ISSN:0007-1641    

DOI:10.1002/pi.4980210602

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe natural log of critical micelle concentration (CMC) values obtained from the natural log discontinuities in surface tension‐concentration relationships, through the least‐squares regression analysis, were plotted against the respective hydrophile‐lipophile balance (HLB) values of four groups of ethoxylated octylphenol‐, dodecylphenol‐, tetradecylphenol‐ and hexadecylphenol‐formal‐dehyde polymeric surfactants.The obtained HLB‐CMC relationship for the investigated compounds can be represented satisfactorily by the linearized equation In (CMC) =a—b(HLB). Values of the two constantsa(intercept) andb(slope) for 16 of these compounds were determined at 28, 38, 48 and 58°C, using the least‐squares regression analysis of data. The study revealed that bothaandbvalues increase with increasing number of carbon atoms in the ethoxylates of polymeric compounds having a linear alkyl chain. The influence of branching is reflected in the values ofaandbof the compounds having a branched dodecyl chain.The most striking feature of the obtained equation is that the CMC decreases with increasing HLB (negative slope). This observation is contrary to what is generally expected for both ionic an

ISSN:0007-1641    

DOI:10.1002/pi.4980210603

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe interfacial tensions (IFT) of four low molecular weight groups of ethoxylated octylphenol‐, dodecylphenol‐, tetradecylphenol‐ and hexadecyl‐phenol—formaldehyde polymeric surfactants were determined using the spinning drop method. Some noteworthy features of the interfacial behaviour of dilute aqueous solutions of 16 of these compounds and homologous hydrocarbons are discussed.An important feature is that these surfactants behave similarly to monomeric ones in their hydrocarbon scan, that is they have a minimum IFT value against a particular member of a homologous hydrocarbon series. The magnitudes of the tension at minimum (γmin) values obtained in this study are of the order of ‘ultralow’ (10−2‐10−3mNm−1).Thenminvalues of these polymeric nonionic surfactants decrease with increasing hydrophilicity, that is decrease with the increase of ethylene oxide units condensed per mole of alkylphenol unit in the polymeric surfactants studied. In this case, the downward shift innminis smaller and apparently not linearly related to the number of EO units.Increasing the hydrophobicity of these polymeric nonionics, that is increasing the length of the alkyl chain from C8to C16, resulted in an increase in thenminvalues obtained.For each of the investigated groups, the lowest γminvalues are obtained with polymeric surfactants having the highest EO content. The optimum low tension performance occurs at the low end of the equivalent alkane carbon number scale (at EACNs below 6). Under the influence of added electrolytes these EACNs were s

ISSN:0007-1641    

DOI:10.1002/pi.4980210604

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractPoly(vinyl chloride) (PVC) films were grafted with methacrylic acid (MAA) using a simultaneous‐irradiation technique. The effect of solvent ratio (methanol‐water) on grafting was studied and maximum grafting was found for an equivolume mixture of methanol and water. The graft level increased with increase of the plasticizer (dioctylphthalate) content in PVC. Grafting was found to be higher at low dose rate and increased linearly up to 0.25 Mrad for all dose rates and then levelled off. Grafting also increased continuously with increasing monomer concentrations up to 5.4mol/litre, but a linear increase in grafting was observed only up to 2.5 mol/litre. The dependences of rate of grafting on dose rate and monomer concentration were found to be 0.62 and 1.20 respectiv

ISSN:0007-1641    

DOI:10.1002/pi.4980210605

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractTwo series of copolyesters containing both linear mesogenic and nonlinear, non‐mesogenic aromatic ester units, each with a decamethylene spacer, were prepared and characterized for the effect of the non‐mesogenic unit and the spacer on the stability of the liquid crystalline (LC) phase. The mesogenic units were formed from the reaction of 2‐chlorohydroquinone and 1,10‐bis(4‐carboxy‐phenoxy)decane while the non‐mesogenic units were derived from reacting either resorcinol (Series I) or bisphenol A (Series II) with the latter monomer. The non‐mesogenic units containing bisphenol A were found to be more efficient in destroying liquid crystallinity of the copolyesters than were resorcinol‐containing units. However, the presence of a flexible spacer in each unit allowed the copolymers to form a nematic LC phase even at contents of the resorcinol and bisphenol A non‐mesogenic units as high as 70 and 60

