Pultrusion of Fast-Gel Thermoset Polyurethanes: Processing Considerations and Mechanical Properties

摘要

Although polyurethane resins were developed in the 1930s, they only began to appear significantly in composites about three years ago. When compared to the matrix resins that are currently dominant in pultrusion, polyurethanes offer a range of properties that are generally equal or superior. Of particular interest, polyurethane resins exhibit superior elongation-to-failure and impact resistance, adhere exceptionally well to most materials including the commonly used fibers in composites, are formulated from inexpensive raw materials and contain no styrene, and are already commercially produced in large quantities. However, the industries that manufacture large quantities of polyurethanes (such as cushioning and energy-management foams) employ processing technologies that are considered extremely difficult to adapt to composites production. Two significant barriers were identified for pultruding polyurethane resins: the fast gel times of the raw materials when mixed and the tendency of the chemistry to produce internal voids in the material during gel and cure. The research described in this paper presents the processing technologies and methods developed that allow highspeed production of high-quality polyurethane pultrusions. Mechanical property testing of the composite specimens produced indicate the degree to which the properties of the neat resin are translated into useful composite properties.