Grafting of N-carbamyl maleamic acid onto a styrene-butadiene-styrene copolymer

Abstract

A styrene-butadiene-styrene block copolymer (SBS) was functionalized with N-carbamyl maleamic acid (NCMA) using two peroxide initiators with the aim of grafting polar groups onto the molecular chains of the polymer. The influence of the concentration of benzoyl peroxide (BPO) and 2,5-dimethyl, 2,5-diterbuthylperoxihexane (DBPH) was studied. The concentration of peroxy groups ranged between 0.75 and 6 × 10-4 mol % while the concentration of NCMA was constant at 1 wt %. The reaction temperature was chosen according to the type of peroxide employed, being 140°C for BPO and 190°C for DBPH. FTIR spectra confirmed that NCMA was grafted onto the SBS macromolecules. It was found that the highest grafting level was achieved at a concentration of peroxy groups of about 3 × 10-4 mol %. Contact angle measurements were used to characterize the surface of the SBS and modified polymers. The contact angle of water drops decreased with the amount of NCMA grafted from 95°, the one corresponding to the SBS, to about 73°. T-peel strength of polymer/polyurethane adhesive/polymer joints made with the modified polymers was larger than those prepared with the original SBS. The peel strength of SBS modified with 1.5 and 3 × 10-4 mol % of peroxy groups from BPO were five times larger than that of the original SBS. The materials modified using BPO showed peel strengths higher than the ones obtained with DBPH.