Thermal and chemical stabilization of ethylene/vinyl acetate/vinyl alcohol (EVA‐OH) terpolymers under nitroplasticizer environments

Abstract

In this study, we compare the aging behaviors of cross‐linked ethylene/vinyl acetate/vinyl alcohol terpolymers, also referred to as EVA‐OH, when they are either immersed in nitroplasticizer (NP) liquid or exposed to NP vapor at different temperatures. While thermogravimetric analysis and differential scanning calorimetry are used to probe the thermal stability of aged NP and polymers, Fourier transform infrared, gel permeation chromatography, ultra‐violet/vis, and nuclear magnetic resonance are used to probe their structural changes over the aging process. The study confirms that NP degrades through CN cleavage, and releases HONO molecules at a slightly elevated temperature (<75°C). As these molecules accumulate in the vapor phase, they react among themselves to create an acidic environment. Therefore, these chemical constituents in the NP vapor significantly accelerate the hydrolysis of EVA‐OH polymer. When the hydrolysis occurs in both vinyl acetate and urethane groups and the scission at the cross‐linker progresses, EVA‐OH becomes vulnerable to further degradation in the NP vapor environment. Through the comprehensive characterization, the possible degradation mechanisms of the terpolymers are proposed. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41450.

Thermal stability of a eutectic mixture of bis(2,2-dinitropropyl) acetal and formal: Part B. Degradation mechanisms under water and high humidity environments

“…Water, together with acidic molecules such as HNOx and organic acids, will degrade not only the Estane polymer, but also other adjacent polymeric materials. [17,18] With the key insights about the mechanisms of the NP degradation in various In the Hregion, the spectra were multiplied 10 times to better illustrate the spectral changes. The same methodology is applied to the rest FTIR spectra in this document.…”

Thermal stability of a eutectic mixture of bis(2,2-dinitropropyl) acetal and formal: Part A. Degradation mechanisms in air and under nitrogen atmosphere

“…To better understand the changes in the FTIR spectra observed during the aging, we first discuss the spectra of BDNPA, BDNPF, and baseline NP, shown in Figure 8, and summarize the tentative assignments of their most prominent peaks in Table 2. [10,12,29,30] Since most of the major peaks are observed in the two spectral regions (2600-relatively weak, we present the results separated into these two regions, hereafter referred…”

“…NP will degrade inside these materials, which will trigger the degradation of these polymeric materials as well. [10][27] To completely resolve the NP migration and degradation, more stable nitro-plasticizes with less mobility and high chemical stability should be evaluated and/or developed as replacements for BDNPA/F.…”

“…Like many other plasticizers, NP comprises low molecular weight components, which have tendency to diffuse out of the binder domain and can decompose to reactive byproducts at elevated temperatures (>40 °C). [3,[6][7][8][9][10] Therefore, the thermal stability of NP can directly determine the shelf life of explosive charges and nearby components in munitions. Although thermal stabilities were investigated for various classes of polynitro compounds, relatively few studies focused on the understanding of the decomposition pathways of BDNPA/F [11][12][13][14] and the effects of their aging at temperatures below 70 °C.…”

“…2) : These peaks were only labeled as -CH n bending in our previous paper. [10] : vw -very weak; w -weak; m -moderate; s -strong; vs -very strong. : vw -very weak; w -weak; m -moderate; s -strong; vs -very strong.…”