| Gradient-density polyurethane foam has smooth,high-density,tough and tensile external skin and low-density core. This paper studied the compound formulations and processing conditions in making gradient-density polyurethane foam; the density distribution and mechanical properties of the products; the rheology of the main reactants and the reaction system.In order to reduce the density of rigid polyurethane foam and preserve its original performance synchronously, gradient-density polyurethane foam was manufactured. Low-density core makes it have the advantage of light mass and small heat conduction coefficient. High-density skin makes it have fine rigidity and intensity. Due to its density distribution, the properties of gradient-density polyurethane foam is superior to those of even-density polyurethane foam. Gradient-density PUF was produced in two ways : mould shaping and embed shaping, through changing volume filling coefficient, mass filling coefficient, and the size of foam core. This paper investigated the density distribution of gradient-density polyurethane foam and tested its mechanical properties, including surface rigidity, compressive strength, impact strength, flexural strength. The influence of filling coefficient and core size on mechnical properties are deeply investigated. This paper studied the influence of blowing agent dosage on the main reactant of PUF, and the chemorheology in reaction process. According to reaction characteristics and rheology, the reaction process was divided into four parts: reaction initial stage, reaction accelerates stage, gel stage, and cure stage. |
