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1996 Volume 14 Issue 2
1996, 14(2): 97-104
Abstract:
Various aspects of the rheological behaviour of liquid crystalline copolyesters, i.e.,samples of copoly (p-hydroxybenzoate / bisphenol A terephthalate), were explored by usingInstron capillary rheometer. The experimental results indicated that the apparent viscositywas affected significantly by shear rate, melt temperature and p-hydroxybenzoate unit con-tent. The flow activation energies △Eη are in the range of 205.1 to 74.5 kJ/mol, dependingon the shear rate of 10-1000 s-1, at temperature 568-603K. These copolyesters exhibit a yield phenomenon in the shear flow,and the values of yield stress decrease with increasing temperature.It is quite unusual that the extrudate of the copolyester shows the smaller swelling ratio even than unity at the lower temperature and lower shear rates.
Various aspects of the rheological behaviour of liquid crystalline copolyesters, i.e.,samples of copoly (p-hydroxybenzoate / bisphenol A terephthalate), were explored by usingInstron capillary rheometer. The experimental results indicated that the apparent viscositywas affected significantly by shear rate, melt temperature and p-hydroxybenzoate unit con-tent. The flow activation energies △Eη are in the range of 205.1 to 74.5 kJ/mol, dependingon the shear rate of 10-1000 s-1, at temperature 568-603K. These copolyesters exhibit a yield phenomenon in the shear flow,and the values of yield stress decrease with increasing temperature.It is quite unusual that the extrudate of the copolyester shows the smaller swelling ratio even than unity at the lower temperature and lower shear rates.
1996, 14(2): 105-110
Abstract:
The permeability coefficients of a series of copolymers of vinylidene chloride (VDC)with methyl acrylate (MA), butyl acrylate (BA) or vinyl chloride (VC) (as comonomer)to oxygen and carbon dioxide have been measured at 1.0 MPa and 30℃, while those towater vapor have been measured at 30℃ and 100% relative humidity. All the copolymersare semicrystalline. VDC/MA copolymers have lower melting temperature compared with VDC/BA copolymers, while that melting temperature of VDC/VC copolymer is higherthan that of VDC/acrylate copolymers with thesame VDC content.The barrier property of the copolymers is predominantly controlled by crystallite,free volume fraction,and cohesive energy.The permeability coefficients of VDC/MA copolymers to oxygen,carbon dioxide,and water vapor were successfully correlated with the ratio of free volume to cohesive energy.
The permeability coefficients of a series of copolymers of vinylidene chloride (VDC)with methyl acrylate (MA), butyl acrylate (BA) or vinyl chloride (VC) (as comonomer)to oxygen and carbon dioxide have been measured at 1.0 MPa and 30℃, while those towater vapor have been measured at 30℃ and 100% relative humidity. All the copolymersare semicrystalline. VDC/MA copolymers have lower melting temperature compared with VDC/BA copolymers, while that melting temperature of VDC/VC copolymer is higherthan that of VDC/acrylate copolymers with thesame VDC content.The barrier property of the copolymers is predominantly controlled by crystallite,free volume fraction,and cohesive energy.The permeability coefficients of VDC/MA copolymers to oxygen,carbon dioxide,and water vapor were successfully correlated with the ratio of free volume to cohesive energy.
1996, 14(2): 111-119
Abstract:
Six aromatic polyesters were prepared for gas separation membranes, and their per-meation properties for hydrogen, oxygen, nitrogen, carbon dioxide, and methane weremeasured at 30℃ and 1 atmosphere by low pressure manometric method. The cor-relation between the gas transport behavior and molecular structure of aromatic polyestermembrane is discussed. These data are interpreted qualitatively in terms of the calculatedpacking density, gas-polymer interaction, concentration of aryl bromine on backbone, and effect of silane group on main chain of polymer.
Six aromatic polyesters were prepared for gas separation membranes, and their per-meation properties for hydrogen, oxygen, nitrogen, carbon dioxide, and methane weremeasured at 30℃ and 1 atmosphere by low pressure manometric method. The cor-relation between the gas transport behavior and molecular structure of aromatic polyestermembrane is discussed. These data are interpreted qualitatively in terms of the calculatedpacking density, gas-polymer interaction, concentration of aryl bromine on backbone, and effect of silane group on main chain of polymer.
