摘要:

AbstractThe reaction of mesyl chloride with crosslinked pullulan microparticles was investigated, in particular the influence of the reaction conditions on the ratio between the two possible products chlorodeoxy or O‐mesyl pullulan. It was found that in N,N‐dimethylformamide the preponderent reaction product is chlorodeoxy pullulan, while in pyridine at low temperatures the main product is the mesyl ester of pullulan. In N,N‐dimethylacetamide, the substituent groups are both chlorodeoxy and mesyl ones, in about 2:1 ratio. By the introduction of either chlorodeoxy or mesyl groups, the pullulan‐crosslinked microparticles become hydr

ISSN:0003-3146    

DOI:10.1002/apmc.1996.052410101

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe yielding and the fracture behaviour of an intercrosslinked polymer network obtained by the simultaneous curing of an unsaturated polyester (UP) and a thermosetting bismaleimide resin (BMI) was investigated in a wide range of temperatures and testing rates. The yield stress σyand the Young's modulus E increase by increasing the testing rate and decreasing temperature. Moreover, under the same testing conditions, σyand E increased as the BMI content in the blend was enhanced. On the other hand, it was found that the fracture parameter Kcwas not affected by the presence of BMI. The yielding process was analyzed using the theories both of Argon and Bowden and the molecular parameters derived there were related to the molecular structure of the network developed upon curin

ISSN:0003-3146    

DOI:10.1002/apmc.1996.052410102

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractA series of seven polyketones was prepared by Friedel‐Crafts reaction using 2‐chloroanisole, choroacetyl chloride, 1,2‐dichloroethane and dichloromethane with anhydrous aluminium chloride as catalyst and carbon disulfide as a solvent under different experimental conditions. The polyketones thus obtained were characterized by determination of the chlorine content (Carius method), IR spectroscopy, vapour‐pressure osmometry, thermogravimetry and differential scanning calorimetry. All these polyketones were tested for their antimicrobial properties against selected microorganisms. The results indicate that some of these resins show fair to good antimicrobial properties towards tested microorganisms and may be used as commercial b

ISSN:0003-3146    

DOI:10.1002/apmc.1996.052410103

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractPoly(4‐hydroxybutyl acrylate) poly(4‐HBA) was graft‐copolymerized onto silk fibres (bombyx mori) in aqueous medium with ammonium persulfate as initiator. The weight gain increased with increasing concentration of monomer in the grafting system. The grafting efficiency ranged from 45 to 65%. Equilibrium moisture regain decreased sharply beyond 10% weight gain. The tensile properties of the silk fibres did not change significantly as a function of the increasing weight gain. Birefringence and isotropic refractive index decreased until 35% weight gain and then remained unchanged. The X‐ray diffraction patterns showed that the crystalline structure was not affected by grafting. Differential scanning calorimetry (DSC), thermomechanical (TMA), and thermogravimetric (TG) measurements showed that poly(4‐HBA)‐grafted silk fibres underwent only slight changes in the thermal behaviour. The dynamic mechanical measurements (DMA) exhibited a downward shift of both the storage (E′) and loss modulus peak (E″) with increasing weight gain. Scanning electron microscopy (SEM) observations showed the presence of some deposits adhering to the surface of silk fibres grafted at high monomer/si

ISSN:0003-3146    

DOI:10.1002/apmc.1996.052410104

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractIn an early stage of the polycondensation of phenol/formaldehyde (Ph/F) systems catalyzed by bivalent metal acetates (Me2+(ac)2), 2‐hydroxy‐benzylalcohol (2‐OH‐BA) formation was selective in the weak acidic medium and only in the presence of the catalyst. The concentration change in 2‐OH‐BA and its hemiformal (HF) was followed by GPC as a function of the pH value of the system and the catalyst concentration and was found to be independent of the type of metal used in the catalyst but dependent on the pH value of the medium and on the catalyst concentration. An extremely high catalyst concentration does not cause further increase in the overall rate of 2‐OH‐BA formation. It was proved by1H NMR that at higher conversion and in the presence of Me2+(ac)2catalyst, the o‐o′‐ArCH2Ar isomers are dominating over o, p′ and p,p′ ones. Novolacs with overwhelming o‐diphenylmethane structures are thermally stable up to 400°C and can be crosslinked witho

