- Slides: 12
Segmental Mobility – Region of Viscoelasticity Segmental Mobility refers to the transitions occuring in a polymer chain while subjected to an increase in temperature. Related LOs: > Prior Viewing – Single Chain Conformation-Ideal Chain > Future Viewing – Unit cells in polymer crystal, Chain Folding-Lamella, Superposition Principle Course Name: Polymeric Materials Level: UG Author : R. Piramuthu Raja Ashok, Ph. D Scholar, IIT Madras Mentor: Dr. Susy Varughese *The contents in this ppt are licensed under Creative Commons Attribution-Non. Commercial-Share. Alike 2. 5 India license
Learning objectives 1 2 After interacting with this Learning Object, the learner will be able to: 3 4 5 Analyse the different thermal transitions in polymers. Differentiate the regimes of viscoelasticity. Predict thermal response of a polymer due to segmental mobility.
1 2 Master Layout (Part 1) Part 1: Segmental Mobility-Free Volume Glass- Transition 3 Glassy Rubbery 4 5 Viscous Flow
1 2 3 4 5 Definitions and Keywords Segmental Mobility 1. Free Volume: The space a polymer molecule has for internal movements/motions. 2. Backbone: simplest representation of the polymer (C-C) chain where pendant groups are attached. 3. Gamma Transitions: Free volume increase due to localised bond movements and side chain movements. 4. Beta Transitions: After gamma transitions, the free volume continue to increase; the whole side chains and localized groups of four to eight backbone atoms begin to have enough space to move. 5. Alpha Transitions: 1. In amorphous polymer, the alpha transition is the glass transition temperature, where the polymer transits from a glassy state to a rubbery state. 2. In crystalline polymer, large scale chain slippage occurs resulting in material to flow and the temperature is called melting temperature.
Part 1, Step 1: Free Volume Concepts 1 T Polymer Sample Free Volume 2 4 5 Volume 3 Occupied Volume Tg Temperature
Part 1, Step 1: 1 Action As shown in animation 2 3 4 5 Description of the action Audio Narration 1. The animation should start after the audio naration point 1. 2. The sequence is given as an animation in the powerpoint. Kindly follow the same direction. 3. The temperature bar can be altered if u have a sample bar with changing colors. . Or PLEASE use the same as in animation. 1. Segmental Mobility can be best understood from the free volume concepts. 2. Consider a polymer sample inside a heating chamber. When the temperature increases, the free volume of the sample increases. At a particular temperature, there is a change in the rate of increase of free volume. This transition is called glass transition temperature. 3. The occupied volume of the polymer increases linearly with the temperature. Now let us see what happens to the polymer chains when subjected to heating.
Part 1, Step 2: 1 T < Tα Increased Free Volume Tγ 5 Tβ 1 Tα 4 Rotation Modulus 4 Stretching Bending 2 Temperature 3 Molecule as collection of mobile segments
Part 1, Step 1: 1 Action As shown in animation 2 3 4 5 Description of the action Audio Narration 1. The sequence should be as in animation. 2. After the animation is completed, the fig 2 should appear without the arrows and the numbers against them. That callout and the arrow numbers are for animators communication. . Do remove it in original. 3. The arrow number 1 should stretch in both the arrow head direction. , i. e, the black line corresponding to arrow 1(polymer chain) should also stretch; same way arrow 2 - bending ; arrow 3 rotating. This movements should go alongside the curve. 1. In a polymer chain, when the temperature is increased, the chains vibrate and starting to slip past each other. This stage is where the gamma transitions are prominent. The bond stretching and bending occurs as the chain experiences more and more temperature. 2. As the temperature and the free volume continue to increase, the whole side chains and localized groups of four to eight backbone atoms begin to have enough space to move and the material starts to develop some toughness. This transition, called the beta transition Tβ. 3. At a particular temperature, the glassy state polymer transists into a rubbery state, this transtion is called glass to rubber transtion.
Slide 5 Free Volume Slide 10 Transtions Slide 18 Modulus- temperature Name of the section/stage Interactivity area Animation area Button 01 Button 02 Button 03 Instructions/ Working area Credits
APPENDIX 1 Questionnaire: 1. 2. 3. 4. In amorphous polymer, the alpha transition is called a) Metling temperture b) Glass-rubber transition c) Beta transition Melting temperature is a ______ order transition. a) First b) Second c) Zero d) Third Glass transition is a _______ order transition. a) First b) Second c) Zero d) Third Free volume is the space occupied by neighbouring polymer chains. Yes/No?
Links for further reading APPENDIX 2 Reference websites: http: //pslc. ws. htm http: //plc. cwru. edu/tutorial/enhanced/main. h tm Books: Introduction to Polymer Viscoelasticity, 3 rd Edition, Montgomery T. Shaw, William J. Mac. Knight, Wiley Publications, 2005. Polymer Science & Technology, 2 nd Edition, Joel. R. Fried, Prentice. Hall India, 2003. Polymer Physics, U. W. Gedde, Chapman & Hall, London, 1995.
APPENDIX 3 Summary Temperature response of polymers and different transitions were studied. The glass transition temperature using free volume concept.