ISSN:0022-233X    

DOI:10.1080/00222338108063215

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Partially neutralized liquid polybutadiene treated with succinic anhydride (SA), that is, PBSA(PNa), was prepared by partial neutralization with NaOH of adduct polymer (PBSA) from liquid polybutadiene and SA (PNa means that PBSA was partially neutralized with NaOH). PBSA(PNa) was found to act as an effective W/O∼type emulsifier for vinyl monomers such as styrene, MMA, acrylonitrile, and ethylene glycol dimethacrylate. Inverted emulsions having very low viscosity were prepared from the vinyl monomers with various amounts of PBSA(PNa). By polymerization, the emulsions were transformed to a white solid which were dry to the touch. The water-containing polymers obtained are characterized by the properties of showing a very high rate of water loss. The higher the amounts of PBSA-(PNa) and of water in the polymer, the more rapid the water loss becomes. Most of physical properties increase in value by removing water. Further improvement in physical properties is observed by reinforcing with glass fiber; the flexural and impact strengths especially increase remarkably.

ISSN:0022-233X    

DOI:10.1080/00222338108063216

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Cellulose peroxides derived from various cellulose derivatives with hydrogen peroxide were investigated. Fibrous carboxy-methyl cellulose, periodic acid-oxidized cellulose, and methyl vinyl ketone-treated cellulose were employed as cellulose derivatives. Carboxyl and carbonyl groups in the cellulose derivatives were believed to react with hydrogen peroxide to form peroxides with structures of peracid and α-hydroxyhydroperoxide types, respectively. The decomposition of the cellulose peroxides and their abilities to initiate grafting reaction were examined.

ISSN:0022-233X    

DOI:10.1080/00222338108063217

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Graft copolymerization of methyl acrylate (MA) onto cellulose has been studied in the presence of Fe(acac)s, Al(acac)s, and Zn(acac)z as initiators in aqueous medium. The percentage of grafting has been determined as a function of concentration of initiators and monomer, reaction time, and temperature. A plausible mechanism for grafting involving prior complex formation between metal chelates and monomers has been suggested. The free radical mechanism for grafting was confirmed by carrying out several experiments in the presence of chain transfer agents such as CCl4, CHCl3, CH3CH2CH2SH, and EtsN. All these additives, with the exception of EtsN, were found to suppress grafting. The relative reactivity of different metal chelates toward grafting has been determined and was found to follow the order: Fe(acac)s > Zn(acac)z > Al(acac)s.

ISSN:0022-233X    

DOI:10.1080/00222338108063218

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The mechanism of grafting of polystyrene on a polybutadiene (PB) backbone during the preparation of impact-resistant polystyrene was studied by withdrawing samples during propolym-erization from beginning of the reaction to about 25% conversion. Good separation of the “elastomer and graft” fraction of the polymer from the free polystyrene part could be achieved by using 0.24 volume fraction of methanol in (MEK + benzene) + methanol solvent-nonsolvent. IR analysis of the grafted fraction showed that the microstructure of the elastomer remained unaltered. The unsaturation of the samples studied through the bromine number as well as by the perbenzoic acid number was also found to remain unchanged. Formation of free polystyrene started with the onset of polymerization and was faster. During prepolymerization, 80% of styrene converted constantly to form free polystyrene and 20% went into the grafted polymer. The results indicate that grafting is initiated through proton abstraction at the α-carbon of butadiene, most probably by initiator radicals. The grafted polystyrene chains possibly are shorter than free polystyrene chains.

ISSN:0022-233X    

DOI:10.1080/00222338108063219

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Graft polymerization of methyl methacrylate onto natural and modified wools was performed using the Na2S2O3-H2O2redox system as initiator. High graft yields were rapidly obtained with natural, reduced, oxidized wools and, to a less extent, with S-carboxymethylated fibers. S-Aminoethylated, deamined, and some acetylated wools were less easily grafted, and practically no grafting was observed with dinitrophenylated wools. The IR and NMR analysis of isolated polymethacrylic chains did not reveal any stereoregulating effect on methyl methacrylate polymerization due to crystalline components of wool structure. The percentages of graft-on and the molecular weights of the separated poly(methyl methacrylates) were found to be dependent on chemical groups in wool and also on the extent of oxidative processes and of competitive homopolymerization. There is some reason to believe that a part of short polymer chains was not truly grafted but only entwisted in the wool structure.

ISSN:0022-233X    

DOI:10.1080/00222338108063220

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Anionic polymerization of p-triphenyltin styrene (TPSnS) was investigated under high vacuum conditions (∼ 10−6mmHg). TPSnS has been readily polymerized by sodium naphthalide, potassium naphthalide, or sodium salts of α-methylstyrene oligomers to form “living polymers” at low temperature (≤ -30°C). The addition of α-methylstyrene to these living systems gave the block copolymers, TPSnS-block α-methylstyrene. The Mark-Houwink values of K and a, determined in tetrahydrofuran, were K = 0.59 × 10−4and a = 0.68 where M was Mn, indicating that the polymer was moderately coiled in this solvent. Some physical properties of poly(TPSnS) were examined.

ISSN:0022-233X    

DOI:10.1080/00222338108063221

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

It was demonstrated that highly hindered bisphenols could be used to produce polyesters of moderate molecular weight. Bisphenols linked in the 4 and 4′ or the 2 and 2′ positions and substituted in positions ortho and para to the phenolic hydroxyl groups with methyl or tertiary butyl groups (these bisphenols are now used as very effective antioxidants) formed polymers, their reactivity depending more on the nature of the group linking the two phenyl rings than on the steric effects of the ortho substi-tuents. Bisphenols linked in the 2 and 2′ positions and containing bulky electron-withdrawing groups were found to be least effective as condensation monomers although successful polymerization to moderate molecular weight could be achieved using me it polycondensation techniques.

ISSN:0022-233X    

DOI:10.1080/00222338108063222

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The structural changes in PVC during thermal dehydrochlorination in pyridine have been investigated. From gel permeation chromatography analyses, chain scission and cross-linking reactions were observed. Cross-linking increased with an increase in reaction time and temperature, whereas the chain scission increased with dilution of the reaction solution. Infrared spectros-copy indicated the presence of conjugated double bond sequences in polymeric chains. Polyene sequences were analyzed by ultraviolet spectroscopy. The length of the polyene sequences and the total number of conjugated double bonds increased with reaction time. An increase in dehydrochlorination temperature lowered the fraction of long polyene sequences, and thus the discoloration. Dilution of the reaction solution decreased the polyene sequence lengths as well as the total number of conjugated double bonds. Shorter polyenes were maximum and their proportion decreased with increase in their length.

ISSN:0022-233X    

DOI:10.1080/00222338108063223

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

This paper deals with kinetic studies of the 2,5-xylenol and formaldehyde reaction catalyzed by hydrochloric acid. The catalyst concentrations used were 0.008, 0.012, 0.02, and 0.04 N. The investigations were carried out at 65, 70, 75, and 80°C. It was observed that the reaction follows a second-order rate law. The rate of reaction was found to increase with an increase in acid concentration. The overall rate constant was resolved into stepwise rate constants. It is a two-step reaction, the second step of the reaction being a rapid follow-up of the first step. Activation parameters for the overall reaction have been calculated, and a mechanism conforming to the experimental observations is suggested.

ISSN:0022-233X    

DOI:10.1080/00222338108063224

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor