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1990 Volume 8 Issue 4
1990, 8(4): 289-294
Abstract:
In the process of bulk photopolymerization of styrene initiated by AIBN decomposition polyvinyl benzophenone (PVB) can supply an effective cage for triplet-triplet energy transfer between PVB macromolecules and small molecules of AIBN to influence the molecular weight of polystyrene in weak magnetic field (less than 0.035T), that was different from the case of polyvinyl naphthalene (PVN) which supplied cages for this system only in the stronger magnetic field (more than 0.2 T) studies. It was found that in the same conditions,PVN could exert more tremendous influences on the bulk photopolymerization system of styrene than PVB because in the stronger magnetic field the triplet PVN had much longer life time than PVB.
In the process of bulk photopolymerization of styrene initiated by AIBN decomposition polyvinyl benzophenone (PVB) can supply an effective cage for triplet-triplet energy transfer between PVB macromolecules and small molecules of AIBN to influence the molecular weight of polystyrene in weak magnetic field (less than 0.035T), that was different from the case of polyvinyl naphthalene (PVN) which supplied cages for this system only in the stronger magnetic field (more than 0.2 T) studies. It was found that in the same conditions,PVN could exert more tremendous influences on the bulk photopolymerization system of styrene than PVB because in the stronger magnetic field the triplet PVN had much longer life time than PVB.
1990, 8(4): 295-301
Abstract:
Many kinds of dispersed Pd (0) supported on cross-linked poly (N-vinyl pyrrolidone) were prepared and characterized by IR and X-ray diffraction. Their hydrogenation properties of methyl acrylate have been examined. Experimental results indicate that the hydrogenation rate will reach a maximum as the degree of crosslinking increases to a certain point. The catalytic activity of the catalysts is closely related to the preparation condition and the particle size of Pd of the catalysts. Some other factors which affect the catalytic properties have also been studied.
Many kinds of dispersed Pd (0) supported on cross-linked poly (N-vinyl pyrrolidone) were prepared and characterized by IR and X-ray diffraction. Their hydrogenation properties of methyl acrylate have been examined. Experimental results indicate that the hydrogenation rate will reach a maximum as the degree of crosslinking increases to a certain point. The catalytic activity of the catalysts is closely related to the preparation condition and the particle size of Pd of the catalysts. Some other factors which affect the catalytic properties have also been studied.
1990, 8(4): 302-311
Abstract:
The kinetics of polymerization of acrylonitrile (AN) initiated by quinquevalent vanadium (V5+)-thiourea (TU) redox system has been investigated in aqueous nitric acid in the temperature range from 30 to 50℃. The polymerization rate (Rp) can be expressed as follows:Rp=2.80×105e-14.200/RT[AN]2.2[V5+]0～1/3[TU]0～4/3[HNO3]0.2. In the copolymerization of acryionitrile with methyl acrylate (MA), the reactivity ratios were found to be 1.0 and 1.1, respectively. The experimental observations suggest that the initiating species is probably a complex consisting of a central ion of Lewis acid-VO2+ and the ligands of Lewis bases-acrylonitrile,thiourea,and nitrate anions,while the initiating system in lower concentration,the polymerization of acrylonitrile does not occur if the thiourea is acidified prior to its reaction with quinquevalent vanadium.This indicates that the primary radicals(or the monomeric radicals in the present article) are produced by associated thiourea rather than isothiourea.
The kinetics of polymerization of acrylonitrile (AN) initiated by quinquevalent vanadium (V5+)-thiourea (TU) redox system has been investigated in aqueous nitric acid in the temperature range from 30 to 50℃. The polymerization rate (Rp) can be expressed as follows:Rp=2.80×105e-14.200/RT[AN]2.2[V5+]0～1/3[TU]0～4/3[HNO3]0.2. In the copolymerization of acryionitrile with methyl acrylate (MA), the reactivity ratios were found to be 1.0 and 1.1, respectively. The experimental observations suggest that the initiating species is probably a complex consisting of a central ion of Lewis acid-VO2+ and the ligands of Lewis bases-acrylonitrile,thiourea,and nitrate anions,while the initiating system in lower concentration,the polymerization of acrylonitrile does not occur if the thiourea is acidified prior to its reaction with quinquevalent vanadium.This indicates that the primary radicals(or the monomeric radicals in the present article) are produced by associated thiourea rather than isothiourea.
1990, 8(4): 312-320
Abstract:
The dependence of the molecular weights on the concentration of reactants in the polymerization of acrylonitrile initiated by vanadium (V)-thiourea redox system has been investigated. It was found that the molecular weights of the polymer change nonlinearly with increasing concentrations of nitric acid and thiourea. Probably, the composition of the complexes exert a great influence on the chain initiation and termination. The reaction of "complextermination" gives rise to the decrease of the molecular weights markedly while the concentrations of thiourea and vanadium(V) in the range from one to three molar ratios.
