摘要:

AbstractGels of syndiotacticity‐rich poly(vinyl alcohol) (s‐PVA) in mixed solvents of water/dimethyl sulfoxide (DMSO) or water/ethylene glycol (EG) were made by chilling at the temperatures of 0–70°C from those solutions with the polymer concentrations below 10g/dL. The melting points of the gels were measured warming the gel from the gelling temperature (Tgel) at a constant heating rate. The apparent enthalpy of fusion of a junction of gel, ΔHwas estimated from the relation between the apparent melting temperature and the polymer concentration. Thes‐PVA gels made from the mixtures of the water/lower contents of DMSO or EG had a minimum at lowerTgeland a maximum ΔHat a higherTgel. On the other hand, thes‐PVA gels made from the mixtures of the water/higher contents of them had nearly a maximum ΔHat a higherTgel. From those results, it was considered that the former gels received a high thermal history while the latter gels received only slight th

ISSN:0021-8995    

DOI:10.1002/app.1987.070340701

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

年代:1987

数据来源: WILEY

摘要:

AbstractEffects of bisphenol A type epoxy compounds involving various average molecular weights on the zinc stearate/calcium stearate and the cadmium stearate/barium stearate synergetic soaps induced thermal stabilization of poly(vinyl chloride) (PVC) were investigated by colorimetry. The remarkable stabilization effects of epoxides could not be observed on the PVC films without synergetic soaps, while the stabilization of PVC was markedly enhanced by combined use of epoxides and synergetic soaps. The appearance of excessive coloration of cool color producing metal chloride–polyene complexes which were an origin of abrupt discoloration of stabilized PVC was retarded by using epoxides together with synergetic soaps. Moreover, as for PVC with or without synergetic soaps, the epoxy compounds did not inhibit the formation of longer polyene chains which were a chromophore for yellow orange of aged PVC. Further colorimetries and IR or X‐ray photoelectron spectroscopies on the various PVC containing epoxy compounds and zinc chloride indicated that the epoxy groups caught the zinc chloride. The synergetic effect between epoxy compounds and synergetic metal soaps is ascribed to the action that the epoxides serve as an acceptor for the excessive cool color producing metal chloride produced from zinc stearate and cadmium stearate to retard the abrupt discoloration of stabilized

ISSN:0021-8995    

DOI:10.1002/app.1987.070340702

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

年代:1987

数据来源: WILEY

摘要:

AbstractMid‐ and near‐infrared (IR) spectroscopy has been used to study the curing of a bisphenol‐A based epoxy resin (EPON‐828) with a tetrafunctional curing agent, viz., meta‐phenylenediamine (MPDA). Three different cure cycles were used in the study. Primary amine functionality was observed to react relatively rapidly; none remained after curing for 2 h at 75°C. Secondary amine functionality was exhausted in epoxy rich samples subjected to the standard cure cycle (2 h at 75°C followed by 2 h at 125°C). In samples with stoichiometric amount or higher MPDA, complete reaction of secondary amine or epoxy groups was not observed. In amine‐rich samples subjected to post curing (6 h at 175°C), evidence was seen for the reaction of hydroxyl and epoxy groups, resulting in a considerable increase in the crosslink density o

ISSN:0021-8995    

DOI:10.1002/app.1987.070340703

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

年代:1987

数据来源: WILEY

摘要:

AbstractFlow‐rate effect on specific retention volume (V g0) was studied by eluting aliphatic, aromatic, and chlorinated aliphatic probes at infinite dilution on poly(n‐butyl methacrylate) stationary phase at different temperatures from −10 to 150°C, encompassing both the glass transition (Tg) and the softening temperatures of the polymer. The effect became pronounced as the temperature was reduced below 100°C.V g0decreased with an increase in the flow rate: first linearly at temperatures between 70 and 100°C, and then nonlinearly at all temperatures below 70°C. The retention diagrams ofn‐pentane, isooctane, and cyclohexane alone enabled the detection of glass transition. Dichloromethane gave a linear retention diagram throughTgwithout showing the f

ISSN:0021-8995    

DOI:10.1002/app.1987.070340704

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe synthesis of diallyl esters of linear dicarboxylic acids, and their use as multifunctional crosslinking agents for vinyl polymers, was studied. The number of carbon atoms in the chains of the diacids used varied from 2 to 10 in order to define the effect of the chemical structure on the reactivity of the crosslinkers prepared. Measurements of swelling in chloroform were performed to determine the average molecular weight between crosslinks, thus making an overall evaluation of the crosslinking efficiency. Sorption experiments were also carried out, using aqueous ethanol.

