摘要:

AbstractAnalysis of various time‐conversion curves obtained with different AIBN‐concentrations at 65°C led to relative rate constants of conversion in the liquid and precipitated phase. Due to the density difference between the two phases, the time‐ and conversion‐dependent volume concentration of the initiator and the conversion‐dependent volume concentration of the free liquid and polymer‐dissolved monomer could be calculated per unit volume of suspended reaction mixture. By this calculation, the molar concentrations of all reactants were given for each point on the time‐conversion curves. On the basis of known kinetic equations a correlation could be achieved between conversion in the range up to 70% conversion and time by using the time integral of the effective initiator concentration. Exact correlation revealed a side reaction of the initiator AIBN, which was supposed to be due to small traces of oxygen. The desactivated initiator amount is nearly constant over all polymerization runs with different initial initiator concentrations. Taking this into account, the experimentally determined time‐conversion curves coincide with the

ISSN:0449-2994    

DOI:10.1002/polc.5070330102

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

年代:1971

数据来源: WILEY

摘要:

AbstractPoly(vinyl chloride) (Cobex) sheet was oriented by hot drawing. Double cantilever beam cleavage specimens were then cut out parallel to the direction of molecular alignment. The fracture surface energy and fracture surface features were then investigated as a function of the birefringence, a measure of the degree of molecular alignment. Two different modes of crack propagation were observed. The first mode was by local plastic deformation at the crack tip coalescing voids present in the material and giving a dimpled fracture surface. This occurred up to a birefringence of 2.55 × 10−3and was accompanied by a sharp fall in fracture surface energy with increasing birefringence. The second fracture mode was by smooth cleavage, this occurred above a birefringence of 2.13 × 10−3and was accompanied by a slight decrease in fracture surface energy with increasing birefringence. There was a transition region at intermediate birefringence values where both modes of fracture were

ISSN:0449-2994    

DOI:10.1002/polc.5070330103

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

年代:1971

数据来源: WILEY

摘要:

AbstractFollowing a previous study of two commercial poly(vinyl chloride) polymers, with Mwvalues of 130,000 and 70,000, the influence of γ radiation on the concentrated solutions of two other polymers in tetrahydrofuran was investigated. Their Mwvalues were 51,000 and 700,000, respectively; the second sample being crosslinked by copolymerization with a polyfunctional monomer.The irradiation‐induced changes were investigated by osmometry, light‐scattering, gel permeation chromatography and dilute and concentrated solution viscometry. From the experimental data obtained, it can be seen that the viscosity‐molecular weight relations are strongly affected by the molecular weight distribtuion and the presence of branching in the samples. By assuming the Stockmayer distribution, and using the equations developed by Kilb, the viscosities of the irradiated samples have been described satisfac

ISSN:0449-2994    

DOI:10.1002/polc.5070330104

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

年代:1971

数据来源: WILEY

摘要:

AbstractUnder the assumption that poly (vinyl chloride) (PVC) contains a negligible amount of long branches, simple kinetic considerations lead to the result that the molecular weight distribution (MWD) function resulting from a heterogeneous polymerization will be in accordance with the functional expression for the most probable distribution (mpd). A comparison between the experimental MWD curves determined by gel permeation chromatography (GPC) and the mpd supports this hypothesis and it is shown that the form of the MWD of PVC is very close to or identical with the mpd. Furthermore, it is found that PVC samples prepared by heterogeneous polymerization in the temperature interval 25–55°C have approximately identical distributions when normalized molecular weights are used. The degree of long chain branching is estimated to be equal to or less than 2 × 10−4long branches per repetition

ISSN:0449-2994    

DOI:10.1002/polc.5070330105

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

年代:1971

数据来源: WILEY

摘要:

AbstractA new theory of solution thermodynamics is outlined. The energy and enthalpy are related to the contacting areas of the chemically different kinds of molecular segments, the energy per unit contact area for each kind of contact, and an equilibrium constant. Departures of the entropy of mixing from the classical Raoult's law relationship result from differences in the volumes of solvent and solute molecules, from departures from perfect randomness of mixing, and from the concentration dependence of the orientational randomness of the bonds in the molecules. Simple equations for these relationships have been tested. Quantitative agreement is usually obtained.Examples are given of applications of the theory to polymer solutions. Application to poly(vinyl chloride) solutions has not yet been made, but the appropriate procedures and methods for determining the parameters are discussed.

