Datasheet

Thursday, 17 July 2003 MiniProject: Design Aspects Colin K McCord
EEE512J2 – Electronic Product Design Page 31 Chapter 6: Physical Design
The first stage in manufacturing plastic is polymerisation. The two basic polymerisation methods are
condensation and addition reactions. These methods may be carried out in various ways. In bulk
polymerisation, the pure monomer alone is polymerised, generally either in gaseous or liquid phase,
although a few solid-state polymerisation’s are also used. In solution polymerisation, an emulsion is formed
and then coagulated. In interfacial polymerisation, the monomers are dissolved in two immiscible liquids, and
the polymerisation occurs at the interface of the two liquids.
Chemical additives are often used in plastics to produce some desired characteristic. For instance,
antioxidants protect a polymer from chemical degradation by oxygen or ozone; similarly, ultraviolet stabilisers
protect against weathering. Plasticizers make a polymer more flexible, lubricants reduce problems with
friction, and pigments add colour. Among other additives are flame retardant and antistatic.
6.3. Shaping of Plastic
Plastic products are made from plastic resins, which melt into a syrupy liquid when heated. There are several
standard manufacturing techniques for shaping plastics (see figure 6.3a for illustrations), many of which
could be used in manufacture of the ABS plastic case of the ECG monitor.
Figure 6.3a. Illustrations of manufacturing techniques for shaping plastics, source [MS Encarta Encyclopaedia 96]