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The thermal decomposition of hydrogen cyanide diluted to 0.2, 0.5, and 1.0 mol% in argon was studied behind incident shock waves over the temperature range 2600–3600 K. The decomposition process was followed by monitoring the CN X2Σ+-B2Σ+ (0-0) absorption centered at 3883 Å. The bimolecular rate constants for the reaction HCN+Ar→H+CN+Ar were obtained from the initial slopes of absorption; k1=(1.26±0.28)×1016exp[–(99.69±1.39)kcal mol−1/RT] cm3 mol−1 s−1. The kinetic results are well fitted by the classical collision-theory expression, k1=λ(Z⁄n!)(E⁄RT)nexp(–E⁄RT), with λ=0.22, n=3.5, and E=D0(H–CN)= 118.7 kcal/mol. The overall absorption profiles were found to be explicable on the basis of the reaction scheme involving the homorecombinations of H and CN as well as the chain reaction with H and CN as carrier species.

ABSTRACT:The physical structure of oriented polyoxymethylene (POM) drawn in two steps by press drawing and subsequent simultaneous biaxial drawing was studied. The degree of crystallinity, the orientation, and the tensile modulus depending on draw ratio were analyzed. By the press drawing method, the draw ratio reached 6.0, the tensile modulus was 4.5 GPa, and the degree of crystallinity decreased from 70% to 65%. By the two-step drawing of press drawing followed by subsequent simultaneous biaxial drawing, the tensile modulus reached 11 GPa when the draw ratio was 14 times, and the degree of crystallinity increased from 71% to 76 -80%, but it did not depend on the draw ratio, and showed effectively a constant value (average 77%). The physical structural properties, such as the degree of crystallinity, the orientation of the crystal, and the lamella structure, were analyzed by SEM, X-ray diffraction, and other methods.

ABSTRACT:The physical structure of polyoxymethylene (POM) drawn into two steps by a press and a simultaneous biaxial drawing machine was studied and the drawing dependency on the degree of the crystallization, the orientation, and the modulus were analyzed. The stretching ratio by the press reached 6.0 and the tensile modulus of elasticity increased from 2.5 to 4.5 GPa. However, the degree of crystallization decreased slightly. The rupture elongation increased in the lower drawing region and it peaked when the drawing ratio was 1.7. The film stretched by 2 times was drawn by the biaxial drawing machine. The high tensile modulus of elasticity was obtained and the maximum value was 11.5 GPa at 14 times of the drawing ratio. The lamella structure of POM was supposed to loosen and become oriented to the drawing axis ambiguously by the first drawing. The lamella was highly oriented by the second stretching procedure. The tensile strength and the elongation as well as the modulus were analyzed as a function of the degree of the stretching and the crystallization.

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