1996, 14(2): 120-126
Abstract:
A new series of acrylates with the same mesogens containing thioester as bridge-bondwere synthesized, and the acrylates were characterized by H1 NMR, IR and MS. Thepolymers were obtained by radical polymerization using AIBN as initiator. The monomersand polymers exhibit thermotropic-enantiotropic liquid crystalline behavior.
A new series of acrylates with the same mesogens containing thioester as bridge-bondwere synthesized, and the acrylates were characterized by H1 NMR, IR and MS. Thepolymers were obtained by radical polymerization using AIBN as initiator. The monomersand polymers exhibit thermotropic-enantiotropic liquid crystalline behavior.
1996, 14(2): 127-133
Abstract:
A new organic aerogel made from (N- hydroxymethyl)-acrylamide (NA) and resorcinolis reported. The acidic solution of NA and resorcinol was irradiated by γ-rays with 1200-1800 Gy dose, then was heated to 60℃ for at least 16hr to form transparent sol-gel.The translucent aerogel can be obtained from the sol-gel with CO2 as supercritical fluid.Synthetic conditions (e.g. acidity of the solution, ratio of NA to resorcinol) are discussed.
A new organic aerogel made from (N- hydroxymethyl)-acrylamide (NA) and resorcinolis reported. The acidic solution of NA and resorcinol was irradiated by γ-rays with 1200-1800 Gy dose, then was heated to 60℃ for at least 16hr to form transparent sol-gel.The translucent aerogel can be obtained from the sol-gel with CO2 as supercritical fluid.Synthetic conditions (e.g. acidity of the solution, ratio of NA to resorcinol) are discussed.
1996, 14(2): 134-141
Abstract:
Critical concentrations of lyotropic liquid crystalline ethylcellulose in more than tensolvents were determined using both Abbe refractometer and polarized microscopy. Criti-cal concentration Ccrit of forming liquid crystal phase decreased with increasing solubilityparameter δ of solvent until approaching the δ of polymer. Although the alcohols usedas solvents had the same variation rule, the critical concentration values of their solutionswere much higher, due to their excessive large hydrogen bond component of δ.The experiments of using mixes solvents which showed good linear relation between Ccrit and δalso proved this rule.A technique of Transmission Optical Anaysis was first used to estimate the concentration dependence of critical phase transition temperature Tcritof EC,and a T-C phase diagram could be drawn.
Critical concentrations of lyotropic liquid crystalline ethylcellulose in more than tensolvents were determined using both Abbe refractometer and polarized microscopy. Criti-cal concentration Ccrit of forming liquid crystal phase decreased with increasing solubilityparameter δ of solvent until approaching the δ of polymer. Although the alcohols usedas solvents had the same variation rule, the critical concentration values of their solutionswere much higher, due to their excessive large hydrogen bond component of δ.The experiments of using mixes solvents which showed good linear relation between Ccrit and δalso proved this rule.A technique of Transmission Optical Anaysis was first used to estimate the concentration dependence of critical phase transition temperature Tcritof EC,and a T-C phase diagram could be drawn.
1996, 14(2): 142-149
Abstract:
2,2'-Bis (4H-3, 1-benzoxazin-4-one) (BBON) has been proved to be an effective chainextender for poly (ethylene terephthalate) (PET). In order to study the reaction mechanismand kinetics of chain-extending reaction, β-bishydroxyethylene terephthalate (BHET) wasselected as model compound. The NMR data, IR spectra and number average molecularweight (Mn) of the products obtained from the reaction of BBON and BHET verify thatBBON is a hydroxyl-reactive extender. The mechanism was discussed. Kinetics data indicate that extending reaction is a second order reaction,and BBON has high reactivity.The activation energy (Ea) was measured.
