JEC COMPOSITES MAGAZINE - Issue #66 - July/August 2011 - 40

biocomposites

Fig. 3: Tensile strength and dimensional stability of PLA

the viability studies carried out in 2008 to test cutting-edge materials such as PDLA, nanocellulose, nanoclays and mineral fillers from organic residual resources, the scientists from CTAG defined the weaknesses of biocomposites and strategies to face them in order to introduce these green materials in a mass-produced vehicle. The following weaknesses were established: - High hydrolysis potential resulting in a shortening of molecular chains and material degradation. Biopolymers then become sticky and brittle, with poor dimensional stability. This effect is even worse at high temperature. Therefore, these materials cannot pass standard ageing tests. - High volatile compound emissions that negatively affect the results of tests to determine odour and fogging potential. This is critical for materials used inside a car, since volatile compounds prevent proper glass defogging, thus limiting the visual field. According to OEM restrictions, the glass reflectivity due to volatile emissions must not be reduced by more than 15%. - Poor compatibility and dispersion of natural reinforcements due to poor

interactions between surfaces, resulting in aggregates, micro-notches, residual stress, etc. - Processing requires specific knowhow. Most of the commerciallyavailable neat biopolymers are not ready for use in the automotive industry. They present a very narrow processing window due to their thermo-mechanical sensitivity. Preliminary drying and degassing are usually required and natural fibre dosing is complicated due to density differences. - Further price evolution is needed to approach them to commodities and larger-scale infrastructures are still need to be developed to deliver the volumes required by the sector.

developing novel biomass-based thermoplastic composites to overcome the current weaknesses of biopolymers in terms of complying with automotive standards through the following research lines: 1. Design and modulation of new molecular architectures based on polylactic acid (PLA): a. Via blending with PDLA to produce sc-PLA and thus maximize the nucleation efficiency, crystallization rate and heat distortion temperature (HDT) of the material. b. Via the transesterification of PLA chains to obtain a PLA stereoblock copolymer using the ability of PLLA and PDLA to form high-melting crystals. Through the use of different block and chain lengths, the resulting material will show improved mechanical performance and processing behaviour. 2. Improvement of polyhydroxybutyrate (PHB) properties, adapting their structure and nature to automotive specifications. 3. Synthesis of a new protein-based copolymer using silk-like crystalline and elastine-like flexible blocks to obtain a new material with a unique balance of mechanical properties and thermostability.

jec composites magazine / No66 July - August 2011

The ECOplast project
Within the framework of this four-year project started in June 2010 and cofunded by the European Commission under the 7th Research Framework Programme (7FP), scientific and industrial researchers aim at providing a suitable solution covering both the closest technical horizon, through short-term results close to the market, and future needs, through the tailormade synthesis and functionalization of new high-tech materials. Thus, the first step will consist in

JEC COMPOSITES MAGAZINE - Issue #66 - July/August 2011

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #66 - July/August 2011