Virtual technology day How biopolymers can be processed in hot runners

Editor: Alexander Stark

Germany — Never before has the plastics industry been as driven by sustainability as it is today. The increasing pressure from society and legislation demanding more sustainable alternatives is also driving Guenther hot runner technology. Therefore, the 1st Virtual Technology Day on 16 June 2021 was dedicated to the processing of biopolymers in the hot runner.

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Horst-Werner Bremmer, Head of Application Technology Consulting and Sales, moderated the lecture programme of the 1st Guenther Virtual Technology Day.
Horst-Werner Bremmer, Head of Application Technology Consulting and Sales, moderated the lecture programme of the 1st Guenther Virtual Technology Day.
(Source: Guenther)

Biopolymers are an attractive alternative to polymers and are increasingly becoming the focus of the plastics processing industry. However, their crystallisation behaviour makes processing these new materials difficult. This prompted Guenther Hotrunner to put together a programme of lectures on this topic for a virtual technology day. More than 160 registrations from a wide range of companies proved the interest in the possibilities in biopolymer processing.

Manuel Schmellenkamp from Sigmasoft opened the lecture programme of the online event with the topic “Processing biopolymers — How does simulation work?” Using the example of polylactide (PLA), which can be injection moulded as a blend and filled with natural fibres (for example, wood imitation), he demonstrated the benefits of simulation in all areas of the plastics processing value chain. PLA basically behaves like a thermoplastic during injection moulding, but the residual moisture has a greater effect on the mechanical and rheological behaviour. In addition, the process parameter is often narrower due to the strong temperature sensitivity. In the follow-up, Manuel Schmellenkamp described the properties needed for a simulation and simulated the influence of the viscosity parameters of PLA during injection moulding. He came to the conclusion that viscosity fluctuations do not influence the balancing, but mainly the pressure requirement. Therefore, the process parameters have a stronger influence on the balancing than the polymer properties, which is why the use of mould cavity pressure sensors is recommended. This was followed by a film about the design and production of a Blue Flow heater. During the breaks, the participants were able to discuss the presentations and ask questions and network in specially set up “zoom break-out” rooms.

Wolfgang Wieth from K.D. Feddersen described “Plastics in Transition” and addressed sustainable materials for technical applications. He began by highlighting the European Green Deal, the carbon footprint and the mass-balance method, before moving on to biobased and biodegradable bioplastics. The figures of the increasing global CO2 emissions and their polluters briefly caused astonishment, because only five percent of the emissions generated on the basis of crude oil can be traced back to plastics and of these again only one percent to technical plastics. Wolfgang Wieth then used various examples to demonstrate the increasing use of bio-based and biodegradable bioplastics in a wide range of industries.

The committed participation of online visitors made Guenther's 1st Virtual Technology Day a success.
The committed participation of online visitors made Guenther's 1st Virtual Technology Day a success.
(Source: Guenther)

A material made from natural raw materials

One example of how it is already possible to use resources efficiently is so-called paper injection moulding, which Niclas Beutler from Natur Compound introduced to the participants. Paper injection moulding is a mixed material consisting of natural raw materials, for example a combination of renewable raw materials such as cellulose and degradable raw materials such as chalk. The granulate is then produced by a blending process and the products are created quite conventionally by injection moulding. The properties of the granulate go hand in hand with a number of advantages. The products made in this way are 100 percent biodegradable and home compostable, which avoids disposal costs. Existing tools can be used for processing, which in turn reduces investment costs. Due to the similarity to conventional plastic, the application is familiar to the customer. The approved direct food contact also ensures a wide range of possible applications.

Jörg Essinger, Head of Application Technology & Service at Guenther, used the results from material tests with biopolymers in Guenther's technical centre to demonstrate the “processing of biopolymers with hot runner technology”. An excerpt from the company's application database with realised applications with biopolymers then also showed that both bio-based and biodegradable (compostable) plastics are being used more and more frequently.

The examples given included an egg cup made of the biomaterial Fibrolon, a PLA blend with wood fibres that is biodegradable. In this mould, a hot runner 5SMF30K with AHJ5 (202004670) from Guenther was used. The shot weight was 11.2 g per nozzle. The biomaterial was processed at a processing temperature of 150 °C to 200 °C and a mould temperature of 30 °C to 50 °C. The dwell time was very short. The dwell time was chosen very short to avoid thermal damage to the fibres. In another example, Jörg Essinger also discussed the processing of a biopolymer that consists of about 70 percent renewable raw material (cellulose) and 30 percent degradable raw material (chalk), i.e. paper injection moulding. In a video afterwards, the procedure for designing the optimum temperature curve in the tundish and the production of ideal channel holes were shown.

Christian Homp from Arburg dealt with “Efficient plastics processing”. His presentation focused on the challenges involved in processing bioplastics, such as screw geometry, injection moulding parameters, hot runner and drying. He emphasised the need for customers and end users to be particularly aware of this topic. As an example, he cited comparative material tests in the Arburg technical centre with fossil and alternative plastics. Following this, Jannes Wilke from Guenther's application technology department presented a joint project between the two companies in which a mask housing was produced from Terralene HD 4527 using a 4-cavity needle valve mould. The challenge was the small wall strength, which required a short injection time, and this with a very narrow process window. Jannes Wilke clearly described the selection of the appropriate nozzle type by means of filling and pressure loss calculations.

The participants of the Technology Day were able to see the application of this 4-fold mask filter tool in a virtual live demonstration on an Arburg machine. Bioplastics were processed on another Arburg machine. After a virtual company tour of the Guenther production facility, the online event of the Frankenberg hot runner specialists ended with a panel discussion with all the speakers. Guenther Managing Director Siegrid Sommer was impressed by the committed participation of the online visitors and, while not ruling out further virtual technology days, is looking forward to another real Technology Day in Frankenberg in 2023, as the company will also be celebrating its 40th anniversary in that year.

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