Kevlar-like Aramid Polymers from Mixed PET Waste

Abstract

This work describes the synthetic approaches, spectroscopic and thermal characterization of aramid polymers prepared from waste polyethylene terephthalate (PET) via sustainable and scalable processes. Direct depolymerization of PET with aliphatic diamines under melt conditions resulted in decomposition without substantial formation of any aramid polymer. The Higashi–Ogata methodology or direct polycondensation of terephthalic acid (TPA) derived from PET waste and p -phenylenediamine, resulted in oligomerization and formation of aramids with a low degree of polymerization. The highest molecular weight polymers were obtained via the acid chloride of TPA, the traditional method. A proprietary solvent enabled the dissolution of most polymers and subsequent size exclusion chromatography analysis in the same solvent. We emphasize that although the soluble polymer compounds are prepared via the traditional route, they are novel. The apparent molecular weights of the soluble polymers ranged between 10–35 kDa ( M n ) and 28–81 kDa ( M w ). All analogues were prepared with commercially available diamines and diamine combinations. The obtained solid powders were dissolved in D 2 SO 4 and analyzed spectroscopically to qualitatively evaluate the degrees of polymerization, while the solids were characterized via thermogravimetric analysis and differential scanning calorimetry. Many reaction conditions were employed to improve the solution polycondensation reaction, and it was found that addition of pyridine (2 eq) to the NMP reaction medium was crucial in preventing the precipitation of the polymer. Contrary to conventional wisdom, CaCl 2 did not play a crucial role in the molecular weight increase of the polymer when oxydianiline was used. Our data indicated that the temperature and absence of CaCl 2 provided a boost in molecular weight. Both room temperature and 0 °C reactions generated similar polymers as suggested by nuclear magnetic resonance; however, the cold conditions enhanced gel formation, an important attribute in the future processing of these materials to obtain fibers. All analogues had a high degradation temperature at 5 and 10% weight loss ( 5% and T 10% ), above 400 °C, along with high percent char values. A glass transition ( T g ) was not detected in any of the analogues prepared.

Correlating Surface Chemistry to Surface Relaxivity via TD-NMR Studies of Polymer Particle Suspensions

“…Kevlar is known for its rigid polymeric structure, reflecting the low mobility of phenyl rings and the strong intermolecular hydrogen bonding between amide groups . These characteristics grant Kevlar its high tensile strength and low solubility, which might reflect the low surface relaxivities observed here . Surprisingly, PS-AAL also showed low surface relaxivity values for both liquids.…”

“… 71 These characteristics grant Kevlar its high tensile strength and low solubility, which might reflect the low surface relaxivities observed here. 72 Surprisingly, PS-AAL also showed low surface relaxivity values for both liquids. Jeong et al recently discussed the dominance of dispersive over polar forces in PS-AAL (40% AAL) surfaces, reporting contact angles of ∼73 and ∼32° for water and diiodomethane, respectively.…”

Preparation and Properties of Mechanically Robust, Colorless, and Transparent Aramid Films

“…In solution condensation polymerization, by using an aprotic polar amide solvent such as DMAc or NMP and adding salts such as LiCl and CaCl 2 , the solubility of the polymer can be increased and thus a high molecular weight polymer can be obtained. Cosimbescu et al produced a high-viscosity solution using CaCl 2 as an additive in the process of manufacturing aramid using terephthaloyl dichloride and para-phenylenediamine as monomers and pyridine as an acid scavenger [ 15 ]. However, since such inorganic salts become impurities in the final product especially for the production of films, they must be removed by washing.…”

Carbonyl-rich porous organic polymers for cobalt adsorption from water

“…A polymerization using a 1 : 1 ratio of amine groups to acyl chloride groups should result in an amide-linked polymer with an equal number of amine end groups and carboxylate end groups. [39][40][41][42] By changing the monomer stoichiometry, we anticipated an uneven end group population between the amines and carboxylates. Our polymer naming scheme refers to the stoichiometric equivalents of acyl-chloride groups in the synthesis, relative to 1 equivalent of amino groups (Table 1).…”