Meriplast A novel protein-based bioplastic

Transcription

1 Meriplast A novel protein-based bioplastic Revealing the potential of wheat proteins Wheat gluten is unique amongst vegetable proteins due to its specific visco-elastic properties, which are notably essential for quality in bread making. Tereos Syral has developed a process which enables to maintain the visco-elasticity of wheat gluten into a novel flexible and elastic biomaterial. Reveals the potential of cereals

2 Why use Meriplast? Sustainability Meriplast is 100% based on renewable raw materials (wheat and oilseeds such as rapeseed or sunflower) and 100% biodegradable. The production process is very mild and fully complies with the principles of green chemistry. Mechanical and physical properties Meriplast has unique flexibility & elasticity properties. It shows a good resistance to torsion and folding. It is not soluble in water but a prolonged immersion in water will affect the materials mechanical properties. Sensory Meriplast displays outstanding sensory properties. It has a very good touch, a good grip without stickiness, it is permeable and absorbs water. It has a pleasant cereal smell. Safety Meriplast is not toxic when degraded in farmland soil. It does not burn in normal atmospheric conditions: it has a limited oxygen index (LOI) above 21% (22 and 26% for Meriplast N60 and N50 respectively). A novel flexible and elastic biomaterial Meriplast is a novel bioplastic entirely made from raw materials derived from agriculture and is fully biodegradable. This material has specific flexibility and elasticity properties, which makes it unique amongst the biodegradable and renewable materials currently available. Meriplast is fully bio-based, it is both renewable and biodegradable. Applications The targeted applications of Meriplast are moulded objects for interior such as toys, leather imitation for office products (covers), design articles, pieces of furniture. Applications are still in the development phase. Processability Meriplast can be processed on standard rubber processing machinery (injection moulding, calandering). The range Different grades that vary in extensibility and tensile strength can be produced. The material s natural colour is light brown but it can be coloured into a wide variety of tints. Meriplast life cycle Agricultural production wheat Bio-ethanol coproduct Tereos Syral patented process coproduct oilseeds Bio-diesel Meriplast Figure 1: The natural colour of Meriplast is light brown. biodegradation 100% Figure 2: Prototypes of finished products made of Meriplast

3 Mechanical properties The mechanical properties of Meriplast are similar to elastic materials such as natural rubber or thermoplastic elastomers up to 100% elongation. Ultimate tensile strength and elongation are however lower (Table 2). Table 2: Physical and mechanical properties of Meriplast Physical and mechanical properties Density Hardness Strength at 100% (Shore A-15 ) d elongation a Strength at break (MPa) a a According to ISO type 5A, b Rubber Technology, Compounding and Testing for performance By John S. Dick Hanser, c Technical data sheet from API, d ASTM D 2240 Elongation at break (%) a Meriplast N Meriplast N Natural rubber (thread) b API (TPE from APINAT) c Figure 6: Relaxation test for Meriplast N60 at extension ratio of 100% Tensile modulus E (Pa) 1,E+07 1,E+06 trend line: slope = ,E time (s) Figure 7: Residual elongation of Meriplast N60 after relaxation test 100 A visco-elastic behaviour Meriplast exhibits a complex visco-elastic behaviour with dominant elastic features, as demonstrated by relaxation tests (Figure 6). The figure shows changes in the tensile modulus over time under a constant extension ratio of 100 %. The behaviour of the material is in between a purely elastic and a purely viscous material: the linear decrease on a double logarithmic plot has a slope of -0.13, compared to 0 for a purely elastic material and 1 for a purely viscous material. Moreover, Meriplast displays a unique, slow elasticity as shown by measures of residual elongation of the samples after removal from the testing machine (Figure 7). For example, after stretching the material to an elongation of 100% for 1h, the material retracts to 30% of its initial length after 30 minutes and to 4% after 7 days. Residual elongation (%) Release time (min)

