Polyvinyl chloride - Processing and structure
Abstract - Widely different procedures for the processing of PVC have proved themselves and have succeeded in practice on the basis of the special physical and chemical properties of PVC. In this connection a distinction must be made between the processing of plasticized PVC and the relatively difficult processing of rigid PVC. A survey of the most important methods of preparation and processing is given here. The special, rather abnormal properties of PVC in comparison with other thermoplastics are partly a result of its characteristic structure. The consequences for preparation and processing must therefore be considered anew. Of course, the globular structure of PVC has an effect on the behaviour of the solid-state material and the melt, too, so that great importance must be attributed to the processes at the particle interface.
Processing Aids: The Effect of Polymethyl Methacrylate on the Fusion of Rigid Poly(vinyl chloride)
The fusion process of a PVC dryblend, both with and without a PMMA processing aid, was studied in a Brabender Plasticorder over a range of mixer temperatures. charge masses and rotor speeds. The progress of fusion was monitored by the examination of the morphology of the PVC samples taken during different stages of the fusion process. The technique of examining the acetone-swollen samples by optical microscopy before and after shearing,1 provided an insight to the mechanism of action of the PMMA processing aid. The study established that the PMMA processing aid modified both the inter-grain coefficient of friction and the packed density which had a significant effect on the initiation of the fusion process. The fusion process of both PVC compounds, i.e. with and without PMMA processing aid, was shown to proceed via a comminution mechanism, where the PVC grains were randomly broken into sub-grains and primary particle agglomerates. Concurrent with this breakdown, the cohesion of PVC agglomerates was observed.
Surface roughness monitoring by singular spectrum analysis of vibration signals
Abstract This study assessed two methods for enhanced surface roughness (Ra) monitoring based on the application of singular spectrum analysis (SSA) to vibrations signals generated in workpiece-cutting tool interaction in CNC finish turning operations i.e., the individual analysis of principal components (I-SSA), and the grouping analysis of correlated principal components (G-SSA). Singular spectrum analysis is a non-parametric technique of time series analysis that decomposes a signal into a set of independent additive time series referred to as principal components. A number of experiments with different cutting conditions were performed to assess surface roughness monitoring using both of these methods. The results show that singular spectrum analysis of vibration signal processing discriminated the frequency ranges effective for predicting surface roughness. Grouping analysis of correlated principal components (G-SSA) proved to be the most efficient method for monitoring surface roughness, with optimum prediction and reliability results at a lower analytical-computational cost. Finally, the results show that singular spectrum analysis is an ideal method for analyzing vibration signals applied to the on-line monitoring of surface roughness.