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 encapsulation. 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 properties in terms of solvent resistance, oil resistance, and abrasion resistance. Here the blends of low-density polyethylene (LDPE) and polyurethane (PU) were studied with reference to their shrinkability introducing crosslinking in both phases. Various microstructural parameters have been examined 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 high-temperature (H-T) stretched sample is higher than that of low-temperature stretched samples, which is again higher than that of the original sample. 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 increases, and further high temperature processing decreases the initial degradation temperature but enhances the rate of degradation.