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1986 Volume 4 Issue 3
1986, 4(3): 207-213
Abstract:
The morphological structure and mechanism of nucleation and growth of Ln-PB and Ni-PBwith different molecular weight were investigated by transmission electron microscopy. The crys-tallization of low molecular weight fraction is primarily from predetermined nuclei, crystallizationfor the high molecular weight fraction is primarily from sporadic nuclei. Two types morphologyof spherulite with different lamellar entanglement have been observed. The entanglement of highermolecular weight fractions are found to be of significance in the morphology and rate of crystallization of polymer.
The morphological structure and mechanism of nucleation and growth of Ln-PB and Ni-PBwith different molecular weight were investigated by transmission electron microscopy. The crys-tallization of low molecular weight fraction is primarily from predetermined nuclei, crystallizationfor the high molecular weight fraction is primarily from sporadic nuclei. Two types morphologyof spherulite with different lamellar entanglement have been observed. The entanglement of highermolecular weight fractions are found to be of significance in the morphology and rate of crystallization of polymer.
1986, 4(3): 214-219
Abstract:
A kinetic study on the photopolymerization of methyl methacrylate (MMA) with benzophenone(BP)/triethylamine (TEA)/mercaptan systems as initiator has been carried out in the presence of oxygen.It was found that both aliphatic and aromatic thiols promote the photooxidation process, leadingto obvious decrease in induction period of photopolymerization. The rate-aereleration of aromaticthiols is more effective than that of aliphatic ones, such as p-toluene thiol used as additive increasesthe relative quantum yieldφO2/φN2 to 1.8.
A kinetic study on the photopolymerization of methyl methacrylate (MMA) with benzophenone(BP)/triethylamine (TEA)/mercaptan systems as initiator has been carried out in the presence of oxygen.It was found that both aliphatic and aromatic thiols promote the photooxidation process, leadingto obvious decrease in induction period of photopolymerization. The rate-aereleration of aromaticthiols is more effective than that of aliphatic ones, such as p-toluene thiol used as additive increasesthe relative quantum yieldφO2/φN2 to 1.8.
1986, 4(3): 220-228
Abstract:
In the presence of Friedel-Crafts catalyst, the chloromethylated copolymer of styrene-divinylben-zene may react with each other and cross-link by itself Thus a new type of polymeric adsorbent wasobtained, and its structure was identified by its physical properties and infrared spectra. The Friedel-Crafts reaction is manifestly affected by the nature of the solvent, the kind and amount of catalystused, reaction temperature and reaction time, etc. The porous structure and physical properties of the adsorbent prepared have been investigated systematically.The adsorbent has ligh specific surface area(1000-1300 m2/g),porosity,narrow pore distribution,high skeleton density and good mechanical properties.
In the presence of Friedel-Crafts catalyst, the chloromethylated copolymer of styrene-divinylben-zene may react with each other and cross-link by itself Thus a new type of polymeric adsorbent wasobtained, and its structure was identified by its physical properties and infrared spectra. The Friedel-Crafts reaction is manifestly affected by the nature of the solvent, the kind and amount of catalystused, reaction temperature and reaction time, etc. The porous structure and physical properties of the adsorbent prepared have been investigated systematically.The adsorbent has ligh specific surface area(1000-1300 m2/g),porosity,narrow pore distribution,high skeleton density and good mechanical properties.
1986, 4(3): 229-234
Abstract:
The following factors affecting the rubber toughened epoxy resin system were studied: 1. kindsof curing agent used, 2. the Mc value of the matrix, 3. the bonding foce between the dispersed phaseand the matrix. Our experimental result indicates that the average chain length between crosslinks(Mc) is a much more important affecting factor. Chemical bonding between the dispersed phaseand the matrix is also important. A toughening mechanism of rubber toughened epoxy has beenproposed. In the material with relatively low crosslinking density,extensive fracture process strip is formed which is induced by the combined stress field near the rubber particles.The chemical bonding between the dispersed phase and the matrix may increase the strength of the local stress field about the rubber particles which is in favor of broading the fracture process area.
The following factors affecting the rubber toughened epoxy resin system were studied: 1. kindsof curing agent used, 2. the Mc value of the matrix, 3. the bonding foce between the dispersed phaseand the matrix. Our experimental result indicates that the average chain length between crosslinks(Mc) is a much more important affecting factor. Chemical bonding between the dispersed phaseand the matrix is also important. A toughening mechanism of rubber toughened epoxy has beenproposed. In the material with relatively low crosslinking density,extensive fracture process strip is formed which is induced by the combined stress field near the rubber particles.The chemical bonding between the dispersed phase and the matrix may increase the strength of the local stress field about the rubber particles which is in favor of broading the fracture process area.
