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issue 02/2021

  • Text
  • Balance
  • Moulding
  • Carbon
  • Recycling
  • Plastics
  • Sustainable
  • Products
  • Renewable
  • Biobased
  • Packaging
  • Materials
  • Bioplastics
Highlights: Injection Moulding Basics: Mass Balance

Injection Moulding

Injection Moulding PLA-WPC for injection moulding How to disrupt FMCG-Packaging with wood and biopolymers Using wood-based and fully renewable materials for fast-moving consumer goods (FMCG) to reduce fossilbased plastic consumption is the vision that drives the team behind forewood. For this purpose, they have developed a technology that enables WPC to be injection moulded into thin-walled, complex packaging applications. Wood-plastic composites, better known as WPC, is a wellknown class of materials for various purposes. In their first generation, they are used to manufacture extrusion profiles, such as decking or window frames. Further developments enable the use of WPC in injection moulding for large parts, such as furniture. The original idea for WPC was primarily based on economic considerations: non-cutting processing makes it possible to manufacture products with a wooden look much more cost-effectively. Accordingly, WPC products were comparatively simple and did not need to meet any special technical requirements. With the growing interest in sustainability and environmental protection, the material class WPC is also experiencing a revival. With the use of wood flour as a filler, it is already possible to partially replace fossil resources with renewable raw materials without compromising the known properties. The upcoming generation of WPC combines technical wood fibres with bioplastics to generate up to 100 % biobased materials. Forewood uses wood fibres embedded in a polymer matrix fully made of biopolymers, such as polylactic acid (PLA). Using wood fibres instead of wood flour improves the mechanical properties of the composite. The completely biobased and biodegradable material consists of more than 50 % wood and is suitable for producing everyday products via injection moulding. However, the successful processing of forewood in injection moulding is significantly more challenging than conventional plastics. The fundamental challenge in processing WPC lies in the contrasting properties of the two materials it contains. While wood is subject to thermal decomposition at high temperatures, sufficiently high temperatures are necessary for the melting process of the involved polymer. This trade-off results in a narrow processing window for forewood. There is a sweet spot of process stability that requires a high level of control over all processes involved. Processing temperatures must be relatively low to produce high-quality products. Otherwise, the appearance and the mechanical properties of the product suffer, as the wood fibres’ advantages get lost through thermal decomposition. Too high processing temperatures also result in organoleptic changes to the material. In addition to the injection moulding process, the accompanying process steps are also specially designed for forewood. The hydrophilic wood fibres require appropriate pre-treatment to ensure a low residual moisture content. The abrasive effect of the wood fibres influences the design of the mould and injection unit. The selection and control of these parameters and the overall process coordination are crucial for high product quality. With the rezemo wooden coffee capsule launched in 2018, the basic feasibility, marketability, and customer acceptance of FMCG made from forewood was proven. In this lighthouse project, forewood fulfils several specific requirements. The material complies with the food standard according to EU No. 10/2011, has very good sealing properties, and a sufficient barrier against oxygen. Permeation tests show that a coffee shelf life of more than nine months is feasible. Due to the wood fibres, higher stiffness and thermal stability are achievable with forewood compared to pure PLA. As a result, high strengths can be achieved even with low layer thicknesses. In concrete terms: 20 bioplastics MAGAZINE [02/21] Vol. 16

By: Janina Jarothe Research & Sustainability rezemo GmbH Waiblingen, Germany layer thicknesses of less than 500 µm are possible without any problems. Coffee capsules are massproduced with high throughput. Accordingly, production must occur in economically attractive conditions. In the FMCG sector, material costs account for a large proportion of manufacturing costs. Forewood’s competitive price enables these products to get manufactured economically. Furthermore, the reproducible high quality of the wooden coffee capsules is crucial, as it is a product that is visible to the customer. Using forewood enhances the value of the product, especially regarding its look and feel. COMPEO Leading compounding technology for heat- and shear-sensitive plastics Injection Moulding The development know-how gained from the wooden coffee capsule is the basis for developing further FMCG and similar products from forewood. With the experience gained, it is possible to realise thin-walled and complex products using injection moulding. The 100 % biobased materials make it possible to fully avoid the use of fossil resources. Using forewood also promotes a circular economy: Organic recycling i.e., industrial composting closes the loop, while material recycling works only in a few cases. Forewood’s potential application areas are diverse and range from packaging for food or cosmetics to the agricultural industry. It is suitable for anyone who wants a sustainable product without compromising on high quality. Forewood is a brand of rezemo GmbH that is located near Stuttgart, Germany. The team develops, designs, manufactures, and sells 100 % biobased packaging for everyday consumer products to enable environmentally friendly consumption and drive the Green New Deal. They cover the entire value chain to realise sustainable products and make a decisive contribution to protect our earth. Uniquely efficient. Incredibly versatile. Amazingly flexible. With its new COMPEO Kneader series, BUSS continues to offer continuous compounding solutions that set the standard for heat- and shear-sensitive applications, in all industries, including for biopolymers. • Moderate, uniform shear rates • Extremely low temperature profile • Efficient injection of liquid components • Precise temperature control • High filler loadings bioplastics MAGAZINE [02/21] Vol. 16 21

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