BIOPLASTICS | TECHNOLOGY


PLA using mixtures of lactic acid oligomers (OLAs). These can have either a terminal carboxyl group or free hydroxyl group, with one or both being blocked by esterification. Fiori says the torque curve – which reflects the plasticising power of the product – for different PLAs plasticised with different OLAs (branded Glyplast by the company) are very similar to those obtained with PLA plasti- cised with a polyadipate or diethylhexyl adipate.


Films containing 20% Glyplast OLA have a glass


transition temperature (Tg) that is suitable for commercial use, Fiori says. “The thin, flexible PLA films obtained, in addition to offering notable advantages in the food industry, show mechanical characteristics similar to those of flexible thin films of PVC or polyethylene, but with the ecological advantage that it is degradable in the same or at a higher speed than that of soft plant tissue under equal conditions.” Currently, Condensia offers a series of additives obtained from bio-renewable raw materials and that are fully biodegradable and compostable (ISO 20200). When used in mixtures with PLA, they make it possible to obtain stretch films with good mechanical properties (Figure 1) without loss of transparency. Furthermore, the company says they can be used as impact strength modifiers, chain extenders, and nucleating agents.


PBS benefits Thailand’s PTT MCC Biochem, which is partly owned by Mitsubishi Chemical Corp, claims to be the only manufacturer of bio-based polybutylene succinate. The company says a key differentiator for its BioPBS product is its good biodegradability. It sees applications in single-use products, stationery, toys, and other products. It can also be used in compounding, where it can be combined with other bioplastics to improve biodegradability, as well as to enhance flow, flexibility and impact strength (Figure 2), heat stability and cycle time. The company says BioPBS is already used in


Figure 1: Stress-strain curves and sample mechanical properties of various PLA/OLA mixtures Source: Condensia Quimica


Figure 2: Effect on impact strength of addition of BioPBS to PLA Source: PTT MCC Biochem


26 COMPOUNDING WORLD | September 2019


unreinforced form in coffee capsules and dispos- able tableware. PTT MCC Biochem has also been working with Arctic Biomaterials on development of long and short-fibre reinforced compounds incorporating the Finnish company’s ABMcompos- ite technology, which is based on bioresorbable glass fibres. The fibres were originally developed for medical applications, but Arctic Biomaterials has since moved into technical applications as well. Arctic Biomaterials’ first venture into bio-based compounds involved the use of PLA. It has suc- ceeded in creating compounds with HDTs of around 155°C and modulus of well over 10,000 MPa. Sales and Marketing Director Tomi Kangas says the company has been involved in around 50 customer projects, some with major global brands. It also manufactures compounds based on other biopolymers, both reinforced and unreinforced and containing a number of bio-based additives. PTT MCC Biochem says its most recent success is the development of PLA-based compounds (that also contain PBS) that can resist temperatures of


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