Influence of Polyglycidyl-type Bonding Agents on the Viscoelastic Properties of a Carboxyl-terminated Poly(butadiene-co-acrylonitrilе)-based Composite Rocket Propellant

In the present study, functionally substituted bonding agents (triglycidyl isocyanurate and diglycidyl dimethylhydantoin) were incorporated into a composite propellant formulation based on carboxyl-terminated poly(butadiene-co-acrylonitrilе) and ammonium perchlorate. Bonding agents are an important component of a composite propellant, making up to 0.5 wt.% of the formulation. They affect processing, mechanical properties, ballistics, ageing and the characteristics of insensitive munition (IM) propellants. All of the testing has been done using an unmetallized propellant formulation (80 wt.% bimodal ammonium perchlorate and 20 wt.% binder). The focus has been on the mechanical properties of the propellant, as influenced by the presence of these bonding agents. Mechanical uniaxial tensile tests were accompanied by a dynamic mechanical analysis (DMA) over a wide range of temperatures. The storage modulus, loss modulus, loss factor and glass transition temperature for each propellant sample have been evaluated. The network characteristics, such as sol-gel content and crosslink density have been calculated and successfully correlated with the mechanical properties. The dynamic mechanical studies showed that the content of the bonding agent did not influence the glass transition temperature; however, the loss factor was shown to be a function of the crosslink density

Methacrylic Acid Based Polymer Networks with a High Content of Unfunctionalized Nanosilica: Particle Distribution, Swelling, and Rheological Properties

The poor stability and tendency to agglomerate of unfunctionalized nano-SiO2 in the presence of ionic species presents a challenge for preparing poly(methacrylic acid)/nano-SiO2 nanocomposite (NC) hydrogels with desired strength and swelling capability. We proposed a facile and eco-friendly method for the preparation of PMAA/SiO2 NC hydrogels using unfunctionalized silica nanoparticles (NPs) in the form of a suspension. SEM and TEM analyses showed that the NP distribution in the polymer matrix highly depended on the particle concentration. At lower concentrations (up to 13.9 wt %), the NPs were uniformly dispersed as single nanoparticles. With an increase in NP concentration, homogeneously dispersed nanoscale aggregates were formed, while a further increase in the silica concentration led to the formation of homogeneous structures consisting of mutually interacting nanosilica particles coated with PMAA. Swelling experiments confirmed that the silica NPs behaved as adhesive fillers that interacted with PMAA chains, causing the formation of a thin polymer layer strongly adsorbed at the particle interface. The thicknesses of the adsorbed polymer layer, as well as the swelling kinetic parameters, were strongly influenced by nanoparticle size and concentration. Combining nanosilica and PMAA in the form of a soft hydrogel network provided stabilization of the NPs and ensured better mechanical properties of the obtained NC hydrogels compared to pure polymer matrix. The optimal loadings, necessary to ensure the most improved dynamical-mechanical properties, were found in the case of the formation of homogeneously dispersed, nanosized silica aggregates in a PMAA matrix