On 4-5 March 2020, Aimplas will host its seventh International Seminar on Biopolymers and Sustainable Composites in Valencia, Spain, with the aim of leading the discussion in new opportunities and challenges. Among the many high profile exhibitors, speakers and sponsors is specialty chemical producer WACKER CHEMIE AG. Dr Lada Bemert, Global Business Development Manager Biopolymers at WACKER CHEMIE AG, speaks to EPPM about the new VINNEX biopolymer additive.
Which qualities does the VINNEX additive possess that perhaps many of its bio-based predecessors do not?
VINNEX is an additive system for the formulation of bioplastics. By using the product, biopolyesters processing and property profile can be optimally adjusted. Another benefit is that VINNEX enables the various biopolyesters to be combined with each other and with starch, which substantially increases the range of applications and processing options of biopolyesters. Consequently, WACKER’s additives contribute to opening up new markets for bioplastics.
The biopolyesters that are currently readily available and can replace plastics produced using petrochemicals include polylactic acid (PLA) and polybutylene succinate (PBS). PLA is a brittle material and therefore has a tendency to shatter relatively easily. To prevent this, the formulations are often enhanced with additives to improve the impact strength. Typical applications in which this property is required range from children’s toys to packaging. A cost-effective additive for increased impact strength is provided by VINNEX 2504 and VINNEX 2505: the powder additives that are based on vinyl acetate-ethylene copolymers make the end product more elastic.
Another example is VINNEX 2526. It enables polylactic acid (PLA) based blown and cast films to be optimally processed which is essential for food packaging applications. The additive improves the melt strength, and thereby also the bubble stability during extrusion. It also enables the process temperature to be reduced by about 10 °C. By minimising the ‘necking’, i.e. the constriction of the melt film that is often observed in PLA and PBS, the improved melt strength results in optimum thickness distribution.
How difficult is the process of producing the VINNEX additives?
Depending on the desired features and application needs, VINNEX can be based on vinyl acetate-ethylene or polyvinyl-acetate and other monomers. The production of VINNEX additives based on vinyl acetate-ethylene is a high-pressure polymerisation process, which requires special knowhow and handling of components in different phase-conditions, liquid and gaseous phases. Polymerisation of polyvinyl-acetate-based VINNEX is also not a trivial process. Here, the molecular weight control and addition of other monomers are crucial for final product properties.
And how does it simplify traditional manufacturing processes such as IM or thermoforming?
VINNEX resins lower the melt viscosity and increase the melt strength of the biopolyester. This decreases injection time and improves the IM process. Furthermore, lower viscosity and higher strength of the melt allow defect free parts by thermoforming.
For example, the improved melt strength obtained by using VINNEX 2526 enables manufacturers to produce thermoformed blister packs with an optimal thickness distribution and transparency. Extremely good water-vapour permeability combined with high transparency makes a film made from PLA and VINNEX an ideal shrink wrap, for example, for fresh vegetables.
Another example is VINNEX 8880 which simplifies products manufactured in injection moulding applications and 3D printing. The additive optimises the flow properties of the polymer melts to make biopolyesters easier to process. Firstly, the low melt viscosity can be used to produce complex injection moulded items more easily. Secondly, it can increase the loading of fillers, such as cellulose fibre, starch or inorganic fillers. The improved flow characteristic also enables the process temperature to be reduced in 3D printing.
Is it likely to develop suitability for applications beyond packaging?
The applications of biopolyesters are already going far beyond packaging. PLA, for example, is used in various medical applications as medical yarn, implants and diverse devices, such as biodegradable screws, pins and plates. Additionally, biopolyesters modified with VINNEX can be used in the production of toys, automotive and electronic applications.
Recycling – particularly collection for recycling – is still proving difficult for many regions. How does VINNEX change that game, and what does it mean for Europe’s plastics recycling businesses?
Recycling of biopolyesters is currently a topic of research in the industry. First results for the possibility of mechanical and chemical recycling of PLA have been published recently. At the present, we have no evidence that VINNEX will affect the recycling process. With increasing awareness and demand for recycling, we will continue our research to contribute to recyclable biopolymer solutions.
