Microstructural developments of poly (p-phenylene terephthalamide) fibers during heat treatment process: a review

Abstract

Poly (p-phenylene terephthalamide) fibers prepared by wet or dry-jet wet spinning processes have a notable response to very brief heat treatment (seconds) under tension. The modulus of the as-spun fiber can be greatly affected by the heat treatment conditions (temperature, tension and duration). The crystallite orientation and the fiber modulus will increase by this short-term heating under tension. Poly (p-phenylene terephthalamide) fibers have a very high molecular orientation (orientation angle 12-20°). Kevlar  and Twaron  fibers are poly (p-phenylene terephthalamide) fibers. This review reports for PPTA fibers the heat treatment techniques, devices and its process conditions. It reports in details the structural relationships between the fiber properties which are influenced by the heat treatment process. In particular, focused deeply on the effect of the crystal structure and the morphology of the fibers on the mechanical properties of PPTA fibers.

Molecular Dynamics Modeling of PPTA Crystals in Aramid Fibers

“…PPTA bers are typically used in applications where they are loaded in tension along the ber direction (as opposed to transversely), and as such, the most important and oft-reported mechanical properties are the longitudinal stiness and strength. Table 2.1 provides a summary of the tensile axial modulus and failure stress/strain of some dierent varieties of Kevlar and Twaron bers, as reported in the review article by Ahmed et al [2]. In conventional fibers such as nylon and poly(ethy1ene terephthalate) (PET) the long period is obtained from small-angle x-ray scattering.…”

“…Bundles of 60 nm diameter cylindrical crystallites were also observed in the fiber direction. If the fiber is stressed prior to etching, the cracks propagate in planes 600-800 nm apart [ 161, so the fibers have internal weak planes spaced 200 nm along the fiber, which correspond to the boundaries of the crystallites, and also defect planes occurring Table 2.1: Mechanical properties of various grades of PPTA ber, as reported in [2].…”

“…These remarkable properties have led to aramid bers being heavily used in projectile-resistant fabrics such as personal protective vests and helmets, jet engine enclosures, and ame-retardant clothing [2].…”

Investigating the glass transition temperature at the atom-level in select model polyamides: A molecular dynamics study

“…This stacking interaction is observed experimentally via both wide-angle X-ray scattering and differential scanning calorimetry (DSC) measurements in polymers, such as aromatic polyamides like poly(paraphenylene terephthalamide) [13], aromatic polyesters including polybutylene terephthalate [14] and polyethylene terephthalate [15], as well as in 4,4'-methylene diphenyl diisocyanate (MDI) based polyurethanes [16]. It was also noted that the diffraction patterns of the chain structure in a 4,4'-MDI-butanediol based polyurethane resembled the α-form crystalline structure of nylon 6,6 [17,18] The time and length scales accessible to all-atom molecular dynamics is on the order of nanoseconds and of angstroms, which is not sufficient to capture phenomenon such as phase separation and the formation of crystalline regions [20].…”

Enhancing the dispersion and adhesion of short aramid fibers in bromo‐isobutylene‐isoprene rubber using maleated polybutadiene resin via co‐vulcanization with 4, 4’ bis(maleimido)diphenylmethane

“…As a result, the interaction between the aramid fiber and the polymer matrix is generally weak. Therefore, various chemical and physical methods like acid treatments , bromination , polymer coating , polymer grafting , carbon nanotube grafting , heat treatments , plasma treatment , and so on have been practiced on the aramid fiber surface to improve its adhesion with the rubber matrix. In addition to the above‐mentioned methods, the use of coupling agents was also been employed to enhance the fiber‐matrix adhesion.…”