The Cold Compaction of Polyvinyl Chloride (PVC) Powders

• Published in: Journal of King Saud University. Engineering sciences 1994, Vol.6 (1), p.99-112
• Main Author: Es-Saheb, M.H.H.
• Format: Article
• Language: English
• ISSN: 1018-3639; 1018-3639
• DOI: 10.1016/S1018-3639(18)30601-9

In the polymer industry, during many plastics processing methods, both conventional and novel, polymeric powers or granules are subjected to varying rates of compaction. This has an important effect on the success and efficiency of the process. Uniaxial strain rates ranging from 10−4 to 1.0 per sec., are covered for three different grades of polyvinyl chloride (PVC) powder. Four particle size fractions of these types of 150, 180, 212 and 250 μm are evaluated. The investigation shows that all materials tested exhibit strain rate sensitivity to varying degrees (increased resistance to compaction as the speed is increased). Also, it is found that the values of the mean yield pressure, determined by Heckel relation, are increasing with the speed of compaction, as well as with the particle size, in a non-linear manner. Generally, both ductile and brittle behaviors existed in the compaction process, but at higher speeds (strain rates) the amount of plastic deformation decreased (i.e. brittle behavior dominated), which resulted in smaller contact areas among the compacted particles and increased the final compact ‘capping’ possibilities. Furthermore, the tensile strength of the final compacts, assessed by the diametral compression ‘Brazilian’ test, shows a non-linear increase with the speed of compaction. Finally, as the particle size decreased and the particle shape becomes more irregular, the relative tap density increased.