TABLE OF CONTENTS The majority of the factors to be considered in processing are the same for recycled HDPE and virgin HDPE. Other materials are not blow moulded in volumes that are finding their way into the recycling stream. HDPE in a variety of grades, especially for blow moulding is the largest volume plastic available. The items to be considered most in handling the recycled material is that chips or flakes will flow differently to pellets. This will cause a problem in both the initial feed area due to more chance of bridging at the extruder inlet. The presence of fines in the flake increases this situation. Determination of the amount of fines is often a very important specification to have in order to evaluate the potential for this type of problem.
The problem of optimising the concentration level of the recycled HDPE to the virgin HDPE in a given application centres on the long-term property requirements, as well as, the short term properties. Exposure of test bars of the material to accelerated or natural UV radiation is necessary to establish the long-term toughness of the material and compare it to the initial value for the HDPE. This will ensure the selected material ratio will meet the short-term and long-term requirements for the product.
The same procedure would be duplicated for any recycled plastic material. Blending virgin and recycled material together requires a determination of which blend will meet the specifications that are normally applied...
