Setting shrinkage of polyester

Fig. A shows the effects of CoOc and MEKPO contents on setting shrinkage of polyester resin concrete. The setting shrinkage increases with rising contents of CoOc and MEKPO. In particular, the shrinkage is remarkably affected by MEKPO (catalyst) content rather than CoOc (accelerator) content.

Figure 5. Relationship between curing time and setting shrinkage of polyester...

Fig. 10 shows the comparison of data on setting shrinkage of polyester resin concrete determined by the experimental automatic apparatus and embedded strain gages. 

The setting shrinkage of polyester resin concrete increases with a rise in contents of catalyst and accelerator, and is markedly affected by catalyst content rather than accelerator content. 

Polyester/long-staple fibres are also used in the linen industry, where the yams may be of either the stretch-broken or unbroken type, but are more commonly of the latter. Heat-setting of such fabrics may be carried out at 180 C for 30 secs on the hot air pin stenter, allowing up to 2% weft shrinkage with overfeeding only to compensate for any warp shrinkage that has occured in the previous process. 

With RTSs, any loose resin and reinforcement should be removed and the affected area cleaned and dried. It may be useful to roughen surrounding areas, to obtain better adhesion. For superficial damage (to gelcoat only), apply catalyzed/activated resin to the damaged area and allow to set/solidify. Film, such as transparent ceUulose, tape or TP polyester, may be used to keep the resin in position and impart a smooth surface finish. Apply a thicker film of resin than usual, to allow for shrinkage. When the repair patch has fully hardened, dress the resin back to the correct contour of the molding. 

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