Interfacial bond strength of paper-polypropylene-paper laminates

The bond strength of paper-polypropylene-paper (PPP) laminates was measured using a peel test. Testing was performed on the as-received laminates of different manufacturers, after thermal aging in air and nitrogen, after static thermal aging in oil at room temperature and 90°C, and after cyclic thermal aging in oil. Initial peel strengths ranged from 25 to 141 N per meter of width. The results of thermal aging ranged from a slight increase to a decrease of about 50% in peel strength. Aging in oil at room temperature had a smaller effect on peel strength. Thermal ageing in oil caused a decrease of up to 80% of the initial peel strength. Under cyclic thermal aging as in seen in actual cable use, some specimens delaminated while other were markedly weakened. It is believed that differential swelling of the paper and polypropylene was the primary cause of failure, as most specimens failed adhesively. The laminate with the highest initial peel strengggs not always the strongest under actual use