Mechanical Bonding Techniques After Moulding

A silicone rubber can be bonded to a solid substrate if it is clamped into or onto it. A very good example is the baby soother. The silicone nipple is injection moulded by a common LR process and then post cured. After that the nipples are clamped into a plastic construction or even overmoulded by thermoplastic. 

In clamping it is essential to protect the silicone part from any mechanical damage such as cuts or scratches. These ruptures of the silicone moulding will lead to potential sources for defects during its use. Mechanical damage after clamping can also be a risk. 

Another example is insulators for cable connectors which have been previously injection moulded from LR or HTV. Then, they are expanded and held in that state by a plastic spiral which is removed when it is applied onto the cable (thus retaining the original shape of the insulator). A large number of similar applications can be found in the automotive, medical fields, etc. 

To minimise risks of mechanical rupture a range of silicone rubbers, both LR and HTV grades are available in different levels of mechanical strength and Shore hardness. Table 11.11 gives a brief survey and comparison with standard properties. This table is simplified as it refers to tear resistance only. 

For additional information on general aspects of silicone rubber bonding and latest developments in silicone rnbber technology, the reader is encouraged to refer to literature such as [17, 18]. 

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The following techniques are useful for analysis and charaterization for the sizing on the fibres SEM, IR and 6PC of extracts, IGC and DMA (T ) for the fibre-matrix bond micro bond, micro failure with SEM [2], confocal laser scanning microscopy [3] DMA, flexural strength, ILSS and impact of the uni-directional composites (fixed fibre length, orientation and volume fraction distributions). After this detailed analysis, the fibres are tested in their application, which is an injection moulded compound for thermoplasts, where the microstructure (fibre length, fibre orientation and fibre-fibre distance distributions) as well as the fibre- matrix adhesion determine the mechanical properties. 

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