A comprehensive investigation of rheological properties of linear and branched styrene-acrylonitrile copolymer specimens with similar molecular characteristics has been carried out. During the steady-state shear flow, the viscosity properties of both specimens are described by the Cross equation. In this case, the branched copolymer is characterized by a higher viscosity and shear thinning degree as well as by substantially lower shear rate values corresponding to transition to the non-Newtonian flow region. The elasticity of the branched copolymer melt (estimated from the value of the first normal stress difference) is considerably higher than that of the linear. This is reflected on the characteristics of occurrence of unstable flow at high shear rates. Rougher extrudate surface distortions are characteristic for the branched copolymer, and the shear rate corresponding to their occurrence is noticeably lower than for the linear copolymer. The dynamic characteristics of the copolymers being compared also attest to a greater elasticity of the branched specimen. An investigation of the viscoelastic properties in a wide temperature range allowed constructing a generalized frequency dependence of dynamic moduli encompassing various regions of the relaxation states of the copolymer specimens. Continuous relaxation spectra were calculated by means of the Mellin transform. It is shown that relaxation phenomena caused by segmental mobility doesn’t depend on the presence of branchings, whereas branching of the chain has a substantial effect on translation mobility of the chain as a whole. Branching leads to a noticeable increase of transient elongation viscosity but has almost no effect of strain hardening of the melt.

The rheological properties of 5% solutions of a fiber-forming polyamidobenzimidazole in DMAA containing LiCl additives and polyamidobenzimidazole-polysulfone blends in the same solvent have been studied. The total concentration of polymer blends with various component ratios is 5 wt %. At temperatures below ∼110°C, the systems under study behave as non-Newtonian fluids and their viscosity decreases with temperature. At T > 110°C, the temperature dependence of viscosity passes through a minimum. The position of the minimum on the temperature scale decreases with the concentration of polyamidobenzimidazole. This character of a change in viscosity is associated with the phase separation of polyamidobenzimidazole solution that leads to its gelation. The temperature corresponding to the minimum viscosity coincides with the onset temperature of a sharp turbidity of solution during heating. It is suggested that solutions containing up to 5% polyamidobenzimidazole possess an LCST. The addition of up to 50% polysulfone has almost no effect on the temperature of transition but brings about a marked decline in the viscosity of the system.

The rheological properties of aqueous solutions of poly(acrylic acid), poly(diallyldimethyldiammonium chloride), and their mixtures at 25°C have been studied. The concentrated solutions of the mixtures contain 18 wt % of both polymers taken at different ratios. The ratio of cationogenic and anionogenic groups φ varied from 0 to 0.4 is taken as a criterion for selection of mixture composition. An increase in φ, reflecting a more intense formation of polyelectrolyte complexes in solution, is accompanied by a significant rise in the low-frequency loss modulus and, especially, in the storage modulus, as well as by an increase in viscosity over the entire studied range of shear rates. This behavior may be explained by the presence of an additional spatial structure with junctions formed by interacting complementary charged groups. In the general case, the formation of poly(acrylic acid)-poly(diallyldimethyldiammonium chloride) polyelectrolyte complexes is said to take place in solution. The excess of rheological characteristics of mixture solutions over the corresponding characteristics of poly(acrylic acid) solutions is found to be the power function of parameter φ. The additional spatial network derived from polyelectrolyte complexes and occurring in solution is destroyed at lower shear stresses than is the network of intermolecular entanglements. At high shear stresses, orientational effects may cause phase separation of the systems owing to a change in the hydrophilic-hydrophobic balance between complexes of poly(acrylic acid) with poly(diallyldimethyldiammonium chloride) and water.