ISSN:0007-1641    

DOI:10.1002/pi.4980210606

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractLinear end‐blocked and crosslinked siloxane copolymers containing dimethylsiloxyl and methyl(1‐oxypyridin‐3‐yl)siloxyl groups were prepared and characterized thermally (TGA) and spectroscopically. These hydrophobic copolymers were found to be highly effective transacylation catalysts in the synthesis of carboxylic anhydrides and the hydrolysis of diphenyl phosphoro‐chloridate (DPPC) under phase‐transfer catalysis (PTC) conditions, i.e. CH2Cl2‐H2O suspension. The insolubility of the copolymers in water and the preference of the intermediate, polymeric 1‐acyloxypyridinium ion for the more lipophilic carboxylate ion in anhydride formation suggest that the reaction occurs at the CH2Cl2‐H2O interphase. The rapid rate of hydrolysis of DPPC under PTC conditions and in water provides evidence for initial hydrophobic binding or association of the hydrophobic catalyst prior to reaction with a water‐

ISSN:0007-1641    

DOI:10.1002/pi.4980210607

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe calorimetric properties and dynamic mechanical behaviour of pure poly(ethylene oxide) (PEO) and its blends with poly(N‐vinyl carbazole) (PNVK) have been examined as a function of composition in the range 50‐100% PEO. Thermomechanical measurements indicate the presence of a phase separation in this blend.Using the Hoffman‐Weeks plot no equilibrium melting point depression was found in any of the blends studied. Some kinetic interfacial effects were detected in the crystallization processes. For all blend compositions, the Avrami exponent is close to that obtained for pure PEO. The DMTA and DTA results suggest an incompatibility in this s

ISSN:0007-1641    

DOI:10.1002/pi.4980210608

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractA total of eighteen linear polysiloxanes of general formula Me3SiO‐(MeSi(E)O)x(MeSi(H)O)ySiMe3(E = —(CH2)nester; x+y = 40) have been prepared by the platinum catalysed addition of CH2=CH(CH2)n‐2‐ester to Me3SiO‐(MeSi(H)O)40SiMe3under anhydrous conditions. Polymers containing the ester functionalities—(CH2)3CO2R(R = Me, CF3, Et, Pr, and CH2COMe),—(CH2)3‐CHMeCO2Et, —(CH2)2CH(CO2Me)2, —(CH2)3CH(CO2Et)2, ‐(CH2)3CO2CH= CHCO2CH2CH=CH2and —(CH2)3CO2C6H4CO2CH2CH=CH2have been characterised by analysis and1H and13C NMR spectroscopies. Factors affecting Markownik off versus anti‐Markownikoff addition of allyl acetate to this polymethylsiloxan

ISSN:0007-1641    

DOI:10.1002/pi.4980210609

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe dependence of molecular weight of poly(methyl methacrylate) on reaction conditions, as polymerized in aqueous nitric acid with the redox system ceric ammonium nitrate‐glucose, has been studied. The average molecular weights and molecular weight distributions were determined by size‐exclusion chromatography. The degree of polymerization was found to increase in the course of a run and was also affected by changes of Ce(IV) and glucose concentrations in the range where the rate of polymerization increased, but not where the rate was independent of Ce(IV) concentration and decreased with glucose concentration. The average molecular weights can be controlled by variations in monomer concentration and in temperature. The polymerization rate was found to attain a maximum with nitric acid concentration whereas the rate of ceric ion consumption increased. A fall in the degree of polymerization was observed on increasing the acid concentration. The effect of nitrate ion concentration as well as of that of certain water‐miscible solvents on the above‐mentioned parameters has also been

ISSN:0007-1641    

DOI:10.1002/pi.4980210610

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe vibrational Raman spectra of single fibres of Nomex and Kevlar have been studied and vibrational assignments made. Commercial samples of Kevlar 29 and Kevlar 49 were found to be identical spectroscopically. Distinguishing features in the Raman spectra of Kevlar and of Nomex were identified for the purpose of spectroscopic or microprobe characterisation of these materials as single fibres or as small particles (∼ 2 μm). The Raman spectra of Kevlar and Nomex fibres which had been subjected to mechanical stresses of up to 4.5 kg mm−2were also analysed and comparisons made with previous results on stressing experiments in the literature for Ke

ISSN:0007-1641    

DOI:10.1002/pi.4980210611

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY