Modification of polyamide 6.6 dyeing properties by grafting with poly(acrylic acid) Miranda, T, Santos, J, Soares, G. M. B. 2C2T – Centre for Textile Science and Technology; Department of Textile Engineering; Minho University, 4800-058 Guimarães, Portugal gmbs@det.uminho.pt Abstract The wet chemical surface modification continues to be a growing area of research interest. This study describes preparation and characterization of poly (acrylic acid)-grafted polyamide 6.6 fabric. Poly (acrylic acid) has been grafted onto polyamide backbone using benzoyl peroxide (BPO) as catalyst in aqueous medium. The benzoyl peroxide initiator optimum concentration was 0.03 M. The best conditions for optimum grafting reaction were reaction time 120 min, grafting temperature 85°C, monomer concentration 0.5 M and BPO concentration 0.03 M. The grafting rate was evaluated gravimetrically. The maximum grafting percentage obtained was 13.3%. All samples were characterized by Fourier–transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR). The influence of acrylic acid grafting onto polyamide 6.6 was studied in terms of dye uptake using a basic dye, Rouge Maxilon GRL. Mechanical properties were also analysed. Keywords: Graft copolymerization, Polyamide 6.6 fabric, dyeing properties 1. Introduction The modification of polymers continues to receive a lot of attention from the scientific community. Its popularity is due to the fact that it allows obtaining materials with new functionalities without requiring specialized equipment 1 . Among all the methods of modification, grafting is one of the most promising processes. Graft copolymerization is mainly an attractive method to impart a variety of functional groups on polymers 2 . Grafting reaction involves the copolymerization of a monomer onto the polymer backbone. The formation of copolymers from several natural and synthetic polymers by graft copolymerization has been widely studied 3-5 . This work describes the preparation and characterization of poly (acrylic acid)-grafted polyamide 6.6 fibers. The acrylic acid (AA) has been grafted onto polyamide 6.6 (PA 6.6) backbone using benzoyl peroxide (BPO) as initiator in aqueous medium 4 . The hydrophobic nature of the semi – crystalline polyamide 6.6 fibers with low presence of carboxylic groups, results on a poor dyeability with basic dyes. The grafting rate depends on AA concentration, BPO concentration, time and temperature of the reaction. Makhlouf and collaborators studied the best conditions for same grafting reaction and they found out that those were 0.5 M of AA, 0.03 M of BPO, reaction time of 120 min and grafting temperature of 85°C 4 . Previous studies showed that the acrylic acid grafting increased the carboxyl groups on the polyamide 6.6 fibers, which improves their hydrophilic properties and ability to be dyed with Red Astrazon 5BL basic dye 6 . In the present study, the modified polyamide 6.6 samples were characterized by the use of FTIR-ATR techniques and they were comparatively analyzed in terms of dye uptake and mechanical properties. 2. Experimental 2.1 Materials The acrylic acid (AA) monomer (VHR International) and a Rouge Maxilon GRL dye (Huntsman, Portugal) were used without previous purification. Polyamide 6.6 fabric was purchased from Lameirinho, Portugal. 2.2 Methods In order to achieve a better initiator and monomer’s diffusion in polyamide 6.6 surface during grafting reaction, samples must be