摘要:

AbstractModification of nylon 6 by blending with a small amount of a novolac resin has been investigated. Unexpected increased ofTgand tensile modulus and reduction in moisture absorption have been found at levels of novolac incorporation of 1–3 wt %. The small amount of novolac resin also has an effect on the crystallization and nylon 6 crystal structure (α vs. γ form). © 1993 John Wiley&Sons,

ISSN:0021-8995    

DOI:10.1002/app.1993.070480401

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

年代:1993

数据来源: WILEY

摘要:

AbstractAn attempt has been made to graft copolymerize 4‐vinyl pyridine onto isotactic polypropylene hydroperoxide by mutual irradiation method in an aqueous medium. Polypropylene hydroperoxide has been prepared by irradiating recrystallized polypropylene beads from a Co60source in the presence of air. The resulting polypropylene hydroperoxide beads have been used as the backbone polymer and grafting of 4‐vinyl pyridine has been studied as a function of various reaction parameters. Optimum conditions for maximum percentage of grafting have been evaluated. Rate of grafting (Rg) has been determined as a function of preirradiation dose and initial monomer concentration. Water has been found to affect percentage of grafting. The graft copolymers have been characterized by spectroscopic method and isolation of the grafted poly(4‐VP) from the graft copolymer. A plausible mechanism is proposed to explain the mutual grafting of 4‐vinyl pyridine onto polypropylene hydroperoxide. © 1993 John Wiley&S

ISSN:0021-8995    

DOI:10.1002/app.1993.070480402

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

年代:1993

数据来源: WILEY

摘要:

AbstractTo clarify the relationship between crosslinking density and physical properties of phenol–formaldehyde novolac cured epxy resin and factors governing their physical properties, we studied various properties of cured resins having different crosslinking densities. The resins were prepared with various curing accelerators and raw epoxy resins having different molecular weights. We found that as the crosslinking density of a cured resin increases, glass transition temperature (Tg) rises and the relaxation time becomes longer. Furthermore, in the rubbery region, the coefficient of linear thermal expansion drops and the elastic modulus become larger, while, in the glassy region, the coefficient of linear thermal expansion, specific volume, water absorption, diffusion coefficient, and permeability all increase but the elastic modulus becomes smaller. The WLF analysis on the relaxation behaviors of typical cured resin showed that cured resin with a higher crosslinking density decreases in the fractional free volume. This behavior is completely opposite from the relationship predicted from the temperature dependency of specific volume. While the coefficient of thermal expansion of free volume decreases as the crosslinking density increases for the cured resin, it coincides well with the tendency predicted from the difference in coefficient of cubic thermal expansion in the rubbery and glassy regions of each cured resin. That the free volume obtained from WLF analysis shows a relationship opposite to the predicted free volume as based on the temperature dependency of specific volume is explained as follows: Namely, the free volume obtained from the WLF analysis is a hole free volumeVhwhich contributes to fluidity andVhdecreases with the crosslinking density. On the other hand, the free volume predicted from the specific volume is a sum of the interstitial free volumeViandVh.Viincreases with the crosslinking density and thisViincrease exceeds the decrease ofVh. Therefore, the free volume predicted from the specific volume increases with the crosslinking density. Consequently, the influence of free volume on the relationship between the crosslinking density and physical properties of cured resin can be interpreted as follows. As the crosslinking density increases on cured resins,Tgrises, the relaxation time is lengthened, and the coefficient of linear thermal expansion becomes smaller in the rubbery region because, as the crosslinking density increases,Vhdecreases. Since crosslinking density increases on cured resins, the coefficient of linear thermal expansion, water absorption, diffusion coefficient, and permeability become larger, and the elastic modulus becomes smaller in the glassy region because, as the crosslinking density increases,Viincreases and, accordingly, molecular chain packing becomes looser; i.e., the specific volume increases. © 1993 John Wiley&Sons, I

ISSN:0021-8995    

DOI:10.1002/app.1993.070480403

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

年代:1993

数据来源: WILEY

摘要:

AbstractA composite sandwich structure, consisting of a paper sheet as a middle layer and two porous coating layers of a highly filled acrylate–styrene–butadiene copolymer, has been studied by means of a dynamic mechanical test in torsion. Stiffness and mechanical damping, tan δ, were recorded over the temperature region where the latex polymer exhibits a glass transition. The mechanical damping decreases with increasing filler content in the coating. Variations in the thickness of the coating layers did not influence the mechanical damping. The glass transition temperature of the latex polymer increases with increasing volume fraction of filler at high filler contents as an effect of filler–matrix interaction. The outer layers partly penetrate into the middle layer, as indicated by thickness measurements on the coated paper. A theoretical comparison of the peak heights of the mechanical damping using lamination theory shows a discrepancy in the experimental results. If penetration of the outer layer is allowed for, i.e., if using a thicker outer layer of the composite in the calculations, a favorable correlation between the theoretical and the experimental results is obtained. © 1993 John Wiley&So

ISSN:0021-8995    

DOI:10.1002/app.1993.070480404

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

年代:1993

数据来源: WILEY

摘要:

AbstractA compatibilization strategy for poly(ethylene terephthalate) (PET) and polyethylene (PE) blends to achieve high toughness is described. Maleic anhydride functionalized styrene–ethylene–butylene–styrene (MA‐g‐SEBS) block copolymer at 20 pph was found to produce an intricate multidomain morphology in which the two major components (50% PE, 50% PET) and the compatibilizer coexist on a hierarchal order. A portion of the PET was dispersed as interconnected rodlike domains oriented along the injection direction. The rest of the PET and the PE constituted beadlike nano domains which served as the matrix. The blend at all these morphological levels responded to deformation in a cooperative fashion giving rise to a super tough material. That is, a blend whose elongation at break (600%) was superior to its two major components (90% for PET and 300% for PE). © 1993 John Wiley

ISSN:0021-8995    

DOI:10.1002/app.1993.070480405

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

年代:1993

数据来源: WILEY

摘要:

AbstractThree hydrolyzed‐starch–polyacrylonitrile (HSPAN) copolymer materials tested as gel–water dispersions in a Brookfield rotating spindle viscometer exhibited velocity slip at solid boundaries and a yield stress. Dispersions with 0.5% HSPAN concentrations were about 20,000 times more viscous than water when the shear stress surpassed the yield stress and viscous power‐law flow ensued. The apparent viscosity of an HSPAN gel–water dispersion was reduced by nearly an order of magnitude when tap water was substituted for deionized water. The apparent viscosity of the HSPAN gel–water dispersions decreased by about 30% after the fluid was continuously maintained at a temperature of 80°C for 1 week, and by an order of magnitude or more after 3 weeks under those conditions. In natural convection tests, the yield stress enabled an HSPAN gel–water dispersion to withstand greater temperature differences across a horizontal layer before inception of natural convection than a fluid without one. © 1993 John

ISSN:0021-8995    

DOI:10.1002/app.1993.070480406

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

年代:1993

数据来源: WILEY

摘要:

AbstractA theoretical analysis has been carried out of the structure of metalliferous epoxy–chelate polymers (MECP) based on diglycidyl ether of bisphenol‐A (DGEBA) hardened with metal complexes of the formula [M(L)n(X)p], whereMis the cation of the transition metal;R, a nitrogen‐containing ligand;X, the anion of an organic acid;n, the number of the ligands in the complex molecule (n= 1 or 2), andp, the metal valency (p= 2 or 3). On the basis of the correlations between the tensile strength (σt) and tensile modulus (Et), and flexural strength (σf) and flexural modulus (Ef), of MECP, σt=f(Et)and σf=f(Ef), and supposing that when the condition\documentclass{article}\pagestyle{empty}\begin{document}$ \sigma _{_{t_A } }= \sigma _{_{t_B } } ,{\rm}\sigma _{_{f_A } }= \sigma _{f_B } ,{\rm}E_{t_A }= E_{t_B } ,{\rm}E_{f_A }= E_{f_B } $\end{document}is fulfilled, whereAandBare complex hardeners of different structures but of the same class, the epoxy–chelate matrices have similar structures. The influence of the structural fragments of the hardener molecule (the metal, ligand, and anion) on the polymer properties was evaluated and it was found out that the biggest contribution to these properties belongs to the metal, the alteration of which changes the thermal stability (ΔMis the polymer mass loss after thermal treatment in air), deformability (ε), σf,Ef, and deflection temperature (DT) significantly. By this, the effect of the hardener structure change on the alteration of the MECP properties is maximal for ΔM, is minimal for the compressive strength (σc), and decreases in the series: ΔM>ε>DT>σf>Ef>σc. The type of the anion affects σcsignificantly, but the ligand type contributes the least to the polymer properties. The obtained dependencies of the MECP properties on the structural fragments of the complex hardeners allow preliminary evaluation of the structure of the chelates and epoxy–chelate compositions necessary to produce epoxy polymers with required properties. The new method of the theoretical investigation of the effect of the structural fragments (method of TIESF) of the polymer matrix on the polymer properties can be used to analyze the structures of the polymers of other classes and to predict the optimal structures, promising the production of the materials with the optimal properties. © 1

ISSN:0021-8995    

DOI:10.1002/app.1993.070480407

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe reaction of poly(vinyl chloride) (PVC) with mercaptoalkyltrialkoxysilanes yielded silane‐grafted PVC that can be cross‐linked by the hydrolytic mechanism. The grafting of the silanes on the plasticized and unplasticized PVC was carried out at 180° C during processing in the presence of basic lead‐containing stabilizers. The reaction is favorably affected by the presence of plasticizers and lubricants containing polar, preferably ester, groups. The silane‐grafted and cross‐linked polymers have satisfactory thermal stability. The results of strength measurements at elevated temperatures after cross‐linking by water indicate that the material obtained has greatly improved parameters that are suitable for a number of applications. © 1993 John Wi

ISSN:0021-8995    

DOI:10.1002/app.1993.070480408

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe cross‐linking of plasticized and unplasticized poly(vinyl chloride) (PVC) grafted with amino‐ and mercaptoalkyltrialkoxysilanes has been studied in water and in air at 20–140°C. In both media, the cross‐linking occurs faster for plasticized PVC grafted with aminosilanes; however, at temperatures above 100°C, the effect of degradation cross‐linking is apparent. For mercaptosilanes, a marked dependence of the cross‐linking rate on the silane structure was found; plasticized PVC with grafted 3‐mercaptopropyltrimethoxysilane was cross‐linked in water at 100°C after 6 h, whereas this process took 12 h for 5‐mercaptopentyltriethoxysilane. Practically no cross‐linking occurred in unplasticized PVC belowTg, whereas the rate at 100°C was comparable with that for plasticized PVC. The cross‐linking rate is affected by the chain mobility, water content, and diffusion of water into the material; a very slight dependence on the thickness of the material was found for plasticized PVC. ©

ISSN:0021-8995    

DOI:10.1002/app.1993.070480409

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

年代:1993

数据来源: WILEY

摘要:

AbstractA relationship between dynamic storage modulus (E′) and the mean cross‐polarization time constants 〈TCH〉 for 16 polymer data sets has been established by using a standard linear solid model. This model is used in an attempt to equate the process of cross‐polarization with mechanical rigidity by virtue of the implicit dependence of each phenomenon on molecular motion. The apparent validity of the relationship between these parameters indicates that cross‐polarization in polymers can be a function of molecular motion in addition to microscopic spin dynamics. The limitations as well as practical applications of this relationship are discussed. © 1993 John Wil

ISSN:0021-8995    

DOI:10.1002/app.1993.070480410

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

年代:1993

数据来源: WILEY