摘要:

AbstractA group of phenolic antioxidants was synthesized, characterized and the performance of these antioxidants in polymer processing was tested in the polymer melt by multiple extrusions. The change in melt flow was observed and compared with the change in melt flow by use of commercially available antioxidants. All the antioxidants examined had the same phenolic stabilization moiety but varied in the size of the substituents in the para‐position of the aromatic ring. Increasing length of the side chain considerably influences the behaviour of the antioxidants in the polymer and thus their effectivenes

ISSN:0003-3146    

DOI:10.1002/apmc.1994.052150101

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractCalcium carbonate of various particle shape (spheric, cubic, needle‐shaped type) and polypropylene (PP) were mixed on a two roll mill and the mixture was pressed into plates. The effect of particle shape on the crystallization behavior of PP/CaCO3composites, such as crystallization peak temperature (TMAX), crystallized pattern, etc., was investigated with differential scanning calorimetry measurements. The value of TMAXis explained by the total surface area of added CaCO3particles; TMAXof needle‐shaped series is larger than that of cubic or spheric ones. TMAXof various shaped CaCO3‐filled PP totally depends on the cooling rate and maximum temperature in the non‐isothermal crystallization, respe

ISSN:0003-3146    

DOI:10.1002/apmc.1994.052150102

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractScrap latex products contain rubber hydrocarbon of very high quality, that is only slightly crosslinked. A novel economic technique for converting such latex waste into a processible material is developed. This paper reports the effect of adding this latex reclaim to natural rubber. It is shown that latex reclaim can replace raw natural rubber up to about 50 wt.‐% without affecting mechanical propertie

ISSN:0003-3146    

DOI:10.1002/apmc.1994.052150103

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractA quantitative study was carried out on the homogeneous zirconocene dichloride/methylalumoxane/trimethylaluminum (Cp2ZrCl2/MAO/TMA) catalyst system in ethylene polymerization. The effects of variation of the AlMAO/Zr ratio, absolute Zr concentration, and addition of TMA on ethylene polymerization activity and polymer properties were investigated. The polymerization profiles for small AlMAO/Zr ratios and the changes with the Zr concentration are explained with a complexation equilibrium for the active homogeneous complex and with the change to a heterogeneous catalyst upon polymer precipitation. Good polymer productivities can be achieved at AlMAO/Zr<1000 when working at Zr concentrations between 10−4and 10−5mol/l with addition of TMA (AlMAO/AlTMA≈

ISSN:0003-3146    

DOI:10.1002/apmc.1994.052150104

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe system zirconocene dichloride/methylalumoxane was supported on silica in order to provide ethylene polymerization catalysts for suspension or gas phase processes. Highest activity was found for a sandwich‐like, three layer anchoring of the zirconium centers on the support surface. The new catalyst systems show a decrease of activity compared to polymerization experiments in homogeneous phase. However, the molecular weights are increased and the weight distributions remain narrow by immobilization of the active catalyst sites. Those supported metallocene catalysts could find application for the synthesis of polyethylene materials with controlled rheolog

ISSN:0003-3146    

DOI:10.1002/apmc.1994.052150105

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractSome hydrogels of different chemical composition were synthesized using 2‐hydroxyethyl methacrylate, methacrylic acid, acrylic acid, and acrylamide in different ratios and crosslinked by ethylene dimethacrylate. Effects of the copolymer composition as well as the type of monomers on some hydrogel characteristics were evaluated. Some characteristic properties, namely soluble fraction percentage, swelling degree, solution uptake, and salt uptake were found to be markedly affected by the hydrogel compositio

ISSN:0003-3146    

DOI:10.1002/apmc.1994.052150106

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe conditions of the preparation of formaldehyde/urea (F/U) resins have been supervised with the aim to reduce formaldehyde emission by influencing the ratio of methylene/dimethylene‐ether‐bridge linkages in the product.The most crucial point of this task is to keep the pH values of the reacting mixtures on the required level. The effect of formic acid, unevitably present in industrial formaldehyde solutions, was neutralized by applying a new buffer system, containing boric acid and ethylene gly

ISSN:0003-3146    

DOI:10.1002/apmc.1994.052150107

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractA rapid and convenient procedure was developed for the determination of the substituent pattern of carboxymethyl cellulose (CMC) by means of high‐performance liquid chromatography. The hydrolysates of CMC are separated on a polystyrene‐based strong cation‐exchange resin into glucose, 2,3,6‐tri‐O‐carboxymethyl glucose and groups of 2‐, 3‐and 6‐mono‐O‐ and 2,3‐, 2,6‐, and 3,6‐di‐O‐carboxymethyl glucoses. By this method the determination of the average degree of substitution as well as the substituent pattern is possible. In this way we found that CMC samples which were synthesized in LiCl/N,N‐dimethylacetamide as a cellulose solvent, contain a significantly higher amount of both tricarboxymethylated and unsubstituted units than those obtained in a slurry of cellulose in isopropanol/water at comparable DS values. The substituent pattern of heterogeneously synthesized CMC i

ISSN:0003-3146    

DOI:10.1002/apmc.1994.052150108

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractWater‐soluble cationic polymers were obtained by polyaddition of poly(ethylene glycol) (PEG) diglycidylethers (M̄nof PEG were 396, 587, 1437 and 3554, resp.) with asymmetrical diamines such as N,N‐dimethyl‐1,3‐diaminopropane and N,N‐diethyl‐1,3‐diaminopropane. The cationic polymer properties depend on the PEG initial molecular weight and on the diamine reactivity too. PEG with M̄n= 396 had the best behaviour in these reactions. The polyelectrolyte feature of cationic polymers was emphasized both in dilute aqueous solutions and in 2M aqueous NaCl solutions. The polyelectrolyte behaviour in 2M aqueous NaCl solution is determined by the PEG

ISSN:0003-3146    

DOI:10.1002/apmc.1994.052150109

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe semi‐empirical molecular orbital method AM1 has been used as a tool for the prediction of radical intermediates and crosslink structures that may be of importance in the direct laser excitation of siloxanes. Special emphasis was put on configuration interaction (Cl) in order to calculate energies and geometries of excited triplet states as well as potential curves of triplet reactions. Heats of formation of intermediates and reaction enthalpies of monomolecular fragmentation reactions of T1excited states of 2‐phenyl‐1,1,1,2,3,3,3‐heptamethyltrisiloxane and octamethyltrisiloxane were calculated. In the former case bimolecular reactions were also considered. Dissociation of a methyl group was found to be the most probable monomolecular fragmentation. Consecutive reactions of the silyl radical formed lead to crosslink structures like SiCH2Si and SiC6H4Si. Biphenyl‐ and phenylcyclohexadienyls are the most probable crosslink structures of bimolecular reactions with phenyl exciplexes as intermediates. Experimental evidence is given for these cro

ISSN:0003-3146    

DOI:10.1002/apmc.1994.052150110

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY