Improvement of the deformative characteristics of poly-β-hydroxybutyrate by plasticization

Plasticized systems of poly--hydroxybutyrate (PHB) are studied, where low-molecular compounds traditionally used for this purpose for various systems, i.e., dioctyl sebacate, dibutyl sebacate, polyethylene glycol, Laprol 503, and Laprol 5003, are used as plasticizers. All of them are nontoxic and biodegradable compounds with a similar molecular weight and comparable polarity of molecules. The main purpose of this study is to improve the deformability of PHB taking into account the structural changes in plasticized PHBs. The plasticizers chosen are completely compatible with the polymer and form a monophase system up to a plasticizer content of 15–20%. An increase in the plasticizer content allows us to increase efficiently the deformability of the polymer (the relative breaking elongation of PHB at room temperature grows up to 250–300%). At the same time, the system becomes considerably weaker and therefore there is no point in increasing the concentration of plasticizers by more than 20 wt.%. According to the data obtained from DSC measurements, the ratio between the amorphous and crystalline regions of PHB in the presence of plasticizers mentioned remains practically constant. The changes in the elastic properties of PHB/low-molecular plasticizer systems are mainly due to efficient weakening of intermolecular interactions in the amorphous regions of the polymer. A slight decrease in the crystalline order of PHB is of secondary importance.Institute of Polymer Materials, Riga Technical University, Riga, LV-1048, Latvia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 4, pp. 527–538, July–August, 1999.     

Effect of fillers on the hardness and structural order of polymers

The effect of various finely dispersed filler particles differing in size, structure, and the chemical nature of the surface, on the hardness of one crystalline (polycaproamide) and two amorphous (polystyrene and polymethylmethacrylate) polymers has been experimentally investigated. The observed changes in hardness are related with a change in the structural order of the polymer under the influence of the filler and with the formation of structures of different strength by the fillers in the polymer.Kiev Shevchenko State University. Translated from Mekhanika Polimerov, Vol. 4, No. 6, pp. 1077–1081, November–December, 1968.     

Contribution to the theory of the elastic properties of amorphous-crystalline polymers

The elastic constants of an amorphous-crystalline polymer are calculated from the known values of the elastic constants of its amorphous and crystalline components.Moscow Lenin Pedagogical Institute, Problem Laboratory of Polymer Physics. Translated from Mekhanika Polimerov, Vol. 5, No. 2, pp. 213–218, March–April, 1969.     

Molecular mechanism of oriented crystalline polymers

It is shown with reference to linear polyethylene that the deformation of an oriented crystalline polymer takes place as a result of elongation of the coiled parts of the macromolecules in the amorphous zones owing to conversion of gauche into extended trans isomers. The decrease in coiled isomer content when the specimen is deformed by approximately 5% is accompanied by a small number of chemical bond breakages. Repeat deformation by the same amount does not result in any additional breakage of polymer chains.A. F. Ioffe Physicotechnical Institute, Academy of Sciences of The USSR, Leningrad. Translated from Mekhanika Polimerov, No. 4, pp. 584–588, July–August, 1973.     

Acoustic determination of molecular orientation in polymers

On the basis of the results of measurements of the ultrasonic propagation velocity in polyethylene terephthalate fibers it is shown that the Moseley formula is suitable for determining the molecular orientation of both amorphous and amorphouscrystalline polymers. The dependence of the molecular orientation factor of amorphous and crystalline specimens of polyethylene terephthalate on the draw temperature and draw ratio is investigated. The effect of polymer orientation on the ultrasonic shear-wave velocity in the fiber is studied.Kiev Branch, All-Union Scientific-Research Institute of Artificial Fibers. Translated from Mekhanika Polimerov, No. 1, pp. 26–34, January–February, 1976.     

Mechanics of the static tension of a through chain in amorphous crystalline polymers

The displacements and tensions of the points on a through chain lying inside one crystallite of an oriented amorphous crystalline polymer are analyzed theoretically for various degrees of withdrawal of the chain from the crystallite. The tension of the chain in the amorphous region is examined as a function of its contour length and the length of the amorphous region. The nature and efficiency of the stoppers (obstacles) retaining the through chain inside the crystallites are considered. Specific results are calculated for polyethylene and polypropylene.A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 5, pp. 771–778, September–October, 1973.     

Cold flow and melting of plastics under severe friction conditions

Dry friction of a series of crystalline polymers (polypropylene, nylon, PTFE) against steel over a wide range of sliding velocities (4.4–4.4×10^–4 cm/sec) and loads (P=7.5–360 kg) with almost complete mutual overlap of the friction surfaces is studied. It is shown that friction of polymer materials against steel may be accompanied by melting of the crystalline polymer (at high velocities) or cold flow (at low velocities) in the surface layers associated with an orientation effect and the appearance of anisotropy.Mekhanika Polimerov, Vol. 1, No. 5, pp. 95–100, 1965     

Investigation of the energy effects accompanying the elastic deformation of uniaxially oriented crystalline polymers

The energy (thermal and mechanical) effects accompanying the elastic deformation of uniaxially oriented crystalline polymers have been investigated; it has been established that, when these polymers are stretched, heat is released. It is shown that the heat release in uniaxial tension is a consequence of localization of the elastic deformation in the poorly ordered regions of the polymer. The relation between the thermoelasticity of uniaxially oriented crystalline polymers and their supermolecular structure is examined.Institute of Heteroorganic Compounds, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 5, pp. 785–798, September–October, 1970.     

Changes in the structure of polymeric materials in a magnetic field

It is shown that the action of a magnetic field leads to a change in the supermolecular structure of crystalline polymers. The creation of an oriented state in amorphous thermoplastics and thermosets is accompanied by an increase in their hardness and the homogeneity of the structural state.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, pp. 737–739, July–August, 1973.     

Effect of orientation and molecular weight on the modulus of elasticity of polymer materials

The modulus of elasticity of a perfectly crystalline polymer is calculated as a function of the orientation of the crystallites. The calculations are based on the mechanics of a micro-inhomogeneous continuum. The dependence of the modulus of elasticity on crystallite orientation and molecular weight is calculated with reference to the example of crystalline kapron.Moscow-Lenin Pedagogical Institute. Problem Laboratory of Polymer Physics. Translated from Mekhanika Polimerov, Vol. 4, No. 6, pp. 1002–1007, November–December, 1968.     

Limiting stretch ratios of polymers. Role of molecular mobility

Orientation stretching stops before the polymer chains reach full orientation. The reason for the cessation of stretching in linear polymers is considered to be the decreased kinetic flexibility of the macromolecules. With Kapron as an example, it has been demonstrated, using NMR, that on attainment of the limiting stretch ratio under the action of the stretching (orienting) forces, segmental motion in the amorphous regions is almost completely stopped: the amorphous regions are glassy at any orientation temperature, even those close to the melting point of the crystals. The orientation process stops because the polymer under load behaves like a rigid body devoid of rubber-like elasticity.A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, Vol. 9, No. 3, pp. 387–391, 1973.     

Internal stresses in crystallizing polymer coatings

The effect of crystalline structure on the internal stresses in polyethylene coatings has been studied. An equation for the internal stresses in crystallizing polymer coatings has been derived. The important role of orientation processes is demonstrated.Leningrad Lensovet Technological Institute. Translated from Mekhanika Polimerov, Vol. 4, No. 6, pp. 992–996, November–December, 1968.     

Elasticity of the crystal lattice of polyethylene terephthalate

The elasticity of the crystal lattice of polyethylene terephthalate was studied along and across the axes of the polymer molecules. The elastic modulus across the chains depended on the degree of crystallinity and the interplane distances in the directions of thea and b parameters of the unit cell. The nature of the elastic deformation in the crystal lattice was analyzed, and its elastic modulus along and across the axes of the chains was calculated. On loading biaxially oriented amorphous-crystalline polymers with a tensile stress applied in the direction of one of the orientation axes of the polymer, the stresses in the crystallites oriented along and across the external applied force and the amorphous regions in series with them were equal to the stress in the sample averaged over the cross section.Deceased.Translated from Mekhanika Polimerov, No. 6, pp. 982–986, November–December, 1972.     

Strengthening of Polypropylene Strips by Orientational Stretching in Liquids

Data on the orientational stretching of polypropylene strips in process liquids serving as plasticizers of polypropylene are presented. Such a stretching allows one to avoid many complications characteristic of stretching in air and to increase the maximum stretch ratio significantly (up to 15). The stretching of strips is accompanied by changes in the crystalline structure of polypropylene and by transformation of the amorphous phase into a crystalline one. It is established that the specific strength of the orientationally stretched strips as a function of stretch ratio has a maximum. This is caused by the competing processes of macromolecule orientation in the stretching direction and the destruction of molecular bonds, which leads to the origination of microdamages in the strip surface layer and to a growing content of amorphous phase. It is shown that the extraction of process liquids from the stretched strips increases their specific strength by 20–30%.__________Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 2, pp. 251–264, March–April, 2005.     

Elasticity and strength of nonoriented partially crystalline polymers

The dependence of the elastic modulus and strength on the crystallinity and temperature was studied. During the analysis of the strength data, the nonoriented crystalline polymers can be regarded as compositions consisting of a compliant matrix (amorphous phase) and a more rigid reinforcement (crystalline phase).The A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 6, pp. 964–968, November–December, 1975.     

Mechanical relaxation processes in polymers

The various kinetic processes are classified and the place of relaxation effects among them is established. The theoretical basis of mechanical relaxation phenomena in polymers is outlined. The characteristics of relaxation processes associated with molecular mobility are examined with reference to various classes of polymers, in particular, amorphous and crystalline polymers, copolymers, and mechanical mixtures. The characteristics of relaxation processes associated with rearrangement of the supermolecular structures in amorphous and crystalline polymers are considered.This article is a review of mechanical relaxation effects in polymers with particular attention to research conducted in the Problem Laboratory of Polymer Physics of the Moscow Lenin State Pedagogical Institute.Problem Laboratory of Polymer Physics, Lenin Moscow State Pedagogical Institute. Translated from Mekhanika Polimerov, Vol. 5, No. 1, pp. 30–53, January–February, 1969.     

Relation between the elastic deformation of oriented specimens of crystalline polymers and the "large-period" deformation

Illustrative calculations for a specific model of the supermolecular organization of an oriented crystalline polymer are presented as an explanation of the fact that the "large-period" deformation may exceed the macrodeformation of the specimen.Institute of High-Molecular-Weight Compounds, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 4, pp. 579–583, July–August, 1973.     

The theory of orientational drawing of linear amorphous polymers

On the basis of modern ideas on the structure of linear, amorphous polymers a model of a molecular, three-dimensional network with temporary cross-links and van der Waals interaction between the chains is presented. Using this model as a starting point, a differential equation for the deformation of a linear, amorphous polymer in the viscoelastic state is derived. The differential equation for the orientation of a linear, amorphous polymer, which describes the evolution of distribution functions for statistical segments, is obtained. Previously obtained results follow from this theory as special cases.V. I. Lenin State Pedagogic Institute, Moscow. Translated from Mekhanika Polimerov, No. 6, pp. 1021–1028, November–December, 1974.     

Relaxation processes in oriented amorphous and crystalline polymers

Studies were made of the experimental data on the relaxation processes leading to the preferential molecular disorientation and uniaxially drawn amorphous and crystalline polymers.A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 5, pp. 787–792, September–October, 1972.