ISSN:0003-3146    

DOI:10.1002/apmc.1996.052410105

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe partial hydrolysis of cellulose acetate was studied in homogeneous toluene/acetic acid/water media of different compositions using sulfuric acid as a catalyst. The presence of toluene considerably increases the hydrolysis rate. Products with a degree of substitution (DS) of about 1.70, useful for further derivatization, were obtained at 60°C with 15–34 wt.‐% toluene in the reaction medium and without addition of water during the process in shorter times than in the conventional procedure free of toluene. The kinetic behaviour of toluene‐containing systems is dependent on the composition of the reaction medium, as well as on the temperature. The reaction systems with 15 wt.‐% and 20 wt.‐% toluene, respectively, were found to obey a linear relationship of ‐ln(DS/DS0) versus time. The behaviour of the studied reaction systems is tentatively explained by an enrichment of the solvation shell in water and sulfuric acid, since the acidity function of the sulfuric acid was not influenced by the presence of toluene. The hydrolysed products obtained by the described procedure are soluble in some common organic solvents used for derivatization, such as dimethylformamide, acetic acid and dimeth

ISSN:0003-3146    

DOI:10.1002/apmc.1996.052410106

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractDifferential scanning calorimetry (DSC), Fourier‐transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X‐ray photoelectron spectroscopy (XPS) were used to study the miscibility of blends of a graft copolymer of poly(methyl methacrylate) on linear low density polyethylene (LLDPE‐g‐PMMA, G‐3) with poly(vinylidene fluoride)Systematic name: poly(1,1‐difluoroethylene).(PVF2) and the compatibilization of blends of LLDPE/PVF2. The specific interaction between PMMA side chains and PVF2in G‐3/PVF2binary blends is weaker than that between the homopolymers PMMA and PVF2. There are two states of PVF2in the melt of a G‐3/PVF2(60/40, w/w) blend, one as pure PVF2and the other interacting with PMMA side chains. The miscibility between PMMA side chains and PVF2affects the crystallization of PVF2. LLDPE‐g‐PMMA was demonstrated to be a good compatibilizer in LLDPE/PVF2blends, improving the interfacial adhesion and dispersion in the latter. Diffusion of PMMA side chains into PVF2in the interfacial region reduces the crystallization rate and lowers the melting point (Tm) and the crystallization temperature (Tc) o

ISSN:0003-3146    

DOI:10.1002/apmc.1996.052410107

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractMatrix‐assisted laser desorption/ionization mass spectrometry is shown to be a suitable method for the analysis of condensation polymers. Although these products are rather low in molar mass, they exhibit a complex chemical structure. Phenolic novolacs and resols can be analysed with respect to the degree of polymerization and the type and number of functional groups. Modified phenolic resins, such as epoxidized novolacs, can be identified and the degree of epoxidation can be determined. It is shown for polycarbonates and polyesters that depending on the reactant ratio linear oligomers with different endgroups and cyclic oligomers are forme

ISSN:0003-3146    

DOI:10.1002/apmc.1996.052410108

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractSeven homologous samples of a thermoplastic polyurethane (TPU) were characterized in dilute solutions of N‐methyl‐2‐pyrrolidinone (NMP) by size exclusion chromatography (SEC) on normal‐phase silica gel, low‐shear viscometry and membrane osmometry. The Staudinger‐Mark‐Houwink (SMH) constants of this homologous series were obtained by a new procedure of calculation on the basis of universal calibration of SEC with narrow polystyrene standards. The calculated SMH constants for these TPU samples in NMP at 298 K (K = 3.94 mL g−1, a = 0.29) prove the branched structure of this TPU samples and were further confirm

ISSN:0003-3146    

DOI:10.1002/apmc.1996.052410109

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractDie Härtung verschiedener Epoxidharzsysteme wurde mit Hilfe der dielektrischen Analyse verfolgt. Da sie sehr empfindlich ist, erwies sie sich zur Beobachtung der Nachhärtungsperiode besser geeignet als die Differentialkalorimetrie. Am Beispiel der Vernetzung von Diandiglycidylether mit anhydridmodifizierten Phenolnovolaken wird gezeigt, daß mittels dielektrischer Analyse die Bestimmung von Glasumwandlungstemperaturen möglich ist; dagegen ist diese Methode für die Ermittlung von Gelierzeiten nicht geei

ISSN:0003-3146    

DOI:10.1002/apmc.1996.052410110

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY