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1965 Volume 7 Issue 6
1965, 7(6): 373-385
Abstract:
In polyesterification, the action of alcohol as a carrier of H+-ion was supposed to be negligable, in contrast to the result obtained by Tang Au-Ching. A new hypothesis of polyesterification was then suggested.This mechanism can be used to explain some other types of esterification as well. Favourable results were obtained even if p (the percent of the theoretical degree of reaction) is greater than 91%. In the hydrolysis of esters by using strong or weak acid as catalysts, results obtained were found to be better than those obtained by previous authors.
In polyesterification, the action of alcohol as a carrier of H+-ion was supposed to be negligable, in contrast to the result obtained by Tang Au-Ching. A new hypothesis of polyesterification was then suggested.This mechanism can be used to explain some other types of esterification as well. Favourable results were obtained even if p (the percent of the theoretical degree of reaction) is greater than 91%. In the hydrolysis of esters by using strong or weak acid as catalysts, results obtained were found to be better than those obtained by previous authors.
MUTUAL INFLUENCE BETWEEN THE EFFECTS OF RADIATION AND THE CRYSTALLIZATION PROPERTIES OF POLYETHYLENE
1965, 7(6): 386-395
Abstract:
1．The samples of polyethylene irradiated with 1，20，50，1 00，and 200 megarad γ一ray were crystallized from dilute xylene solutions under the same conditions．The mot-phology of a series of crystals obtained changes regularly as the dose increases．Below the gel point,single crystals could be obtained． Beyond this point，dendritic crystals (becoming more and more irregular with increasing dose) were obtained．But when the crystallizing temperature was lowered or the cooling rate Was decreased，regular dendritic crystals or even single crystals could again be obtained．Therefore this change of morphology with increasing dose is due not to the change of the structure of the mole-cules，but to the increasing of the degree of supersatu．ration during crystallization．The higher the gel fraction is，the higher is the degree of supersaturation．2．Three kinds of typical crystalline morphology(they belong tO the linear，bran-ched，and three-dimensional network molecules) were observed from irradiated poly-ethylene．This indicates that within suitable range of dose．these three kinds of mole-cules do exist in irradiated polyethylene at the same time．3． The crystallization process of the polymer from dilute solution is also a process of spontaneous separation of the unlike molecules and a process of congregation of the like molecules．4． Single crystals of polyethylene prepared under the same conditions had been ir-radiated separately with 5，20，50，100，and 200 megarad γ-ray．The morphology of these irradiated crystals was studied with an electron microscope, Some of them re-mained unchanged，but．there were Iots of wrinkles on the others．Moreover，even in the same single crystal，many wrinkles were found in some sectors，but none in the others． The unequal distribution of the wrinkles indicates that a perfect crystal lattice has higher resistance to γ-radiation．It also indicates that every sector in a hollow pyramid crystal is a structural unit of more perfect crystalline lattice．
1．The samples of polyethylene irradiated with 1，20，50，1 00，and 200 megarad γ一ray were crystallized from dilute xylene solutions under the same conditions．The mot-phology of a series of crystals obtained changes regularly as the dose increases．Below the gel point,single crystals could be obtained． Beyond this point，dendritic crystals (becoming more and more irregular with increasing dose) were obtained．But when the crystallizing temperature was lowered or the cooling rate Was decreased，regular dendritic crystals or even single crystals could again be obtained．Therefore this change of morphology with increasing dose is due not to the change of the structure of the mole-cules，but to the increasing of the degree of supersatu．ration during crystallization．The higher the gel fraction is，the higher is the degree of supersaturation．2．Three kinds of typical crystalline morphology(they belong tO the linear，bran-ched，and three-dimensional network molecules) were observed from irradiated poly-ethylene．This indicates that within suitable range of dose．