Poly(p‐Phenylenebenzobisoxazole) fiber with polyphenylene sulfide pendent groups

Abstract

Poly(p‐phenylenebenzobisoxazole) (PBO) fiber with polyphenylene sulfide (PPS) pendent groups was made to improve PBO fiber compressive strength by crosslinking. PPS moieties allowed the polymeric network to crosslink at heat‐treatment temperatures at which PBO does not thermally degrade. PBO‐PPS fiber heat‐treated for 30 s at 600°C did not dissolve or break up in methanesulfonic acid. Compressive strength of crosslinked fiber was about 20% better than that of unmodified PBO fiber. In another experiment, 10 mol % of 2,5‐diphenylsulfideterephthalic acid was incorporated into PBO fiber. The side chain of one phenyl sulfide unit was too short to enhance crosslinking, and the fiber had about the same compressive strength as unmodified PBO fiber. © 1995 John Wiley & Sons, Inc.

Rigid‐Rod Polymers: Synthesis, Processing, Simulation, Structure, and Properties

“…The cracking phenomenon would appear to be a function of internal stress generation and morphological heterogeneity. A similar phenomenon may also be playing a role in the reported decrease in tensile properties of analogous systems 222–225. The observation of a non‐fibrillar morphology226 in free annealed MePBZT fiber, can be interpreted as indication of inter‐ as well as intra‐fibrillar crosslinking; however, chain degradation has also been mentioned as a possible factor for this change in morphology227 as well as for the decrease in tensile strength.…”

Preparation of multiwall carbon nanotubes/poly(p‐phenylene benzobisoxazole) nanocomposites and analysis of their physical properties

“…1) is prepared by polycondensation of 4,6‐diamionophenol dihydrochloride(DADHB 2HCl) and terephthalic acid in PPA (poly (phosphoric acid)) 1. So Ying‐Hung et al2 proposed the mechanism for PBO polymerization, that is, both chain ends were capped with DADHB, and the structure of the PBO oligomer is shown in Figure 2(b).…”

“…This relatively poor axial compressive strength of PBO is mainly ascribed to the weak lateral interactions between the molecules. Until now, a lot of research efforts8–10 have been expended in attempting to improve the fiber compressive strengths. Most of the methods have been aimed at modifying the molecular structures to improve the interactions between the chains by introducing hydrogen bonding and disrupting chain packing.…”

Synthesis of Heterocyclic Aramid Fiber Based on Solid‐Phase Cross‐Linking of Oligomers with Reactive End Group

“…In addition, random distribution of cross‐linking sites in macromolecular chains made cross‐linking less controllable, which resulted in instability of structure and properties. Similar methods have been carried out on poly( p ‐phenylene‐benzothiazole) (PBT) and poly( p ‐phenylene‐benzobisoxazole) (PBO) and the same problem was observed . So all these effects must be considered for cross‐linking of aramid at high temperature.…”