983 resultados para Polymer Science and Rubber Technology
Studies On Thermoplastic Elastomers With Special Reference To Triblock Copolymers And Nbr/Pvc Blends
Resumo:
Thermoplastic elastomers are a relatively new class of materials which compete with thermoset rubbers in some areas and thermoplastic materials in other areas. The main thrust of the present investigation is a comparative study’ on commercially .available triblock. styrene thermoplastic elastomers and those derived from blends of acrylonitrile-butadiene rubber and poly(vinyl chloride). The styrene—based thermoplastic elastomers are gaining acceptance as a replacement for both natural and synthetic rubber‘ in many‘ applications. TPEs based on blends of elastomers and plastics ix: the fastest growing segment of the broad class of thermoplastic elastomers. Broad applicability and simple technology of production are the attractive features of this class of TPES. NBR/PVC thermoplastic elastomers were selected for this investigation due to the versatility of PVC, its number one position, low cost. ability to Ina compounded into various flexible and rigid form with good physical and chemical and weathering properties etc., which will be passed over to PVC blends especially NBR/PVC blends which are known to form miscible systems
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In the present study, the photochemical depolymerisation of NR in toluene, in presence of H202 and a homogenizing solvent (Methanol/Tetrahydro— furan) so as to get hydroxyl terminated liquid natural rubber (HTNR) has been carried out. The copolymeri— sation of this product with butane 1,4 diol and toluene 2,4 diisocyanate in presence of a catalyst, dibutyl tin dilaurate, to produce polyurethanes with HTNR soft segments is also reported. The preparation of block copolymers based on poly(ethylene oxide) with varying molecular weights and HTNR are also discussed along with a detailed study on their thermal and mechanical properties
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Starve feeding of single screw extruder was described as an important means of improving the performance characteristics of the extruder. In addition to such improvement with versatility, the starve feeding technique also may affect the mechanical properties of the extrudate since the heat transfer an(l mixing characteristics in the starve fed and Hood fed extruders are not the same. Since the material is more loosely packed in the channels of the starve fed extruder, there may be greater bed mobility and uniformity. Further, the. thermal an(l shear induced degradation are also less since possibilities of developing local high temperatures are less compared to a densely compacted extruder bed. This study has been undertaken mainly to explore the effect of feeding rate on the mechanical properties of rubber and plastic extrudates since the effect of feeding rate has not been analysed from this angle so far.
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Earlier studies5773 in our laboratory showed that when a nucleophile is used along with disulphide or sulphenamide accelerators the vulcanization is accelerated greatly and the reaction mechanism is generally nucleophilic in nature. However it was observed that it also changes with the systems under review. The present study, deals with the use of unsubstituted amidino thiourea i.e. aminoimino methyl thiourea(AMT) V in the vulcanization studies of different elastorners and their blends. One of the aims of this study was to get further proof with regard to the theory of nucleophilic reaction mechanism in such binary systems.Mixes containing thiourea are used as controls. AMT is more nucleophilic than TU and this is clear from the fact that the fonner can condense with isothiocynate even in the absence of alkali while TU cannot". Also the guanidinyl group in AMT can facilitate the polarization of the C=S bond favouring a nucleophilic reaction
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In this lecture, we will focus on analyzing user goals in search query logs. Readings: M. Strohmaier, P. Prettenhofer, M. Lux, Different Degrees of Explicitness in Intentional Artifacts - Studying User Goals in a Large Search Query Log, CSKGOI'08 International Workshop on Commonsense Knowledge and Goal Oriented Interfaces, in conjunction with IUI'08, Canary Islands, Spain, 2008.
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Search engines - such as Google - have been characterized as "Databases of intentions". This class will focus on different aspects of intentionality on the web, including goal mining, goal modeling and goal-oriented search. Readings: M. Strohmaier, M. Lux, M. Granitzer, P. Scheir, S. Liaskos, E. Yu, How Do Users Express Goals on the Web? - An Exploration of Intentional Structures in Web Search, We Know'07 International Workshop on Collaborative Knowledge Management for Web Information Systems in conjunction with WISE'07, Nancy, France, 2007. [Web link] Readings: Automatic identification of user goals in web search, U. Lee and Z. Liu and J. Cho WWW '05: Proceedings of the 14th International World Wide Web Conference 391--400 (2005) [Web link]
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In this class, we will discuss metadata as well as current phenomena such as tagging and folksonomies. Readings: Ontologies Are Us: A Unified Model of Social Networks and Semantics, P. Mika, International Semantic Web Conference, 522-536, 2005. [Web link] Optional: Folksonomies: power to the people, E. Quintarelli, ISKO Italy-UniMIB Meeting, (2005)
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In this class, we will discuss the nature of network evolution and some selected network processes. We will discuss graph generation algorithms that generate networks with different interesting characteristics. Optional : The Structure and Function of Complex Networks (chapter 8), M.E.J. Newman, SIAM Review 45 167--256 (2003); Optional: Emergence of Scaling in Random Networks, A.L. Barabasi and R. Albert, Science 286, 509 (1999)
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In this class, we will discuss network theory fundamentals, including concepts such as diameter, distance, clustering coefficient and others. We will also discuss different types of networks, such as scale-free networks, random networks etc. Readings: Graph structure in the Web, A. Broder and R. Kumar and F. Maghoul and P. Raghavan and S. Rajagopalan and R. Stata and A. Tomkins and J. Wiener Computer Networks 33 309--320 (2000) [Web link, Alternative Link] Optional: The Structure and Function of Complex Networks, M.E.J. Newman, SIAM Review 45 167--256 (2003) [Web link] Original course at: http://kmi.tugraz.at/staff/markus/courses/SS2008/707.000_web-science/
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In this class, we will discuss the course organization and provide a basic motivation for and introduction to the course. Readings: Web science: a provocative invitation to computer science, B. Shneiderman, Communications of the ACM 50 25--27 (2007) [Web link] Readings: Chapter 1 & 2, A Framework for Web Science, T. Berners-Lee and W. Hall and J. A. Hendler and K. O'Hara and N. Shadbolt and D. J. Weitzner Foundations and Trends® in Web Science 1 (2006) [Web link] Originally from: http://kmi.tugraz.at/staff/markus/courses/SS2008/707.000_web-science/
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The semantic web represents a current research effort to increase the capability of machines to make sense of content on the web. In this class, Peter Scheir will give a guest lecture on the basic principles underlying the semantic web vision, including RDF, OWL and other standards.
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How can we analyze and understand affiliation networks? In this class, we will discuss properties of affiliation networks and we will investigate the use of Galois lattices for the exploration of structural patterns in bi-partite graphs. Optional : L.C. Freeman and D.R. White. Using Galois Lattices to Represent Network Data. Sociological Methodology, (23):127--146, (1993)
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What are fundamental entities in social networks and what information is contained in social graphs? We will discuss some selected concepts in social network analysis, such as one- and two mode networks, prestige and centrality, and cliques, clans and clubs. Readings: Web tool predicts election results and stock prices, J. Palmer, New Scientist, 07 February (2008) [Protected Access] Optional: Social Network Analysis, Methods and Applications, S. Wasserman and K. Faust (1994)
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We will discuss several examples and research efforts related to the small world problem and set the ground for our discussion of network theory and social network analysis. Readings: An Experimental Study of the Small World Problem, J. Travers and S. Milgram Sociometry 32 425-443 (1969) [Protected Access] Optional: The Strength of Weak Ties, M.S. Granovetter The American Journal of Sociology 78 1360--1380 (1973) [Protected Access] Optional: Worldwide Buzz: Planetary-Scale Views on an Instant-Messaging Network, J. Leskovec and E. Horvitz MSR-TR-2006-186. Microsoft Research, June 2007. [Web Link, the most recent and comprehensive study on the subject!] Originally from: http://kmi.tugraz.at/staff/markus/courses/SS2008/707.000_web-science/
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What are ways of searching in graphs? In this class, we will discuss basics of link analysis, including Google's PageRank algorithm as an example. Readings: The PageRank Citation Ranking: Bringing Order to the Web, L. Page and S. Brin and R. Motwani and T. Winograd (1998) Stanford Tecnical Report
