Problem, solution, consequences18.05.2016
One of the key elements affecting the quality of obtained products and their mechanical properties or appearance is the skillful selection of conditions regarding processing of the plastic materials. The correct choice of extrusion parameters of polymeric materials requires knowledge of their properties, the temperatures at which they are plasticized without risk of degradation and their behavior under the influence of other factors. The individual elements of the plastic material extrusion line must allow obtaining products of desired shapes and sizes, and therefore it is important to know such phenomena regarding polymers as the Barus effect or different types of shrinkage.
The improper selection of processing parameters, as well as the inadequate design of individual components, entails significant negative consequences. Too low temperature of individual zones of the plasticizing system will not allow appropriate plasticizing of the plastic material that will generate large resistance during the process, and incorrectly chosen speed of screws may be associated with too short time of its presence in the unit and insufficient homogenization. Too aggressive conditions will cause degradation of the material, which in addition to visible surface defects, results in significant deterioration of mechanical properties of the product. The incorrect design of extruder elements, such as, e.g. a head, causes defects in the extruded profile - among others, subsidence. In addition, all the mentioned elements and the type of material influence the shape and dimensions of the extrusion. Only the correct conditions at any stage of the extrusion, allow obtaining a product with desired properties.
There are two main groups of polymers considering their physical structure, namely thermoplastic and chemo, and thermosetting, the so-called duroplastics. The main difference between these polymers is that thermoplastics unlike duroplastics are capable of going through multiple plastic state when heated to a suitable temperature, and therefore can be repeatedly processed.
Zamak Mercator successfully conducts a variety of testing for external companies, during which basing on the knowledge and experience of its staff and high processing capabilities of manufactured extruders, it selects the appropriate conditions for extrusion of plastic materials, even difficult in processing and gives the opportunity to receive high quality products. Zamak Mercator cooperates with Polish and foreign companies from a variety of industries, even as demanding as the aviation and the energy sector.
An important issue, which allows the extrusion of products that meet stringent quality requirements and successfully pass all strength tests is temperature distribution in the individual zones of the plasticizing system and the rotational speed of screws. The great advantage of extruders manufactured by Zamak Mercator is the high stability of preset parameters, which especially in the case of temperature has a significant effect on the properties of the obtained products and reduces the risk of degradation of the ingredients in prepared composites. We successfully conducted various tests on obtaining, among others, polyamide matrix composites, belonging to the group of condensation polymers or polyolefins e.g. polypropylene reinforced with steel wire and continuous glass fiber. The tests were conducted by means of a single-screw extruder equipped with a screw measuring 32 mm in diameter.
The proper selection of extrusion parameters and assurance of their high stability and the stability of the desired dimensions of the extruded material, ensured the success in obtaining a polyamide strand from re-granulate, designed for welding plastic components, which featured very good mechanical properties and can therefore be used in such a demanding industry as aviation. Other types of tests included obtaining composite materials wherein thermoplastic polyolefin elastomers (TPO) were the matrix, and as fillers different materials were used, such as nano-cellulose or chalk. These tests were performed by means of a twin-screw extruder with parallel screws measuring 2x24 mm in diameter. Special structures of screws and the ability to achieve high torques allow proper dispersing of any fillers in a matrix and processing of compositions, which are difficult to extrude.
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