1986, 4(3): 235-240
Abstract:
Proton-decoupled, 13C FT-NMR (operating at 50.3 MHz) is used to determine spin-latticerelaxation time (T1), nuclear Overhauser enhancement (NOE), linewidth and chemical shift of 1,2-polybutadiene as a function of temperature in CDCl3 solution and the temperature dependence ofmolecular motion of 1,2-polybutadiene has been investigated with these NMR relaxation parameters.It is found that jumps of NOE and linewidth vs. temperature appear between-1℃ and -30℃. Theminimum of nT1 vs. temperature for all carbons occur at about -45℃.
Proton-decoupled, 13C FT-NMR (operating at 50.3 MHz) is used to determine spin-latticerelaxation time (T1), nuclear Overhauser enhancement (NOE), linewidth and chemical shift of 1,2-polybutadiene as a function of temperature in CDCl3 solution and the temperature dependence ofmolecular motion of 1,2-polybutadiene has been investigated with these NMR relaxation parameters.It is found that jumps of NOE and linewidth vs. temperature appear between-1℃ and -30℃. Theminimum of nT1 vs. temperature for all carbons occur at about -45℃.
1986, 4(3): 241-247
Abstract:
The effects of molecular weight and temperature on crystallization processes at low tempera-ture for cis-1,4 polybutadiene prepared with rare-earth catalyst (Ln-PB) have been studied by WAXDmethod. In the range of molecular weight from(Mn)=2.13×105 to 46.8× 105,there are a maximum of crystallization rate at (Mn)≈29× 105 and a minimum at (Mn)≈8×105.The temperature related to maximum crystallization rate,Tc,max is observed to be between -60℃ and -70℃.The degree of equilibrium crystallinity of Ln-PB is independent of molecular weight at (Mn) greater than 104,also the linearity is shown between the correspondent temperature,degree of equilibrium crystallinity and molecular weight.Values of unit cell parameters of Ln-PB increase with temperature.The main crystallization of Ln-PB belongs to heterogeneous nucleation.The crystallization processes are mixed growth one and two dimensions.
The effects of molecular weight and temperature on crystallization processes at low tempera-ture for cis-1,4 polybutadiene prepared with rare-earth catalyst (Ln-PB) have been studied by WAXDmethod. In the range of molecular weight from(Mn)=2.13×105 to 46.8× 105,there are a maximum of crystallization rate at (Mn)≈29× 105 and a minimum at (Mn)≈8×105.The temperature related to maximum crystallization rate,Tc,max is observed to be between -60℃ and -70℃.The degree of equilibrium crystallinity of Ln-PB is independent of molecular weight at (Mn) greater than 104,also the linearity is shown between the correspondent temperature,degree of equilibrium crystallinity and molecular weight.Values of unit cell parameters of Ln-PB increase with temperature.The main crystallization of Ln-PB belongs to heterogeneous nucleation.The crystallization processes are mixed growth one and two dimensions.
1986, 4(3): 248-255
Abstract:
A series of copolyesters based on bis(4-hydroxybutyl) terephthalate, terephthaloyl chloride andvarious aromatic diols (i.e. hydroquinone, chlorohydroquinone, bromohydroquinone or dihydroxybi-phenyl) was prepared. 1H-NMR studies revealed that the monomer units had microstructures closeto random distribution in the chains. The copolymers showed composition-dependent liquid crystal-line properties as verified by visual observation of stir opalescence, polarizing microscope, DSC andX-ray diffration. The copolyesters with aromatic diol contents over a certain extent(for chloro-hydroquinone m≥0.33) were thermotropic with wide liquid crystalline temperature ranges.The introduction of chlorohydroquinone into the copolyesters could gradually destroy the crystallinity of the polymers but retain the liquid crystalline characteristics.
A series of copolyesters based on bis(4-hydroxybutyl) terephthalate, terephthaloyl chloride andvarious aromatic diols (i.e. hydroquinone, chlorohydroquinone, bromohydroquinone or dihydroxybi-phenyl) was prepared. 1H-NMR studies revealed that the monomer units had microstructures closeto random distribution in the chains. The copolymers showed composition-dependent liquid crystal-line properties as verified by visual observation of stir opalescence, polarizing microscope, DSC andX-ray diffration. The copolyesters with aromatic diol contents over a certain extent(for chloro-hydroquinone m≥0.33) were thermotropic with wide liquid crystalline temperature ranges.The introduction of chlorohydroquinone into the copolyesters could gradually destroy the crystallinity of the polymers but retain the liquid crystalline characteristics.
1986, 4(3): 256-261
Abstract:
Plasma-polymerization of octafluorocyclobutane was carried out in a capacitively coupled tubu-lar reactor with external electrodes. The number-average molecular weight, melting temperature,decomposition temperature and solubility in te trafluorodibromoethane of the products was mea-sured and the polymer structure was characterized by ESR. IR and19F-NMR methods. The experi-mental results show the absence of the highly crosslinked structure but a fluorine-deficient structurecaused by free-radicals, carbonyl groups,double bonds and multicage-like segments in the polymer.
