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1987 Volume 5 Issue 1
1987, 5(1): 1-6
Abstract:
A method of comparative DSC technique is proposed for excess enthalpy relaxation study. The essential of the comparative DSC technique consists of comparing the enthalpy relaxation behavior of an aged sample with a quenched sample as reference. The accuracy of comparison is improved because of simultaneous measuring of the sample and reference which makes noise of the apparatus subtractive. This technique has been applied to studying the influence of crosslinking on the enthalpy relaxation behavior of epoxy resins. The effect of crosslinking on the kinetics of enthalpy relaxation of epoxy resins is discussed.
A method of comparative DSC technique is proposed for excess enthalpy relaxation study. The essential of the comparative DSC technique consists of comparing the enthalpy relaxation behavior of an aged sample with a quenched sample as reference. The accuracy of comparison is improved because of simultaneous measuring of the sample and reference which makes noise of the apparatus subtractive. This technique has been applied to studying the influence of crosslinking on the enthalpy relaxation behavior of epoxy resins. The effect of crosslinking on the kinetics of enthalpy relaxation of epoxy resins is discussed.
1987, 5(1): 7-11
Abstract:
The absorption and fluorescence spectra of dibenzoyl methane have been studied. From the absorption spectra it was found that there are two peaks locating at 252 nm and 340 nm, respectively, similar to that of o-hydroxy benzophenone which can form intra-molecular hydrogen bond. Besides, an uncommonly large Stoke's shift of fluorescence can be observed in fluorescence spectra. The photostabilizing effects of dibenzoyl methane and UV-531 on the photodegradation of poly (cis-1, 4-butadiene) in solution have been investigated and compared.A possible mechanism was discussed.
The absorption and fluorescence spectra of dibenzoyl methane have been studied. From the absorption spectra it was found that there are two peaks locating at 252 nm and 340 nm, respectively, similar to that of o-hydroxy benzophenone which can form intra-molecular hydrogen bond. Besides, an uncommonly large Stoke's shift of fluorescence can be observed in fluorescence spectra. The photostabilizing effects of dibenzoyl methane and UV-531 on the photodegradation of poly (cis-1, 4-butadiene) in solution have been investigated and compared.A possible mechanism was discussed.
1987, 5(1): 12-19
Abstract:
The present article deals with the exchange process of bivalent metal ions, such as Zn2+, Cd2+ and Hg2+, etc., taken up by non-crosslinked earboxylated polypropylene (CPP) resin. The control factor of the exchange rate deduced from the kinetic data is governed basically by the chemical reaction rather than the mass transfer effect particle diffusion and/or liquid film diffusion. In solution, all the graft chains in the outer shell of a CPP resin could form a "quasi-macromolecular solution" domain. This opinion further demonstrates the structural pattern of CPP resin proposed in earlier paper[1].
The present article deals with the exchange process of bivalent metal ions, such as Zn2+, Cd2+ and Hg2+, etc., taken up by non-crosslinked earboxylated polypropylene (CPP) resin. The control factor of the exchange rate deduced from the kinetic data is governed basically by the chemical reaction rather than the mass transfer effect particle diffusion and/or liquid film diffusion. In solution, all the graft chains in the outer shell of a CPP resin could form a "quasi-macromolecular solution" domain. This opinion further demonstrates the structural pattern of CPP resin proposed in earlier paper[1].
1987, 5(1): 20-25
Abstract:
Triad sequence distributions in a series of P(AM/AA) with different AA% were calculated from copolymerization reactivity ratio r1 and r1 based on first order Markov statistic model, and the calculated data compared with observed ones from 13C-NMR spectra showed good agreement with each other. The sequence distribution in P(AM/AA) obtained under our experimental conditions fits in with first order Markov statistic model. A significant sequence structure difference was observed between P(AM/AA) and alkaline hydrolyzed polyacrylamide,ABA triad (acrylate unit center),AAA and AAB triads (acrylamide unit center) dominated in hydrolyzed ones.
