Natural Fibre Reinforced Cellulose Acetate
Karen Yu, Janny Ke
Sir Winston Churchill Secondary
Floor Location : S 208 E

There is an increasing demand for high performance materials that are not detrimental to the environment. The purpose of our project to reinforce cellulose acetate plastic with natural fibres, namely hemp, flax, and pomelo skins. Cellulose acetate is a thermoplastic made from natural materials, usually cotton or wood pulp, or potentially household or agricultural wastes high in cellulose. It is completely biodegradable and does not release toxins into the environment when it degrades, unlike most of the current plastics on the market.rnrnWe chose the anisotropic short fibre method of reinforcement, which involves cutting up the fibres into short pieces and mixing them randomly throughout the entire composite. Although composite materials look heterogeneous, their properties can be generalized and tested as the heterogeneity is almost uniform throughout.Our samples were made by dissolving cellulose acetate in acetone and mixing the fibres into it in a 25% by mass ratio.rnrnThe tensile strength test was conducted by clamping a sample between two clamps and hanging increasing weights from the bottom clamp. The change in thickness of the sample was measured using a micrometer, and the using these values the tensile modulus and Young's modulus were calculated. We plotted graphs of the tensile modulus against the amount of force applied, the percent change in thickness over the mass added, and Young's modulus over the amount of force applied. From these three graphs, we found that hemp performed the best out of all the samples because the largest amount of force could be applied to it with the least amount of deformation. Flax could also sustain the same amount of force as hemp, but had more deformation. The pomelo skin sample actually performed worse than the control sample. rnrnThe flexural test consisted of bending various lengths of the specimen and evaluating their angle of initial fracture, angle of break, difference between these two angles and deformation in thickness; the upper limit of bending is 165 degrees due to apparatus setup. The angle of initial fracture for all of the specimen are found to be extremely similar (around 80 degrees), which reflects the similar matrix strength of the composites. However, the angle of break differs greatly, with flax composites having near 150 degrees followed by flax composites, pomelo composites, and the control (the angle of which is often the same as the angle of initial fracture). The huge difference between the angle of fracture and angle of break for the fibre reinforced composites may be due to the fibres bridging across broken cellulose acetate plastics, supporting the fractured matrix and distributing the stress; unreinforced plastics, on the other hand, breaks right away as it lacks this support. The deformation in thickness is the greatest for the fibre-reinforced composites and least for the control, showing the former's flexural strength and the latter's brittleness. Overall, flax composites are found to have the highest flexural strength, followed by hemp composites, control, and pomelo composites. Also as expected, as the length decreased the angle of break also decreased.