摘要:

AbstractGraft‐copolymerization of acrylamide (AAm) on poly(ethylene terephthalate) (PET) films using benzoyl peroxide (Bz2O2) initiator has been studied. Four organic solvents, namely, pyridine (Py), 1,2‐dichloroethane (DCE), DEC/H2O (20/80, v/v), and dimethyl sulfoxide (DMSO), were used as swelling agents. DMSO was found to be the most suitable swelling agent. Solvent inclusion in the films increased with increased length of solvent treatment time and temperature. Elevated temperatures had a greater effect on the inclusion of swelling agents than did the length of swelling. Variation of graft yield with the type of solvent, initiator concentration, monomer concentration, temperature, and polymerization time were also investigated. The graft yield increased in the order of toluene, benzene, DMSO. The optimum temperature for grafting was found to be 70°C. The graft yield was observed to increase with monomer concentration and polymerization time, then reached a plateau. The graft yield increased up to a certain Bz2O2concentration, then decreased. © 1993 John Wiley&Sons

ISSN:0021-8995    

DOI:10.1002/app.1993.070470101

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe sorption of CO2and the noble gases Ne and Ar in semicrystalline glassy poly(butylene terephthalate) (PBTP) films was measured by the gravimetric method with a recording microbalance at 298 K. The sorption of CO2was found to be significantly higher than that of Ne and Ar. This is attributed to a specific interaction between CO2and PBTP. The sorption isotherm for CO2was analyzed by the dual‐mode sorption model, while the sorption behaviors for Ne and Ar did not follow this model. Their sorption isotherms can be described by the sorption model developed here for the noble gases in PBTP. A critical adsorption pressurep*that is dependent mainly on the relative size of the frozen microvoids and the noble gas atoms is defined in this model. The Langmuir adsorption for describing the sorption in this gas/polymer system in addition to Henry's solubility happens just above thisp*, whereas only Henry's solubility takes place belowp*. © 1993 John Wiley&Sons, I

ISSN:0021-8995    

DOI:10.1002/app.1993.070470102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractSorption measurements of CO2, Ne, and Ar in poly(butylene terephthalate) (PBTP) films were studied by the gravimetric method with a recording microbalance at 298 K in the pressure range of 1–22 bar. The semicrystalline samples were annealed and oriented at 373 K. The sorption isotherms for CO2in PBTP films in the glassy state can be well described by the dual‐sorption theory. The nonlinear sorption behavior of Ne and Ar can be satisfactorily analyzed using the sorption model developed for noble gases in PBTP. For the undrawn annealed films, it has been found that the increment of crystallinity leads to the reduction of the equilibrium gas concentration. For the oriented films, the gas concentration rises with increasing draw ratio. It appears that the sorption behavior for all tested gases in the oriented PBTP films does not depend on the changes of crystallinity and crystalline morphology under extension. The difference of the critical pressurep*indicates the change in the size of the frozen microvoids existing in the noncrystalline phase, which was altered by annealing and drawing. © 1993 John Wiley&Sons,

ISSN:0021-8995    

DOI:10.1002/app.1993.070470103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractIn this work, the radiation‐induced structural changes in the copolymer of tetrafluoro‐ethylene and ethylene (F‐40) were studied by X‐ray photoelectron spectroscopy (XPS). During irradiation, some CF2groups in the polymer were found to have been converted into carbon structures that bonded indirectly with fluorine atoms. © 1993 John Wiley&S

ISSN:0021-8995    

DOI:10.1002/app.1993.070470104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractLow‐density polyethylene (LDPE) films cografted with vinylene carbonate (VCA) andN‐vinyl‐N‐methylacetamide (VIMA) were studied as a matrix for the immobilization of the enzyme alkaline phosphatase (ALP) either by direct fixation or by inserting spacers. When water‐soluble alkyldiamines such as diaminoethylene, diaminobutane, diethylenetriamine, and diaminohexane were used as spacers between the matrix and the enzyme, the surface concentration (SC) of the active ALP coupled on the matrix was increased, whereas the effect of the spacer on the SC was dependent on the length of the spacer. Bovine serum albumin (BSA) was preimmobilized onto the LDPE films to provide a better simulation of the biological environment for the enzyme, and the SC of ALP on the matrix was significantly increased by coupling ALP onto the BSA preimmobilized surfaces. Compared to native ALP, some physicochemical properties of ALP could be improved by the covalent immobilization. © 1993 John Wiley

