摘要:

AbstractThe paper is concerned with the kinetics of radical conversions in solid polystyrene (PS) induced by decomposition of free‐radical initiators over the temperature range of 60–90°C. A complex quantitative study of PS oxidation was carried out. The kinetics of initiator decomposition and of hydroperoxide accumulation, the variations in chemiluminescence (CL) intensity accompanying polymer oxidation were studied. The CL spectrum and the changes in molecular weight in the course of oxidation were measured. A method for determination of the relative antiradical activity of antioxidants, based on the competition between the antioxidant and the stable radical for the active radical was proposed. The activity of valence‐saturated antioxidants in the solid phase was found to become more uniform compared to the liquid phase, whereas that of stable nitroxide radicals was abnormally high. Initiated solid PS oxidation occurred by a chain mechanism with formally linear termination of the chain. The chain length of 3.0 ± 0.5 was independent of temperature. A model of initiated PS oxidation is proposed. It implies structural inhomogeneity of the sample, resulting in different probabilities of radical formation in the polymer bulk in the course of initiator decomposition in various sample zones. The model permits quantitative description of the kinetics of hydroperoxide accumulation, stable radical consumption, and of variations in CL intensity during initiated and inhibited PS ox

ISSN:0360-6376    

DOI:10.1002/pol.1975.170130301

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe effect of the catalytic amount of H2O was investigated with the EtnAlCl3‐n‐VOCl3catalyst system on the alternating copolymerization of acrylic monomers with diolefins and styrene. The presence of the catalytic amount of H2O produced an improvement in the yield and in the molecular weight as well as the structure of copolymer with the EtnAlCl3‐n‐VOCl3catalyst system. The efficiency of the aluminum components in the EtnAlCl3‐n‐VOCl3system appears with AlEt3and especially with Et1.5AlCl1.5. The catalytic activity was found to depend upon the H2O EtnAlCl3‐nmolar ratio and was also affected by the order of mixing of the catalyst components and the monomers. Effective catalyst could be prepared when the catalyst components (except VOCl3) were premixed without presence of monomers. The possible catalytic behavior of H2O

ISSN:0360-6376    

DOI:10.1002/pol.1975.170130302

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractRadical polymerization of methacrylic acid (MAA) and acrylic acid (AA) in the presence of a positively charged macromolecular matrix was studied. In the presence of a matrix, the rates of polymerization were remarkably increased, especially in high pH region. This suggests that electrostatic interaction between the macromolecular matrix and the growing chains and/or the monomer molecules plays an important role in the process of polymerization reaction. The kinetic orders were greatly influenced by the relative matrix concentration (PC) as follows: for (PC)0>[M]0,Rp=k[M]0.9[PC]0.3[I]0.8≤ [M]0Rp=k[M]0.3[PC]0[I]0,8where [M] and [I]are monomer and initiator concentration, respectively, andkis a constant. The mechanism of the interaction of matrix with monomer and/or growing chains in the process of the propagation is discussed. The complex formed in the matrix polymerization could be easily made into fiber by spinnin

ISSN:0360-6376    

DOI:10.1002/pol.1975.170130303

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractPyrolysis of a commercial flexible urethane foam in an inert atmosphere was investigated by use of GCMS and chemical ionization mass spectroscopy. Pyrolysis products were identified and quantified at four pyrolysis temperatures. A mechanism is discussed in terms of the identified products.

ISSN:0360-6376    

DOI:10.1002/pol.1975.170130304

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractExperimental conditions have been defined for the steady‐state combustion of vertically positioned polymer rods burning at the top surface. Temperature and composition profiles through solid and gas phases of the system, polymer consumption rate, and flame height were measured, and the response of these parameters to changes of the oxygen concentration in the environment were determined. Measurements showed that unreacted oxygen diffused from the environment to the burning surface and was absorbed into the polymer, forming a well defined oxygen‐rich layer. Concentration of chemically bound oxygen at the surface of this layer were high, e.g., with polypropylene ca. 26 wt‐%, and identical with the stoichiometry of the gases leaving the surface and serving as fuel for the flame. The composition of the gas phase at the surface indicated the conversion of 11.4% of the hydrocarbon fuel to CO, CO2, and H2O. An energy balance for the system confirmed that fuel production in this surface layer takes place via simultaneous oxidative and pyrolytic degradation of the polymer, with exothermic processes supplying the energy for endothermic processes. Conductive and radiative contributions from the gas phase were found to play a minor role in maintaining fuel formation. The rate of degradation of a polymer to fuel, normalized to the area of the burning surface, was found to be independent of polymer supply rate and to increase with the oxygen concentration in the environment. The degradation process was successfully modeled in TGA experiments at temperatures and oxygen concentrations representative of the burning surface. The existence of an oxidative surface layer was confirmed and the TGA degradation rate related to the surface‐to‐volume ratio of the polymer sample. Compositional analysis of a methane diffusion flame of a geometry identical to that of the polymer flame, revealed the presence of unreacted oxygen throughout the preheating zone and at the surface of the burner. Conversion of fuel to final combustion products at the surface was 6.3%. Temperature and composition changes as a function of oxygen concentration in the environment were determined and compared with the polymer diffusion flame. It was concluded that a polymer flame, because of its autogenerative fuel production, possesses only one degree of freedom, viz., the oxygen concentration in the environment, in contrast to the conventionally fueled diffusion flame for which fuel supply rate is an additional independent parameter. Due to this single degree of freedom, the sensitivity of the polymer flame to environmental influences is increased. Effects caused by these extrinsic factors will be the subject of a separa

ISSN:0360-6376    

DOI:10.1002/pol.1975.170130305

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractA theoretical analysis has been made of the graft polymerization process in terms of the quantitative interrelationship between the initiation rateRi, thekp/kt1/ratio of the monomer, the equilibrium solubilityMof the monomer in the polymer, the polymer film thicknessL, and the diffusivityDof the monomer in the polymer. It is shown how the values of these parameters in any grafting system interact to lead to diffusion‐controlled graft polymerization. Whether graft polymerization is diffusion‐free or diffusion‐controlled depends on the values ofKp,d,kp/kp1/2, andLas gathered in the parameterA= [(Kp/kt1/2)Ri,D,/1/2]L/2. When the values of the various terms are such thatAis less than 0.1 (i.e.,Dis large whileRi,kp, andLare small), the reaction is diffusion‐free. WhenAis greater than 3 (i.e.,Dis small whileRi,kp, andLare large), the reaction is diffusion‐controlled. The derived equations showing the relationship between kinetic and diffusional parameters are theoretically applicable to all grafting systems, i.e., for all monomer‐polymer combinations under all conditions of reaction temperature, radiation intensity and polymer film thickness. The theoretical analysis has been verified for the rate and degree of polymerization for the radiation‐induced graft polymerization of styrene to

ISSN:0360-6376    

DOI:10.1002/pol.1975.170130306

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractSeven crosslinked polydimethylsiloxanes were prepared from carboxyl‐terminated siloxane oligomers of different average lengths and a trifunctional imine. The 10‐sec torsion modulus was measured as a function of temperature, and compression‐deflection data were obtained on swollen specimens. Polymer‐solvent interaction parameters were calculated from equilibrium swelling ratios and modulus data. The plots of modulus versus temperature show two distinct transitions for all the crosslinked polymers. The low‐temperature transition corresponds to the siloxane chains, whereas the high‐temperature transition should be attributed to the portion of the network chain derived from the crosslinking agent and the organic part of the oligosiloxane. On shortening the siloxane blocks, both transitions shift to successively higher temperatures and higher modulus levels. However, the siloxane transition temperature shows only a limited rise even when the average block length becomes quite small. The low siloxane polymers seem to exhibit two swelling maxima, each corresponding to one of the constituents. The studied materials from nonrandom copolymeric structures typical of block polymers. Such microphase systems can probably be expected in crosslinked polymers whenever the crosslinking agent participates significantly in the network chains and its compatibility with the flexible chains spec

ISSN:0360-6376    

DOI:10.1002/pol.1975.170130307

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractRing‐opening polyaddition of 4,4′‐disubstituted bisazlactones with various diamines was carried out inN‐methyl‐2‐pyrrolidone to afford polyamides with pendant amide group having inherent viscosities of 0.17‐0.51 in quantitative yields. The solution polymerization with aliphatic diamines was almost complete at room temperature within 24 hr. Nearly all of the polyamides were soluble in polar in polar aprotic solvents and in acidic solvents. These polymers began to decompose at around 200–300°C as determined by DTA and TG

ISSN:0360-6376    

DOI:10.1002/pol.1975.170130308

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractBis(2‐carb‐n‐butoxyethyl)methylphosphine oxide was prepared and condensed with 1,2‐diaminoethane, 1,6‐diaminohexane, 1,8‐diaminooctane, 1,10‐diaminodecane, and 1,12‐diaminododecane to form polyamides with an increasing number of methylene groups between the amide moieties. Polyamides made from the 1,10‐ and 1,12‐diaminoalkanes were shown by x‐ray and DSC to be semicrystalline, while those based on the 1,6‐ and 1,8‐diaminoalkanes were amorphous to x‐ray and revealed no first‐order transitions. The repeat distances of the crystalline polymers were determined, and an extended planar zigzag conformation was excluded as a possible conformation for these polymers. The thermal stability of the phosphorus‐containing polyamides, in both oxygen and nitrogen, was studied by TGA and the results were correla

ISSN:0360-6376    

DOI:10.1002/pol.1975.170130309

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe effects of triphenyl phosphite (TPP) on the radical polymerization of styrene (St) and methyl methacrylate (MMA) initiated with α,α,‐azobisisobutyronitrile (AIBN) was investigated at 50°C. The rate of polymerization of St and MMA at a constant concentration of TPP was found to be proportional to the monomer concentration and the square root of the initiator concentration. The rate of polymerization and the degree of polymerization of both St and MMA increased with increasing TPP concentration. The accelerating effect was shown to be due to the decrease of the termination rate constantktwith an increase in the viscosity of the polymerization systems. The chain transfer constantCtrof TPP in St and MMA systems was determined from the degree of polymerization system. TheCtrof TPP was almost zero in the St system and 6.5 × 10−5in the MMA

ISSN:0360-6376    

DOI:10.1002/pol.1975.170130310

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY