摘要:

AbstractThe commercially available poly(vinyl alcohol) (PVA) and poly(vinyl acetate) (PVAc) were fractionated by precipitation to give nine and six fractions respectively. The dependence of the thermal stability of the polymer on the molecular weight of the samples was investigated by dynamic thermogravimetry in air. The percentage decomposition temperature, integral procedural decomposition temperature, and activation energy measurements revealed that the stability of PVAc was directly proportional to the molecular weight of the sample. In PVA, there was an optimum polymer size where the stability was at a maximum, and it decreased on increasing or decreasing the molecular weights.

ISSN:0003-3146    

DOI:10.1002/apmc.1975.050460101

出版商:Hüthig&Wepf Verlag    

年代:1975

数据来源: WILEY

摘要:

AbstractThe thermal degradation of poly(vinyl acetate) in ethyl benzoate, benzyl benzoate, and ethyl salicylate was investigated in an atmosphere of nitrogen in the temperature range 189−212°C. The degradation was followed by titrating the evolved acid and recording the absorption spectra of the degraded polymer solution. The degradation was influenced by the solvents, and was higher in ethyl salicylate than in other solvents. A broad absorption band was observed in benzyl benzoate and ethyl benzoate while in ethyl salicylate peaks at 367, 390, 412, and 435 nm were observed. Polyenes with a smaller number of double bonds were more predominant than polyenes having more than 10 double bonds. The activation energy varied between 11−15 kcal/mol in these solvents. The results have been explained by proposing the participation of solvents in the degradation react

ISSN:0003-3146    

DOI:10.1002/apmc.1975.050460102

出版商:Hüthig&Wepf Verlag    

年代:1975

数据来源: WILEY

摘要:

AbstractVersuche mit feinkörnigen Pulvern, bestehend aus Kieselgel, Kaolinitverbindungen und Calciumcarbonat, wurden durchgeführt, um zu prüfen, ob mit Hilfe der60Co‐γ‐Vorbestrahlungsmethode die Oberflächenpfropfung mit Methylmethacrylat (MMA) und Styrol gelingt. Es zeigte sich, daß nennenswerte Mengen Polymeres aufgepropft werden können. Der Pfropfungsgrad (PG) steigt mit zunehmender absorbierter Dosis an und strebt bei höheren Dosen einem Sättigungswert (PGmax) zu. Die gemessenen Werte von PGFmax(in g Polymeres/m2Pulveroberfläche) sind für alle Substanzen größenordnungsmäßig gleich. Daraus wird geschlossen, daß die Polymerisation durch aktive Zentren ausgelöst wird, die sich an der Oberfläche der Pulverpartikeln befinden, und daß die an der Oberfläche maximal erreichbare Konzentration an aktiven Zentren ungefähr gleich groß ist. Unterschiede in den PGFmax‐Werten der einzelnen Substanzen sind vermutlich darauf zurückzuführen, daß die verschiedenen gepfropften Pulver einen unterschiedlich großen Anteil an nicht kovalent gebundenen und trotzdem nicht extrahierbaren Polymeren enthalten, der sich in engen Poren befindet. Hinweise dafür ergab die durch AIBN thermisch ausgelöste Polymerisation von MMA in Gegenwart von porenreichem Kieselgel, die zu PGF=2 × 10−4g Polymeres m2führte. Mit der Vorbestrahlungsmethode wurde PGFmax= 8 × 10−4g Polymeres/m2erhalten. Es wird vermutet, daß das nach der Vorbestrahlungsmethode aufgepfropfte Polymere zumindest zum Teil nicht kovalent gebunden ist. Der Anteil des nicht kovalent gebundenen und nicht extrahierbaren Polymeren sollte eine Funktion der Anzahl und der Größe der Po

ISSN:0003-3146    

DOI:10.1002/apmc.1975.050460103

出版商:Hüthig&Wepf Verlag    

年代:1975

数据来源: WILEY

摘要:

AbstractPoly(vinyl propionate) was found to form a weak iodine‐complex in an aqueous solution of potassium iodide. The complex was colorless under usual conditions differing from the poly(vinyl acetate)iodine complex which had a red‐violet colour. Random and block copolymers of vinyl acetate (VAc) and vinyl propionate (VPr) also formed colored iodine complexes. The maximum absorption wave‐length (λmax) of the complex shifted to shorter wave‐lengths with decrease in the VAc‐fraction of copolymers and to longer wave‐lengths with increase in the concentration of added iodine. This shift of λmaxwas discussed in connection with the chain length of the polyiodine in the complex.The molar absorption coefficient (ϵmax) of the complex (defined as absorbance per bound iodine molecule) depended remarkably upon the polymer composition. The dependence of ϵmaxupon the copolymer composition could be explained by the assumption that the complex consists of two different parts, a strongly colored and a wea

ISSN:0003-3146    

DOI:10.1002/apmc.1975.050460104

出版商:Hüthig&Wepf Verlag    

年代:1975

数据来源: WILEY

摘要:

AbstractThis paper presents the mechanical behavior and the molecular arrangement of the carbon‐black filled SBR under uni‐ and biaxial stretching. The stress of filled SBR, estimated from the stress‐temperature experiment under uniaxial stretching, changed from the entropy component to the internal energy component with the concentration of carbon black. Under biaxial stretching the stress is composed of an internal energy contribution from a low load of black. The structural change of the rubber was observed by the X‐ray diffraction and the electron microscope. The stretching of SBR produces the oriented, densely packed pseudocrystalline regions and thin molecular regions. Under biaxial stretching the rubber chains orient parallel to the film and the stream of the densely packed layers is o

ISSN:0003-3146    

DOI:10.1002/apmc.1975.050460105

出版商:Hüthig&Wepf Verlag    

年代:1975

数据来源: WILEY

摘要:

AbstractCyclophosphazene oligomers (I) have been formed by heating tetrabutoxydianilinocyclophosphazene and dichlorodiphenylsilane at temperatures between 100°C to 160°C. These oligomers are soluble in most organic solvents. Molecular weights and softening points of (I) are in the range of 1700 to 37000 and 95°C to 180°C. Molecular weights and softening points of cyclophosphazene polymers (II) obtained by reheating of (I) at 190°C are about 3000 to 180000 and about 78°C to over 300°C. The thermal decomposition of the polymers (II) occurs in the range from 100°C to 300°C. It is shown by thermogravimetry that the weight loss of the thermally most stable polymer of (II) is about 15% in air

ISSN:0003-3146    

DOI:10.1002/apmc.1975.050460106

出版商:Hüthig&Wepf Verlag    

年代:1975

数据来源: WILEY

摘要:

AbstractPolyphosphonylureas were prepared from the condensation of phenylphosphonic diisocynate with secondary and primary diamines employing the interfacial technique. The thermal properties of the products were studied by differential scanning calorimetry and thermal gravimetric analysis. In air the products undergo thermal oxidative degradation at temperatures greater than 300°C. The products undergo identical thermal degradation at temperatures less than 300°C in both air and N2. The products show significantly better thermal stability than their carbon counterpart

ISSN:0003-3146    

DOI:10.1002/apmc.1975.050460107

出版商:Hüthig&Wepf Verlag    

年代:1975

数据来源: WILEY

摘要:

AbstractA commercial PVC and another one prepared in bulk at 40°C were fractionated by means of fractional solution method using cyclohexanone‐methanol mixtures. Both fractionations resulted in two sets of fractions. Their thermal degradation at 175, 180 and 185°C was followed by means of a conductivity cell which allows a continuous titration of the evolved HCl. The results showed that the lower the molecular weight the higher the degradation rate was; nevertheless, this relationship is only valid up to molecular weights of 60 000 to 90 000, from which the degradation rate appeared to be independent on the molecular weight. The UV‐visible spectra of the degraded polymers suggest a similar polyene sequence distribution for all the fractions which accounts for a similar mechanism of degradation in contrast to what happens to fractions with different tact

ISSN:0003-3146    

DOI:10.1002/apmc.1975.050460108

出版商:Hüthig&Wepf Verlag    

年代:1975

数据来源: WILEY

摘要:

AbstractThe kinetic and thermal parameters for the decomposition of a group of polymerization initiators were determined using differential scanning calorimetry (DSC). The solvent was di‐n‐butylphthalate, and the measurements were made in the temperature range between 50°C and 180°C. The activation energies for azobisisobutyronitrile and benzoyl peroxide are 137.5 kJ/mol (32.9 kcal/mol) and 119.6 kJ/mol (28.6 kcal/mol), respectively, which is in agreement with literature values. The activation energies for technical lauroyl peroxide and technical methylethylketone peroxide are 141.7 kJ/mol (33.9 kcal/mol) and 181.4 kJ/mol (43.4 kcal/mol), respectively, and are higher than the values reported in the literature. This is probably due to the fact that technical samples were used.The heats of decomposition were also obtained. They are − 230.7 kJ/mol ( − 55.2 kcal/mol) for azobisisobutyronitrile, − 293.0 kJ/mol ( − 70.1 kcal/mol) for benzoyl peroxide, − 693.5 J/g ( − 165.9 cal/g) for lauroyl peroxide, and −459.8 J/g ( − 110.0 cal/g) for methy

ISSN:0003-3146    

DOI:10.1002/apmc.1975.050460109

出版商:Hüthig&Wepf Verlag    

年代:1975

数据来源: WILEY

摘要:

AbstractEs wurde der Verlauf des Einbaus von 6‐Caprolactam und 8‐Capryllactam in die Polymerketten bei der hydrolytischen, kationischen und anionischen Copolymerisation bei äquimolaren Mengen der angeführten Monomeren verfolgt. Bei der hydrolytischen Copolymerisation im Temperaturbereich von 200−260°C wird am Anfang der Polymerisation 6‐Caprolactam schneller in die Ketten eingebaut. Mit sinkender Temperatur nimmt die Gesamtgeschwindigkeit der Copolymerisation ab, und der Unterschied zwischen den Einbaugeschwindigkeiten der Lactame steigt an. Demgegenüber wird in der Anfangsphase der kationischen Copolymerisation 8‐Capryllactam größenordnungsmäßig schneller eingebaut, und die Veränderungen in der Zusammensetzung der Copolymeren sind nicht von der Temperatur abhängig.Bei der anionischen Copolymerisation werden unter den untersuchten Bedingungen beide Lactame mit gleicher Geschwindigkeit in die Polymerketten eingebaut.Den angeführten Unterschieden beim Einbau der einzelnen Monomeren in die Copolymerketten bei unterschiedlichem Mechanismus entsprechen die Schmelztemperaturen der in den verschiedenen Phasen der Copolymerisation

ISSN:0003-3146    

DOI:10.1002/apmc.1975.050460110

出版商:Hüthig&Wepf Verlag    

年代:1975

数据来源: WILEY