摘要:

AbstractSix vinyl phosphonates have been synthesized and evaluated as grafts on poly(ethylene terephthalate) for their flame retardance properties. Diethylvinyl phosphonate was used as a model for phosphorus‐containing flame retardants in developing the methodology for localizing flame retardants either on the surface of the filament or uniformly throughout it. SEM–X‐ray microprobe techniques were used in the verification of the location of the flame retardant in the filament. The flame retardance efficiency of poly(diethyl vinyl phosphonate) was then correlated with its location in the filament. Other grafted phosphorus‐containing flame retardants showed a range of efficiencies that depended not only upon the location of the graft within the filament but also upon the %P in the compound. The wide variations in flame retardance efficiencies of copolymers and terpolymers were attributed to large variations in the melt viscosity of the different grafted materials. The grafts showed only small changes in tenacity and large increases in elo

ISSN:0021-8995    

DOI:10.1002/app.1978.070220901

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe thermal degradation of PVC was studied at 190°C in pure nitrogen and nitrogen containing 10, 20, and 40% HCl (by volume). The rate of dehydrochlorination was determined by gravimetry. Degradations in nitrogen were followed with conductometry in addition. Changes in molecular weight distribution and degree of long‐chain branching (LCB) were determined by gel permeation chromatography–viscometry and polyene sequence distribution by UV spectroscopy. The rate of dehydrochlorination increases with the HCI content of the atmosphere. The rate of molecular enlargement also increases but only as a result of the increased dehydrochlorination rate. The increase inMwand LCB are thus related to the extent of conversion only. Changes in the UV spectra indicate that the increase in rate of dehydrochlorination is mainly due to increased propagation rate in atmospheres containing less than 10% HCI. At higher HCI contents an increase in initiation rate is noted. It is suggested that this, at least in part, is due to the fact that HCI, by forming a cyclic transition state, catalyzes the random elimination of HCI. This process, in turn, is promoted by the presence of polyene seque

ISSN:0021-8995    

DOI:10.1002/app.1978.070220902

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

年代:1978

数据来源: WILEY

摘要:

AbstractA new theory is developed which relates the graft level, graft molecular weight, and particle size to the probability of hitting a rubber particle as a crack propagates in a two‐phase impact‐modified plastic. It is shown theoretically that the particle size average of interest in evaluating the impact properties of two‐phase plastics is the surface‐average particle sizeDs. The theory predicts a maximum probable impact at a specific particle size that depends on the graft level required to achieve compatibility between the two

ISSN:0021-8995    

DOI:10.1002/app.1978.070220903

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

年代:1978

数据来源: WILEY

摘要:

AbstractCapillary rheometry was performed over a temperature range of 170°–200°C and a shear‐rate range of 3–3000 sec−1on an unplasticized poly(vinyl chloride) compound. The data were corrected for the effect of pressure on viscosity, for pressure loss in the barrel and at the capillary entrance, and for the non‐Newtonian velocity profile. The pressure coefficient of viscosity was found to be in the same order of magnitude as those previously found with linear polyethylene and butadieneacrylonitrile copolymers. The pressure–shear‐rate superposition of the flow curves is valid at least approximately, although the temperature–shear‐rate superposition is inapplicable. The shape of flow curves at 180°, 190°, and 200°C are concave downward when they are expressed as log‐shear‐stress‐log‐shear‐rate. Similar plots at 170° and 175°C, however, are very different; shear stress is independent of shear rate at low shear rates, increases somewhat and becomes independent of shear rate again at high shear rates. There is no detectable temperature dependence of flow behavior at 170° and 175°C. Irregularly shaped extrudates were obtained at higher shear rates. At constant shear rate the irregularity increased with the length of the capillary. The effect of thermal‐mechanical history on the particulate and crystalline structure is discussed with possible influence on the r

ISSN:0021-8995    

DOI:10.1002/app.1978.070220904

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

年代:1978

数据来源: WILEY

摘要:

AbstractA novel class of 3,9‐haloneopentoxy‐2,4,8,10‐tetraoxa‐3,9‐diphosphaspiro[5.5]undecane‐3,9‐dioxides has been synthesized. The method of preparation and physical properties of the compounds are described. The chemicals have been found to be excellent fire retardants for polypropylene. A polypropylene composition meeting the UL‐94 V‐0 specification can be achieved on both 1/8 and 1/16‐in.‐thick specimens with as little as 15% addition of one of these compounds. The use of a typical inorganic synergist such as antimony oxide is not required. The spirodiphosphates described exhibit good light, thermal, and

ISSN:0021-8995    

DOI:10.1002/app.1978.070220905

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

年代:1978

数据来源: WILEY

摘要:

