摘要:

AbstractPolyimides were prepared from the reaction of two aromatic dianhydrides with two diamines containing carbonyl and ether connecting groups between the aromatic rings. The diamines were prepared from the reaction of 4‐aminophenol or (3‐aminophenol) with an activated aromatic difluoro compound (4,4′‐difluorobenzophenone) in the presence of potassium carbonate. Some of these polyimides were shown to be semicrystalline as evidenced by wide‐angle X‐ray diffraction. Glass transition temperatures were observed between 203 and 242°C. All polyimides were found to be thermally stable up to 400–450°C with a char yield of about 50–60% at 900°C. The effect of the structure on the properties of polyimides, such as crystallinity, glass transition temperature and thermal behav

ISSN:0025-116X    

DOI:10.1002/macp.1991.021920501

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractA series of rigid rod‐like polyspiroacetals bearing flexible side chains was prepared by interfacial polycondensation of 4,4′‐(2,4,8,10‐tetraoxaspiro[5,5]undecane‐3,9‐diyl)diphenol with 2,5‐dialkoxy‐substituted terephthaloyl dichlorides. The majority of these polymers were soluble in polar solvents like tetrahydrofuran (THF), dimethylformamide (DMF), CHCl3, phenol/CCl4(1 : 1 by vol.) mixtures, etc. The molecular weights ranged from 7 600 to 15 000 and the melting temperature from 182 to 228°C. Both of the above values decreased with increasing length of the side chains. The TG curves revealed 5% weight loss at 350–370°C under N2gas atmosphere. Wide‐angle X‐ray diffractograms showed that all of the polymers have considerable crystallin

ISSN:0025-116X    

DOI:10.1002/macp.1991.021920502

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractA study of the mechanism of thermal oxidative and thermal mechanical degradation of isotactic polypropylene (PP) is reported. Size exclusion liquid chromatography has been applied to the study of molar mass distribution (MMD) of samples of PP under oxidative degradation in the presence of an incorporated organic peroxide and of samples subjected to repeated extrusion. The change in MMD of the samples of PP under controlled oxidative degradation at 230°C is explained by a random chain scission mechanism and those of the samples of PP extruded repeatedly from an extruder at 280°C can be elucidated by a mechanism of mechanical chain scission with a threshold degree of polymerization 2L, below which the chain will not undergo scission. The value ofLwas found to be around 50

ISSN:0025-116X    

DOI:10.1002/macp.1991.021920503

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe catalyst NdCl3/EtOH/TiCl4(NSC) was prepared using NdCl3as carrier. The composition of the NSC was analyzed by IR, XPS, GC and titration. This catalyst and MgCl2/EtOH/TiCl4catalyst (MSC) were employed for the polymerization of ethylene and propene. The titanium component in NSC exists basically as Ti(OEt)Cl3but both as TiCl4and Ti(OEt)Cl3in MSC. NSC combined with organoaluminium compounds polymerizes ethylene with fairly high productivity. Both the activity and the concentration of active centresC*in ethylene polymerization with NSC‐AlEt3catalyst system decrease with increasing temperature, while the propagation rate constantkpincreases. The difference in the kinetic behavior for polymerization of ethylene between the NSC‐AlEt3and the MSC‐AlEt3catalyst system would arise mainly from the different stability and reactivity of the titanium active center. The activity for polymerization of propene by using NSC in comparison to MSC is ver

ISSN:0025-116X    

DOI:10.1002/macp.1991.021920504

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractCopolycondensation of ε‐caprolactone (CL) and δ‐valerolactone (VL) was performed in the presence and absence of phosphoric acid, in order to clarify the competition between the ring‐opening reaction of lactones and the polycondensation of linear compounds produced by this reaction. The gel permeation chromatography data showed that the monomer peaks remained in the system even after 7 h from start of the reaction when polymerized in the absence of phosphoric acid and, on the contrary, in the presence of phosphoric acid the peaks disappear perfectly within 1 h. The weight‐average molecular weights (M̄w) of poly(CL‐co‐VL), obtained by copolycondensation with and without phosphoric acid at 200°C for 1 h, were approximately 540 and 8900, suggesting that phosphoric acid markedly accelerates not only the rate of ring‐opening but also the rate of copolycondensation. On the other hand, the biodegradation of the copolyesters obtained is characterized by the action of a lipase‐type enzyme, showing a typical parabolic‐typ

