the effects of solvent, temperature, time, weight percent of catalyst on the rate and mechanism of cyclization of natural rubber (nr) was studied in toluene and xylene solutions having tin tetra chloride catalyst (sncl4). iodometric titration show, with 8% sncl4 (based on polymer weight) cyclization occurs, leaving 27.4% of the total unsaturation. infrared spectra of cyclized nr show decreased ...

in this study, modified starch was used as a fat replacer in the milk. the fat replacer was manufactured from modified starch such as pre-gelatinized and cross–linked starches. modified starches were manufactured by hydrochloric acid and citric acid treatments from potato and wheat and were added to skim milk at concentrations of 0.15%, 0.30% and 0.45%. viscosity, total solid, fat content, titr...

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the surface properties of tio2-pvdf nanocomposite membranes were investigated by incorporating different chemically modified tio2 nanoparticles into the poly (vinylidene fluoride) (pvdf) matrix. the nanocomposite membranes were prepared via dual coagulation bath diffusion and the induced phase inversion method. the membrane surface morphologies were investigated by using sem and afm and related...

maleic anhydride (man) copolymers with methyl methacrylate(mma), ethyl methacrylate(ema), methyl acrylate(ma), ethyl acrylate (ea) and buthyl acrylate (ba) ( in a 1:1 mole ratio) were synthesized by free radical polymerizations method under vacuum -azobis(isobutironitrile)(aibn) as an initiator of reaction at 701c. the copolymer compositions were determined using related 1h nmr spectra techni...

20-Homo tylosin, 20-nor tylosin, 20-deoxy-19,20-didehydro tylosin (6-vinyl tylosin) and 2",3"-didehydro-3"-deoxy tylosin were prepared by multi-step procedures. 20-Homo tylosin was about twice less active than tylosin while the other compounds exhibited very weak antibacterial activity.

Although several powerful methods exist for the redesign of enzyme structure and function these are typically limited to the 20 most abundant proteinogenic amino acids. The use of chemical modification overcomes this limitation to allow virtually unlimited alteration of amino acid sidechain structures. If heterogeneous mixtures of enzyme products are to be avoided, however, the required chemist...

The degradation of PVC at a processing temperature is mostly caused by its abnormal and unsta— ble molecular structures. It has been pointed out that its allyl chloride structures play a significant role as the abnormal and unstable structures. Inasmuch as the allyl chloride struc— tures are markedly more chemically active than the normal structure, the selective chemical treatments are applica...