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S. S. Labana 《Journal of polymer science. Part A, Polymer chemistry》1970,8(1):179-193
The kinetics of the electron-beam-induced copolymerization of di(2′-methacryloxyethyl)-4-methyl-m-phenylenediurethane (DVU) with 2-hydroxyethyl methacrylate (HEMA) were studied. Monomer mixtures containing 1.96–82.8% DVU have been described at dose rates of 1.7–17 Mrad/sec with the use of 270-kV electrons. Based on rates of conversion, gel formation, and intensity-rate data, a kinetic scheme is proposed in accord with a model which undergoes unimolecular termination and for which the copolymerization and gel formation take place in a crosslinked network swollen with monomers. The rate of gel formation is: In[(1 + g)/(1 ? M2g)] = A (1 + M2)t, where g is the gel fraction, M2 is the mole fraction of DVU in the monomer charge, and A is kpki/kt. Up to 55% conversion, the rate of disappearance of unsaturation for concentrated DVU solutions (M2 > 0.03) is: In[Mo/M(1 ? M2g)] = A (1 + M2t), where M is the total unsaturation. For dilute solutions of DVU, the rate expression for pregel copolymerization simplifies to: In(Mo/M) = A (1 + M2)t. These results show that at a certain optimum concentration of monovinyl monomer—70% in the present system—both rapid reaction rates and complete copolymerization occur. Because of the inability of gel bonds to undergo polymerization, a limiting conversion is reached for copolymerizing mixtures containing insufficient monovinyl monomer. 相似文献
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Sonandkar Abhijeet A. Agrawal Pradeep N. Madrewar Dnyanoba M. Labana Sneha M. Jain Ankita P. 《平面色谱法杂志一现代薄层色谱法》2014,27(5):357-361
JPC – Journal of Planar Chromatography – Modern TLC - Impatiens balsamina belonging to family Balsaminaceae is commonly known as terda. The plant has extensive range of... 相似文献
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Jain Ankita P. Hamrapurkar Purnima D. Parate Abhijeet N. Labana Sneha M. Madrewar Dnyanoba M. Sonandkar Abhijeet A. 《平面色谱法杂志一现代薄层色谱法》2014,27(3):181-185
JPC – Journal of Planar Chromatography – Modern TLC - A simple, rapid, selective, and quantitative high-performance thinlayer chromatographic (HPTLC) method has been developed for the... 相似文献
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S. S. Labana 《Journal of polymer science. Part A, Polymer chemistry》1968,6(12):3283-3293
The kinetics of high-intensity electron beam-induced polymerization of di(2′-methacryloxyethyl)-4-m-phenylenediurethane during the network formation has been studied up to complete gelation and up to 56% conversion of unsaturation. From experimentally determined gel fractions, rate of disappearance of unsaturation, kinetic chain length, and intensity dependence, it is proposed that the polymerization takes place in a swollen network where the growing chains undergo unimolecular termination, and where gel-gel reaction is prohibited. The rate expression derived is: In [α(1 ? g)0.545] = In α0 ? 2.51 kikpt/kt where α is the total unsaturation and g is the gel fraction. The value of kp/kt is found to be 2.1 and that of GR, the free radical yield per 100 eV absorbed, to be 16; these high values are ascribed to the high viscosity of the polymerizing system. 相似文献
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