摘要:

AbstractExtrusion rates have been measured for high density polyethylene fibers prepared by solid‐state extrusion through a conical die with maximum draw ratio of 52, using constant pressure and temperatures ranging from 0.12 to 0.49 GPa and 60° to 140°C and molecular weights from 5 × 104to 6 × 106. The processing variables are reported in terms of an apparent elongational viscosity. The logarithm of the extrusion rate was proportional to the applied pressure. Deviation from the Eyring theory of viscosity was found, since lowering of the extrusion temperature to 60°C produced an anomalous decrease in the extrusion rates. The anomaly was explained by the increased friction between die and polymer, the pressure dependence of the yield stress, and by the pressure dependence of the α‐relaxation mechanism. Apparent activation energies of 60 and 100 kcal/mole were calculated for the solid‐state extrusion in the region 100°–130°C and 80–100°C. Three modes of deformation were observed for each extrusion, consisting of an unsteady state, a second stage of drawing in which the extrusion rate approached a constant value, and a fracture region. The first mode corresponded to orientation and rotation of the crystalline lamellae, as shown by the rapid increase and plateau region of the crystalline and noncrystalline orientation functions. During the second stage of deformation, the apparent elongational viscosity ηEincreased linearly with draw ratio, as did the modulus, and this mode was found necessary for the attainment of high modulus fibers. The second mode of deformation was associated with the deformation of the crystalline lamellae and strain hardening in which ηE‐approached that for a glass. Strain hardening readily occurred with decreasing temperature, and increasing draw ratio and molecular weight. Continuous extrusion producing uniform modulus fibers was only possible when the maximum draw ratio of the die was less than the fiber draw ratio, where strain hardening occurred. The third mode of deformation limited the maximum modulus obtainable and consisted of fracture or kink planes oblique to the fiber axis. The relations between the processing variables used in the solid‐state extrusion and the resulting fiber

ISSN:0360-8905    

DOI:10.1002/polc.5070630125

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

年代:1978

数据来源: WILEY

摘要:

AbstractBlends may be made of pairs of polymers where neither, one, or both components are crystalline. The state of compatibility for such blends may be deduced by x‐ray and light scattering. A survey of recent studies in this laboratory of several binary blends of crystalline and amorphous polymers is presente

ISSN:0360-8905    

DOI:10.1002/polc.5070630126

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

年代:1978

数据来源: WILEY

摘要:

AbstractHead‐to‐head poly(vinyl cyclohexane) (H‐H PVCH) was prepared from 2,3‐diphenylbutadiene, which was polymerized by radical, 1,4 polymerization to poly(2,3‐diphenylbutadiene) and then catalytically hydrogenated to H‐H PVCH, H‐H PVCH was also prepared by catalytic hydrogenation of H‐H polystyrene (PS). The catalytic hydrogenations were carried out at an initial hydrogen pressure of 2000 psi and a temperature of 200°C. Some chemical, physical, and thermal properties of H‐H PVCH were investigated and compared with the properties of atactic and isotactic head‐to‐tail (H‐T) PVCH. The glass transition temperature of the H‐H polymer was found to be 50°C lower than that of the atactic H‐T polymer which indicates that the backbone chain has more flexibility. Both H‐H and H‐T PVCH showed comparable thermal stability. The temperature of the maximum rate of thermal degradation by differential thermogravimetric analysis was approximately 40°C higher than that

ISSN:0360-8905    

DOI:10.1002/polc.5070630127

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe effects of reaction parameters including copolyester composition, catalyst type and amount, temperature, time, endgroup concentration (molecular weight), and degree of crystallinity were determined for the reorganization of random to block poly(ethylene terephthalate‐co‐succinate). The crystallization‐induced reactions, which were the basis of these ordering processes, were carried out at temperatures at or below the terephethalate unit melting points of the initial copolyester. All samples so treated showed increased melting points, recrystallization temperatures, and degrees of crystallinity which correlated with increased blockiness of the terephthalate units, as determined by nuclear magnetic resonance spectroscopy. At reaction temperatures greater than 15°C below the initial copolyester melting point, those parameters which controlled the rate of the ester interchange reaction also controlled the extent of the reorganization. Within approximately 15°C of the melting point, the reaction rate was apparently less important than physical factors related to the crystalline properties of the initial copo

ISSN:0360-8905    

DOI:10.1002/polc.5070630128

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe nucleation and growth behavior of a poly(1‐butene) melt has been measured as a function of undercooling and shear rate. Experiments were conducted using a parallel‐plate rotary shearing device with polarized light microscopy as the measuring technique. An exponential increase of nuclei with time at constant undercooling and shear rate was found. Growth rates of the crystalline bodies showed no significant change in a shear field. Nucleation and growth rate data were analyzed using expressions of the formI=I0exp [‐ΔE/RT ‐UTm/TΔT]G=G0exp [‐ΔE/RT ‐ UTm/TΔT] where ΔTis the undercooling,Tmis the equilibrium melting temperature, andUcontains lateral s̀ and end‐surface s̀efree energies. The value of s̀s̀ecalculated fromUfor crystallization under shear differed from that calculated for the quiescent case by a factor of two. This difference is tentatively explained in terms of an entropy loss

ISSN:0360-8905    

DOI:10.1002/polc.5070630129

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

年代:1978

数据来源: WILEY

ISSN:0360-8905    

DOI:10.1002/polc.5070630104

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

年代:1978

数据来源: WILEY