4 Slow relaxation and resilience of Meriplast also influence response to compression, which is different from that of rubber. Meriplast N50 has a compression set value of 65% after a release time of 30 min, compared to 10% for natural rubber and 30% for SBR rubber. However, after a prolonged release time of 7 days, the material almost retrieves its original shape (Table 3). Table 3: Compression set value (%) (ASTM D395 Method B type 1 for 24hr at 25 C) 1,E+07 compression time at 25 C Meriplast N50 1 hour ,E <1 1 week trend line: slope = Mechanical response to variations of humidity and temperature Increasing temperature or humidity causes plastification of Meriplast, hence decreasing elastic modulus. Under standard ambient conditions (50% relative humidity and 25 C), the material has a moisture content of approximately 11% and a stress at break of 4.3 MPa. At a relative humidity of 70%, moisture content increases to 24% and stress at break decreases to 1.6 MPa (Figure 8). This is reversible when the material is put back to the initial conditions. Meriplast is not designed for prolonged immersion in water. As an example, after a 24-hour immersion in water, the material adsorbs up to 1.5 times its own weight. Drying of the swollen material will result in the loss of mechanical properties in terms of flexibility and elasticity. Temperature affects mechanical properties of Meriplast in a steady way, with no sharp transitions. Dynamic mechanical thermal analysis shows that the material has a transition from glassy state (at -100 C) towards a rubbery state plateau (at 100 C), which occurs over a very broad range of about 200 C (Figure 9). For natural rubber, this transition typically occurs over 40 to 60 C. That makes Meriplast unique amongst elastic materials. Modulus (Pa) Tensile modulus E (Pa) 1,E+05 Stress at break (MPa) Residual elongation (%) 1,00E Storage Modulus 1,00E+09 1,00E+08 1,00E+07 1,00E+06 1,00E Figure 8: Influence of relative humidity on stress at break ,35 0,30 Loss Modulus 1 0, Release time (min) 0,20 Tan delta time (s) Meriplast N60 after 30 min release after 7 days release after 30 min release after 7 days release 1 day <1 2 days Relative humidity (%) Figure 9: Dynamic moduli (Storage Modulus, Loss Modulus and Tan Delta) as a function of the temperature for Meriplast N60 0,15 0,10 0,05 Tan Delta 1,00E Temperature ( C) 0,00

5 Packaging and storage Meriplast is available in 15 kg reels with endless strands of mm diameter (Figure 3). Different packaging is available on request. The product should be stored in a cool, dry place with good ventilation. Figure 3: Meriplast packaging Processing conditions Figure 4: Equipment used for testing Meriplast processing Conical frustum Meriplast is thermosetting and has a processing viscosity similar to uncured rubbers. Consequently, it can be shaped using traditional rubber injection technology, for example on REP machinery (REP International, Corbas, France) (Figure 4). Recommended temperature settings are 60 C in the extrusion section, 70 C in the injection chamber and C in the mould. Examples of moulded articles such as plates (120 x 120 x 2 mm) or conical frustums (60 and 47 mm for the diameters, 25 mm height) are shown in Figure 5. Typical mould shrinkage is 2.5%, as determined with a calibrated plate mould. Table 1: Optimal processing conditions for two moulded objects Two plates obtained with one injection: one being injected in parallel and the other one by one point Figure 5: Examples of moulded articles Moulding temperature ( C) Moulding time (min) Plate Conical frustum Product stability and degradation Similarly to other natural materials such as leather or wood, Meriplast adsorbs water but it is not soluble in water. Prolonged contact with water (e.g. dishwasher) should be avoided. Meriplast shows full degradation after 36 days in aerobic fermentation (according to ISO based on the modified Sturm test) and 50 days in farmland soil. Meriplast and its degradation metabolites are not toxic as tested by microbial inhibition tests. ISO 14852: Determination of the ultimate aerobic biodegradability of plastic materials in an aqueous medium - Method by analysis of evolved carbon dioxide Domenek S., Feuilloley P., Gratraud J., Morel M.H., Guilbert S. (2004) Biodegradability of wheat gluten based bioplastics Chemosphere 54:

6 The company Tereos Syral is the 3 rd European starch producer and is the starch activity of the international agro-industrial group Tereos. Tereos Syral transforms 3 million tons of wheat and corn in its 6 European factories into 1,800,000 tons of starch and starchbased products, 180,000 m 3 of alcohol and bioethanol, 200,000 tons of vegetable proteins, and by-products for animal feed. The firm has 1,280 employees and has a pro forma yearly turnover of 1.2 billion. The success of starch products is linked to their versatility and to their renewable as well as biodegradable nature. Current starch manufactures can already be described as bio-refineries. Fibre, protein and starch from the cereals are separated by mostly mechanical means and further transformed in specific lines combining a wide range of technologies: enzymatic or chemical hydrolysis and modifications, hydrogenation, refining, fermentation, drying, crystallisation. Zone Industrielle et Portuaire F MARCKOLSHEIM Tel : +33 (0) Fax : + 33 (0) info-syral@tereos.com Tereos Syral received the special award of R&D for Meriplast at the Biowerkstoff-Kongress in Stuttgart in October Pictures credits: Patrick Bogner, shutterstock December 2011 The information mentioned herein remain the property of Tereos Syral or its contactors. Although Tereos Syral uses reasonable endeavours to ensure the accuracy and completeness of said information, Tereos Syral waives all liability in relation to their use by the addressee.