Hydroxyl Terminated Natural Rubber (HTNR) as a Binder in Solid Rocket Propellant

Abstract

Controlled degradation of deproteinized natural rubber by oxidative method using cobaltous leading to the formation of telechelic liquid natural rubber (TLNR) has been the subject of study in the current work. Hydroxyl-terminated natural rubber (HTNR) having number-average molecular weights (Mn) below 10,000 gmol-1 were synthesized at temperatures 60°C using Cobalt bis (acetyl acetonate) (Co) in the presence of ethanol and Sodium borohydride. The HTNR were characterized structurally by using Fourier Transform Infrared (FTIR), Gel Permeation Chromatography (GPC) and Nuclear Magnetic Resonance (NMR) spectroscopy. From the FTIR and GPC analysis, one hour reaction showed the lowest Mn around 6691 gmol-1 comparable to Hydroxyl terminated polybutadiene (HTPB) which were 7708 gmol-1. As the reaction time increases the Mn also increase up to 8 hours of reaction. FTIR indicated that the synthesized HTNR contained hydroxyl end groups. The study showed the optimum percentage of Cobalt bis (acetyl acetonate) is 5% which produce the lowest molecular weight. Next, the HTNR underwent crosslinking reaction with isophore diisocyanate (IPDI). Then, metal fuel (aluminium powder, Al), oxidizer (ammonium perchlorate, AP) and HTNR were mixed together and went through compression process to produce solid rocket propellant. Burning rate obtained from HTNR samples were 2.78 mms-1 which were equivalent to HTPB samples which is 2.94 mms-1.

Evaluation of the Characteristics of Plastic Explosive Adhered by Liquid Natural Rubber

“…Liquid natural rubber is a liquid polymer made of natural rubber [9,10]. This rubber has been applied as a binder for many fields such as paints, glues, and binders for solid rocket fuel [11] etc. Up to now, a PBX bonded by the LNR binder has not been reported.…”

Preparation and Characterization of Low-Molecular-Weight Natural Rubber Latex via Photodegradation Catalyzed by Nano TiO2

“…LNR commonly has a molecular weight of less than 20,000 g/mol and is considered as a new material derived from NR. Furthermore, the degradation process also opens up the opportunity to use LNR in various applications such as in binders [8], adhesives [9], coatings [10], processing aids [11,12], compatibilizers [13], and encapsulation of paraffin wax [14], as well as precursors for new materials [15,16] and further modifications [17]. Consequently, reducing the molecular weight has extended the potential and possible applications of NR.…”

“…Hence, it has been shown that the LNR chain has formed hydroxyl and carbonyl groups at its extremities. LNR with a hydroxyl end group becomes attractive when its application can be expanded into new areas such as precursor specialty block polymerization [21,22], high-performance adhesives [9,23], and binders [8]. LNR has the same repeating unit ( cis -1,4-isoprene) as virgin NR; consequently, they exhibit similar excellent characteristics such as flexibility, elasticity, low temperature, etc.…”

Effect of Some Experimental Factors on Preparation of Liquid Natural Rubber

“…In this case, it cannot be used for polymer composites which either contain the power-intensive fillers or are formed by casting as a fuel-binder for solid rocket propellants. For this purpose, it is necessary to strongly decrease molecular weight of NR to below 50,000 [2].…”

“…Liquid natural rubber (LNR) can be synthesized by many methods including mechanic impact, thermal degradation, redox and photochemical method etc [1][2][3][4][5][6][7][8]. By those methods, the molecular weight of the LNRs was from 2,000 to 50,000.…”