The dependence of the molecular weights on the concentration of reactants in the polymerization of acrylonitrile initiated by vanadium (V)-thiourea redox system has been investigated. It was found that the molecular weights of the polymer change nonlinearly with increasing concentrations of nitric acid and thiourea. Probably, the composition of the complexes exert a great influence on the chain initiation and termination. The reaction of "complextermination" gives rise to the decrease of the molecular weights markedly while the concentrations of thiourea and vanadium(V) in the range from one to three molar ratios.
1990, 8(4): 321-329
Abstract:
The results of this study reveals not only the sensitivity of the compatibility of PS with SBR to the molecular weight (MW) of PS and temperature, but also some other interesting characteristics, i. e., unusual morphology change during the process of mixing with increase in temperature of specimen preparation observed under optical microscope and double-peak UCST curves for three blends with PS of low MW from DSC data. Acording to the amount of inward shift of the component Tg's and the broadening of the transition regions,it may be said that this polymer pair is compatible only when the MW of PS is low,and even then there still exists micro-heterogeneity.
The results of this study reveals not only the sensitivity of the compatibility of PS with SBR to the molecular weight (MW) of PS and temperature, but also some other interesting characteristics, i. e., unusual morphology change during the process of mixing with increase in temperature of specimen preparation observed under optical microscope and double-peak UCST curves for three blends with PS of low MW from DSC data. Acording to the amount of inward shift of the component Tg's and the broadening of the transition regions,it may be said that this polymer pair is compatible only when the MW of PS is low,and even then there still exists micro-heterogeneity.
1990, 8(4): 330-334
Abstract:
The compatibility and phase behavior of PS/SBR blends was studied with torsional braid analysis technique. The technique used in this study for preparation of braids was first developed by one of the authors, which gives more precise phase diagram as compared to other conventional methods. The results obtained are in good agreement with those obtained in our previous work.
The compatibility and phase behavior of PS/SBR blends was studied with torsional braid analysis technique. The technique used in this study for preparation of braids was first developed by one of the authors, which gives more precise phase diagram as compared to other conventional methods. The results obtained are in good agreement with those obtained in our previous work.
1990, 8(4): 335-341
Abstract:
Toughened epoxy resin with excellent properties was obtained by adding organic acid anhydride curing agent and hydroxy-terminated butadiene-acrylonitrile copolymer (HTBN), which is cheaper than CTBN. The anhydride reacts with both epoxy groups on epoxy resin and hydroxyl groups on HTBN. As a result the soft long chains of HTBN and the rigid chain of epoxy resin form one network, giving the resin toughness. Two-phase structure of the toughened resin was observed by SEM and TEM.
Toughened epoxy resin with excellent properties was obtained by adding organic acid anhydride curing agent and hydroxy-terminated butadiene-acrylonitrile copolymer (HTBN), which is cheaper than CTBN. The anhydride reacts with both epoxy groups on epoxy resin and hydroxyl groups on HTBN. As a result the soft long chains of HTBN and the rigid chain of epoxy resin form one network, giving the resin toughness. Two-phase structure of the toughened resin was observed by SEM and TEM.
1990, 8(4): 342-346
Abstract:
In an attempt to prepare a polymeric solid electrolyte with both high ionic conductivity at ambient temperature and adequate mechanical strength, an ionic conducting IPN composed of bisphenol A epoxy resin/polyethylene glycol containing LiClO4 was synthesized. The dependence of conductivity was investigated as a function of salt content, composition and temperature. It has been revealed that a maximum of conductivity appeared when EO/Li=25, where EO denotes the—(CH2CH2O)-unit in polyethylene glycol, and that the temperature dependence of conductivity followed VTF equation,suggesting that the motion of ionic carriers resulted from the segmental motion of the polymer.When glycerol epoxy resin was used instead of bisphenol A epoxy,the ambient temperature(25℃) conductivity could somewhat further be raised up to 3×10-5 S/cm.
In an attempt to prepare a polymeric solid electrolyte with both high ionic conductivity at ambient temperature and adequate mechanical strength, an ionic conducting IPN composed of bisphenol A epoxy resin/polyethylene glycol containing LiClO4 was synthesized. The dependence of conductivity was investigated as a function of salt content, composition and temperature. It has been revealed that a maximum of conductivity appeared when EO/Li=25, where EO denotes the—(CH2CH2O)-unit in polyethylene glycol, and that the temperature dependence of conductivity followed VTF equation,suggesting that the motion of ionic carriers resulted from the segmental motion of the polymer.When glycerol epoxy resin was used instead of bisphenol A epoxy,the ambient temperature(25℃) conductivity could somewhat further be raised up to 3×10-5 S/cm.
1990, 8(4): 347-352
Abstract:
The plasma treatment of polytetrafluoroethylene (PTFE) films was carried out in a capacitively coupled reactor with external electrodes. The free radicals generated in the process of treatment were detected by ESR techniques. The ESR spectra tended to indicate that the free radicals of the pLasma-treated PTFE film sample were turned into peroxy radicals on exposure to air. The extrema separation (W) of the ESR spectrum of the peroxy radical increased with the lowering temperature and underwent a sudden change within the temperature range of 170 to 190K.The ESR spectrum observed at 77K was quite different from that observed at room temperature.Finally,the effects of treatment time.input power and system pressure on radical concentration of the treated samples were studied.The attenuation of the peroxy radical at room temperature was also investigated.
