Polypropylene/polypropylene-grafted acrylic acid blends for multilayer films: Preparation and characterization

Polypropylene (PP) was functionalized with acrylic acid IAA) and styrene (s t) as a comonomer by means of a radical-initiated melt-grafting reaction. F TTR, ESCA, and H-1-NMR spectroscopies were used to characterize the formati on of polypropylene grafted with acrylic acid (PP-g-AA) and polypropylene g rafted with acrylic acid and styrene (PP-g-AAst). The content of AA grafted onto PP was determined by using volumetric titration. Blends of PP with 0- 100 wt % of PP-g-AA were prepared by melt mixing. The effect of the modifie d polymer content on the surfaces of cast films was characterized through F TIR-ATR and ESCA analysis as well as contact-angle, wetting tension, and in k-adhesion measurements. The influence of the content, of AA on the melting and crystallization temperature of PP was investigated by DSC. The contact angles of water on cast-film surfaces of PP/PF-g-AA blends decreases with increasing modified polymer content and decreasing PP-g-AA molecular weight . A notorious improvement on wetting tension was observed with increasing m odified polymer content and decreasing PP-g-AA molecular weight. From FTIR- ATR and ESCA spectra of the blends, a calculation was made of the carbonyl index on the films' surfaces. It was found that the higher the carbonyl ind ex, the lower the contact-angle value for the polypropylene blends. An incr ease in crystallization temperature of PP was observed when AA monomers wer e grafted into PP and with increasing PP-g-AA content in the blend, probabl y caused by a nucleation effect, of AA monomers that would improve the crys tallization capability of PP. (C) 2000 John Wiley & Sons, Inc.