摘要:

AbstractA combined optical and electron microscopical study has been carried out of the crystallization habits of poly(vinylidene fluoride) (PVF2) when it is crystallized from blends with noncrystallizable poly(ethyl acrylate) (PEA). The PVF2/PEA weight ratios were 0.5/99.5,5/95, and 15/85. Isothermal crystallization upon cooling the blends from the single‐phase liquid region was carried out in the range 135–155°C, in which the polymer crystallizes in the α‐orthorhombic unit cell form. The 0.5/99.5 blend yielded multilayered and planar lamellar crystals. The lamellae formed at low undercoolings were lozenge shaped and bounded laterally by {110} faces. This habit is prototypical of the dendritic lateral habits exhibited by the crystals grown from the same blend at high undercoolings as well as by the constituent lamellae in the incipient spherulitic aggregates and banded spherulites that formed from the 5/95 and the 15/85 blends, respectively. In contrast with the planar crystals grown from the 0.5/99.5 blend, the formation of the aggregates grown from the 5/95 blend is governed by a conformationally complex motif of dendritic lamellar growth and proliferation. The development of these aggregates is characterized by the twisting of the orientation of lamellae about their preferentialb‐axis direction of growth, coupled with a fan‐like splaying or spreading of lamellae about that axis. The radial growth in the banded spherulites formed from the 15/85 blend is governed by a radially periodic repetition of a similar lamellar twisting/fan‐like spreading growth motif whose recurrence corresponds to the extinction band spacing. This motif differs in its fan‐like splaying component from banding due to just a helicoidal twisting of lamellae about the radial direction. © 1993 John

ISSN:0887-6266    

DOI:10.1002/polb.1993.090311001

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractGas sorption properties, permeability coefficients, and diffusion coefficients of a series of norbornene polymers are presented. Introduction of the Si(CH3)3group into the polynorbornene (PNB) backbone chain results in significant increases in glass transition temperature, permeability, and diffusion coefficient for a number of gases (H2, O2, N2, CO2, CH4, C2H6). The transport properties and sorption isotherms for poly(5‐trimethylsilyl norbornene) (PTMSNB) are very similar to those for poly(vinyltrimethyl silane) (PVTMS), which contains the same side‐chain group but differs from PTMSNB by the structure of its main chain. For another silicon‐containing polymer poly[5‐(1,1,3,3‐tetramethyl‐1,3‐disilabutyl) norbornene] (PDSNB) having a bulkier side‐chain group, the glass‐transition temperature is decreased in comparison with that of PNB, presumably owing to self‐plasticization. Both silicon‐containing norbornene polymers (PTMSNB and PDSNB) have permeability coefficients for “rapid” gases like H2or CO2of about 102Barrer. The high values of the Langmuir sorption capacity C′Hfor PTMSNB and PVTMS, as well as the high diffusivity and mobility of spin probes in these polymers, were attributed to a large free volume related to the bulky Si(CH3)3groups attached directly to the main chain.

ISSN:0887-6266    

DOI:10.1002/polb.1993.090311002

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe melting behavior of spherulites in thin sections of isotactic polypropylene bulk samples and high‐density polyethylene thin films crystallized isothermally at various temperatures has been studied by polarized light microscopy. The regions around cavities and multiple boundary points between spherulites have higher melting temperatures than the other parts of spherulites crystallized in Regime III. The increase in melting temperature is explained as a result of crystallization under negative pressure arising locally in pockets of occluded melt due to density change during spherulitic crystallization. The negative pressure lowers locally the equilibrium melting temperature and therefore decreases the undercooling, which results in an increase in lamellar thickness. Sectioning of bulk samples releases frozen negative pressure and reveals the increase in melting temperature of those parts of spherulites that were crystallized at lower undercooling. © 1993 John Wiley&Sons, I

