Preparation of poly(p-phenylene terephthalamide) in a microstructured chemical system

Abstract

A microstructured chemical system, mainly including a micro-sieve mixer, a delay loop and a stirring tank, was designed to implement the polycondensation of p-phenylenediamine (PPD) and terephthaloyl chloride (TPC) for the preparation of poly(p-phenylene terephthalamide) (PPTA). A two-step method was exhibited, which consisted of fast conversion of more than 90% reactive groups in the delay loop and further chain growth in the stirring tank. This new polycondensation method had several advantages, such as continuous operation at higher temperature and out of pyridine, which made the process more controllable and environmentally friendly. PPTA particles with weight-average molecular weight (MW) from 4,000 to 16,000 were obtained at different synthesis conditions, and their structures were characterized by XRD, POM, IR, EA and SEM. The apparent reaction kinetics in the delay loop was also studied, which showed that the apparent activation energy was 12 kJ/mol with a pre-exponential factor of 5.4×10 3 L/(mol·s).

Kinetic Study of Reactions of Aniline and Benzoyl Chloride Using NH3 as Acid Absorbent in a Microstructured Chemical System

“…Kinetic study of the reactions between aniline (AL) and benzoyl chloride (BC) is of significant importance for it reveals the intrinsic rules of reactions between aromatic amines and aromatic acid chloride, which have been widely applied in the fields of organic synthesis and polymerization process, for example, synthesis of intermediates for the production of insecticides, spice, and medicine, , and preparation of aramid fibers. , As a significant reaction, the kinetic study of the reactions between aniline and benzoyl chloride has attracted wide interest of researchers. − Borkent et al studied the effect of substituents of the aromatic amines and acid chloride in the reactions using a stopped-flow spectroscopy method in hexamethylphosphoric triamide, but the kinetic parameters might not be very accurate since five parameters were estimated from a single curve as the author admitted. Wamer et al studied the kinetics and mechanism of the reactions in a two-phase system of aqueous aniline and benzoyl chloride in chloroform .…”

Aqueously soluble semi‐aromatic copolyamides with dual‐functional groups as sizing agent

“…Kevlar fibers, one of its representative products, which are spun from the liquid crystalline solution of poly(p‐phenylene terephthalamide) (PPTA) in concentrated sulfuric acid, display outstanding mechanical property, high‐thermal stability, and good flame retardancy because of the high orientation of polymer chains, strong intermolecular hydrogen bondings, and symmetric chemical structure. These characteristics enable them wide applications in military, aeronautics, astronautics, and automobiles . Regardless of those excellent properties, the harsh processing condition remains an unresolved challenge because of the poor solubility, high‐melting point, and glass‐transition temperature of PPTA .…”

Synthesis and properties of poly(p-phenylene terephthalamide) bearing both polar and unsaturated substituents introduced via claisen rearrangement reaction

“…Because of the rigidity, symmetry, and intermolecular H‐bonding of polymer chains, PPTA can be spun into highly oriented fibers with excellent thermal stability, high chemical resistance, low flammability and exceptional tensile strength and modulus from liquid‐crystalline solution in concentrated sulfuric acid . The representative product, that is, Kevlar, has been comprehensively studied and widely applied in many fields such as military, aeronautics, astronautics, and automobiles . Kevlar and other aramid fibers have been frequently employed as reinforcing materials to fabricate high performance rubber and epoxy‐based composites.…”

“…1,2 The representative product, that is, Kevlar, has been comprehensively studied and widely applied in many fields such as military, aeronautics, astronautics, and automobiles. [3][4][5][6] Kevlar and other aramid fibers have been frequently employed as reinforcing materials to fabricate high performance rubber and epoxy-based composites. However, the inferior interfacial affinity toward matrices due to the smooth surfaces and chemical inertness of fibers hinders the full achievement of their potential.…”