Caprolactam Magnesium Bromide Research Articles

Nylon-6 and single-walled carbon nanotubes polyamide composites

Two methods for the functionalization of single-walled nanotubes were proposed, namely grafting of acyllactam groups or amine-terminated polyimides. Such modification allows for the preparation of stable nonsagging nanotubes dispersions in the melted ∊-caprolactam. These dispersions were further utilized for in situ ring-opening anionic polymerization of ∊-caprolactam with ∊-caprolactam magnesium bromide as a catalyst and N-acetyl-∊-caprolactam as an activator. Some unique features of the obtained novel nylon-6/nanotubes composites are significantly increased thermal stability ( T5% up to 400°C), enhanced compression modulus and Izod impact strength of polymer blocks (by 25% and 150%, respectively) and advanced tensile strength and elongation of polymer films. Such an improvement in the properties of the composites in comparison with neat nylon-6 was gained by the addition of as little as 0.1–0.01 wt% of modified nanotubes.

Investigation on the reactive processing of textile-ramie fiber reinforced anionic polyamide-6 composites

Abstract A reactive processing was adopted to prepare a new-style and environmentally friendly thermoplastic composite consisting of anionic polyamide-6 (APA-6) and textile-ramie fiber. However, severe polymerization-inhibition and fiber-discoloration phenomena had happened in reactive processing of ramie fiber reinforced APA-6 composites. To analyze the mechanism and find out the solutions for these issues, three kinds of initiators for APA-6 were selected to react with powdery ramie fiber at 150 °C under vacuum respectively. Then, the discolored by-products obtained from the reactions were analyzed using Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) and atomic absorption spectroscopy (AAS). Finally, it was concluded that the reasons for inhibition and discoloration phenomena were mainly due to the special by-products generated from the peeling reaction of cellulose, which were also easy to react with initiators simultaneously. It meant that the initiators for APA-6 were consumed severely, thereby resulting in the failure of polymerization. Meanwhile, a kind of new initiator, caprolactam magnesium bromide, with low activity and weak alkalinity, weakened the peeling reaction and the reaction with active groups on the special by-products, thus the inhibition and discoloration phenomena were suppressed significantly, which overcame the most important challenges for the preparation of ramie fiber reinforced APA-6 composites via reactive processing. This work not only open a new avenue for development of environmentally friendly composites, but also further broaden the applications of natural fibers.

Microcrystal Particles Behaviour in Inkjet Printing of Reactive Nylon Materials

A novel process using inkjet printing of molten materials to produce nylon 6 for additive layer manufacturing applications was investigated. Different reactive mixtures of molten caprolactam with activator and catalyst were characterized for physical properties to understand their jettability in an inkjet system. Although it was found that the surface tension and viscosity of all materials were within the range suitable for inkjet technology according to the literature, microcrystals of undissolved salt of the catalyst complex (caprolactam magnesium bromide) were found to influence melt supply behavior. The influence of the process on the catalyst microcrystal consistency and agglomeration beyond the jetting system was investigated for purged, deposited multiple droplets and also individual droplet samples using hot-stage polarized light microscopy. Quantitative image analysis showed that although microcrystal agglomeration occurred within the accumulated droplets due to kinetics of droplet impact, this however was much less than with the purged samples. A generally consistent content and dispersion of the microcrystals existed within the consecutively deposited droplets.

Polyamide from lactams by reactive rotational molding via anionic ring-opening polymerization: Optimization of processing parameters

A reactive rotational molding (RRM) process was developed to obtain a PA6 by activated anionic ring-opening polymerization of epsilon-caprolactam (APA6). Sodium caprolactamate (C10) and caprolactam magnesium bromide (C1) were employed as catalysts, and difunctional hexamethylene-1,6-dicarbamoylcaprolactam (C20) was used as an activator. The kinetics of the anionic polymerization of !-caprolactam into polyamide 6 was monitored through dynamic rheology and differential scanning calorimetry measurements. The effect of the processing parameters, such as the polymerization temperature, different catalyst/activator combinations and concentrations, on the kinetics of polymerization is discussed. A temperature of 150°C was demonstrated to be the most appropriate. It was also found that crystallization may occur during PA6 polymerization and that the combination C1/C20 was well suited as it permitted a suitable induction time. Isoviscosity curves were drawn in order to determine the available processing window for RRM. The properties of the obtained APA6 were compared with those of a conventionally rotomolded PA6. Results pointed at lower cycle times and increased tensile properties at weak deformation.

Influence of Laurolactam Content on the Clay Intercalation of Polyamide 6,12/Clay Nanocomposites Synthesized by Open Ring Anionic Polymerization

In situ anionic homo‐ and copolymerization of caprolactam (CL) and laurolactam (LL) with sodium montmorillonite clay (NaMMT) was carried out using two different initiators, sodium caprolactamate (CLNa) and caprolactam magnesium bromide (CLMgBr). Degree of conversion and final molecular weight were used to assess the advancement and efficiency of the polymerization reaction and X‐ray diffraction and electron microscopy were used to evaluate the sodium montmorillonite clay intercalation/exfoliation. The use of CLNa as initiator produced a higher conversion degree and molecular weight than the use of CLMgBr. Through DSC, it was observed that CLNa and CLMgBr tended to produce random and block copolymer structures, respectively, and either random or block, this eventually has an effect on the clay dispersion within the polymer matrix. In all cases, increasing the LL content produced a decrease in the conversion degree and in the molecular weight of the resulting polymer.

Facile preparation route for graphene oxide reinforced polyamide 6 composites via in situ anionic ring-opening polymerization

In this study, a new and facile route has been developed to prepare graphene oxide (GO) reinforced polyamide 6 (PA6) composites and synthesize simultaneously PA6 grafted GO hybrid materials: e-caprolactam (CL) was firstly fixed onto the GO sheets coupling by 4,4′-methylenebis(phenyl isocyanate), and then PA6 was grafted from the GO surface by in situ anionic ring-opening polymerization. The polymerization processing was effectively carried out at relatively low reaction temperature (150 °C) and in a short reaction time (20 to 40 min) by using a caprolactam magnesium bromide (C1) initiator in combination with a difunctional hexamethylene-1,6-dicarbamoylcaprolactam (C20) activator. The PA6 grafted graphene oxide (g-GO) was verified by 1H NMR, FTIR, TGA, XPS and AFM. The PA6 grafted GO sheets (g-GO) contain about 74 wt% polymers, which make the GO sheets homogenously dispersed in matrix and gain good interfacial adhesion. The tensile results show that the tensile strength and Young's modulus of the nanocomposites can be obviously improved by incorporation of g-GO at low contents. Furthermore, the crystallization temperature and degree of crystallinity of PA6-GO nanocomposites both increased in the non-isothermal crystallization process, especially for the composites with GO loading less than 0.2 wt%. This simple and effective approach is believed to offer possibilities for broadening the graphene applications with the development of PA6-graphene nanocomposites.

Optimisation of anionic polyamide-6 for vacuum infusion of thermoplastic composites: choice of activator and initiator

A process for the manufacturing of large thermoplastic composite structures through vacuum infusion is currently being developed at Delft University of Technology. This article discusses the choice of activator, initiator and polymerisation temperature for reactive processing of the anionic polyamide-6 resin. It will be shown that this manufacturing process requires another activator–initiator combination than conventional casting. The concentration of the reactive species and the polymerisation temperature, however, determine the polymerisation rate and the physical properties of the polymer. For use in a vacuum infusion process, a hexamethylene-1,6-dicarbamoylcaprolactam activator and a caprolactam magnesium bromide initiator are suggested to allow for longer infusion times and to increase the compatibility with reinforcing fibres.

Starlike Nylon 6/polyurethane block copolymers by reaction injection‐molding process (RIM)

AbstractStarlike block copolymers of Nylon‐6 and polyurethane were synthesized using ε‐caprolactam as a monomer, caprolactam magnesium bromide as a catalyst, and a star prepolymer of polyurethane. These copolymers were compared with the linear block copolymers of Nylon‐6 and polyurethane. Such copolymers were obtained using the reaction injection‐molding process (RIM) of ε‐caprolactam at different contents of polyurethane (5–30 wt %). In increasing the content of the soft phase, in FTIR, a displacement was observed in the band at 1637 cm−1, assigned to the amide I of the Nylon 6, to a higher wavenumber. This suggests a bigger interaction between the urethane group of the polyurethane and the amide group of the Nylon 6. Star block copolymers showed better mechanical properties compared with the linear ones. This behavior is attributed to the higher crystallinity and ramifications present in the materials. The structure and the thermal properties of the copolymers were studied using different techniques such as DSC, WAXS, DMA, and SEM. A decrease in the crystallinity when increasing the soft phase was also observed. Finally, physical tensile, impact, and hardness tests of the copolymers were carried out. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2483–2494, 2001

Polyamides from lactams via anionic ring-opening polymerization: 1. Chemistry and some recent findings

This paper summarizes a study of the anionic polymerization of caprolactam employing a bisimide (isophthaloyl-bis-caprolactam) as the initiator and caprolactam-magnesium bromide as the catalyst. Polymerization temperature had a direct effect on monomer conversion, polymer molecular weight, and level of crystallinity. At initial temperatures of 140°C and higher, equilibrium conversions (∼94%) were reached, whereas at temperatures <140°C, the monomer conversions were considerably lower. A similar trend was observed for molecular weights. Percent crystallinity in the nylon was higher when the polymerization temperature is about 150°C. At higher temperatures, the crystallinity is less. In addition to actual polymerization temperature, the heat history had a profound influence on the level of crystallinity in the polymer. Expectedly, the rate of polymerization increased with polymerization temperature and initiator concentration. In experiments where the difunctional bisimide (isophthaloyl-bis-caprolactam), which has two acyllactam groups per molecule, was replaced on a molar basis by the monofunctional N-acetylcaprolactam, which has one acyllactam group per molecule, the polymerization rate was slower by about 50% because the concentration of the acyllactam group was reduced by half. The initiator concentration had a direct influence on the polymer molecular weight. Up to a concentration of about 3.5 mmol of bisimide initiator/mol of caprolactam, the molecular weight decreased with increasing concentration, and this was consistent with the known mechanism. At higher levels, however, the molecular weight increased with increasing bisimide concentrations, contrary to our expectations. A mechanism that explains this anomaly is proposed. With the monofunctional initiator, the molecular weight decreased with increasing concentration. Incorporation of other monomers in poly(caprolactam) have produced several copolymers with interest properties. Incorporation of about 30 wt% laurolactam resulted in a copolymer that had a crystalline melting point that was only slightly lower than that of nylon 6, but had considerably lowered moisture absorption. The moisture absorption of the copolymer was comparable to that of nylon 12.

Polymerization of lactams, 89 magnesium caprolactamates as initiators of ∈‐caprolactam polymerization

AbstractThe anionic polymerization of ∈‐caprolactam initiated with magnesium initiators was studied in the interval 180–250°C. ∈‐Caprolactam magnesium bromide was much more active than magnesium di(∈‐caprolactamate) and the activity of both depended on the way of their preparation. The polymerizations obey the zero order kinetics with respect to the monomer.

Thermal and mechanical properties of some caprolactam-poly(propylene oxide) block copolymers

Nylon-6 block copolymers with higher impact strength were synthesized using caprolactam as monomer, caprolactam magnesium bromide as catalyst and a telechelic isocyanate-terminated poly(propylene oxide) as macro-activator. various proportions of macro-activator up to 25 wt% were employed in order to examine the influence on the mechanical and thermal properties of the block copolymers. Impact strength increased with increase of macro-activator content but Vicat softening point, Rockwell hardness and crystallization temperature on cooling decreased.