recommendations for transformation
In this case, the recommendations for transformation through injection and extrusion will be the same as regards as the temperature, any possible drying, pressures, etc. It will also be possible to use the existing technologies for modification of properties (masterbatches, colorants, etc.). The manufacturing of products using the materials from this category will thus be simplified.
In case of bioplastics that possess new chemical structures, each one will have its own specificities in the same manner as traditional polymers. For the most part, these materials are biodegradable and thus require special care as regards the presence of moisture and the temperatures used.
These biodegradable plastics are polyesters, which are by definition sensitive to hydrolysis. The transformation temperatures used for these materials for injection and extrusion (between 130 °C and 200 °C approximately) actually make this typical reaction of degradation of polyesters very quick and potentially large. This reaction is thus even easier since their biodegradability makes these materials sensitive to it. Thus, these polymers need to be effectively dried, and sometimes the use of a desiccator is needed.
Similarly, they are often sensitive to heat exposure, even without the presence of water. In the procedures during which the stagnation phases may be long (typically in injection moulding), it is not uncommon to observe thermal degradation of the materials when the cycle times are too long. Thus it is necessary to take into account these phenomena while choosing materials, equipment, and the resources to be used in order to avoid them (using additives, etc.)
To summarise, bioplastic may generally be used with traditional transformation equipment without major modifications and are primarily used for the following equipments :
- Extrusion of films, tubes, sections, etc.
- Blowing hollow bodies (extrusion and injection)
- Injection moulding