Preparation And Properties Research Of Flax/PLA Composites

Poly(Lactic Acid) (PLA) is a typical green polymer since it is produced from renewable resources and can be finally degraded to carbon dioxide and water. PLA can not only reduce pollution to environment, but also economize petroleum resources. But PLA is friable and expensive. Flax fiber is one kind of natural plant fiber with good mechanical properties, and it's cheap, biodegradable and renewable. Flax/PLA composite, as a kind of new totally biodegradable plastic, take a balance between the high performance of PLA and the inexpensive of flax fiber.In this study, flax fiber was simply studied at first. Then, flax/PLA composites, flax/PLA composites with fiber treated by KH550, flax/PLA composites with plasticizer PEG, and flax/PLA composites with fiber treated by KH550 and PEG were prepared by Haake polymer work station. Test samples of all kinds of composites were produced using compression molding. The effects of different treatment were studied by testing melt flowing rate of composites, DSC and DMA of compression molding samples. Samples of Flax/PLA composites without any treatment were also produced by injection molding technology. The thermal properties, thermal stability, dynamic properties, mechanical properties and characteristics of impact fracture of Flax/PLA composites, which could evaluate the influence of Flax content on the composites'properties, were studied. The following conclusions can be drawn from the paper:1. Melt flowing properties of composites got worse with the increasing of flax content. KH550 didn't work obviously to MFR of composites. However, the effects of plasticizer PEG on MFR of composites were greatly.2. Glass transition temperature, melting temperature and crystallization enthalpy of composites were enhanced with the increasing of flax content, but cold crystallization temperature decreased. Glass transition temperature, cold crystallization temperature and melting temperature decreased and no double melting peaks with treated by KH550. Compatibility between flax and PLA was improved. Effects of plasticizer PEG were so obvious that the glass transition temperature of composites decreased.3. With the increasing of flax content and silane coupling agent treating, storage modulus and loss modulus of composites were enhanced, Tanδdecreased and Tg increased. Adding plasticizer PEG, storage modulus and loss modulus of composites were enhanced obviously. Effects of plasticizer PEG were so obvious that the glass transition temperature Tg and cold crystallization temperature Tc of composites decreased. However, when KH550 and PEG worked together, effects of PEG were obvious and effects of KH550 were not.4. For test samples of Flax/PLA composites without any treatment, although flexural strength hasn't changed, thermal stability, thermal properties, dynamic properties, tensile strength and flexural modulus were enhanced obviously with the increasing of flax content.5. The results of cold notched bending test were better than that of normal notched bending test. Observing characteristic of fracture by scanning electron microscope(SEM), it was found that fracture roughness of cold test samples decreased and structure turned compact. However, compatibility between flax and PLA got worse because of cold treatment.