Bulk and nano mechanical properties of surface modified Polypropylene films with Acrylic Acid as grafting agents

FASCE L.; SUAREZ M.P; PETTARIN V.; VANINA C.; STRUMIA M.

Annual Technical Conferences ANTEC. Conference Proceedings

Año: 2007 p. 1675 - 1679

ABSTRACT   Modification of PP films through a grafting technique is considered to be one of the main routes to adapt polypropylene to several kinds of applications by adding extra functions while keeping its desired bulk characteristics. Through this paper biaxially oriented commercial films of polypropylene were modified by photo inducing graft copolymerisation of acrylic acid with ultraviolet radiation at room temperature using benzophenone as the initiator. The percentage of grafting was determined by gravimetric measurements and the chemical characterization of the grafted films was carried out by IR analysis. Scanning electronic and atomic force microscopy were used to study the topography of the modified films. Thermal, optical, transport properties and the change in wettability of the grafted products were evaluated by DSC, light transmittance, water permeation and contact angle measurements respectively. Uniaxial tensile deformation and fracture-mechanics tests were performed on the two main draw directions, i.e., the machine-direction (MD) and the transverse-direction (TD). Impact performance was assessed via  biaxial impact tests . The effect of grafting  on the surface mechanical properties has been investigated by the nanoindentation technique. This technique offers an approach to determine the elastic modulus and hardness of the surface which are difficult to be obtained by other methods. The non-degradation of bulk mechanical properties and the generation of a stress-free chemically modified film surface by grafting were demonstrated.