2024 Polymer Lecture Notes (StrucPropPolymers) PDF

Phases in Polymers Phases: Silly putty Solid Suspensions Liquid crystalline materials – Crystalline phase → order (atomic/ molecular level) – Amorphous phase → lack of order...

Phases in Polymers Phases: Silly putty Solid Suspensions Liquid crystalline materials – Crystalline phase → order (atomic/ molecular level) – Amorphous phase → lack of order Liquid – Melts (amorphous phase) – Solutions – Blends – Emulsions Gas – not relevant for polymers Amorphous phase → Glass Transition 1  Communication Board! Class schedule and location – start date Aug 13th , 2024 Slot J - Tues, Thurs, Fri : 4 – 4:50 PM; location PH104 Evaluation (offline + online) % Student count/ background – 10/ CH, PH (Academic Regulations 4.2) Extra class/ buffer days Continuous evaluation + Minor (60 - 40 %): Last day of classes/ attendance submission – Nov 18th , 2024 / – Assignments Monday Class notes Examination dates and modalities Surprise quizzes – Minor – Sep 19th-21st, 2024 Quizzes Flipped classroom – Major: Nov 20th -26th, 2024 Discussion board Attendance Case studies Make class notes - correlation Paper reviews Projects Substitution days – Sep 4th, 2024 (Wed) → Friday’s timetable – Classroom participation Recognize Class performance – performers ! – In class problem solving Quiz 1 – Aug 20th, 2024 --> Akshita Chaudhary – Guest lectures – In class demos (Lab 206 for Feedback Harshita Deka more !) Kaushik Sachan Other courses offered Major examination (40 – 60 %) Continuous evaluation Assignment # 1 : Polymer Industry – Due date Aug 27th, 2024 2  Glass Transition Response/ Mobility of the macromolecule with temperature → Only segmental motion is allowed to a polymer chain at and below Tg. Modes for mobility: (Jam !) Based on type of motion: Chain Vs Segmental motion Translational motion Rotational motion Vibration motion Based on length scale of motion: Chain motion Segmental motion (cooperative motion of 10-50 main chain units) Based on direction w.r.t. the chain axis: Along the chain axis Perpendicular to the chain axis 3  Why do we care about motion ? Motion/ mobility --> Relaxation Motion  Energy 4  Typical Thermal Behavior/ Molecular Structure Semicrystalline Thermoplastics Become liquid upon application of heat (thermal treatment) heating Tg - onset Tg - end Crystalline phase – T glass m Amorphous phase - Tg Modulus Tm Amorphous state Rubber Melt/ liquid (flow !) semicrystalline state Temperature 5  Thermal Process Behavior/ Molecular Structure Tg marks the onset of cooperative translational and rotational motion over larger segmental length scales upon heating. Below Tg polymer chains/ macromolecules do not possess rotational and translational motion for the whole chain rather just for the segment/s. Usually both, Tm and Tg, increase with increasing chain stiffness (Ex: PE Vs PET) and increasing intermolecular attraction forces. Q. Amorphous polymers do not melt. Is that T/F ? oC oC Melting point 250 oC – 260 oC Melting point 110 – 135 6 https://www.britannica.com/science/polyethylene Thermal Process Behavior/ Molecular Structure Thermoplastics Q. Amorphous polymers do not melt. Is that T/F ? Ans. T, as these do not have any ordered phases. Typically, viscosity decreases as temperature increases. For amorphous polymers, viscosity needs to low enough for so called “melt processing”, and this occurs above Tg. Melt processing is a misnomer for amorphous polymers. Can we have crystalline phases in thermosets ? yes 7  Amorphous State in Polymers Amorphous state in polymers – no well-defined order at molecular level (whole molecule or part of the molecule !) Phases in amorphous state in polymers Solid amorphous state – glass Liquid amorphous state – melt Examples: Polystyrene (PS): amorphous glassy polymer, brittle and cheap Epoxy based polymers: adhesives Poly (methlymethacrylate) (PMMA): excellent optical properties, eye lenses, automotive lenses Polycarbonate (PC): optical clarity, toughness, automotive lenses, bullet proofing Inorganic glasses Rubbers 8  Amorphous State in Polymers Amorphous polymers in solid state can be thought of as frozen polymer liquids? Is that T/F? True Quite a few thermoplastics are semicrystalline in nature i.e., they contain amorphous as well as crystalline phases, Examples: Polyethyleneterephthlate (PET), polyethylene (PE), isotactic polypropylene (iPP). PET and iPP crystallize slowly and can be obtained with minimal crystallinity/ almost amorphous via rapid quenching. Crystallization can be initiated by annealing the quenched polymer at elevated temperatures (between Tg and Tm). I.e. annealing process occurs in solid state. 9