Some characteristics of low-temperature hydrolytic polymerization of caprolactam

Spontaneous crystallization of linear PCA chains during low-temperature hydrolytic polymerization of caprolactam (CL) is only observed when the temperature of synthesis is decreased to 473 K. At T = 473 K, hydrolytic polymerization of CL takes place in three successive regimes: purely liquid-phase, mixed (liquid and solid-phase), and purely solid-phase, and the proportion of CL converted into linear chain units in the second regime of the reaction increases from 1.8 to 18.2% with a decrease in the synthesis temperature from 473 to 443 K. The efficiency of the solid-phase stage of the process and low-temperature hydrolytic polymerization of CL as a whole increases with an increase in the degree of crystallinily of the PCA formed, and of the two reactions which take place in the amorphous phase of the polymer — polymerization of CL or polycondensation of linear chains — the first is relatively faster. Translated from Khimicheskie Volokna, No. 2, pp. 15–18, March–April, 1998.     

Distribution of water and of caprolactam between vapor and polymer phases in the solid-phase synthesis of polycaproamide

Conclusions -- Distribution constants of water and CL between the vapor phase and solid PCA at 413–463 K have been determined.-- Results of calculations have been given which show that the stage of solid-phase final amidation of PCA can be realized in apparatus which ensures maintaining the pressure in the range 1.1–1.5 MPa; thereupon, the losses of CL because of evaporation into the free volume of the apparatus do not exceed 9 kg per ton of polymer.Translated from Khimicheskie Volokna, No. 4, pp. 14–15, July–August, 1991.     

Nonisothermal flow of polymer melts and solutions in spinneret channels

Conclusions The effect of dissipation of mechanical energy on the temperature fields of polymer melts and solutions in the channels of spinnerets for fibre spinning has been investigated.It has been shown that the flow of polymer melts in spinneret channels takes place with only slight heat evolution, that is, practically under isothermal conditions. The flow of polymer solutions takes place significantly under nonisothermal conditions, with a large drop in temperature over the channel radius.Translated from Khimicheskie Volokna, No. 4, pp. 42–44, July–August, 1986.     

Thermal properties of sulfo-containing cation exchangers based on copolymers of vinylidene fluoride

It was found that when sulfo-containing cation exchangers based on PVDF and its copolymers are heated in air, the reaction of dehydrofluorination of the sulfonated unit in VDF takes place in the 50–100°C temperature region and the reaction of formation of sulfones with the participation of sulfo groups and macromolecules of the polymer takes place in the 220–250°C region. Treating sulfo-containing PVDF cation exchangers with an excess of ammonia with subsequent heat treatment at 110°C and reduction with hydrochloric acid increases the thermal stability of the sulfo-containing cation exchangers, and the temperature of initial weight loss is 200°C. The apparent activation energies of dehydrofluorination, formation of sulfones, and degradation of the macromolecular chain were determined and were in satisfactory agreement with the published data.Translated from Khimicheskie Volokna, No. 6, pp. 43–47, November–December, 1994.     

The problem of orientation strenghthening of polycaproamide fibres

It is shown that the absolute strength of PCA fibre at 291 K is almost independent of the preliminary draw ratio and the relative strength increases proportionally to the total draw ratio attained in orientation drawing and subsequent stretching at a constant rate. The values of the breaking load and total draw ratio of the oriented fibre can be lower than for the unoriented fibre. The data obtained suggest the existence of temperature-force conditions that allow significantly increasing the orientation draw ratio of PCA fibres.Translated from Khimicheskie Volokna, No. 5, pp. 20–21, September–October, 2004.     

A mathematical model of the melting of polymeric materials in extruders. Investigation of the form of the interface and of melt velocity profiles

Conclusions The form of the interface in the melting of a polymer in an extruder has been studied. It has been found that it differs considerably from right-angled, and melting of the polymer takes place over its entire curvolinear surface.The three components of polymer melt velocity have been constructed: The change in these both over the cross-sectional area of the extruder screw and also along its length has been noted.In the liquid phase of the polymer, an intense circulation of the melt takes place in the transverse plane of the screw channel.Translated from Khimicheskie Volokna, No. 5, pp. 40–42, September–October, 1984.     

Acylation of terminal amino groups in the synthesis of poly-m-phenyleneisophthalamide

Conclusions The reaction between terminal amino groups and dimethylacetamide in acid reaction solutions of PMPIA oligomers (or polymer) at elevated temperatures (80–90°C) has been investigated. The process takes place quantitatively and is catalyzed by the presence of hydrogen chloride. Similar relationships were obtained with m-phenylenediamine.The occurrence of the acylaton reaction via decomposition of dimethylacetamide has been confirmed by polarographic analysis of the accumulation of dimethylamine in the system and by potentiometric titration of the consumption of hydrogen chloride in binding up the dimethylamine which is liberated.Translated from Khimicheskie Volokna, No. 5, pp. 26–27. September–October, 1987.     

Action of the H3PO4−H2O-polyethylene glycol system in the synthesis of polycaproamide

Conclusions Use of the ternary activating system H₃PO₄–H₂O-PEG is a rather efficient method in the one-stage synthesis of PCA having a degree of polymerization of 150–200.Formation of amidinium groups during the PCA synthesis process aids in increasing its stability to further polycendensation.Lowering the moisture content of the PCA melt in the stage of its synthesis to 0.05–0.08% by wt. should eliminate the effect of further polycondensation of the polymer in spinning fibres of almost any assortment.Translated from Khimicheskie Volokna, No. 3, pp. 22–23, May–June, 1983.     

Thermal decomposition of poly(tetramethyloxydisilaethylene)

Thermal decomposition of poly[oxybis(dimethylsilylene)] having chains terminated with trimethylsiloxy groups was studied by thermogravimetry, pyrolysis-mass spectrometry, and infrared spectroscopy. The polymer is thermally less stable than poly(dimethylsiloxane). Depolymerization occurs at temperatures of 250–350°C, although this process also takes place at lower temperatures. The depolymerization produces cyclic oligomers of general formula [(Me₂Si)₂O] _n , with predominant formation of the oligomern=2. The depolymerization is accompanied by processes which are referred to as restructurization because they change the structure of the polymer backbone. Decomposition may lead also to the formation of branching points. The shape of the thermograms taken under isothermal conditions is in agreement with an unzipping mechanism for depolymerization involving random initiation. Excluding the short initial period of the process, the unzipping is terminated at a restructurization point. A low activation energy points to initiation induced by electron transfer, presumably involving traces of contaminant. At higher temperatures, 350–600°C, loss of organic parts of the polymer takes place along with further restructurization. At higher temperatures the polymer was also found to undergo easily oxygenation of its backbone with atmospheric oxygen, which leads to the formation of siloxane groups.     

Bulk surface photografting process and its applications. I. Reactions and kinetics

A bulk surface photografting process which is conducted in the interface between two polymer films was designed and investigated. The bulk surface photografting is a highly efficient process. With this method, the surface of hydrophobic polymers can be made hydrophilic in less than 2 s and a grafted layer 5 μm thick can be obtained in 30 s. The kinetic investigation shows that the bulk surface photografting polymerization involves a four-step reaction process: induction period, surface initiation, successive polymerization, involves a four-step reaction process: induction period, surface initiation, successive polymerization, and solid-phase crosslinking. The photoreduction of benzophenone (BP) takes place in the interlayer between the LDPE films and is a three-stage process: surface photoreduction, secondary photoreduction, and solid-state photoreduction. With regard to the photoreduction of the initiator caused by hydrogen abstraction, the kinetic studies show that the photoreduction rate has a first-order dependence on the BP concentration. The activation energy of the hydrogen abstraction reaction is about 28.5 KJ (6.8 kcal)/mol. With regard to the photografting polymerization reaction, the reaction order of the rate Rp with respect to the monomer is unity and 0.89 with respect to BP. This means that the termination reaction takes place mainly by combination of polymer chain free radicals and semipinacol free radicals from BP. The activation energy of the overall polymerization reaction is around 8.8 kJ (2.1 kcal)/mol. © 1996 John Wiley & Sons, Inc.     

Failure of polypropylene fibers

Conclusions A quantitative definition of the highly elastic deformation built up in extension of polypropylene fiber has been proposed.In the extension of a crystallizing polymer, under definite temperature-deformation conditions, a steady flow regime is reached (analogous to amorphous polymers). Under these conditions, breakage takes place on reaching a critical fiber diameter, regardless of the original fiber thickness.Translated from Khimicheskie Volokna, No. 4, pp. 22–23, July–August, 1983.     

Drying and conditioning viscose staple fibre

Conclusions With respect to the mechanism of moisture removal, the process of drying viscose staple fibre is divided into two stages. The first stage takes place at a constant rate. Removal of moisture takes place by the mechanism of evaporation from a free surface. In the second stage, mainly solvated bound water is removed, by a desorption mechanism, which is described by an equation for a first order chemical reaction.The main factor which determines the kinetics of fibre drying in the second state is temperature. At a temperature of 100–120°C, the amount of air delivered to the second dryer can be reduced from 14,000–16,000 to 3,000–5,000 m³/h.The significant effect of the degree of fibre loosening on drying kinetics has been demonstrated.Translated from Khimicheskie Volokna, No. 6, pp. 28–32, November–December, 1986.     

Dyeing of polyamide granulate with preliminary treatment with acetic acid solution

It was found that preliminary treatment of PCA granulate with a dilute solution of CH₃COOH sharply increases the rate and degree of sorption of acid dyes by PCA granulate. A technological regime for dyeing PCA granulate with acid dyes was proposed and approved in industrial conditions; it allows increasing the intensity of the color by several times with almost total extraction of the dye from the bath.Ivanovo State Academy of Chemical Engineering. Translated from Khimicheskie Volokna, No. 4, pp. 35–37, July–August, 1996.     

Preparation of high-molecular-weight polycaproamide by the method of removing water from the melt with nitrogen in the stage of polycondensation at normal pressure

Conclusions A necessary condition for obtaining high-quality PCA is carrying out the synthesis process, and, especially, the polycondensation reactions, at a water content in the reaction system which is close to the equilibrium figure. Thereupon, it is preferable to maintain a reduced melt temperature (513–528°K) in the finishing stage of the polycondensation.It is possible to fulfill the indicated conditions at reasonably high process rates by performing the first stage under water vapor pressure until monomer polymer equilibrium is attained, and performing the polycondensation stage with repeated renewal of a well-developed melt surface, which assists in intensive water removal without local drying out of the polymer.Translated from Khimicheskie Volokna, No. 5, pp. 20–22, September–October, 1983.     

Sex pheromone of European grapevine moth (Lobesia botrana) its chemical transformations in sunlight and heat

Photo- and radical isomerization of (E, Z)-7,9-dodecadien-1-yl acetate (DDA) leads to an equilibrium mixture of all four possible geometric isomers of 7,9-DDA in the ratio ofE,E, 69–76%;Z,E, 11–13%;E, Z, 12–15%; andZ, Z, 1–3%. Iodine catalysis of the isomerization takes place even in dark at room temperature and is probably a radical reaction.     

Operational properties of the chemisorptive fibre VION AN-1

Conclusions Boundary conditions have been determined for the regeneration of VION AN-1 fibre which ensure retention of its sorptive properties on repeated use.The rate of sorption of acid vapors depends on the original fibre structure only at a low relative humidity of the gas stream.On sorption of acid vapor by the moistened fibre, hydration of the ionogenic groups of the polymer takes place; this leads to a change in its structure. In this case, the rate of sorption does not depend on the porosity of the original fibre.Translated from Khimicheskie Volokna, No. 3, pp. 37–38, May–June, 1987.     

A mathematical model of the fusion of polymeric materials in extruders. Effect of polymer physical properties and processing regimes on rate of fusion

Conclusions The effect of polymer physical properties, rate of extruder screw rotation, and preliminary heating of the polymer on its rate of fusion have been studied.It has been shown that in individual sections of the interface a freezing of previously melted polymer takes place.The rate of polymer fusion along the screw channel is not constant, and as the flake moves from the inlet pipe of the extruder to the exit pipe, it initially decreases, then rises, and then drops again.Translated from Khimicheskie Volokna, No. 6, pp. 46–48, November–December, 1984.     

Preparation of cation-exchange polycaproamide fibers

Conclusions -- The process of preparing cation-exchange PCA fibers by the radical graft polymerization of potassium p-styrene-sulfonate in aqueous and in aqueous salt solutions of the monomer has been investigated. The identity of the kinetic parameters (reaction order with respect to monomer and the effective activation energy) of the heterophase graft polymerization of PSS indicates the occurrence of the graft polymerization in the kinetic region.-- A beneficial effect of the nature of the low-molecular electrolyte on the reaction rate and yield of graft polymer has been established; and the optimum content of electrolyte in the reaction mixture has been determined. Cation-exchange fibers have been obtained having an exchange capacity up to 1.3 meq/g.Translated from Khimicheskie Volokna, No. 2, pp. 12–14, March–April, 1993.     

Fabrication and properties of modified polyamide fibres in combination of graft polymerization and alkylation

The important possibility of fabricating PCA fibers with improved hygienic properties with a low concentration of polymeric modifier — PDMAEMA quaternary salt — with the reaction of radical graft polymerization in a two-component solution of monomer and alkylating agent was demonstrated. The basic characteristics of graft polymerization of DMAEMA and alkylation combined in the stage of modification of the surface of the fiber-forming polymer were investigated.Moscow State Textile Academy. Translated from Khimicheskie Volokna, No. 3, pp. 17–20, May–June, 1994.     

Synthesis of a novel comb-like poly(vinyl ether) with isopropylnaphthoxy pendant by cationic polymerization

Summary A novel comb-like polymer having isopropylnaphthoxy pendant with the controlled molecular structure was synthesized by the cationic polymerization of 2-(6-isopropyl-2-naphthoxy)ethyl vinyl ether with AlEtCl₂ catalyst. Although the polymer's molecular weight (Mn: 4,000–17,000) could be controlled by the reaction conditions (sovent polarity, temperature and initial monomer concentration), the steric structure was not affected by them at all, giving almost the same amount of the meso and racemic diads irrespective of the conditions. The polymer showed only an amorphous character (Tg: 22–45 °C) but not any liquid crystalline phase.