Influence of the Recycled Material Percentage on the Mechanical Behaviour of HDPE for Injection Moulding Process for an Ecologycal Design

Abstract

Nowadays plastic materials recycling aims most of the time to use the recycled material to manufacture products of less requirements than the original products, so the material is depreciated. It would be important to recycle plastic materials to use them for the same applications they were initially used. To make this possible it would be necessary to characterize the recycled material properties, design products taking into account that they are going to be produced with recycled material and to be able to recuperate the product at the end of its lifetime. An example of this designing philosophy is going to be presented in this work, applied to large trash containers produced with HDPE (RIGIDEX5740UA), where the product can be easily recovered at the end of its lifetime and also the amount of polymer material wasted during thermoplastic injection moulding is very high. Recycling mills convert parts into small pieces that are used as feed material for injection again, by mixing it in different percentages with raw material. This mixture of both raw and recycled material modifies material properties according to the percentage of recycled material introduced. Some of the properties affected by this modification are those related to mechanical behaviour. This paper analyzes the mechanical behaviour of material with different percentages of recycled material. Test parts have been injected with different percentage of recycled material and have been tested by a tensile machine. Results like; Stress at yield, Stress at break and Young Modulus have been calculated and analysed. The product of this work has been designed using only one plastic material, which is very helpful from the point of view of manufacturing and recycling. In these kinds of parts a very tight safety factor is used, thats why to know exactly material properties is very important during its design.