Thermoplastics recycling

Thermoplastics can be remelted and reused, though the purity of the material tends to degrade with each reuse cycle. There are also methods by which plastics can be broken back down to a feedstock state in order to facilitate their reuse, mixed with untouched material. To assist recycling of disposable items, some schemes have been devised to mark components by plastic type, but recycling has proven difficult. The biggest problem with plastics recycling is that it is difficult to automate the sorting of plastic waste, comparing to other recyclable materials, such as metals, that are easier to process mechanically. Developments are, however, taking place in the field of active disassembly, which may result in more consumer product components being re-used or recycled. Currently, the percentage of plastics recycled is very small, somewhere around 5%, but smarter design and increased awareness among users are leading an important improvement towards a more rational disposal of thermoplastics.

Thermosets Recycling

Although an intese research activity is going on in order to improve the current thermosets recycling processes, some very well known procedures like re-use/repair, degradation, pyrolysis, and incineration already permit an effective recycling of these materials.

Even if thermoset compounds cannot be remoulded like pure thermoplastics, they present the advantage of being very durable, in spite of the frequent use in applications where they are exposed to tough enviroments.

Recycling thermosets is a process that involves, as first step, the breaking up of mouldings by granulation and grinding, to reduce them to particle sizes. Once shattered, the material is commonly used as a form of filler into other compositions. When the combination enhance the qualities of the host material, the filler is defined as active, while when it is purely added in order to achieve a cost reduction, it is said to be inactive.

Degradation

Through processes like photodegradation, chemical degradation and biodegradation is possible to proceed to the reduction of plastics to lower molecular weight materials.

Pyrolysis

The use of thermal methods allows the breaking down of polymers into low molecular weight species that can be handled and treated much more easily. The materials thus obtained can actually be re-used: fillers can be separated promptly from fibres, and used as raw materials for new processes.

Incineration

Although incineration should be classed as disposal rather than recycling, the advantages of this process are linked to the energy recovery and the reduction of Carbon Monoxide and Sulphur Dioxide contents, with no increase in dioxins or furans.