Stimuli Sensitive Behaviour of Modified Polyacrylonitrile Fibres

A series of copolymers based on acrylonitrile (AN) and acrylic acid (AA) with varying architecture and composition were synthesized using free radical polymerization. The distribution of monomers in the copolymer chains could be successfully controlled by regulating the addition of more reactive monomer (AA). Copolymers having nearly random distribution of comonomer moieties to block type distribution with different composition (10-50 mol % AA) were synthesized to investigate the effect of polymer architecture and composition on pH response and mechanical properties of resultant structures. These copolymers were solution spun from dimethylformamide-water system, drawn in coagulation bath, and annealed at 1208C for 2 h to make pH-sensitive fibers which were structurally stable without the need of chemical crosslinking. The fibers from block copolymers showed significantly better tensile strength (34.3 MPa), higher retractive forces (0.26 MPa), and enhanced pH response (swelling 3890%) in comparison with fibers from random copolymer (13.55 MPa, 0.058 MPa, and 1723%, respectively). The tensile strength and retractive forces could be further improved to a value of 72 MPa and 0.36 MPa, respectively, by changing the composition of the block copolymer while retaining the swelling percentage similar to the random copolymer mentioned above. It is proposed that on processing to fibers, the block copolymers could form a segregated domain structure with separate domains of AA and AN, where AN domains were responsible for high structural integrity by providing connectivity among polymer chains, while AA domains showed improved response to changing pH of the environment.

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“…In another approach, [15][16][17][18][19] the existing poly(acrylonitrile) were modified to produce pH-sensitive fibers.…”

Section: Introductionmentioning

confidence: 99%

Influence of the copolymer architecture and composition on the response and mechanical properties of pH‐sensitive fibers

Sahoo

Jassal

Agrawal

2007

J of Applied Polymer Sci

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“…known to exhibit a significant mechanical response to chemical or thermal stimuli . For instance, some hydrogels strongly expand (contract) in response to a change in pH of the environmental solution [21][22][23][24][25][26][27][28][29][30]. This expansion/contraction behavior is similar to the spontaneous motion of human muscles.…”

Section: Introductionmentioning

confidence: 92%

An investigation on actuation behavior of polyacrylonitrile gel fibers as a function of microstructure and stabilization temperature

Mirbaha

Arbab

Zeinolebadi

et al. 2013

Smart Mater. Struct.

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Polyacrylonitrile (PAN) gel fibers show great potential to be used as actuators due to their mechanical response to chemical stimuli. In this work the response of PAN gel fibers to pH variation is studied. Three commercial grade PAN fibers with different chemical composition are investigated. Fibers are stabilized at temperatures varying from 100 to 275 °C. The stabilized fibers are hydrolyzed in an alkaline solution to obtain gel fibers. Gel fibers are stepwise immersed in solutions with pH varying between 0 and 14. Length/diameter variations are measured by optical microscopy. Results suggest that there is an optimum stabilization temperature at which a maximum response to pH change is obtained. This temperature corresponds to the onset of cyclization reactions, and is determined by the chemical composition of starting material. Thus at low stabilization temperatures (T ≤ 200 °C) only a gel-like shell is formed on the surface of fibers. Fibers stabilized above 200 °C show significant length/diameter variations (up to 325%). Increasing the stabilization temperature above the optimum temperature weakens the response of fibers to pH change. The results also show that the actuation behavior of PAN fibers containing itaconic acid starts at lower stabilization temperatures. This is attributed to the effect of acidic groups in lowering the onset of cyclization reactions.

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“…Structurally, the aramid fibers are classified into two categories: one is meta linked (m‐aramid) and the other is para linked (p‐aramid). Nowadays, both these aramid fibers are commercially available in the market under different trade names like Kevlar, Twaron, Conex, Nomex and Technora . For many years different types and forms of aramid fibers have been used to reinforce different elastomers and thermoplastic elastomers (TPEs) to improve various properties .…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2018

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Composites based on brominated isobutylene‐isoprene rubber (BIIR) and 5‐mm short aramid fiber were prepared by varying the fiber content from 1 to 10 phr using 4, 4’ bismaleimido diphenyl methane (BMDM) and zinc oxide as the vulcanizing agent. Morphological analysis revealed that the fiber dispersion becomes inferior even at 5 phr loading due to fibrillation during mixing. As a result, the 10 phr fiber‐filled composite showed a brittle failure under a tensile deformation. To solve this problem, maleic anhydride‐grafted polybutadiene (MA‐g‐PB) resin was treated with the aramid fibers in the 1:1 ratio prior to mixing with the rubber matrix. Excellent fiber dispersion could be seen in both the visual image of the molded sheet and the scanning electron microscope image of the fractured surface. The stress–strain curve of the 10 phr fiber‐filled composite after the resin treatment showed a tough deformation behavior with a breaking elongation >100% indicating an enhanced fiber‐matrix adhesion. From the vulcanization studies of the fiber‐filled BIIR before and after the MA‐g‐PB resin treatment, it has been identified that a co‐crosslinking reaction between the MA‐g‐PB‐treated fiber and the BIIR matrix with BMDM via Alder‐ene and Diels‐Alder reactions is responsible for the enhanced fiber–matrix adhesion. POLYM. COMPOS., 40:2993–3004, 2019. © 2018 Society of Plastics Engineers

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Stimuli Sensitive Behaviour of Modified Polyacrylonitrile Fibres

Cited by 7 publications

References 18 publications

Influence of the copolymer architecture and composition on the response and mechanical properties of pH‐sensitive fibers

Influence of the copolymer architecture and composition on the response and mechanical properties of pH‐sensitive fibers

An investigation on actuation behavior of polyacrylonitrile gel fibers as a function of microstructure and stabilization temperature

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

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