Low cost, light weight, recyclability, and high specific strength of natural fibres make them a good replacement for synthetic fibre such as glass in fibre reinforced plastics (FRP). Green and ecofriendly source of these fibres offer less reliance on oil sources. However, their moisture uptake ability, low thermal stability and quality variations are some disadvantages that restrict their use.

Biodegradable polymers or biopolymers such as polylactic acid polymers (PLA) are polyesters of lactic acid, and originally made from renewable agricultural raw materials e.g. corn starch. Development of new composite products from the existing renewable resources has a strong potential to bring a new biodegradable composite material suitable for the automotive and packaging industry to replace non-renewable petroleum based plastics. These biodegradable composites could degrade completely in soil or by composting process and do not emit any toxic or harmful components.

The purpose of this work is to investigate the effects of increasing natural fibre content, and also adding Biomax modifier on the mechanical properties of poly lactic acid. PLA was reinforced with two different kinds of sustainable natural fibres, cotton, and jute fibres respectively. Biomax strong 120 was used as modifier for PLA/natural fibre composites in order to improve the impact strength and toughness properties. Mixtures of different fibre mass proportions as reinforcement, and PLA as a base resin with modifier additive were compounded in a twin-screw extruder. The extruded materials were processed in a novel compression moulding system to produce test samples. Composites without any modifier content were also produced under the same conditions and used as reference materials.

Addition of plant fibres to the PLA reduces the composites flexural strength, while improves the elastic modulus significantly, compared to neat PLA. PLA 3001D based composites containing 40% jute fibre exhibited the highest stiffness (5.9 GPa) amongst the composites. Investigation of the impact properties of the composites showed that increasing fibre mass proportion leads to an increase in the impact strength of the composites. The impact strength of the PLA/cotton composite is more promising than PLA/Jute composites. The most significant result is that addition of even 3% Biomax Strong 120 had a positive effect on the impact properties of the specimens.

Analysis of the rheological properties of the composites demonstrates that the cotton fibre reinforced PLA has higher complex viscosity than Jute fibre reinforced PLA composites. The DSC results explain that the crystallization temperature increases with increasing the jute fibre content. Furthermore composite‟s microstructure was monitored using Scanning Electron Microscope (SEM). A better adhesion between the cotton fibres and the PLA matrix than jute fibres and PLA was observed in the SEM images.