Z. Pelzbauer

The effect of polymeric porogen on the properties of macroporous poly(glycidyl methacrylate-co-ethylene dimethacrylate)

Abstract Macroporous copolymers of glycidyl methacrylate with ethylene dimethacrylate [poly(GMA-co-EDMA)] were prepared using poly(methyl methacrylate) and polystyrene of various molecular weights as a porogen, either pure or in toluene solution. The polymeric porogen remains partly incorporated in the polymer beads. The effect of the polymeric porogen on the shape and size of the particles, porous structure and particle morphology has been studied. The fraction of the oxirane groups accessible to chemical reaction with variously bulky substrates was determined in the particles. Accessibility of the oxirane groups was characterized by the e.p.r. spin-label technique. Quaternary ammonium derivatives of poly(GMA-co-EDMA) exhibited high catalytic activity in nucleophilic substitution.

Deformation of melts of mixtures of incompatible polymers in a uniform shear field and the process of their fibrillation

Fibril formation in mixtures of incompatible polymers, in this case polyethylene and polystyrene, has been studied with their melt being deformed in a uniform shear field. It has been found that when polyethylene is present in a smaller amount, it may form very long fibrils 5 to 8 µm in diameter in the deformed mixture. The formation of such fibrils is determined by the relationship between the viscosity ratio of the mixture components and shear stress. Also, just as in the case of a nonuniform shear field in a flow through a duct, fibril formation in melts of mixtures of incompatible polymers in a uniform shear field takes place upon reaching a certain shear stress. The lower the ratio between the viscosities of the fibril-forming polymer and the other component, the lower this shear stress.

Reactive polymers : XXV. Morphology of polymeric sorbents based on glycidyl methacrylate copolymers☆

Abstract Scanning electron microscopy was used to obtain basic data on the surface and internal morphology of macroporous copolymers based on glycidyl esters of methacrylic acid which are useful as chromatographic sorbents. The basic morphological units in beads consist of spherical microparticles (globules and nodules), hundredths to tenths of a micrometre in size. On the bead surface the globules are compactly arranged in the shell, owing to the surface tension in suspension copolymerization. The pores in the shell are an order of magnitude smaller than the macropores between the aggregates of globules inside the beads. With increasing content of the crosslinking agent in copolymers, the microparticles become finer and more individualized, which explains the increase in the specific surface area of the sorbents. In gas chromatography, the morphology of the sorbent preferentially determines the retention of non-polar compounds, while that of polar compounds is affected by the chemical composition of copolymers, that is, by the content of glycidyl epoxy groups in this instance.

Investigation of the surface structure of polymers by chromatographic methods : V. Use of gel permeation chromatography in the study of the porous structure of copolymers of glycidyl methacrylate

Abstract Gel permeation chromatography (GPC) was used in an inversion function to characterize the porous structure of macroporous copolymers. Using macroporous glycidyl methacrylate copolymers as an example, the relationships between the exclusion limit in GPC and the pore size and porosity of the sorbent, the distribution coefficient and the pore geometry and size, and the peak widening and morphology of the porous structure were established. Characteristic quantities are compared with results provided by other methods, especially electron microscopy, mercury porosimetry and nitrogen sorption. It was demonstrated that the porous structures of strongly cross-linked macroporous copolymers in the swollen and dry states differ.

Effect of Rheological Properties of Compounds on Fiber Formation in Mixtures of Incompatible Polymers

Abstract Mixtures of linear polyethylene with polystyrene were used in studying the fiber formation pattern of mixtures of incompatible polymers whose melts were forced through dies. Variables included the viscosity of the components, mixture preparation conditions, and shear stress. It has been established that the process of fiber formation occurs within a definite range of shear stresses, dependent on the viscosity ratio of the fiber-forming polymer and the polymer serving as the dispersion medium. When this ratio is equal to or less than unity, mixtures containing the fiber-forming component in the form of a finely dispersed phase yields continuous fibers several micrometers in diameter within a broad range of shear stresses. At greater values of the component viscosity ratio (tens of units), no fiber formation takes place in the mixtures.

