One treatment method for plastic waste is mechanical recycling through an intrusion process, to produce plastic lumbers. The recycling of plastics into lumbers originates from the 1980’s, when Recycled Plastic Lumber (RPL) was introduced. The product is obtained by mixing post-industrial and post-consumer plastics with other materials into a substitute for concrete, wood and metals. The material has a similar resemblance of wood lumber and the product design often has the same sizes and shapes as in the lumber industry. RPL is mostly used for numerous outdoor applications, such as park furniture or decks as the material is particularly suitable for applications where there is contact with water and soil, as plastic lumbers are resistant to decay.
However, the functionality of traditional RPL has so far been limited. The material is made from scrap of plastic waste from the technical waste treatment process of plastics recycling, where there are a variety of different polymers present. The low level of compatibility of these polymers combined with the contamination by non-polymeric materials such as paper results in a material with poor mechanical properties. To obtain sufficient stiffness in the end-products, there is often a need to create over-dimensioned beams which implies heavy products with low mechanical properties.
Introducing an adjusted form of the conventional process where plastics are made into RPL, the project PROWASTE has managed to create a material which results in products with higher quality and performances. The innovative aspect of the new method is the production of high performance plastic beams, reinforced by fiberglass pultruded rods. The parameters for the production process and the equipment needed for the production of recycled plastic lumbers reinforced with rods have been defined during industrialization activities carried out by the partners of the project. The rods are introduced in the plastic matrix during the extrusion phase in the production cycle, and the method doesn’t require any substantial modification of the conventional production plant used for moulding plastic lumber. Compared to the unreinforced plastic lumber, the flexural properties increase by a factor of 3.
This three-year project started in 2010 and is funded through the European Commission
CIP programme, a grant funding programme. The major results from the project are the implementation of a faster system to insert rods in the plastic beams, and the definition of a plastic mixture that optimizes the strength of the end-products. The reinforced plastic lumber are mostly used for applications within the urban and outdoor furniture market, for railway ties or deadening panels for railways and highways, pallets, decks, outdoor flooring or in poles for agricultural uses. At the moment, the system is operative at the plant of one of the project partners, and the technology readiness level is thus estimated to reach a level 8 on the TRL scale, according to the scope of CIP, which provides public grant funding for demonstration. However, the project team, coordinated by the Centre for planning, design and technology of materials in Italy, is continuously working on improvements of the technology.