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DMA analysis of the structure of crosslinked poly(methyl methacrylate)s

Barszczewska-Rybarek I. M., Korytkowska-Wałach A., Kurcok M., Chladek G., Kasperski J.

Acta of Bioengineering and Biomechanics

2017

Vol. 19, no. 1

47--53

Purpose: This paper presents the study aimed at the development of crosslinked poly(methyl methacrylate)s (X-PMMA) of varied crosslink density and the investigation of the relationships between the polymer network structure and dynamic mechanical properties. Methods: A series of model X-PMMA networks were crosslinked by the introduction of: 1, 2, 5, 10 and 20% of triethylene glycol dimethacrylate (TEGDMA). The copolymerizations led to various glass-rubber relaxation properties of the polymer networks, as revealed by dynamic-mechanical analysis (DMA). Glass temperature (Tg) and storage modulus above the Tg ( ) Erubbery  were a sensitive function of network architecture. DMA data were used for calculating the network parameter (Mc), crosslink density (q) and its alternative measure – the degree of crosslinking (DX). Results: The viscoelastic properties as well as structural parameters calculated from those showed correlation with the amount of the crosslinker. The increase in TEGDMA content resulted in the Tg, q and DX increases, whereas Mc decrease. The possible incomplete conversion of double bonds was detected in the DMA analysis, which was confirmed by the degree of conversion (DC), measured by FTIR spectroscopy. Additionally, some amount of sol fraction was found by 1H NMR experiments. Conclusions: The structure-property relationships developed for the system presented in this work could be useful in tissue engineering, where X-PMMA is applied. The direct measure of storage modulus values before and above glass transition may serve as a simple and fast indicator of the X-PMMA crosslink density.

Badania wpływu parametrów sieciowych na jakość transmisji multimedialnej w sieci testowej

Szlęzak M., Zakrzewski T.

Studia Informatica

2003

Vol. 24, nr 3

161-169

Referat przedstawia problematykę wpływu parametrów sieciowych na jakość transmisji dla najbardziej istotnych elementów spotkania multimedialnego, jakimi są obraz i dźwięk. Artykuł prezentuje kryteria obiektywnej i subiektywnej oceny jakości transmisji w sieci Internet. Wyniki otrzymane z przeprowadzonych doświadczeń w sieci testowej z wykorzystaniem narzędzi do transmisji multimedialnej prezentują wpływ wybranych parametrów sieciowych na jakość transmisji po stronie odbiorczej. W referacie przedstawiono problemy napotkane przy realizacji doświadczenia i propozycje ich rozwiązania.

This paper describes the network parameters influence on the multimedia transmission quality. The authors concentrate on main elements of videocon-ference meeting, which are video and voice streams. Article shows objective and subjective criteria used to estimate transmission quality in computers networks, in particular in the Internet. The influence of selected network parameters on received data quality was tested in an experimental network with use selected videoconference tools. The results of performed experiments, as well as the difficulties met during experiment and proposed solutions, are presented.