Plasma-polymerization of octafluorocyclobutane was carried out in a capacitively coupled tubu-lar reactor with external electrodes. The number-average molecular weight, melting temperature,decomposition temperature and solubility in te trafluorodibromoethane of the products was mea-sured and the polymer structure was characterized by ESR. IR and19F-NMR methods. The experi-mental results show the absence of the highly crosslinked structure but a fluorine-deficient structurecaused by free-radicals, carbonyl groups,double bonds and multicage-like segments in the polymer.
1986, 4(3): 262-273
Abstract:
The mechanical behaviors of polyether (ET) and polyester (ES) soft segment urethane-ureaelastomeric fibers constrained at different levels of elongation have been investigated by means ofdynamic mechanical tests and force-temperature measurements. The dynamjc mechanical re-sponse of the ET urethane-urea showed some difference from that of the ES as a function of exten-sion ratio. For force-temperature measuring the existence of a low temperature transition corre-sponding to the glass transition (Tg's) of the ester or ether soft segments,stree-softening temperature(Ts) and initial melting temperature(Tmh) of hard segment crystallites was observed.The result of cyclic testing of a constrained sample as a function of temperature indicated that the irreversible decrease in stress implied a permanent change in sample microstructure.
The mechanical behaviors of polyether (ET) and polyester (ES) soft segment urethane-ureaelastomeric fibers constrained at different levels of elongation have been investigated by means ofdynamic mechanical tests and force-temperature measurements. The dynamjc mechanical re-sponse of the ET urethane-urea showed some difference from that of the ES as a function of exten-sion ratio. For force-temperature measuring the existence of a low temperature transition corre-sponding to the glass transition (Tg's) of the ester or ether soft segments,stree-softening temperature(Ts) and initial melting temperature(Tmh) of hard segment crystallites was observed.The result of cyclic testing of a constrained sample as a function of temperature indicated that the irreversible decrease in stress implied a permanent change in sample microstructure.
1986, 4(3): 274-283
Abstract:
Two melting transitions were observed in linear segmented polyurethane-urea elastomers underextension using thermal, mechanical and X-ray diffraction techniques, and the results are compared.These data indicate both strain-induced and temperature-induced crystallization in the stretchedclastomers, which may result from two different types of crystallites with different melting tempera-tures. These have been assigned as type 1 appearing around 60℃, and type 2 around 30℃. The type 1 crystallization can be induced by stretching at room temperature to large strain,and is mechanically reversible,but the type 2 crystallization is mainly induced by cooling below its crystallization temperature.These two crystalline structures are interchangeable under suitable conditions.At elongations greater than 300%,the low temperature peak observed on fusion thermograms disappears or combines with the high temperature peak.When the temperature of the samplc is over the melting point of the type 1 crystal,irreversible melting occurs and only the type 2 crystal develops on cooling.The results of stress-strain and stress hysteresis experiments at different temperatures indicate the relative importance of strain-induced and temperature-induced crystallization on the mechanical properties of these materials.
Two melting transitions were observed in linear segmented polyurethane-urea elastomers underextension using thermal, mechanical and X-ray diffraction techniques, and the results are compared.These data indicate both strain-induced and temperature-induced crystallization in the stretchedclastomers, which may result from two different types of crystallites with different melting tempera-tures. These have been assigned as type 1 appearing around 60℃, and type 2 around 30℃. The type 1 crystallization can be induced by stretching at room temperature to large strain,and is mechanically reversible,but the type 2 crystallization is mainly induced by cooling below its crystallization temperature.These two crystalline structures are interchangeable under suitable conditions.At elongations greater than 300%,the low temperature peak observed on fusion thermograms disappears or combines with the high temperature peak.When the temperature of the samplc is over the melting point of the type 1 crystal,irreversible melting occurs and only the type 2 crystal develops on cooling.The results of stress-strain and stress hysteresis experiments at different temperatures indicate the relative importance of strain-induced and temperature-induced crystallization on the mechanical properties of these materials.
1986, 4(3): 284-291
Abstract:
A series of 1-naphthylmethyl methacrylate (NMMA)-methyl methacrylate (MMA) copolymerswere synthesized on free radical mechanism. The reactivity ratios of NMMA (r1) and MMA (r2) werereported to be 0.83 and 0.89, respectively. The characterization of the copolymers by using IR, NMR,GPC, UV and fiuorescence spectrometry was described in this paper.
A series of 1-naphthylmethyl methacrylate (NMMA)-methyl methacrylate (MMA) copolymerswere synthesized on free radical mechanism. The reactivity ratios of NMMA (r1) and MMA (r2) werereported to be 0.83 and 0.89, respectively. The characterization of the copolymers by using IR, NMR,GPC, UV and fiuorescence spectrometry was described in this paper.
1986, 4(3): 292-295
Abstract:
The effect of chain flexibility of fluoropolymers on their radiation crosslinking behavior is studiedand the relationship between sol fraction and the radiation dose to the fluoropolymers given in ourprevious report is confirmed.
The effect of chain flexibility of fluoropolymers on their radiation crosslinking behavior is studiedand the relationship between sol fraction and the radiation dose to the fluoropolymers given in ourprevious report is confirmed.
