Re­cyc­ling & Re-Use Po­ten­tiale

Production and characterisation of wood-plastic composites (WPC) with a matrix of thermoplastic elastomer (TPE) for the production of wood-WPC composite structures.

Supervisor:

1. Supervisor:                  Prof. Dr.-Ing. Elmar Moritzer
2. Supervisor:                 Prof. Dr. rer. nat. Thomas Tröster
3. Practice partner:         Günter Voß, Klimaschutzmanager Stadt Lichtenau
4. Industry partners:   N.N.

Motivation

The material wood-plastic composites (WPC) has been an integral part of the plastics processing industry worldwide for years now. The composite is a combination of wood fibres and a plastic matrix. Through this symbiosis, improved haptic properties and increased weather resistance can be achieved. Basically, WPCs are extruded or injection moulded on the basis of a cost-effective thermoplastic matrix, such as polypropylene or polyethylene. Plastics can be divided into the subgroups thermoplastics, thermosets, elastomers and thermoplastic elastomers (TPE). TPEs combine elastomer-like properties with the processing characteristics of thermoplastics. Because of this, TPEs are very easy and inexpensive to process. The production of a WPC based on a thermoplastic elastomer (TPE) has only been researched to a very limited extent. [DiKr18, NEH04] describe the moulding of WPC based on a matrix of thermoplastic polyurethane (TPU, soft segments of polyester or polyether) or thermoplastic vulcanisates (TPV). To date, there is no known research on the injection moulding technology of WPC based on TPE. This research gap is to be closed in these research efforts so that a cost-effective and easily processable WPC with good optical, haptic and mechanical properties (damping behaviour) as well as increased recycling potential can be generated and made available to the plastics processing industry. 

Objective

The aim of the project is to develop a new material in the wood-plastic composite material class and to characterise the material properties for successful application in the injection moulding process. In particular, the flow behaviour of the wood fibre-reinforced, thermoplastic elastomer as well as the adjustment of the fibre length distribution can be determined as characteristic variables for a successful injection moulding process. Due to the high material recycling potential of the TPE and the wood fibres, a comprehensive investigation is to be carried out with regard to the recycling of wood fibres (especially chipboard or similar), TPE and WPC and the resulting influence on the product quality is to be quantified. In order to finally enable a composite structure for application in the furniture industry, automotive or sports industry (bicycle or Nordic walking stick handle), an extensive investigation of the surface characteristics is indispensable and should be a further pillar for the final development of a technology carrier.

Procedure / Methods:

For implementation, suitable TPE and fibre types are first evaluated and then compounded. During the compounding process, the thermoplastic elastomers are mixed with the fibres and granulated. The focus here is on the composition of the compound in terms of fibre content, the necessary adhesion promoter content and matrix content as well as the moisture content of the fibres. On the basis of the compound produced, the fibre is to be separated from the polymer component by means of a Soxhlet extraction and then a fibre length measurement is to be carried out. A further determination of thermodynamic, rheological and hygroscopic parameters is indispensable for the investigation of the injection moulding process. In particular, various process parameters are to be evaluated and corresponding filling studies carried out. By means of injection moulded shoulder rods, mechanical characteristic values with regard to stiffness and damping behaviour will be recorded as a function of the ageing condition or moisture content. To evaluate the material for application-oriented use, long-term abrasion tests are carried out and the topography is analysed. As a further aspect of the research efforts, the recycling potential of the materials will be investigated. For this purpose, all components (TPE, fibre material, WPC) will be regranulated and fed into the injection moulding process. The focus here is on the changed filling behaviour, the fibre distribution in the component and the mechanical characteristic values.

Literature