MATERIALS AND APPLICATIONS |
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Film production with a laboratory extruder |
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BACKGROUND OF THE PCR PLUS PROJECT Recycled plastics can be divided into two macro-categories: post-consumer resins( PCRs), the result of separate packaging collection, and postindustrial resins( PIRs), i. e. industrial production scrap, processing residues and non-compliant items. PIRs generally include materials with welldefined characteristics and a composition that is often known, so that it is relatively easy to use them for applications similar to the original ones. On the contrary, PCRs are more complicated to handle as they are made up of different materials and often include specific active ingredients with different functions. On top of all this, PCRs come from packaging items with a defined lifecycle and are prone to aging and the accumulation of |
contaminants( e. g. residues of food, detergents, glues, dirt of various kinds). The PCRs collection and sorting chain is already doing a great job, bringing to the market selected grades with clear specifications. However, due to the inherent complexity of their management, we are still far from the massive replacement of virgin resins and a lot of work must still be done to improve products and processes.
PROJECT PLAN Such an ambitious project had to be organised in clear and defined steps with specific objectives and dedicated resources. However, already in the early stages, it was soon understood that the project could not lead to a single result, but that in order to handle a“ variable” material such as PCRs it would be necessary to investigate behaviour models and study modular solutions. In other words, the quality level achieved by plastics makes it possible for an operator in the sector to predict their behaviour on processing machines and to codify effective process settings aimed at obtaining maximum results. On the other hand, however, second-life plastics do not always fit this model. In fact, although their characteristics are absolutely in line with the original plastics, they contain chemical-physical elements that modify their behaviour in a variable way. In the face of this variability, and with the stated aim of studying solutions applicable on an industrial scale, Rifra drew up a project plan consisting of several steps:
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- I- Preliminary study on the state of the art of recycled resins and of the selection of raw materials, in terms of PCR resins and potentially interesting additives;
- II- Identification of the best analysis techniques( available at industrial laboratories) for material characterisation;
- III- Definition of a model of the behaviour of resins containing additives. The work is still ongoing, but we can share a summary of the results obtained so far.
STEP I The polyolefin-based PCRs can be divided into different subgroups according to the final application: PCRs for the film sector and PCRs for the moulding sector. Rifra decided to study both subgroups by analysing two of the best-selling resins currently available from the market: 1.“ Polymer A”, specific for the cast film sector: polyethylene( mainly LDPE) with small amounts of other polymers( mainly PP below the 10 % threshold). 2.“ Polymer B”, specific for the moulding sector: polyethylene( mainly LDPE) with a polypropylene content between 30 and 50 %. The physical and chemical properties of these resins have been studied in order to understand their characteristics.
STEP II Specific techniques have been used for studying the variability in the behaviour of polymers that
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Italian technology plast / April 2025 |
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www. plastmagazine. it |
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