摘要:

AbstractArticles manufactured from plastic materials are generally enhanced visually by the incorporation of pigments, dyes and fluorescent brightening agents. This article provides an overview of the requirements of these colouring materials for use in plastics and of the structures and properties of the most important products in commercial use.

ISSN:0959-8103    

DOI:10.1002/pi.1994.210340401

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe dielectric behaviour of hydroxypropyl cellulose in dioxan has been studied at 10–50°C over a range of concentration of 10–55 wt% to include the isotropic and anisotropic phases. The study showed that the loss maximum ε″maxmagnitude of polarization ε0− ε∞relaxation time 1/2πfmdegree of broadening of the absorption curves 1–hor α, and the mean‐square dipole moment 〈gμ2〉, steadily increase with concentration up to 42 wt%, above which a rapid decrease takes place. This indicates that the isotropic solution transforms to an anisotropic solution with a smaller mean dipole moment. The critical concentration is realized to be temperature invariant. This was evidenced by measuring the refractive index of solutions covering the same concentratio

ISSN:0959-8103    

DOI:10.1002/pi.1994.210340402

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractPolymer‐anchored Pd(II) complex catalyst was sythesised by sequential attachment of 1,2‐diaminopropane as a ligand to the chloromethylated commercially available styrene‐divinylbenzene copolymer (XAD‐2). The catalyst was characterised using techniques such as FTIR, SEM, EPR, and UV‐VIS reflectance spectroscopy. Other physicochemical properties, such as bulk density, moisture content, swelling and surface area by the BET method at low temperature by nitrogen adsorption, were also studied. The catalyst was tested for the rate of hydrogenation of cyclohexene. The influence of various factors such as temperature, concentration of catalyst, substrate, and quantity of solvent have been determined. The results are compared with the homogeneous analogue. The recycling efficiency of the catalyst was als

ISSN:0959-8103    

DOI:10.1002/pi.1994.210340403

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractA dielectric dispersion and frequency loss peak within the low frequency range 0.05–1 kc/s and at temperatures of 283–333 K was observed in the case of the sodium salt of carboxymethyl cellulose and absent in the case of its acid form. The critical frequency of the dielectric absorption was independent of molecular weight and of the presence of low moisture content. The results obtained show that the variation with temperature of the dielectric constant is exponential at low frequency only in the case of the sodium salt of carboxymethyl cellulose. The significance of the results is discus

ISSN:0959-8103    

DOI:10.1002/pi.1994.210340404

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe thermal discharge behaviour of cellulose diacetate (CA2) (39% acetyl content) and cellulose triacetate (CA3) (44% acetyl content) films was studied at different polarizing temperatures and fields. Cellulose diacetate exhibited two peaks, one at low temperatures and the other at high temperatures, whereas cellulose triacetate exhibited only one peak. The origin of these peaks in CA2 is attributed to dipolar orientation and space charge polarization respectively, while the only peak in CA3 is due to space charge polarization. The difference in thermal discharge behaviour of CA2 and CA3 is attributed to the difference in acetyl contents of the two acetates.

ISSN:0959-8103    

DOI:10.1002/pi.1994.210340405

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe corona discharge technique was explored as a means of forming chemically active sites on cellulose surfaces. Paper thus treated was brought into contact with the reaction medium, a styrene–methanol mixture.The corona discharge was generated between two flat circular electrodes separated by a quartz disk. Scanning electron microscope analysis and wettability studies indicated that a hydrophobic film coated the cellulosic fibers.The molecular weights of both the homopolymer and the copolymer were characterized by GPC. Two peaks for grafted copolymer were observed, the first having about the same average molecular weight as the homopolymer, and the second having a molecular weight of about ten times the first fraction.A polymerization mechanism is propose

ISSN:0959-8103    

DOI:10.1002/pi.1994.210340406

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractInterpolymer complex formation between poly(N‐vinyl‐2‐pyrrolidone) (PVP) and poly(monomethyl itaconate) (PMMel) has been studied. Data from Dynamic Light Scattering show at least two different size distributions of polymer complex (PC). The PC size distributions increase when the temperature increases. Viscosity measurements were also performed in order to estimate the polycomplex segmental density. From these results it can be concluded that PVP and PMMel give rise to a polycomplex formation and the driving force for this association is hydrogen bonding as much as hydrophobic interac

ISSN:0959-8103    

DOI:10.1002/pi.1994.210340407

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractAn attempt was made to clarify the effect of addition of organoaluminum and organoboron compounds in the stereospecific polymerization of acrylonitrile (AN) initiated by dialkylmagnesium (R2Mg) above 100°C. The triad isotacticity (i.e. the content ofmm(m: meso)) as well as the viscosity‐average molecular weight (M̄v) of polyacrylonitrile (PAN) increased when trialkylaluminum (R3Al) and trialkylboron (R3B) were used as additives. Diisobutylaluminum hydride [(i‐C4H9)2AlH] was found to be the best additive. in the stereospecific polymerization of AN, giving PAN with higher (mm) content (0.63), higherM̄vvalue (5.2 × 104), and a yield approximately double that obtained using (n‐C6H13)2Mg alone. When the (n‐C6H13)2Mg/(i‐C4H9)2AlH system was used, the yield, (mm), andM̄vof PAN increased with polymerization temperature (Tp); maximum values of yield, (mm), andM̄vwere obtained atc. 130°C. The optimum amount of additives was approximately equimolar to R2Mg as initiator. The13C chemical shift of α‐carbon in R2Mg at 90°C shifted by mixing with R3Al and R3B, respectively, indicating the existence of interaction between R2Mg and the additives. The main role of the additives is considered to be suppression of the self‐association of R2Mg by strong

ISSN:0959-8103    

DOI:10.1002/pi.1994.210340408

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe transient currents in the discharge mode in polymethylmethacrylate (PMMA) and malachite green doped PMMA films measured as a function of temperature (363–383 K) and field strength (2.0 ×103‐2.0 × 104V/cm) have been found to follow the Curie–von Schweidler law, characterized by different slopes in the short and long time regions. Various mechanisms which may be responsible for the time‐dependent transient currents of pure and malachite green doped PMMA films are discussed. The effect of doping with malachite green on the discharge current indicates the formation of molecular a

ISSN:0959-8103    

DOI:10.1002/pi.1994.210340409

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe dielectric characteristics of cyanoethylated cellulose samples having different degrees of substitution have been investigated at different frequencies from 0.1 to 10 KHz and at temperatures from −40°C to 180°C. Two relaxation processes, designated as α and β in order of decreasing temperature, were recognised. The low temperature β‐relaxation is expected to be due to local motion of anhydroglucose rings, while the α‐relaxation is related to the side group motion. The data obtained are discussed in terms of the progressive destruction of the fibre structure, together with the increase of side group polarity due to cyan

ISSN:0959-8103    

DOI:10.1002/pi.1994.210340410

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY