The present article reports the investigation on the effects of solvent and position of functionality on various physical properties of polyurethanes (PUs) based on hydroxyl-terminated polybutadiene (HTPB). The PU films (curative) were prepared by coupling HTPB (P0) with isophorone diisocyanate (IPDI) in various solvent media. The PUs obtained in different solvent media displayed similar thermal profile and glass transition temperature (T_g), but their tensile properties varied significantly. Optimized tensile properties were observed when tetrahydrofuran was used as the solvent media. In the course, the investigation of the functionality effect, tetrazole (M1, M2, and M3) were covalently attached at the terminal carbon of HTPB to obtain three modified HTPBs (P1, P2, and P3), thereby coupling with IPDI to obtain the corresponding tetrazole functional PUs films. Pristine (P0–PU) and functional PU (P1–PU, P2–PU, and P3–PU) films have similar thermal profile and T_g (−76 °C), but they have a notable enhancement in tensile properties; for example, tensile strength and elongation at break of P0–PU were found to be 3.21 MPa and 727%, respectively, whereas these values were 4.84 MPa and 958%, respectively, in the case of P3–PU. It was observed that on increasing the number of methylene group from 1 to 3 between HTPB and tetrazole moiety, the strength of hydrogen bonding increases, which facilitates better packing of urethane network in the PU and hence improves the tensile properties. Also, modification of pristine HTPB with tetrazole derivatives enhanced the calorific values of the resulting PUs.

中文翻译：

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溶剂和官能度对基于羟基封端的聚丁二烯（HTPB）的聚氨酯的物理性能的影响

本文报道了有关溶剂和官能度位置对基于羟基封端的聚丁二烯（HTPB）的聚氨酯（PU）各种物理性能的影响的研究。通过在不同溶剂介质中将HTPB（P0）与异佛尔酮二异氰酸酯（IPDI）偶联来制备PU膜（固化剂）。在不同溶剂介质中获得的PU表现出相似的热曲线和玻璃化转变温度（T _g），但它们的拉伸性能差异很大。当使用四氢呋喃作为溶剂介质时，观察到最佳的拉伸性能。在此过程中，对功能性作用的研究是，将四唑（M1，M2和M3）共价连接到HTPB的末端碳上，以获得三个修饰的HTPB（P1，P2和P3），从而与IPDI偶联以获得相应的四唑功能性PU薄膜。原始（P0–PU）和功能性PU（P1–PU，P2–PU和P3–PU）膜具有相似的热分布和T _g（-76°C），但它们的拉伸性能显着提高；例如，P0–PU的拉伸强度和断裂伸长率分别为3.21 MPa和727％，而P3–PU的拉伸强度和断裂伸长率分别为4.84 MPa和958％。观察到，随着HTPB和四唑部分之间的亚甲基的数目从1增加到3，氢键的强度增加，这有利于聚氨酯网络中聚氨酯网络的更好堆积，因此改善了拉伸性能。同样，用四唑衍生物对原始HTPB进行修饰可提高所得PU的热值。