Abstract
In this paper, thermal and mechanical properties of ablative thermal protective material (TPM) as inhibitors for a free-standing propellant grain based on phenolic resin (PR) and acrylonitrile butadiene rubber (NBR) were investigated. NBR elastomerized PR composite, reinforced with chopped carbon fibers (CFs) (PR/NBR/CF), was prepared by homogenization of 90 parts by weight (PBW) PR in 100 PBW NBR (28 wt.% of acrylonitrile content). PR/NBR/CF composite was blended in two-roller open and closed mixers and in a twin-screw extruder. Carbon black, aluminum(III)-oxide, and fumed silica were added as promoters of thermal and mechanical properties of PR/NBR/CF. The structural analysis was studied using Fourier transform infrared spectroscopy (FT-IR). Thermal properties of the prepared PR/NBR/CF composite inhibitor were studied by ablation and firing tests, while a morphological analysis of the char layer formed after the ablation test was conducted via scanning electron microscopy (SEM). A low erosion rate of 2.00 × 10(-4) m·s(-1) and high tensile strength and elongation at break of 6.7 MPa and 419.92%, respectively, indicate that the developed materials can be applied as a thermal insulation/inhibitor of free-standing rocket propellant grains. Bond strength between PR/NBR/CF composite and aluminized composite rocket propellant (ACRP), determined via a standard peel test, showed higher adhesion forces between the PR/NBR/CF composite and the ACRP compared to the cohesion between the ACRP molecular chains.