The plasma treatment of polytetrafluoroethylene (PTFE) films was carried out in a capacitively coupled reactor with external electrodes. The free radicals generated in the process of treatment were detected by ESR techniques. The ESR spectra tended to indicate that the free radicals of the pLasma-treated PTFE film sample were turned into peroxy radicals on exposure to air. The extrema separation (W) of the ESR spectrum of the peroxy radical increased with the lowering temperature and underwent a sudden change within the temperature range of 170 to 190K.The ESR spectrum observed at 77K was quite different from that observed at room temperature.Finally,the effects of treatment time.input power and system pressure on radical concentration of the treated samples were studied.The attenuation of the peroxy radical at room temperature was also investigated.
1990, 8(4): 353-358
Abstract:
A series of PCL/MDI/BDO segmented polyurethanes have been synthesized by two-step method in solution.The hard segment content ranges from 10% to 48% by weight, and the molecular weight of PCL diols is 1500. Hard segment spherulites have been observed in compression molded specimens of all of the samples except the one of the lowest hard segment content. The difficulty in sphernlite formation was explained as only in a small temperature range,the microphase separation rate may be faster than the crystallization rate and all these processes are very slow due to the hydrogen bonding between hard and solf segments and the interactions between hard segments themselves.PCL soft segments of molecular weight 1500 is still crystallizable and may form different crystalline superstructures.
A series of PCL/MDI/BDO segmented polyurethanes have been synthesized by two-step method in solution.The hard segment content ranges from 10% to 48% by weight, and the molecular weight of PCL diols is 1500. Hard segment spherulites have been observed in compression molded specimens of all of the samples except the one of the lowest hard segment content. The difficulty in sphernlite formation was explained as only in a small temperature range,the microphase separation rate may be faster than the crystallization rate and all these processes are very slow due to the hydrogen bonding between hard and solf segments and the interactions between hard segments themselves.PCL soft segments of molecular weight 1500 is still crystallizable and may form different crystalline superstructures.
1990, 8(4): 359-362
Abstract:
In this work, characterization of radiation grafting degree of polystyrene-g-acrylic acid by XPS was studied. It is found that along with the main peak C1s there is a photoelectron peak at 289.0 eV that appears to be C1s of-(?)-OH group and shows the presence ofpolyacrylic acid grafted on the polystyrene The grafting degree obtained by XPS is in agreement with that from the gravimetric method.
In this work, characterization of radiation grafting degree of polystyrene-g-acrylic acid by XPS was studied. It is found that along with the main peak C1s there is a photoelectron peak at 289.0 eV that appears to be C1s of-(?)-OH group and shows the presence ofpolyacrylic acid grafted on the polystyrene The grafting degree obtained by XPS is in agreement with that from the gravimetric method.
1990, 8(4): 363-370
Abstract:
The initiation mechanism of methyl methacrylate (MMA) polymerization by organic peroxide and polymerizable aromatic tertiary amine such as N-methacryloyloxyethyl-N-methyl aniline (MEMA) binary system has been studied. The kinetics of polymerization of MMA and the ESR spectra of organic peroxide/MEMA system were determined. Based on the ESR study and the end-group analysis by UV spectra of the polymer formed, the initiation mechanism is proposed.
The initiation mechanism of methyl methacrylate (MMA) polymerization by organic peroxide and polymerizable aromatic tertiary amine such as N-methacryloyloxyethyl-N-methyl aniline (MEMA) binary system has been studied. The kinetics of polymerization of MMA and the ESR spectra of organic peroxide/MEMA system were determined. Based on the ESR study and the end-group analysis by UV spectra of the polymer formed, the initiation mechanism is proposed.
1990, 8(4): 371-376
Abstract:
The polymerization rates of three cyanopyridines catalyzed by cuprous chloride-zinc system are measured, and the structure of the formed polymer is also determined. Compared with aromatic nitrile, cyanopyridines polymerize faster and form polyconjugated polymer with skeleton—(C=N)—n instead of triazine structure. This chain-polymer possesses semiconductive property, and can be converted into conductive material by thermal treatment. In addition, the polymerization kinetics of 3-cyanopyridine catalyzed by 3-cyanopyridinium perchlorate is investigated.It is found that the polymerization rate is directly proportional to the concentrations of monomer and catalyst,and the activation energy of the polymerization is 103.1 KJ/mol.
The polymerization rates of three cyanopyridines catalyzed by cuprous chloride-zinc system are measured, and the structure of the formed polymer is also determined. Compared with aromatic nitrile, cyanopyridines polymerize faster and form polyconjugated polymer with skeleton—(C=N)—n instead of triazine structure. This chain-polymer possesses semiconductive property, and can be converted into conductive material by thermal treatment. In addition, the polymerization kinetics of 3-cyanopyridine catalyzed by 3-cyanopyridinium perchlorate is investigated.It is found that the polymerization rate is directly proportional to the concentrations of monomer and catalyst,and the activation energy of the polymerization is 103.1 KJ/mol.
