摘要:

AbstractStructure is taken as the main theme in outlining the mechanical properties of polymer composites. Examples of two‐component polymer systems are selected from the literature showing their morphology, as evidenced from electron micrographs, and their corresponding mechanical properties, as evidenced by dynamic mechanical spectra. A compatibility number,Nc, is defined in a continuous scheme from a compatible system (one glass transition,Nc→ ∞) to an incompatible system (two glass transitions,Nc→ 0). The point at which semicompatibility occurs,Nc≅ 1, is taken as the approximate universal segmental length associated with a glass transition. This length of 150 Å allows for 100 to 5000 CC bonds for an associated glass transition. The ramifications of this molecular interpretation of a glass transition are discussed, resulting in a denouncement of the time–temperature correspondence principle and a new interpretation of short‐segmental

ISSN:0021-8995    

DOI:10.1002/app.1976.070201001

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

年代:1976

数据来源: WILEY

摘要:

AbstractA new catalyst system, based on a mixture of boron trifluoride–acetic acid complex (BF3·2CH3COOH) and magnesium chloride hexahydrate (MgCl2·6H2O), has been examined in cotton finishing treatment for producing easy‐care properties. It provides strong catalysis in crosslinking cotton with a series of N‐methylol finishing agents when the pad‐dry‐cure process is applied. Curing can be carried out at a temperature of 130–150°C for a period of 1–3 min, dependent on the temperature used. The resilience and abrasion resistance properties as well as the degree of polymerization (D.P.) of the crosslinked cotton so obtained were equivalent or slightly better than those of crosslinked cottons catalyzed by conventional catalysts. The influence of the new catalyst as well as a number of conventional catalysts, viz., ammonium chloride, ammonium dihydrogen phosphate, magnesium chloride hexahydrate, and zinc nitrate hexahydrate, on some properties of cotton fabrics was also investigated. The behavior of these catalysts in the presence of the N‐methylol finishing agent was quite different from their behavior in its absence. With the exception of ammonium salts, the D.P. of crosslinked cotton was much higher than that of cotton treated with the catalyst only. The opposite holds true for the a

ISSN:0021-8995    

DOI:10.1002/app.1976.070201002

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

年代:1976

数据来源: WILEY

摘要:

AbstractRates of sodium bisulfite‐initiated polymerization of methyl methacrylate in water were determined in absence and in presence of the metal oxides TiO2and Cu2O at 30°, 40°, 50°, and 60°C. Cuprous oxide and titanium dioxide enhanced the rate of polymerization and reduced the molecular weight as compared with the figures obtained in absence of oxide, the effect of the former being more pronounced than the latter. With TiO2, the rate was increased from 2.3 to 3.2 × 10−5, while with Cu2O, it was increased to 8.6 × 10−5mole/l./sec, both at concentrations of 9 g/l. water. The apparent energy of activation for the polymerization of methyl methacrylate between 40°C and 50°C was found to be 15.6 kcal/mole in absence of the metal oxides, and 7.6 kcal/mole and 2.8 kcal/mole in presence of titanium dioxide and cuprous oxide, respectively. The number‐average molecular weight was found to decrease slightly with the addition of TiO2but to decrease greatly when

ISSN:0021-8995    

DOI:10.1002/app.1976.070201003

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

年代:1976

数据来源: WILEY

摘要:

AbstractGlass‐like materials containing carbon were produced by heating plumbite‐treated cotton fabrics in a limited oxygen atmosphere while in contact with a surface having a high silica content. Although the new materials were changed to a clear glassy state, they retained the design and shape of the fabric weave and were hard, brittle, acid resistant, and alkali resistant. Surface smoothness of the new materials and release from the high silicon‐content materials on which they were made depended on lead content of the plumbite‐treated cotton fabric. High lead contents produced smoother surfaces and better release. This information was applied in producing glass‐like write‐on labels for laboratory glassware or individual flakes of the new material. Direct heat from a Bunsen‐type burner caused the new glass‐like materials to become metallic gold in color without altering other properties. Indirect heat reversed the color to the original. ESCA and x‐ray fluorescence examinations showed the atom ratio of lead to silicon to be 2.5:1 for those made from high lead‐content fabric. Substantial carbon was present

ISSN:0021-8995    

DOI:10.1002/app.1976.070201004

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

年代:1976

数据来源: WILEY

摘要:

AbstractSuzorite mica has been surface modified by microwave plasma treatment in ethylene gas. The surface‐treated mica was used as a filler in polyethylene, polystyrene, and a mixture of these two polymers. Significant changes in rheological behavior ensue. These indicate that adhesion between polyethylene and irradiated mica is superior to that of interfaces using unirradiated mica. In contrast, ethylene irradiation reduces the ability of filled polystyrene compounds to store elastic energy in melt flow, an effect consistent with impaired adhesion at interfaces involving these components. An intermediate situation exists in the case of the two‐polymer blend. The tensile properties of these systems also reflect surface treatment, reinforcement occurring in polyethylene‐containing compounds, while the tensile properties of polystyrene composites deteriorate. Plasma‐induced surface modifications of fillers to produce desired property changes in specified polymer matrixes are implied by the present work, but a fuller understanding of the chemistry of surface modification reactions is needed to substantiate these impli

ISSN:0021-8995    

DOI:10.1002/app.1976.070201005

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe complex relative premittivityK*(ω) of polymer–mica composites has been studied in the frequency range extending from about 10−2to 107Hz. Microwave plasma treatment in ethylene of the mica flakes leads to significant alterations ofK*(ω) for the matrix polymers used—polyethylene, polystyrene, and a mixture of these two polymers. The origins of the dispersion characteristics were investigated using a series of polyethylene samples containing up to 50 wt‐% of untreated mica. Comparing experimental results with theoretical analyses of the Maxwell‐Wagner‐Debye‐like interfacial polarization effect, it is possible to identify two major contributions toK*(ω): a Debye‐like dispersion centered near 102Hz and a charge‐diffusion mechanism which contributes primarily at low

ISSN:0021-8995    

DOI:10.1002/app.1976.070201006

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

年代:1976

数据来源: WILEY

摘要:

AbstractABS systems which differ distinctly in particle size and degree of grafting were prepared and investigated by dynamic mechanical measurements as function of temperature in the glass transition region of the rubber phase. Variation of rubber content within different sample series results in effects which were mainly referred to thermal stresses as consequence of phase interactions. Basic aspects of the deformation behavior of some of these ABS systems are studied by mechanical and morphological methods, and the operation modes of the component of a bimodal/bigraft‐system concerning toughness are discusse

ISSN:0021-8995    

DOI:10.1002/app.1976.070201007

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

年代:1976

数据来源: WILEY

摘要:

AbstractAn earlier model relating the variation of the steady‐shear melt viscosity of high‐density polyethylene to the molecular weight distribution is applied toward predicting the steady‐shear elastic compliance, the first normal stress difference, and relaxation spectrum as a function of shear rate from the molecular weight distribution. The model envisions the cutting off of longer relaxation times as the shear rate is raised such that at any shear rate${\rm \dot \gamma }$the molecular weights and their corresponding maximum relaxation times τmare partitioned into two classes; the relaxation times are partitioned into operative and inoperative states, depending on whether they are less than or greater than τc, the maximum relaxation time allowed at${\rm \dot \gamma }$. Equations relating molecular weight and relaxation time to the steady‐shear elastic compliance and viscosity are assumed valid at nonzero shear rates, except for the partitioning effect of shear rate. The shear rate dependence of the first normal stress difference and the steady‐shear viscosity for polyethylene melts is successfully predicted over the range covered by the cone‐and‐plate viscometer. The assumed proportionality constant between τcand 1/${\rm \dot \gamma }$was determined to be 1.7. Using this relation, the maximum relaxation time at 190°C for a polyethylene molecule of molecular weightMis given by τm= 1.4 × 10−19(M)3.33. Reasonable agreement has been obtained between the experimentally determined relaxation spectrum of a polyethylene melt and that predicted from the molecular weight distribution. The agreement is best at the lon

