摘要:

AbstractThe thermal and photochemical oxidation of anthraquinone‐ andp‐benzoquinone‐doped polypropylene has been studied by absorption, luminescence, and infrared spectroscopy. Prior to irradiation, fluorescence and phosphorescence measurements showed that some of the anthraquinone and most of thep‐benzoquinone had been converted into their corresponding hydroquinones during processing. Thep‐benzoquinone, unlike anthraquinone, also imparted a blue coloration to the polymer before irradiation, which is associated with the formation of a quinhydrone complex (or complexes). These results indicate that the quinones are thermally reduced to their corresponding hydroquinones during processing by a mechanism of hydrogen atom abstraction from the polymer substrate. On photo‐oxidation, whereas anthraquinone acted as a photosensitizer,p‐benzoquinone acted as a ph

ISSN:0021-8995    

DOI:10.1002/app.1978.070220601

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe thermal degradationin vacuoof ethyl cellulose and cellulose acetate in the form of very thin films or bulk material between 230° and 320°C has been studied. With the ethyl cellulose films, volatilization (as measured by weight loss) was a first‐order process up to about 50% reaction, with an activation energy of 208 kJ/mole. This is about the same as that associated with the initial drop in intrinsic viscosity of the solid during bulk pyrolysis, in which very high molecular weight material, probably crosslinked, was formed at a later stage. The volatile products from ethyl cellulose included H2O, CO, CO2, C2H4, C2H6, C2H5OH, CH3CHO, unsaturated aliphatic compounds, and furan derivatives. Acetic acid and acetyl derivatives ofD‐glucose were produced from cellulose acetate. It is suggested that the polymers degrade by radical chain mechanisms, and a number of possible elementary steps are pro

ISSN:0021-8995    

DOI:10.1002/app.1978.070220602

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

年代:1978

数据来源: WILEY

摘要:

AbstractThree structural modifications of poly(γ‐benzylL‐glutamate) (PBLG), forms A, B, and C, were prepared by varying the casting solvents and casting temperature. From x‐ray analysis, infrared absorption spectroscopy, differential scanning calorimetry, and viscoelastic measurements, it is concluded that form A of PBLG is characterized by intramolecular stacking between the benzene rings in the side chain, form B exhibits intermolecular stacking, and form C has no stacking. The transition which corresponds to the breakdown of stacking of form A at 135°C is irreversible, while that of form B at 110°C is reversible. The degree of stacking is larger for form A than for form B. These structural features of the side chain region reflect the permeation and sorption behavior of carbon dioxide. Breakdown of stacking between benzene rings causes an abrupt increase in permeability in both form A and form B, and the permeation behavior for form A is not reversible, as is suggested from the irreversibility of the transition. The larger the degree of stacking, the lower is the amount of sorption. Although stacking is considered to affect the sorption site (solubility) and molecular motion, its influence on solubility is more evident in the temperature range up to ab

ISSN:0021-8995    

DOI:10.1002/app.1978.070220603

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe mechanism of foam inhibition in an aqueous sodium dodecylbenzene sulfonate (DBSNa) solution by temperature‐sensitive, water‐soluble poly(dimethylaminoethyl methacrylate) (PDM) was investigated. The solution's foam collapsing rate, % transmittance, surface tension, pH, temperature, and degree of hydrophobicity of PDM showed that aging a PDM–DBS solution 125 to 280 hr produced a turbid solution and effectively inhibited foaming. Likewise, controlling the pH at 4 ≤ pH ≤ 7 and increasing the hydrophobicity of PDM enhanced the foam‐inhibiting action of the polymer. The reaction between DBSNa and PDM was temperature dependent and the temperature effect was almost reversible. When compared with other available commercial antifoaming agents, PDM was found most effective in suppressing foam formation in aqueous DBS

ISSN:0021-8995    

DOI:10.1002/app.1978.070220604

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

年代:1978

数据来源: WILEY

摘要:

AbstractStyrene–methyl vinyl ketone copolymers, methyl methacrylate–methyl vinyl ketone copolymers, and styrene–methyl vinyl ketone–2,6‐di‐t‐butyl‐4‐acroylaminomethylphenol terpolymers as well as polystyrene and polypropylene have been weathered either by artificial irradiation or by outdoor exposure. The weathered products were analyzed using GC mass spectrometry, liquid chromatography, IR, UV, NMR, and wet analytical methods. Most of the weathered products proved to be low molecular weight polymers with various functional groups, and many low molecular weight compounds were identified. From the degradates of styrene copolymers, acetone, acetic acid, acetophenone, benzoic acid, formic acid, phenol, benzaldehyde, etc., were identified; from the degradates of methyl methacrylate copolymers, acetone, acetic acid, methanol, methyl methacrylate, methyl vinyl ketone, etc., were identified; and from the degradates of polypropylene, aliphatic acids up to propionic were analyzed. In many cases, the most abundant species was acetic acid. From polypropylene weathered outdoors for two years, 1.2 μl/g acetic acid was obtained. The degradates of styrene copolymers were found to contain fluo

ISSN:0021-8995    

DOI:10.1002/app.1978.070220605

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

年代:1978

数据来源: WILEY

摘要:

AbstractCompositionally and structurally varied copolymers all containingn‐octadecyl acrylate were prepared and evaluated as viscosity index improvers in a common base oil under conditions of low shear. Systems evaluated over a range of copolymer and blend composition were: copolymers ofn‐octadecyl acrylate with, respectively, methyl methacrylate, 2‐ethylhexyl acrylate, andn‐dodecyl acrylate; and homopolymers of poly(n‐octadecyl acrylate), prepared with a wide range of molecular weights. Properties were compared with those of blends of commercial methacrylate copolymers (acryloids) which had been freed of their entraining liquid. Mixtures of base oil with copolymers ofn‐octadecyl acrylate and methyl methacrylate, compared at fixed SAE viscosities, were the most efficient of all blends studied. They had the smallest rate of change of viscosity with temperature (as measured by their ASTM slopes), particularly in the composition region of incipient polymer precipitation at room temperature. Efficiency of certain of these composition was somewhat greater than that of the acryloids. A parameter that related concentration and weight‐average molecular weight was used to correlate all of the data for ASTM slope and viscosity. Empirical relations developed by using this parameter enabled rheological data to be estimated that agree within 6% of experimental values for the case of thermodynamically good base oil solvents. These data demonstrated the relatively small contributions of copolymer structure to viscosity inde

ISSN:0021-8995    

DOI:10.1002/app.1978.070220606

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe viscosities obtained for the copolymer blends of the previous paper were correlated with several relations derived to describe more fundamental behavior of polymer–diluent mixtures at both infinite dilution and finite concentrations. Only the most efficient blends showed any appreciable expansion of hydrodynamic volume as temperature increased from 25° to 98.9°C. However, in spite of restricted coil expansion, all of the copolymers were effective viscosity index improvers. The mechanism of viscosity index improvement in multigrade oils was shown to be largely regulated by the translational friction generated by the polymer coils. This greatly increased the apparent negative entropy change of the blends; the enthalpy change characteristic of the base oil was retained. Efficiency resulted from coil contraction at low temperatures, but enthalpy decrease below that of the base oil was small. In contrast, viscosity index improvement using higher molecular weight solvents was accompanied by large enthalpy increases. Thus, undesirably high viscosities resulted at low temperatures. The structure of these blends was uncomplicated by polymer chain entanglements; unit values of the Fox‐Flory exponent were obtained for the relation between viscosity and weight‐average carbon backbone length. The lack of evidence for coil compression in the thermodynamically miscible blends above a critical reduced concentration was anomalous. Intermingling of side chains and their interaction may have overcome normal excluded volume

ISSN:0021-8995    

DOI:10.1002/app.1978.070220607

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe melting transitions and heats of fusion were obtained by differential scanning calorimetry for the crystalline phase of the same mixtures whose rheological properties were reported in the previous two papers. Pour point temperatures were also determined. In addition, the same thermodynamic quantities were also collected for higher polymer concentrations in this work, thus encompassing the entire concentration range. The DSC scans revealed that the distribution of crystallite sizes characteristic of the bulk copolymers was retained in the blends. Phase diagrams indicated isomorphism in all systems studied. An equation was derived to predict the influence of diluent concentration on melting point depression of copolymers, in which one component crystallizes through its side chains but in which the side chains of the other remain amorphous. The difference between the experimental heats of fusion and the value for entirely crystalline poly(n‐octadecyl acrylate) were used to estimate extent of apparent cocrystallization of the different copolymers with the base oil. While this tended to increase with pour point‐depressant ability, concomitant crystallinity of wax and depressant were essential to successful wax crystal modification. A mechanism is proposed in which whole molecules of hexagonally packed copolymers are attached to wax nuclei and accumulate slowly a t low diffusion rates. Thus, growth occurs over small crystal areas and is considered responsible for the directing influence of copolymer depressant. The resulting small crystal sizes, accompanied by fast growth of rapidly diffusing paraffins on uncontaminated surfaces, promote more compact habits, like dendrites that postpone network formation to lower temperatures. It was concluded that a melting point difference of less than 25°C between bulk copolymer and base oil is required for successful pour point depression. Consequently, in this base oil, only copolymers with long amorphous side chains in a limited composition range, such as then‐octadecyl acrylate–2‐ethylhexyl acrylate copolymers, possessed sufficient lattice disorder to meet the specification. The rest produced gelation at higher te

ISSN:0021-8995    

DOI:10.1002/app.1978.070220608

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

年代:1978

数据来源: WILEY

摘要:

AbstractAdvanced methods of conducting and analyzing instrumented Charpy impact tests are described and used in measuring the initiation fracture toughnessK1cat a range of impact velocities and temperatures. Improvements developed in the impact testing of metals are discussed and applied in the toughness evaluation of polymers. In lower‐speed impact tests where load–displacement records are nearly linear, the maximum recorded load may be used to evaluateK1cby stress analysisKcalibration formula. In high‐speed impact tests, where the load trace is highly oscillatory, the fracture load to be used in the calculation must be derived indirectly. The indirect derivation of fracture load for this purpose from a “low blow” stiffness measurement and specimen deflection has been studied in detail, and the use of the periodic time of the “low blow” test has been found to offer a reliable method of calculating the sys

ISSN:0021-8995    

DOI:10.1002/app.1978.070220609

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe effect of various organic compounds on the birefringence equilibrium shrinkage and swelling of poly(ethylene terephthalate) filaments was studied. Evidence is presented that suggests the carrier action of the compounds is dominated by dispersion forces and that interaction between dye and the carrier in the fiber has been detected.

ISSN:0021-8995    

DOI:10.1002/app.1978.070220610

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

年代:1978

数据来源: WILEY