ICF100500PR INTRODUCTION Reinforcement of thermoplastics polymer like PET fibres/PMMA matrix composite results in a material with some improved characteristics such as low embrittlement, stability and high mechanical strength. In addition, the specific gravity of the PET fibres is 1,29 g/cm3 less, which makes possible to produce a composite material with good mechanical properties and low specific mass. Conversely, it was recognised that the chemical inertness and the low surface energy of the PET fibres will make it difficult to achieve the adequate bond with a polymer to produce the composite[1-2]. The plasma treatment can be effective to improve the interfacial adhesion of the thermoplastics based composites[3]. By using excited-state chemistry in corona discharge, a number of polymers were modified before painting, printing and lamination[4]. Generally, oxidation on the fibre surface etched results in an increase in interfacial bond strength[5]. Gao and Zeng[6] concluded that the adhesion increases by at least four time by plasma treatment and, also, a slight decrease in the surface energy of the treated monofilaments with ageing time is observed. Because of this attractive attributes, plasma treatment of the fibre surface has been considered the prime technique for the control of adhesion in composites. However, the time of treatment is an important parameter to be considered because when it is long the fibers can be degraded and have their mechanical properties reduced. For the plasma treatment, no real increase in pull strength with treatment time was obtained for more than 510s[7]. In another work, it was observed that treatment time longer than 180s with argon plasma causes heavy degradation on the poly(tetrafluoroethylene) fiber surface[8]. In this work three different treatment times, 5s 20s, and 100s were used to obtain the adhesion improvement, by objecting, specifically, a treatment time with which there is an increase of the superficial energy without further degradation of the fibers. The oxygen and argon plasma were used to treat the PET in order to promote a perfect interfacial adhesion with the matrix. The experimental design was performed by pull-out test in order to investigate the adhesion of the interface PET/PMMA. SEM analysis of the pull-out specimens after oxygen and argon plasma treatment were realised. EXPERIMENTAL Materials The polymethyl methacrylate resin was polymerized from the methyl methacrylate monomer by a thermal polymerization at 100ºC. The polyethylene therephthalate (PET) fiber provided by Montefiber SpA (Acerra, 2
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