以钯活化木炭为催化剂,通过氢化 HTPB 合成推进剂级 HHTPB

Ch. Devi Vara Prasad , P. Kanakaraju , R Vinu , Abhijit P Deshpande
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引用次数: 0

摘要

为了提高基于端羟基聚丁二烯(HTPB)和高氯酸铵(AP)的传统复合推进剂的性能,设想对HTPB进行加氢处理,从而提高基础聚合物的H/C(氢碳比)。本文尝试用活性炭负载钯为催化剂,HTPB聚合物为前驱体的催化方法对HTPB进行部分加氢反应。HTPB的羟基值为41.0 mg KOH/g,数平均分子量(Mn)为6150,多分散性(PD)为2.25。以异丙醇(IPA)和甲苯作为溶剂介质,在加氢过程中分散HTPB聚合物。估计表明,在复合固体推进剂中,以~ 37 %氢化HTPB (HHTPB)作为粘合剂,比冲(ISP)增加了1.2 s。部分加氢只是为了保留实现具有良好结构完整性的无缺陷固体推进剂颗粒所必需的其他工艺能力。相比之下,其他公司试图接近饱和。在一个容量为100 ml、压力为60 bar的反应器中合成htpb,并根据在给定催化剂浓度下改变反应器参数(如操作温度、操作压力和溶剂与聚合物比)的大量实验来控制氢化程度。通过FTIR, 1H NMR和13C NMR对最终产物进行详细表征,以揭示氢化程度以及通用聚合物的特征。HHTPB测定的羟基值与HTPB相当;然而,在37% %的转化率时,发现分子量和多分散性有轻微的增加,而其他研究人员发现oh值的损失。热重分析显示,气化速率无显著变化。与HTPB相比,HHTPB的H/C比和热值略有增加。尽管HHTPB的粘度增加,但其乙烯基型功能分布的增加有助于在推进剂加工过程中获得更好的加工性能。然而,推进剂的配方需要借助增塑剂、固体载荷等进行优化,以达到所需的性能。
本文章由计算机程序翻译,如有差异,请以英文原文为准。

Synthesis of propellant grade HHTPB by hydrogenation of HTPB using Pd-activated charcoal as catalyst

Synthesis of propellant grade HHTPB by hydrogenation of HTPB using Pd-activated charcoal as catalyst
To derive more performance from the conventional composite propellant based on hydroxyl-terminated polybutadiene (HTPB) and ammonium perchlorate (AP), it is envisaged to hydrogenate HTPB, which increases the H/C (hydrogen to carbon ratio) of the base polymer. This paper attempts to describe the partial hydrogenation of HTPB using a catalytic method that uses palladium supported by activated charcoal as a catalyst and HTPB polymer as a precursor. HTPB has a hydroxyl value of 41.0 mg KOH/g with a number-average molecular weight (Mn) of 6150, polydispersity (PD) of 2.25 was used as a precursor. Iso-propyl alcohol (IPA) and toluene were used as a solvent media to disperse the HTPB polymer during hydrogenation. The estimate revealed an increase in specific impulse (ISP) up to 1.2 s with ∼37 % hydrogenated HTPB (HHTPB) as binder in composite solid propellants. Partial hydrogenation is only attempted to retain other process capabilities essential for realizing a defect-free solid propellant grain with good structural integrity. In contrast, others attempted to reach near saturation. A reactor capacity of 100 ml, operating at 60 bar pressure, was used to synthesize HHTPB, and the extent of hydrogenation was controlled based on the numerous experiments varying the reactor parameters like operating temperature, operating pressure, and solvent-to-polymer ratio for a given catalyst concentration. Detailed characterization of the end product by FTIR, 1H NMR and 13C NMR to reveal the degree of hydrogenation along with generic polymer characteristics. The measured hydroxyl value of HHTPB is comparable with HTPB; however, a marginal increase in molecular weight and polydispersity was noticed at 37 % conversion, wherein other researchers found a loss in -OH value. Thermogravimetry analysis revealed that no significant change in the gasification rate. A slight increase in the H/C ratio and calorific value was observed for HHTPB compared to HTPB. Despite the increase in viscosity of HHTPB, the increase in the vinyl-type functional distribution of HHTPB aids for better process-ability during propellant processing. However, the propellant formulation should be optimized with the help of plasticizers, solid loading, etc., to achieve the required properties.
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