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ABSTRACT:In the present study, ethylene/vinyl alcohol (EVAL) copolymers with different hydroxyl contents were melt mixed with styrene/maleic anhydride (SMA) copolymers. These two copolymers have functional groups capable of reacting intermolecularly, giving stable products. All EVAL copolymers were prepared from the same ethylene/vinyl acetate (EVA) copolymer by controlled hydrolysis. The blends, prepared at constant temperature and rotation speed in the rheomixer, were characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis, as well as mechanical properties and extraction experiments. All the above measurements lead to the conclusion that a certain part of hydroxyls of EVAL have reacted with anhydride groups of SMA, leading to the formation of branched and crosslinked products. The effect of (1) the molar ratio of hydroxyl/maleic anhydride functional groups, (2) the overall concentration of the functional groups, and (3) the mixing time on the structure and properties of the blends are discussed. Emphasis is given on the influence of these factors on the tensile strength, the elongation at break, and impact strength of the products.

P2PSIP is a protocol for managing multimedia sessions in a distributed architecture, where all participating nodes share and manage network resources like bandwidth and disk space. This paper presents threats associated with P2PSIP protocol and proposes protocol enhancement to mitigate possible attacks. These extensions have been designed for the leading draft of P2PSIP overlay management protocol, RELOAD.. This paper proposes the use of Public key cryptography communication encryption, while symmetric cryptography is only used for peer authentication. The Public/Private Key (PPK) pair of each peer is refreshed based on a timer threshold, for the system to become even more robust. Through experimentation from a testbed, it is demonstrated that the overhead in terms of CPU load didn't exceed 3% in both peak and average evaluation cases.