摘要:

AbstractElectroinitiated cationic copolymerisation of indene and styrene was investigated by constant potential electrolysis. Effects of copolymerisation potential and temperature on the copolymer composition and the reactivity ratios are discussed. The reactivity ratios of the monomers were calculated according to the integrated Lewis‐Mayo equatio

ISSN:0007-1641    

DOI:10.1002/pi.4980170301

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractAnalysis by infrared and nuclear magnetic resonance spectroscopy, differential scanning calorimetry and thermogravimetric estimation of the condensation products of hexamethylene diisocyanate and certain lignin model compounds bearing a free phenolic hydroxyl (prepared both in the melt at 100°C and in refluxing methylene chloride solution) shows that stoichiometric proportions give high yields of bisurethanes. These products decompose below 160°C to regenerate the starting material

ISSN:0007-1641    

DOI:10.1002/pi.4980170302

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThis paper discusses the thermo‐softening process of a triblock copolymer of styrene‐butadiene‐styrene. The specific volume vs temperature curve shows an anomalous expansion above ∼ 165°C, compared with a theoretical curve obtained from applying the simple law of mixtures to the pure components. The amount of crosslinking developed in the copolymer in terms of its gel content is found to increase suddenly, starting from 200°C and being fully developed at 230°C. Form birefringence vs temperature curves obtained during temperature cycling tests, show that a rearrangement takes place in the imperfect original domain structure above 145°C. This significantly increases the birefringence at room temperature. There is a maximum value of birefringence which is not destroyed even when the sample is heated up as high as 290°C. Dynamic mechanical thermo‐analysis shows a large broad peak for the tan δ in the studied region due to this rearrangement. The processes involved are, in general, irreversible although the specific volume vs temperature curve below 150°C

ISSN:0007-1641    

DOI:10.1002/pi.4980170303

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThe well known occurrence of different crystalline forms in polypropylene and their easy recognition in the polarising microscope has provided a method of analysing the behaviour of this material during the production of hot plate welds. The different thermal behaviour of the α‐ and the β‐forms of crystalline polypropylene allows estimation of the thermal history of the polymer in the region of the weld. In particular it is possible to estimate the amount of material actually melted by contact with the hot plate. The effect of the original crystalline microstructure of the components being welded on the microstructure of the recrystallised material forming the weld bond has also been explored. It is possible to characterise the general crystalline texture in the weld bead in terms of the shear and thermal history of the material. The influence of pre‐ and post‐welding annealing of the polypropylene has been investigated and a difficulty is encountered in explaining an apparent ‘memory’ of β‐form crystallisation which conflicts with established x‐ray d

ISSN:0007-1641    

DOI:10.1002/pi.4980170304

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThis paper examines several procedures for selective degradation of the preformed polymer component (polycarbonate) of certain types of graft copolymers. A procedure based on a two‐phase alkaline hydrolysis of the polycarbonate is identified as the preferred technique because it provides a clean system for the quantitative recovery and subsequent characterisation of the grafts. The application of the technique to a series of polycarbonate/polystyrene graft copolymers is reported. The kinetics of free‐radical graft polymerisation of styrene and the molecular weight distributions of the polystyrene grafts are compared with those for styrene homopolymerisation performed at the same rates of initiation. This comparison allows several differences between the kinetics of graft and homopolymerisation to be identified, both prior to and after gelation. These factors are interpreted in terms of modifications to the rate coefficient for bimolecular termination of the propagating grafts. Two (possibly three) factors are identified which influence the polymerisation kinetics prior to gelation; their influences are contrary and their relative importances depend on the rate of initiation. After gelation an additional effect, termed the network effect, comes into force and dominates both the rates of graft polymerisation and the molecular weight distributions of the gra

ISSN:0007-1641    

DOI:10.1002/pi.4980170305

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThe solid‐state polymerisation of the disubstituted diacetylene, 2,4‐hexadiynylene bis(p‐toluene sulphonate). has been studied by x‐ray diffraction in the temperature range 223 to 295 K. The variation in lattice parameters is shown to be similar to that reported in previous less extensive studies. This data is used to determine the behaviour of the thermal expansion coefficients as a function of polymer content. The relevance of these results to the question of polymer chain lengths at low conversion is di

ISSN:0007-1641    

DOI:10.1002/pi.4980170306

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThe trimethylsilylation of parabola vermiculite gives polyorganosiloxanes of the structure QxMy. (Q = SiO42: M = ((CH3)SiO12) which will form gels in a wide range of organic solvents and resins. No other mineral has so far been reported to yield trimethylsilylated products capable of forming gels. The effect on the nature and yields of these QM polyorganosiloxanes' of variation in reaction time, particle size and vermiculite/hexamethyldisiloxane ratio have been investigated. The QM polyorganosiloxanes produced are hydrophobic insoluble powders which gel in a wide range of organic solvents. Reaction with NaOH/EtOH mixtures gives ‘silicone‐silicate’ hybrids by replacement of trimethylsilyl groups with sodium ions. i.e. ‘QMNa’ products. The ability of these products to form films is compared to that of parabola vermiculite itself and also acid‐leached vermiculite. QM polyorganosiloxanes give films which can either be peeled off as an integral film or, after heating on a glass slide at 50°C. will give a hard hydrophobic surface. Preliminary investigation has also shown that QM polymers can be used as fillers in

ISSN:0007-1641    

DOI:10.1002/pi.4980170307

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThe mechanical properties (tensile strength, low temperature falling weight impact strength) of XENOY CL‐100 (a blend of polycarbonate and polybutylene terephthalate) have been studied. This blend is comprised of tough components and the property combinations that result may be useful for certain applications. The hydrolysis resistance of the blend in deionised water at 40°C has been studied. After 30 weeks it did not lose its tensile strength, but subsequently it did lose 50% of the low temperature (−70°C) falling weight impact strength. If the −70°C low temperature toughness is an important quality, this should be taken into account. However, the low temperature (−70°C) falling weight impact strength of pure polycarbonate and of pure poly(butylene terephthalate) is very low, whilst XENOY CL‐100 is still tough material, even after 30 weeks immersion at 40°C. Further study of the composition of XENOY CL‐100 showed that this blend is composed of polycarbonate. poly(butylene terephthalate) and crosslinked acrylic rubber; traces of titanium‐catalyst residue for the poly(butylene terephthalate) polymeristaion and black dye ha

ISSN:0007-1641    

DOI:10.1002/pi.4980170308

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThe problem of measuring quantitatively and reliably the proportions of methylene‐ and ether bridges in melamine‐formaldehyde resins has resisted chemical and spectroscopic approaches. Such measurements are specially required for refining statistical models of the overall crosslinking reaction. Pregel samples contain oligomer mixtures which can be freed from pendent methylols by treatment with ammonia. They obey the empirical formula (C3N6H6)1(CH2)R(H2O)z, whereRandzcan be found by optimising over measurements of %C, %N and %H. The accepted structures lead to prediction of z = −0.5R if only ether bridges are present or z= −Rif only methylene bridges are present. In principle, intermediate values of −0.5R>z>‐R could allow the proportions of the two kinds of bridges to be determined. However, over a wide range of ratiosRof formaldehyde to melamine, results are found to obey z = −0.2R, indicating retention of free water in the samples. Prolonged vacuum drying at room temperature may overcom

ISSN:0007-1641    

DOI:10.1002/pi.4980170309

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThe effect of a range of organic additives on the thermal stability of poly(vinyl chloride), both with and without a chloroparaffin extender, was studied using a number of experimental techniques. Of the additives used the best overall balance was provided by pentaerythritol, which increased stability when the extender was present and had no effect when it was absent. The congo red test emerged as the most suitable technique, being consistent and inexpensive and able to screen several additives simultaneously. Isothermal differential thermal analysis correlated with the congo red test but required more expensive equipment, was time‐consuming and demanded good mixing of the poly(vinyl chloride) compound to give reproducible results. Thermogravimetry was not sufficiently sensitive and the heat stability test was the least useful of al

ISSN:0007-1641    

DOI:10.1002/pi.4980170310

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY