ISSN:0360-8905    

DOI:10.1002/polc.5070710103

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

年代:1984

数据来源: WILEY

ISSN:0360-8905    

DOI:10.1002/polc.5070710104

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

年代:1984

数据来源: WILEY

摘要:

AbstractThis article presents a systematic investigation into the influence of dose rate on the results of irradiation of Nylon‐6 in ai

ISSN:0360-8905    

DOI:10.1002/polc.5070710105

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe thermodynamic properties of isotactic polypropylene in the fully crystalline, glassy, and molten state are established from 0 to 500 K based on data bank heat capacities and the vibrational frequency spectrum. The seven skeletal vibrations are described by θ3and θ1of 91 and 714 K for crystalline polypropylene. For the calculation ofCp− Cv, a LindemannA0value of 1.5 × 10−3K mol/J was found. Calculated and experimental heat capacity data show agreement within an average error of −0.3 ± 1.6%. Glassy polypropylene was similarly treated up to the glass transition temperature at 260 K (θ3= 78 K, θ1= 633 K, average heat capacity error −0.6 ± 2.8%). The residual 0 K entropy of glassy polypropylene is 1.9 J/K mol. Partially crystalline polypropylene is shown through high‐sensitivity DSC measurements to have a glass transition range from 260 to 380 K. Similarly, high‐sensitivity DSC has been used to characterize the condis phase of polypropylene (conformationally disordered polypropylene) which was prior called “smectic mesophase” or “paracrystalline.” Its heat of transformation to the stable

ISSN:0360-8905    

DOI:10.1002/polc.5070710106

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

年代:1984

数据来源: WILEY

摘要:

AbstractA series of particulate anionic PSs havingM̄nvalues from 1900 to 350,000 has been observed visually on a hot‐stage microscope at heating rates from 0.2 to 10 K/min. The temperature range over which the particles sinter, coalesce, and flow onto the glass slide is relatively narrow and reproducible. The temperature corresponding to a specific optical appearance is designatedTf(for flow temperature) and appears to represent an isoviscous state. It decreases asM̄n−1belowMc, and increases asM̄n(or possiblyM̄waboveMc, whereMcis the entanglement molecular weightTfvalues at 10 K/min are only slightly belowTIItemperatures observed by DSC and by torsional braid analysis. A plot of log heating rate versusTf−1with only five points forM̄n= 17,100 is clearly non‐Arrhenius and appears to follow a Vogel or WLF‐type equation.Tfis greater than and distinct fromTgat all heating rates except asM̄nbecomes less than about 2000 where the two processes tend to merge.Tfis independent of the several substrates tested: glass, Mylar, carbon, mica, Al, Al2O3, and PS. Globule formation which occurs just belowTfis probably a surface tension phenomenon. Its temperature,Tg1, decreases asM̄n−2/3atM̄n>Mc. It appears to represent aniso‐surface tension state. Origins of the endothermic peak observed by DSC on powder on first heating and the endothermic slope change found with melted films on subsequent heatings are proposed. Observations ofTg1andTfwere made on poly(p‐methylstyrene) and poly(p‐tert‐butylstyrene) but

ISSN:0360-8905    

DOI:10.1002/polc.5070710107

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe heat capacity of a narrow molecular weight distribution polystyrene, National Bureau of Standards—Standard Reference Material 1478, has been determined by a fully automated adiabatic calorimeter from 5 to 380 K for the sample subjected to different thermal history. The number‐average molecular weight of this sample is 35,800 and the dispersity in the molecular weights,Mw:Mn, is 1.045. The heat capacities of the glass and of the liquid of this material are found to be within 0.5% of other atactic polystyrenes over most of the temperature range studied. The glass transition temperatureTgof the annealed glass (cooling rate<1 K/h) at 366 K and that of the quenched glass (cooling rate about 6 K/min) at 366 K are determined by the intersections of enthalpy‐temperature curves of the glasses with the liquid. The glass transition temperature is slightly higher than that calculated from dilatometrically determinedTgs of a series of low‐polydispersity polystyrenes cooled at 0.1 K/h, but is lower than that from thermal analytically determ

ISSN:0360-8905    

DOI:10.1002/polc.5070710108

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

年代:1984

数据来源: WILEY

摘要:

AbstractThis article describes work with model polymers to explore the effects of long branches on polyethylene melt rheology. Dynamic moduli were measured at two or more temperatures on melts, blends, and solutions of linear (L) and star (B) hydrogenated polybutadiene (HPB). Enhancement factor Γ and temperature coefficient (flow activation energyEa) were determined from viscosity data and correlated with arm molecular weightMband volume fraction of the star component Φ. As in other species, Γ for a given branch point functionality is roughly an exponential function of Φ11/6Mbin entangled melts and solutions. In contrast with other species, however, (Ea)Band (Ea)Lare different; (Ea)B– (Ea)Lis directly proportional to ΦMb, and the degree of thermorheological complexity varies primarily with (Ea)B– (Ea)L. In blends with linear HPB of comparable viscosity, Γ for the star component remains essentially constant, and (Ea)B– (Ea)Lis directly proportional to the volume fraction of the sta

ISSN:0360-8905    

DOI:10.1002/polc.5070710109

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

年代:1984

数据来源: WILEY

摘要:

AbstractLight‐scattering and viscosity measurements are reported for fractions of poly(decamethylene perfluorosebacate). Intrinsic viscosity (dL/g) relationships at 25°C are [η] = 1.55 × 10−4Mv0.70in chloroform and (η) = 8.8 × 10−4Mv0.50ins‐tetrachloroethane. From these data the characteristic ratio is found to beCθ= 6.3 ± 0.5, indicating that the perfluoroalkane chain is not much more extended than an alkane chain. The solid semicrystalline polymer melts at 45°C, and its x‐ray powder pattern suggests a structure different from that of poly(decame

ISSN:0360-8905    

DOI:10.1002/polc.5070710110

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

年代:1984

数据来源: WILEY

摘要:

AbstractViscosities of mixtures of poly(vinyl alcohol) and Na smectite in water were measured at several pressures by using Couette and falling‐body‐type viscometers. The values of viscosity of clay‐polymer mixtures were found to bear an exponential relationship to the concentration of the polymer. The viscosities of these mixtures could be related to the concentration of clay by Arrhenius law at low concentrations or by Weltmann and Green's equation at high concentrations. The viscosities of polymer, clay, and clay–polymer mixtures increase exponentially with p

ISSN:0360-8905    

DOI:10.1002/polc.5070710111

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe adsorption of poly(vinyl butyral) (PVB) at the γ‐Fe2O3–benzene interface and the air–water interface was investigated by means of the adsorbance on γ‐Fe2O3and surface pressure (π)–area (A) curves. The adsorption isotherms of PVB on γ‐Fe2O3from the various solvents are of the Langmuir type and can be explained by competitive adsorption between PVB and the solvents. From the π–Acurves of monolayers and the adsorbance on γ‐Fe2O3, it was confirmed that the adsorbed PVB on γ‐Fe2O3is in a train‐loop conformation with the hydroxyl groups and the butyral segments directed toward the solution phase. The packing density of γ‐Fe2O3, particles in the magnetic coatings preferentially depends on the conformation of polymers on the particle surface. The PVB–solvent system which gives the most compact train‐loop conformation gives the highest dispersion and packing o

ISSN:0360-8905    

DOI:10.1002/polc.5070710112

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

年代:1984

数据来源: WILEY