Nylon 6/SiO2Nanocomposites Synthesized by in situAnionic Polymerization

Abstract

In situ anionic polymerization of °-caprolactam in the presence of SiO2 and silanated SiO2nanoparticles was promoted as a route for the synthesis of two series of nylon 6/SiO2 nanocomposites. The process was performed at 160°C well below the melting temperature of the nylon 6 ( Tm ~ 225°C) and initiated/activated with sodium dicaprolactamato-bis(2-methoxyethoxo)aluminate/ N, N′[methylene-di(4,4′phenylene)bis-carbamoyl]bis- δ-caprolactam system. The nanocomposites obtained exhibit higher onset decomposition temperatures than neat nylon 6 and a tendency of reduction of the polymer yields, degree of polymerization, water absorption and melting temperatures with silica content increasing. The crystallization temperature, Tc of the nanocomposites reaches a maximum value at 2.0 wt.% of the nanoparticles. The mechanical tests of nanocomposites revealed an increase in flexural modulus as a function of filler percentage and a decrease in notched impact strength by addition of the modified silica (over 4.0 wt.%) and unmodified silica. Furthermore, the flexural strength diminishes both the treated and untreated filler content is increased for concentration of ~ 4.0 wt.%

Dispersion of nano-silica in monomer casting nylon6 and its effect on the structure and properties of composites

“…Such strategy was designed according to the following: (i) it was reported that particles with polar surface can be easily wetted by polar liquid [11]. Accordingly, nano-silica with polar silanol groups on the surface can be easily wetted by polar melted caprolactam containing amide group, (ii) the preparation of the nylon6/silica nanocomposites using in-situ anionic polymerization was also recently reported by Rusu and Rusu [12]. It is found that nano-silica was simply dispersed in the melted caprolactam by ordinary stirrer.…”

“…Considering that the tremendous energy offered by ultrasonic is likely to break the nanoparticles aggregations into smaller ones or even mono-dispersing particles [13], in the present work, ultrasound was employed to disperse nanosilica in melted caprolactam. Therefore, the agglomerated nanoparticles would be pulled apart and coated with caprolactam, leading to the improved stability of smaller aggregations and mono-dispersing nanoparticles against re-agglomeration, and (iii) in comparison with classical hydrolytic polymerization of caprolactam which takes about 12-24 hrs [14,15], the rapid anionic polymerization of caprolactam (usually within 1 hr [12,16]) also contributed to the avoidance of re-agglomeration and deposition of nanoparticles during the polymerization process, leading to the uniform distribution of nanoparticles in polymer matrix (Figure 1). Besides, it is well known that the anionic polymerization of caprolactam proceeds well below the melting temperature of the nylon6, which could avoid the degradation in comparison with conventional melt compounding.…”

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

“…It is well known that anionic polymerization of !-CL (APCL) occurs faster (i.e., over a few minutes) than classical hydrolytic polymerization, which takes about 12-24 h [4]. A fast polymerization process in addition to good mechanical properties of PA6 results in a wide range of applications for this polymer in reaction injection molding [5,6], rotational molding [1,7] and centrifugal molding [8][9]. This makes PA6 one of the main engineering materials in use today.…”

Crystallization in Polymer Nanocomposites

“…This effect was attributed to the possible better adhesion between modifi ed silica and polymer, which impeded the motion of the polymer chains and thus hampered the crystallization. However, in another study, Rusu and Rusu [95] observed a maximum increase in the crystallization temperature at 2 wt% nanoparticles for both surface -treated and untreated silica.…”