Polymer Chemistry: Types, Fabrication, Advantages

Polymer Classifications

• Polymers are broadly classified into natural and synthetic types.
• Natural polymers include cellulose, starch, and rubber.
• Synthetic polymers are further divided into plastics, fibers, and elastomers.
• Plastics include thermoplastics like polyethylene and thermosets like bakelite.
• Fibers consist of polyamides and polyester.
• Elastomers include neoprene.

Polymer Fabrication and Processing

• Polymers are created through a polymerization process, linking basic units or monomers into macromolecules.
• The resulting high molecular weight polymers can be processed into rubbers, plastics, fibers, adhesives, and coatings.
• Additives such as plasticizers, stabilizers, and fillers are used in polymer processing.

Advantages of Plastics

• Plastics have a low weight, with a density approximately 10% that of steel.
• Plastics are environmentally efficient, requiring less than 30% of the processing energy needed for metals.
• Plastics enable the fabrication of parts with complex geometries and the adaptation of properties to production requirements.
• Plastics are thermal and electrical insulators, and exhibit corrosion and chemical resistance.
• Plastics can be colored and transparent with a controllable friction coefficient.
• Plastics allow for large manufacturing quantities and display elasticity.
• Global consumption of plastics polymers is 200,000,000 tons.
• Global consumption of steels is 1,000 tons.

Polymer Pricing

• Engineering materials' prices vary widely.
• Petroleum-based fuels and construction materials like glass, structural steel, bricks, and concrete are the least expensive.
• Polymers, technical ceramics, and glasses have mid-range prices.
• Exotic materials like diamond, platinum, gold, sapphire, iridium, and beryllium are the most expensive.
• Manufactured products also range in price from inexpensive construction materials to extremely costly items.

Thomas Hancock & Charles Goodyear

• Thomas Hancock and Charles Goodyear patented vulcanization in their respective countries during the 19th century.
• Vulcanization involves adding sulfur to latex in a liquid state ensuring it retains elasticity during processing.

Plastic Composition

• Plastics consist of polymers and additives.
• Polymers are macromolecules, "many parts"
• Every pearl constitutes a repetitive unit formed by one or more monomers

Polymerization Types

• Polymers are obtained through polymerization, with two primary methods: addition and condensation.
• Addition polymerization is exemplified by polyethylene from ethylene monomers expressed as CH2=CH2, forming a chain structure.
• Condensation polymerization is exemplified by polyamides (nylon) from diamines and diacids, with a byproduct of H2O.

Copolymers Composition

• Copolymers are synthesized from two monomers that react with each other instead of forming separate polymers.
• An example is ethylene-propylene copolymer.
• Copolymers can be random, alternant, block, or graft copolymers depending on the arrangement of the monomers.

Polymer Structure

• Polymer structures can be amorphous, resembling clews, or semicrystalline.
• Semycristalline structures can be lamela or spherulite

Molecular Architecture

• Molecular architecture includes linear, branched, and reticulated structures.
• Tacticity, or the stereochemical arrangement in chiral centers, is key.
• IUPAC defines tacticity as macromolecules with constant repeating unit configurations.
• Ordered structures can be isotactic or syndiotactic and tend to crystallize in regular structures.
• Atactic structures tend to be amorphous, which results in lower densities, are easily deformed, offer low stiffness, poor chemical/heat resistant, and low processing temperatures due to low packing.

Thermal Transitions in Thermoplastic Polymers

• Amorphous polymers exhibit a glass transition temperature (Tg) and a decomposition temperature (TD).
• Semicrystalline polymers show a glass transition temp, a crystalline melting point (Tm), and a decomposition temp.
• The state of aggregation and temperature determine final system behavior.

Transformation Processes

• Transformation involves pre-molding, molding, and shape stabilization.
• Pre-molding transports heat to high fluidity.
• Molding flows material through shaping tools.
• Shape stabilization treatment achieves permanent dimensions.

Methods of Transformation

• Continuous methods, such as extrusion, are used for simple geometries.
• Cyclic methods, like injection molding and thermoforming, are employed for complex geometries.

Crosslink Formation

• Crosslinks are formed when the crosslinking (heat) has been promoted.
• Chains have reactive points like double bonds.
• Primary links can form "Direct" between segments or go through bridges by reactive substances like sulfur and styrene monomer.

