properties of NFPC. Samples as per DOE runs were conditioned, compounded with twin screw co-rotating extruder, injection molded and tested. The results indicated that bagasse interacts much better compared to oat hull with coupling agent. As well, styrene copolymerized with ethylene/propylene rubber appeared to be more effective in increasing impact properties. Coupling agent appeared to very effective increasing tensile properties although had mild deteriorating effect on impact properties. It was found that compared to unfilled polypropylene, bagasse as a natural filler was very effective on Flexural properties, however, bagasse decreased the tensile properties when compared to unfilled polypropylene. SEM microscopy was used to observe mechanism of impact and appeared to support numerical tests results of Izod Impact Energy responses. Statistical methods generally validated the results and best normal residual plot fit was for Izod Impact results which was almost linear. The worst fit however, belonged to mean failure Energy results. Statistical validity of results was also considered in detail using normal residual plots and were reported in detail for each DOE. Generally, the results were validated with some exceptions. It is important to evaluate and understand the effect of UV weathering on properties of commercially available NFPC products. To achieve this goal, a Design of experiment was designed to run tests for effect of weathering and physical impact location on multi-axial impact properties of an NFPC product. Commercial products were cut to size and impacted by multi-axial impact tester and work versus displacement graphs were generated. Effect of UV weathering and impact location was studied on Multi-Axial impact responses of NFPC commercial roofing product and results indicated UV weathering deteriorated total energy, energy to maximum load and maximum load of roofing product. The location of impact either in middle or side or with/without back reinforcement, was not found to be effective on multi-axial impact properties The statistical method used was mildly validated using normal residual plots.