Adhesion of maleic anhydride functionalized polyolefins and blends



We study three new classes of olefin-based polymer, low-molecular-weight homopolypropylene (LMW-hPP), syndiotactic-rich polypropylene (srPP), and random propylene polymer (RPP). RPP is a random propylene/ethylene copolymer. By blending LMW-hPP with 20 wt % of a maleic anhydride (MA) functionalized srPP (MA-srPP) or MA functionalized RPP (MA-RPP) instead of a commercial MA-iPP (maleic anhydride-grafted-isotactic polypropylene), adhesion to a polar substrate, such as polyester (Mylar), is greatly enhanced. Effects of crystallinity controlled by either stereoregularity or comonomer incorporation and molecular weight of these MA functionalized propylene-based polymers on adhesive performance are discussed. To further understand the mechanisms of enhanced adhesion, Sum Frequency Generation (SFG) spectroscopy is used to evaluate the migration of MA-srPP in LMW-hPP towards the interface when contacting a polar sapphire substrate. It shows that the buried interface between the LMW-hPP/MA-srPP blend (wt ratio = 80/20) and sapphire has the same characteristic spectrum as the MA-srPP/sapphire interface, suggesting the enrichment of MA-srPP in the interfacial polymer when the blend is in contact with sapphire. Also, vibrational modes of C=O have been detected at both the blend/sapphire and MA-srPP/sapphire interfaces, further indicating that the interfacial polymer contains MA groups. Besides Mylar, adhesion to the non-polar iPP substrate is also studied. The adhesion mechanisms to these polar and non-polar substrates are explained in terms of our adhesion model. Applications of these MA functionalized polyolefins and blends are envisioned in the tie-layer and adhesive areas. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39855.