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Glass transition temperature (Tg)- Polymer Chemistry
 
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Anna University Engineering Chemistry-1 (Notes) CY6151 Unit-1 Polymer Chemistry Properties of Polymer Glass Transition temperature
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What is GLASS TRANSITION? What does GLASS TRANSITION mean? GLASS TRANSITION meaning & explanation
 
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What is GLASS TRANSITION? What does GLASS TRANSITION mean? GLASS TRANSITION meaning - GLASS TRANSITION definition - GLASS TRANSITION explanation. Source: Wikipedia.org article, adapted under https://creativecommons.org/licenses/by-sa/3.0/ license. The glass–liquid transition or glass transition for short is the reversible transition in amorphous materials (or in amorphous regions within semicrystalline materials) from a hard and relatively brittle "glassy" state into a viscous or rubbery state as the temperature is increased. An amorphous solid that exhibits a glass transition is called a glass. The reverse transition, achieved by supercooling a viscous liquid into the glass state, is called vitrification. The glass-transition temperature Tg of a material characterizes the range of temperatures over which this glass transition occurs. It is always lower than the melting temperature, Tm, of the crystalline state of the material, if one exists. Hard plastics like polystyrene and poly(methyl methacrylate) are used well below their glass transition temperatures, that is in their glassy state. Their Tg values are well above room temperature, both at around 100 °C (212 °F). Rubber elastomers like polyisoprene and polyisobutylene are used above their Tg, that is, in the rubbery state, where they are soft and flexible. Despite the change in the physical properties of a material through its glass transition, the transition is not considered a phase transition; rather it is a phenomenon extending over a range of temperature and defined by one of several conventions. Such conventions include a constant cooling rate (20 kelvins per minute (36 °F/min)) and a viscosity threshold of 1012 Pa·s, among others. Upon cooling or heating through this glass-transition range, the material also exhibits a smooth step in the thermal-expansion coefficient and in the specific heat, with the location of these effects again being dependent on the history of the material. The question of whether some phase transition underlies the glass transition is a matter of continuing research. The glass transition of a liquid to a solid-like state may occur with either cooling or compression. The transition comprises a smooth increase in the viscosity of a material by as much as 17 orders of magnitude without any pronounced change in material structure. The consequence of this dramatic increase is a glass exhibiting solid-like mechanical properties on the timescale of practical observation. This transition is in contrast to the freezing or crystallization transition, which is a first-order phase transition in the Ehrenfest classification and involves discontinuities in thermodynamic and dynamic properties such as volume, energy, and viscosity. In many materials that normally undergo a freezing transition, rapid cooling will avoid this phase transition and instead result in a glass transition at some lower temperature. Other materials, such as many polymers, lack a well defined crystalline state and easily form glasses, even upon very slow cooling or compression. The tendency for a material to form a glass while quenched is called glass forming ability. This ability depends on the composition of the material and can be predicted by the rigidity theory. Below the transition temperature range, the glassy structure does not relax in accordance with the cooling rate used. The expansion coefficient for the glassy state is roughly equivalent to that of the crystalline solid. If slower cooling rates are used, the increased time for structural relaxation (or intermolecular rearrangement) to occur may result in a higher density glass product. Similarly, by annealing (and thus allowing for slow structural relaxation) the glass structure in time approaches an equilibrium density corresponding to the supercooled liquid at this same temperature. Tg is located at the intersection between the cooling curve (volume versus temperature) for the glassy state and the supercooled liquid.
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Time temperature superposition
 
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Time temperature superposition Prof. Abhijit P Deshpande Department of chemical Engineering IIT Madras
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Polymers: Introduction and Classification
 
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This lecture introduces to the basics of Polymers, their classifications and application over wide domains.
Polystyrene
 
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Polystyrene (PS) /ˌpɒliˈstaɪriːn/ is a synthetic aromatic polymer made from the monomer styrene, a liquid petrochemical. Polystyrene can be rigid or foamed. General purpose polystyrene is clear, hard and brittle. It is a very inexpensive resin per unit weight. It is a rather poor barrier to oxygen and water vapor and has a relatively low melting point. Polystyrene is one of the most widely used plastics, the scale of its production being several billion kilograms per year. Polystyrene can be naturally transparent, but can be colored with colorants. Uses include protective packaging (such as packing peanuts and CD and DVD cases), containers (such as "clamshells"), lids, bottles, trays, tumblers, and disposable cutlery. Polystyrene is used to make napalm-B, where it makes up about 46% of the formulation. As a thermoplastic polymer, polystyrene is in a solid (glassy) state at room temperature but flows if heated above about 100 °C, its glass transition temperature. It becomes rigid again when cooled. This temperature behavior is exploited for extrusion, and also for molding and vacuum forming, since it can be cast into molds with fine detail. This video is targeted to blind users. Attribution: Article text available under CC-BY-SA Creative Commons image source in video
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Polymer blend
 
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A polymer blend or polymer mixture is a member of a class of materials analogous to metal alloys, in which at least two polymers are blended together to create a new material with different physical properties. This video is targeted to blind users. Attribution: Article text available under CC-BY-SA Creative Commons image source in video
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Polymer
 
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A polymer (/ˈpɒlɨmər/) (poly-, "many" + -mer, "parts") is a large molecule, or macromolecule, composed of many repeated subunits. Because of their broad range of properties, both synthetic and natural polymers play an essential and ubiquitous role in everyday life. Polymers range from familiar synthetic plastics such as polystyrene to natural biopolymers such as DNA and proteins that are fundamental to biological structure and function. Polymers, both natural and synthetic, are created via polymerization of many small molecules, known as monomers. Their consequently large molecular mass relative to small molecule compounds produces unique physical properties, including toughness, viscoelasticity, and a tendency to form glasses and semicrystalline structures rather than crystals. The term "polymer" derives from the ancient Greek word πολύς (polus, meaning "many, much") and μέρος (meros, meaning "parts"), and refers to a molecule whose structure is composed of multiple repeating units, from which originates a characteristic of high relative molecular mass and attendant properties. The units composing polymers derive, actually or conceptually, from molecules of low relative molecular mass. The term was coined in 1833 by Jöns Jacob Berzelius, though with a definition distinct from the modern IUPAC definition. The modern concept of polymers as covalently bonded macromolecular structures was proposed in 1920 by Hermann Staudinger, who spent the next decade finding experimental evidence for this hypothesis. This video is targeted to blind users. Attribution: Article text available under CC-BY-SA Creative Commons image source in video
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Lec 29 | MIT 3.091SC Introduction to Solid State Chemistry, Fall 2010
 
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Lecture 29: Polymers: Synthesis, Properties & Applications Instructor: Donald Sadoway View the complete course: http://ocw.mit.edu/3-091SCF10 License: Creative Commons BY-NC-SA More information at http://ocw.mit.edu/terms More courses at http://ocw.mit.edu
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Lec 28 | MIT 3.091 Introduction to Solid State Chemistry
 
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Organic Glasses - Polymers: Synthesis by Addition Polymerization and by Condensation Polymerization View the complete course at: http://ocw.mit.edu/3-091F04 License: Creative Commons BY-NC-SA More information at http://ocw.mit.edu/terms More courses at http://ocw.mit.edu
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Polymers
 
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Polymers
Copolymer
 
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When two or more different monomers unite together to polymerize, their result is called as copolymer and its process is called copolymerization. Commercially relevant copolymers include acrylonitrile butadiene styrene (ABS), styrene/butadiene co-polymer (SBR), nitrile rubber, styrene-acrylonitrile, styrene-isoprene-styrene (SIS) and ethylene-vinyl acetate. This video is targeted to blind users. Attribution: Article text available under CC-BY-SA Creative Commons image source in video
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Lec 28 | MIT 3.091SC Introduction to Solid State Chemistry, Fall 2010
 
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Lecture 28: Polymers: Structure & Composition Instructor: Donald Sadoway View the complete course: http://ocw.mit.edu/3-091SCF10 License: Creative Commons BY-NC-SA More information at http://ocw.mit.edu/terms More courses at http://ocw.mit.edu
Views: 16030 MIT OpenCourseWare
Polystyrene
 
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Polystyrene /ˌpɒliˈstaɪriːn/ is a synthetic aromatic polymer made from the monomer styrene, a liquid petrochemical. Polystyrene can be rigid or foamed. General purpose polystyrene is clear, hard and brittle. It is a very inexpensive resin per unit weight. It is a rather poor barrier to oxygen and water vapor and has a relatively low melting point. Polystyrene is one of the most widely used plastics, the scale of its production being several billion kilograms per year. Polystyrene can be naturally transparent, but can be colored with colorants. Uses include protective packaging , containers , lids, bottles, trays, tumblers, and disposable cutlery. Polystyrene is used to make napalm-B, where it makes up about 46% of the formulation. This video targeted to blind users. Attribution: Article text available under CC-BY-SA Public domain image source in video
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Lec 29 | MIT 3.091 Introduction to Solid State Chemistry
 
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Structure-property Relationships in Polymers, Crystalline Polymers View the complete course at: http://ocw.mit.edu/3-091F04 License: Creative Commons BY-NC-SA More information at http://ocw.mit.edu/terms More courses at http://ocw.mit.edu
Views: 29951 MIT OpenCourseWare
Mod-01 Lec-02 Introduction to Polymers (Contd.)
 
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Polymer Chemistry by Dr. D. Dhara,Department of Chemistry and Biochemistry,IIT Kharagpur.For more details on NPTEL visit http://nptel.ac.in
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Mod-03 Lec-10 Principles of Polymer Synthesis (Contd.)
 
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Science and Technology of Polymers by Prof. B. Adhikari,Department of Metallurgy and Material Science,IIT Kharagpur.For more details on NPTEL visit http://nptel.ac.in
Views: 590 nptelhrd