PULTRUDED FIBER-REINFORCED POLYURETHANE-TOUGHENED PHENOLIC RESIN .2. MECHANICAL-PROPERTIES, THERMAL-PROPERTIES, AND FLAME RESISTANCE

dA novel process has been developed to toughen phenolic resin by polyu rethane for fiber-reinforced pultruded composites. The mechanical prop erties of the composites (tensile strength, flexural strength, and not ched Izod impact strength) approach maximum values at 10wt% of the blo cked polyurethane content. The fabricated composites show good mechani cal properties and possess low void fraction. Notched Izod impact stre ngth of the composite (with 5wt% polyurethane content) increases by mo re than 30% compared to the virgin composite. The thermogravimetric an alysis (TGA) showed that the temperature for the 5% weight loss of the phenolic/polyurethane copolymer decreases with the increasing of the polyurethane content; however, the thermal degradation temperature is still higher than 350 degrees C. Differential scanning calorimetric an alysis (DSC) showed that the onset point of copolymer is 20 degrees C higher than that of the virgin one. The presence of the blocked polyur ethane may hinder the polymerization of phenolic resin. The modified c omposite shows excellent dimensional stability. The copolymer composit e also possesses good fire resistance. (C) 1996 John Wiley & Sons, Inc .