摘要:

AbstractThe term “thermal analysis” now refers to a set of techniques which measure the response of a specimen to a linearly varying temperature. They are versatile techniques with particular value for polymer science. The applications of the various thermoanalytical methods to the study of fusion, crystallization, glass transition, thermal degradation, oxidation, and crosslinking reactions and the use of the results in polymer science and technology are discus

ISSN:0360-8905    

DOI:10.1002/polc.5070490113

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe methods used to examine forensic samples of commercial materials containing polymeric substances are summarized. The materials most commonly encountered are paint, textile fibers, fabrics, plastics, wire insulation, adhesives, adhesive tapes, and buttons. These materials are basically organic polymers which are filled to various extents with inorganic stabilizers, pigments, and/or extenders. The materials are therefore examined for both organic and inorganic constituents.Techniques used to examine organic constituents include infra‐red, pyrolysis and infra‐red, pyrolysis gas chromatography, and chemical modification such as hydrolysis, followed by derivatization and gas chromatographic analysis of the derivatives.Techniques used to examine inorganic constituents include spectrography, x‐ray fluorescence spectrometry, infra‐red, and scanning electron microscopy when coupled to an x‐ray

ISSN:0360-8905    

DOI:10.1002/polc.5070490114

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

年代:1975

数据来源: WILEY

摘要:

AbstractA short review of multiphase polymer composites is given, biased towards some as yet unexplained observations. It is proposed that the interface between the two phases of such polymers has an important influence on the properties observed. It is also suggested that careful study of the interface may lead to improved polymer properties. Some methods that may be applied for such studies are listed and briefly discussed.

ISSN:0360-8905    

DOI:10.1002/polc.5070490115

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe rates of alkaline hydrolysis of polyacrylamide chains attached to polystyrene latex particles have been measured and compared with the corresponding values in free solution. The attached chains exhibited a significant reduction in rate. The magnitude of this reduction increased with decreasing molecular weight. Consequently, the rates of hydrolysis of attached chains were a function of their molecular weight; this contrasted with the apparent second‐order rate constants for the chains in free solution, which were insensitive to the molecular weight. The reduction in rate was attributed to the decreased accessibility of the amide groups to the hydroxyl anions when the polymer chains were attached to an impenetrable interfac

ISSN:0360-8905    

DOI:10.1002/polc.5070490116

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

年代:1975

数据来源: WILEY

摘要:

AbstractA simple analytical theory is developed to explore the effects of surfactants, whether ionic or nonionic, on the rate of polymerization of seeded systems. It is assumed that the average number of free radicals per particle is small (n<1), that termination is rapid, and that free radicals may exit from the particle.Some consequences of the variation of the kinetic parameters are explored numerically. It is shown that the radical capture efficiency decreases in the order electrostatic, steric, then electrostatic plus steric for these three different types of stabilization. The radical capture efficiency is shown to be very low (1 free radical captured in 103– 104) despite the absence of new nucleation. Possible reasons for the low efficiency are discusse

ISSN:0360-8905    

DOI:10.1002/polc.5070490117

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

年代:1975

数据来源: WILEY

摘要:

AbstractDiallylamines readily undergo free‐radical polymerization to form polymers which contain cyclic structures. Five‐membered rings predominate, and this conclusion is supported by ESR spectroscopy of the radicals formed in a flow system, by chemical characterization of the compounds formed under nonpropagating conditions, and by NMR spectroscopy of the polymers. The presence of substituent groups in the diallylamine molecule has an important bearing on the cyclization reaction. For example, methyl groups in the β‐position, (dimethallylamines) form a mixture of 5‐ and 6‐membered rings, and the presence of bulkier groups, as in methyl bis‐2‐tert‐butyl allylamine, can prevent reaction with certain free‐radical initiators. Similarly, increasing temperature results in an increase in the amount of 6‐, relative to 5‐, membered ring structures with N‐methyldimethallylamine. These results are generally similar to those obtained with the carbon analogues.From a theoretical viewpoint, the formation of the 5‐membered ring structure indicates that the generally accepted less stable primary radical is formed in preference to the 6‐membered structure which would contain a secondary radical. This apparent conflict is explained by the kinetics of the reaction and particularly the stereo‐electronic effects which operate in the transition state. Thus, the reaction can be under kinetic control and lead predominantly to 5‐membered ring structures, but when thermodynamic control starts to operate, e.g., at higher temperatures, the more stable 6‐membered ring structures may become significant. Changing the polymer structure from a predominantly 5‐membered one to one containing 6‐membered rings can be expected to alter the properties of the polyelectrolyte. Thus, differences in the titration curves have been noted, and the possibility exists of relating these differences to the polymerization condi

ISSN:0360-8905    

DOI:10.1002/polc.5070490118

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

年代:1975

数据来源: WILEY

摘要:

AbstractPulse radiolysis has been used to investigate the transient species formed in aqueous and methanolic solutions of styrene, α‐methyl styrene, methyl methacrylate, and butyl acrylate. The reaction rate constants for formation and disappearance of these species and their activation energies are reported.In aqueous solutions, the primary radical products of the radiolysis of water react with styrene. About 20% of the ·OH radicals and about 45% of the reducing radicals, eaqand ·H, give the benzyl radicals C6H5CHCH2OH and C6H5CHCH3, respectively. The remaining 80% and 55% give the cyclohexadienyl radicals HOC6H5CHCH2and C6H6CHCH2, respectively. In methanol solutions, the cyclohexadienyl radical C6H6CHCH2is the only one detected.The kinetic parameters for radical‐radical dimerization of methyl methacrylate and of butyl acrylate are similar, showing that the differences in termination rates observed for the conventional polymerization of these monomers are due not to electronic, but to viscosity‐stru

ISSN:0360-8905    

DOI:10.1002/polc.5070490119

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

年代:1975

数据来源: WILEY

摘要:

AbstractPolymerization rates of N‐vinyl pyrrolidone and corresponding activation energies depend on the nature of the polymerization solvent. This is mainly due to the influence of solvent polarity on the propagation reaction. The dependence of the termination rate on the viscosity of the polymerization medium has a relatively minor effec

ISSN:0360-8905    

DOI:10.1002/polc.5070490120

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

年代:1975

数据来源: WILEY

摘要:

AbstractMagnetic polymers, originally conceived in ion‐exchange form as a means of handling microbeads in a thermally regenerable desalination process, have now been prepared in a variety of configurations for use in a number of water purification procedures. Processes have been devised which employ magnetic polymers in filtration, in oil slick removal, and in the adsorption of metal ions.Suitably shaped particles, when magnetized, form a filter bed of high voidage volume. Tests have been run on a variety of turbid waters. The particles give considerably better performance as filter aids than the diatomaceous earth normally used. An extremely important advantage is that the magnetic filter aids can be recovered and reused after washing.Vesicular forms of magnetic hydrophobic polymers float on water and have application in the removal of oil spills from water surfaces. The oil becomes trapped in the voids between the particles; the resulting mass is readily removed from the water by magnetic means, after which the oil is separated from the particles simply by centrifugation. The particles and residual oil are then recycled.Magnetic ion exchangers, smaller in size than conventional resins, can be employed in continuous contacting systems, such as fluidized and semifluidized beds. When compared with normal continuous ion‐exchange systems, the same removal of ions can be accomplished using considerably less resin in a plant which is smaller, simpler, and much cheaper to constr

ISSN:0360-8905    

DOI:10.1002/polc.5070490121

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

年代:1975

数据来源: WILEY

摘要:

AbstractPositive electron resists are polymeric film‐forming materials which undergo predominantly main‐chain scission upon exposure to high‐energy electrons. The irradiated regions of a selectively “patterned” film may be removed by fractional dissolution, enabling processes such as chemical etching to be carried out on the exposed substrate. Foremost in determining sensitivity (the minimum dose required to render an image developable, i.e., to produce a molecular weight distribution significantly removed from the original distribution) is the G(scission). Poly(methyl methacrylate) (PMMA) has a sensitivity of ∼10−5C/cm2(G(s) ∼ 1.9) compared with poly(butene‐1 sulfone) (PBS) whose sensitivity is ∼10−6C/cm2(G(s) ∼ 12). The molecular weight and molecular weight distribution are also of extreme importance, e.g., the sensitivity of PBS can be increased to ∼4–5 × 10−7C/cm2using molecular weights>106with low dispersitivity. Obviously, care must be taken when comparing sensitivit

ISSN:0360-8905    

DOI:10.1002/polc.5070490122

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

年代:1975

数据来源: WILEY