Shrinkability and microstructural properties of composites based on low-density polyethylene (LDPE) and polyurethane (PU) rubber

The heat shrinkability of polymers, which depends on their elastic memory, is being utilized in various applications, mainly in the field of encapsula tion. The elastic memory can be introduced into the system by the addition of an elastomeric phase. From the technological point of view, low-density polyethylene (LDPE) is an important polymer. Polyurethane shows excellent p roperties in terms of solvent resistance, oil resistance, and abrasion resi stance. Here the blends of low-density polyethylene (LDPE) and polyurethane (PU) were studied with reference to their shrinkability introducing crossl inking in both phases. Various microstructural parameters have been examine d to determine their effect on shrinkability. Shrinkability decreases with increase in elastomer content and with increase in cure time in the case of blends of fixed ratio, for all blends. Generally, the crystallinity of a h igh-temperature (H-T) stretched sample is higher than that of low-temperatu re stretched samples, which is again higher than that of the original sampl e. From the continuous cure characteristics studied by Monsanto Rheometer, torque was found to increase with increase in elastomer content. From high- temperature DSC it is found that with increase in PU content stability incr eases, and further high temperature processing decreases the initial degrad ation temperature but enhances the rate of degradation.