The effect of coagulant on the structure and properties of poly(p‐phenylene benzobisthiazole) fibers [PBZT]

Abstract

SynopsisFibers spun from anisotropic solutions of a lyotropic rigid-rod polymer, poly ( para-phenylene benzobisthiazole) [ PBZT] , were coagulated into homogeneous nonsolvents including a solution of 18% iodine/82% ethanol, ethanol, and water. The effect of these coagulants on the structure and mechanical properties of the PBZT fibers was studied. Structural and mechanical studies were performed on as-spun fibers. Wide-angle X-ray diffraction techniques have shown that fibers coagulated in the presence of iodine anions had d-spacings that were unique, as well as d-spacings that were characteristic of PBZT or iodine anions. Tensile and shear properties were highest in a fiber having a spin/draw ratio of 3 which contained 19.5% iodine species by weight. For these fibers, an average tensile strength of 2.2 GPa and a torsional modulus of 1.14 GPa was recorded. For fibers having this spin/draw ratio, and undergoing no post-processing heat treatment or tension drying, these values are much higher than would be expected.

Effects of different coagulation conditions on polyacrylonitrile fibers wet spun in a system of dimethylsulphoxide and water

“…The spinnability is affected not only by the properties of the spinning solution but also by the coagulation bath conditions. [1][2][3][4][5][6][7][8][9] Various factors that influence the coagulation process including the polymer composition, molecular weight, and its distribution of polymer, respectively, were explained by Paul and Mcpeters 10 and Han and Segal, 11 and Takahashi et al 12 The effect of coagulation bath composition on the structure of as-spun fibers was reported by Knudsen. 13 Recent investigations that used modeling techniques to understand diffusion processes have been reported by Baojun et al 14 and Alieva et al 15 Determination of diffusion coefficient of DMSO in polyacrylonitrile (PAN) fiber formation has been reported by Chen and coworkers. 16 But, an important feature of the coagulation process of solutions is that a distinct moving boundary is associated with the coagulation.…”

Liquid crystalline organic fibres and their mechanical behaviour

“…Nevertheless, other coagulation baths (such as dilute phosphoric acid solution, MSA aqueous solution, methanol, ammonium hydroxide and iodine/ethanol solution) were considered. From a general point of view, the composition and temperature of the coagulation bath influence the structure and mechanical properties of the fibres (Choe and Kim, 1981;Rakas and Farris, 1990). The importance of the coagulation bath was shown by the non-aqueous coagulation system developed by Toyobo (Kitagawa et al, 1999.…”

Rigid‐Rod Polymers

“…Different coagulants, including cool water, dilute PPA, methanol, and NH 4 OH have been used (120). During coagulation, the acid diffuses out of the fiber and about 90% of the solvent is removed (121).…”

“…The composition, pH, and temperature of the coagulation bath affect the structure and properties of the fibers. In general, slower coagulation rates lead to higher tensile modulus and strength of the fibers (123). Slow coagulation also helps the formation of cocrystals of the polymer and solvent.…”

“…A low nucleation density of crystal solvates results in a lamellar structure, and a high nucleation density leads to microfibril structure (122). For PBZT fibers, different compositions of the coagulation bath, such as iodine/ethanol solution, exhibit a measurable effect on fiber structure and properties (123,124).…”