Triad sequence distributions in a series of P(AM/AA) with different AA% were calculated from copolymerization reactivity ratio r1 and r1 based on first order Markov statistic model, and the calculated data compared with observed ones from 13C-NMR spectra showed good agreement with each other. The sequence distribution in P(AM/AA) obtained under our experimental conditions fits in with first order Markov statistic model. A significant sequence structure difference was observed between P(AM/AA) and alkaline hydrolyzed polyacrylamide,ABA triad (acrylate unit center),AAA and AAB triads (acrylamide unit center) dominated in hydrolyzed ones.
1987, 5(1): 26-33
Abstract:
In order to study the mechanism of the formation of maeroporous copolymer, the overall reaction kinetics, phase separation and gelation of the S/EGDM in the presence of inert solvents and the physical properties of the eopolymer were investigated and compared with the corresponding system of S/DVB and S/DVB/MMA. The formation of the network structure of the macroreticular polymer was studied and a model of the mechanism suggested.
In order to study the mechanism of the formation of maeroporous copolymer, the overall reaction kinetics, phase separation and gelation of the S/EGDM in the presence of inert solvents and the physical properties of the eopolymer were investigated and compared with the corresponding system of S/DVB and S/DVB/MMA. The formation of the network structure of the macroreticular polymer was studied and a model of the mechanism suggested.
1987, 5(1): 34-39
Abstract:
The dielectric loss factor and permittivity of a series of 1, 2-polybutadienes with different contents of 1, 2-units and different contents of syndiotactie 1, 2-units were determined over a frequency range from 30Hz to 100KHz at different temperatures. The WLF equation was evaluated for various samples with Tθ at 100KHz as a reference temperature and the master curves of various samples have been constructed, which are in accordance with those calculated by Havriliak-Negami equation. The frequency dependence of the dielectric relaxation of 1,2-polybutadienes was investigated over a frequency range from 100 Hz to 1012 Hz in lerms of the experimental data and the master curves.
The dielectric loss factor and permittivity of a series of 1, 2-polybutadienes with different contents of 1, 2-units and different contents of syndiotactie 1, 2-units were determined over a frequency range from 30Hz to 100KHz at different temperatures. The WLF equation was evaluated for various samples with Tθ at 100KHz as a reference temperature and the master curves of various samples have been constructed, which are in accordance with those calculated by Havriliak-Negami equation. The frequency dependence of the dielectric relaxation of 1,2-polybutadienes was investigated over a frequency range from 100 Hz to 1012 Hz in lerms of the experimental data and the master curves.
1987, 5(1): 40-44
Abstract:
FeCl3·6H2O, NiCl2, CuCl2, ZnCl2 and CrCl3 have been incorporated into polyphenylquinoxaline by a new method. High-quality, flexible, glass-cast films have been obtained which exhibit increased glass transition temperature and excellent thermal stability. Moduli and tensile strengths of the metal-containing polyphenylquinoxaline films increase surprisingly at elevated temperature. Electrical resistivities of these films fall in the same order range as polyphenylquinoxaline alone. X-ray photoelectron spectroscopic study of metal-containing polyphenylquinoxaline films shows that all metals in these films are present in the ionic state,there is charge transfer between nitrogen of polyphentlquinoxaline and Cu2+,Zn2+ of CuCl2,ZnCl2 containing polyphentlquimoxaline films.
FeCl3·6H2O, NiCl2, CuCl2, ZnCl2 and CrCl3 have been incorporated into polyphenylquinoxaline by a new method. High-quality, flexible, glass-cast films have been obtained which exhibit increased glass transition temperature and excellent thermal stability. Moduli and tensile strengths of the metal-containing polyphenylquinoxaline films increase surprisingly at elevated temperature. Electrical resistivities of these films fall in the same order range as polyphenylquinoxaline alone. X-ray photoelectron spectroscopic study of metal-containing polyphenylquinoxaline films shows that all metals in these films are present in the ionic state,there is charge transfer between nitrogen of polyphentlquinoxaline and Cu2+,Zn2+ of CuCl2,ZnCl2 containing polyphentlquimoxaline films.
1987, 5(1): 45-52
Abstract:
Ni(Ⅱ) naphthenate in hydrogenated gasoline or toluene will appear light green, which is the result of absorption in the red and blue bands of the spectrum. The three peaks caused by the spin-allowed d-d transitions are 403, 680, and 1170nm respectively, and are similar to those of Ni(H2O)6+2. The configuration of Ni(Ⅱ) complex is octabedral.In a two-component system of Ni(naph)2-Al(i-Bu)3, the naphthenate ligand attached to Ni(Ⅱ) can be exchanged for the alkyl group on tri-isobutylaluminium, if Al(i-Bu)3/Ni(naph)2 in a system containing metalalkyl and naphthenate does not exceed the value of 0.53.At a higher ratio,Al(i-Bu)3/Ni(naph)2>0.53,Ni(Ⅱ) is reduced to Ni(I) and Ni(O).In a two-component system Ni(naph)2-BF3·OEt2,a part of the naphthenate can be exchanged for halogen.A new Ni(Ⅱ)complex is formed,which consists of three new d-d bands in the region 360-1660nm.
Ni(Ⅱ) naphthenate in hydrogenated gasoline or toluene will appear light green, which is the result of absorption in the red and blue bands of the spectrum. The three peaks caused by the spin-allowed d-d transitions are 403, 680, and 1170nm respectively, and are similar to those of Ni(H2O)6+2. The configuration of Ni(Ⅱ) complex is octabedral.In a two-component system of Ni(naph)2-Al(i-Bu)3, the naphthenate ligand attached to Ni(Ⅱ) can be exchanged for the alkyl group on tri-isobutylaluminium, if Al(i-Bu)3/Ni(naph)2 in a system containing metalalkyl and naphthenate does not exceed the value of 0.53.At a higher ratio,Al(i-Bu)3/Ni(naph)2>0.53,Ni(Ⅱ) is reduced to Ni(I) and Ni(O).In a two-component system Ni(naph)2-BF3·OEt2,a part of the naphthenate can be exchanged for halogen.A new Ni(Ⅱ)complex is formed,which consists of three new d-d bands in the region 360-1660nm.
1987, 5(1): 53-60
Abstract:
The crystallization kinetics of the copolyester, poly(ethylene terephthalate) (PET) modified by sodium salt of 5-sulpho-isophthalic acid(SIPM), was investigated by means of differential scanning calorimeter. The experimental results and polari-microscopy observation all showed that the introduction of SIPM did not affect the nucleation of crystallization. Within the temperature range between their glass transition temperature Tθ and melting point Tm, the crystallization rate of the copolyester sample decrrased with increasing content of SIPM.The relative crystallization rate constant Z of SIPM/DMT (dimethyl terephthalate)4mol% sample was about 1% pure PET's Z value.For isothermal crystallized copolyester samples,DSC heating curves displayed multi-melting behavior.This was interpreted by molecalar weight fractionation during crystallization and premelting-recrystallization mechanism.This interpretation showed why the second melting point Tm2 will change according to Hoffman-Weeks(H-W) equation[1] and the first melting point Tm1 will increase with increasing SIPM.The principal cause of these phenomena is the high temperature crystallization rate decreases rapidly with increasing SIPM.
The crystallization kinetics of the copolyester, poly(ethylene terephthalate) (PET) modified by sodium salt of 5-sulpho-isophthalic acid(SIPM), was investigated by means of differential scanning calorimeter. The experimental results and polari-microscopy observation all showed that the introduction of SIPM did not affect the nucleation of crystallization. Within the temperature range between their glass transition temperature Tθ and melting point Tm, the crystallization rate of the copolyester sample decrrased with increasing content of SIPM.The relative crystallization rate constant Z of SIPM/DMT (dimethyl terephthalate)4mol% sample was about 1% pure PET's Z value.For isothermal crystallized copolyester samples,DSC heating curves displayed multi-melting behavior.This was interpreted by molecalar weight fractionation during crystallization and premelting-recrystallization mechanism.This interpretation showed why the second melting point Tm2 will change according to Hoffman-Weeks(H-W) equation[1] and the first melting point Tm1 will increase with increasing SIPM.The principal cause of these phenomena is the high temperature crystallization rate decreases rapidly with increasing SIPM.
