COMPOSITES OF POLYVINYL-CHLORIDE WOOD FIBERS .1. EFFECT OF ISOCYANATE AS A BONDING AGENT

Various parameters concerning the performance of isocyanate as a coupling agent have been discovered. Greater premixing time (e.g., 20 min) leads to an improvement in the mechanical properties of the composites. The isocyanate solution is more efficient in comparison with undiluted isocyanate. Moreover, the chemical structure of isocyanate, which provides a better interaction with thermoplastics, results in superior properties. The reactivity of different isocyanates decreases in the following order: PMPPIC, TDIC, HMDIC, EIC. Again, isocyanate can act as a promoter or as an inhibitor, depending on the concentration of isocyanate used. For example, with a moderate concentration, it promotes maximum mechanical properties, while with a higher concentration, mechanical properties deteriorate. In addition, the nature of the pulp (e.g., CTMP, cotton, or sawdust) and fiber loading percentage as well as different grades of polymer supplied by different companies also play an important role in the mechanical properties of thermoplastic composities. © 1990, Taylor & Francis Group, LLC. All rights reserved.