Reactive polymers. 60. glycidyl methacrylate-styrene-ethylene dimethacrylate terpolymers modified with strong-acid groups

Abstract Glycidyl methacrylate-styrene-ethylene glycol dimethacrylate (GMA-ST-EDMA) terpolymers were prepared by suspension radical polymerization. The polymer is enriched in styrene during the polymerization, and this can be explained by kinetic and thermodynamic factors operating simultaneously. The terpolymers were used in the preparation of strong-acid ion exchangers. Special attention was paid to the stability of ion exchange derivatives under the conditions of ion exchange. The GMA-EDMA copolymer, which according to its IR spectra contained sulfonate groups, was the most stable: its exchange capacity did not decrease even after one hundred exchange cycles. Modified GMA-ST-EDMA terpolymers undergo an autocatalytic hydrolysis of the polymeric matrix, which gradually dissolves.

Morphology of zone-drawn polyethylene and dependence on thermomechanical conditions of drawing

Abstract By using scanning electron microscopy and applying the methods used in ref. 8, characteristic morphologies prepared by zone-drawing of polyethylene under various thermomechanical conditions are characterized in this paper. Depending on the regime of drawing (isothermal and nonisothermal), on the temperature of the zone and on the affecting stress applied, either the mechanism of drawing by plastic deformation of the solid phase (high stress, lower temperatures), or drawing of the melt (low stresses above the melting point of the undrawn polymer) is operative. In the former case a fibrillar structure with a minor amount of interfibrillar transverse lamellae is formed. In the latter case the shish-kebab structure is obtained, which gradually becomes a structure of smooth fibrils with extremely high draw ratios (up to 150). In both cases the original spherulites are transformed into fibrils, the thickness of which depends unambiguously only on the draw ratio. At high stresses, transverse cracks arise in the samples, and the size of the cracks increases while their frequency diminishes towards the place of fracture. Fracture relaxation of the structure arising from the oriented crystallization of the melt leads to the formation of interfibrillar cavities. In structures due to the deformation of the solid phase, surface waves and kink-bands are formed. The extent of the relaxation processes is influenced by the temperature and stress of drawing and fracture.

Birefringence and orientation of polyethylene zone-drawn under various thermomechanical conditions

Abstract In this paper, the influence of deformation and thermomechanical drawing conditions on the development of birefringence and orientation in high-density polyethylene during zone drawing is described. The orientation process of the crystalline phase does not proceed uniformly with deformation and is complete at lower draw ratios, while orientation of the amorphous phase increases continuously up to the highest draw ratios. The maximum birefringence considerably exceeds that of a polyethylene crystal (as high as 0.081) and the amorphous orientation almost approaches that of the crystalline phase. This indicates that the zone-drawing technique is highly effective in producing orientation. The birefringence is affected simultaneously by drawing stress and temperature; at higher temperatures and lower stresses, softening effects predominate, while in the opposite case stiffening effects become operative. The occurrence of both factors is regulated by the time of thermal exposure in the heating zone.

Relationship between thermal shrinkage and morphology of zone-drawn polyethylene

Abstract Shrinkage was investigated in polyethylene drawn in the solid state and in the melt. The findings indicate the formation of a crystalline skeleton at draw ratios above 5–10. The skeleton raises the resistance of the drawn samples to shrinkage and its quality increases with the draw ratio. The possible structure of the skeleton is discussed. Regeneration of the drawn polymer to the isotropic state was also investigated. This was found to depend on the heating procedure; in the case of gradually increased temperature the reversibility of plastic deformation is restricted by annealing effects, while immediate melting at 150°C showed the reversibility to be substantially higher and even total recovery could be achieved. These differences are explained in terms of disturbed continuity of the stretched molecular network.

Rearrangement of the porous structure of macroporous copolymers

Abstract Changes in the porous structure of the strongly crosslinked macroporous copolymers glycidyl methacrylate-ethylene dimethacrylate and styrene-divinylbenzene were studied. Via interaction with organic solvents (dioxane, methanol) changes are brought about in the specific surface areas and pore volumes, which are interpreted in terms of changes in the microporous and macroporous domains of the porous structure of the polymers. According to mercury porosimetry, there are also changes in pore distribution. The phenomenon has also been observed in microphotographs of polymer sections obtained by electron microscopy and in the sorption of solutes.