摘要:

AbstractThe interface reactions of 3‐aminopropyltriethoxysilane treated surfaces, with a polyamic alkyl ester/polyimide resin formed from pyromellitic dianhydride and oxydianiline, were defined by Fourier Transform Infrared (FTIR) analysis on the surface layers of germanium internal reflection plates. Adhesion between these interfacial layers is the result of chemical bonding, which apparently proceeds through initial amide formation between the amino function of the silylated surface and the alkyl ester group present in the polyamic ester. Heating results in diamide formation by a second alkyl, surface‐bound amine displacing the aromatic polymer amine. Heating the more stable dialkyldiamide to 300°C imidizes both the polymer and the interfacial region, producing a strong laminate composite. Polymer scission at the aromatic amide linkages occurs in this adhesion process, bonding surface‐bound alkyl amines to one end of a shortened polymer

ISSN:0887-6266    

DOI:10.1002/polb.1988.090260601

出版商:John Wiley&Sons, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractA novel driven‐rod, radiant pyrolysis technique has been used to study the steady‐state linear regression of vertically mounted poly(methyl methacrylate) and polypropylene rods degrading from the top under high‐flux, nonflaming conditions that simulate those of combustion. With this technique reliable temperature‐depth and oxygen‐depth profiles have been obtained and used to calculate the observed mass loss rates and to elucidate the mode of polymer degradation during combustion, respectively. For poly(methyl methacrylate) burning in this rod configuration, condensed phase oxidation is unimportant and the degradation mechanism is similar to that under more conventional slow‐heating conditions in the absence of air. In contrast, for burning polypropylene condensed phase oxidation occurs; the lack of oxygen incorporation suggests that the polymer degrades by oxygen‐promo

ISSN:0887-6266    

DOI:10.1002/polb.1988.090260602

出版商:John Wiley&Sons, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractPolyesters based on 4'‐hydroxyphenyl‐4‐hydroxybenzoate and dichlorides of dibasic acids, prepared using a high‐temperature solution polycondensation in 1‐chloronaphthalene, exhibit enantiotropic nematic mesomorphism. The range of temperatures for the nematic phase ΔtNcan be controlled by changing the number of methylene units in the repeating polymer unit. For n = 4, ΔtN= 97°C is the largest that can be obtained. Highernleads to smaller values of ΔtN. Whenn= 12, the polyester exhibits only one single C‐I transition. Forn>12 a smectic mesophase can be expected in this system. Strezlecki and Liébert reported a wide range of temperatures of ΔtN(70–160°C) for the Sn polymers made by the transesterification of 4'‐acetoxyphenyl‐4‐acetoxybenzoate and the dicarboxylic acids. We believe the latter reaction occasionally involves the internal ester linkage in the monomer unit, producing a copolyester having a random distribution of hard segment lengths and changed poly

ISSN:0887-6266    

DOI:10.1002/polb.1988.090260603

出版商:John Wiley&Sons, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractA thermodynamic model has been proposed for the simulation of monomer partitioning behavior in the dispersion polymerization of styrene in ethanol. The monomer concentration in the polymer particles is very low (20 vol% at 5% conversion) and decreases further as the polymerization proceeds. It is independent of stabilizer concentration but is strongly dependent on initial monomer concentration. The partitio n coefficient ([Mp]/[Mc]) of styrene increases from 0.8 to 1.1 with incresing conversion. There are two polymerization loci in dispersion polymerization, namely the continuous and polymer phases. Competition between solution and heterogeneous polymerization has been observed in this system. The rate of dispersion polymerization is dependent on initial monomer concentration but is independent of initiator concentration at higher conversions. The molecular weight of the polymers produced by this process increases with increasing conversion and decreases with increasing initiator concentration.

ISSN:0887-6266    

DOI:10.1002/polb.1988.090260604

出版商:John Wiley&Sons, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractA highly sensitive microcomputer‐controlled chemiluminescence apparatus capable of spectral resolution of emitted light has been used to study the oxidation of thermoplastic matrix material poly(ether ether ketone), PEEK, at 110°C in oxygen. Even after prolonged exposure and extensive decay in the chemiluminescence signal, the samples show no change in properties or accumulation of oxidation products. Evidence suggests that after oxygen‐assisted initiation, reaction proceeds by radical transfer primarily of polymer phenoxy radicals in a type of radical aromatic substitution reaction on PEEK. Similar substitution‐type biomolecular termination of polymer phenoxy radicals can lead to excited polymer and benzoquinone, emitters that account for much of the oxyluminescence spectrum of PEEK. Under the experimental conditions, the benzoquinone is volatile and the product polymer should be indistinguishable from starting p

ISSN:0887-6266    

DOI:10.1002/polb.1988.090260605

出版商:John Wiley&Sons, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractDifferential scanning calorimetric analyses were conducted on samples of poly(vinylidene fluoride) polymerized in an autoclave by tributylborane‐oxygen by free‐radical initiation at low temperature (‐70‐0°C). The peak melting points and the percent head‐to‐head defect in each polymer sample were determined by a reported calorimetric method. A commercial sample showed a melting temperature in the range 157–162°C and a percent head‐to‐head defect of 7.7%; whereas two experimental samples showed melting temperatures in the range 172–179°C with a percent head‐to‐head defect of 4.4 and 4.9%. The calorimetric procedure was modified by reducing annealing times to only 2 h, which saves time and, as shown in this study, avoids t

ISSN:0887-6266    

DOI:10.1002/polb.1988.090260606

出版商:John Wiley&Sons, Inc.    

年代:1988

数据来源: WILEY

摘要:

Abstract(N‐Ethylcarbazol‐3‐yl)methyl acrylate and methacrylate were polymerized anionically and radically. Anionically‐polymerized polyacrylate using ethylmagnesium chloride‐benzalacetophenone as catalyst is an isotactic rich polymer with 85% isotactic dyad. All polymers except anionically polymerized polymethacrylate showed good film forming property. Hole drift mobilities measured by the time‐of‐flight method at room temperature and at 5 × 105V/cm are in the following order: isotactic polyacrylate (1.0 × 10‐5cm2/V s)>atactic polyacrylate (1.8 × 10‐6cm2/V s)>atactic polymethacrylate (1.2 × 10‐6cm2/V s) at 5 × 105V/cm. These results are discussed in terms of the hopping model

ISSN:0887-6266    

DOI:10.1002/polb.1988.090260607

出版商:John Wiley&Sons, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractRF plasma‐deposited fluoropolymer films prepared from perfluoropropane were examined on a variety of metallic, glass, and polymeric substrates using electron spectroscopy for chemical analysis (ESCA) and Fourier transform infrared spectroscopy (FTIR). The F1s ESCA spectra of thin (<100 Å) depositions on some substrates exhibited a peak suggestive of ionic fluoride species. FTIR studies demonstrated the presence of bifluoride ion in some films. Angular‐dependent ESCA studies indicated that these ionic species were not located at the outermost surface of the deposition but rather near the fluoropolymer‐substrate interface. By depositing these fluoropolymer films on a large number of different metallic substrates, and comparing the results of thermal stability studies and solubility studies with literature descriptions of the properties of each of the respective fluoride salts, additional support for the identification of ionic fluoride species at the fluoropolymer‐substrate interface was generated. The implications of this interfacial ionic zone for the adhesion of plasma‐deposited fluoropolymer films to substrates are

ISSN:0887-6266    

DOI:10.1002/polb.1988.090260608

出版商:John Wiley&Sons, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractIt has been shown that butadiene initiated with potassium naphthalene in the mixture THF‐n‐hexane polymerizes conveniently rapidly. The active center is sufficiently stable below 0°C to produce narrow molecular weight linear polybutadiene. The two‐ended living polymer has also served to prepare ring polybutadienes. The analysis of the ring polymers by a high‐resolution set of SEC columns proved superior to the conventional method for the determination of the linear content in rings and in synthetic mixtures of rings and linear polymers. Dilute solution characterization of the linear and ring polymers shows thatgr′ = [η]/r[η]lis less than 0.66 in a

ISSN:0887-6266    

DOI:10.1002/polb.1988.090260609

出版商:John Wiley&Sons, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractThin films of the epoxy formed by the reaction of tetraglycidyl 4,4'‐diamino‐diphenylmethane and 4,4'‐diaminodiphenyl sulfone (73:27 w/w) were reacted with acrylonitrile (ACN) and isocyanates as blocking reagents for hydroxyl, amine, and epoxy groups. The water uptake at 30, 45, 55, and 70°C of the epoxy resin was monitored gravimetrically. At each temperature the epoxy exhibited case I or Fickian behavior. The diffusion coefficient D increased from 30 to 55°C, but decreased at 70°C because of the reaction of water with residual oxirane groups. Diffusion of ACN is accompanied by both reaction and polymerization, so equilibrium could not be reached. Sorption of the isocyanates essentially follows case I or Fickian behavior. Equilibrium moisture absorptions showed a correspondence between the reduction of moisture absorption and the number of blocked functional groups, irrespective of the nature of the blocking groups. Moisture absorption reductions as high as 68% were obtained. Moisture diffusion of the films after blocking with the various reactants exhibits case I or Fickian behavior. At 30°C,Dvalues are significantly higher for reacted films. At 70°C, the value ofDis unchanged as compared with the 30°C value for films reacted with ACN, butDvalues are significantly lower for films reacted with isocyanate blocking reagents as compared with the

ISSN:0887-6266    

DOI:10.1002/polb.1988.090260610

出版商:John Wiley&Sons, Inc.    

年代:1988

数据来源: WILEY