摘要:

AbstractC‐Fasern sind wegen ihrer herausragenden Festigkeit und ihres hohen Moduls für die verschiedensten technischen Einsatzgebiete von großer Bedeutung. Deshalb werden viele Anstrengungen unternommen, Fehlstellen in den Fasern, die die Eigenschaften praktisch begrenzen, zu minimieren. Eine deutliche Hilfe hierbei ist die Optimierung der Struktur der PAN‐Fasern, die zu C‐Fasern weiterverarbeitet werden. In der vorliegenden Arbeit wird für naßgesponnene PAN‐Fasern beschrieben, wie es durch Aufteilung der Verstreckung und angemessene Temperaturführung gelingt, Faser‐Strukturen einzustellen, die zu besseren C‐Faser‐Eigenschaften führen. Die praktischen Ergebnisse werden durch Stru

ISSN:0003-3146    

DOI:10.1002/apmc.1991.051920101

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractPorous copolymers of N‐vinylcarbazole (NVC) and divinylbenzene (DVB) of different composition (crosslinking degree) have been studied. The copolymers were obtained by suspension polymerization carried out in the presence of diluents, mixtures of ‘good’ (isopentanol and toluene) and ‘bad’ solvents (dodecane and toluene).The supermolecular structure of the copolymers was found to depend not only on the crosslinking degree, but on the thermodynamic quality of diluents. In the presence of good solvents, copolymers of the porous‐gel type were formed at relatively small crosslinking degree (<20% DVB).Sorption properties of porous NVC‐DVB copolymers with respect to p‐nitrophenol were found to be similar to those of acrylonitrile

ISSN:0003-3146    

DOI:10.1002/apmc.1991.051920102

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractA total of 12 water‐soluble N‐substituted polyaspartamides, some of these previously reported, are synthesized from the polysuccinimide1by nucleophilic ring opening and are characterized microanalytically and spectroscopically. The relative hydrolytic mainchain stabilities of the product polymers are evaluated in dialysis tests (6000–8000 molecular‐mass cut‐off) performed over periods of 24–48 h in aqueous solution in an effort to assess their suitability as homo‐ or copolymeric carriers for aqueous‐phase coupling to biologically active agents. In agreement with previous work, resistance to main‐chain degradation is found to be very poor with the N‐(2‐aminoethyl)‐ and N‐(3‐aza‐6‐oxahexyl)‐substituted derivatives2aand2b(10–20% recovery after 48 h), and moderately poor with the 3,6‐diazahexyl‐substituted2c(45% recovery). These three representatives, hence, cannot efficaciously be subjected to aqueous‐phase drugcoupling reactions save for short exposure times. Good to excellent stabilities, however, with product recoveries in the 70–95% range, are shown by the remainder of polymers,2d–21, all of which are characterized by the absence of primary or secondary amino groups in the side chains separated from the amide nitrogen atom by less than three carbon atoms. Polyaspartamides selected from this group for their promising drug coupling potential include the N‐(3‐aminopropyl)‐, N‐(3‐aminohexyl)‐, and N‐(2‐ṕiperazinylethyl)‐substituted types2e, 2fand2hpossessing primary or secondary amine functions as anchoring sites, and the N‐(2‐(dimethoxy)ethyl) derivative21, of interest as the precursor to a formyl‐functionalized carrier polymer. Lastly, the units of2iand2j, featuring 3‐(dimethylamino)propyl and 3‐(morpholin‐4‐yl)propyl substituents, lend themselves as solubilizing segments in copo

ISSN:0003-3146    

DOI:10.1002/apmc.1991.051920103

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractCopolymers of N,N‐dimethyl acrylamide (DMA) and isopropylmethacrylate (IPM) were prepared in dimethyl formamide using azoisobutyronitrile as initiator. The composition of copolymers was determined by1H‐NMR analysis. Reactivity ratios (rDMA= 0.58, rIPM= 2.76) were calculated from these values by using the Kelen‐Tüdős differential linear e

ISSN:0003-3146    

DOI:10.1002/apmc.1991.051920104

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe injection‐molded poly(1‐butene) (PB‐1) is found to be more brittle than the compression‐molded PB‐1. The morphologies of these specimens are examined by use of polarized optical microscopy and scanning electron microscopy (SEM). A skin layer and an oblate spherulitic structure extended to the core region are observed in the injection‐molded PB‐1, while typical spherulites exist in the compression‐molded PB‐1. Below the skin layer of the injection‐molded PB‐1, the fracture surface is found to consist of many aligned strip‐like voids with ribbon edges propagating to the center of the specimen and perpendicular to the flow direction of injection‐molding. Based on these observations, it can be inferred that shear stress induced by the melt flow during the injection‐molding does not only cause the formation of skin layer, but also penetrates deeply into the central region of the injection‐molded specimen causing the formation of oblate spherulites. The oblate spherulitic structure is responsible for the aligned voids during elongation of PB‐1, while the existence of the skin layer and the oblate spherulites in core region is responsible for the brittleness of the injection‐molded PB‐1. The elongation of the injection‐molded PB‐1 is found to be lower than that of the compression‐molded. This can be attributed not only to the presence of the skin layer but also to the oblate spherulites in the core region. The elongation can be improved by annealing at a te