Rheological and mechanical properties of acrylonitrile-butadiene-styrene polymers (ABS) prepared via bulk polymerization depending on the molecular weight (Mw) of styrene-acrylonitrile copolymer (SAN) have been investigated. The tendencies of attaining the yield stress at steady-state shear flow and approaching to the “plateau” region of storage modulus at low frequencies in oscillatory tests were observed. Both these phenomena are induced by formation of the structural skeleton consisting of polybutadiene (PB) particles arranged in the SAN-matrix. Growth of Mw of SAN leads both to increase of the “plateau” value of storage modulus at low frequencies and the yield stress. This fact can be explained by the influence of Mw of SAN chains grafted onto PB particles on structure formation in ABS melts because of a redistribution of the ratio particle-particle / particle-matrix interactions. The elongational viscosity of ABS melts is a power function of Mw of SAN matrix. The power index of this function increases with the polymer straining that reflects orientation of SAN chains with their length increase. The strain-hardening index of ABS melts increases considerably with increase of SAN matrix Mw. However, it does not depend on presence of PB particles in the material. It means that the value of this index is governed by orientation effect in the SAN matrix. The impact strength of the investigated ABS samples is interrelated with rheological characteristics of ABS melts as well as Mw of SAN. The dependence of impact strength on Mw can be explained by increasing role of orientation effects of SAN chains with Mw increase in the copolymer fibrils connecting the walls of crazes formed at impact action.

Phase diagrams were constructed and comprehensive thermodynamic analysis was performed for hydroxypropyl cellulose-water and hydroxypropyl cellulose-ethanol systems with the use of the static sorption, calorimetry, cloud-point, polarization microscopy, and X-ray diffraction analysis techniques and the measurement of transmitted polarized light intensity. The concentration dependences of the enthalpy, entropy, and Gibbs energy of the formation of liquid-crystalline phases in the systems were determined. It was found that the formation of liquid-crystalline solutions of hydroxypropyl cellulose in water is associated with the energy term of interaction between the components and that in ethanol solutions is due to changes in combinatorial entropy.

A series of ABS plastics prepared by bulk polymerization was studied. The test samples contained almost equal amounts of PB but mostly differed in the molecular mass of a styrene - acrylonitrile copolymer. It was shown that the molecular mass of the copolymer strongly affects the rheological and mechanical properties of ABS plastics. An increase in molecular mass leads to a rise not only in the non- Newtonian viscosity of plastics but also in their yield point, storage modulus under periodic steady- state shear flow in the low- frequency plateau region, and impact strength. Quantitative correlations between these rheological and mechanical characteristics of the copolymers and their M-w values were established. As opposed to homophase polymer systems, a marked increase in the shear stress has no effect on viscosity in relation to the molecular mass of ABS plastics. In the case of melts, the influence of the M-w of the styrene - acrylonitrile copolymer on the rheological behavior of ABS plastics is apparently related to a change in the interaction of PB particles with the copolymer that controls the structural framework of the system. The relationship between the impact strength of the copolymer and its M-w may be explained by the fact that the latter parameter influences orientational effects in crazes that arise during steady- state shear flow of ABS plastics in the solid state.

The mechanical and rheological behavior of dynamically vulcanized PP/EPDM blends is examined and compared with those of unvulcanized blends. The effect of blend ratio and dynamic vulcanization of EPDM rubber on tensile properties and flow are investigated. The mechanical properties of the blends are strongly influenced by the blend ratio. With the increasing of EPDM content the value of yield stress in a solid state decreases with the elastomer volume fractions less than 0.45 for the unvulcanized blends. For the dynamically vulcanized blends the interval of EPDM content, at which the yield peak is seen, is rather limited below 0.25 elastomer volume fractions. it is shown that dynamic vulcanization changes the deformational behavior of PP/EPDM blends. The rheological properties of dynamically vulcanized blends depending on the ratio of the components may be similar to the properties of polymer composites containing the highly disperse structuring filler. The distinction between the rheological behavior of unvulcanized and dynamically vulcanized blends is related to differences of their structures and viscoelastic characteristics of unvulcanized and vulcanized EPDM phase.

The rheokinetics of vulcanization, compatibility, and morphology were studied for polychloroprene-polybutadiene blends. The time of the onset of gelation and the time of the completion of vulcanization were examined in relation to the blend composition by the method of small-amplitude cyclic deformation. The technique of electron-probe X-ray microanalysis was used to determine the polychloroprene-polybutadiene compatibility and the temperature-concentration position of the region of phase inversion. The effect of covulcanization and interaction at the polychloroprene/polybutadiene interface was estimated by measuring the peeling strength of vulcanized doubled rubber plates. The dependences of the kinetic parameters on the mixture were shown to be affected by the morphology of the rubber blend, the blend's partial compatibility, and the redistribution of vulcanizing components between the rubbers during vulcanization. As a result, the times of the onset and completion of vulcanization depend on the ratio of the rubbers in the blend according to different patterns.

The isotactic PP and its binary blends with an LC copolyester or polycarbonate which were crystallized from the melt under a pressure p(cr) of up to 300 MPa at a constant cooling rate of 2 K/min were studied by X-ray diffraction and DTA. The content of a gamma phase in PP was shown to increase sharply, almost in a step-wise manner, from similar to10 to similar to95%, with a rise in p(cr) from 50 to 100 MPa. If crystallization was carried out at a pressure of 100 MPa, the addition of the above-mentioned polymers to PP led to a decrease in the content of the gamma phase and an increase in the content of the gamma phase. This phenomenon was accounted for by the gamma-alpha phase transformation under the action of local stresses appearing at the PP-LC copolyester or PP-PC interface upon cooling due to a marked difference in the thermal expansion coefficients of these polymers at the temperature of crystallization of PP.

Blends of PET with a linear LC copolyester based on PET and p-hydroxybenzoic acid were studied by volume dilatometry at a pressure of 50-125 MPa, DSC, X-ray analysis, and IR spectroscopy. Melting and crystallization of the blends containing up to 75% of the LC component are similar to those of a pure PET; in this case, transition temperatures linearly increase with increasing the pressure. It was found that the temperature dependence of the thermal expansion coefficient of the blend shows several peaks within the temperature interval corresponding to the crystallization temperature T-cr of PET. As was shown, the melting temperature T-m of the samples under pressure is independent of the blend composition but, under the same conditions, Tcr decreases with increasing the concentration of LC component. After the heating-melting-cooling-crystallization cycle, both T-cr and T-m decrease with increasing the concentration of LC copolyester in the blend. When the melt of this blend is heated under pressure, the transesterification reaction between PET and the LC copolymer components leads to the accumulation of a noncrystallizable product. As the pressure is increased, T-m increases and transesterification is shifted to higher temperatures. According to data of IR spectroscopy, the rate of this P process in the melt increases.

The rheological behavior of PP blends with the ethylene-propylene-diene terpolymer (EPDM) with different compositions containing the unvulcanized elastomeric phase and the elastomeric phase vulcanized in the course of blending was studied. The relationship between the rheological properties of unvulcanized blends and their compositions qualitatively follows the general tendency known for polymer blends. However, PP blends with the cured EPDM exhibit a quite different behavior. These blends, like polymer composites containing a highly disperse solid filler, are characterized by viscosity values much higher than those of the individual polymers, as well as by the presence of the yield stress. This phenomenon manifests itself within a certain concentration range of PP-EPDM blends. The viscosity of the blends increases with increasing crosslinking degree of the rubber. The yield stress appears to be virtually independent of the crosslinking degree and increases with the content of EPDM in the blend. Distinctions in the behavior of unvulcanized and vulcanized blends are associated with a transition of the flow of viscoelastic emulsions containing PP and the unvulcanized EPDM to the flow of suspensions composed of deformable crosslinked rubber particles in the melt of PP. The vulcanization of EPDM particles denudes their flowability, and an increase in the crosslinking degree enhances their elastic modulus and reduces their flow deformability. As a consequence, the viscosity of the System as a whole increases. A change in the morphology of PP-EPDM blends induced by the vulcanization of the elastomer was examined.

The specific volume, thermal expansion coefficient a, and compressibility beta were measured in the 20-300degreesC temperature range and at pressures up to 300 MPa for polypropylene blends with a liquid-crystal copolymer of p-hydroxybenzoic acid and PET. In the solid-state region (up to similar to70degreesC) or at temperatures corresponding to the fluid state of a blend (T greater than or equal to 173degreesC), the alpha value was found to adhere to different dependences on the blend composition at high and low pressures. High pressures appeared to cause ordering in a polypropylene melt. In the intermediate temperature range, different patterns of the change in the specific volume and alpha and beta values were observed. In the region of the polypropylene melting and crystallization temperatures, alpha and increased in a nonmonotonic manner for all blend compositions (100-25% polypropylene), whereas these parameters changed insigniticantly for the LC copolyester. In this case, it might be expected that local stresses affecting the blend structure would develop in the blend upon its cooling. The temperature and pressure dependences of the specific volume for the melts of these systems can be described by the Tait equation, as well as by an expression similar to the van der Waals equation, with the parameters varying linearly with the blend composition. This finding opens new frontiers in engineering calculations on the injection molding process as applied to melts of polymer blends.

