摘要:

AbstractWater‐borne enzymatic coating‐based dry chemistries have been used for more than 20 years, especially by diabetics, for self‐monitoring of blood glucose. Until now, it has been believed that enzymes work only in water and not in organic solvents. Synthesis of a hydroxylated acrylic polymer and the novel concept of dispersing enzymes have enabled us to design nonaqueous diagnostic coatings. These coating films gave excellent dose response and dynamic range. Additionally, these coatings can easily be ranged by a wide variety of antioxidants. In contrast, water‐borne coatings are extremely difficult to range. Furthermore, nonaqueous coating films produce color signals that are independent of the reaction time with excellent thermal stability. Molecular forces and thermodynamical considerations have been used to explain the performance of the new dry chemistries. An organic reaction mechanism of ranging has also been proposed for the nonaqueous system. © 1993 John Wiley&S

ISSN:0021-8995    

DOI:10.1002/app.1993.070471201

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

年代:1993

数据来源: WILEY

摘要:

AbstractA detailed examination has been undertaken of the influence of surface treatment on the adhesion of ultrahigh molecular weight polyethylene (UHMW‐PE) fibers to epoxy resin. XPS, SEM, FTIR–ATR, LRS, and contact‐angle measurements have been used to characterize the chemical and physical changes of the fibers. The results, taken together, suggest that the adhesion depends on three factors: (i) chemical bonding effects, after plasma treatment, with the introduction of various kinds of oxygen‐containing groups into the surface of the nonpolar polyethylene, which greatly improve the surface energy of the fibers; (ii) mechanical keying effects; and (iii) the nonpolar dispersion force. It is concluded that these three factors can be regarded as additive and the contributions from each of them to fiber/resin adhesion are different and change with increasing treatment time. The optimum results are obtained when their respective contribution reaches about 60%, 30%, and 10%. © 1993 John Wiley&S

ISSN:0021-8995    

DOI:10.1002/app.1993.070471202

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

年代:1993

数据来源: WILEY

摘要:

AbstractSix plastic films with varying chemical compositions in three different accelerated weathering environments were evaluated for disintegration. The films included two traditional films (LDPE and polystyrene), three with enhanced photodegradability (2% ECO and 10% ECO and LDPE with a vinyl ketone graft), and one with enhanced biodegradability (LDPE with 6% corn starch). The films were exposed to UVA‐340 bulbs to simulate sunlight while in fresh water, salt water, or no water conditions. Disintegration of the films was determined by monitoring the change in physical properties of tensile strength at break, elongation at break, and toughness at break at selected intervals throughout the exposure period. Both the chemical composition of the film and the exposure environment produced significant differences in disintegration rates. Two of the films with enhanced photodegradability (2% and 10% ECO copolymers) disintegrated more rapidly than did the other films in this study. The environment where no water was present resulted in the fastest disintegration rate for the films when compared with the fresh‐water environment. However, two films, LDPE and LDPE with 6% corn starch, degraded more rapidly in the salt‐water environment than in the other two environments due to the presence of oxidation catalysts in the water system. © 1993 John Wiley&Son

ISSN:0021-8995    

DOI:10.1002/app.1993.070471203

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

年代:1993

数据来源: WILEY

摘要:

AbstractA study has been made of the crystallization behavior of polypropylene (PP) filled with rare earth oxides under isothermal conditions. These rare earth oxides include lanthanum oxide (La2O3), yttrium oxide (Y2O3), and a mixture of rare earth oxides containing 70% Y2O3(Y2O3–0.70). A differential scanning calorimeter was used to monitor the energetics of the crystallization process from the melt. During isothermal crystallization, dependence of the relative degree of crystallinity on time was described by the Avrami equation. It has been shown that the addition of any of the three rare earth oxides causes a considerable increase in the overall crystallization rate of PP but does not influence the mechanism of nucleation and growth of the PP crystals. The analysis of kinetic data according to nucleation theories shows that the increase in crystallization rate of PP in the composites is due to the decrease in surface energy of the extremity surfaces. The relative contents of the β‐form in the composites are somewhat higher than that in the plain PP. However, the contents of the β‐form in the plain PP and the composites are all very low relative to those of the β‐form and the influence of the formation of the β‐form on the crystallization kinetics can be neglected. © 1993 John W

ISSN:0021-8995    

DOI:10.1002/app.1993.070471204

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe flammability behavior of a series of polychlal fiber/polyester fiber blends has been investigated in terms of the oxygen index and the thermal degradation characteristics. The thermal degradation behavior of these fiber blends has been studied by a conventional dynamic thermogravimetric technique in a flowing air atmosphere at several heating rates. Quantitative data are presented that pinpoint how the flammability behavior of the blends differs from that of the components. These results indicate that interactions occur between the polychlal and polyester fibers in the blends. © 1993 John Wiley&Sons, Inc

