摘要:

AbstractThe steady‐state and dynamic melt rheology for a series of poly(1‐olefins) has been investigated. The series includes poly(1‐butene), poly(1‐hexene), poly(1‐heptene), poly(1‐octene), Poly(1‐undecene), poly(1‐tridecene), poly(1‐hexadecene), and poly(1‐octadecene). The flow behavior was investigated by use of a Weissenberg rheogoniometer. Measurements on poly(1‐butene) were also made using an Instron capillary rheometer. The empirical relationship developed by Cox and Merz was obeyed for the entire series of poly(1‐olefins) at all temperatures investigated. Graessley's theory was used to calculate the flow curves for the poly(1‐olefins) from the measured molecular weight distributions. The purpose was to investigate the effect of polymer composition on the shear rate dependence of viscosity. It was found that all experimental flow curves except those for poly(1‐hexene) can be fitted with the calculated curves from the individual molecular weight distributions. The conclusion is made that flow curves of poly(1‐olefins) depend predominately on molecular weight distribution and are essentially independent of side‐chain length even for poly(1‐olefins) with pendant groups as long as 16 carbon atoms. The low‐shear limiting Newtonian viscosity η0for all poly(1‐olefins) was expressed by, η0=KM̄ w3.4or by η0=K′P̄ w3.4where M̄wis the weight‐average molecular weight and P̄wis the weight‐average degree of polymerization. The K and K′ values obtaine

ISSN:0098-1273    

DOI:10.1002/pol.1978.180161001

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractSolid‐state extrusion of high‐density polyethylene (HDPE) has received considerable attention. It has been shown that extrudate may have high values of optical clarity, tensile modulus (∼70 GPa = 7 × 1011dyn/cm2), andc‐axis orientation. The effects of extrusion conditions on the properties of the resultant fibers have, however, not yet been clarified. A systematic study has thus been made here to evaluate extrusion pressure, temperature, and extrusion (draw) ratio, and the molecular weight of extruded HDPE. The effects of extrusion ratio on the degree of crystallinity, melting behavior, crystal orientation, and dimensional change along the extrusion direction are

ISSN:0098-1273    

DOI:10.1002/pol.1978.180161002

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThe tensile properties have been evaluated for high‐density solid‐state polyethylene extruded to different extrusion (draw) ratios. The results are compared with measured and theoretical values on this and other polymers. An extrusion (draw) ratio and a deformation gradient are defined and discussed. The content of extended tie molecules in extruded high‐density polyethylene was calculated from a model and modulus

ISSN:0098-1273    

DOI:10.1002/pol.1978.180161003

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThe effects of pressure on the α (ca. 70°C, 1 kHz) and γ (ca. −100°C, 1 kHz) relaxations of linear polyethylene were studied dielectrically between 0 and 4 kbar. Equation of state (PVT) data were also determined in the range of interest of these relaxations. The sample was rendered dielectrically active through oxidation (0.8 C0 per 1000 CH2). The α process (which occurs in the crystalline fraction) could be studied over a much wider temperature range than heretofore possible due to the effect of pressure in increasing the melting point. Examination of relaxation strength from 50 to 150°C showed that there must be two crystalline relaxation processes: the well‐known α relaxation plus a competing one. The α relaxation is believed to be due to a chain twist–rotation–translation mechanism that results in rotation–translation of an entire chain in the crystal. The relaxation strength of the α process decreases and therefore indicates the presence of a second (faster and not directly observed) process that increases in intensity with increasing temperature. It is postulated that the second process is due to motion of defects that become more numerous through thermal injection at higher temperatures. Analysis of the relaxation data along with the PVT data allowed the constant volume activation energy for the α relaxation to be determined. It was found to be 19.4 ± 0.5 kcal/mole. The constant volume activation energy is important in modeling calculations of the crystal motions and is significantly smaller than the atmospheric constant pressure activation energy of 24.9 kcal/mole. The effect of pressure on the activation parameters and shape of the γ process was also determined. There has been controversy over whether the γ process occurs only in the amorphous fraction or in both the amorphous and crystalline phases. Since the two phases have quite different compressibilities, increasing the pressure should change the shape of the loss curves (versus frequency and temperature) if the process occurs in both phases. The shape (but not location) of the loss curves was found to be remarkably independent of pressure. This finding strengthens the view that the γ process is ent

ISSN:0098-1273    

DOI:10.1002/pol.1978.180161004

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThe dielectric absorption due to the side‐group rotation of the methyl methacrylate (MMA) unit in MMA‐styrene and MMA‐p‐chlorostyrene (pCS) copolymers was measured. The relaxation time for MMA‐pCS copolymers with low MMA contents could be interpreted quantitatively in terms of the Kramers rate‐constant theory at the low‐friction limit. On the other hand, the frictional effect on the relaxation time could not be ignored for any copolymers except for the MMA‐pCS copolymers with low MMA contents. The relaxation time for pure poly(methyl methacrylate) could be interpreted by the Kramers theory at the high

