摘要:

AbstractThe two‐phase equilibrium in the system polystyrene (PS)‐liquid sulfur dioxide [SO2(l)] was investigated, mainly at room temperature. The system consisted of an upper PS‐rich phase, concentration (30–50)% depending on the way of preparation, and a lower phase containing less than 1% PS. The range of molecular weights of the PS samples used was 22,000–350,000 (M̄w). PS with an M̄wvalue of 22,000 dissolved homogeneously in SO2(l). In systems forming two phases a fractionation of PS with respect to molecular weight was observed. The M̄wvalue of the PS fraction dissolved in the lower PS lean phase was always substantially lower than that of the upper phase. When increasing the temperature to 90–95°C, the two phases disappeared and the PS component formed a jellylike mass with a very low solubility in SO2(l). Also in the supercritical dense SO2gas, the solubility of PS was a few tenths of a percent only. Experiments with Soxhlet extraction indicated an extractability o

ISSN:0021-8995    

DOI:10.1002/app.1979.070231001

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractThe products obtained on degradation of poly(m‐N,N‐dimethylaminostyrene) in vacuo are described. The effects of molecular weight and pyrolysis temperature are discussed and compared with those observed for polystyrene under similar conditions. The liquid products of pyrolysis were separated and identified by gas–liquid chromatography using Kovats' retention index and by mass spectrometry. Product analysis revealed significant differences between the products of degradation of the two polymers, and mechanisms involving N‐alkyl and N‐aryl bond scission are proposed and discussed to account for this behavior. The degradation behavior of poly(m‐N,N‐dimethylaminostyrene) shows a marked molecular weight dependence. This is discussed in terms of the differences in the physical forms of the polymer produced on heating, namely, formation of a “melt” or retention of the original “fibrous” identity. Quantitative studies on the liquid fraction are also described and the behavior compared with results ob

ISSN:0021-8995    

DOI:10.1002/app.1979.070231002

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractThe effect of extent of degradation of poly(m‐N,N‐dimethylaminostyrene) on the quantity and molecular weight of the residue is described. Comparative studies on polystyrene and poly(m‐N,N‐dimethylaminostyrene) have indicated significant differences between the two polymers. Torsional braid analysis has shown the crosslinked residue from poly(m‐N,N‐dimethylaminostyrene), produced at temperatures greater than 150°C, to be obtained on the heating cycle rather than the cooling cycle, and mechanisms to account for this phenomenon are discussed. The physical form of the residue has been found to be molecular weight dependent, and this has been discussed in terms of the differences in “melt temperature” relative to the “onset temperature” for crosslinking. The quantity and composition of the fraction volatile at pyrolysis temperature, involatile at ambient temperature are discussed. The components of this fraction were identified by GPC and mass spectrometry and include oligomers containing the secondary amino function. Mechanisms involving N‐alkyl and N‐aryl scission are proposed to account f

ISSN:0021-8995    

DOI:10.1002/app.1979.070231003

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractThe products obtained on vacuum pyrolysis of poly(p‐N,N‐diethylaminostyrene) are described. The effect of sample molecular weight and pyrolysis temperature are compared with that observed for polystyrene degraded under identical conditions. The liquid products were separated using gas–liquid chromatography and identified using Kovat's retention index and mass spectrometry. Significant differences were found between the products arising from the two polymers which are discussed in terms of mechanisms involving N‐alkyl and N‐aryl bond scission and the subsequent reactions of the generated radicals. Comparative quantitative studies are described and

ISSN:0021-8995    

DOI:10.1002/app.1979.070231004

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractComparative studies were made of the residue and the fraction volatile at pyrolysis temperature, involatile at ambient temperature obtained from polystyrene and poly(p‐N,N‐diethylaminostyrene) degraded under identical conditions. Poly(p‐N,N‐diethylaminostyrene) yielded a crosslinked glassy residue after pyrolysis at temperatures greater than 250°C, and crosslinking is accompanied by N‐alkyl group scission as shown by mass spectrometry. The components of the fraction volatile at pyrolysis temperature, involatile at ambient temperature were separated and identified by GPC and mass spectrometry. Mechanisms involving N‐alkyl and N‐aryl bond scission are proposed to account for the observed products. Quantitative studies on the effect of pyrolysis temperature and polymer molecular weight on the residue and the volatile fraction are described and discussed. No molecular weight dependence was observed for this system in the

