Technological Characteristics of Injection Molding of Dynamic Elastoplasts Based on Thermoplastic Polyolefins and Butyl Rubber

Resumo

The influence of the butyl rubber concentration and technological mode of injection molding on the main properties of elastoplasts based on butyl rubber and thermoplastic polyolefins—low-density polyethylene and polypropylene—was considered. Initially, the influence of the butyl rubber concentration on the ultimate tensile stress, tensile stress at yield, and elongation at break of the polymer mixtures based on low-density polyethylene and polypropylene was investigated. It was found that, with the concentration of butyl rubber in the composition based on low-density polyethylene equal to 20 wt % or higher and in the composition of polypropylene equal to 40 wt % or higher, the compositions change the deformation mechanism, i.e., the transition of plastic deformation into highly elastic deformation characteristic of rubbers occurs. The use of dicumyl peroxide and sulfur as crosslinking agents made it possible to obtain dynamically vulcanized elastoplasts with improved physicomechanical and technological properties during the “monotrem” process. The original design of the worm screw on the injection molding machine of the brand DE3132.250Ts1 makes it possible to carry out on it a “monotrem” technology of obtaining elastoplastic and dynamic vulcanizates on their basis. This technology allows in a single cycle of injection molding simultaneously to implement in the material cylinder the mixing of thermoplastic and elastomeric components in the melt, followed by their vulcanization with dicumyl peroxide or sulfur to form dynamically vulcanized elastoplasts. During the investigation the technology of mechanochemical synthesis of initial polymer mixtures and dynamic elastoplasts, the influence of the temperature regime of injection molding on the cylinder zones, the injection molding pressure, the mold temperature, and the injection boost time on their ultimate tensile stress, elongation at break, and volume contraction was established. A detailed interpretation of the observed regularities in the change in the properties of composite materials was given.