The Problem of Waste Plastic Mechanical Recycling and its Solution

4 The Problem of Waste Plastic Mechanical Recycling and its Solution 

During the manufacture of polymer-polymer composites, the amorphous-crystalline structure of the constituents can also be problematic. It is well known that polymers are polymorphic materials therefore, they can undergo many different crystalline and amorphous modifications. It is characteristic of plastic that the physical and chemical properties of these modifications can differ significantly. The main difference among the polymorph modifications is that they are stable at different temperature and pressure ranges, and they are interconvertible. 

Therefore, in many cases, the main research objective is how to improve the properties of one - usually widely available and cheap - plastic material by the addition of another plastic. The most common examples of these are PE-PA, PP-PA, PE-PET, PE-ABS and so on, e.g., recycled PET and HDPE composites were prepared with different proportions of raw materials in the work of Avila and co-workers. It was found that changes in the ratio of raw materials significantly influenced the characteristics of the composites. The properties of the final products could also be improved by the application of compatibilisers however, the tensile strength of the composites was typically below 30 MPa [24]. 

5 Improving the Properties of Polymer Blends using Compatibilisers 

As previously described, polymer-polymer blends with enhanced properties can only be manufactured using selected plastics as constituents. This means that in most cases, only polymers with similar physical and chemical properties can be blended without the formation of immiscible phases, e.g., PE with PP, various PA and PS with ABS. In instances when it is difficult to implement, in order to achieve better interfacial properties it is necessary to modify the surface of the constituents of the polymer blends [9-11,16, 21-23, 32-53]. 

---