摘要:

AbstractOxygen as a promoter of radical polymerisation of ethyl acrylate was studied in the aqueous medium. Cu2+was chosen as the catalyst for the ascorbic acid (AA)—02redox reaction, constituting a three component initiating system. The rate of polymerisation,Rp, was observed to increase, remain constant and then decrease with increasing [Cu2+].Rpincreased with [O2] upto ∼ 6.5 × 10−4M and thereafter remained constant. [AA]>1.2 × 10−3M did not influence the rate.Rpalways increased with monomer [M] at fixed [Cu2+], [O2] and [AA]. However, the order with respect to [M] increased with increasing [Cu2+]. The rate of polymerisation increased with ionic strength, μ and decreased with [H2SO4]. There was an initial increase inRpfollowed by a decrease with increasing temperature. Conditions were identified whereRpdepended only on [Cu2+] and [M]or [M] only for industrial exploitation. Kinetic chain length of the polymers obtained under various experimental conditions were determined visco

ISSN:0007-1641    

DOI:10.1002/pi.4980140302

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractHybrid organosiloxane/sodium silicate structures have been prepared by the interaction of a‘QM’ polyorganosiloxane, produced by the trimethylsilylation of‘Suzorite’ (a phlogopite mineral), and a solution of sodium hydroxide in ethanol.These hybrid products lose volatiles on heating and give products which exhibit glass transition points at (∼ 520°C). They show properties intermediate between those of typical organosiloxanes and silicates. They have both hydrophobic and hydrophilic properties as demonstrated by their solubility in water and acetone. This is dependent on the relative proportions of Na, Si(O1/2)4and (Me)3SiO1/2grou

ISSN:0007-1641    

DOI:10.1002/pi.4980140303

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract‘QMD’ polymers have been prepared by the interaction of‘QM’ polymers (derived from a phlogopite) with (a) Me2SiCl2, (b)ClSiMe2(OSiMe2)7OSiMe3, and (c) CISiMe2(OSiMe2)7OSiMe2Cl.Reaction of the products with sodium hydroxide in ethanol gives materials the structures of which are hybrids of polyorganosiloxanes composed of Si(O1/2)4, Me3SiO1/2and Me2Si(O)1/2)2building units with sodium silicate units e.g. (O1/2)2Si(O−Na+)2.These materials have melting points below 150°C, some products have been shown to form films from aqueous solution and fro

ISSN:0007-1641    

DOI:10.1002/pi.4980140304

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractSodium metabisulphite (Na2S2O5) has been found to initiate the aqueous polymerisation of methyl methacrylate (MMA) at 35°C in phosphate buffer solutions of pH 6.85 and a constant ionic strength (μ) of the media in an inert atmosphere of pure nitrogen. The reaction has a well defined induction period which is a function of the concentrations of the initiator, of the monomer and also of temperature. The polymerisation is signalled by the sudden appearance of a haze at the end of the induction period in a given run, and the polymer separates out as a coarse precipitate during the progress of the polymerisation reactions. When the conversion is over 50 per cent complete, the polymerisation media looks like a thick curd if the monomer concentration is relatively high. The rate of polymerisation is found to decrease with conversion or time in a given run, and the initial rate (vp), obtained by extrapolating the linear yield/time versus time curves to zero time, keeping the conversion below 10 percent, is found aswhere (I) = initiator concentration in the range, (0.26 to 3.94) × 10−3(mol dm−3), and (M) = monomer concentration in the range 0.019 to 0.141 (mol dm−3). At high initiator concentrations, the rate of polymerisation is found to decrease. In a given run, the viscosity average molecular weights (Mv) of the polymers is found to increase quickly with a conversion of up to 25 to 30 percent, and then slowly with the further increase in conversion. (Mv) however is found to decrease with the increase of the initiator concentrations at a given conversion but increases with the increase of the monomer concentrations. Hydroquinone inhibits the polymerisation reactions, whereas air is found to increase the induction period, but later enhances the polymerisation rate in the same run. It has been shown that the bisulphite addition reaction of MMA is not important under the experimental conditions, and the polymerisation occurs by the free radical mechanism. The rate constant (k2) of the reaction,has been estimated from the analytical data as, k2= 14.62 × 10−2(dm3mol−

ISSN:0007-1641    

DOI:10.1002/pi.4980140305

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractThe dilute solution properties of nine poly(vinylpyrrolidone) fractions in methanol covering the molecular weight range 6.76 × 104to 1.02 × 107were studied. Constants a and Kmof the Mark‐Houwink‐Sakurada (M.H.S.) equation were found to be 0.60 and 2.64 × 10−4respectively using light scattering and intrinsic viscosity data and were compared with the literature values. The second virial coefficient, A2decreases gradually as the molecular weight increases while the root‐mean‐square radius of gyration,2 z1/2increases. The dependence of A2on molecular weight is in agreement with other flexible polymers dissolved in moderate to good solvents. The unperturbed chain dimension, (r 0−2/M) was calculated using the Stockmayer‐Fixman (S—F) equation and a value of 4.9 × 10−17cm was obtained. The S—F plot slightly bends in the region of high molecular weight which

ISSN:0007-1641    

DOI:10.1002/pi.4980140306

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractPoly(hexamethylene oxide) obtained by two routes, polycondensation and cationic polymerisation, is fractionated and its molecular weight distribution is analysed by using well known data treatment methods namely those of Beall, Wesslau, Tung and Saiz and Horta. The results are compared and discussed showing that the polycondensated sample has a lower molecular weight and wider distribution than the cationic one.

ISSN:0007-1641    

DOI:10.1002/pi.4980140307

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractThe modified statistical theory of rubber elasticity introduced by Flory5is designed to take into account the constraints on the fluctuations of network junction points arising from spatial occupancy of neighbouring chains. This theory has been applied by Erman2with some success to the rather limited experimental data of Jones and Treloar6for natural rubber subjected to biaxial strains of the most general type. However, when applied to the more extensive data of Vangerko and Treloar12he theory is found to be seriously inadequate in the high‐strain region. This inadequancy is thought to be due primarily to the neglect of the limited extensibility of the network chains, though straininduced cystallisation may also play some par

ISSN:0007-1641    

DOI:10.1002/pi.4980140308

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractStress‐strain properties and swelling measurements were used to characterise networks obtained either by peroxide curing or by photocrosslinking.It was shown that the value of the average molecular weight of a network strand (Mc) is dependent on its methods of determination (mcffrom modulus,Mcv2mfrom swelling ratios) and that the value of the ratioMcp/Mcv2mis a characteristic of each crosslinking process. Moreover, the results have shown that the homogeneity of distribution of the crosslinks is dependent on the crosslinking process use

ISSN:0007-1641    

DOI:10.1002/pi.4980140309

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980140301

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY