CONICET | Buscador de Institutos y Recursos Humanos

In many applications it is necessary to change and/or to improve some of the polymeric surface properties without modifying the bulk properties of the material. This work deals with the evaluation of the effect of surface grafting on the bulk mechanical properties of commercial bi-oriented polypropylene films. Films of PP 32 ìm thick were surface modified by radical grafting polymerization initiated by UV light with acrylic acid as co-monomer. Samples were characterized by FT-IR, gravimetric and titration methods. Transparency was determined by light transmittance and hydrophobicity by contact angle determination. Mechanical tests, uniaxial and double edge notched tensile, were performed in various orientation directions at room temperature at 10 and 2 mm/min respectively, in an Instron testing machine coupled to a video extensometer. It was demonstrated by FT-IR, gravimetric and titration methods that grafting was actually achieved, in a percentage of about 13 %. Physical properties were highly influenced by surface modification. Light transmittance was reduced in 16%, and contact angle values were influenced depending on the solvent character. Mechanical properties, Young modulus (E) and yield stress (óy), were highly dependant on orientation, but did not exhibit noteworthy variations with surface grafting. A novel technique for fracture characterization of brittle polymer films based on J-integral approach was developed. Again, different values were obtained depending on the solicitation direction, but fracture values were not much affected by surface modification. ), were highly dependant on orientation, but did not exhibit noteworthy variations with surface grafting. A novel technique for fracture characterization of brittle polymer films based on J-integral approach was developed. Again, different values were obtained depending on the solicitation direction, but fracture values were not much affected by surface modification.