| Abstract: | Functionality of hydroxyl–terminated butadiene prepolymers (HTPB) was determined from gel point measurements as described by Strecker and French.2 Commercial HTPB samples had functionalities ranging from 1.9 to 2.6, with most of the material close to 2.0. In order to calculate functionality from gel point measurements, the hydroxyl content of the HTPB must be known. A method was developed which gave reproducible results. Curing agents used in the gel studies were viscous liquid poly-functional isocyanates with functionalities of 2.00 and 2.50. An extensive study showed that no side reactions were occuring with the isocyanates at the temperatures employed. It is estimated that the precision of the method is ±0.80%. Functionality calculated by dividing molecular weight by equivalent weight results in lower values in all cases when compared to gel point measurements. |