2,2'-Bis (4H-3, 1-benzoxazin-4-one) (BBON) has been proved to be an effective chainextender for poly (ethylene terephthalate) (PET). In order to study the reaction mechanismand kinetics of chain-extending reaction, β-bishydroxyethylene terephthalate (BHET) wasselected as model compound. The NMR data, IR spectra and number average molecularweight (Mn) of the products obtained from the reaction of BBON and BHET verify thatBBON is a hydroxyl-reactive extender. The mechanism was discussed. Kinetics data indicate that extending reaction is a second order reaction,and BBON has high reactivity.The activation energy (Ea) was measured.
1996, 14(2): 150-162
Abstract:
A full-relaxation optimization of molecule and the popular MM2 force field are em-ployed to obtain the geometry parameters and the conformational energy surface of a mesoor a racemic dyad of poly(methyl acrylate) (PMA) with a specified carbonyl-bond orien-tation in side-groups. It is found that the conformational energy maps calculated hereconsiderably differ from those calculated with the rigid molecular model as reported in theearlier studies. The g- state cannot be omitted in the obtained contour maps.Two important conformers tg- and g -t with energy minima were newly detected for a racemic dyad.The analysis on the conformations with energy minima confirmed that the ester groups are not always perpendicular to the plane defined by the two adjacent skeletal bonds and may change their relative orientations to meet the requirement of lower energies during the conformational state transition.Instead of the early way of adjusting the interaction energy parameters to fit the experimental data,we attempt to predict unperturbed chain dimensions via the reliable force field and the configurational statistical mechanics.The proposed scheme with three rotational states identified from the contour maps allowed us to satisfactorily reproduce the experimental dimensions of random PMA chains.
A full-relaxation optimization of molecule and the popular MM2 force field are em-ployed to obtain the geometry parameters and the conformational energy surface of a mesoor a racemic dyad of poly(methyl acrylate) (PMA) with a specified carbonyl-bond orien-tation in side-groups. It is found that the conformational energy maps calculated hereconsiderably differ from those calculated with the rigid molecular model as reported in theearlier studies. The g- state cannot be omitted in the obtained contour maps.Two important conformers tg- and g -t with energy minima were newly detected for a racemic dyad.The analysis on the conformations with energy minima confirmed that the ester groups are not always perpendicular to the plane defined by the two adjacent skeletal bonds and may change their relative orientations to meet the requirement of lower energies during the conformational state transition.Instead of the early way of adjusting the interaction energy parameters to fit the experimental data,we attempt to predict unperturbed chain dimensions via the reliable force field and the configurational statistical mechanics.The proposed scheme with three rotational states identified from the contour maps allowed us to satisfactorily reproduce the experimental dimensions of random PMA chains.
1996, 14(2): 163-171
Abstract:
In this paper, the capabilities of grafting acrylonitrile (AN) onto starch initiatedby Fe(III)-TU, V(V)-TU, Cr(VI)-TU, Mn(VII)-TU redox systems were compared in thepresence of sulfuric acid of different concentrations. It was shown that the grafting capabili-ty of Mn(VII)-TU is the highest in these initiating systems. Using Mn (VII-TU as initia-tor, the effects of various acids (HClO4, H2SO4, HNO3, HCl) on the graft copolymerizationof acrylonitrile onto starch were discussed, and the capabilities of graft copolymerization of methyl methacrylate (MMA),acrylamide (AM),acrylic acid (AA) onto starch were investigated.The experimental results show that the order of the influences of different acids is HCIO4>H2SO4>HNO3>HC1,and the order of grafting capabilities of different monomers grafted noto starch is MMA>AN>AM>AA.The structure and morphology of graft copolymers were studied with infrared spectroscopy and scanning electron microscopy.The size,shape and roughness of surface of the grafted starch granules are changed after grafting.
In this paper, the capabilities of grafting acrylonitrile (AN) onto starch initiatedby Fe(III)-TU, V(V)-TU, Cr(VI)-TU, Mn(VII)-TU redox systems were compared in thepresence of sulfuric acid of different concentrations. It was shown that the grafting capabili-ty of Mn(VII)-TU is the highest in these initiating systems. Using Mn (VII-TU as initia-tor, the effects of various acids (HClO4, H2SO4, HNO3, HCl) on the graft copolymerizationof acrylonitrile onto starch were discussed, and the capabilities of graft copolymerization of methyl methacrylate (MMA),acrylamide (AM),acrylic acid (AA) onto starch were investigated.The experimental results show that the order of the influences of different acids is HCIO4>H2SO4>HNO3>HC1,and the order of grafting capabilities of different monomers grafted noto starch is MMA>AN>AM>AA.The structure and morphology of graft copolymers were studied with infrared spectroscopy and scanning electron microscopy.The size,shape and roughness of surface of the grafted starch granules are changed after grafting.
