Measuring the time evolution of the gas pressure in closed cell polyolefin foams produced by compression moulding

The evolution with time of the gas pressure in the cells of low density closed cell polyolefin based foams has been measured using a method that combines mechanical testing and modelling of the compressive response. The results have proved that foam blocks produced by compression moulding present a sub-atmospheric, non-constant gas pressure after production, the increase of pressure with time being a very slow process. In fact, it has been shown that this process has not finished 200 days after production. In addition, it has been also shown that the cooling of the foam during production affects the pressure distribution within the foam.