A PILOT STUDY TO INVESTIGATE METHODS OF ASSESSINGTHE CHEMICAL CHANGES OCCURRING IN LATEX CONDOMSAGED UNDER DIFFERENT CONDITIONS

摘要

In recent years much progress has been made in understanding how the physical properties of NR latex condoms change when the condoms are aged under different conditions. Little progress, however, has been made in understanding the underlying chemical changes that that occur during ageing. A pilot study was undertaken to investigate various chemical, physical and spectroscopic methods to assess the chemical changes occurring under different ageing conditions. The tests investigated included ATR/FTIR spectroscopy, residual accelerator analysis and an assessment of crosslink type and crosslink density using swelling and chemical probe techniques.ATR/FTIR spectroscopy failed to identify any significant changes in the chemical structure of the rubber and appears to have little utility in assessing the ageing of latex condoms packed in air impermeable aluminium foil laminate packaging. In particular no evidence of oxidation of the rubber was seen, a finding consistent with the type of packaging used. Analysis of the accelerator residues provided useful background information but again did not provide information about the chemical changes occurring in the rubber as it aged.Out of all of the techniques investigated, the use of swelling measurements to determine crosslink densities before and after treatment with a chemical probe (propane-2-thiol) that selectively degrades polysulphidic crosslinks proved to be the most useful. Statistically significant changes in total crosslink density and crosslink type were observed depending upon ageing conditions.It is concluded that chemical probe studies offer significant promise as a method for investigating the chemical changes occurring in latex condoms as they age under various conditions. The study also provides further evidence that high temperature ageing (i.e. at 70°C) results in changes that are not typical of those seen at intermediate and ambient temperatures.