THERMAL ANALYSIS AND STRUCTURE STUDIES ON THE BLENDS OF LIQUID CRYSTALLINE COPOLYESTERS AND PET, PBT
1987, 5(1): 61-65
Abstract:
The apparent uniform blends of liquid crystalline aromatic copolyesters and semiflexible polyesters PET or PBT were obtained by mechanical mixing in the molten state within certain range of composition.The effects of blending with liquid crystalline components on the structure of homopolyester matrix were examined by thermal analysis and X-ray diffraction. These results suggest that the LC component in the blend may possibly be acting as a nucleating agent, or it may induce axial orientation of molecules promoting the local ordering of matrix.For the blends of PET,these influences mainly display in narrowing the width of cold crystalline peak and enhancing the main peak of x-ray diffraction;and for the blends of PBT,the pre-melting crystalline peak was enhanced.
The apparent uniform blends of liquid crystalline aromatic copolyesters and semiflexible polyesters PET or PBT were obtained by mechanical mixing in the molten state within certain range of composition.The effects of blending with liquid crystalline components on the structure of homopolyester matrix were examined by thermal analysis and X-ray diffraction. These results suggest that the LC component in the blend may possibly be acting as a nucleating agent, or it may induce axial orientation of molecules promoting the local ordering of matrix.For the blends of PET,these influences mainly display in narrowing the width of cold crystalline peak and enhancing the main peak of x-ray diffraction;and for the blends of PBT,the pre-melting crystalline peak was enhanced.
CONFIGURATION OF VO(OR)2Cl-Al(i-Bu)3 CATALYST SYSTEM AND CHARGE DISTRIBUTION OF VANADIUM CENTRAL ION
1987, 5(1): 66-75
Abstract:
According to the caiculation of quantum chemistry it come be deduced that conngurauons or the catalysts VO(OR)2Cl-Al (i-Bu)3, for the alternating Copolymerization of butadiene with propene, the highest reactive configuration was A. When the catalyst complex forms the configuration A, the energy of the system was the lowest; the central vanadium atom had relatively high positive charge and whose frontier orbital overlapped easily with the frontier orbital of butadiene to form coordination complex, so it was concluded from the experimental results and calculations that the configuration of the catalyst of relatively high actibity was A.
According to the caiculation of quantum chemistry it come be deduced that conngurauons or the catalysts VO(OR)2Cl-Al (i-Bu)3, for the alternating Copolymerization of butadiene with propene, the highest reactive configuration was A. When the catalyst complex forms the configuration A, the energy of the system was the lowest; the central vanadium atom had relatively high positive charge and whose frontier orbital overlapped easily with the frontier orbital of butadiene to form coordination complex, so it was concluded from the experimental results and calculations that the configuration of the catalyst of relatively high actibity was A.
1987, 5(1): 76-80
Abstract:
Elastomerie reactive microgels were evaluated as toughener for epoxy adhesives. It turned out that elastomeric microgels can improve lap shear strength and peel strength greatly. The glass transition temperature of the resin matrix was not affected by the presence of dispersed mierogel particles, and thus the microgel-toughened adhesives have a good bond strength at elevated temperatures.
Elastomerie reactive microgels were evaluated as toughener for epoxy adhesives. It turned out that elastomeric microgels can improve lap shear strength and peel strength greatly. The glass transition temperature of the resin matrix was not affected by the presence of dispersed mierogel particles, and thus the microgel-toughened adhesives have a good bond strength at elevated temperatures.
1987, 5(1): 81-86
Abstract:
Rheological investigation on a series ot unvulcamzed polybutadiene elastomers of different processability has been carried out by means of a capillary extrusion rheometer. It is found that the processability of unvulcanized polybutadiene can be correlated with the occurrence of unsteady flow and the wall stress, dependence of the dimensionless number e characterizing the entrance elongational elasticity which has been found to be sensitive to the branching structure and the molecular weight distribution of the samples.Interpretation based on the atructural data of unvulcanized polybutadiene were discussed.
Rheological investigation on a series ot unvulcamzed polybutadiene elastomers of different processability has been carried out by means of a capillary extrusion rheometer. It is found that the processability of unvulcanized polybutadiene can be correlated with the occurrence of unsteady flow and the wall stress, dependence of the dimensionless number e characterizing the entrance elongational elasticity which has been found to be sensitive to the branching structure and the molecular weight distribution of the samples.Interpretation based on the atructural data of unvulcanized polybutadiene were discussed.
