摘要:

AbstractPoly(butyl methacrylate) (PBMA) was grafted onto wool in the presence of air and nitrogen atmosphere using potassium persulphate (KPS) and thioacetic acid (TAA) as redox pair under different reaction conditions. The percentage grafting and efficiency were compared. The graft copolymer was characterized by scanning electron micrograph, thermogravimetry, and molecular weight.

ISSN:0021-8995    

DOI:10.1002/app.1990.070400901

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

年代:1990

数据来源: WILEY

摘要:

AbstractPolyoxyethylene–polyamide multiblock copolymers were successfully synthesized from α, ω‐polyoxyethylene–dicarboxylic acid (POE–diacid), a mixture of two dicarbroxylic acids, and an aromatic discocynate by two synthetic routes, i.e., one‐step and two‐step method. In the two‐step method, α, ω‐diisocyanate‐terminated polyamide oligomers, preformed from a mixture of isophthalic acid (IPA) and azelaic acid (AZA) with 4,4′‐methylenedi (phenyl isocyanate) (MDI), were reacted with POE–diacid to form multiblock copolymers. In the one‐step method, the reaction components, MDI, IPA, AZA, and POE diacid, were reacted all together. These polymerizations were carried out in the presence of 3‐methyl‐1phenyl‐2‐phospholene 1‐oxide as a catalyst in tetramethylene sulfone, giving multiblock copolymers with inherent viscosities of 0.5–1.1 dL/g. They were soluble in amide‐type solvents, and transparent, ductile, and elastomeric films could be cast from theirN,N‐dimethylacetamide solutions. The tensile strength and modulus of the films thus prepared decreased with an increase in the polyoxyethylene content, whereas the elongation at break increased. The tensile strength/elongation at break/tensile modulus of the multiblock copolymer films ranged f

ISSN:0021-8995    

DOI:10.1002/app.1990.070400902

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

年代:1990

数据来源: WILEY

摘要:

AbstractSince 4‐vinylbenzylN,N‐diethyldithiocarbamate (VBDC) polymer easily cleaves at the C—S bond and generates benzyl radical, graft copolymerization of methyl methacrylate (MMA) or 4‐vinylpyridine (VPy) onto VBDC polymer is easily performed by UV irradiation. The structural analyses of the graft copolymers are performed through glass transition temperature measurements. The graft copolymers of MMA have oneTgand VPy graft copolymers have twoTg's arising from the main and side chains. It becomes clear that the mode of side chains propagation is significantly different for each of the second monome

ISSN:0021-8995    

DOI:10.1002/app.1990.070400903

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

年代:1990

数据来源: WILEY

摘要:

AbstractThis work is aimed at determining the influence of molecular weight distribution, branch content, and thermal history on the dynamic mechanical properties of four high density polyethylenes. Molecular segregation as a function of crystallization conditions has been measured by means of differential thermal analysis, whereas infrared spectroscopy allowed us to relate the structural changes introduced by the use of different crystallization conditions with both molecular segregation and dynamic mechanical properties. The α‐relaxation is the most affected transition by thermal treatments. Molecular segregation plays an important role in the mechanical behavior when the amount of segregated material is big enough as to shield the effect due to the isothermally thickened crystals. The presence of a high degree of segregation brings about asymmetry in the α‐relaxation peak as well as detectable changes in the reorganization factor (which defines the degree of order within the system) obtained by infrared spectroscopy. The supermolecular structure is found not to affect the dynamic mechanical properties. The β‐relaxation depends on the branch content, whereas the λ‐relaxation remains constant regardless of structural characteristics and thermal

ISSN:0021-8995    

DOI:10.1002/app.1990.070400904

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe urea formaldehyde polymerization has been modeled using the functional group approach, which accounts for the formation of higher oligomers. The kinetic model involves four molecular species and three rate constants, as opposed to six as proposed in earlier studies. The experimental data of Price et al. have been curve fitted using our model, which is found to describe them very well in the entire range of temperature and urea formaldehyde ratio. Based on the activation energies, it has been argued that the reverse reaction step must involve the condensation product, water.

ISSN:0021-8995    

DOI:10.1002/app.1990.070400905

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

年代:1990

数据来源: WILEY

摘要:

AbstractPolyacrylonitrile (PAN)/polythiophene (PTP) composite films were prepared by polymerizing thiophene vapor in PAN films impregnated with sulfuric acid or aluminum chloride as an initiator. After polymerization of thiophene for 1 h, the electrical conductivities of composites reach in the range of 10−7–10−3S/cm depending on the initiator and its concentration. The stability of conductivity to ambient air exposure is excellent. The transparency of composite films has been estimated by transmittance at the maximum absorption wavelength of 593 nm. The transmittance of composite film prepared with 10% of sulfuric acid on the weight of PAN reaches above 90%. The transparency has been maintained for the period of experiment, i.e., 1 month under ambient air exposure. Sulfuric acid is more effective than aluminium chloride for the preparation of transparent conducting PAN/PTP composite

ISSN:0021-8995    

DOI:10.1002/app.1990.070400906

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

年代:1990

数据来源: WILEY

摘要:

AbstractA series of poly(p‐oxybenzoate‐co‐p‐phenylene isophthalate)s were prepared by melt polycondensation ofp‐acotoxybenzoic acid,p‐phenylene diacetate, and isophthalic acid followed by solid‐state polymerization. The solid‐state polymerization not only increased the molecular weight, but also annealed the copolyesters. The thermal stability, liquid crystallinity, thermal properties, and solid‐state crystallinity of these copolyesters were investigated by TGA, polarized microscope, DSC, and wide‐angle X‐ray diffraction, respectively. It was found that copolyesters with HBA content of 50, 60, and 70 mol % showed explicit melt birefringence at 370°C and thus exhibited liquid crystalline state. The effect of annealing during solid‐state polymerization on the thermal properties was discussed. The effect of copolymerization on their crystallinity was interpreted with X‐ray

ISSN:0021-8995    

DOI:10.1002/app.1990.070400907

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe incorporation and release of sulfadiazine, paracetamol, diazepam, quinine hydrochloride, and doxycycline hydrochloride in and from rectangular slabs of highly crosslinked citric acidglycerol copolymer matrix have been described. The release of the drugs in phosphate buffer of pH 7.4 and at 37°C was followed spectrophotometrically. After an initial burst, the first three drugs were released up to 4 days and the last two drugs up to 7 days at almost constant rates. The erosion profile of the drug‐free matrix and the release characteristics of the drug‐loaded slabs under physiological conditions indicate hydrolytic erosion of the slab from the surface as well as from the bulk. It has been suggested that the zero‐order release of the drugs was possible due to a balance between the decreasing release rate by diffusion through the matrix and the increasing release rate because of increasing polymer permeability resulting from gradual crosslink cl

ISSN:0021-8995    

DOI:10.1002/app.1990.070400908

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

年代:1990

数据来源: WILEY

摘要:

AbstractSufficient fractionation was attained for polyacetal copolymers by the column elution method. The characteristics of molecular weight, composition, and sequence length of the original copolymers were evaluated through the analyses of fractions by1H‐NMR, GPC, and DSC. Comonomer content in polymer fractions decreased with the increase of molecular weight in any samples, and the copolymer prepared by gas‐phase polymerization showed broad compositional distribution as compared with that by solution polymerizat

ISSN:0021-8995    

DOI:10.1002/app.1990.070400909

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

年代:1990

数据来源: WILEY

摘要:

AbstractWater‐soluble copolymers ofcis‐butenedioic acid (MA) with sodium methallylsulfonate (SMAS) were prepared in aqueous solution using potassium persulfate (KPS) as the initiator. The effects of reaction conditions (e.g., monomer concentration, initiator concentration, monomer fractions and pH, reaction temperature and times, etc.) on the copolymerization were also studied. The results showed that higher conversion could be obtained under suitable conditions (see Figs. 1–5). The copolymers were characterized by IR and NMR spectroscopy. The ratios of infrared absorbances at 1585 cm−1(carboxyl absorption) and 1048 cm−1(sulfonic group absorption) were used to de‐termine the composition of poly(MA‐co‐SMAS). The reactivity ratios were calculated by Kelen–Tudos method and Fineman–Ross method. Both the chemical analysis and the scanning electron micrographs showed that the copolymer has an excellent antiscaling effect o

ISSN:0021-8995    

DOI:10.1002/app.1990.070400910

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

年代:1990

数据来源: WILEY