ISSN:0021-8995    

DOI:10.1002/app.1979.070231005

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractThe major degradative process in γ‐irradiated cellulose acetate is chain scission. For the dry powder theGsvalue (number of scissions per 100 eV of energy absorbed) was found to be 7.1. The water‐swollen material was found to degrade at the higher rate ofGs= 9.45. Additions of ethanol and methanol to the water brought about reductions inGs, whereas dissolved nitrous oxide produced an increase inGs. The useful life of cellulose acetate reverse osmosis membranes exposed to γ radiation was estimated by observations of the water permeation rate during irradiation. Membrane breakdown occurred at 15 Mrad in pure water, but the dose to breakdown was extended to 83 Mrad in the presence of 4% met

ISSN:0021-8995    

DOI:10.1002/app.1979.070231006

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractThe effects of aromatic, naphthenic, and paraffinic oils on the dynamic mechanical behavior of an EPDM rubber (Nordel 1560) have been investigated as have the influences of oil level, carbon black loading, and peroxide crosslinking.

ISSN:0021-8995    

DOI:10.1002/app.1979.070231007

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractZeta potential measurements by the streaming current method were performed on pulp (DP) fibers with or without irreversibly adsorbed monolayers of cationic polyelectrolyte. Factors affecting the electrokinetic properties of these fibers, such as the amount of adsorbed polymer, the polymer molecular weight (Mn50,000 and 200,000), ionic strength (10−5∼ 10−2MKCl), and the pH of the streaming medium (KCl solution), were examined. As the amount of adsorbed polymer increased, the negative zeta potential of the fibers decreased until the polarity of the zeta potential was reversed to the positive side. A marked change in the value of zeta potential was not observed when the formation of the saturated monolayer was completed. The zeta potential also varied in proportion to an increase in the amount of polymer adsorbed. Experimental results are interpreted with reference to the origin of the surface charge, the amphoteric nature of the surface, the modes of adsorption, and the adsorbed polymer chain configuration. Possible effects of the adsorbed monolayer formation on the structural change of the electric double layer at the fiber surface are discussed. It is concluded that the formation of a monolayer of cationic polyelectrolytes on the negatively charged cellulose fibers under the condition ofk1>k2(part I) provides a means to arbitrarily control the charge of the fibers until formation of a saturated mono

ISSN:0021-8995    

DOI:10.1002/app.1979.070231008

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractStudies were carried out on grafting of various vinyl monomers to nitrocellulose by ceric ions. It was observed that graft copolymerization occurred only with methyl methacrylate (MMA) and methyl acrylate monomer. The variables such as initiator concentration, monomer concentration, time of grafting, and nitrocellulose content on grafting of MMA are discussed. By hydrolyzing away the nitrocellulose backbone, the grafted poly(methyl methacrylate) branches were isolated and the>co peak at 1740 cm−1in the infrared spectra of these isolated branches gave definite evidence of grafting. The molecular weight of isolated branches has been determined by viscometry. The probable mechanism of grafting may be at the α‐carbon atom of primary alcohol or at a C2‐C3glycol group of the anhydro glucose unit or at the hemiacetal group of the end unit of nitrocellulose, as nitrocellulose is formed by the partial nitration of cotton c

ISSN:0021-8995    

DOI:10.1002/app.1979.070231009

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractThe technique for staining unsaturated additives within cotton fibers reacts osmium tetroxide with a sorbyl moiety which has been attached to the cellulose chain. Resulting electron micrographs indicate that contrast is considerably enhanced. Measurements of fibrillar size averaged 0.30 nm, closely approximating the values in the literature.

ISSN:0021-8995    

DOI:10.1002/app.1979.070231010

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY