Available online
Description
The programme examines (1) industrial polymerisation of vinyl chloride (2) polymer chain lengths (3) polymer structure and crystallinity.
The programme examines (1) industrial polymerisation of vinyl chloride (2) polymer chain lengths (3) polymer structure and crystallinity.
| Module code and title: | ST294, Principles of chemical processes |
|---|---|
| Item code: | ST294; 15 |
| First transmission date: | 22-09-1975 |
| Published: | 1975 |
| Rights Statement: | |
| Restrictions on use: | |
| Duration: | 00:23:11 |
| + Show more... | |
| Producer: | Barrie Whatley |
| Contributors: | I. Boustead; David Roberts |
| Publisher: | BBC Open University |
| Keyword(s): | Addition polymerisation; Bulk polymerisation; Chain length; Polyvinylchloride; PVC properties; Suspension |
| Footage description: | Ian Boustead introduces the programme with a demonstration of a simple polymerisation reaction. He combines a monomer with some initiator in a test tube. Boustead uses graphics to look at the equations for the basic polymerisation reaction and that for vinyl chloride. He then refers back to his demonstration above and explains what modifications have to be made to do this on an industrial scale. Boustead then lists the advantages and disadvantages of suspension and bulk polymerisation at the industrial level. Boustead uses graphics to discuss the sort of equipment used in industrial suspension polymerisation of vinyl chloride. He goes on to do the same for bulk polymerisation of vinyl chloride. Boustead shows samples of products from both processes as well as electron micrographs to compare the results. Boustead explains how the progress of the reaction is monitored. An animated graph is used as an aid. Boustead shows several manufactured items made of PVC which all have very different physical properties. He then shows examples of the pure polymer from both processes. Boustead explains the tests which were carried out to compare three physical properties - flexibility, impact and tensile strength. The results are shown on a chart. David Roberts looks at the basic polymerisation reaction equation to explain the differences in the same polymers made by different processes. He points out that the value N (the number of repeating units in the polymer chain) is the important variable. Roberts then explains how N is measured. He relates this to viscosity and shows how this is measured in a lab demonstration. The results, mean chain length, for the two samples are shown. Roberts shows that mean molecular mass alone is not sufficient to account for the physical properties of the polymer. Roberts explains how molecular mass distribution is determined, by gel-permeation chromatography. He uses several models to demonstrate the method. Roberts shows a chart recording from the chromatograph for a polystyrene sample. He explains, in detail, how the apparatus works. Ian Boustead, with several graphic aids, explains how N can be controlled by changes in reaction temperature. He then explains how temperature affects chain termination. David Roberts uses several molecular models of monomers and polymers to explain how shape of polymers affects their physical properties. |
| Master spool number: | 6HT/71591 |
| Production number: | 00525_1167 |
| Videofinder number: | 2752 |
| Available to public: | no |