ISSN:0021-8995    

DOI:10.1002/app.1993.070471205

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

年代:1993

数据来源: WILEY

摘要:

AbstractComposite membranes were formed by deposition of plasma‐polymerized acrylic acid (PPAA) films onto porous commercial membranes to improve the rejection, especially of chlorinated compounds, in ultrafiltration of E‐stage bleach effluent. Although increased rejections were accompanied by reduced flux, in most cases, the reductions were not significant considering the extent of increased rejections. A good composite membrane showed the AOX removal of 94% (76% before the modification) and the chemical oxygen demand (COD) removal of 84% (67% before the modification) with 33% reduction of the flux. The permeate was optically clean. The improved rejection is attributed to the tightly crosslinked network of a plasma polymer film and its negatively charged surface. Ultrathin film thickness and the hydrophilic property of a plasma polymer film minimize the reduction of flux. © 1993 John Wiley&Sons,

ISSN:0021-8995    

DOI:10.1002/app.1993.070471206

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

年代:1993

数据来源: WILEY

摘要:

AbstractA series of 17 polymers was etched in the reactive ion‐etching (RIE) mode. The etch rates were monitored using a laser interferometer. The gases used were oxygen alone and a mixture of carbon tetrafluoride with oxygen (8% O2). The polymers fell into three groups: the aromatics (polystyrene and derivatives), the aliphatics (methacrylates and vinyl acetate), and the cellulosics (methyl ether and nitrate). In oxygen with a power density of 0.25 W/cm2, the etch rates for the three groups fell in the range of 200–300 nm/min, 350–450 nm/min, and 500–850 nm/min, respectively. The etch rates were also measured at a power density of 0.50 W/cm2. The etch rates at the higher‐power density were about 75–80% higher than those at the lower‐power density. The etch rate in the fluoride mixture was about half that in the oxygen, all other parameters being the same. Plasticizers that lower the glass transition temperature of polymers based on vinyl chloride, methyl methacrylate, or styrene do not change the etch rate of the polymers very much. There is a slight increase in the rate for polystyrene and a slight decrease in the rate for poly(methyl methacrylate). All the effects of composition on etching rate can be correlated to a first approximation with the molar fractions of carbon and oxygen in the resist. © 1993 John W

ISSN:0021-8995    

DOI:10.1002/app.1993.070471207

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

年代:1993

数据来源: WILEY

摘要:

AbstractStructural change of acrylonitrile–butadiene–styrene (ABS) terpolymer due to iodine doping has been reported using both infrared (IR) and thermally stimulated current (TSC) techniques. IR investigation revealed the presence of a new stretching band at 640 cm−1that indicates the formation of the C‐I structure. The TSC spectrum consists of two different decaying charge distributions of opposite polarity, which simply superpose to yield the net current observed. The variation of the position of the negative peak relaxation and its intensity as the iodine percentages increases indicates the formation of different ionic iodine species. The induced ionic dipoles superpose the α‐relaxation of ABS. © 1993 John Wile

ISSN:0021-8995    

DOI:10.1002/app.1993.070471208

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe crystallization kinetics of poly(ethylene terephthalate) was measured under isothermal conditions by DSC in the presence of various fillers and with varying filler concentrations. The fillers used were carbon, titanium dioxide, glass fiber, and calcium carbonate. The kinetics was calculated using the slope of the crystallization vs. time plot, the times for 10% and 50% reduced crystallization, and the Avrami equation. Activation energies were determined from measurements under different isothermal temperatures. The fillers caused athermal nucleation to be inhibited as shown by the increased values of the Avrami exponent,n. Interactions between the polyester and filler were interpreted to reduce the mobility of the polymer in the melt. This decreased the rate of crystallization and increased its activation energy. The order of the filler effect in reducing crystallization was the following: no filler

ISSN:0021-8995    

DOI:10.1002/app.1993.070471209

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe relative solubility of tetrachlorohexafluorobisphenol‐A polycarbonate was observed in 127 organic compounds comprising 14 different chemical classes at room temperature and up to about 225°C. The polymer is soluble in numerous esters, ketones, halocarbons, heterocyclics, and amides. It is poorly soluble in alcohols and fluorocarbons. Correlation of observed solubility with Hildebrand total solubility parameters was poor; a much better correlation was observed with Hansen three‐dimensional parameters. The solubility parameter of the polymer was estimated to be 9.1 (cal/cm3)1/2(18.7 MPa1/2) from the averages of the Hansen parameters for 26 experimentally identified solvents. © 1993 John Wiley&Sons

ISSN:0021-8995    

DOI:10.1002/app.1993.070471210

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

年代:1993

数据来源: WILEY