摘要:

AbstractA time‐of‐flight mass spectrometer, used for the examination and identification of organic compounds, has been modified for the study of the thermal breakdown of complex organic materials. The development of the apparatus and examination of a range of polyurethane foams is descri

ISSN:0007-1641    

DOI:10.1002/pi.4980060102

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractDibasic lead phosphite is known to be a stabiliser for plasticised PVC against weathering. The stabilisation mechanism, however, is not known and could be due to absorption of u.v. radiation by the dibasic lead phosphite, or to an antioxidant action.It is suggested that the mechanism, in fact, depends upon an antioxidant action against the harmful effect of atmospheric oxygen absorbed during the test, and also that a similar effect occurs during thermal degradation of the PVC in free air. This beneficial effect is due to the presence of the phosphite grouping, but it is also necessary to have sufficient basic lead present to remove chlorine ions or radicals in the form of lead chloride. It has been found that equivalent molecular amounts of dibasic lead phosphite and normal lead phosphite are equally efficient in the presence of basic lead sulphate compounds.An interesting discovery is that the weather conditions during the early stages of an exposure test may be more important than the total radiation received by the test piece at a later date. The conditions in the early stages of a test influence the manner in which the basic lead stabiliser removes the harmful chlorine ions or radicals liberated from the polymer. Mild conditions allow sufficient time for lead to diffuse through the plastic to the surface region where it reacts to form a precipitate of lead chloride in the form of needle like crystals. Harsher conditions result in the basic lead stabiliser particles themselves absorbing the chlorine ions or radicals to form lead chlorine in situ.Tetrabasic lead sulphate improves the stability of the PVC by absorbing some of the harmful u.v. radiation with the result that the diffusion mechanism is favoured even under severe conditions.

ISSN:0007-1641    

DOI:10.1002/pi.4980060103

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractSome transverse mechanical properties of composites comprising uniaxially aligned continuous glass fibres embedded in a glass microsphere‐reinforced expoxy resin matrix have been determined from three‐point bending experiments.For a constant fibre volume fraction, the transverse modulus, strength, fracture surface energy for crack initiation and work of fracture are investigated as a function of microsphere content and compared with the equivalent two‐phase composites without beads.Modification of composite transverse properties are attributed to corresponding changes in matrix properties and comparisons are made with boundary expressions established for two‐phase particulate systems. The effects of voids, microsphere size and surface treatment on the properties are also e

ISSN:0007-1641    

DOI:10.1002/pi.4980060104

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractPolymers with phenylene groups in the main chain have been examined under uniaxial tension for their reactions to liquids. Preliminary results and critical values of the stress for breaking on liquid contact at room temperature are given.

ISSN:0007-1641    

DOI:10.1002/pi.4980060105

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractFlocculation of latex particles by a series of cationic polymers has been investigated, with special attention being paid to the effect of particle concentration. Both initial rate and ultimate extent of flocculation have been examined over a range of polymer concentrations, so that the onset of flocculation and of restabilisation could be established. At low particle concentrations, the effect of the polymers seems to be predominantly charge neutralisation; even high molecular weight polymers do not appear to form ‘bridges’, presumably because of the relatively flat configuration of the adsorbed polymer chains. However, at high particle concentrations, bridging flocculation may occur because adsorbed polymer chains require a finite time to attain their equilibrium configuration.Some practical implications of these findings are briefly discus

ISSN:0007-1641    

DOI:10.1002/pi.4980060106

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractNeedle‐like crystals of polyoxymethylene, grown in a polymerisation system of trioxane in solution with a cationic catalysis and considered to be single‐crystals of extended‐chains, were investigated by means of X‐ray diffraction. As for the molecular orientation in the crystal, a typical ‘fibre‐pattern’ with c‐axis oriented along the length was obtained from a specimen in which needles were embedded and aligned in a resin matrix. The degree of crystallinity, estimated from the diffraction diagram, was practically 100% (or not less than 95%) and the peak width of crystalline reflections, as narrow as a crystal of low molecular weight substance. Periodicity, as is seen in lamellar‐type crystals, was not observed by X‐ray scattering at small angle. The density measured was in a range, between 1.493and 1.505, which was not different from the

ISSN:0007-1641    

DOI:10.1002/pi.4980060107

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980060109

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980060110

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980060111

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980060101

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY