The document discusses the glass transition temperature (Tg) of polymers. Tg is the temperature at which an amorphous polymer transitions from a brittle, glassy state to a rubbery, flexible state. It depends on factors like the polymer's chemical structure, molecular weight, and presence of plasticizers. Knowing the Tg is important as it indicates the physical state of the polymer and suitable processing conditions. It also provides information about the polymer's flexibility and how it will respond to mechanical stresses.
Brief intro about crystalline and amorphous structures,
glass transition temperature,
free volume theory of glass transition temperature,
factors effecting glass transition temperature etc.
Introduction
Why do we need plasticizers?
Mechanism of action of plasticizers
Properties of plasticizers
Classification of plasticizers
Selection of plasticizers
Effect of plasticizer on permeability of film.
Effect of plasticizer on mechanical properties of film.
Effect on residual internal stress.
Effect of plasticizers on release rates of drug.
Texture of plasticized films.
Limitations.
Conclusion.
Brief intro about crystalline and amorphous structures,
glass transition temperature,
free volume theory of glass transition temperature,
factors effecting glass transition temperature etc.
Introduction
Why do we need plasticizers?
Mechanism of action of plasticizers
Properties of plasticizers
Classification of plasticizers
Selection of plasticizers
Effect of plasticizer on permeability of film.
Effect of plasticizer on mechanical properties of film.
Effect on residual internal stress.
Effect of plasticizers on release rates of drug.
Texture of plasticized films.
Limitations.
Conclusion.
A polymer is a large molecule, or macromolecule, composed of many
repeated subunits. The structure of a polymer is defined in terms of
crystallinity. This might also be thought of as the degree of order or regularity
in how the molecules are packed together. A well-ordered polymer is
considered crystalline. The opposite is an amorphous polymer. Almost
all amorphous polymers possess a temperature boundary. Above this
temperature the substance remains soft, rubbery and flexible, and below
this temperature it becomes hard, glassy and brittle.
The temperature, below which a polymer is hard and above which
it is soft is called the glass transition temperature.
For example:-
When an ordinary natural rubber ball if cooled below -70oC becomes so
hard and brittle that it will break into several pieces like a glass ball falling on a
hard surface.
This happens because there is a temperature boundary for amorphous.
The transition from the rubber to the glass-like state is an important feature of
polymer behavior, marking as it does a region where dramatic changes in the
physical properties, such as hardness and elasticity, are observed.
The hard, glassy, brittle state is known as the glassy state and the soft,
rubbery, flexible state is the rubbery or viscoelastic state. The glass transition
temperature is denoted by Tg.
Tf is another term for temperature, when a polymer is heated further, it forms
a viscous liquid and starts flowing, this state is known as viscous-fluid state
and the temperature is termed as flow temperature (Tf).
Tg is an important characteristic property of any polymer as it has an
important bearing on the potential application of a polymer.
polymerization is a process of bonding monomer, or "single units" together through a variety of reaction mechanisms to form longer chains named Polymer.
It consists classification of polymerization techniques. What is bulk polymerization, how will the reaction proceed, and what are the advantages, disadvantages, and applications. Similarly, what is solution polymerization and how it will be carried out, what are the advantages, disadvantages, and applications behind it everything is explained in detail. Some of the related questions are also included for practice. All the contents taken from different websites and books are also mentioned.
A polymer is a large molecule, or macromolecule, composed of many
repeated subunits. The structure of a polymer is defined in terms of
crystallinity. This might also be thought of as the degree of order or regularity
in how the molecules are packed together. A well-ordered polymer is
considered crystalline. The opposite is an amorphous polymer. Almost
all amorphous polymers possess a temperature boundary. Above this
temperature the substance remains soft, rubbery and flexible, and below
this temperature it becomes hard, glassy and brittle.
The temperature, below which a polymer is hard and above which
it is soft is called the glass transition temperature.
For example:-
When an ordinary natural rubber ball if cooled below -70oC becomes so
hard and brittle that it will break into several pieces like a glass ball falling on a
hard surface.
This happens because there is a temperature boundary for amorphous.
The transition from the rubber to the glass-like state is an important feature of
polymer behavior, marking as it does a region where dramatic changes in the
physical properties, such as hardness and elasticity, are observed.
The hard, glassy, brittle state is known as the glassy state and the soft,
rubbery, flexible state is the rubbery or viscoelastic state. The glass transition
temperature is denoted by Tg.
Tf is another term for temperature, when a polymer is heated further, it forms
a viscous liquid and starts flowing, this state is known as viscous-fluid state
and the temperature is termed as flow temperature (Tf).
Tg is an important characteristic property of any polymer as it has an
important bearing on the potential application of a polymer.
polymerization is a process of bonding monomer, or "single units" together through a variety of reaction mechanisms to form longer chains named Polymer.
It consists classification of polymerization techniques. What is bulk polymerization, how will the reaction proceed, and what are the advantages, disadvantages, and applications. Similarly, what is solution polymerization and how it will be carried out, what are the advantages, disadvantages, and applications behind it everything is explained in detail. Some of the related questions are also included for practice. All the contents taken from different websites and books are also mentioned.
Lecture notes on Structure and Properties of Engineering Polymers
Course Objectives:
The main objective is to introduce polymers as an engineering material and emphasize the basic concepts of their nature, production and properties. Polymers are introduced at three levels; namely, the molecular level, the micro level, and macro-level. Through knowledge of all three levels, student can understand and predict the properties of various polymers and their performance in different products. The course also aims at introducing the students to the principles of polymer processing techniques and considerations of design using engineering polymers.
Methods of polymerisation It is also called as Zeigler – Natta polymerisation.
Zeigler (1953) and Natta (1955) discovered that in the presence of a combination of transition metal halides like TCl4, ZnBr3 etc, with an organometallic compound like triethyl-aluminium or trimethyl-aluminium, stereospecific polymerisation can be carried out.
Combination of metal halides and organometallic compounds are called Zeigler Natta catalyst.
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
1. 1
THE GLASS TRANSITION
TEMPERATURE
Introduction
Polymer can be crystalline, amorphous or partially crystalline
depending on whether it possesses a long range ordered
structure or not.
A crystalline polymer exist as crystalline solid with long range
order (solid phase state) or as a molten liquid (liquid phase
state) with solid to liquid transition occurring at temperature
called ‘Melting Temperature (Tm)’.
An amorphous polymer which does not possess long range
order occurs in glassy solid, rubbery or liquid state. The
temperature at which amorphous polymer passes from glassy
solid to rubbery state is called ‘Glass Transition
Temperature (Tg)’ and the one at which it passes from
rubbery state to molten liquid is the ‘Flow Temperature (Tf)’.
Partially crystalline polymer has both crystalline and
amorphous portions.
Figure 1. Change of State with Temperature in Polymeric Materials
2. 2
Glass Transition and Glass Transition
Temperature
Glass transition is an important thermal property of
amorphous polymer or amorphous portion of partially
crystalline polymer. Almost all amorphous polymers have a
‘temperature boundary’ only above which it remains soft,
flexible and rubbery (Rubbery or Viscoelastic State) and
below which it becomes hard, brittle and glassy (Glassy State)
and this temperature of transition is called Glass Transition
Temperature.
Polymers structurally consist of localized units or chain
segments. Thus they can exhibit 2 types of motions:-
1. Segmental motion or micro or internal Brownian
movement.
2. Molecular motion or macro or external Brownian
movement.
In solid (glassy) state, both motions freeze. As the temperature
increases and reaches Tg, internal Brownian movement
activates, i.e., localized mobility is activated but overall
mobility is not. This is Rubbery state. At further high
temperature (around Tm), both Brownian movements are
activated and individual polymer chains start moving apart.
This is Liquid state.
Measurement of Tg
Tg is usually measured using dilatometer, which is based on
variation in the physical property – Specific Volume. With the
increase in temperature, initially there is a gradual increase in
the volume. With further increase in temperature, a point is
3. reached where there occurs an abrupt increase in volume. This
gives the value of Tg.
