摘要:

The particle structure of polyvinyl chloride is controlled by the shear field imposed on the monomer droplet and the interfacial behavior of the vinyl chloride/water phases during polymerization. The inter facial tension in the presence of hydroxypropyl methylcellulose (HPMC) was measured as a function of concentration and temperature. The molecular weight distribution of HPMC was determined by coupled GPC-LALLS (low angel laser light scattering) technique. By monitoring the concentration of HPMC in the aqueous phase during polymerization, the coverage powers of HPMC were calculated and compared with the theoretical value based on Langmuir layer consideration. The effects of agitation on resin porosity were also examined. These results are discussed with respect to the particle structure.

ISSN:0022-233X    

DOI:10.1080/00222338408056556

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Three classes of polyoxamides were prepared: homopolymers derived from α-, ω-diaminoalkanes, and 4,4′-diaminodiphenyl-methane, copolymers with an alternating sequence of two different aliphatic diamines and copolymers with a random sequence of two different diamines. For their syntheses a new class of monomers, the diamine bisoxamide diethyl esters, were prepared from α,ω-diamines and oxalic acid chloride ethyl ester. The 22.63 MHz13C-NMR spectra of the polyoxamide solution in fluorosulfonic acid permitted sequence analysis because the carbonyl signals are sensitive to the nature of the neighboring diamine units. In contrast, 9.12 MHz15N-NMR spectra did not give any sequence information. The thermal stability of the polyoxamides was investigated, but differential scanning calorimetry did not give useful information on the crystallinity of the polyoxamides because of their thermal degradation.

ISSN:0022-233X    

DOI:10.1080/00222338408056557

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Uranium (VI) forms an intense yellow-colored complex with N-(thiobenzoyl)-N-phenylhydroxylamine. The complex has maximum absorbance at 410 nm at pH 5.1–5.7. Beer' law is valid up to 29.4 ppm of uranium(VI). The molar absorptivity is 1.87 × 104mol−1cm−1. The effects of diverse ions, stability constants, and the structure of the complex are discussed.

ISSN:0022-233X    

DOI:10.1080/00222338408056558

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The transesterification of dimethyl terephthalate has been studied by measuring the amount of methanol formed as a function of time. The influence of various catalytic systems was investigated with regard to the nature and concentration of the metal ion and temperature. The order of decreasing activity was found to be Pb, Zn, Mn, Sn, Sb, Ti, and mixtures of Zn plus Pb and Zn plus Sb were found to be synergistic. The postulate that there is a correlation between the metal oxygen bond and the activity of the catalyst is discussed.

ISSN:0022-233X    

DOI:10.1080/00222338408056559

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Some newer polyamides were synthesized and characterized by their elemental, IR spectral, and thermal analysis. The thermal decomposition of such polymers was investigated by using programmed and isothermal thermogravimetric analysis. Reaction rates and overall activation energies were calculated from isothermal weight loss studies. Differential thermal analysis was used to determine the melting points of polyamides. These results indicate that the polymers decompose above 185°C the steep weight loss occurred mainly between 250 and 310°C. Most of the polyamides were soluble in organic solvents and exhibited inherent viscosity in the range of 0.12 to 0.42.

ISSN:0022-233X    

DOI:10.1080/00222338408056560

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

When any degree of inhomogeneity exists in a copolymer—regardless of source-distributions of dyads and triads will deviate from values calculated under the assumption of homogeneity. For copolymer systems described by the Wall equation (r1r2= 1), the triads (111) and (222) will always be higher than predicted; (112 and (121) will be less than predicted at m1<0.33; greater when m1>0.33. The triads (221) and (212) will be less when m1<0.67, greater at m1<0.67. When nonhomogeneity is taken into account, and the probability equations adjusted accordingly, monomer distributions can be predicted accurately from simple Markovian statistics. Further, in the presence of inhomogeneity, pseudore-activity ratio products calculated from dyads will always be fallaciously high. Published data for olefin copolymerizations using heterogeneous Ziegler-Natta catalysts confirm that these systems follow the Wall equation but are nonhomogeneous.

ISSN:0022-233X    

DOI:10.1080/00222338408056561

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Grafting of nylon 6 fiber was carried out using ethyl methacrylate (EMA) as the monomer in various water-alcohol systems (i.e., water-methanol, water-ethanol and water-n-propanol; water-alcohol ratio 1:1) at 70°C using a carbon arc lamp as the source of photochemical initiation. Percent graft add-on (% GAO) increases continuously and linearly with an increase in monomer concentration irrespective of the media used. The % GAO, however, decreases with an increase in the alkyl chain length of the alcohol used in the following order: water-methanol > water-ethanol > water-n-propanol. With an increase in the time period of grafting, % GAO and total polymer yield (% TPY) increase continuously in all three media whereas the grafting efficiency (GE) first increases and then falls after reaching a maximum level. Although a similar trend is maintained in the three systems, there is a decrease in overall % TPY and % GAO from the water-methanol system to the water-n-propanol system through the water-ethanol system.

ISSN:0022-233X    

DOI:10.1080/00222338408056562

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The kinetics of the thermal polymerization of ethyl acrylate initiated by Mn3+in sulfuric acid at 50 to 60°C have been studied. The rate of monomer disappearance is found to bear a square dependence on [M] and is independent of both [Mn3+] and [H+]. The rate of manganic disappearance is found to be directly proportional to [M], [Mn3+], and [H+]. The degree of polymerization is directly proportional to [M] and inversely proportional to [Mn3+] and [H+]. A kinetic scheme involving the initiation and termination of polymerization by Mn3+is proposed.

ISSN:0022-233X    

DOI:10.1080/00222338408056563

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Ferric acetylacetonate has been utilized as an initiator for effecting grafting of methyl methacrylate (MMA) and ethyl methacrylate (EMA) onto Himachali wool in aqueous medium. The extent of grafting and grafting efficiency have been determined as functions of various reaction variables that influence the grafting reactions. Nitric acid was found to catalyze the graft copolymerization. Rate of grafting (Rp) and induction period (Ip) of MMA and EMA have been determined as a function of total initial monomer concentration. MMA was found to be more reactive than EMA toward graft copolymerization. With MMA, the induction period (Ip) was found to increase with increasing [MMA], while the reverse was true with EMA. A plausible mechanism for graft copolymerization has been suggested to explain the relative reactivities of MMA and EMA toward grafting onto wool.

ISSN:0022-233X    

DOI:10.1080/00222338408056564

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Polymerization of methyl methacrylate was carried out at 55 and 65°C using benzoyl peroxide as initiator in the presence of the fol-lowing additives: (a) cholesteric compounds like cholesterol, cho-lesteryl acetate, cholesteryl caprylate, cholesteryl stearate, choles-teryl chloride, cholesteryl laurate, cholesteryl oleyl carbonate, and cholesteryl 2-ethylhexyl carbonate, (b) a nematic liquid crystal, N-(p-methoxy benzylidene)-p-butyl aniline, and (c) rodlike molecules like 2-butynediol and diacetylene diol. The rates of polymerization, activation energies, molecular weights, and tacticities of the poly-mer are discussed in the light of monomer + additive interactions. It is found that monomer-additive complexes affect the polymerization rates.

ISSN:0022-233X    

DOI:10.1080/00222338408056565

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor