Audio Transcript Auto-generated
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Hi everyone.
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My name is kayla koa,
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and today I will be taking a dive into polymer science and chemistry,
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polymers make up one of the largest subject areas of materials chemistry.
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The use of polymers is widespread in modern technology and
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they are used to enhance the properties of ceramics,
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metals, semiconductors and optical materials.
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The main reasons behind the widespread use and importance
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of polymers is that they can be fabricated easily,
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are corrosion resistant and lightweight and are generally inexpensive.
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As you can see here useful polymers come in both
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natural and synthetic forms and are present in many everyday products
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such as wool, epoxy, polyester, etcetera.
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Let's go over some of the basics of polymers.
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Polymers are large molecules made up of repetitive
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bonding of smaller molecules known as monomers.
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They can be grouped into two major categories. Homo polymers and co polymers.
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Homo polymers are made up of identical monomers,
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while co polymers are made up of deferring monomers.
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This arrangement of monomers makes up the polymers primary structure.
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The secondary structure describes the polymers shape or confirmation
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and typically approaches a helical or she arrangement.
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The tertiary structure describes the folding of the polymer
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and lastly,
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the coronary structure represents the overall shapes
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of groups of the tertiary structures.
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Structural characteristics of polymers are closely
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related to the material's properties,
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polymers can be linear, which contain an uninterrupted straight chain,
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branched polymers consist of smaller chains branching from the longer parent,
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both linear and branched polymers are typically
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thermal plastics that melt when heated.
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Network polymers are highly cross linked and create
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thermo sets that cannot be melted one shape
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the crosslink density and network molecules can bury from low,
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such as rubber bands to high, such as epoxy.
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The stereo chemistry of substitutes of the monomers that make up
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the polymer can also have an effect on its physical properties.
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It's a tactic,
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stereo chemistry means the substitute prints are on
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the same side of the polymer backbone,
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while Scindia tactic means these substitutes are alternating.
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A tactic means substitutes are random,
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I said, tastic and Cindy.
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A tactic arrangements are more likely to form compact crystalline structures and
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protect arrangements are more likely to form a more fa structures.
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Crystalline regions contribute largely to strong hard
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materials while amorphous regions allow some flexibility,
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these properties and how they are affected by a polymer structure
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are of great importance when synthesizing polymers for various industries.
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Next we'll cover some basics and organic, metallic and metal Lloyd polymers.
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Typically,
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polymer chemistry emphasizes materials derived from a
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select few elements such as carbon,
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hydrogen, oxygen,
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nitrogen, chlorine and floor eEN
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elements such as silicon,
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sulfur and phosphorus will link similar to the way carbon does.
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Since their bond energies are generally lower such products
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might be expected to offer lower thermal stability,
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ease and lower bond strength when compared to carbon based polymers,
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but this isn't always true.
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One common misconception is the type of bonding
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that can occur between inorganic and organic atoms.
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While there is clear ionic bonding,
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many of the inorganic organic bonding is the
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same nature as this present in organic compounds.
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Because of this,
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the same spatial geometric rules apply to these types
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of polymers as to the more classic polymers.
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The exception to these rules is the ion Immers pictured here
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where medals are bonded through ionic bonding two oxygen atoms.
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The number of potential polymers is vast because
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the inorganic portions can exist as oxides and salts
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in different oxidation states, different geometries, etcetera.
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The importance and application of these polymers is lesser known, but just as great
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for example, chlorophyll shown to the left
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is a metal containing polymer that allows photosynthesis to take place.
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These polymers form the basis of many insulators and building materials
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and are also present in high abundance in the earth's crust.
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These types of polymers exhibit a wide range
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of properties not common to most organic polymers,
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such as electrical conductivity and catalytic operations.
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You can see in Table nine point to
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the current and potential applications for organic,
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metallic and metal Lloyd Polymers.
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Let's talk about some of the reactions of these types of polymers.
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Any reactions are just an extension of known inorganic organic,
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metallic and organic reaction.
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The majority can be placed into two broad classes.
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Oxidation, reduction reactions known as redox and substitution reactions.
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Redox polymers have the ability to change their
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electrochemical properties by losing or gaining electrons.
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Redox reactions are important in this synthesis of polymers and monomers
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in the use of polymers catalysts and in applications involving transfer of heat,
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electricity and light
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substitution reactions typically contain a Ligon that acts as
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a leaving group as well as the agent of substitution
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Liggins or species that use a lone pair to form a co valent bond with a metal ion.
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An example of this is shown below between technical or
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platini and dia means to form the anticancer and antiviral
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platinum To polly mine.
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The chloride is the departing Ligon and the
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amine group is the agent of substitution.
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Many polymer forming reactions that occur at metal
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atom sites can be considered lewis acid base reactions
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that form covalin bonds.
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This reaction is also commonly compared to
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a biomolecular nuclear Felix substitution reaction,
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or SN two.
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Although the precise mechanism is difficult to describe because of the president,
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the presence of available D orbital's on the organic metallic atom.
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Inorganic metallic polymer substitution reactions,
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the electronic starik mechanistic kinetic and thermodynamic factors are
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the same as in regard to smaller molecules.
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Condensation reactions typically involved the expulsion of a smaller
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molecule leading to a repeating unit with fewer atoms
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than the sum of the two reactant.
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The reaction can be at the metal atom or somewhat displaced.
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Most condensation reactions can be considered in terms of polar mechanisms
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such as nuclear filic electra. Filic.
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Many organic metallic allies can behave similar to organic acid chlorides
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due to the high degree of co violent character.
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This is shown below in hydraulic Asus and polyester verification
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where the metal atom behaves similarly to the carbon well, carbon atom.
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Next we will look at inorganic polymers,
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polymers abound in the world of in organics and
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are major components in the natural world of soil,
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mountains, sands, etcetera.
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Just like organic polymers.
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They are also synthesized and uses abrasives, coatings, flame retardants,
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lubricant.
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The list goes on and on.
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These polymer structures do not include carbon in the background backbone.
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When carbon is present in the molecule,
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it is not bonded to hydrogen or organic side groups,
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we recover some of the more well known inorganic polymers.
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Portland cement is the least expensive and most widely
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used synthetic and organic polymer it typically consists of
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consists of anhydrous crystalline calcium silicates, lime and alumina.
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When anhydrous cement mix is added to water, the silicates form
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hydrates and calcium hydroxide.
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Once hardened,
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it contains about 70% cross links calcium
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silicate hydrate and 20% crystalline calcium hydroxide.
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The hardening of cement paste occurs through two major steps.
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First a layer is formed on the surface of the calcium
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silicate particles consisting of mainly water with some calcium hydroxide.
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This layer grows small fibers from each silicate
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particle that increased in number and length,
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becoming integrated among themselves.
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These fibers form sheets that contain tunnels and holes
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as these sites become saturated with calcium hydroxide,
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it begins to crystallize occupying vacant
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sites and interconnecting with the silicate.
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Silicone is the most abundant metal like
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element in earth's crust but is typically present in the large number of polymers
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based on the condensation of the Ortho silicate and ion,
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which is a tetrahedron silicon atom attached to four oxygen atoms.
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The variety and
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naturally occurring silicates is due to the ability
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of this anti on to be linked together
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forming various sized polymers and the substitution of different metal
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atoms of approximately the same size as silicon often forms.
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This figure shows general silicate structures from its simplest tetra huge inform
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president and things such as granite
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to a complex network found in courts.
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Cat ions similar in ionic radius to silicone
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such as iron,
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to aluminum and calcium are often found
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in silicate like structures like these pictures
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in the soul gel process,
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polymer precursors are formed in solution and then joined
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to furnish dense glasses or poly crystalline ceramics.
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The most common procedures involved Alcock sides of silicone, boron,
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titanium and aluminum
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in an alcohol water solution.
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The Alcock side groups are removed by
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hydraulic Asus and replaced by hydroxyl groups.
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Branch polymers chains grow and interconnect to
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form a network through the solution.
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The jell formed is dried by evaporation and
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consolidated two glasses or ceramics by centering,
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which is the process of forming a solid mass by heat or pressure.
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The nature of the reactions
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can be varied to produce different structures and properties.
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They are used in various products such as scratch resistant coatings.
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Adhesives for glass surfaces and absorbent
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Asbestos has been used for over 2000 years.
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It is not a single material but group of materials that give soft fibers.
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They contain two d.
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silicate and ions bound by a layer of aluminum hydroxide or magnesium hydroxide.
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It is used to make fire resistant fabric, electrical installation,
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building installation and brake linings.
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Carbon is also present in an organic materials such as diamond and graphite.
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Graphite is the more stable L. A. Trip of carbon.
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This image shows diamond to the left
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where carbon is the center of a tetrahedron formed by other carbon atoms,
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while graphite to the right is a layered planner
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molecule.
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This difference in structure creates one
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of the hardest naturally occurring materials
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on one end and a very brittle material on the other.
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I hope this presentation has given you more insight
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to the vast scopes of polymers in materials chemistry.
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Thank you.