Effect of temperature and chemical treatment on the rate of the reaction of high density polyethylene with ozone

Карпова, С. Г.; Blinov, N N; Попов, А. А.; Zaikov, G.Ye.

doi:10.1016/0032-3950(89)90101-9

Cited by 1 publication

(1 citation statement)

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“…At high degrees of exposure to ozone, when polymer chain cleavage becomes intense, the mobility of the probe increases. The observation that, in individual PHBHV, the molecular mobility decreases over the entire period of oxidation can be explained firstly by the fact that, in the inter crystallite regions of PHBHV, the fraction of straight ened chains is high enough, and, after oxidation, these chains tend to be more oriented, so that the parameter describing the degree of chain linearity [16] β = h/L = increases (here, h is the distance between the ends of the chain, L is the contour length of the mac romolecule, and k is the number of segments). It is known that each polymer has its own value of β* above which the chains tend to straighten and below which, to fold.…”

Section: Curve 4)mentioning

confidence: 99%

Effect of external influences on the structural and dynamic parameters of polyhydroxybutyrate-hydroxyvalerate-based biocomposites

Карпова

Иорданский

Попов

et al. 2012

Russ. J. Phys. Chem. B

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The EPR probe, DSC, and WARDX methods are applied to study the molecular dynamics and structure of 3 hydroxybutyrate-3 hydroxyvalerate copolymer (PHBHV, 5 mol %) and its mixtures with seg mented polyester urethane (SPEU) upon ozone oxidation and hydrothermal treatment. It is shown that time limited (3 and 5 h) treatment of the mixed compositions with water at 40°C has no noticeable effect on the dynamics of rotation of the probe (EPR) and the crystallinity of PHBHV (DSC). However, hydrothermal treatment at 70°C causes an increase in the molecular mobility of the probe in the system, accompanied, according to XRD and DSC analyses, by increases in the degree of crystallinity and density of PHBHV crys tallites. The temperature of fusion of mixed compositions also increases. During ozonation, the mobility of the probe slows gradually in PHBHV all the time, whereas in mixed compositions, a slowdown is observed only up to 3 h of oxidation time, after which, up to 5 h of ozonation, the mobility increases, along with decreases in the fraction of the amorphous phase and in the density of the crystallites.

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Section: Curve 4)mentioning

confidence: 99%