1996, 14(2): 172-182
Abstract:
The interfacial adhesion between poly (ethylene terephthalate) (PET) and glass beadwas investigated by scanning electron microscope and parallel-plate rheometer. Effect ofinterfacial adhesion on the crystallization and mechenical properties of PET/glass beadcomposites was also studied by differential scanning calorimeter and mechanical testers.The results obtained indicate that the glass bead has a heterogeneous nucleation effecton the PET crystallization. Although better interfacial adhesion is advantageous to the increase of the tensile strength of the composite,yet it is unfavorable to the crystallization of PET.It should be pointed out that the crystallization rate of filled PET is always higher than that of pure PET,regardless of the state of interfacial adhesion.
The interfacial adhesion between poly (ethylene terephthalate) (PET) and glass beadwas investigated by scanning electron microscope and parallel-plate rheometer. Effect ofinterfacial adhesion on the crystallization and mechenical properties of PET/glass beadcomposites was also studied by differential scanning calorimeter and mechanical testers.The results obtained indicate that the glass bead has a heterogeneous nucleation effecton the PET crystallization. Although better interfacial adhesion is advantageous to the increase of the tensile strength of the composite,yet it is unfavorable to the crystallization of PET.It should be pointed out that the crystallization rate of filled PET is always higher than that of pure PET,regardless of the state of interfacial adhesion.
1996, 14(2): 183-187
Abstract:
This investigation deals with the free radical polymerization both of (2-methacryloyloxy-ethyl) trimethyl ammonium chloride (QACEMA) and of diallyldimethyl ammoniumcbloride (DADMAC) in inverse emulsion. The influences of some factors, such as theconcentration of monomers, initiator and emulsifier are discussed. The polymerization rateequations of above two monomers can be written as follows:Rp= k[M]1.21 [I]0.82 [E]0.57 (for QACEMA)Rp= k'[M]1.34 [I]0.90[E]0.62(for DADMAC)
This investigation deals with the free radical polymerization both of (2-methacryloyloxy-ethyl) trimethyl ammonium chloride (QACEMA) and of diallyldimethyl ammoniumcbloride (DADMAC) in inverse emulsion. The influences of some factors, such as theconcentration of monomers, initiator and emulsifier are discussed. The polymerization rateequations of above two monomers can be written as follows:Rp= k[M]1.21 [I]0.82 [E]0.57 (for QACEMA)Rp= k'[M]1.34 [I]0.90[E]0.62(for DADMAC)
1996, 14(2): 188-192
Abstract:
A wholly-aromatic thermotropic liquid crystalline polymer (WATLCP) composed ofp-hydroxybenzoic acid (HBA), 4,4'-dihydroxy bisphenyl (BP), terephthalic acid (TPA),m-phthalic acid (MPA) was synthesized. It was symbolized by BP-LCP. Using a simi-lar method, a new copolymer BP-PSF was prepared. BP-PSF has a semi-flexible chainpolysulfone and a rigid-rod chain like BP-LCP. By FT-IR, polarizing microscope and DSCtechnique, the structures and properties of BP-LCP and BP-PSF were studied.
A wholly-aromatic thermotropic liquid crystalline polymer (WATLCP) composed ofp-hydroxybenzoic acid (HBA), 4,4'-dihydroxy bisphenyl (BP), terephthalic acid (TPA),m-phthalic acid (MPA) was synthesized. It was symbolized by BP-LCP. Using a simi-lar method, a new copolymer BP-PSF was prepared. BP-PSF has a semi-flexible chainpolysulfone and a rigid-rod chain like BP-LCP. By FT-IR, polarizing microscope and DSCtechnique, the structures and properties of BP-LCP and BP-PSF were studied.