ISSN:0887-6266    

DOI:10.1002/polb.1993.090311003

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe effects of ionene polymers (6,3‐ionene, 6,6‐ionene, 6,8‐ionene, and 6,12‐ionene) with various charge densities upon association constantsKfor the complexation between flavin mononucleotide and indoleacetate have been studied. Except for 6,12‐ionene,Kincreases with increasing polymer concentration then passes through a maximum, and declines at high polymer concentrations. The value of the maximumKincreases in the order 6,8‐ionene>6,3‐ionene>6,6‐ionene. In contrast, 6,12‐ionene gives only a monotone increasing curve with increasing polymer concentration. These curves are analyzed using the theory of the partition coefficient proposed in the previous paper. The types of the curves that the theory predicts are classified in greater detail than in the previous paper, and examples are given. © 1993 Jo

ISSN:0887-6266    

DOI:10.1002/polb.1993.090311004

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractMixtures of a phenoxy polymer (polyhydroxyether ofbis‐phenol A) and a polyolefin ionomer (sodium ionomer of ethylene methacrylic acid copolymer) were compatibilized by the addition of small amounts of sodium ethoxide and/or by the incorporation of varying amounts of A‐B‐A block oligomers. The latter were produced by reacting severalbis‐phenol A epoxy resins, varying in molecular weight, with montanic acid in order to provide segments soluble in each of the two polymer components of the blend. Chemical miscibilization by the addition of sodium ethoxide changed the morphology into one containing larger amounts of cocontinuous phases, while the incorporation of substantial amounts of A‐B‐A oligomer brought about primarily the formation of irregular and highly elongated particles. The mixtures were found to exhibit the typical properties of ionomers which were enhanced by the addition of sodium ethoxide. Furthermore sufficient evidence was gathered to establish that the ionomeric aggregates are shared by both polymer components of the blend, from which the term coionomeric mixture is derived. © 1993 John Wil

ISSN:0887-6266    

DOI:10.1002/polb.1993.090311005

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractBlends of polybutylene terephthalate and ethylene butyl acrylate copolymers were studied at two extreme concentration levels so that each polymer would form, in turn, a particulate dispersed phase. The blends contained 5% by weight of a coionomeric compatibilizer, which was produced from 1 : 1 mixtures of a polyhydroxy ether of bisphenol A and the sodium ionomer of an ethylene methacrylic acid copolymer, using sodium ethoxide to enhance the formation of ionomeric clusters together with an A‐B‐A block oligomer to assist the solubilization of the two ionomeric polymers. In all cases the addition of the coionomeric compatibilizer mixture to the blend was found to decrease the size of the dispersed particles with a concomitant reduction in the interphase gap. It was also observed that the dispersed polymer exhibited a lower level of crystallinity and a slightly lower melting point than when it was present as a matrix, particularly for the case of the ethylene butylacrylate copolymer. The inability of the compatibilizer to completely prevent the formation of an interfacial gap which did not allow the blends to achieve more substantial improvements in mechanical properties, was attributed to the vast difference in crystallization temperature between the two polymers. © 1993 John Wiley&Sons,

ISSN:0887-6266    

DOI:10.1002/polb.1993.090311006

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe perfectly alternating ethylene carbon monoxide copolymer (polyketone; POK) has been studied by means of1H nuclear magnetic resonance and thermal analysis, and the crystal structure, determined by wide angle x‐ray scattering methods, is presented. The crystal structure of this polymer in well‐oriented fibers (POK‐α) is as follows: Space group Pbnm, α = 6.91 (2) Aå,b= 5.12 (2) Aå,c= 7.60 (3) Aå (fiber axis),pc= 1383 kg/m3. This differs from the structure reported earlier by Chatani et al. (POK‐β). The very dense packing in the POK‐α structure is a result of the arrangement of the dipoles in the crystal lattice, giving rise to strong lateral forces between the polymer chains. Owing to the all‐transconformation of the polymer chain in the crystal lattice, high moduli can be achieved for well‐oriented fibers. A first approximation results in a value of 360 GPa for the theoretical modulus. From the melting data for a series of low molecular weight polyketone homologs, a first, estimate is derived for the crystalline heat of fusion (215–330 J/g) for infinite chain length. As a result of the strong lateral forces, this polymer shows a (very) high crystalline heat of fusion, whereas creep and compressive strength of oriented fibers are expected to be superior to those of high‐modulus polyethylene fibers. ©

ISSN:0887-6266    

DOI:10.1002/polb.1993.090311007

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractX‐ray scattering from a series of poly(ethylene terephthalate) (PET) fibers spun at differet speeds is analyzed to probe the morphology in the direction transverse to the fiber axis. Both the apparent crystal modulus, determined from the change in wide‐angle X‐ray scattering angle with fiber stretching, and the transverse degree of crystallinity indicate there is a substantial interfiberillar amorphous content. In the PET fiber spun at conventional speeds, only roughly one‐quarter of the fiber cross‐section is actually occupied by fibrils. The transverse crystallinity increases for fibers spun at speeds sufficient to cause crystallization in the spin line. The X‐ray moduli and fibril diameters are correspondingly larger in these high speed spun fibers. © 1993 John Wil

ISSN:0887-6266    

DOI:10.1002/polb.1993.090311008

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractTwo phenomenogical descriptions of oriented semicrystalline polymers, the series‐parallel model and the series‐aggregate model, were applied to poly(ethylene terephthalate) (PET) fibers obtained at different spinning speeds. The mechanical behavior of the fibers conformed well to both models. The analyses indicate that PET fibers obtained by high‐speed spinning possess a more compliant interfibrillar amorphous phase. This feature may account for both the greater dimensional stability, as well as the more reversible mechanical behavior, exhibited by high‐speed spun PET. © 1993 John Wiley&S

ISSN:0887-6266    

DOI:10.1002/polb.1993.090311009

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractBlends oft‐butylaminoethyl methacrylate grafted polyethylene (PE‐g‐tBAEMA) with methyl methacrylate‐methacrylic acid copolymer (PMMA‐MAA) and polymethyl methacrylate (PMMA) were prepared in a Banbury type batch mixer. The effects of component proportions and processing conditions on the melt flow index, morphology, impact, and tensile properties of the resulting polymer blends were investigated. The interfacial chemical reaction was studied using Fourier transform infrared (FTIR) technique. It was observed that the melt index of the blends was reduced with increasing melt processing temperature and mixing time, indicating the formation of PE‐g‐PMMA block copolymer. New IR bands at 1554, 1628, 1800, and 1019 cm−1were observed only for PE‐g‐tBAEMA/PMMA‐MAA, the reactive blends, but not for PE‐g‐tBAEMA/PMMA, the nonreactive blend. These IR bands were attributed to the amide, carboxylate anion and methacrylimide formation resulting from the chemical reaction between the secondary amine on the PE‐g‐tBAEMA/PMMA moiety and the carboxylic acid on PMMA‐MAA segment. The morphology of the blends in various compositions was examined using scanning electron microscopy (SEM) and related to their mechanical properties. All of the blends have a domain structure whose morphology is strongly dependent on the concentration of the dispersed phase. Furthermore, the PE‐g‐tBAEMA/PMMA‐MAA reactive blends were shown to have much finer morphology than the corresponding nonreactive blends. For the reactive polymer blends consisting of brittle particles dispersed in the ductile matrices, the PE‐g‐tBAEMA/PMMA‐MAA, impact and tensile result higher than predicted by the additivity rule were observed. The toughening of polyethylene by PMMA was explained by a “cold‐drawing” mechanism. The Young's modulus of the blends and the extent of interfacial adhesion were analyzed with Takayanagi and Sato

ISSN:0887-6266    

DOI:10.1002/polb.1993.090311010

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY