¹H‐NMR investigation of the thermooxidation degradation of poly(oxymethylene) copolymers

Abstract

ABSTRACT:The thermooxidative degradation of poly-(oxymethylene) copolymer (CPOM-Y) powder was studied in air in 150°C. The effect of the sequence distribution of degraded poly(oxymethylene) (POM) samples on the thermal decomposition behavior was investigated with 1 H-NMR and gas chromatography/mass spectrometry. The results showed that the degradation process of CPOM-Y could be divided into three stages with a gradually increasing degradation rate. The change in the sequence molar fractions agreed with the fact that the ethylene oxide (EO) units had higher thermal stability, and the degradation of POM was due to the decomposition of formal units. At the beginning, CPOM-Y tended to split off formaldehyde, starting at the chain ends, some of which were not ended by EO units. In stage 2, the thermooxidation of POM occurred in the amorphous phase. In stage 3, no obvious rules for the changes in the sequence contents were obtained from NMR results, and this indicated further random chain scission and unzipping occurring heavily in the crystalline bulk. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: [577][578][579][580][581][582][583] 2004

The influence of polyoxymethylene molar mass on the oxidative thermal degradation of its nanocomposites with hydroxyapatite

“…The degradation rate of chain scission is higher than that of the initial step; in chains with higher molar mass, more formaldehyde formation occurs and the degradation rate increases linearly with increasing molar mass. On the other hand, Pan et al [6] postulated that the degradation process of POM copolymer could be divided into three stages with a gradually increasing degradation rate: (1) At the beginning, POM chain tends to split off formaldehyde, starting at the chain ends, some of which were not ended by ethylene oxide (EO) units; (2) in the second stage, the thermooxidation of POM takes place in the amorphous phase, and finally, in the last stage, further random chain scission and unzipping occur in the crystalline phase. In the work done by Archodoulaki et al [11], it was found that the onset temperature of degradation for POM copolymer with the highest average molar mass was the highest.…”

“…However, these comonomer units strongly affect the thermal and chemical behavior of the copolymer. Thus, the properties of POM copolymers depend on the comonomer composition and on the sequence distribution (e.g., random or block) of the constituent comonomers [6].…”

Thermooxidative degradation of polyoxymethylene homo- and copolymer nanocomposites with hydroxyapatite: Kinetic and thermoanalytical study

“…Commercial c-POMs are typically produced through the cationic copolymerization of trioxane and 0.1-15 mol % of a cyclic ether, such as ethylene oxide (EO), dioxolane, or 1,3,5-trioxepane. Acetal copolymers consist of POM segments with oxyethylene units distributed in the chain, which affect the thermal and chemical behavior of the copolymer [13]. According to Kern [14], degradation reactions in POM-homopolymers are also occurring in POM copolymers but the copolymer units hinder the unzipping of the polymer chain and the depolymerisation is stopped at the C-C bond of the copolymer unit [15].…”

Insights into the direct selective oxidation of methane to methanol over ZSM-5 zeolytes in aqueous hydrogen peroxide

“…We attributet hese to water-soluble polyoxomethylenes (POM) which have am olecular formula of HO(CH 2 O) n H. The reported 1 HNMR spectrum of POM species from formaldehyde presentss ignals at around 1.9-2 ppm (OH) and % 4.5-5.2 ppm (CH 2 -O). [44][45][46] The peaks at around 4-5 ppm would have been obscured by the only partially suppressed water signal. In aqueous solution HCHO is known to polymerise to linear POM, where n can be as high as 100, [44][45][46] and in this respect zeolites are known to promote POM formation.…”

“…[44][45][46] The peaks at around 4-5 ppm would have been obscured by the only partially suppressed water signal. In aqueous solution HCHO is known to polymerise to linear POM, where n can be as high as 100, [44][45][46] and in this respect zeolites are known to promote POM formation. [47] Low molecular weightP OM (n < 8) is water-soluble.…”