Effects Of Organic Peroxides Research Articles

Thermal and mechanical properties of LDPE by the effects of organic peroxides

Thermal and mechanical properties of LDPE by the effects of organic peroxides

Effects of Organic Peroxides on the Curing Behavior of EVA Encapsulant Resin

Compounds of poly(ethylene-co-vinyl acetate) (EVA with vinyl acetate content 33%) with three different organic per- oxides, namely, dialkyl peroxide, peroxyester peroxide, and peroxyketal peroxide, were prepared with a twin screws extruder and a two-roll mixing mill. The cure behavior of the EVA compounds was analyzed from rheographs, which were obtained by a moving die rheometer (MDR) at various curing temperatures between 150?C to 170?C. The effects of organic peroxides on cure behavior were examined. The dynamic curing obtained by the torque rheometer provided sufficient experimental data to show that dialkyl peroxide is not suitable because it has a high half-life temperature and its by-products can discolor the final product. Peroxyester peroxide is good for curing at temperatures in the range of 150?C to 160?C, which accomplished an ultimate cure within 5 to 8 minutes. Also, the peroxyketal peroxide has higher performance, which decreased the optimum cure time to 3 minutes. The thermal decomposition mechanism of organic peroxide was applied to explain how the cure behavior is affected by generated free radicals.

Effect of organic peroxides on the morphology and properties of EVA/Cloisite 15A nanocomposites

AbstractThis article describes the effect of the presence of organic peroxides on the morphology and properties of ethylene vinyl acetate copolymer (EVA)/Cloisite 15A nanocomposites. The results show that the presence of dicumyl peroxide (DCP) or dibenzoyl peroxide (DBP) during the preparation of EVA/Cloisite 15A clay nanocomposites gives rise to intercalated, exfoliated, or mixed morphologies, which are not normally observed for samples prepared in the absence of organic peroxides. In the absence of clay, both DCP and DBP initiate de‐acetylation and chain scission of EVA chains, but the influence of DBP is more pronounced. The presence of clay inhibits the initiation of EVA degradation by DCP free radicals, which can be observed in the higher tensile strength values for DCP treated samples, as well as in the de‐acetylation step in the TGA curves. DBP has a more significant influence on the polymer degradation, and this gives rise to reduced thermal stability and mechanical properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Effect of organic peroxides on the thermal decomposition of expanded polystyrene with the addition of α-methylstyrene

Recently, as a part of thermal recycling, in order to reduce the consumption of energy and get oligostyrene of several thousands of molecular weight, which can be used as a kind of fuel oil, the thermal decomposition of expanded polystyrene (EPS) with α-methylstyrene as a chain-transfer agent was studied at a temperature about 200 °C. In this work, three kinds of organic peroxides were used as radical accelerators in the thermal decomposition of EPS with α-methylstyrene. We found that the addition of dicumyl peroxide (DCP) enhanced the thermal decomposition of EPS even at lower temperature, about 140 °C, but the addition of tert-butylcumyl peroxide (BCP) was less effective than DCP. On the other hand, di- tert-butyl peroxide had almost no effect on the thermal decomposition of EPS. The activation energy, determined from the rate coefficients, were 66.6 and 70.5 kJ/mol for DCP and BCP, respectively.

Effects of organic peroxides on human epidermal keratinocytes

Human epidermal keratinocytes cultured for about 10 days were incubated for 60 min with ferrous ions, ascorbic acid, H 2O 2 t-butyl hydroperoxide or benzoyl peroxide. Lipid peroxidation was determined by malondialdehyde and ethane formation and cytotoxicity by the trypan blue exclusion test. ADP complexed ferrous ions and ascorbic acid led to high lipid peroxidation of keratinocytes, but no cell damage occurred. In contrast, H 2O 2, t-butyl hydroperoxide and benzoyl peroxide were unable to induce lipid peroxidation. Cell viability decreased greatly with benzoyl peroxide. The addition of ferrous ions to keratinocytes incubated with H 2O 2, t-butyl hydroperoxide or benzoyl peroxide resulted in a significant increase in lipid peroxidation whereas only slight additional cell damage occurred. In keratinocytes incubated with benzoyl peroxide and simultaneously irradiated with UV-A, lipid peroxidation increased and was several times higher than with UV-A alone. (+)-Cyanidanol-3 inhibited lipid peroxidation in both systems whereas EDTA was effective only when keratinocytes were exposed to benzoyl peroxide and ferrous ions. The data indicate that in human epidermal keratinocytes lipid peroxidation is inducible, but that it is not related to cell damage. Cytotoxicity caused in keratinocytes by benzoyl peroxide must be due to a mechanism dissimilar to lipid peroxidation.

Effect of organic peroxides on initial coloring of poly(vinyl chloride)

AbstractSuspension polymerization of vinyl chloride was studied using five organic peroxides which show similar polyerization rates. Initial coloring of polymers obtained depended on the kinds of peroxides and the amount of peroxides used. Initial coloring of PVC had no relation to water solubility of the peroxides, but depended greatly on their susceptibility to hydroysis. Organic peroxides with susceptibility to hydrolysis remained low in the polymer, and yielded PVC showing preferable initial coloring.

Self‐extinguishing polystyrene foaming‐in‐place beads

AbstractThe preparation of practical self‐extinguishing polystyrene foaming‐in‐place compositions by suspension polymerization is described. The halogen necessary for self‐extinguishing characteristics is incorporated by chain transfer. The synergistic effect of organic peroxides decreases drastically the amount of halogen necessary. For example, 0.3 pph 1,2‐dibromotetrachloroethane in the presence of 0.2 pph dicumyl peroxide renders the composition self‐extinguishing, while 1.0 pph is necessary without peroxide. The rate of polymerization is unaffected by the presence of this chain transfer agent, while the molecular weight is reduced considerably. The effectiveness of other halogenated chain transfer agents and peroxy compounds has been demonstrated. Silicone mold release agent exerts a deleterious effect on the self‐extinguishing properties.

Effects of Organic Peroxides on Corrosiveness of Aviation Fuels and Pure Hydrocarbons.

Effects of Organic Peroxides on Corrosiveness of Aviation Fuels and Pure Hydrocarbons.