ISSN:0959-8103    

DOI:10.1002/pi.4990260302

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractBlends of sulphonated polystyrene, neutralized with metal ions, have been prepared in various proportions with polystyrene homopolymer. Morphology, microstructure, and deformation modes of strained, cast thin films have been examined by transmission electron microscopy. Variables studied include blend composition and ion content. In blends of low ionomer concentration, the ionomer component phase‐separates and takes the form of small dispersed particles. With the increase of ion content, the average particle size increases and, as crazes develop in the matrix, particles elongate and fibrillate. These ionic crosslinked particles adhere well to the matrix, share in carrying the applied stress and reinforce the matrix polymer. Implications of these results for mechanical performance of bulk samples are discusse

ISSN:0959-8103    

DOI:10.1002/pi.4990260303

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractCrystallization behaviour of isotactic polypropylene/linear low density polyethylene (iPP/LLDPE) blends has been investigated by optical microscopy and DSC. Crystallization of iPP depends upon blend composition and thermal history. When blended with LLDPE, the crystallization temperature of iPP,Tc, decreased slightly. Crystallinity did not change in the range 0‐80wt% LLDPE; there were only slight changes in the crystalline structure, but LLDPE seemed to resist forming the β type of spherulites. Below 80 wt% of LLDPE, iPP was a continuous phase. The iPP spherulite growth rate was almost constant; however, overall crystallization decreased due to decreasing primary nuclei densi

ISSN:0959-8103    

DOI:10.1002/pi.4990260304

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractA survey of pipe installation damage in Australia has shown that when pipes are installed in water reticulation systems, they often have significant levels of damage or notches that can be considered as sharp, i.e. less than 25 μm notch tip radius. Experimental investigations of the effect of simulated sharp notches of varying depth on uPVC pipes subjected to a representative cyclic pressure regime show that there is a relationship between the depth of the notch and the cycles to failure. With damage less than 1·2 mm deep, corresponding to a stress intensity factor of 0·2 MPa,m, a fatigue crack threshold exists, below which cracks do not grow and consequently pipe lifetimes in excess of 100 years can be expected for pipes installed under such cyclic pressure conditio

ISSN:0959-8103    

DOI:10.1002/pi.4990260305

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractIn order to improve the flexibility and the anti‐static properties of poly‐(p‐phenylene‐terephthalamide) (PPTA), the copolymer ofp‐phenylene diamine,p,p′‐diaminodiphenyl ether and terephthaloyl chloride (PPDTA) was synthesized. This copolyamide PPDTA was mixed with electrically conductive polyaniline (PAn) in concentrated sulphuric acid solution, and was processed to form film, or fibre, of the new composite PAn/PPDTA with high strength and good electrical conductivity. The composite is a lyotropic liquid crystalline polymer with electrical conductivity 10−1S/cm. The surface morphology of the PAn/PPDTA composite consists of an oriented fib

ISSN:0959-8103    

DOI:10.1002/pi.4990260306

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractWool can be deaged both thermally and aqueously, resulting in disruption of the network of secondary bonds. The ensuing increase in mobility of the macromolecular chains manifests itself as a decrease in the glass transition temperature; hence this property can be used to monitor the ageing/deageing process. The extent and stability of the network that forms on ageing is a function of the temperature and time of formation. If samples are allowed to age for two consecutive periods of time at different temperatures then two independent networks are formed, each with its own characteristic glass transition temperature. The moisture content, thermal history and scan rate must be carefully controlled during any thermal analysis. It has also been shown that deageing can be used to facilitate the temporary setting of wool.

ISSN:0959-8103    

DOI:10.1002/pi.4990260307

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractInterpenetrating polymer networks (IPNs) of styrene‐butadiene‐styrene (SBS) block copolymers and polystyrene (PS) were prepared by sequential polymerisation. TEM micrographs of both the constituent block copolymers and their IPNs were obtained after staining with osmium tetroxide. It was found that images obtained after cryo‐ultramicrotoming of bulk samples were a more legitimate representation of block copolymer morphology than those obtained from solvent‐cast samples. Micrographs of both semi‐IPNs and true‐IPNs and bulk block copolymer reveal distinct microphase separation. An anisotropic domain morphology is found, with polybutadiene (PBD) being the continuous phase containing PS‐rich domains. Domain dimensions change with cross‐linking and block copolymer type. Image analysis and small angle X‐ray data were obtained to provide further quantit

ISSN:0959-8103    

DOI:10.1002/pi.4990260308

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractCopolymerization of methacrylic acid (M) and acrylonitrile (A) in bulk at 60°C gives a statistical copolymer. Through the use of1H,13C, DEPT and twodimensional NMR techniques, the observed resonances in the NMR spectra of these copolymers can be assigned, and thus provide detailed information about the microstructure of the polymer at the diad, triad and tetrad levels. Configurational effects have also been shown to play an important role, although in all cases the chemical shift differences resulting from configurational variation are smaller than those resulting from sequence variation

ISSN:0959-8103    

DOI:10.1002/pi.4990260309

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe technique of dynamic mechanical thermal analysis (DMTA), operated in the dual cantilever mode, was used to characterize the effects of frequency, crystallinity, molecular weight (MW) and the extent of thermal oxidation on the dynamic mechanical response of poly(ethylene oxide) (PEO). The glass transition temperature (Tg) of PEO (MW = 9 × 105Dalton) was found to be −44°C. For PEO (MW = 1 × 105Dalton) theTgis −39°C and this value increases by 2–9°C for every decade increase in the measuring frequency. Two minor, second‐order transitions of PEO are also discernible at −33 and 32°C. An inverse dependence ofTgon molecular weight was found in the molecular weight range studied and this is contrary to the Fox‐Flory theory. It was also found that a partially crystalline sample is obtained despite very rapid quenching of PEO from the melt into liquid nitrogen. Thermal oxidation of PEO before processing leads to an increase in the amplitude of the loss tangent peak. This reflects the effect of oxidation products in restricting polymer crystallization and the subsequent increase in the amorphous fraction of the polymer. The position of theTgpeak in PEO remains reasonably fixed with progressive ageing and this was attributed to crosslinking having occurred in addition to chain scission during

ISSN:0959-8103    

DOI:10.1002/pi.4990260310

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractStaining techniques, which reveal the heterogeneous nature of polymer oxidation, are reviewed. A sensitive staining technique is described which identifies the location and distribution of partially oxidized areas within the morphological structure of high density polyethylene (HDPE) powders and films. Gaseous sulfur dioxide (SO2) reacts specifically with the hydroperoxide groups in oxidized HDPE, producing macromolecular sulfates. Subsequent heating leads to the elimination of sulfuric acid and the formation of conjugated sequences along the polymer chains. Such conjugated regions can be readily identified using ultraviolet microscopy. The staining of oxidized polymers with gaseous reagents avoids problems, like extraction of oligomeric material, which are encountered when using conventional solvent‐based methods, e.g. 2,4‐dinitrophenylhydrazine stain

ISSN:0959-8103    

DOI:10.1002/pi.4990260311

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY