Development, control, and monitoring of foam produced during rotational moulding

The main conclusions were that CBA developed foams could be successfully controlled using PST, heating rate, polymer rheology, or CBA concentration, in agreement with the literature. It is also identified that the structures could also be significantly controlled in terms of foam density range by developing them in a vacuum environment (0.134-0.291 g/cm3), by polymer particle size (0.227-0.351 g/ cm3), or to a much lesser extent by the cooling rate used (0.313-0.329 g/cm3).

The parameters controlling foams produced without CBAs are studied for the first time, finding that they may be effectively controlled by minimising the polymer particle size and maximising the heating rate, achieving a cell density improvement of 115 %. A novel ultrasonic monitoring method is successfully developed and used to monitor polymer thickness changes during the heating, and the formation of air gaps during the cooling of a moulding.

Foam mouldings are also observed using the method, finding a 16 % reduction in signal amplitude at CBA decomposition. The processes and procedures created are ready to be exploited in industry, and will enable foams for large-scale lightweight rotationally moulded multi-layer products to be optimised.<br><br>