ISSN:0021-8995    

DOI:10.1002/app.1993.070470105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractIn this article we report results of the evaluation of the reactivity of polyphenolic extracts of coconut husk with formaldehyde in both acidic and alkaline media. The objective of this evaluation was to determine if the extracts could be used in the preparation of phenol–formaldehyde‐type resins. Extracts were obtained using aqueous solutions of NaOH (with and without anthraquinone) and NH4OH. Because of their low Stiasny's Number values, these extracts are not suitable for phenol–formaldehyde resin preparation in acidic conditions unless they are mixed with phenol or phenolic derivatives. Nevertheless, extracts obtained with NaOH, especially at 100 and 120°C, showed sufficient reactivity with form‐aldehyde in basic conditions and may therefore be considered suitable for resin preparation in an alkaline medium. The resins were characterized using infrared spectroscopy (IR), differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA). A transition temperature prior to decomposition was not detected; their thermal stability was similar to phenol–formaldehyde‐type resins. © 1993 John Wi

ISSN:0021-8995    

DOI:10.1002/app.1993.070470106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractPolyacrylonitrile fiber was treated with hydroxylamine to form a chelating fiber containing the amidoxime group with high adsorption capacity to the Au3+ion (up to 626 mg/g, when the nitrile group conversion reaches 53.7%), reasonable mechanical properties, and good thermal stability; the relationship among reaction conditions, fiber structures, and properties were investigated. The amidoxime group content rapidly increases to a steady value with increasing reaction time or HONH2• HCl concentration, the fiber strength drops linearly with increasing reaction time, when the reaction takes place at the temperature where the morphology and order structure begins to be destroyed, and the amidoxime group content increases significantly, while fiber strength decreases remarkably. It is suggested that, to prepare a chelating fiber with high adsorption capacity and reasonable mechanical property, the reaction could be carried out at temperatures from 70 to 75°C, time of about 30 min, and concentration around 75 g/L. © 1993 John Wiley&Sons,

ISSN:0021-8995    

DOI:10.1002/app.1993.070470107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractGraft starch‐polyacrylonitrile copolymers have been obtained from cassava starch (yucca starch or tapioca), which was pre‐heated at 65 and 95°C for different lengths of time. The copolymerization was carried out by using ceric ion as initiator at different concentrations (2.0 to 8.0 mmol/L) and also varying both the length of time of copolymerization and the ratio of monomer to starch. The composition, or grafting parameters, of all the obtained copolymers was determined by weight difference after they were extracted with dimethylformamide and hydrolyzed with an acidic solution. Samples of these copolymers were also hydrolyzed with an aqueous solution of potasium bydroxide to produce the corresponding hydrogels, and its absorbency in water was determined. © 1993 John Wiley&Sons

ISSN:0021-8995    

DOI:10.1002/app.1993.070470108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe characteristics of glycidyl methacrylate (GMA)–modifiers, including the polymerization properties, curing properties, and thermal stability, were studied. The degree of crosslinkage for (GMA–modifier)polyols increases with increasing hexamethoxymethylmelamine (HMMM) content and reaches maximum when HMMM content is about 40 wt %. The gels obtained from thermal free‐radical polymerization for GMA‐modifier monomer decrease with increasing acid value. UV curing experiments indicate that the energy of ultraviolet might be insufficient to promote the curing reaction through transetherification with short‐term irradiation. Kinetic parameters for the thermal decomposition of the polymer were measured with TG thermograms. © 1993 John Wiley

ISSN:0021-8995    

DOI:10.1002/app.1993.070470109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe cyanoethylation of jute fiber was studied at different reaction conditions. Moisture regain decreased significantly on cyanoethylation. Introduction of 5–6% nitrogen content on the fiber minimized the moisture regain capacity to 2.8%. A further increase in the nitrogen content increased the moisture regain. The effect of cyanoethylation on infrared absorption was studied. The absorbance curves of OH and CH stretching frequencies are parabolic in nature, whereas β‐glycosidic and CH bending absorption curves are almost linear with an increase in the degree of substitution. The cellulosic transition was indicated by the lattice conversion ratio, which showed an increase along with the degree of cyanoethylation. © 1993 John Wile

ISSN:0021-8995    

DOI:10.1002/app.1993.070470110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY