| Abstract: | The low temperature mechanical strength and the modes of failure of low density polyethylene (LDPE) films and hot air slit-seals have been assessed. Seven different LDPEs were blown into thin films (～30μm) and slit-sealed on-line, both the extrusion and sealing being undertaken using commercial equipment. When pulled in tension transverse to the extrusion direction, both the films and the slit-seals exhibited a ductile response at the higher temperatures, while at lower temperatures brittle failures were seen. The ductile-to-brittle transition temperatures were reasonably well defined with the slit-seal embrittling at significantly higher temperatures. The low temperature mechanical performance of LDPE films containing slit-seals is thus controlled by the seal. However, by using seven different LDPE resins with a range of melt flow rates, it was seen, that the low temperature response was enhanced with the low melt flow rate resins. Informed materials selection can therefore enable manufacturers to produce LDPE products containing slit-seals with good low temperature strength. |
