Changes/variations during manufacturing and storage of free radical-polymerized hydroxyl-terminated polybutadiene resin/prepolymer (widely used binder for the composite solid propellants) are not reflected in terms of appreciable change in the hydroxyl value. As a result, cured properties of the propellant mixed using the given formulation finalized by keeping R ratio (NCO/OH ratio) within 0.7–0.9 did not yield predicted mechanical properties. Investigations carried out subsequently, by the authors, identified the root cause to be variations in molecular weight and its distribution, which were not indicated in terms of change in hydroxyl value. Authors confirmed their findings by 1H1NMR studies whereby the variation in molecular weight distribution could be explained in terms of variation in spin–spin relaxation time (T 2) values.

中文翻译：

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HTPB预聚体对复合固体推进剂性能的影响

自由基聚合的羟基封端聚丁二烯树脂/预聚物（广泛用于复合固体推进剂的粘合剂）的制造和储存过程中的变化/变化并未反映在羟基值的明显变化方面。因此，通过将 R 比（NCO/OH 比）保持在 0.7-0.9 内而最终确定的给定配方混合的推进剂的固化性能并没有产生预期的机械性能。作者随后进行的调查确定了根本原因是分子量及其分布的变化，而这些变化并未以羟值的变化来表示。作者通过 1H1NMR 研究证实了他们的发现，由此可以根据自旋-自旋弛豫时间 (T 2) 值的变化来解释分子量分布的变化。