ISSN:0021-8995    

DOI:10.1002/app.1987.070340705

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe rate of hydrolysis of polyamide 6 in membrane casting solution containing strong mineral acid has been studied by determining changes in molecular weight, as estimated from dilute solution viscometry measurements. Hydrolysis is shown to be first order with a long half‐life of about 250 days. A two‐step dissolution process for polyamide 6 is proposed. The effect of extended dope maturation time upon polyamide 6 membrane preparation and performance has been examined. At short maturation times where protonation of polymer chain is occurring, flux is relatively low. A major increase in flux occurs after about 10 h, when protonation appear complete and hydrolysis has begun. Hydrolysis reduces polymer chain entanglement, and so quite different mechanisms for membrane formation exist as dope maturation time proceeds. With chains less than the critical entanglement length, nodular top layer membranes and alveolar walls lead to high water flux. However, such membranes are quite frag

ISSN:0021-8995    

DOI:10.1002/app.1987.070340706

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

年代:1987

数据来源: WILEY

摘要:

AbstractDevelopment of polyurea‐urethane and polyurea reaction injection molding (RIM) systems has created a need for kinetics of polyurea formation. Adiabatic batch reactions in solution were used to determine heats of reaction and relative reactivity of several aromatic amines andn‐butanol with phenyl isocyanate (PI). In addition to comparing times required to reach 25, 50 and 75% conversion for both catalyzed and uncatalyzed reactions,n‐th order models with Arrhenius rate constants were used to fit some of the exotherms. The reaction of 3,5‐diethyl toluene (2,4 and 2,6)‐diamine and PI could not be modeled due to unequal reactivity of the two amine groups. This unequal reactivity was studied using high performance liquid chromatography (HPLC) separation of the reaction products. The reactions of primary aliphatic amines and aromatic isocyanates were too rapid to be monitored in the batch apparatus. With a flow apparatus the reaction half time was estimated to be

ISSN:0021-8995    

DOI:10.1002/app.1987.070340707

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

年代:1987

数据来源: WILEY

摘要:

AbstractMolecular, hydrodynamic, and thermodynamic properties of nylon 11 in meta cresol and 1,1,1,2,2,2‐hexafluor‐2‐propanol (HFIP) solutions, as well as its distribution of molecular weights were investigated by means of viscosimetry, conductimetric titration of end groups, light scattering, and fractionation by successive precipitation. The studies were carried out on commercial samples as such (Mn= 14,900,Mw= 29,400) and on specimens prepared by solid‐state postpolymerization of the former (Mn= 35,000–43,000,Mw= 91,000–104,000). The results show the expected normal or Flory–Schulz distribution of molecular weights on the commercial sample (U= 1.03), and a broadened distribution on the postpolymerized one (U= 1.42), in agreement with previous observations on solid‐state postpolymerization of other polyamides. The intrinsic viscosity of the individual fractions was determined experimentally and the weight‐average molecular weights were calculated from the data of the fractionation (number‐average molecular weight and the mass fraction of polymer on each individual fraction) by means of an iterative numerical procedure. The parameters of the Mark–Houwink equation were, then, derived from the data of a large number of samples, including that corresponding to the whole, unfractionated polymers, spanning a range of about 100,000 units of molecular weight. The value of the exponent (a= 0.69) for solutions in meta cresol corresponds to the behavior of a linear, flexible macromolecule in a good‐solvent medium. The solutions in HFIP employed for the light‐scattering studies, on the other hand, display high values of the second virial coefficient (A2= 7.8 × 10−3− 5.6 × 10−3mol mL/g), suggesting that HF

ISSN:0021-8995    

DOI:10.1002/app.1987.070340708

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

年代:1987

数据来源: WILEY

摘要:

AbstractA new class of positive deep ultravoilet (UV) resists consisting of poly(p‐disilanylenephenylene)s was developed, in which a disilanylene unit and a phenylene unit are connected alternatively in the polymer main chain. These resists had very high etching resistance against oxygen plasma. The lithographic applications of a double‐layer resist system in which the poly(p‐disilanylenephenylene) film was used as the top imaging layer were examined. As a result, very high resolution and high contrast were attained. The double‐layer resist technique using organosilicon deep UV positive resist appears very promising for lithographic appli

ISSN:0021-8995    

DOI:10.1002/app.1987.070340709

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

年代:1987

数据来源: WILEY

摘要:

AbstractGlow discharge polymerization of hexamethyldisiloxane was carried out on activated charcoal granules through the application of capacitively coupled RF plasma. The coats were examined with Auger and IR spectroscopies, and with SEM. The surface topography and the tenacity of samples coated with plasma were compared with that of the solution‐coated ones. Mercury porosimetry was used to study the effect of the coat on pore size distribution. The effect of contact with blood on the number of blood cells were studie

ISSN:0021-8995    

DOI:10.1002/app.1987.070340710

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

年代:1987

数据来源: WILEY