Introduction to Plastics Recycling, Second edition

6.10: Conclusion

6.10 Conclusion

An overview of the processes discussed in this chapter is given in Table 6.1. Whilst primary mechanical recycling will continue to be common practice amongst plastics processors, secondary recycling is subject to both practical and economic limits for use. Success depends primarily upon the economics of sorting to obtain single polymer materials, and knowledge of material provenance and degradation history. Processes adapted from conventional machinery to take more highly contaminated feedstock exist, however they are limited in application to wood replacement type profiles and panels and cannot overcome the inherent limitations in the make-up of their feedstock. Even these processes also generally require feedstock to have undergone some preliminary sorting. The next chapter will look at ways to upgrade recyclate materials in order to improve upon their properties for mechanical recycling applications.

Table 6.1: Comparison of processes

Process

Complexity of parts

Forming action

Mould

Plastic types

Tolerance to contaminants

Extrusion

Fairly simple profiles

Extrusion

None

Single

Low

Injection moulding

Complex

Injection

Closed

Single

Low

Co-injection moulding

Complex

Injection

Closed

Single layers

Low

Compression moulding

Simple

Compression

Closed

Single

Medium

Extrusion blow moulding

Complex

Inflation

Closed

Single

Very low

Multi-layer extrusion blow moulding

Complex

Inflation

Closed

Single layers

Very low

Injection blow moulding

Simple

Inflation

Closed

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