Mutual solutions of cellulose and thermotropic linear LC polymers such as poly(decamethylene terephthaloyl dioxybenzoate) and poly [oxypropyleneglycol terephthaloyl-bis(4-oxybenzoate)] in N-methylmorpholine-N-oxide were prepared for the first time. The total polymer content in solution was 20%; the cellulose : LC polymer ratio was varied from 20 : 0 to 0 : 20 with a concentration step of 1-2%. In concentrated solutions of cellulose, LC polymers, and their blends, birefringence is absent; hence, they are isotropic systems. Upon the introduction of minor amounts of LC polymers into the concentrated cellulose solution, the viscosity decreases by 3-4 times. When blend solutions with a concentration of LC polymer of 8-10% are spun in air, the formation of solidifying extrudates upon the crystallization of N-methylmorpholine-N-oxide is observed; in the as-formed extrudates, the LC polymer is distributed as thin anisodiametric inclusions with micronic dimensions. Upon the removal of N-methylmorpholine-N-oxide, the resultant extrudates are characterized by an increased strength and rigidity compared to those of cellulose extrudates.

The specific volume of LC copolymer based on p-hydroxybenzoic acid and poly(ethylene terephthalate) was Studied as a function of temperature in the range from 20 to 300 degrees C upon compression to 700 MPa. For the copolymer, two transition temperatures were detected, which are related to the activation of mobility in blocks enriched with PETP and p-hydroxybenzoic acid, respectively. The phase diagram of the copolymer versus temperature and applied pressure was constructed. It was found that the temperature and baric dependences of the coefficients of thermal expansion and compressibility increase sharply in the range of the transition temperatures and appreciably decrease with the growing pressure, especially in the region corresponding to the LC state of the copolymer. The compressibility of the LC copolymer, as well as PETP, is the increasing function of the fraction of free volume which varies with temperature or pressure. It was shown that the dependence of the specific volume of the copolymer on pressure at temperatures above 50 degrees C may be described to a good approximation by the modified van der Waals equation.

Impregnation and infiltration of fibrous materials by LC copolyester melts and the blends with viscous thermo-plastic polysulphone were quantitatively described as unsteady and steady stages in terms of rheological characteristics of the melts using an equivalent capillary model. Addition of LC polyester to viscous thermoplastic melt noticeably enhances impregnation condition. Study of the melt flow through various capillaries demonstrated a development of the melt slippage at high shear rate along the capillary walls. Slippage phenomena may be important at the initial stage of impregnation but can be neglected for final stage due to low shear rate in the last case. On the other hand, at those conditions a yield stress of the melt may considerably complicate the impregnation process due to a drastic viscosity increase.

Liquid-crystalline (LC) polymeric electrets and piezoelectrics with mesogenic groups in the backbone were synthesized and characterized. The samples were obtained on the basis of copolyesters of p-hydroxybenzoic acid with PET or with 6,2-hydroxynaphthoic acid. It is demonstrated that these polymers provide the obtaining of highly stable electrets and piezoelements with a piezoelectric modulus of 15-2 pC/N. Piezoelectrics made of a polymer based on 6,2-hydroxynaphthoic acid are superior to the piezoelectrics made of the PET-based copolyester with respect to time stability and working temperature interval.

Using blends of poly(4-methyl-1-pentene) and the LC copolyester of hydroxybenzoic acid with PET as a model, a comparative study of the specific features of their flow through cylindrical capillaries and fibrous materials was performed. Addition of the LC copolyester to poly(4-methyl-1-pentene) considerably decreases the viscosity. Examination of the flow of the blends through capillaries of different radii showed that this effect is due to the slipping of the blend along the capillary walls and in the bulk at the interface. An increase in the amount of the LC copolyester in the blend considerably accelerates impregnation of a nonwoven fabric, thus facilitating the forming of polymer fiber composites. The flow velocity of polymer blends through a fibrous material can be described, in a good approximation, in terms of the viscosity characteristics of a blend. In this case, a fibrous material is represented as a system of equivalent capillaries, and such quantities as porosity and permeability are used as the basic characteristics of the material. The addition of even small amounts of the LC copolyester to poly(4-methyl-1-pentene) (as a binder) was found to enhance some mechanical properties of the fiber composites.