Thermal analysis of Vectran® fibers and films

Abstract

Vectra | liquid crystalline polymers (LCP's) were introduced as commercial products in the mid-1980's. The first of these (Vectra A130) was a wholly aromatic thermotropic copolyester of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid. Vectra A130 is a thermotropic LCP that can be melt spun into filaments that on heat treatment are characterized by high strength and high modulus. Vectra resin can also be extruded into films. In the fiber or film form this material is commercially known as Vectran | Heat treatment enhances the tensile strength of Vectran fiber variants. Because of this, the elucidation of the physical transformations taking place in the internal structure of the material during heating has always been an important subject. Several thermal techniques are used to indicate clearly that what is observed as a "glass transition" is unlike the conventional glass transition in typical semicrystalline polymers. There is also an indication of the presence of multiple states of mesophase aggregation that collapse into a single state when taken to high enough temperatures.

Combined effects of kink bands and hygrothermal conditioning on tensile strength of polyarylate liquid crystal co-polymer and aramid fibers

“…chain slippage and the failure of entanglements to transmit the load along the filament). 7,8 Conclusions…”

Liquid crystalline single-polymer short-fibers composites

“…As reported in previous studies, Tm 1 could be attributed to inter-chain transesterification reactions. [13,17,18] When the treatment was performed at 300°C, Tm 1 overlaps the endothermic peaks Tp 1 and Tp 2 present in the untreated fibers become the new transition temperatures of the fibers. Due to a largest increment in Tm 1 temperature, 300°C was chosen as heat-treatment temperature.…”

“…Interfaces 289 [15,17,18] After the thermal annealing treatment, a new endothermic peak (Tm 1 ) appears at a temperature increasing with the annealing temperature. As reported in previous studies, Tm 1 could be attributed to inter-chain transesterification reactions.…”

Liquid crystalline organic fibres and their mechanical behaviour

“…12.56. The effect of temperature on the mechanical properties of HBA/HNA copolymer and Vectran fibres can be better understood by considering their dynamic mechanical behaviour (Wellman et al, 1981;Eichenauer and Kjung, 1992;Menczel et al, 1997). As depicted in Fig.…”