SynopsisOxidation of atactic polypropylene (APP) obtained as by product from polypropylene production is studied in melt to obtain polymers which are easily emulsified by commercial emulsifiers. The experiments are done using a stirred, jacketed glass reactor and the relevant heating, air-feeding, and sampling attachments. Oxidation is followed by the change of carbonyl absorbance, iodine number, acid number, molecular weight, and melt flow index (MFI) by time. The relevant tests are done by infrared (IR) spectroscopy and gel permeation chromatography (GPC) and standard tests with minor modifications are applied. It is found that as temperature, air flow rate, and mixing speed are increased, higher oxidation rates are obtained. It is also found that initiator types and concentrations used are not as effective as the above parameters. By oxidation as molecular weight reduces, molecular weight distribution narrows. Correlation between MFI, iodine number, and molecular weight of the oxidized APP is also made for easy follow-up of oxidations. In addition, it is found that for easy and stable emulsions, APP must be modified by oxidation to iodine number and MFI higher than 30 mg/g and 3.5, respectively.
In this study, the effect of the particle size of solid protective agent, commercially obtained and in-situ formed tricalcium phosphate (TCP), on the particle size of suspension polymerized polystyrene (PS) is investigated. It is concluded that when a solid protective agent like TCP is used, its particle size and distribution plays an important role in both suspension stability and particle size of the PS obtained. As the particle size of the TCP becomes smaller, the particle size of the PS obtained is reduced in line with it. In situ precipitation of TCP reduces its particle size considerably. Therefore, to produce PS with the same particle size, lesser amount of in-situ precipitated TCP is required which gives way to production recipe savings and cleaner PS products. ZUSAMMENFASSUNG:Der EinfluD der TeilchengroRe eines festen Suspendiermittels (handelsiibliches oder in-situ gebildetes Tricalciumphosphat (TCP)) bei der Suspensionspolymerisation von Polystyrol (PS) auf dessen Teilchengrdlje wurde untersucht. Aus den Ergebnissen wird geschlossen, daR TeilchengroRe und TeilchengrORenverteilung des festen Suspendiermittels die Stabilitat der Suspension und die TeilchengroRe des PS beeinflussen. Parallel zur Verringerung der TeilchengroRe des TCP nimmt auch die des PS ab. Die Teilchen-groBe von in-situ-ausgefalltem TCP ist erheblich kleiner als die von handelsiiblichem TCP, weshalb sich mit einer geringeren Menge von in-situ-ausgefalltem TCP PS mit der gleichen TeilchengroRe wie bei Verwendung von handelsiiblichem TCP herstellen 1aRt. Dadurch ergeben sich Einsparungen bei der Produktion und reinere Produkte.
In this study, the pervaporation behaviour of azeotrope-forming methanol-carbontetrachloride binary mixture at different compositions was investigated at 30°C and 45°C through LDPE membranes with two different melt flow indices for two different thicknesses. Experimental fluxes and selectivities for methanol and carbontetrachloride were determined. Theoretical calculations for fluxes based on a solution-diffusion model as developed by Yeom and Huang using Fujita's free volume approach and Flory-Huggins thermodynamics showed deviations from the experimental results. Experimental fluxes were decomposed into sorption and diffusion terms to discuss the effects of experimental conditions.
Commercially available diethyl, dicetyl, and dimyristyl peroxydicarbonate initiators are investigated in a commercial PVC suspension polymerization recipe. Diethyl peroxydicarbonate, which is formed in situ by the reaction of hydrogen peroxide, lime, and ethylchloroformate, produced PVC with less "fish-eyes", whereas it has the disadvantage of being toxic and gives inconsistent polymerization times, therefore the reactor efficiency decreases. Dicetyl and dimyristyl peroxydicarbonates are solid, less toxic materials easy to handle, therefore, when these initiators are used, consistency between batches is obtained. However, PVC with coarse particle sizes containing considerable amounts of "fish-eyes" is obtained, which eventually causes processing problems. It is found that particle coarsening occurs as a result of water soluble impurities of initiators, and "fish-eyes" occur as a result of morphological changes. When dicetyl and dimyristyl type initiators are used, the number of non-porous PVC particles increases. This structure heterogeneity causes formation of ungeltified spots, so-called "fisheyes", during processing. It is found that the non-porous particles are formed due to accumulation of an excessive amount of initiator in a single vinyl chloride monomer droplet.When the distribution of these solid initiators is homogenized by adding them in solution, the formation of non-porous particles is inhibited. However, the coarsening effect still remains, which could be eliminated by extraction of initiator solutions with water just before they are fed to the reactor. Extraction also decreases the amount of crust formation. ZUSAMMENFASSUNG Handelsiibliche Diethyl-, DicetyJ-und Dimyristylperoxydicarbonat-Initiatoren wurden in einem technischen PVC-SuspensionspolymerisationsprozeR verwendet. Diethylperoxydicarbonat, das aus Wasserstoffperoxid, Chlorameisenstiureethylester und Kalk in situ hergestellt wurde, fiihrte zu einem PVC mit wenigen ,,Fischaugen", jedoch erwiesen sich dessen Toxizitat und die ungleichmaRigen, den Reaktorwirkungsgrad herabsetzenden Polymerisationszeiten als nachteilig. Dicetyl-und Dimyristylperoxydicarbonat 0 1991 Hiithig & Wepf Verlag, Basel CCC 0003-3146/91/$04.00 99 C. Arslanalp, E. Erbay, T. BilgiG 0. T. Savayqisind weniger giftige, leicht handhabbare Feststoffe, die, als Initiator, verwendet zu wesentlich gleichmafligeren Produkten fiihren; man erhalt ein grobkorniges PVC, das jedoch relativ viele ,Fischaugen" enthalt, wodurch moglicherweise Verarbeitungsprobleme verursacht werden konnen. Es konnte gezeigt werden, da8 die Vergroberung der PVC-Partikel auf wasserldsliche Verunreinigungen im Initiator und das Auftreten von ,,Fischaugen" auf morphologische Veranderungen zuriickzufiihren sind. Bei Verwendung von Dicetyl-und Dimyristylperoxydicarbonat steigt die Anzahl der nicht-porosen PVC-Teilchen an. Diese Strukturinhomogenit&t fiihrt beim Verarbeiten zur Bildung von nicht erstarrenden Bereichen, den sogenannten ,,Fischaugen". Es konnte gezeigt werden, daf3 diese nicht-porosen Teilchen durc...
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