Studies on miscibility in homopolymer/ random copolymer blends by equation of state theory

The miscibility of poly(methyl methacrylate) (PMMA) and styrene-acrylonitrile random copolymers (SAN) blends was investigated on the basis of the Flory—Orwoll—Vrij equation of state theory. To obtain the equation of state parameters (P*, V*_sp, T*: characteristic parameters), the pressure—volume—temperature (PVT) behaviour was measured for PMMA and a series of SANs with various acrylonitrile contents. The exchange energy parameter X_ij was also calculated by fitting the theory to some phase diagrams of PMMA/SAN blends. The Flory—Huggins interaction parameter χ was separated into two contributions based on the equation of state theory for mixtures: the exchange energy term χ_inter and the free volume term χ_free. Both the temperature and copolymer composition dependences of χ_inter and χ_free were estimated by calculations using the equation of state parameters. There exists a region in which χ_inter is negative, leading to a miscibility window in PMMA/SAN blends. However, the immiscibility at high temperatures in the blends cannot be explained only by χ_inter; it is caused by the free volume contribution, χ_free. The miscibility window behaviour in PMMA/SAN blends may be explained within the framework of the equation of state theory.     

Das spezifische Brechungsinkrement eines statistischen Methylmethacrylat/Benzylacrylat/Styrol-Terpolymeren

The specific refractive index increments of a random methylmethacrylate/ benzylacrylate/styrene-terpolymer and of the three corresponding homopolymers was measured in several solvents and at six different wavelengths. With the known terpolymer composition and the specific refractive index increments of the homopolymers the specific refractive index increment of the terpolymer is calculated by means of an equation formerly derived. Calculated and experimental values are compared.     

Zur kinetik der acrylnitril-polymerisation

The heterogeneous bulk polymerization of acrylonitrile initiated by AIBN has been studied by means of an improved dilatometric technique and a new method of analysis, where the initial reaction rate (v_w)₀ results from the intercept of a straight line in a \documentclass{article}\pagestyle{empty}\begin{document}$ \frac {\ln \left( 1 \hbox{---} {\rm U} \right)} {{\rm e}^{{- 0,5} {\rm k}_{\rm s}{\rm t} \hbox{---} 1}}$\end{document} versus t plot. It has been found that the initial reaction rate is proportional to the square root of the initial catalyst concentration S₀. The ratio of the rate coefficients of propagation and termination\documentclass{article}\pagestyle{empty}\begin{document}$\frac { {\rm k}_{\rm a} } { {\rm k}_{ {\rm w}^{2} } } $\end{document} could be calculated from the slope of a straight line passing through the origin in a plot of (v_w)₀ versus \documentclass{article}\pagestyle{empty}\begin{document}$\sqrt { {\rm S}_{0} }$\end{document} and yielded a value of 280 mol 1^?1.     

Messung der Selbstdiffusion im System Polystyrol-Benzol; Temperatur-, Konzentrations- und Molekulargewichtsabhängigkeit

Self-diffusion of benzene and polystyrene in the system benzene-polystyrene is studied by means of spin-echo-technique as function of temperature, concentration and polymer molecular weight. From the dependence of temperature the activation energies are calculated as function of concentration and molecular weight. The concentration dependence is discussed in terms of restricted diffusion and the Fujita Free-Volume-Theory. The computed free volume shows a significant maximum at 50°C. This effect may be attributed to a change in the mobility of the phenyl side groups of polystyrene and is vanishing with decreasing molecular weight. The free-volume-temperature curves are giving references to the glass transition.     

13C- and 23Na-NMR investigations on alkali cellulose

Summary Solid state ²³Na- and ¹³C-NMR spectra of alkali cellulose are presented as a function of NaOH-concentration of the steeping lye, steeping temperature and amount of adhering lye (press factor). Results are discussed with regard to chemical binding of NaOH to the cellulose chain in the system cellulose/ NaOH/H₂O.Presented at the 22nd Microsymposium, Characterization of Structure and Dynamics of Macromolecular Systems by NMR Methods, Prague, CSSR, July 20–23,1981     

Quantifying the evolution of TTCN-3 as a language

Ten years of maintenance, nine published revisions of the standards for the Testing and Test Control Notation version 3 (TTCN-3), more than 500 change requests since 2006, and 10 years of activity on the official TTCN-3 mailing list add up to a rich history, not unlike that of many successful Open Source Software (OSS) projects. In this article, we contemplate TTCN-3 in the context of software evolution and examine its history quantitatively. We mined the changes in the textual content of the standards, the data in change requests from the past 5 years, and the mailing list archives from the past 10 years. In addition, to characterize the use of the TTCN-3 we investigated the meta-data of the contributions at the TTCN-3 User Conference, and the use of language constructs in a large-scale TTCN-3 test suite. Based on these data sets, we first analyze the amount, density, and location of changes within the different parts of the standard. Then, we analyze the activity and focus of the user community and the maintenance team in both the change request management system and the official TTCN-3 mailing list. Finally, we analyze the distribution of contributions at the TTCN-3 User Conference across different topics over the past 8 years and construct use anomalies during the development of a large-scale test suite. Our findings indicate that the TTCN-3 is becoming increasingly stable as the overall change density and intensity, as well as the number of change requests are decreasing, despite the monotonous increase in the size of the standards.     

Zur oligomerenbildung bei der thermischen polymerisation von styrol

It is shown that in thermal polymerization of styrene four dimers and six trimers are formed by parallel occurring oligomerization reactions. With increasing temperature the rate of oligomerization increases more rapidly than the rate of polymerization. The relativ yields of the different oligomers depend on temperature, too.     

Struktur und eigenschaften von ABS-polymeren. IX. Quantitative untersuchungen zur morphologie von ABS-polymerisaten

The technological properties of ABS polymers largely depend on the structure of the elastomer phase as well as on the elastomer/thermoplast interface. The morphological structure of such polymers can be determined from electron micrographs of ultramicrotome sections – after selective contrasting of the polybutadiene phase – or of replicas of fracture surfaces after selective chemical degradation. The various ABS polymers are classified by their manufacturing processes and their morphologies and characterized by electron micrographs. The degree and place of grafting are of particular importance. The quantitative determination of the surface- and internal grafting is achieved by combining the determination of the degree of grafting (extraction), the evaluation of the results obtained on particle counting, and a morphometric process. It is demonstrated that the morphometric process can in general be applied for the quantitative determination of the contrastable component in two-phase polymers.     

Das Verhalten organischer Pigmente in Polymeren

The importance of colouring matter is of prime importance in the plastics industry. The individual behaviour of organic pigments in the various polymer materials necessitates, however, on the part of the plastics manufacturer a precise knowledge of ?which pigment for which plastic”?. For example, a well known Thioindigo pigment behaves very differently in various polymer materials : In polystyrene, depending on the concentration used, it is monomolecularly dissolved, in associated solution or present as undissolved particles. In PVC, however, the good migration fastness is indicative of the insolubility of the pigment in this medium and so it is not surprising that PVC is the ideal plastic medium for this pigment. The behaviour of organic pigments in polymers is largely a function of molecular structure, e. g. intermolecular H-bonds can cause a decrease in solubility of a pigment in a polymer material, which in turn results in improved migration fastness. This is demonstrated by the improved migration fastness of variously substituted β-hydroxy naphthoic acid arylamide derivatives. Many phenomena exist however, which as yet can only be explained on the basis of the crystal structure of the pigment particles, i. e. the presence of aggregates or agglomerates. Such a phenomenon is, for example, the dispersibility of pigments in polymers. Here pigment surface, wettability by polymer and intermolecular forces are all of importance. In general, the dispersibility is better the smaller the specific surface area, as is shown for a typical quinacridone pigment. The influence of the rate of wetting on dispersibility is demonstrated using polyethylene wax. A further effect, which demonstrates the intermolecular forces between pigment and polymer, is the way in which certain pigments influence the rate of crystallization of partly crystalline polymers. This itself is connected with the shape and size of the pigment particles embedded in the polymer material. Such effects are demonstrated by measurements on various polyethylene objects. The pigment in this case was a naphthalene tetra carbonic acid derivative in both cis and trans form with widely varying specific surface areas.