ISSN:0098-1273    

DOI:10.1002/pol.1978.180161005

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThree loss peaks in the dielectric spectra of thermally oxidized polyethylene at temperatures below 50°K are each apparently associated with specific species of nonvolatile oxidation products involving hydrogen atoms. We report how each is influenced by room‐temperature rolling, heat treatment, isotopic substitution, and chemical attack. One, the Vincett‐Phillips peak, is susceptible to attack by Cu2+, Fe3+, and HI, and is attributed to a hydroperoxide species. Its rapid and easy determination has promise in the study of polyethylene oxidation. Carson's (higher‐frequency) peak is tentatively attributed to an alcohol species and a new (lower‐frequency higher‐temperature) peak is described but not yet attributed. A few additional observations are made on the loss peaks associated with antioxidants of the substituted phenol type, as reported by Thoma

ISSN:0098-1273    

DOI:10.1002/pol.1978.180161006

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractHigh‐speed gel‐permeation chromatography (GPC) of water‐soluble polymers has been investigated by using TSK‐GEL, type‐PW columns packed with small porous particles. Being semirigid, the column packing could be operated under high pressure and, therefore, it was possible to achieve high‐speed GPC. A resolution higher than that of ordinary GPC in organic solvent system was attained when the measurement of one sample was completed within 40 min with a 6‐ft column set. Samples with a wide range of molecular weights, from oligomers to polymers having a molecular weight greater than 106, could be fractionated. Dextran, polyethylene glycol, polyacrylamide, poly(vinyl alcohol), and poly(vinyl pyrrolidone) were separated according to molecular size with no evidence of adsorption. Investigation of other water soluble polymers is no

ISSN:0098-1273    

DOI:10.1002/pol.1978.180161007

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractOptical and ESR spectra of polymer‐Cu(II) complexes in polymer films have been studied. The dependence onF1= [Cu2+]/[MU] andF2= [OH−]/[Cu2+], where [MU] is the molar concentration of monomeric units of the polymer, has been obtained. Optical spectra and potentiometric titration curves in solution have also been studied. There exists a buffer region 0 ≲F2≲ 2. Optical spectra in films are slightly different from those in solutions. At least five different ESR signals, designated asA,B,CorD, andE, have been found in poly(vinyl alcohol)‐Cu(II). These signals appear successively with increasingF2. Assignments are proposed as follows. SignalA(F2≈ 0), also found in poly(acrylamide)‐Cu(II) and poly(vinyl pyrrolidone)‐Cu(II), is due to a single Cu(II) coordinated with two water molecules and chelated with two oxygens or nitrogens attached to the polymer. A chain of Cu(II) ions singly and double bridged with OH−ions is responsible for theBsignal (F2≈ 1). TheCandDsignals (F2≈ 2) appear to be caused, respectively, by a dimeric Cu(II) complex singly or doubly bridged with OH−ions. TheEsignal (F2≈ 7) appears to be due to a monomeric Cu(II) complex, different from that r

ISSN:0098-1273    

DOI:10.1002/pol.1978.180161008

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractGelation and melting of aqueous gelatin were investigated by differential scanning calorimetry. This phenomenon can be analyzed as a conventional crystallization process assuming predetermined primary nucleation and unidirectional growth. The results were interpreted in terms of the fringed micelle model. Calculated values of the diameter of the renatured collagen fibril were found in excellent agreement with those determined previously by electron microscopy.

ISSN:0098-1273    

DOI:10.1002/pol.1978.180161009

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractSamples of low‐molecular‐weight polystyrene (PS) in poly(methyl methacrylate) (PMMA) were prepared by first dissolving PS in methyl methacrylate monomer and then polymerizing the monomer. Forty‐three specimens of varying number‐average molecular weight (2100–49,000) and composition (5–40 wt %) of PS were prepared, and the surface morphology and phase relationships studied by scanning electron microscopy. Four distinct types of phase relationships were observed: (i) a single phase consisting of PS dissolved in PMMA; (ii) PS dispersed in PMMA; (iii) PMMA dispersed in PS; and (iv) regions of PS dispersed in PMMA coexisting with regions of PMMA dispersed in PS. Values of the size and population density of the dispersed particles are reported. Finally, the size and distribution of the dispersed particles and the various types of phase relationships are discussed in terms of the ternary polystyrene/poly(methyl methacrylate)/methyl methacrylate ph

ISSN:0098-1273    

DOI:10.1002/pol.1978.180161010

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY