Biodegradable polymer matrices can be an alternative to the use of polyolefins in the preparation of natural reinforced composites?

LÓPEZ, JOAN P.; PÈLACH, MARÍA A.; MÉNDEZ, JOSÉ A.; VILASECA, FABIOLA; CAÑIGUERAL, NURIA; LLOP, MIQUEL; VALLEJOS, MARÍA E.; MUTJÉ, PERE

Puerto de la Cruz, Tenerife - España

Congreso; 6ª Congreso Internacional de la ANQUE - Química y Desarrollo Sostenible; 2006

ASOCIACIÓN NACIONAL DE QUÍMICOS DE ESPAÑA

In the field of the preparation of composites reinforced with fibres, the most often used polymer matrix is polypropylene (PP). This polymer can be effectively reinforced with natural fibres leading a limited increase in the mechanical properties, which can be improved by the addition of coupling agents1. These composites can be used in a lot of applications such as transports, automotive industry and building construction. But these composites have the disadvantage of the low or nule biodegradable character of the polymer matrix producing an ecologic impact derived from the storage of residues.  On the other hand, synthetic and natural biodegradable polymers can also be considered as polymer matrices for preparing composites. Under different degradation process synthetic materials such as poly(L-lactic acid), poly(e-caprolactone), etc…, have been applied mainly in the field of the biomaterials. On the other hand, the use of natural biomatrices is being increased due to their tolerance with the environment related with the non-toxicity of the degradation products and from the point of view of the acquisition, since they come from renewable resources. Thus, one of the most often researched biopolymers is starch. This biopolymer is a polysaccharide synthesised by plants in the form of granules. The principal crops used for its production include potatoes, corn and rice. Starch has been widely used as a raw material in film production because of increasing prices and decreasing availability of conventional film-forming resins. Starch films possess low permeability and are attractive materials for food packaging. But these biodegradable matrices, like the non-biodegradable ones, need the addition of fibres to improve their properties. The addition of natural fibres derived from cellulose gives rise to biocomposites totally biodegradable, more compatible with the environment and the “green chemistry”. There are different kind of fibres depending on the resource being flax, hemp, cotton, jute and pine the most often used. As it was mentioned, the main component of these fibres is cellulose, a polysaccharide with pending hydroxyl groups, able to interact with other polar groups through the establishment of hydrogen bonds. Hemp strands is a reinforcement that has been considered in a lot of occasions as reinforcement of non-biodegradable matrices. The hemp strands have a rough surface and are a part of the tail of the plant that has the highest content of cellulose. In this work, new completely biodegradable composites have been formulated, using starch as polymer matrix and hemp strands as reinforcement. The influence of the addition of the reinforcement was evaluated in terms of mechanical properties. Tensile test was carried out obtaining values of muduli and strengths with those of plain starch. The results weree compared with those formulations of composites based on PP as polymer matrix coupled with MAH-PP (4wt%, regarding reinforcing content).