Enzymatic Modification of Polyamide for Improving the Conductivity of Water-Based Multilayer Nanocoatings

Abstract

Enzymatic modification, using a protease from Bacillus licheniformis (Subtilisin A), was carried out on polyamide 6.6 (PA6.6) fabric to make it more amenable to water-based nanocoatings used to impart electrical conductivity. The modified PA6.6 fibers exhibit a smoother surface, increased hydrophilicity due to more carboxyl and amino groups, and larger ζ-potential relative to unmodified polyamide. With its improved hydrophilicity and surface functionality, the modified textile is better able to accept a water-based nanocoating, composed of multiwalled carbon nanotubes (MWCNT) stabilized by sodium deoxycholate (DOC) and poly(diallyldimethylammonium chloride) (PDDA), deposited via layer-by-layer assembly. Relative to unmodified fabric, the enzymatically modified fibers exhibit lower sheet resistance as a function of PDDA/MWCNT-DOC bilayers deposited. This relatively green technique could be used to impart a variety of useful functionalities to otherwise difficult-to-treat synthetic fibers like polyamide.

Flame suppression of polyamide through combined enzymatic modification and addition of urea to multilayer nanocoating

“…This improved performance from enzymatic modification of PA 6.6 is believed to be due to increased hydrophilicity, from the additional carboxyl and amino groups, and the resulting increased surface charge relative to the unmodified fabric. This greater hydrophilicity and surface charge improve the ability of the modified fabric to accept a water-based, functional nanocoating and to gain more weight with fewer bilayers deposited [34]. Mass loss and rate of mass loss as a function of temperature for coated polyamide are shown in Fig.…”

“…1. Before LbL deposition, the PA 6.6 fabric was enzymatically modified in a bath with a 30:1 liquior ratio (LR) at pH 6.8 (0.1 M phosphate buffer), using 10% by weight of the fabric protease enzyme at 60°C for 60 min, according a previously reported procedure [34]. The fabric was then immersed into the APP solution for five minutes and subsequently rinsed in DI water for one minute.…”

“…It was also included in a polyethylenimine (PEI) solution and combined with APP for layer-by-layer deposition onto nylon/cotton fabric [33]. Previous work has demonstrated that enzymatic modification is an effective process for achieving good hydrophilicity on the surface of PA 6.6 fibers that is responsible for more effective deposition of a multilayer nanocoating [34]. This work presents the LbL deposition of an ammonium polyphosphate/chitosan intumescent system, in combination with the gas-phase active small molecules thiourea (THU) and urea (U), on the surface of enzymatically modified PA 6.6 fabric.…”

Enzymes Involved in Plastic Degradation

“…Recently,a protease from Bacillus sp. has been shown to hydolyze both PA 6 and PA 6,6 [65]. This particular protease functions optimally between 25-30 o C at pH 8 under agitatiom.However, protease and lipase enzymes are normally used to modify and improve PA physical and chemical properties such as hydrophilicity while smoothing the surface [65,66].…”

New Approaches of Biotechnology in Textile Coloration

“…The hydrophobicity nature of synthetic polymers as polyamide (PA) and polyester (PET) make them uncomfortable to wear. [34] Sodium hydroxide was used in the traditional chemical process to improve the hydrophilicity and flexibility of the synthetic textile but due to the increase in weight loss and yellowing of fibers, this process was unacceptable. Many proteases enzymes with a different commercial name such as Protex Gentle L, were used to induce changes in the nylon 6,6 polymer.…”