Manufacturing and characterization of soy-based pultruded polyurethane composites

In the recent past, composites have been finding various applications in civil infrastructure, marine, transportation, automotive and non-automotive applications by replacing metals in structural components. Pultrusion is considered to be a cost effective method for manufacturing composite materials. Polyurethane resin systems form a good alternative to the conventional styrene based systems in pultrusion due to their better physical, chemical and mechanical properties. Polyols derived from soybean oil along with isocyanates produce polyurethanes that can match in many aspects with one derived from the petrochemical polyols. Even though, polyurethanes have good properties there are lots of challenges like designing unique material handling and processing methods. A two part polyurethane resin and a two part soy-based polyurethane resin system have been considered in the present work. Various issues like design of injection box, the component metering unit and die design which complicated the process of polyurethane pultrusion are discussed. Glass fiber reinforced composites were manufactured and mechanical characterization was performed. The properties of the soy-based polyurethane and base polyurethane pultruded parts are compared. It was found that soy-based polyurethane pultruded parts had good flexural properties and comparable impact properties than the base polyurethane system. In-core fiber reinforced composites are also manufactured using a polyester resin system. The process of manufacturing these pultruded composites are discussed in detail. Low velocity impact test was performed on these core filled parts and it was observed that ±45 fiber mat showed higher damage when compared to the random fiber mitt pultruded part --Abstract, page iii