From Tree to Structural Foam
BioEconomy Develops Sustainable Plastics from Biomaterials
Numerous products of our everyday life are based on crude oil. However, this resource is exhaustible. In order to satisfy industrial demand in the long run, and, at the same time, to avoid harm to the climate, it is crucial to find alternatives based on renewable resources that will be suited to replace fossil raw materials in the future.
In the »Effimat« research project, which has recently been concluded, six partners worked together on such a solution: the Fraunhofer IMWS, the Fraunhofer Center for Chemical-Biotechnological Processes (CBP), and the enterprises Miltitz Aromatics, Hennecke Polyurethane Technology, BARiT Kunstharz und Belagstechnik, as well as ö_Konzept. Their research efforts were aimed at developing biopolymers for floorings and foams, in addition to the respective processing techniques. These types of products are produced on a crude oil basis, at present. The researchers were successful in generating them from tall oil, which is obtained as a by-product when producing wood pulp.
Tall Oil as a Starting Point
The cluster project was funded by the Federal Minister of Education and Research, and its approach was the holistic use of wood as a raw material. The efforts undertaken by the enterprises and research institutes working together on the project were aimed at finding new types of alternative materials that are suited to replace conventional materials thanks to their similar or even entirely new properties. The starting point was tall oil, which can serve to produce high-quality reactive resin systems, after treatment in different synthetic compounding stages. Together with a curing agent, they can be made into very rigid plastic materials, suitable for, e.g. construction applications.
A new approach in the area of bio-based plastics was the combination of tall oil with a cold-curing agent. By returning the by-product of tall oil into the production cycle, another step of material use could be established along the wood utilization cascade, thus stepping up the potential of value creation.
Testing Special High-Pressure Foaming Process
In order to manufacture, on an industrial scale, semi-finished foamed products on a tall oil basis, the project partners also developed a special high-pressure foaming process. Applying this process, a special mixing head feeds the resin mixture into a corresponding cavity, where it is foamed by an expanding gas propellant. For this process, first, high-quality resin mixtures had to be generated, and a suitable anhydride hardener developed.
In comprehensive material test that followed, numerous combinations of materials and curing agents were characterized in terms of properties, and several compounds and structural foams produced at laboratory scale. Based on these test results, the researchers were able, in a parallel process, to investigate foaming of the resin mixtures at industrial scale, as well as practical application in bio-resin-bonded floorings. In the framework of the investigations, the Fraunhofer IMWS produced compound and foam materials for industrial applications, and characterized them in terms of mechanics, thermomechanics and morphology.
While working on the project, sophisticated resin systems were developed for a wide range of applications, which can be modified to suit the respective requirement and processing technique. "The benefits included in these novel resin systems are not only due to the biogenous origin of the primary materials. Another favorable aspect is the fact that production is more energy efficient, generally speaking, because structural foams based on vegetable oil cure faster at low temperatures, when processed", explains Nicole Eversmann, project leader at Fraunhofer IMWS. Plastics based on vegetable oil mainly serve for niche products at present, i.e. (protective) packagings or bicycle helmets. Moreover, this class of materials is suitable for applications in construction and cabinetry.