From Science & Research
From Science & Research New biocomposites for car interior The development of novel biocomposites based on new biopolymers, reinforced with natural fibers, nanofillers and additives, for applications in automotive interior parts was the goal of the European Research Project ECOplast, which is now successfully nearly completed. The project consortium incorporates 13 partners coming from 5 European countries and is led by the Spanish Galician Automotive Technological Centre (CTAG, (Porriño Pontevedra, Spain) Requirements for interior parts in automotive are manifold: mechanical stability, odor, fogging and temperature resistance are only a small sample of what the producers have to take care for. Bioplastics which are available nowadays do not meet the requirements of the automotive industry. Pablo Soto from Grupo Antolin, a Spanish automotive supplier who was a partner in the Ecoplast consortium, states: “We recognize that the automotive industry wants to use bio-based plastics and natural fibers on the condition that they pass the requirements for materials in interior parts that are really challenging, at a level of price similar to current materials“. Before Ecoplast started, the insufficient temperature resistance of PLA, for example, and the fogging behavior and volatile emissions of PHB prevented their use in car interiors. Improvements of PHB and PLA In the past, the odor and fogging of PHB limited its use in cars. Within the scope of the Ecoplast project, AIMPLAS (Paterna, València, Spain) studied the efficiency of supercritical CO 2 (sc-CO 2 ) in the reduction of the volatiles. A significant reduction of the organic volatile substances by up to 80 % was achieved. However, the process was too expensive and instead of it a new formulation of PHB which reduces volatiles was developed. The components that lead to fogging or volatiles emissions were successfully identified and replaced by others. As a result BIOMER (Krailling, Germany) now offers a new formulation of PHB for car interior parts. Corbion (Gorinchem, The Netherlands) improved the temperature resistance of PLA by using PDLA nucleated PLLA materials, so-called nPLA. A separately developed high impact blend (n-PLAi) was used to overcome the low impact strength of PLA. Compatibilty of wood fibers The incompatibility of hydrophilic wood fibers and hydrophobic thermoplastic matrices causes weakness to composite material strength properties, especially impact strength. VTT (Espoo, Finland) modified the cellulose fiber surface to be more compatible with polymer matrix utilizing a new dry compacting method and reactive plasticizers or additives capable of forming bridges between fiber and polymer matrix. The resulted PLA-cellulose fiber composite material showed increased impact and tensile strength values. With rising amount of fibers the heat resistance, heat deflection temperature, HDT (A), of the composite material increases (see fig. 1). Fig. 1: Heat deflection temperature in dependence of fiber amount All in all, great improvements in the proprieties of the PLAcellulose fibre composites were achieved, just a few of the requirements for car interiors, as fogging or resistance to humidity, need further developments. PHB long natural fiber composites Compression molding appeared as the best option to reinforce PHB with fiber mats. The best results were achieved by Aimplas with impregnated flax mats. Using this process the PHB penetrates completely through the mats. The obtained samples show good mechanical properties and a nice appearance (see fig. 2). Values for unnotched Charpy impact reached more than 40 kJ/m 2 and the flexural modulus over 3 GPa. Fig. 2: PHB with flax mats 18 bioplastics MAGAZINE [03/14] Vol. 9
From Science & Research Improvements using nanocellulose and nanoclays First trials with compounds of n-PLAi with nanocellulose indicated favourable results but the compound has to be optimized, which needs more research work. Preliminary tests of using nanocellulose as an additive in silk-elastin-like polymer matrices were promising, too. NBM has developed the first organomodified clays for the use in PLA compounds (see fig. 3). The preparation included the formulation, optimization and fabrication of the nanofillers according to proprietary purification and surface modification technology. A compound based on n-PLAi with 5 wt % of this new nanoadditive based on natural clays complies with all requirements defined in the project. New protein-based copolymer Basic research for the development of a new protein-based copolymer using silk-like crystalline and elastin-like flexible blocks (silk-elastin-like polymers, SELP), performed by the University of Minho, and for the scale-up of SELP production revealed good results. More details of this can be found in Casal et al. (2014). Additionally, the methodology and knowhow to produce biocomposites based on these novel polymers was developed within the Ecoplast project in collaboration with PIEP. New approaches to the biocomposites processing technologies PIEP addressed the possibility of processing the target biocomposites using a more energy efficient technology – iCIM: integrated twin screw extruder and in-line injection molding (see fig. 4) - and hence profit from the inherent advantages for this type of materials provided by iCIM: shorter residence times, lower shear stresses and superior maintenance of fiber morphology. For the studied n-PLA biocomposite it was possible to obtain, at least, the same level of mechanical performance, when compared to the results achieved with conventional technologies, sustaining the potential of this technology. Conclusion Ecoplast project results are very promising and may lead to the production of innovative completely bio-based composites which are validated for the automotive industry: Organomodified clays for PLA were developed. A compound based on n-PLAi with 5 wt % of this new nanoadditive complies with all requirements defined in the project. A great improvement of PHB properties was achieved, especially for PHB reinforced with short fibers which yielded results far better than expected. Additionally, of special importance is the development of a new PHB formulation that meets the automotive fogging requirements. PHB reinforced with mats shows interesting results. The materials can be used in different applications. For both materials under investigation in the Ecoplast project, n-PLA and PHB, the cycle times have been remarkably reduced during the project. Material prices are still high but are expected to be drastically reduced upon large-scale industrial commercialization of polymer production. Additionally, the reduction of processing costs has to be one of the principal lines of investigation in the near future. Fig. 3: TEM image of nanoclay in PLA matrix Fig. 4: iCIM: integrated twin screw extruder and in-line injection molding Literature: M. Casal, A. Cunha, R. Machado: „Future Trends for Recombinant Protein-Based Polymers: The Case Study of Development and Application of Silk-Elastin-Like Polymers“ in: Kabasci, S. (Ed.): Biobased Plastics: Materials and applications. (Wiley series in renewable resources, 11) Chichester: Wiley, 2014, S. 311; ISBN 978-1-119-99400-8. The partners involved in the project are: Centro Tecnológico de Automoción de Galicia (CTAG), Spain (coordinator) Asociación de Investigación de Materiales Plásticos y Conexas – AIMPLAS, Spain PIEP Associação sociação – Polo de Inovação em Engenharía de Polímeros, Portugal Biomer, Germany FKuR Kunststoff GmbH, Germany Fraunhofer-Institut für Umwelt-, Sicherheits- und Energietechnik UMSICHT, Germany Grupo Antolín – Ingeniería S.A., Spain Megatech ech Industries Amurrio S.L. (MEGATECH), Spain NanoBioMatters R&D (NMB), Spain Pallmann Maschinenfabrik GmbH & Co, Germany Corbion (Purac), Netherlands University of Minho (UMINHO), Portugal VTT–T Technical Research Centre of Finland, Finland www.ecoplastproject.com bioplastics MAGAZINE [03/14] Vol. 9 19