ISSN:0003-3146    

DOI:10.1002/apmc.1991.051920105

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractA general numerical procedure is presented to calculate the modification of the basic equation for hydrodynamic lubrication brought about by the use of polymeric fluids with shear depending viscosity. The procedure is based on the generalized Newtonian fluid model and allows to treat continuously all the flow regions between the pure Newtonian and the power law behavior. The results show that the influence of the viscosity depending on shear stress is completely characterized by one dimensionless number, namely U.·τ*/h*, where U is the relative sliding velocity, h*is the characteristic film thickness, and τ*is a characteristic time of the lubricant. The procedure is exemplified by applying it for the determination of the influence of the molecular weight and concentration of the polymeric component of the lubricant on the hydrodynamic lubrication. This influence is brought about by the strong relation between the polymer properties and

ISSN:0003-3146    

DOI:10.1002/apmc.1991.051920106

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe technique of inverse gas chromatography (IGC) was used to investigate the thermodynamic miscibility (compatibility) of low molecular weight PVC‐poly(adipate ester) plasticizer mixtures. The polymer‐plasticizer thermodynamic interaction parameters were determined from chromatographic retention data for various low molecular weight volatile solutes (probes) on stationary phase mixtures which covered the entire composition range for each component. Experiments were carried out in the temperature range of 90 to 110°C. The Flory‐Huggins interaction parameter (χ+23) values were found to be dependent on the chemical nature of the probes, the temperature, and the composition of the mixed phase. The results predict a relatively high polymer‐plasticizer compatibility for a wide range of polymer‐plasticizer mixtures (up to approx. 70 wt.‐% of plasticizer). Results were also compared to our own previous data using high molecul

ISSN:0003-3146    

DOI:10.1002/apmc.1991.051920107

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe paper gives a report on the oxygen permeability in films of poly(styrene‐comaleic acid) halfesters and halfamides as well as other polymers containing carboxylic groups in comparison with commercially available glass forming polymers at room temperature. The presence of oxygen in the polymer layers was proved by the quenching of the delayed fluorescence of pyronin B. The permeability of the halfesters/halfamides (Pox= 2…7.10‐14cm2/Pa .s) corresponds to that of common polymers like poly(methyl methacrylate) (PMMA) or poly(vinyl acetate) (PVAc), and is nearly one order of magnitude higher than that of poly(acrylic acid) (PAAc), poly(styrene‐comaleic acid) (SMAc) and carboxymethylcellulose (CMC). Presumably, intramolecular hydrogen bonds in the halfester/halfamides compete successfully with the intermolecular interactions and hence cause an increase in permeability as also do bulky substituents. Addition of bases like dimethyl aminopropanol (DMAP) and dimethyl aminopropyl acrylamide (DMAPAA) decreases the permeability to about 1/40 of the initial value. The permeability is then similar to the low permeability of polymers with predominant ionic interaction sodium polyacrylate (NaPAAC), sodium carboxymethylcellulose (

ISSN:0003-3146    

DOI:10.1002/apmc.1991.051920108

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractSome polyketones were prepared from p‐xylene, chloroacetylchloride, 1,2‐dichloroethane and dichloromethane using anhydrous aluminiumtrichloride and carbon disulfide as solvent. The resins thus obtained have been characterized by IR spectra and number average molecular weight. The thermal properties have been studied by thermogravimetry and differential scanning calorimetry. All the resins were tested for their biological activity against Pseudomonas fluorescens, Bacillus subtilis and Aspergillus niger. The results show that the growth of the tested organisms can be controlled by the polyketone res

ISSN:0003-3146    

DOI:10.1002/apmc.1991.051920109

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractSpherical macroporous particles, intended for use as carrier particles in various types of column operations, were prepared by suspension and microsuspension polymerization of trimethylolpropane trimethacrylate (TRIM), in the presence of various amounts of porogenic agents (toluene or mixtures of toluene and isooctane). The texture and properties of the particles varied markedly with the amount and composition of the porogenic agent, and were also affected by the choice of suspension stabilizer. Macroporous particles were prepared, ranging in total pore volume from 0.4 to 3.6 cm3/g, and in specific surface area from 7 to>450 m2/g. All of the particles contained macropores, and except for those with very low specific surface area, contained a certain fraction of micropores (diameter<60 Å). The presence of micropores could be eliminated completely by decreasing the monomer concentration and increasing the isooctane content of the porogenic agent to 50 wt.‐%. Increasing the isooctane content also resulted in an increase in the total pore volume and a decrease in the tendency of the polymer matrix to swell in toluene. The effect on properties of particles by heat treatment at 130°C and by grafting poly(methyl methacrylate) onto the particles was also studied.The amount of unreacted double bonds of the particles could be varied by varying the polymerization temperature. The presence of easily accessible double bonds is important as they can be utilized for functionalization of the rigid macroporous partic

ISSN:0003-3146    

DOI:10.1002/apmc.1991.051920110

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY