摘要:

AbstractThe molecular orientation of stretched polyethylene has been estimated separately for the crystalline and amorphous phases by using x‐ray and birefringence techniques. It is confirmed that if a hightly crosslinked polyethylene is highly stretched rapidly in the perfectly molten state and cooled to room temperature, a fibrous structure comprised of highly oriented crystallites and almost unoriented relaxed amorphous chains is produced. Some properties such as dynamic mechanical properties and thermodynamic property are discussed in relation to the molecular structur

ISSN:0021-8995    

DOI:10.1002/app.1966.070101001

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

年代:1966

数据来源: WILEY

摘要:

AbstractWhen effect of the substrate is nullified, resiliency can be defined as a function of strain, time, and humidity. Determination of improvement in the immediate, or rapid, tensile recovery readily delineates differences due to chemical modifications. Delayed recovery is usually less improved than immediate. Crosslinking cotton with dimethylolethyleneurea (DMEU) increases tensile strain recovery as the number of crosslinks increase, reduces dependency of recovery upon external strain, and produces maximum recovery at about 65% R.H. Noncrosslinking treatments produce limited increases in tensile strain recovery. Measurements on yarns crosslinked with DMEU and then hydrolyzed indicate that incalculably few residual links may contribute to tensile recovery.N‐Methylol‐N'‐methylethyleneurea treated cotton displays physical blocking and water swelling which aid recovery. Oleoyl chloride esterified cellulose has tensile recovery probably due to molecular entanglements. Its delayed or viscoelastic recovery is the most improved with immediate recovery being the least improved. The higher the moisture regain, the greater tensile modulus reduction under wet conditions. Crosslinking with DMEU under dry conditions lessens this reduction in modulus. Improvements in the tensile recovery of strain and energy, for all samples and with varied conditions of humidity and strain, correspond linearly with unit

ISSN:0021-8995    

DOI:10.1002/app.1966.070101002

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

年代:1966

数据来源: WILEY

摘要:

AbstractIsothermal crystallization of poly[3,3‐bis(chloromethyl)oxacyclobutane] and poly‐(ethylene terephthalate) from the quenched glassy state gave small lamellae approximately 1000–2000 A. in lateral dimension with a constant thickness of about 100 A. The maximum primary nuclei density for crystallization slightly above the glass transition temperature,Tg, was 1010greater than frequently observed during spherulitic growth from the melt. Since the lamellae grow at a linear rate, the crystallization process could be described by the Avrami theory for two‐dimensional growth with a constant nuclei density. By assuming that crystallization nearTgis diffusion‐controlled, bulk crystallization rate data were analyzed to obtain self‐diffusion coefficients whose activation energies were similar to reported values for oth

ISSN:0021-8995    

DOI:10.1002/app.1966.070101003

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

年代:1966

数据来源: WILEY

摘要:

AbstractThe crystallinity of a variety of poly(ethylene terephthalate) (PET) specimens, produced by thermal annealing, has been measured by three x‐ray diffractometric index methods and by an index method for differential scanning calorimetric data. The measurement procedures are termed indices since they involve various methods of ranking specimens in a relative manner between maximum and minimum crystallinity standards. Statistically different index values are determined by the various physical methods and procedures of calculation for many types of specimens. The integral index method, which utilizes x‐ray diffractometric data, corresponds in a more precise manner to the calorimetric index than to the other two x‐ray methods, for the cases in which oriented film is annealed in a vacuum oven and is subject to a continuous pumping environment. This treatment also produces a threefold increase in number‐average molecular weight of PET film. Annealing in sealed ampules,Mnconstant, produces substantially the same results for all three x‐ray methods but different results for the calorimetric procedure. A relatively simple two‐point procedure yields virtually the same trend as the more complicated indic

ISSN:0021-8995    

DOI:10.1002/app.1966.070101004

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

年代:1966

数据来源: WILEY

摘要:

AbstractSamples of α‐cellulose, containing 0.11–0.14% ash, were isothermally pyrolyzed in a fluidized bath in a nitrogen environment at 250–298°C. Results were reported in terms of volatilization (based on weight‐loss measurements) and decomposition (in term of glucosan loss). The findings show three distinct stages of pyrolysis: (1) an initial period of rapid decomposition and weight loss; (2) a range in which both the volatilization and decomposition are of zero order; (3) a region in which the volatilization follows a first‐order rate, leaving a char deposit which does not undergo further pyrolysis. The degree of decomposition and volatilization occurring during the zero‐order phase increases with increasing temperature. A single activation energy of 42 kcal./mole describes both the decomposition and volatilization rates in the zero‐order phase over the entire 2

ISSN:0021-8995    

DOI:10.1002/app.1966.070101005

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

年代:1966

数据来源: WILEY

摘要:

AbstractLength‐temperature measurements on a series of polymer blends over the whole range of composition from pure polyethylene to pure polypropylene and one set of determinations on a 50:50 copolymer and on polystyrene are evaluated. The total crystallinity of the samples did not exceed 54%. The experimental procedure utilized a linear variable differential transformer without the use of a confining fluid, and the temperature ranged from about +20 to –185°C. A least‐square numerical differentiation procedure based on moving arcs is applied to yield directly the coefficients of thermal expansion as a function of temperature. The linear voltage differential transformer (LVDT) technique can detect transitions in which the change in thermal expansion coefficients is less than 10−5°C.−1. In polypropylene as well as the blends, the principal glass transition is clearly seen in the range observed by others, namely at about –9 to –14°C. Its location varies only slightly with composition at polyethylene contents less than 88 mole‐%. For polyethylene the transition region broadens noticeably. The results are suggestive of two transitions for 0>T>–40°C. A second transition region is observed for either pure component around –126°C. Its location varies some what with composition. However, our results do not indicate the appearance of an additional transition region characteristic of the mixture. The copolymer exhibits a major transition at –61°C. in good agreement with earlier workers. The thermal expansion decreases again around –150°C. In general our observations concerning transitions belowTgare c

ISSN:0021-8995    

DOI:10.1002/app.1966.070101006

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

年代:1966

数据来源: WILEY

摘要:

AbstractEquilibrium pressure–volume–temperature behavior in both the solid and molten regions was determine for nylon 610. Data were measured with a compressibility device capable of obtaining precise and accurate data. Residual curve treatment showed that the data were true equilibrium data. A volume extrapolated to 2419 atm. at room temperature from the present data compared favorably to the sole literature value reported by Bridgman. The data of this work showed the existence of what appears to be a second‐order transition point for nylon 610. This point ranged from 140°C. at 232 atm. to about 170°C. at 1855 atm. The Spencer‐Gilmore equation was fitted to the data of t

ISSN:0021-8995    

DOI:10.1002/app.1966.070101007

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

年代:1966

数据来源: WILEY

摘要:

AbstractDielectric constant and loss of poly(vinyl alcohol) films of different stereoregularity and crystallinity are measured at frequencies from 30 cps to 3 Mcps in the temperature range from −50 to 25°C. The relaxation strength of local mode relaxation is higher for atactic and syndiotactic samples than for isotactic samples when compared at zero crystallinity. This behavior is reasonably explained in terms of interchain hydrogen bonds in the former and intrachain hydrogen bonds in the latter. Dielectric constant and loss of the crystal aggregate of atactic poly(vinyl alcohol) are measured at temperatures from −50 to 140°C. The relaxation strength of the crystalline relaxation is in good agreement with the theory in which the relaxation is attributed to torsional vibration of crystalline chains. The weak loss peak at low temperatures which almost agrees with the local mode relaxation of bulk samples in the frequency‐temperature position is ascribed to the surface disorder of single c

ISSN:0021-8995    

DOI:10.1002/app.1966.070101008

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

年代:1966

数据来源: WILEY

摘要:

AbstractAs one in a series of studies relating the rheological behavior of mechanical mixtures of two polymer components to the degree of mixing, the tensile stress relaxation behavior of a graft copolymer of poly(vinyl acetate) with styrene, obtained by60Co γ‐irradiation of poly(vinyl acetate) in styrene solution and extraction of homopolymers, was investigated as a function of the fraction of styrene component and compared with that of a mechanical mixture of poly(vinyl acetate) with polystyrene, one of the typical combinations of incompatible components. The results obtained may classify the graft copolymer as a sort of mechanical mixture giving stable mixing even for incompatible componen

ISSN:0021-8995    

DOI:10.1002/app.1966.070101009

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

年代:1966

数据来源: WILEY

摘要:

AbstractCastings having unexpectedly high heat‐distortion temperatures result when certain treated resins of the EPONEPON is a registered trademark of the Shell Oil Company.828 type and about 75% of the stoichiometric amount ofm‐phenylenediamine, are postcured for 10–20 hr. at 175–200°C. The improvement in heat‐distortion temperature is about 100°C., to values as high as 250°C. A recrystallized resin has given the highest values. Other glycidyl ethers of polyphenols have shown this phenomenon to a lesser degree, but other amine curing agents, including isomers and substitution products ofm‐phenylenediamine, have not. Some evidence of a new curing reaction has been developed, by NMR and pyrolysis studies of model compounds, which supports the postulate that them‐phenylenediamine is alkylated with a fifth epoxy group during the postcure, presumably at a ring carbon, resulting in grea

ISSN:0021-8995    

DOI:10.1002/app.1966.070101010

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

年代:1966

数据来源: WILEY