Effect of thermal annealing on crystallinity and mechanical strength of textile glass and carbon fiber reinforced in situ polymerized ϵ-caprolactam parts

Oligomer composition and content in regenerated PA6 fiber and its effect on properties

“…[8][9][10] Whether chemical regeneration or physical regeneration is used, changes in the micromolecular structure of PA6 significantly affect its crystallization, orientation, mechanical, and dyeing properties. [11][12][13] The average molecular weight of PA6 material usually increases slightly during repeated meltextrusion regeneration, but the mechanical properties of PA6 fibers prepared by repeated cycles typically decrease by 10-15%, which may be attributed to a broadening of the molecular weight distribution and an increase in the low-molecular-weight impurity content. [14][15][16] When the melting process temperature is 240-260 C, the melt polycondensation reaction of PA6 is more obvious than the thermal degradation reaction, resulting in a slight increase in the average molecular weight.…”

“…Physical regeneration involves the melting and reconstitution of PA6 products, whereas chemical regeneration involves the degradation of waste into small monomers, recovering resources through chemical depolymerization 8–10 . Whether chemical regeneration or physical regeneration is used, changes in the micromolecular structure of PA6 significantly affect its crystallization, orientation, mechanical, and dyeing properties 11–13 . The average molecular weight of PA6 material usually increases slightly during repeated melt‐extrusion regeneration, but the mechanical properties of PA6 fibers prepared by repeated cycles typically decrease by 10–15%, which may be attributed to a broadening of the molecular weight distribution and an increase in the low‐molecular‐weight impurity content 14–16 .…”

An applicability study on various methods for determining the monomer conversion rate of polyamide 6

“…Several methods have been proposed to determine the conversion rate of CL. They include gravimetry, [16][17][18][19][20][21] gas chromatography, 22,23 enthalpy of polymerization, 10,24 and so forth. Among them, the gravimetry is favored by the majority of researchers because of its easy realization and stable result.…”

Determination of the residual monomer concentration of ε‐caprolactam in polyamide‐6 using thermogravimetric analysis coupled with Fourier transform infrared spectroscopy gas analysis

“…One technique is gravimetry after solvent extraction of the monomer. After grinding, the polymer is treated for several hours in a solvent, commonly methanol 13,22,23 or distilled water, 1,24,25 which dissolves the low-molecular weight monomer molecules from the polymer. The residual monomer concentration is determined by the weight ratio of the dissolved monomer and the polymer before extraction.…”