There has been much interest over recent years in the rapid cooling of the internal surfaces of blow-moulded containers in order to increase production rates. Systems have employed circulating air, chilled air, CO//2 and liquid nitrogen. This article looks at the latest process reported and compares it on a performance basis with conventional cooling and with the CO//2 system. Test results are presented which show that the system improves container performance in areas of shrinkage consistency, stress-crack resistance and panel warpage. Tests with PVC indicate higher productivity than those shown on PE, with no surface imperfections. While the average productivity improvement shown on present-day machinery is 34%, improvements in excess of 50% should be possible with special machinery now under construction.
