Modification of polyamide 6 with hycar ATBN

The preparation of block copolymers from 6-caprolactam and a liquid amine terminated butadiene-acrylonitrile copolymer Hycar ATBN 1300X21 having higher notched impact strength than ordinary poly(6-caprolactam) was studied. In the polymerization of 6-caprolactam initiated by an adduct of phosphoric acid with 6-caprolactam the influence of initiator concentration (0– 50 mol-%) and Hycar ATBN 1300X21 concentration (0–5 wt.-%) in the polymerization charge, of polymerization time (4 – 72 h) and of temperature (200–280°C) on the 6-caprolactam conversion and on the properties of the copolymers formed were followed. Notched impact strength of the block copolymers prepared under optimized conditions was as high as 13.5 kJ·m^?2.     

Adiabatic anionic polymerization of caprolactam in the presence of N-acylated caprolactam macroactivator: Kinetic study

In this study, bis ?-caprolactam bis-diphenyl methane diisocyanate polypropylene glycol 1000 used as the macroactivator was prepared and well characterized prior to use. The anionic polymerization of ?-caprolactam with the macroactivator as a function of the macroactivator concentration was adiabatically carried out. The adiabatic temperature rise method as well as the macrokinetics were used for elucidation of the kinetics of the polymerization. A nonlinear regression technique was used for determining the parameters of the macrokinetic equation. The equilibrium conversion and equilibrium time obtained were 94–96% and 2–9 min depending on the macroactivator concentration. The effects of the concentrations of macroactivator and ?-caprolactam on the initial rate, apparent overall reaction rate, and the empirical parameters were studied. A side reaction induced by the transfer of the proton in the isocyanurate group of the macroactivator to caprolactam anion was found. According to this finding, a new reaction kinetic model was proposed by properly modifying the macrokinetic equation. © 1993 John Wiley & Sons, Inc.     

The structure and physical properties of anionically polymerized nylon 6 crosslinked by bislactams

Crosslinked polyamides prepared by copolymerization of ?-caprolactam with bislactams under conditions of activated anionic polymerization proceeding adiabatically below their melting point show differences in physico-mechanical properties. Owing to varying copolymerization rates of bislactams, depending on the position of the connecting bridge of the bislactam in relation to the amido group, copolymers with different morphological structure are formed. The differences in the mechanical properties of the copolymers are explained on the basis of the differences in the morphological structure. This explanation is supported by results obtained by measuring the thermal and dynamic properties.     

Synthesis and characteristics of the composites based on poly(caproamide) and multiwalled carbon nanotubes

Polycaproamide composites are synthesized by the anionic activated bulk polymerization of ?-caprolactam in the presence of 0.1–5.0 wt % of multiwalled carbon nanotubes and using low-molecularmass monofunctional (N-acetyl-?-caprolactam) and macromolecular polyfunctional (aromatic polyimides) activating agents. The effect of nanotubes on the polymerization of ?-caprolactam is studied, and this effect is shown to become more pronounced as the concentration of nanotubes is increased. The effect of nanotubes on the microstructure, phase composition, water sorption, thermophysical, mechanical, and friction characteristics of poly(caproamide) is analyzed.     

The kinetics of hydrolytic polymerization of ε-caprolactam. II. Determination of the kinetic and thermodynamic constants by least-squares curve fitting

The kinetic and thermodynamic constants of the hydrolytic polymerization of ?-caprolactam were determined by least-squares curve fitting. The calculations were carried out using observed kinetic data such as concentration of ?-caprolactam ([CL]), endgroup ([EG]), and ?-aminocaproic acid ([ACA]) and time derivatives of each concentration (rates) ?[CL]/?t, ?[EG]/?t, and ?[ACA]/?t. The sets of the converged constants are obtained for the initial water concentrations of 0.42, 0.82, and 1.18 mole/kg. An averaged set of the constants applicable for this range of the initial composition was also evaluated. The compatibility between observed and calculated concentration and rate curves was improved by the use of the newly developed sets of the constants. The mechanism of the polycondensation reaction is also discussed, based on the rate and kinetic constants obtained by this work.     

Polymerization of lactams, 95 Preparation of polyesteramides by the anionic polymerization of ε-caprolactam in the presence of poly(ε-caprolactone)

Preparation of polyesteramides-poly[(ε-caprolactam)-co-(ε-caprolactone)]s by anionic polymerization of ε-caprolactam in the presence of poly(ε-caprolactone) at 150 °C was studied in this paper. ε-Caprolactam magnesium bromide was used as an initiator of polymerization and polymeric materials containing 5-25 wt% ε-caprolactone units were obtained. Thermal methods (DSC and DMA) were employed for characterization of poly[(ε-caprolactam)-co-(ε-caprolactone)]s and their mechanical properties were also evaluated. By introducing the activator with N-acyllactam structure, the polymerization rate increased and it was possible to carry out the polymerization at 110 °C. Mechanical properties of polyesteramides were influenced by both the content of ε-caprolactone units incorporated into copolymer and polymerization temperature. The mechanism of incorporation of poly(ε-caprolactone) is discussed. The results show that it is not possible to restrict exchange transacylation reactions, progressing in the course of polymerization, by kinetic tools.     

Die polymerisation der lactame XIV. Einfluß des hexamethylguanidiniumchlorides auf die aktivierte anionische polymerisation der lactame

It was proved that hexamethylguanidiniumchloride (HMGC) exhibited a pronounced accelerating effect on the activated anionic polymerization of 2-pyrrolidone (40°C) and 6-caprolactam initiated by alkali metal salts of the corresponding lactams. The accelerating effect of HMGC was not specific for a certain type of alkali metal salt of lactams as initiator, it was proved that the effect is operative for polymerization of 6-caprolactam when using sodium or cesium salt of 6-caprolactam. It was proved that HMGC does not form growing centers under reaction conditions studied. The initial polymerization rate in the homogeneous phase is a linear function of square root of HMGC concentration at constant concentrations of initiator and activator. On the basis of this finding it was possible to suggest a plausible mechanism of HMGC influence on the polymerization process.     

Depolymerization of poly-ϵ-caprolactam catalyzed by sodium hydroxide

Depolymerization of poly-?-caprolactam chips was carried out at low pressures (3–15 mm Hg) and elevated temperature (225°–270°C) in the presence of sodium hydroxide as catalyst. The effects of variation of amount of sodium hydroxide, time, temperature, and pressure on ?-caprolactam yield were studied. With increase in alkali content the yield increases linearly, reaching a maximum at 1% (w/w) NaOH and then falls. The yield increases with time of depolymerization up to 4 1/2 hr and then becomes practically constant. Between 240° and 250°C there is a sudden increase in depolymerization rate. Further increase in temperature has very little effect. Decrease in pressure from 15 to 3 mm Hg shows a nine-fold increase in yield. The optimum conditions for the depolymerization were a temperature of 250°C, a pressure of 3 mm Hg, and a time 4 1/2 hr in the presence of 1% NaOH (w/w), which gave a 90.5% yield of ?-caprolactam. Physical properties, IR spectra, and behavior toward polymerization of the recovered monomer indicated the presence of some impurities.     

On the synthesis of poly(ε-caprolactam)—poly(butadiene-co-acrylonitrile) block copolymers for the reaction injection molding process

The liquid rubbers Hycar ATBN and HTBN were used in the preparation of poly(ε-caprolactam)—poly(butadiene-co-acrylonitrile) block copolymers intended for reaction injection molding by the anionic polymerization of ε-caprolactam. The conversion of Hycar end groups to polymerization growth centers and the conditions of polymerization influence the crystallization, morphology, and mechanical properties of the product through its molecular structure. The contribution of individual reactions to this molecular structure is discussed.     

Flammability and thermal behavior of phosphorus-containing polyamide-6

An investigation is reported on the flammability and thermal behavior of polyamide-6, obtained by anionic polymerization of ?-caprolactam, carried out in bulk, in the presence of the following N-substituted phosphorus-containing lactam derivatives: diethyl-(N-caprolactam)-phosphonite (PL₁), diethyl-(N-caprolactam)-phosphonate (PL₂), and 2,5-dichlorophenyl-bis(N-caprolactam)-phosphinate (PL₃). Phosphorus-containing lactam derivatives PL,₁ and PL₃ are used as activators of the anionic polymerization of ?-caprolactam, and PL₂, as a modifying additive. The phosphorus-containing polyamide-6 possesses improved flame retardancy, as well as improved thermo- and thermooxidative resistance. Destruction kinetics were studied in nitrogen and air atmospheres, and the activation energy for thermal and thermooxidative destruction have been determined. The effect of PL₁ PL₂, and PL₃ on the melting temperature (T_m) and glass-transition temperature (T_g) of polyamide-6 was established. © 1993 John Wiley & Sons, Inc.     

Flame-resistant polycaproamide by anionic polymerization of ϵ-caprolactam in the presence of suitable flame-retardant agents

Poly(?-caprolactam) (PCL) with improved flame-retardant (FR) properties can be easily obtained by activated anionic polymerization of the monomer, ?-caprolactam (C), in the presence of adequate amounts of red phosphorus (red P). Analogous results with reduced P content can be achieved by coupling red P with a synergistic compound such as a chlorinated hydrocarbon or magnesium oxide (MgO). A peculiar advantage of this method is the possibility of obtaining a very fine and homogeneous dispersion of the FR additive in the polymer matrix, meanwhile avoiding the typical compounding techniques, which are expensive, often unsafe, and require melt mixing of the ingredients. Molecular, thermal, and mechanical characterization, as well as morphology of the resultant products, have been determined: No significant properties change have been found when FR agents are present, apart from the relevant improvement of the flame-resistance. Thus, by this novel procedure it is possible to prepare FR poly-(?-caprolactam) without any appreciable deterioration of its typical properties.     

Mechanism and kinetics of adiabatic anionic polymerization of ϵ-caprolactam in the presence of various activators

Nylon 6 was prepared by adiabatic anionic polymerization of ?-caprolactam using hexamethylene dicarbamoyl dicaprolactam (HDC), cyclohexyl carbamoyl caprolactam (CCC), or phenyl carbamoyl caprolactam (PCC) as activators and sodium caprolactamate (NaCL) as a catalyst at various initial reaction temperatures ranging from 130 to 160°C. Adiabatic temperature rise was recorded as a function of polymerization time to investigate polymerization kinetics. Kinetic parameters for polymerization, which are more accurate than data reported to date, could be obtained by fitting the temperature rise data with a new polymerization kinetic equation involving crystallization exotherm and thermal conduction. The polymerization rate highly depended on the chemical structure of the activator used, which indicates that the initiating step where the activator is attacked nucleophilically by NaCL is a very important reaction step, affecting the overall polymerization rate. CCC showed the fastest polymerization rate, whereas HDC and PCC showed the medium and the slowest rate, respectively. The contributions of crystallization exotherm and thermal conduction to the resultant temperature rise during polymerization were significant, when the initial reaction temperature was lower than 140°C. In all cases, the molecular weight obtained from intrinsic viscosity measurement was greater than the expected molecular weight. This may be attributed to the branching and/or crosslinking reaction through Claisen-type condensation reactions. © 1995 John Wiley & Sons, Inc.     

Kinetics of anionic polymerization of lactams. (Solution of non-isothermal kinetic problems by the inverse method)

Wide use has been made of non-isothermic studies for obtaining kinetic data on the anionic polymerization of ?-caprolactam and ω-dodecalactam. Data are obtained by measuring changes in reaction temperature, under conditions of heat exchange with the surroundings and by solving the inverse thermophysical problem. This solution yields kinetic constants, which when substituted into heat conduction and kinetic equations minimize the deviations of calculated temperature dependences on time and the deviations in experimental data. Thus, we have studied qualitatively the polymerization of lactams. Numerical values of the basic kinetic constants in the macrokinetic scheme have been determined. Some new effects, such as self-acceleration in the polymerization of caprolactam and the increase of the apparent activation energy at high degrees of conversion in the polymerization of dodecalactam were detected. The approach may be useful in studying other polymerizations.     

Morphology and Thermal Behavior of MCPA6/SAN Blends Prepared by Anionic Ring-Opening Polymerization of ε-caprolactam

Summary In this article, a series of blends of monomer casting polyamide 6 and styrene-co-acrylonitrile (MCPA6/SAN) were prepared by in situ anionic ring-opening polymerization of ε-caprolactam (CL). Their morphology and thermal behaviors were investigated by means of scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and wide-angle x-ray diffraction (WAXD), respectively. The SAN phase had much finer domain in MCPA6/SAN than that in the polyamide6/SAN (PA6/SAN) blends prepared by melt blending of PA6 and SAN. All the melting and crystallization parameters of MCPA6/SAN blends decreased gradually with the increase of SAN content, while the melting temperature was almost unchanged. These results were due to the hydrolysis reaction of SAN occurred during the anionic polymerization of ε-caprolactam (CL). In addition, WAXD results showed that only α crystal forms existed in the MCPA6/SAN blends.     

Polymerization of lactams, 48. Autocopolymerization of 6-caprolactam with 12-dodecanelactam

The homo- and copolymerization of 6-caprolactam and 12-dodecanelactam was studied in the absence of an intentionally added initator. Both the polymerization and the copolymerization of an equimolar mixture of the monomers exhibited an induction period, the length of which was reduced with increasing temperature. Above 260°C, the polymers and copolymers of 6-caprolactam were not stable and their intrinsic viscosities as well as the polymer content decreased during long polymerization periods. On the other hand, insoluble products were formed in the homopolymerization of 12-dodecanelactam at temperatures of 300°C and higher. As much as 35 wt.-% of oligomers, predominantly cyclic ones, were formed in the initial stage of polymerization and copolymerization.     

Powdered poly(ethylene terephthalate)

The influence of the conditions of preparation on the properties of powdered poly(ethylene terephthalate) was followed from the point of view of its specific surface. The powdered poly(ethylene terephthalate) prepared by reprecipitation from the melt of 6-caprolactam has a porous and structured surface, and consequently, also a large specific surface in comparison with the powedered poly(ethylene terephthalate) prepared by mechanical milling. The specific surface value is influenced by the cooling rate of the initial homogeneous melt of poly(ethylene terephthalate)-6-caprolactam, by the concentration of poly(ethylene terephthalate) in this melt and by its molecular weight, by the water temperature at the extraction of 6-caprolactam from the tough mixed melt, by the drying temperature of the powdered poly(ethylene terephthalate), and by the content of residual 6-caprolactam in the powdered product. In the examined area, the specific surface value of the powdered poly(ethylene terephthalate) prepared by reprecipitation from the melt of 6-caprolactam ranged from 10 to 110 m²·g^?1.     

Polymerization of lactams, 49. Hydrolytic polymerization of 6-caprolactam in the presence of its cyclic dimer

The hydrolytic polymerization of 6-caprolactam has been studied at 260–280°C in the presence of 5, 10 and 15 mol-% of cyclic dimer of 6-caprolactam and 2 mol-% of 6-aminocaproic acid as an initiator. The content of monomer and cyclic oligomers, including pentamer, was determined by HPLC. It has been proved that the rate of polymerization decreases with increasing content of cyclic dimer in the initial mixture and the time required to attain the equilibrium content of polymer increases as much as by an order of magnitude. The cyclic dimer is incorporated into the polymer above all in the final reaction stage.     

Die polymerisation der lactame XI. Die copolymerisation von 6-caprolactam mit 12-laurolactam

The course of the incorporation of 6-caprolactam and 12-laurolactam into polymer chains during the hydrolytic, cationic and anionic copolymerization for an equimolar ratio of the monomers was studied. During the hydrolytic copolymerization 6-caprolactam is incorporated more rapidly at 260, 230 or 200°C at the beginning of the polymerization process; the differences between incorporation rates of the lactams into the copolymer increase with decreasing temperature. During the cationic copolymerization the incorporation of 12-laurolactam is more rapid by orders of magnitude for the above temperatures at the beginning of the process. Changes in the composition of cationic copolymers as compared to the hydrolytic copolymers are independent of the temperature during the copolymerization. The anionic copolymerization is characterized by a more rapid incorporation of 6-caprolactam into the polymer chain. The differences in the polymerization activity of the two lactams decrease with increasing temperature of the anionic copolymerization. The described course of incorporation of individual monomers, with the various mechanisms of the polymerization, also corresponds to melting points of copolymers in accordance with their composition.     

Polymerization of lactams, 38. Copolymerization of 6-caprolactam with some of its non-homopolymerizing derivatives

It was demonstrated that non-homopolymerizing derivatives of 6-caprolactam: 7-cyclohexyl-1-aza-2-cycloheptanone (I) and 7-isopropyl-5-methyl-1-aza-2-cycloheptanone (II) were polymerizing with 6-caprolactam under conditions of the socalled hydrolytic polymerization. With its increasing content in the initial reaction mixture the copolymerization rate, the equilibrium content of the copolymer, and the reduced viscosity decreased. Lactam (I) was a more reactive comonomer in comparison with lactam (II).     

Die Polymerisation von Lactamen. IV. Die anionische Copolymerisation von 6-Caprolactam mit 8-Caprylolactam

Conditions were defined for preparing homogeneous castings based on copolymers of 6-caprolactam and 8-caprylolactam under conditions of the low-temperature adiabatic copolymerization of the two lactams below the melting point of polymeric products (catalyst: sodium salt of lactams, activator: N-acetyl-6-caprolactam). The content of 8-caprylolactam in the copolymer cannot exceed 30 mole-% owing to its high polymerization heat and to the dependence of the copolymer melting point on the concentrations of the two lactams; the homopolymerization of the 8-caprylolactam cannot be accomplished under these conditions. The copolymer melting point exhibits a minimum in the region of the equimolar ratio of the two lactams. Further, the temperature dependence of the 8-caprylolactam specific heat was determined over an interval of 100 to 226°C (C_p = 0.2543 + 0.0007 T). The copolymerization rate of the anionic process increases with increasing content of 8-caprylolactarn, in accordance with differences of several orders existing between homopolymerization rates of the two lactams. The content of water extractable portions in the copolymers drops proportionally to increasing content of 8-caprylolactam, similarly as in equilibrium copolymers prepared by the hydrolytic copolymerization.