MATERIALS | THERMOPLASTIC ELASTOMERS
Above: Innovative processing of cast polyurethanes: new mining screens are manufactured by Autox for the first time by injection moulding from the prepolymer Adiprene LF
as weight-saving fillers in various ‘hard’ thermoplastics, but our new lightweight technology is using them in TPEs for the first time,” says Martina Hetterich, Project Manager Advance Development at Kraiburg TPE. Zylog ElastoComp, India’s oldest TPE compounder, has also been working on lightweighting for automotive. It has developed a range of high-flow compounds for injection moulding of large and flexible parts. It says it is responding to demand for higher productivity and simpler tools than are required when using more viscous TPEs, which it says hinder the development of large aesthetic parts because of the problems they give with flow marks, streaks, flash, and shiny patches on visible surfaces. Neoflex 8150-02, a styrenic TPE, has a flow rate
of over 1,500g/10 min at 190°C (10kg). “Working closely with a processor and OEM, we formulated this high flow material, which allowed processing a 6ft [1.83m] long part, free from aesthetic issues, at lower pressure and shorter cycle time,” says Zylog director Aschak Damani. “The criticality of the formulation is to ensure homogeneity of the compound, optimised die swell and no phase separation during injection moulding.” Damani adds that the formulation is designed to enable post-moulding operations such as welding and bonding, while complying with automotive OEM requirements of low odour, low fogging, weatherability, chemical and heat resistance and light weighting. Its density is 0.89 g/cm3 The range includes grades for various
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applications, including over-moulded instrument panels, door trims, consoles, parcel shelves, boot mats, boot trims, large exterior step mats and underbody shields. Last year, Lanxess announced that its Adiprene
48 INJECTION WORLD | May 2020
C930 castable urethane low free-MDI prepolymer (originally developed by Chemtura, acquired by Lanxess in 2017) had been proven as an appropriate material for injection moulding as well. Korean company Autox developed a production process that allows cast polyurethane to be injection moulded. “This innovation brings a new perspective to the cast polyurethane world as it combines the processing advantages of injection moulding along with the properties of cast urethane,” says Lanxess. Autox produces a new vibrating screen for the mining industry which is made from this material. Compared with the casting process, injection moulding has a notably higher production output rate. Cost efficiency is also influenced by lower labour costs. Lanxess says the current production time of an injection moulded mesh screen is 5 min, while the pour casting process will normally take 35 min. “Adiprene LF (Low Free) prepolymer delivers improved industrial hygiene, along with ease of processing,” Lanxess adds. “It offers a perfect fit with the injection moulding process, as the viscosity is lower than of a conventional prepolymer.” Lanxess says Autox’s new development means
complex shaped parts are easier to mould as the pressure needed for the injection allows the flow to get into the part details. “The injection process answers one of the main concerns of the industry: waste management, as it also allows for better quality consistency, leading to less trimmings but also less waste from reduced scrap,” the company says. The Adiprene C930 mining screen offers
“outstanding” abrasion resistance and rebounding properties, improving the lifetime and screening efficiency of the part. Results of this caprolactone- based technology have been supported by field testing, which has shown that the lifetime of the screen can be up to three times longer than the market high-quality reference. Lanxess says it and Autox, which normally specialises in rubber spare parts for construction equipment, are confident that other applications can also benefit from this development. A third major TPU producer, Covestro, announced in early May that it will co-operate with independent compounder Teknor Apex on compounding materials based on Covestro’s Desmopan polymers. Thorsten Dreier, the new global head of the TPU business at Covestro, says the two companies together “want to develop customised products to grow together with our existing and new customers.”
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IMAGE: LANXESS
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