ISSN:0021-8995    

DOI:10.1002/app.1976.070201008

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

年代:1976

数据来源: WILEY

摘要:

AbstractSeveral nitrile rubber elastomers were polyblended, across the composition range, with selected polymeric compositions containing vinyl chloride. The compositions incorporated were (a) bulk poly(vinyl chloride) (PVC); (b) copolymers of vinyl stearate and vinyl chloride containing, respectively, 0.21, 0.36, and 0.47 weight fraction of the vinyl ester; and (c) mixtures containing the same weight fractions of di‐2‐ethylhexyl phthalate (DOP) with PVC. Mechanical, viscoelastic, optical, and volatility properties were studied on all blends in this first paper. To accurately compare the mechanical properties of polyblends of different systems, a criterion of mechanical equivalence was taken as the observance of similar stresses at break for compositions selected to have identical 100% moduli. Optimum mechanical equivalence, therefore, occurred at the largest ratios of 100% modulus to break stress for all systems compared. Optimum mechanical property equivalence was observed for NBR blends with PVC and for similar blends of both internally and externally plasticized systems containing 0.21 weight fraction of plasticizer. However, considerably more nitrile rubber was needed for PVC blends to acquire the properties of the plasticized systems. Mechanical equivalence was observed, but was not optimum for systems having more plasticizer because tensile strengths were lower. Polyblending with NBR improved the toughness and low‐temperature properties of starting vinyl stearate copolymers. Improved toughness was indicated by the expansion of areas under stress–strain curves. Refractive index matching appeared to explain the transparency of the best films and their relative freedom from haze. On heating at 85°C, poly(vinyl chloride) and the copolymer polyblends suffered no volatility loss. Volatility of DOP from the blends was 1.5 times greater than for PVC–DOP mixtures. Because modulus–temperature curves and mechanicalTgvalues of the filler component shifted with composition, the mechanical behavior of these blends was in harmony with an accepted standard of interdomain c

ISSN:0021-8995    

DOI:10.1002/app.1976.070201009

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

年代:1976

数据来源: WILEY

摘要:

AbstractIsochronal viscoelastic parameters were obtained for the polyblends of nitrile rubbers with internally and externally plasticized poly(vinyl chloride) (PVC) whose mechanical properties were studied in the previous paper. Thus, the room‐temperature mechanical properties of the previous paper were extended to included a wide temperature range in this work. Phase immiscibility, indicated by the observance of two glass transition temperatures, using differential scanning calorimetry, was observed for most of the polyblends. In contrast, blend compatibility was indicated by mechanical measurements, because the inflection temperatures of the isochronal curves (Ti) shifted with blend composition. It was concluded that mechanical spectroscopy‐monitored volume elements large enough to include contributions to viscoelastic response from both phases; this caused the curves to shift with composition. On the other hand, the much shorter‐range segmental responses characteristic ofTgproduced transitions at the discrete temperature intervals representative of each phase. Using a relation between torsional stiffness at room temperature and tensile strength, failure strengths with respect to temperature were estimated and compared at varied free‐volume increments (T − Tg) up to 50°C. Approximate equivalence was found by this procedure for fillers of bulk PVC and those containing 21 wt‐% of both internal and external plasticizer, in analogy with findings for mechanical property optimization of the previous paper. Low‐temperature properties and viscoelastic response of the polyblends containing vinyl stearate copolymers were greatly improved over their neat state. In addition, data from isochronal temperature–composition diagrams suggested viscoelastic equivalence, but greater ease of processability for the blends containing vinyl ester, compar

ISSN:0021-8995    

DOI:10.1002/app.1976.070201010

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

年代:1976

数据来源: WILEY