these three kinds of mole-cules do exist in irradiated polyethylene at the same time．3． The crystallization process of the polymer from dilute solution is also a process of spontaneous separation of the unlike molecules and a process of congregation of the like molecules．4． Single crystals of polyethylene prepared under the same conditions had been ir-radiated separately with 5，20，50，100，and 200 megarad γ-ray．The morphology of these irradiated crystals was studied with an electron microscope, Some of them re-mained unchanged，but．there were Iots of wrinkles on the others．Moreover，even in the same single crystal，many wrinkles were found in some sectors，but none in the others． The unequal distribution of the wrinkles indicates that a perfect crystal lattice has higher resistance to γ-radiation．It also indicates that every sector in a hollow pyramid crystal is a structural unit of more perfect crystalline lattice．
1965, 7(6): 396-402
Abstract:
In order to find polymerization conditions for polycetyl methacrylate with homo-geneous molecular weight in higher conversion，we have studied the solution polymeriza-tion of cetyl methacrylate in carbon tetrachloride，chloroform，benzene，and sym-tetra-chloroethane．From the experimental data，the following conclusions can be drawn：(1)the chain transfer constants of the solvents selected above are lower than those jn the polymeriza-tion of methyl methacrylate under similar conditions；(2)the solution polymerization rates of cetyl methacrylate in the four given solvents are nearly the same；(3)in higher con-versions，the molecular weights of polycetylmethacrylate depend mainly on the chain transfer constants of the solvents，but under certain conditions the viscosity effect induced by polymeric molecular shape in the solvents might have some influence on the molecular weights of the polymer obtained；(4) homogeneity of the molecular weight of the poly-met is related probably to the polymeric molecular shape in the solvents，but not to the apparent viscosity of the solution．
In order to find polymerization conditions for polycetyl methacrylate with homo-geneous molecular weight in higher conversion，we have studied the solution polymeriza-tion of cetyl methacrylate in carbon tetrachloride，chloroform，benzene，and sym-tetra-chloroethane．From the experimental data，the following conclusions can be drawn：(1)the chain transfer constants of the solvents selected above are lower than those jn the polymeriza-tion of methyl methacrylate under similar conditions；(2)the solution polymerization rates of cetyl methacrylate in the four given solvents are nearly the same；(3)in higher con-versions，the molecular weights of polycetylmethacrylate depend mainly on the chain transfer constants of the solvents，but under certain conditions the viscosity effect induced by polymeric molecular shape in the solvents might have some influence on the molecular weights of the polymer obtained；(4) homogeneity of the molecular weight of the poly-met is related probably to the polymeric molecular shape in the solvents，but not to the apparent viscosity of the solution．
1965, 7(6): 403-414
Abstract:
The exchange velocities of some anion exchange resins were determined．It includes the following： (1) 3，5一Dinitrobenzoic acid was adsorbed by the exchanger made by the condensa—tion of one mole of tetraethylene pentamine and different amounts(2.5—3.0 moles) of epichlorohydrin； (2) Acetic acid was adsorbed by the exchanger of different particle size (0.315—0.630 mm)； (3) Different acids such as formic，acetic，caproic，hydrochloric，and 3，5-dinitro-benzoic acid were adsorbed by the exchangers； (4) 3，5-Dinitrobenzoic acid was adsorbed by the exchangers of tetraethylene pen-tamine—epichlorohydrin and its alkylated and quaternized products； (5) 3，5-Dinitrobenzoic acid was adsorbed by several modified resins of tetra-ethylene pentamine．epichlorohydrin． Two different methods (the limited batch method and the batch method) were used to determine the exchange velocity of the anion exchange resins，the results showed that the exchange rates were identical when the concentration of the hydrochloric acid was maintained at about 0.032 N．
The exchange velocities of some anion exchange resins were determined．It includes the following： (1) 3，5一Dinitrobenzoic acid was adsorbed by the exchanger made by the condensa—tion of one mole of tetraethylene pentamine and different amounts(2.5—3.0 moles) of epichlorohydrin； (2) Acetic acid was adsorbed by the exchanger of different particle size (0.315—0.630 mm)； (3) Different acids such as formic，acetic，caproic，hydrochloric，and 3，5-dinitro-benzoic acid were adsorbed by the exchangers； (4) 3，5-Dinitrobenzoic acid was adsorbed by the exchangers of tetraethylene pen-tamine—epichlorohydrin and its alkylated and quaternized products； (5) 3，5-Dinitrobenzoic acid was adsorbed by several modified resins of tetra-ethylene pentamine．epichlorohydrin． Two different methods (the limited batch method and the batch method) were used to determine the exchange velocity of the anion exchange resins，the results showed that the exchange rates were identical when the concentration of the hydrochloric acid was maintained at about 0.032 N．
1965, 7(6): 448-456
Abstract:
By considering characteristics of cydo—copolymerization，the composition equation at low conversion was derived in the following form：where [M] and [B] represent the concentrations of diene and the vinyl monomer respec-tively，[M]cop and [B]cop the concentrations of diene and vinyl segment in the copolymer，and R1 and R2 represent the relative reactivity ratio of diene and vinyl monomer respec-tively．When [M]=[B]，then R1 becomes the rate ratio of radical M·or m·attacking diene (including monomolecular and bimolecular mechanism) and vinyl monomer；and R2 becomes the rate ratio of radical B attacking vinyl monomer and diene (including two kinds of mechanism)．By ap-piing the above equation，values of R1 and R2 for 12 sets of monomer pairs were obtained and found to be rather the best values with a permissible range of error．
By considering characteristics of cydo—copolymerization，the composition equation at low conversion was derived in the following form：where [M] and [B] represent the concentrations of diene and the vinyl monomer respec-tively，[M]cop and [B]cop the concentrations of diene and vinyl segment in the copolymer，and R1 and R2 represent the relative reactivity ratio of diene and vinyl monomer respec-tively．When [M]=[B]，then R1 becomes the rate ratio of radical M·or m·attacking diene (including monomolecular and bimolecular mechanism) and vinyl monomer；and R2 becomes the rate ratio of radical B attacking vinyl monomer and diene (including two kinds of mechanism)．By ap-piing the above equation，values of R1 and R2 for 12 sets of monomer pairs were obtained and found to be rather the best values with a permissible range of error．
1965, 7(6): 457-460
Abstract:
It was found that the influence of different ortho-substituted benzene diazonium fluoroborates with Mohr's salt as redox initiators on the rates of polymerization of acry-lonitrile (AN) obeys the Hammett equation, in which the Taft σ, but not the σ+of Tsuno or Okamoto, should be used.
It was found that the influence of different ortho-substituted benzene diazonium fluoroborates with Mohr's salt as redox initiators on the rates of polymerization of acry-lonitrile (AN) obeys the Hammett equation, in which the Taft σ, but not the σ+of Tsuno or Okamoto, should be used.
TEMPERATURE DEPENDENCE OF THE UNPERTURBED DIMENSION OF POLYDIMETHYLSILOXANE Ⅱ. THE EFFECT OF SOLVENT
1965, 7(6): 461-464
Abstract:
The instrinsic viscosities of five fractions of polydimethylsiloxane in the molecular weight range .Mη= 2.8×105-2.5×106 were determined in two θ-solvents, butanone (Tθ= 20℃) and bromobenzene (Tθ=78℃). Viscometric data of both systems conform to the relationship [η]θ = KθM0.50 with Kθ= 6.80×10-2 and 7.73×10-2 in butanone and bromobenzene respectively. The value of △1n[η]θ/△1nT thus obtained from thevalues of Kθ at two θ-temperatures is 0.71. Using the Flory-Fox theory of intrinsicviscosity, we get d 1n h02/d-dlnT=0.47. The value is higher than that obtained in the ethyl-benzene-diethylphthalate mixed solvent system.
The instrinsic viscosities of five fractions of polydimethylsiloxane in the molecular weight range .Mη= 2.8×105-2.5×106 were determined in two θ-solvents, butanone (Tθ= 20℃) and bromobenzene (Tθ=78℃). Viscometric data of both systems conform to the relationship [η]θ = KθM0.50 with Kθ= 6.80×10-2 and 7.73×10-2 in butanone and bromobenzene respectively. The value of △1n[η]θ/△1nT thus obtained from thevalues of Kθ at two θ-temperatures is 0.71. Using the Flory-Fox theory of intrinsicviscosity, we get d 1n h02/d-dlnT=0.47. The value is higher than that obtained in the ethyl-benzene-diethylphthalate mixed solvent system.