Figure 2. The relationship of Specific Volume of a Polymer with Temperature
Factors Affecting Glass Tra
Temperature
The presence or absence of segmental and molecular motion,
i.e., mobility of polymer chain decides whether a polymer is
in glassy, rubbery or molten state. Thus T
the following factors:-
1. CHEMICAL STRUCTURE
This includes –
a) Molecular Geometry:
orientation leading to long range 3
i.e., stereoregular
which has irregular backbone or randomly placed side
groups is amorphous. Segmental and chain mobilities
are easier in amorphous structure, thus their T
b) Flexibility: Flexibility of polymer chain is determine
by degree of freedom with which segments rotate along
chain backbone. Higher the degree of freedom of
rotation, more flexible the chain, so more segmental
mobility, thus lower T
3
reached where there occurs an abrupt increase in volume. This
The relationship of Specific Volume of a Polymer with Temperature
Factors Affecting Glass Transition
Temperature
The presence or absence of segmental and molecular motion,
i.e., mobility of polymer chain decides whether a polymer is
molten state. Thus Tg depends mainly
-
CHEMICAL STRUCTURE
Molecular Geometry: If polymer has definite molecular
orientation leading to long range 3 - dimensional order,
i.e., stereoregular structure, it is crystalline while one
which has irregular backbone or randomly placed side
groups is amorphous. Segmental and chain mobilities
e easier in amorphous structure, thus their Tg is low.
: Flexibility of polymer chain is determine
by degree of freedom with which segments rotate along
chain backbone. Higher the degree of freedom of
rotation, more flexible the chain, so more segmental
mobility, thus lower Tg.
reached where there occurs an abrupt increase in volume. This
The relationship of Specific Volume of a Polymer with Temperature
sition
The presence or absence of segmental and molecular motion,
i.e., mobility of polymer chain decides whether a polymer is
mainly on
definite molecular
dimensional order,
structure, it is crystalline while one
which has irregular backbone or randomly placed side
groups is amorphous. Segmental and chain mobilities
is low.
: Flexibility of polymer chain is determined
by degree of freedom with which segments rotate along
chain backbone. Higher the degree of freedom of
rotation, more flexible the chain, so more segmental
4. 4
Linear polymers with single bond have higher degree
of freedom of rotation, therefore lower Tg. For
example, polyethylene has Tg = - 120°C.
Presence of bulky groups or aromatic or cyclic
structure in polymer backbone hinders rotation thus
increasing the value of Tg. For example, nylon has Tg
= 50°C, polystyrene has Tg = 100°C.
c) Chain Polarity and Intermolecular Force: Tg increases as
the main chain polarity increases. Due to the increase in
polarity the intermolecular forces increase leading to
formation of strong molecular aggregates. These are not
able to move easily, i.e., restricted motion occurs, and
the value of Tg increases. For example, Polypropylene
has Tg = - 20°C, Polyvinyl chloride (which has C ― Cl
polar bond) has Tg = 81°C.
2. MOLECULAR WEIGHT
Value of Tg is influenced by the molecular weight of the
polymer (Mn upto 20000) according to the Fox- Flory
Equation, i.e.,
𝑇 = 𝑇∞
−
𝐾
𝑀
where, 𝑇∞
is Tg of polymer at infinite molecular weight,
K is Fox- Flory parameter for a polymer,
Mn is number average molecular weight of polymer.
5. 5
Figure 3. Plot showing effect of Molecular Weight on Tg of Polymer
From the curve, we can see that Tg value will be lower for
low molecular weight polymers.
3. PLASTICIZERS
Plasticizers are low molecular weight, non- volatile
substances (usually liquids) which are added to polymers to
improve its flexibility and utility. For example,
Dibutylpthalate.
Plasticizer molecules penetrate into polymer matrix and
establish polar attractive forces between it and polymer
chains. These attractive forces reduce cohesive forces and
increase segmental motion, thus reducing Tg.
Importance of Glass Transition
Temperature
Glass Transition Temperature is an important parameter of a
polymeric material.
Tg is used for evaluating the flexibility of a polymer
molecule and the type of response it would exhibit to
mechanical stress.
6. 6
It tells about the physical state of the polymeric material at
a given temperature, thus helps in deciding its use. For
example, Hard Plastics like Polystyrene and
Polymethylmethacrylate (Tg ~ 100°C) are used in glassy
state whereas Rubbery Elastomers like Polyisoprene and
polyisobutylene (Tg ~ - 73°C) are used in soft and flexible
rubbery state.
Tg value along with Tm value gives an indication of
temperature region at which a polymeric material
transforms from a rigid solid to viscous state. This helps in
choosing the right processing technique and temperature
for given polymeric material.
References:-
1. Principles of Polymer Chemistry; Ravve, A.
2. Polymer Science; Gowariker, Vasant R., Viswanathan,
N.V., Shreedhar, Jayadev.
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