Viscoelastic and thermal decomposition behaviors of polytetrahydrofuran binder prepared using glycerin as a crosslinking modifier

Abstract

Polytetrahydrofuran (PTHF) is an effective binder ingredient used for improving the performance of propellants. PTHF becomes sufficiently rubbery for use as a binder with the addition of an adequate crosslinking modifier. This study investigated the viscoelastic and thermal decomposition behaviors of the PTHF binder prepared using glycerin as a crosslinking modifier, as well as the influence of the molecular weight of PTHF on the characteristics of the PTHF binder. The curing behavior of the PTHF binder was suitable for the manufacture of propellants, and the superior tensile properties of the PTHF binder made it suitable for use as a propellant binder. The degree of crosslinking of the samples decreased as the molecular weight of the PTHF increased. The PTHF binder has unique dynamic mechanical properties owing to its melting and chemical structure, and these properties were dependent on the molecular weight of PTHF. The glass transition temperature (T g ) and the loss tangent at T g decreased as the molecular weight of the PTHF increased. The temperature and frequency dependence of the PTHF binder were influenced by the melting point of PTHF. The viscoelastic properties of the binder prepared using PTHF with a molecular weight of 650 followed the time-temperature superposition principle. The activation energy for the relaxation of this binder varied remarkably at the melting point of PTHF. The thermal decomposition behavior indicated that at low temperatures, the consumption rate of the binder with low-molecular-weight PTHF was slightly larger than that of the binder with high-molecular-weight PTHF.

Mechanical Characteristics and Thermal Decomposition Behavior of Polytetrahydrofuran Binder using Glycerol Propoxylate (Mn=260) as Crosslinking Agent

“…The TG-DTA curves of the PTHF/glycerin blends showed that the exothermic decomposition occurred in the range 570-720 K and the blends were consumed between 580 and 730 K [12].The thermal decomposition behaviors of the PTHF/GPO blends were almost identical to those of the PTHF/glycerin blends.…”

“…The initial viscosities of the PTHF1/glycerin and PTHF2/ glycerin blends were 1.7 and 62.5 mPa s À1 at 100 s À1 and 353 K, respectively [12]. The initial viscosities of the PTHF/ GPO blends were smaller than those of the PTHF/glycerin blends.…”

“…The ultimate strength and ultimate strain of the PTHF1/ glycerin blend were 3.98 MPa and 713 %, respectively, and those of the PTHF2/glycerin blend were 0.85 MPa and 643 %, respectively [12]. The PTHF/GPO binders showed more flexible tensile properties with the variation in x than did the PTHF/glycerin binders.…”

“…The curing behavior of the PTHF/glycerin blend is described in Ref. [12], and illustrated by the broken line in Figure 1. The increases in the viscosities of the PTHF1/glyc- erin and PTHF2/glycerin blends were small until approximately 200 min, after which the viscosities increased remarkably.…”

“…It does become sufficiently rubbery for use as a binder when a triol material such as glycerin is added as a crosslinking modifier [9]. However, the cured PTHF/glycerin binder showed unsatisfactory mechanical characteristics for use as a propellant binder [12]. Therefore, a curing agent and crosslinking modifier that will improve the mechanical characteristics of the PTHF binder must be found.…”