摘要:

AbstractTwo polypropylenes produced by different conversion routes were extruded as film with added amounts of sodium benzoate between 0.025% and 0.5% by weight. The resultant structures were shown to be a function of casting conditions, molecular features of the base polymer and induced degree of nucleation. At high casting temperatures and with higher percentage of nucleating agents the characteristic skin‐core structure was reversed; the film exhibiting a coarse spherulitic skin and a fine structure in the core. These conditions also gave rise to notable as‐cast orientation. Addition of the highest levels of sodium benzoate resulted in a non‐spherulitic crystalline core structure. As would be expected the elastic modulus and the yield strength of the films increased with percentage crystall

ISSN:0007-1641    

DOI:10.1002/pi.4980210402

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe coupling of 5‐nitro‐2‐furaldehyde‐semicarbazone on to poly(acrylic acid‐co‐vinyl alcohol) copolymer by the use of dicyclohexylcarbodiimide as activator has been studied.On the basis of an experimental design, the influence of different parameters is studied (activator/support, drug/support, reaction time, solvent volume) in order to determine the optimum conditions for obtaining the maximum amount of the coupled drug on

ISSN:0007-1641    

DOI:10.1002/pi.4980210403

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe thermal stabilities of eleven different epoxy resin formulations, ten different polyimide resin formulations, a triazine resin formulation and two aromatic thermoplastic matrices have been compared by isothermal gravimetry in air. The overall activation energies for degradation as a function of percentage weight loss have been determined by regression analysis of the isothermal data. The values obtained indicate a very complex breakdown mechanism in the majority of cases.

ISSN:0007-1641    

DOI:10.1002/pi.4980210404

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractResults are given for the effects of two added inorganic electrolytes, potassium chloride and calcium chloride, upon the kinetics of the emulsion homopolymerisation of styrene and of the emulsion copolymerisation of styrene with a minor amount of acrylic acid, using sodium dodecylbenzenesulphonate as surfactant and potassium persulphate as initiator. Three reaction systems were investigated. Two were for the emulsion homopolymerisation of styrene, one reaction system using a relatively high level of surfactant and the other a relatively low level of surfactant. The third reaction system was for the emulsion copolymerisation of styrene and acrylic acid using an intermediate level of surfactant. The results show that the effects of added electrolytes can be varied and complex: they depend upon several factors such as the nature and amount of the added electrolyte, the level of surfactant, and the presence or absence of the acidic comonomer.

ISSN:0007-1641    

DOI:10.1002/pi.4980210405

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThis paper examines the physico‐chemical characteristics of a natural kaolin, its textural properties, pores, morphology, chemical surface, as well as chemical surface modification through treatment with quaternary ammonium salts in SBR mixes.Diallyldimethylammonium chloride was used as a quaternary alkali for surface modification of the kaolin, thus allowing the unsaturated allyl portion to covulcanize with the rubber. This achieved strong rubber‐filler bonds with consequential enhancement of the technological properties of the vulcaniz

ISSN:0007-1641    

DOI:10.1002/pi.4980210406

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractUltrasonic absorption and velocity measurements are reported on aqueous solutions of poly(vinyl alcohol) (PV‐OH) of different molecular weights and concentrations obtained using a pulsed ultrasonic apparatus operating at 2 MHz and 303 K. The variations in these parameters as a function of concentration are interpreted in terms of changes in the magnitude of the contribution due to relaxation of the backbone and of the side chain acetyl groups. The results show an increase in velocity, density and viscosity with increase in molecular weight and concentration of PV‐OH.In contrast the attenuation values decrease with increase in molecular weight. This suggests that interaction is occurring between PV‐OH and water molecules. Deviation of the variation of the attenuation with concentration from the ‘ideal’ dilute solution behaviour at high concentration is ascribed to the effects of polymer‐polymer interaction. The magnitude of the volume change associated with polymer‐solvent interactions is estimated and discussed.A mathematical equation correlating the relaxation amplitude and the molecular weight of the polymer is suggested. This approach was applied to the calculation of the molecular weight of four unknown samples of PV‐OH from their measured relaxation amplitudes. The results obtained agree well with those obtained

ISSN:0007-1641    

DOI:10.1002/pi.4980210407

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractDevelopments in models for emulsion polymerisation are considered; various types of model can be used and the choice depends on circumstances. Descriptions of batch processes include radical desorption, gel effects and molecular weight distributions. With flow reactors, allowance is made for variations in particle size and number. Population balances are useful in model formulation. Progress is being made with copolymerisation and the use of semi‐batch reactor

ISSN:0007-1641    

DOI:10.1002/pi.4980210408

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractTitanate coupling agents have been used for the surface modification of mica to improve the viscoelastic behaviour of mica‐filled polypropylene. Four titanate coupling agents, neoalkoxy tri(dioctylpyrophosphato) titanate (CA1), neoalkoxy trineodecanoyl titanate (CA2), bisacetylacetonatodistearato titanate (CA3), and bisacetylacetonatodipalmitato titanate (CA4), were used in the present investigation. Mica powder (10 μm, particle size) was coated with these coupling agents in varying concentrations (0.5‐10% based on the weight of the filler), and then blended with stabilised polypropylene powder of 10 melt flow index (MFI). The mica‐filled (10‐50 wt%) polypropylene samples were extruded and used in the granular form for studying the viscoelastic behaviour. The melt viscosity of titanate coated mica‐PP samples decreases irrespective of the nature of the coupling agent used. The activation energy of melt rheology is independent of the mica content. The die swell increases with the use of titanate coupling agent. Compatibility of mica and polypropylene has also been studied with the help of a scanning electron

ISSN:0007-1641    

DOI:10.1002/pi.4980210409

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980210410

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980210413

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY