摘要:

AbstractThe characterization of poly(vinyl chloride‐g‐methacrylic acid) (PVC‐g‐MAA) films, prepared by the simultaneous‐irradiation technique, was undertaken through swelling measurements, attenuated total reflection infrared spectroscopy (ATRIR), scanning electron microscopy (SEM), electron spectroscopy for chemical analysis (ESCA) and thermogravimetric analysis (TGA). The per cent swelling of grafted PVC in various media increased with the increase in the graft level. A higher per cent swelling was observed in 0‐5m NaOH aqueous solution relative to that in distilled water. It is concluded from the ATRIR and ESCA studies that the concentration ratio of oxygen to chlorine atoms on the surface of grafted PVC increased compared with unmodified PVC, indicating grafting of methacrylic acid on to the surface. It was also found that the thermal properties of PVC improved after grafting with metha

ISSN:0007-1641    

DOI:10.1002/pi.4980220202

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractEpoxy resins of functionality 2–4 were reacted with 4,4′‐diisocyanato diphenyl methane within the range of isocyanate to epoxide ratios of 0.5–1‐5 in the presence of 2‐ethyl‐4‐methyl imidazole to form oxazolidone‐isocyanurate polymers. The state and extent of cure of the resins were followed by infrared spectroscopy in conjunction with differential scanning calorimetry. The ratios of isocyanurate to oxazolidone linkages in the cured resins were determined quantitatively by an infrared method and the glass transition temperatures of the corresponding structures were measured by differential scanning calorimetry and dynamic mechanical

ISSN:0007-1641    

DOI:10.1002/pi.4980220203

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractCotton cellulose has been treated with tetrakis(hydroxymethyl)phosphonium chloride (THPC), urea and small amounts of ammonium dihydrogen orthophosphate (ADP) to impart flame retardancy. Complexes of cell‐THPC‐urea‐ADP with transition metals such as chromium, manganese, iron, cobalt, nickel, copper and zinc have been characterized by reflectance UV‐visible spectra. The samples were subjected to differential thermal analysis and thermogravimetry from ambient temperature to 700°C in air to study their thermal behaviour. From the resulting data, various kinetic parameters for different stages of thermal degradation were obtained following the method of Broido. For the decomposition of cellulose and flame‐retardant celluloses, the activation energy was found to increase from 242 to 322kJ mol−1, the entropy of activation from 140 to 307 JK−1mol−1and the char yield from 2.5 to 31%. The free energy of activation for decomposition of cellulose and its derivatives was almost the same, viz. 148–162 kJ mol−1, indicating that the basic steps in the decomposition of cellulose and its derivatives are the same. The IR spectra of the thermally degraded residues of cell‐THPC‐urea‐ADP and its metal complexes indicate that dehydration takes place and a compound containing the carbonyl group is formed. The electron paramagnetic resonance signals indicate the formation of trapped and stable free radicals in the thermal degradation of cel

ISSN:0007-1641    

DOI:10.1002/pi.4980220204

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractAn attempt was made to clarify the effect of steam explosion conditions on the changes in morphology, degree of polymerisationPv, solubility towards aqueous alkali solutionSa, and supermolecular structure of a soft wood pulp and to elucidate the mechanism by which the steam explosion treatment makes natural cellulose completely soluble in aqueous alkali solution. For this purpose, scanning electron microscopic (SEM) observation and X‐ray diffraction, solid‐state cross‐polarisation/magic‐angle sample‐spinning (CP/MAS)13C nuclear magnetic resonance (NMR),SaandPvmeasurements were carried out on a series of soft wood pulps treated systematically by the steam explosion method. It was found that (1) the maximumSa(c. 100%) was obtained when the soft wood pulp was treated under the conditions of steam pressureP= 2.9MPa and treatment timet= 30s, (2) the decrease inPvof the pulp by the steam explosion resembled conventional acid hydrolysis of cellulose, (3) a higher water content in the sample to be treated gave a lower degree of decrease inPv, (4) the repeated steam explosion method gave more fibrillated sample with higherSathan the corresponding batch steam explosion, (5) the amorphous content of the samples as estimated by X‐ray analysis decreased by the steam explosion, in spite of an increase inSa, and (6) the structural parameters expressing the degree of breakdown in the intramolecular hydrogen bonds at the C3and C6positions,Xam(C3) andXam(C6), of the samples as estimated by CP/MAS13C NMR changed as functions ofPandt, being almost parallel toSa. This suggests that these parameters may be more closely correlated withSathan withXam(X) from X

ISSN:0007-1641    

DOI:10.1002/pi.4980220205

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractHigh‐molecular‐weight copolymers were prepared consisting predominantly of oxyethylene and oxymethylene‐oligo(oxyethylene) blocks with a small 1‐phenylethylene block. Ionic conductivities of mixtures of the copolymers with CF3SO3Li were m

ISSN:0007-1641    

DOI:10.1002/pi.4980220206

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThermoplastic rubbers made of triblock copolymers of styrene‐butadiene‐styrene in commercial formulations are commonly used in conjunction with petroleum extender oils, in order to reduce the melt viscosity of the rubber during its processing. These mineral oils contain known quantities of paraffinic‐naphthenic and aromatic molecules, which in turn are preferably absorbed by the rubbery and glassy phases respectively, affecting selectively the copolymer domain structure and thus the rheological and mechanical properties. Using a plasticizer, the melt viscosity of the system is reduced due to the plasticization of the phases, as expected. The melt rheological transition temperature shown by the unplasticized block copolymer is still present in the oil extended formulations. The flow activation energy is affected by the temperature, type and content of plasticizer. For temperatures lower than the rheological transition temperature the aromatic oil gradually weakens and destroys the polystyrene aggregates and the paraffinic oil induces a greater segregation of the polystyrene aggregates. At temperatures above the rheological transition temperature the behaviour of the two is similar because the flow is homoge

ISSN:0007-1641    

DOI:10.1002/pi.4980220207

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractGlass fibre reinforced epoxy composites were fabricated from the matrix resins diglycidyl ether of bisphenol A (DGEBA) and triglycidyl‐p‐aminophenol (TGAP) using diethylene triamine as curing agent. The epoxy laminates were evaluated for their mechanical properties, dielectrical properties and chemical resistance. Significant improvement in fiexural strength but a slight deterioration in dielectrical properties were observed on incorporation of an epoxy fortifier into the resin system before fabricating the composi

ISSN:0007-1641    

DOI:10.1002/pi.4980220208

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractMechanical properties of natural rubber/allyl acrylate and allyl methacrylate grafted cellulose fibre composites are presented. Stress/strain measurements and dynamic mechanical measurements indicate that the adhesion between grafted fibres and matrix is better than that in samples containing untreated cellulose fibres. This makes it possible to vary the composite properties by varying the fibre type and/or fibre amount.

ISSN:0007-1641    

DOI:10.1002/pi.4980220209

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractSeveral membranes prepared from poly(methylmethacrylate‐co‐methacrylic acid) and its Li+and Zn2+ionomers were tested for NaCl, creatinine and urea permeability. The permeabilities of the membranes were explained on the basis of pore contents determined from their scanning electron microscope micrographs. All the membranes showed higher permeabilities during the first 2 hours of experimentation. Introduction of Zn2+ions into the copolymer as crosslinking agent did not have much effect on the membrane properties but the properties of the copolymer were modif

ISSN:0007-1641    

DOI:10.1002/pi.4980220210

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstracttrans‐Polyoctenylene rubber, TOR, has been melt blended with PVC and with polystyrene, PS, in various proportions. PVC/TOR and PS/TOR blends were rigid, lending support to the claim that TOR improves dimensional stability of polymer and rubber blends. A processability study of PVC/TOR blends using a Brabender Plasti‐corder showed that TOR is a suitable processing aid for

ISSN:0007-1641    

DOI:10.1002/pi.4980220211

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY