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From Science & Research

From Science & Research Fig. 4: Tensile properties of solid and microcellular PLA and PLA-HBP blends: (a) Specific toughness, (b) Strain–at–break, (c) Specific modulus, (d) Specific tensile strength. Solid Microcellular Specific Toughness [MPa/(Kg/m 3 )] Strain-at-break [%] Specific Modulus [MPa/(Kg/m 3 )] Specific Tensiles Strenght [MPa/(Kg/m 3 )] PLA PLA - 6% (H2004 + PA) PLA - 12% (H2004 + PA) PLA - 12% (H2004 + PA) -2% NC PLA - 12% (H20 + PA) PLA - 12% (H2004 + PA) 0 0.005 0.01 0.015 0.02 0 15 30 40 60 0 0.4 0.8 1.2 1.6 0 0.02 0.04 0.06 Fig. 3 shows the morphology of the solid and microcellular samples. The cell morphology of the microcellular foams showed that the addition of HBPs and nanoclay decreased the average cell size while increasing the cell density. Moreover, among all the solid and microcellular PLA–HBP blends, PLA–12%(H2004+PA)–2%nanoclay composites exhibited the highest specific toughness and strain-at-break followed by PLA–12%(H2004+PA) and PLA–6%(H2004+PA) (Fig. 4). On the other hand, PLA–12%(H20+PA) had a similar specific toughness and strainat-break values as the pure PLA for both solid and microcellular samples. Furthermore, the addition of HBPs+PA and HBP–nanoclay caused a slight reduction in specific modulus and a considerable reduction in specific strength compared with pure PLA in all solid and microcellular PLA–HBP blends. Overall, using SCF process, a weight reduction of 10–16% was achieved which testifies reduced materials consumption. Conclusions The advocacy of certain bioplastics specifically in areas currently dominated by conventional plastics will be realized only after sustained alleviation in the process and materials properties limitations of such bioplastics. In this regard, SCF assisted injection moulding technology plays a vital role specifically in lowering the viscosity of these bioplastics thereby lessening its processing temperature or widening the processing window, reducing the materials consumption through the development of low density foams without compromising on the specific materials properties, promoting the impact resistance of the materials, inducing stress-free and thus reduced warped parts, high throughout production, etc. Despite these extraordinary benefits, the science of SCF aided bioplastics is at a nascent state. Thus, significant innovations need to be created to pioneer and establish this technology within the commercial space. By: Srikanth Pilla* Clemson University, South Carolina, USA Shaoqin Gong University of Wisconsin-Madison, USA *: Corresponding author: References 1. J. Xu, Microcellular Injection Moulding, Chapter 1, p. 15, 2010. 2. N. P. Suh, Innovation in Polymer Processing, Ed. J. F. Stevenson, Chapter 3, p. 93, 1996. 3. J. Xu, and D. Pierick, J. Injection Moulding Technol., Vol. 5, p. 152, 2001. 4. D.F. Baldwin, N.P. Suh, SPE ANTEC Tech. Papers, Vol. p. 1503, 1992. 5. J.E. Martini, F.A. Waldman, N.P. Suh, SPE ANTEC Tech. Papers, Vol. 40, p. 674, 1982. 6. K.A. Seeler, V. Kumar, Cell. Polym., Vol. 38, p. 93, 1992. 7. S. Pilla, A. Kramschuster, J. Lee, S. Gong and L-S. Turng, J. Materials Sci., Vol. 45, p. 2732, 2010. Table-2: Injection-moulding conditions used to mould the tensile bars (S-Solid; M-Microcellular) Table-1: Percent composition of the materials compounded Experiment Sample PLA PA HBP Naugard-10 (0.2wt% total formulation) Naugard-524 (0.2wt% total formulation) Cloisite ® 30B 1 PLA 99.6 0.0 0 0.2 0.2 0 2 PLA-6%(H2004+PA) 93.6 1.5 4.5 0.2 0.2 0 3 PLA-12%(H2004+PA) 87.6 3.0 9.0 0.2 0.2 0 4 PLA-12%(H2004+PA)-2%NC 85.6 3.0 9.0 0.2 0.2 2 5 PLA-12%(H20+PA) 87.6 7.4 4.6 0.2 0.2 0 S M Mould Temp (ºC) 20 20 Nozzle Temp (ºC) 175 170 Injection Speed (cm 3 /sec) 20 20 Wt% SCF Content n/a 0.56 Pack Pressure (bar) 795 - Pack Time (sec) 7.5 - Screw Recovery Speed (RPM) 280 280 Cooling Time (sec) 35 35 Microcellular Process Pressure (bar) n/a 190 40 bioplastics MAGAZINE [03/14] Vol. 9

Materials he stars of today’s bioplastics industry are polymers like PLA or PBS. However, in a growth market like bioplastics, other substances are coming to market all the time. One such compound is 5-hydroxymethylfurfural (5-HMF), named by the US Department of Energy as one of the most versatile and promising renewable platform chemicals. Since February 2014, 5-HMF has been produced commercially by AVA Biochem, a Swiss-based company who recently developed a technological breakthrough in the continuous, automated and highly-scalable production of 5-HMF by means of modified hydrothermal carbonisation (HTC). Located in Switzerland, AVA Biochem’s plant produces 20 tonnes of 5-HMF per year, at purities of up to 99.9%. Currently, 5-HMF is being produced using fructose sourced in Europe. The modified HTC technology however, will allow for the use of several different biomass streams in the future, including waste biomass. The scale-up potential of the AVA Biochem process means bulk 5-HMF prices should be possible in the near future. If co-located with an efficient feedstock supply and at a suitable scale, 5-HMF could achieve cost parity with petro-based chemicals soon and therefore become cheaper to use in bioplastics applications. Capacity at the plant could be increased to 40 tonnes/year through process improvements and efficiency gains. Scale-up, together with bulk 5-HMF prices, will have significant consequences, opening new opportunities and potentially revolutionising the bioplastics industry. Renewable 5-HMF can already replace petrobased 5-HMF as a drop-in in many applications, such as adhesives used as plasticisers. One of the most promising routes is 2,5 furandicarboxylic acid (FDCA), produced as an intermediate when 5-HMF is oxidised. It can substitute terephthalic acid in polyester, especially polyethylene terephthalate (PET). Global PET output in 2009 was 49.2 million tonnes and PET fibre accounted for about two-thirds. PET for packaging and films accounted for 34%. Other increasingly significant markets are biopolyamides and resins, where 5-HMF derivatives caprolactam and 2,5-Bishydroxymethylfuran (2,5- BHF) play an important part. By conducting technical, lifecycle and market analyses, clearly defining end-product specifications and potential applications, the bio-based industries can help strengthen market pull for bioplastics. Application development done in conjunction with partners is also key to bringing more bioplastics technologies to market. Discussions between AVA Biochem and potential industry partners have begun and the company is optimistic that cooperation will help further develop the downstream chemistry pathways. The industrialscale production of 5-HMF has the potential to open the door to more innovative and highly interesting applications – in bioplastics and beyond. MT O HO Renewable 5-HMF Biobased platform chemical presents opportunities for bioplastics sector Figure 1: Production route for bio-based 5-HMF Figure 2: Potential applications for 5-HMF RO O O H 5-Alkoxymethylfurfural O O OH 2,5-Furandicarboxylic acid O HO O OH 5-Hydroxymethylfuroic acid HO O OH 5-Hydroxymethylfuroic acid N O H Caprolactam HO O 5-HMF O O O Caprolactone O H O O HO 1,6-Hexanediol O HO O O Bis(5-methylfurfurly)ether OH O Adipic acid O Levulinic acid O H O OH OH 2,5-Dimethylfuran bioplastics MAGAZINE [03/14] Vol. 9 41

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