AbstractVapor‐phase mutual grafting of methyl acrylate (MA) onto polyethylene (PE) and subsequent saponification treatment produce a surface graft having a high adhesive bondability, which results from the presence of a hydrolized homopolymer layer (consisting of only monomer component) on an inner graft copolymer layer consisting of both PE and monomer components. The oxidative deterioration and the stabilization of the grafted surface layer have been investigated to clarify the long‐term stability of the adhesive bondability. The bondability rapidly disappears with accelerated weathering followed by acetone extraction treatment, whereas it is kept unchanged during thermal‐oxidative aging at 100°C. Microscopic and ATR infrared spectroscopic observations of the degraded surfaces show that the bondability loss is due to degradative removal of the surface homopolymer layer. The addition of combinations of conventional antioxidants and ultraviolet absorbers stabilizes the grafted surface layer against thermal‐oxidative and photo‐oxidative degradation and thus extends the bondability retention time. The stabilization is more effective in the grafts of carbon black‐containing PE, where carbon black is present in the inner‐graft c

ISSN:0021-8995    

DOI:10.1002/app.1978.070220906

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

年代:1978

数据来源: WILEY

摘要:

AbstractIt has been found that sodium metabisulphite failed to initiate the polymerization of methyl and butyl acrylates but succeeded in polymerizing methyl, ethyl, and hydroxy propyl methacrylates. All the samples of the poly(hydroxypropyl methacrylates) were crosslinked, even those prepared at low conversions. Gel permeation chromatographic analysis indicated a multinodal molecular weight distribution, suggesting the existence of more than one mechanism occurring in such a heterogeneous system. It has also been proved by electron spin resonance that the polymerization process, using sodium bisulphite as the initiator in such a system, is a radical mechanism. The use of substances such as quartz, glass powder, and kaoline powder enabled the detection of the bisulphite radicals by trapping them. Using13C NMR spectroscopy, the estimated triad fractions from α‐methyl peaks and from quaternary carbon peaks of the poly(methyl methacrylates) and poly(ethyl methacrylates) showed that the polymers obtained were all predominantly syndiotactic in structure, as expected. The poly(ethyl methacrylate) samples were found to have a slightly higher syndiotacticity than the poly(methyl methacrylates), also as expected. The greater bulk of the ethyl ester group relative to that of the methyl ester group probably leads to greater steric hindrance in the isotactic and heterotactic triad (i.e., in a mesodya

ISSN:0021-8995    

DOI:10.1002/app.1978.070220907

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe thermal oxidation of natural rubbers fromHevea brasiliensis(pale crepe and smoked sheet) andParthenium argentatum(Guayule) were studied with differential scanning calorimetry (DSC) using the dynamic method. The atmosphere was oxygen at 110 ml/min and the temperature range was 393° −473°K. The decomposition reactions showed a pronounced exothermic emission with shoulders on the high‐temperature side. The kinetic parameters were computed by using three different mathematical approaches: the heat evolution treatment of Borchardt and Daniels, the diffusion‐controlled method by Jander, and the heating rate method developed by Kissinger and Ozawa. The best agreement between these methods was achieved assuming first order in the Borchardt and Daniels method and three‐dimensional diffusion with the Jander model. The mass influence was analyzed observing that good agreement is obtained working with sample weight in the order of 3–4 mg. Under such conditions the activation energies (Ea) were 16–17, 18–19, and 23–24 kcal/mole for the Borchardt‐Daniels, Kissinger‐Ozawa, and Jander

ISSN:0021-8995    

DOI:10.1002/app.1978.070220908

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

年代:1978

数据来源: WILEY

摘要:

AbstractA direct method for preparing deuterated ethylene by reducing acetylene‐d2with chromous ions in a dimethylformamide/deuterium oxide mixture is described. This method gives a good yield of precursor gas of relatively high purity. The gas was polymerized with a Ziegler‐type catalyst to produce deuterated polyethylene with sufficient purity and melt flow properties for use in laser fusion studies. A reaction variables study showed that polymerization of deuterated ethylene yields polymers with higher molecular weights than those obtained using normal ethylene. The study also indicated that the deuterium content of the polymer decreases with increasing reaction temperature, thus dictating that the process operates near room temperature. Several mechanical and chemical properties of the deuterated polymer were determined and are repor

ISSN:0021-8995    

DOI:10.1002/app.1978.070220909

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

年代:1978

数据来源: WILEY

摘要:

AbstractA series of epoxy adhesives were prepared from a commercial bisphenol A‐epichlorohydrin epoxy resin by diluting it with varying amounts of either phenyl glycidyl ether or 1,4‐butanediol diglycidyl ether and curing with either diethylenetriamine (DTA) or diethylaminopropylamine (DPA). The initial physical properties (density, viscosity, and surface tension) of the epoxy solutions were determined both with and without curing agents. It was found that the surface tensions of adhesives catalyzed with DPA are initially very low (31–32 dynes/cm), and within several hours these solutions attain an equilibrium surface tension of 40–46 dynes/cm. When the steel‐to‐steel lap shear strengths of these adhesives were measured, a correlation was not observed between the initial properties and the strengths of thes

ISSN:0021-8995    

DOI:10.1002/app.1978.070220910

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

年代:1978

数据来源: WILEY