ISSN:0025-116X    

DOI:10.1002/macp.1991.021920505

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe influence of several parameters on the polycondensation reaction of potassium maleate and 1,4‐dihalogenobutanes has been studied in 1‐methyl‐2‐pyrrolidone at moderate temperature. The yield and molecular weight of the obtained polyesters as well as the extent oftransisomerization and the nature of chain end‐groups depend strongly on the mole ratio of reagents, the nature of halogen in the 1,4‐dihalogenobutanes and on the presence of small amounts of water in the reaction mixture. In particular, it has been observed that water increases the consumption rate constant of 1,4‐dibromobutane but at the same time acts as a term

ISSN:0025-116X    

DOI:10.1002/macp.1991.021920506

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe feasibility of applying the method of factor analysis to X‐ray diffraction diagrams of binary blends of polypropylene and ethylene‐propylene‐diene terpolymer (PP/EPDM) was examined. The result of mathematical treatment was satisfactory. The number of scattering species and their concentrations in six kinds of PP/EPDM blends were determined. The separation of the spectral peaks of each species in the blends, contributing spectral intensities, was carrie

ISSN:0025-116X    

DOI:10.1002/macp.1991.021920507

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe heterogeneous graft copolymerization of a mixture of vinyl acetate (VAc) and methyl acrylate (MA) onto cellulose was carried out in an aqueous medium through a radical mechanism. Copolymerization led, as usual, to the simultaneous formation of grafted and non‐grafted poly(vinyl acetate‐co‐methyl acrylate). The reactivity ratios of VAc and MA were determined from high‐conversion data by using an integrated form of the copolymerization equation. Values of the reactivity ratios for VAc (r1= 0,020) and MA (r2= 6,750) were calculated. The capacity of the methods for determining reactivity ratios based on the differential copolymerization equation is discussed for the present copolymerization system. Some significant characteristics of the copolymer and the copolymerization reaction are deduced from the copolymerization parameters. It is concluded that the polymerization sites of the grafting and homopolymerization reactions are identical. Also, the present aqueous dispersion technique yields similar results as bulk polymeri

ISSN:0025-116X    

DOI:10.1002/macp.1991.021920508

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractSpin‐lattice relaxation times (T1) have been measured by13C NMR for poly(vinyl alcohol), poly(vinyl benzoate), poly(vinyl cinnamate) and poly(vinyl acetate) in dimethyl sulfoxide as a function of temperature and concentration. As expected,T1increases with increasing temperature and decreases with increasing polymer concentration. The influence of the microstructure (tacticity) of the polymers on the relaxation times is negligible.T1for the methine carbon of the polymer main chain is observed to serve as a measure of the rigidity and/or mobility of the chain. Assuming isotropic motion of the polymer chains, the activation energies for the protonated carbons were determined using the calculated correlation time

ISSN:0025-116X    

DOI:10.1002/macp.1991.021920509

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractMicrocapsules were prepared by a coupling reaction of disuccinimido 4,4′‐azobis(4‐cyanovalerate)Systematic name: 5,5′‐bis(imidooxy)‐2,2′‐dimethyl‐5,5′‐dioxo‐2,2′‐azodipentanenitrile.withL‐lysine, and/or polyallylamine in a water/oil emulsion system. The microcapsules show a light‐responsive release of an inner content, succinylated bovine serum albumin, to the outer bulk phase. Effects of the composition of the coupling suspension on the photo‐durability of the microcapsules obtained were examined. The microcapsules would be useful as a d

ISSN:0025-116X    

DOI:10.1002/macp.1991.021920510

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY