Nucleation and Crystallization of PA6 Composites Prepared by T-RTM: Effects of Carbon and Glass Fiber Loading

Abstract

Thermoplastic resin transfer molding (T-RTM) is attracting much attention due to the need for recyclable alternatives to thermoset materials. In this work, we have prepared polyamide-6 (PA6) and PA6/fiber composites by T-RTM of caprolactam. Glass and carbon fibers were employed in a fixed amount of 60 and 47 wt.%, respectively. Neat PA6 and PA6 matrices (of PA6-GF and PA6-CF) of approximately 200 kg/mol were obtained with conversion ratios exceeding 95%. Both carbon fibers (CF) and glass fibers (GF) were able to nucleate PA6, with efficiencies of 44% and 26%, respectively. The α crystal polymorph of PA6 was present in all samples. The lamellar spacing, lamellar thickness and crystallinity degree did not show significant variations in the samples with or without fibers as result of the slow cooling process applied during T-RTM. The overall isothermal crystallization rate decreased in the order: PA6-CF > PA6-GF > neat PA6, as a consequence of the different nucleation efficiencies. The overall crystallization kinetics data were successfully described by the Avrami equation. The lamellar stack morphology observed by atomic force microscopy (AFM) is consistent with 2D superstructural aggregates (n = 2) for all samples. Finally, the reinforcement effect of fibers was larger than one order of magnitude in the values of elastic modulus and tensile strength.

Influence of fiber orientation, temperature and relative humidity on the long‐term performance of short glass fiber reinforced polyamide 6

“…It is known that the addition of fibers might potentially affect the degree of crystallinity of a composite by increasing the numbers of nucleation sites and crystal growth rate. But as showed in Reference 46, the crystallinity increase is rather small (from 23% in the matrix to 26% in the glass fiber reinforced polyamide 6). This compares well to the differences in crystallinity obtained by Parodi et al Consequently, it is assumed that the overall effect of fiber addition on T g is small and within experimental error it can be assumed independent of fiber content.…”

Self-Nucleation Effects on Polymer Crystallization

“…The lower the value of Ts, the higher is the Tc upon cooling from the melt, indicating a stronger nucleation effect. This peculiar nucleation effect has been termed in different ways in the literature: crystalline memory 38,39,41,[56][57][58]61,63,[66][67][68][69][70][71][72][73][74][75][76][77][78][79][80] , melt memory 49,52,60,64,[81][82][83][84][85][86][87][88][89][90][91][92][93][94] , in some works both terms are used indistinctly 18,47,48,62,65,[95][96][97][98] and in other cases a mo...…”

“…The lower the value of T s , the higher is the T c upon cooling from the melt, indicating a stronger nucleation effect. This peculiar nucleation effect has been termed in different ways in the literature: crystalline memory, ,,,− ,,,− melt memory, ,,,,− in some works both terms are used indistinctly, ,,,,,− and in other cases a more general term, memory effect, has been employed. ,,,− ,,− In this Perspective, we will use the term melt memory to emphasize that this effect occurs when, according to calorimetric evidence, there are no crystal fragments present in the melt (i.e., in the so-called Domain IIa ; see section ).…”

The effect of the titanium dioxide nanoparticles on the morphology and degradation of polyamide 6 prepared by anionic ring‐opening polymerization

“…The composite base layer and the surface layer can be produced in one cycle with this technology. [ 1–9 ]…”

“…The composite base layer and the surface layer can be produced in one cycle with this technology. [1][2][3][4][5][6][7][8][9] Cyclic lactams (amides) are most often produced by anionic ring-opening polymerization. [10][11][12][13] The process is popular, not only because it is fast, but also due to its low activation energy and minimal material requirements.…”