Yu.S. Lipatov

Crystallization of filled Nylon 6 II. Isothermal crystallization

SummaryIsothermal crystallization kinetics from the melt of nylon 6 containing various amounts of untreated glass beads and Aerosil (series GB and A) and aminosilane-treated glass beads (series GBA) was studied by DSC method. Treatment of experimental data in terms of Kolmogorov-Avrami equation has shown that time exponentn is relatively insensitive to presence of GBA filler, whereas it was found to decrease gradually with increasing filler content in samples of GB and A series to value as low as 0.5 for sample A–67. Nucleation free energy was the same in pure nylon 6 and filled samples of GBA series, but dropped suddenly in samples of GB series when mean interparticle separation x decreased below “critical” value ξcrit =(5–10) x 10−6 m. Taking into account the concomitant drop of equilibrium melting temperature, it was concluded that these effects are a consequence of specific structural change in polymer phase accompanying transition into a “boundary state”. Temperature dependence of polyer crystallization rate in highly filled samples of A series at small supercoolings was found to obey them=4 law, which is characteristic of transformations in strained media. Experimental data seem to be consistent with the idea that the postulated strain energy might originate from negative capillary pressure between high-surface energy solid particles wette d by polymer melt. Quantitative analysis of overall crystallization rate dependence on interparticle distance x has shown that ξcrit may be identified with change of growth morphology from a three-dimensional to a two-dimensional one, while slowing down of growth rate at lower values of ξ was attributed to increase of nucleation free energy due to increasing contribution from capillary forces.

X-ray diffraction studies on liquid crystalline order in vinyl polymers with mesogenic side-groups

Abstract X-ray studies on some vinyl polymers with azobenzene sidegroups were performed. A model of layered structure rearrangement resulting from the substitution of the methacrylate main chain for the acrylate is proposed. It has been shown that the perfection of a layered structure is reduced with shortening of the flexible tail of the mesogenic group. Improvement of LC order with increase of temperature was revealed.

Influence of solid surface on equilibria in polymer mixtures

Abstract The influence of solid disperse particles (aerosil) on phase equilibria in ternary (polymer-polymer-solvent) and binary (polymer-polymer) systems has been investigated using adsorption and gas chromatography techniques. The change in position and shape of the binodal for the ternary systems has been established. The region of thermodynamic compatibility of two polymers in a common solvent is broadened due to the selective adsorption of high molecular weight fraction of one of the polymers, this effect being dependent on the amount of solid particles introduced into the system. For binary systems, the thermodynamic interaction parameters χ 23 have been determined and increasing thermodynamic stability of the mixture in the presence of the solid phase has been discovered. The complicated dependences of the interaction parameters on mixture composition are connected with differences in selectivity of adsorption for various compositions. It is supposed that increased thermodynamic stability of a mixture of two incompatible polymers in the presence of solid is due to the transition of both polymers into adsorption and border layers.

Interfacial effects in polymer blends review

Interfacial effects at the boundary between two incompatible polymers and the mechanism of formation of a transitional layer at the interface, are discussed from the point of view of the concept of thermodynamic incompatibility of polymers in blends, taking into account some colloid chemical views. It is shown that the structure of the interfacial, transitional layer is dependent on the conditions of preparation of the mixtures and is controlled by thermodynamic and colloid chamical factors. The types of transitional regions are classified according to their mechanism of formation, thermodynamic and colloid chamical properties and morphology.

Effect of silane treatment of fillers in polyethylene-kaolin compositions☆

Abstract The paper presents results showing the change in bend strength, specific impact toughness and shear modulus as a function of the concentration, in high density polyethylene, of a filler (kaolin) modified by silanes. It is shown that the change in mechanical characteristics is accompanied by morphological changes in the polyethylene in the volume and at the filler surface. Explanations are given for the results obtained.

Studies on one-dimensional order in smectic polymers. Analysis of small-angle x-ray scattering and correlation functions

Abstract The absolute intensity of small-angle X-ray scattering for smectic polymeric liquid crystals with mesogenic side-groups has been analysed. The distribution of electron density in a layer and the correlation functions for the system of layers have been obtained. It is demonstrated that the phase structure of polymers is heterogeneous and may be presented as “layered packs”.

The swelling of filled styrene-divinylbenzene copolymers☆

IT IS now known that the addition of fillers to polymers, especially rubbers, results in additional network formation. In our earlier studies [1-3] we examined the effect of a filler on structure formation in thermoplastic polymers. Study of the special features of structure formation in the case where formation of the polymer takes place simultaneously with formation of the final material is of great interest. Investigation of the conditions of formation of a crosslinked polymer in the presence of a filler would be of great value, particularly to the production of reinforced plastics. We have previously shown that the structure of a linear polymer formed in the presence of a glass surface differs from the structure of the polymer produced in the absence of a filler [4, 5]. The aim of the present work was to discover some of the specific features of formation of a crosslinked polymer in the presence of glass powder of small particle size. A number of papers has been concerned with the s tudy of polymer networks formed in the presence of a filler [6-11]. The materials studied in these papers were exclusively vulcanizates of natural and synthetic rubbers--butadienestyrene, polyurethane etc. In these studies the kinetic theory of elasticity and the F lory-Rehner theory of swelling [12] formed the basis for investigation of the behaviour of the networks in the presence of a filler. By making use of the well known equation of the latter theory, and making a number of assumptions, it is possible to arrive at an estimate of the number of crosslink points in the network of the filled vulcanizate, and thus to estimate the number of additional points of crosslinking due to polymer-filler interaction. I t seemed of interest to apply the theory of the swelling of filled vulcanizates to the swelling of filled, erosslinked polymers that are not in the high-elastic state under the experimental conditions.

Investigation of microphase separation occurring in interpenetrating polymeric networks prepared from polyurethane and styrene-divinylbenzene copolymer☆

Abstract Interpenetrating polymeric networks based on polyurethane and styrene-divinylbenzene copolymer have been prepared. The heterogeneous structure of the networks has been investigated by the methods of small- and wide-angle X-ray scattering. The extent of heterogeneity domains has been calculated and the transitional layer thickness obtained, using the experimental data, and in addition the diffusivity of phase boundaries and the degree of segregation of the components have been determined as well as the molecular level of mixing of the components. It is shown that the degree of microphase separation of components in the interpenetrating polymeric networks depends on the amount of the second component in the system.

Packing density of the chains in the boundary layers of polymers

Abstract The molecular probe method of investigation was used to analyse the packing density of polymer molecules in high polymer boundary layers that are formed at the solid-polymer interface. The complex structure of the boundary layers was found to consist of successive regions differing as to the packing density of the boundary layer (thickness 2–4 μ) and the transitional layer (thickness 30–60 μ). The structure of the boundary and its thickness for each of the studied polymers depend both on the flexibility of the polymer chains and on the cohesive energy density.

Methods of investigation study of the compatibility of oligomers and polymers by gas chromatography

Abstract A chromatographic method is proposed to determine the compatibility of polymers by measuring excess free energy, enthalpy and entropy of mixing. The method is used to determine several mixtures: polystyrene with polyethylene glycol and polyethylene glycol adipate and several oligomer systems. Compatibility with different component ratios in the mixture was studied for a polystyrene-polyethylene glycol adipate system. It was shown that polystyrene does not mix with both polymers in the temperature range studied. Variations of thermodynamic parameters of oligomer mixtures are similar to those of polymer mixtures.