ISSN:0449-2994    

DOI:10.1002/polc.5070330106

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

年代:1971

数据来源: WILEY

摘要:

AbstractThe earlier results concerning the kinetics of polymerization and initiator consumption, molecular weight distribution, and the nature of the chain ends in the polymerization of vinyl chloride initiated by tert‐butylmagnesium chloride (tBuMgCl) in tetrahydrofuran and other solvents are rediscussed in terms of the simultaneous participation of an ionic mechanism and a radical mechanism. The former is operative mainly at the beginning of the process and gives very low molecular weight products. The latter is responsible for the formation of the high polymer. The radicals are generated from the organomagnesium compound giving a tert‐butyl group as a chain end for every macromolecule. New experiments support the radical mechanism: comparison with radical polymerizations in the same conditions of temperature and solvent medium, inhibition by NO, copolymerization with vinylidene chloride. Also the high polymer is not obtained if the ionic mechanism is exalted by introduction of a powerful solvating agent, the dimethoxyeth

ISSN:0449-2994    

DOI:10.1002/polc.5070330107

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

年代:1971

数据来源: WILEY

摘要:

AbstractA sample of poly(vinyl chloride) having a very good thermal stability and a high initial crystallinity was annealed between 80 and 260°C, either as it was or mixed with stabilizers, in sealed ampoules or in KBr pellets, and studied by X‐ray and IR techniques. When the sample is treated in glass ampoules, practically no changes in IR spectra are observed up to 240°C; the X‐ray diagrams, however, show an increase in the size of the crystallites but no increase in the amount of crystalline material. The melting point is observed by X‐ray between 250 and 260°C. If the sample is heated in the KBr pellets, it undergoes some stress which causes an increase of the crystalline IR bands at 604 and 635 cm−1, but no change in the X‐ray diagram. At higher temperatures, dehydrochlorination is enhanced by the KBr and involves chiefly the amorp

ISSN:0449-2994    

DOI:10.1002/polc.5070330108

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

年代:1971

数据来源: WILEY

摘要:

AbstractPoly(vinyl chloride) sheet was oriented by hot stretching at 80°C. Yield stresses in simple tension and compression were measured at 20°C and at a strain rate of 100% min−1as a function of the angle between the test‐piece axis and the hot‐stretch direction. Simple tensile and compressive yield stresses were also measured in the temperature range −40°C to +80°C, in the hot‐stretch direction at strain rates of 100% min−1and 1% min−1, and in the unstretched sheet at 100% min−1. The results are discussed in terms of a yield criterion based on that of von Mises but modified to allow for the effects of anisotropy, internal stress and mean normal stress, and are held to justify the inclusion of the internal stress term. By making specified assumptions, the magnitude of the internal stress term is separated from that of the normal stress term and shown to rise slightly with testing temperature and to be only two‐thirds as great at the lower strain rate. A reason is given for thinking that the strain‐rate effect may

ISSN:0449-2994    

DOI:10.1002/polc.5070330109

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

年代:1971

数据来源: WILEY

摘要:

AbstractTest rings 0.8 mm thick are loaded about 125 N/cm2and the creep is measured for 100–200 minutes. The load may be varied from 75–200 N/cm2.Increase of length (δ) is plotted versus log time which gives a linear relation. δ is converted to elongation [ε = (δ × 100)/1o], and the slope of this line α = Δε/(Δ log time) gives further a linear relationship plotted versus temperature or 1000/T, the energy of activation being 5–7 kcal.The creep is measured in the temperature interval 20–100°C where the increase of log α is between 0.01–0.015/°C. We have tested variation of plasticizers content from 30–80 parts per 100 part resin and resins havingMWfrom 75,000–150,000. TheMWwas determined by means of gel permeation chromatography (Waters Associates).Together with α the elongation after creep of one minute represents another rate parameter, the logarithm of which is linear versus temperature.In the case where log α exceeds 1.8–i.e., an increase of 63% elongation per decade of time–the sample will break after varying times depending upon amount of plasticizer andMw.The method covers a wide range of creep and new plasticizers and resins may be characterised by the positio

ISSN:0449-2994    

DOI:10.1002/polc.5070330110

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

年代:1971

数据来源: WILEY

摘要:

AbstractDielectric dispersion and absorption spectra of plasticized polyvinyl chloride systems were investigated in order to obtain information about the efficiency and compatibility of the plasticizer.Dielectric spectra were measured as a function of temperature at a constant frequency and a constant heating rate within the range of −170 to +150°C.The glass transition temperature [Tg] is found to be dependent on the quality (structure) and quantity of the plasticizer used. The dipole‐dipole interactions, and thus also the plasticizing effect, are characterized by the dielectric permittivity change [Δet] in the transitions range.Dielectric spectra of compounds prepared with either commercial or special‐type plasticizers were measured. The effect of the chemical structure on the dielectric spectra was studied on a series of compounds containing phthalate‐type plasticizers having alcoholic side chains of an increasing length. The results of dielectric measurements are compared with those obtained by standard mechanical tests.From this comparison of results it may be concluded that the investigation of dielectric spectra offers important information regarding the efficiency and compatibility of pla

ISSN:0449-2994    

DOI:10.1002/polc.5070330111

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

年代:1971

数据来源: WILEY