摘要:

AbstractThe 2‐hydroxyethyl methacrylate (HEMA)/ethyl methacrylate (EMA) graft copolymer system has been found to be a useful model for investigating blood/polymer interactions. Studies of the structure of both HEMA and EMA radiation‐grafted regions were conducted using extraction methods and transmission electron microscopy of selectively stained HEMA grafts. The effect of the extraction procedure on the surface topography of HEMA‐ or EMA‐grafted films was studied by means of scanning electron microscopy. The existence of internal cells in the bulk of the HEMA network was demonstrated, and their osmotic nature was investigated. As grafting proceeds, the HEMA network becomes increasingly porous. The extraction studies carried out on EMA grafted showed that with this system an increasingly dense structure is obtained as grafting p

ISSN:0021-8995    

DOI:10.1002/app.1987.070330101

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe photo‐induced graft copolymerization of methyl methacrylate onto nylon‐6 fiber was investigated using isoquinoline‐sulfur dioxide and α‐picoline‐sulfur dioxide charge‐transfer complexes as the photoinitiators. The graft copolymerization was carried out within the temperature range of 35–50°C and from the corresponding Arrhenius plot, the energy of activation has been evaluated. The effect of monomer, initiators, inhibitors, etc. on the graft yield has been investigated. The effect of solvent on the rate of grafting has also been investigated from which the chain‐transfer constant (Cs) of the solvent has been evaluated. The kinetic data and other evidence indicate that the overall polymerization takes place by a radical mechanism. The suitable mechanism has been suggested and the kinetic rate expression

ISSN:0021-8995    

DOI:10.1002/app.1987.070330102

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe degree of crystallinity of polyetheretherketone (PEEK) has been measured using both the density gradient technique (DGT) and differential scanning calorimetry (DSC). The difference in results between the methods was shown to depend on crystallization taking place during the heating scan in the DSC. By freezing the sample at different stages of the DSC thermogram and measuring its crystallinity in the density gradient column, the existence of induced crystallization for PEEK was established. Though this induced crystallization is not visible in the DSC thermogram, it must be taken into account when comparing the degree of crystallinity measured by the two methods. The induced crystallization was in turn interpreted as a result of an increase in crystal perfection that is also commonly observed during the initial stages of the annealing process. Accordingly, the effect of annealing on the crystallinity was also investigated. DSC scans on annealed samples exhibited a small endothermic peak at approximately 10°C above the annealing temperature. This peak was observed in both neat PEEK and its carbon fiber‐reinforced composite. Annealed PEEK shows, therefore, two melting transitions, a low one which depends on the annealing temperature and a high one which is independent of annealing temperature conditions. Collectively, the results of this study demonstrate that processing conditions and morphological features must be considered in characterizing semicrystalline‐based matrix polymers for high performance compos

ISSN:0021-8995    

DOI:10.1002/app.1987.070330103

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

年代:1987

数据来源: WILEY

摘要:

AbstractA simple method for estimation of dilute polymer solution kinematic viscosity versus shear rate curve at temperature of interest and activation energy for viscous flow through the use of efflux time measurement is demonstrated.

ISSN:0021-8995    

DOI:10.1002/app.1987.070330104

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

年代:1987

数据来源: WILEY

摘要:

AbstractDodecenyl succinic anhydride (DDSA), a liquid anhydride curing agent for epoxy resins, was synthesised from C12olefin and maleic anhydride by the “ene synthesis” reaction. C12olefin was prepared by the dehydration of lauryl alcohol using Al2O3(acidic) catalyst. The dehydration was carried out in a flow type reactor. The olefin collected was found to be a mixture of positional isomers of C12olefin. Systematic studies were carried out by varying the dehydration temperature, mode of feeding and flow rate of lauryl alcohol, and the C12olefin collected were converted into DDSA and mechanical properties of an epoxy resin–DDSA system were evaluated. The C12olefins and DDSA were characterized, and the properties correlated with structure and composition. It was found that DDSA derived from C12olefin with double bond near to the center of the chain gave better tensile strength than the DDSA derived from C12olefin with terminal double

ISSN:0021-8995    

DOI:10.1002/app.1987.070330105

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

年代:1987

数据来源: WILEY

摘要:

AbstractMechanical and dielectric properties of rubber mixtures of epoxy/polyurethane based on castor oil loaded with glass fiber is of great interest from a technological point of view. Epoxy resin was prepared from bisphenol A and epichlorohydrin in alkaline medium. Polyurethane was prepared from the hydroxyl group of castor oil reacted with 2,4‐toluene diisocyanate. Elemental analysis and infrared (IR) spectra are presented as evidence for the formation of these materials. A homogeneous solution of epoxy resin and polyurethane was prepared in acetone containing a curing agent 1,3‐propane diamine. The glass‐reinforced laminates were prepared by interacting polymer blends on the glass fiber through compression moulding. Chemical resistance to solvents, flexural strength, izod impact strength, and Rockwell hardness studies on a series of specimens were investigated. It was observed that they behave as tough materials. An attempt was made to study the effect of electrical conductivity by changing the compositions of rubber mixtures during reinforcement with glass fibers. The dielectric constant (E′) dielectric loss (E″), and loss tangent (tan δ) of the specimens and their dependence of temperature w

ISSN:0021-8995    

DOI:10.1002/app.1987.070330106

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

年代:1987

数据来源: WILEY

摘要:

AbstractTerminal epoxides display a group specific near infrared absorption at 4532 cm−1. This combination tone is reasonably free of interferences and can be employed to measure oxirane ring concentrations for epoxy coating resin systems during synthesis and crosslinking. With the use of low signal‐to‐noise FTIR supported by computer data manipulation, chloroform solutions of five commercially available resins were analyzed for epoxide equivalent weight and correlated with results obtained by perchloric acid titrations. The near infrared technique displays linearity for epoxy concentrations of 3.6–20.7 meq/L. Similar results were obtained via a serial concentration study, indicating that the technique is not strongly affected by matrix

ISSN:0021-8995    

DOI:10.1002/app.1987.070330107

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

年代:1987

数据来源: WILEY

摘要:

Abstract13C‐NMR spectroscopy and size exclusion chromatography have been used to determine the mean length of long branches in a number of high pressure process low density polyethylenes (LDPEs).13C‐NMR analyses count all branches longer than C5 as “long.” The polyethylenes studied all had 2–3 long branches per 1000 carbons. The mean branch length was of the order of 200–300 carbons in length. The size of long branches increases with increasingM̄nof the parent polyethylene, but the size of long branches relative to the overall macromolecular size decreases with increasingM̄n. The mean molecular weight of the long branches is some 5–20% ofM̄nof the particular polymer and decreases asM̄nincreases. Both autoclave and tubular reactor prod

ISSN:0021-8995    

DOI:10.1002/app.1987.070330108

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

年代:1987

数据来源: WILEY

摘要:

AbstractX‐ray diffraction, positron annihilation, electron microscopy and bulk density measurements are reported as a function of the degree of acetylation for a linters cotton. Heterogeneous reaction proceeds with a retention of ordered structure in the fibers. Substitution does increase the extent of disorder but is not sufficiently extensive to disrupt completely order at the fiber, fibril, micro fibril, and crystallite levels. The generation of disorder is associated with an increase in the interfibrillar distance, a breakup of the microfibrillar structure without a total disruption of the microcrystalline structur

ISSN:0021-8995    

DOI:10.1002/app.1987.070330109

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

年代:1987

数据来源: WILEY

摘要:

AbstractInfrared microscopy was used to determine di‐n‐butyl phthalate, dinitrotoluene, and methyl centralite diffusion profiles in cross sections of nitrocellulose‐based propellant grains. Absorbance of marker functional groups was determined at 25–50 µm intervals from the edge to the center of the sections. Comparison of IR and light microscopical data indicated that the optically visible boundary does not define the entire depth of deterrent penetration into propellan

ISSN:0021-8995    

DOI:10.1002/app.1987.070330110

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

年代:1987

数据来源: WILEY