1 Februar 2021

Plastics for a green future: Bio-based semi-finished SMC products

Two companies worked together to develop a weight-reduced semi-finished product based on renewable raw materials of organic origin

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Lorenz Kunststofftechnik GmbH works in semi-finished product manufacture, research and development, customer- and component-specific material development, and thermoset plastic recycling. It has special expertise in the production of SMC and BMC thermosets. © Lorenz Kunststofftechnik GmbH

Lorenz Kunststofftechnik GmbH and the Institut für Verbundwerkstoffe (IVW) report the successful development of a lightweight thermoset based on renewable and regional raw materials.

The ecological footprint of plastics and their energy-intensive production has long been subject of public criticism. An increasing amount of research has been ongoing, focussed on the development of environmentally-friendly alternatives – organic plastics – to improve their CO2 balance.

Among these efforts were those of  Lorenz Kunststofftechnik GmbH and the Institut für Verbundwerkstoffe (IVW), who, from 2018 to 2020, worked to find ways to make a thermoset composite with a lower CO2 footprint. The result is a weight-reduced semi-finished product based on renewable raw materials of organic origin. The reduction in density gives this new semi-finished product possibilities for use as a lightweight material in fields like automotive manufacture, e-mobility and infrastructure construction. To improve the ecological balance, the company decided to source raw materials regionally within 500 km in the pending commercialization of the project results. This sustainable plastic is flame-proof to UL 94 V0 4 mm HB and mold-resistant. The research project received financial support from the Federal Ministry of Economics and Technology (BMWi) as a ZIM subsidy (Central Innovation Program for SMEs).

The first ideas for environment-friendly polymers started making the rounds at Lorenz Kunststofftechnik GmbH after the UN Climate Conference in Paris in 2015. The company, which specializes in thermosets, looked for a suitable research partner and in 2018 found one in the Institut für Verbundwerkstoffe (IVW) in Kaiserslautern.

“In earlier projects we had already provided IVW with semi-finished products, so we could build on a good and effective relationship,” said Peter Ooms, director of Sales and Business Development at Lorenz Kunststofftechnik GmbH. “In the current research project, we assisted the IVW with our expertise and SMC materials, as well as in the subsequent testing for industrial production. The Kaiserslautern institute did the lab-scale preliminary testing, general research and the development of the formulations for the new organic SMC.”

Analysis of the required parameters

As the first step, Lorenz and the IVW jointly drew up a material specification sheet. To do so, they asked some 30 companies in various industries who might be interested in such a thermoset, including specialists in electrical, automotive, and industrial manufacture.

“Our survey showed that different industries have different requirements for the material. However, almost all wanted it to have a life-cycle assessment (LCA) to document environmental aspects and CO2 reduction in production, as well as recyclability. One approach to this is the research into sustainable fillers, fibers and resins for the manufacture of semi-finished BMCs and SMCs,” adds Ooms. “We chose the possible organic materials for SMC production based on these requirements.” A number of organic-based lightweight fillers and fibers were shortlisted, for example ground sunflower seed shells and reeds.

In the next phase of the project the IVW prepared the characterization and lab-scale production of the organic-based SMC. “First we did initial tests with various lightweight fillers and fibers,” explains Dr.-Ing. Florian Gortner, a scientist at the IVW who works on processing techniques. “Based on the results we analyzed all the necessary parameters and examined which materials would be especially suitable.” The data obtained included impregnability, density, viscosity, and the availability of the respective raw material.

Characterization and manufacture of a partially organic semi-finished product

Once a basic understanding of the formulation and the interactions among its components had been worked out, in the next work step a demonstrator was defined.

“This demonstrator, in the form of a component with obstacles, helped us examine the flow and mold filling behavior of the material, and compare it with conventional SMC semi-finished products. Building on these results and on press rheometry testing, we built a simulation model to demonstrate the flow behavior and enable predictions about other mold geometries,” explains Gortner. “That made the support from the SMC experts at Lorenz so invaluable, and without it our progress in development would not have been possible.”

The subsequent primary goal was the comparability of the available SMC semi-finished products, and the creation of a solid basis for further test series. This comparability was demonstrated in producibility and workability with conventional equipment and processes, and in selected mechanical properties.

After all the specifications were clarified in cooperation with materials suppliers, SMC experts and vendors, and through extensive research of the literature, the initial development of an SMC resin paste based on conventional fillers began.

“As a starting point for the research project, we chose a UP resin and the appropriate anti-shrinkage additive to understand the basis of SMC formulation development,” says Gortner. “Magnesium oxide and an internal release agent were used to thicken the resin, and a color paste was added to color the semi-finished products. Working from the survey results, we added further additives and adapted the resin paste to the application.”

The challenge at this stage of the project was to get a basic understanding of the interactions of the individual components of an SMC formulation. After iterative test series for different resin systems, largely organic-based formulations were developed that showed the desired viscosity, flow, and impregnation behavior. These formulations were comparable to formulations on the market, given similar fiber mass content.

Industrial-scale use

In this way, a semi-finished product was developed that has lower density than conventional SMC. This makes it especially suitable as a lightweight material for electric vehicles, and so Lorenz intends to produce it for industrial manufacture. “Now that together with IVW we have succeeded in making this new thermoset, we’re planning further improvements for practical applications,” says Ooms in conclusion. “As it goes into regular use, we will doubtless get further useful feedback for changing certain elements in the formulation or for tuning individual parameters for specific applications.”

One such improvement might consist of varying the amount of resin paste with the other materials, or the amount of natural fibers. This makes it possible to create a semi-finished product with the ideal density and mechanical properties for each application. Unsaturated polyester resins could also be replaced, to reduce environmental impact as well as to reduce or even eliminate the health risks of daily work with polymers.

“The objective of our research project was to show that the use of organic-based components in semi-finished thermoset products is possible,” summarizes Gortner. “Thanks to the active support of Lorenz, we were able to do this successfully, and will continue to incorporate feedback from industrial production into our results.”

Lorenz and the IVW expect that this will lead to further development and improvement of semi-finished products with organic-based components.

Source: Bioplastics MAGAZINE, 2021-01-22.

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