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

Abstract

For the anionic polymerization of ε‐caprolactam to polyamide‐6 the residual monomer concentration in the final polymer is an important characteristic. To determine this residual ε‐caprolactam monomer concentration, a fast and fail‐safe method was developed, which couples thermogravimetric analysis (TGA) with Fourier transform infrared spectroscopy (FTIR) gas analysis. FTIR allows an identification of the types of gasses released during heat treatment. Calibration of the infrared absorbance of ε‐caprolactam and the corresponding mass loss in TGA allows a quantitative evaluation of the ε‐caprolactam monomer release. Low‐heating rates and powdery samples guarantee high‐precision measurements.

Selective Lanthanide‐Organic Catalyzed Depolymerization of Nylon‐6 to ϵ‐Caprolactam

“…Without a catalyst, only minuscule amounts of caprolactam are obtained (Table 1, entry 6), along with trace impurities assignable to ɛ-caprolactam cyclic oligomers, [29] which are common impurities in the industrial polymerization process. [30] These oligomers can be extracted from the Nylon-6 starting material and observed by 1H NMR in CDCl 3 (Figure S2).…”

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

“…In previous studies, little attention has been paid to the issue of time here, as they usually take a whole day. [17][18][19]27,36 It can be observed from Table S1 that solvent extraction for 2 h followed by vacuum drying 4 h was sufficient to remove residues from the polymerization product. This will provide important reference for the relevant research and production in the future.…”

“…This is due to the fact that the drying of samples and corresponding escape of most of the water, which is also observed in previous literature. 25,27 Both PA6 polymer and CL monomer are easy to absorb water, especially the latter. That is to say, the higher mass percentage of CL in polymerization product, the higher water content of the sample.…”

“…26 Another method to remove the residue is thermogravimetric analysis (TGA) of sample under inert atmosphere. 25,27 Although previous studies have demonstrated the effectiveness of some testing methods, they only focused on the polymer where reaction was completed and never on the intermediate product. With the continuous development of reactive processing technology for PA6 in recent years, such as reactive extrusion, [28][29][30][31] reactive injection molding, [32][33][34] reaction rotational molding, 14,35 and so on.…”

Designing Low-Cost, Green, and Recyclable Deep Eutectic Solvents for Selective Separation and Recovery of Valuable Metals from Spent Li-Ion Batteries

“…TG curves of UC13-DESs displayed a lesser weight loss than CPL, which is attributed to the formation of the hydrogen bond of CPL and UR (Figure S2). 39,40 The TG and DTG curves (Figure 1c) of UC13-FA-DESs under different FA ratios confirmed that the final decomposition temperatures T n of the substance gradually increase, which are 216.6 °C (UC13-FA1.9), 217.0 °C (UC13-FA2.4), 222.1 °C (UC13-FA3.2), and 224.0 °C (UC13-FA4.8), with the increase in the proportion of FA. The results testified to the fact that UC13-FA2.4-DESs with moderate FA content are beneficial to maintain the stable properties of DESs.…”