Thermoplastics Classifications

• Thermoplastics are classified based on price and benefits as well as consumer volume.
• Categories include "Commodities", "Engineering", and "Specials".
• "Commodities" such as PS and PVC tend to be amorphous, as LDPE and HDPE tend to be semicrystalline.
• Engineering plastics include PC, PPO/PS, ASA, SMA, ABS, PMMA, PET, AND EVOH
• Special plastics Include PI, PEEK, PPS, PTFE, PEI, PA11, PES and PA12

Characteristics of Amorphous vs Semicrystalline Thermoplastics

• Amorphous thermoplastics offer are have less heat resistance, a softening range, and are transparent.
• Amorphous thermoplastics offer less shrinkage during cooling, more tenacity at low temp, less dimensional stability, poor fatigue strength, and high creep.
• Semicrystalline thermoplastics have more heat resistance, a punctual fusion temperature, are opaque, greater shrinkage during cooling.
• Semicrystalline thermoplastics offer low toughness at low temp, higher dimensional stability, and are more resistant to fatigue and wear with lower creep.

Thermoplastic Polymers

• Acrylonitrile-butadiene-styrene (ABS)
• Cellulose Ionomers Polyamides (Nylon, PA)
• Polycarbonate (PC)
• Polyethetherketone (PEEK)
• Polyethylene (PE)
• Polymethylmethacrylate (PMMA)
• Polyoxymethylen (POM)
• Polypropylene (PP)
• Polystyrene (PS)
• Polytetrafluoroethylene (PTFE)
• Polyvinylchloride (PVC)
• Polyurethane (PU)
• Polyester (PET, PETE, PBT)

Types of Plastics

• Thermosets are resins that polymerize when catalyzed and heated, and degrade instead of softening when reheated.
• The first commercial thermoset was bakelite, the phenolic resin which offer greater dimensional stability than thermoplastics.
• Thermosets are used in applications needing high-temperature resistance and creep resistance and can be hard, rigid, flexible, or soft.

Thermoset Polymers

• Epoxy
• Phenolics
• Polyester
• Polyurethane
• Polychlorinated

Elastomers Properties

• Elastomers can lengthen, compress, and flex and return to their original shape when the load is finished.
• Elastomers are easy to foam

Elastomers Types

• Acrylic elastomers Chlorinated Elastomers (Neoprene)
• Ethylene-Propylene (EPDM)
• Ethylene-vinyl acetate (EVA)
• Fluorocarbon elastomers (Viton)
• Isoprene Natural rubber Nitrile (NBR, BUNA-N)
• Polybutadiene elastomers Silicone Styrene Butadiene (SBS)
• Thermoplastic elastomers (ΤΡΕ, ΤΡΟ)

World Plastic Consumption (2010)

• Europe consumed 24%
• USA consumed 23%
• Japan consumed 23%
• China consumed 11%
• Taiwan consumed 8%
• Korea consumed 5%
• Russia consumed 3%
• Other countries consumed 3%

Plastic Transformation in Mexico (2008)

• Injection molding made up 34%
• Extrusion made up 30%
• Blowing made up 15%
• Laminated made up 6%
• Rotomolding made up 4%
• Foaming made up 4%
• Compression made up 2%
• Others made up 5%

Top 5 Polymers Consumers

• Ethylene (tpPE, elPE, HDPE, TPO, Mixes PE/PP, foam PE, fiber PE, PP, PP foam, LDPE, EPDM, LLDPE, CPE, PP mixes, PP fiber, VLDPE, EVA, lonomers)
• Styrene (tpPS, elPS, foam PS, mixes PS, ABS, SAN, ASA, ABS mixes, ABS foams, HIPS, SEBS, SBR)
• Chlorinated Vynil (elPVC, tpPVC)
• Urethane (PU foam, tsPU, tpPU) Esters (tpPolyester, tsPolyester, elPolyester Polyester fiber, PET, UP, TPEs, PBT PETE)

Global Consumption of Polymers by Type

• Packaging is a major consumer by %, and contains PE-LD, PE-LLD, PE-HD, PE-MD, PP, PS, PS-E, PVC, PET, ABS, SAN, PMMA, PA, PC, Other ETP, PUR, and Other plastics.
• Building and Construction makes up 19.7% of global use in the form of PE-LD, PE-LLD, PE-HD, PE-MD, PP, PS, PS-E, PVC, PET, ABS, SAN, PMMA, PA, PC, Other ETP, PUR, and Other plastics.
• Automotive makes up 10% of global use in the form of PE-LD, PE-LLD, PE-HD, PE-MD, PP, PS, PS-E, PVC, PET, ABS, SAN, PMMA, PA, PC, Other ETP, PUR, and Other plastics.
• Electrical and Electronic makes up 6.2% of global use in the form of PE-LD, PE-LLD, PE-HD, PE-MD, PP, PS, PS-E, PVC, PET, ABS, SAN, PMMA, PA, PC, Other ETP, PUR, and Other plastics.
• Agriculture makes up 3.3% of global use in the form of PE-LD, PE-LLD, PE-HD, PE-MD, PP, PS, PS-E, PVC, PET, ABS, SAN, PMMA, PA, PC, Other ETP, PUR, and Other plastics.
• Household, Leisure & Sports makes up 4.2% of global use in the form of PE-LD, PE-LLD, PE-HD, PE-MD, PP, PS, PS-E, PVC, PET, ABS, SAN, PMMA, PA, PC, Other ETP, PUR, and Other plastics.
• Others Industries Makes up 16.7% of global use in the form of PE-LD, PE-LLD, PE-HD, PE-MD, PP, PS, PS-E, PVC, PET, ABS, SAN, PMMA, PA, PC, Other ETP, PUR, and Other plastics.

Polyolefins - Poliethylene (PE)

• Polyolefins which are mostly semicrystallines are made from Polyethylene (PE)
• Has a Tg of -120ºC
• LDPE: Low-density polyethylene or high pressure (r = [0.914 - 0.94 g/cm³]), branched showing low crystallinity with 40 to 45% yielding T m = 110 – 112 ºC and T c = 96 - 100 ºC
• HDPE: High-density polyethylene or low pressure( r = [0.96 - 0.97 g/cm³]), Linear with few and short branches with high crystallinity with 60 to 80 % yielding Tm = 130 – 135 ºC and Tc = 118 - 120 ºC

Effect of Molecular Mass on Polyethylene

• When Number of -(CH2-CH2)- unites is 1 then MW is 30 g/mol, Softening temperature is -169 and state is Gas
• When Number of -(CH2-CH2)- unites is 6 then MW is 170 g/mol, Softening temperature is -12 and state is Liquid
• When Number of -(CH2-CH2)- unites is 35 then MW is 1,000 g/mol, Softening temperature is 37 and state is Grease
• When Number of -(CH2-CH2)- unites is 140 then MW is 4,000 g/mol, Softening temperature is 93 and state is Wax
• When Number of -(CH2-CH2)- unites is 250 then MW is 7,000 g/mol, Softening temperature is 98 and state is Hard wax
• When Number of -(CH2-CH2)- unites is 430 then MW is 12,000 g/mol, Softening temperature is 104 and state is Hard resin
• When Number of -(CH2-CH2)- unites is 750 then MW is 21,000 g/mol, Softening temperature is 110 and state is Hard resin
• When Number of -(CH2-CH2)- unites is 1,350 then MW is 38,000 g/mol, Softening temperature is 112 and state is Hard resin
• The change from Hard Wax through to hard resin is defined as when it turns from plastic to polymer.

Polyolefins - Linear Low Density or Low Pressure Polyethylene (LLDPE)

• Polyolefins which are of a commodity are made from Linear Low Density or Low Pressure Polyethylene with a p = [0.94 - 0.96 g/cm³]
• Are typically branched (Short and regular) Medium crystallinity: 45 a 50%
• Stereospecific (Ziegler – Natta, ZN) or “One site” (Metallocenic, Met) is added
• With a structure of CH2= CH2 with + catalyzer yielding C2= CH- (CH2)n- CH3 yielding n= 5,7,9
• Showing a Tm = 115 – 120 ºC
• and T c = 105 -110 ºC

Polyolefins - Polypropylene (PP)

• Polyolefins are commodities which are a made from Polypropylene (PP) which is -(-CH2-CH-)- with a by product of CH3 Yielding a p = [0.895 - 0.92 g/cm³] a Tg = -10ºC, * T m = 165 ºC andT c = 120 ºC Showing an Isotactic orientation → Crystallinity: 60 a 70 %
• Is combined with Ethylene to reduce "unstable tear" problems giving a high impact resistance for a wider T (mínimum) service range
• Shows various orientations of Block compolymer or Random copolymer

Polyolefins (Copolymers)

• Polyolefines can be made with copolymer such as ETHYLENE - VYNIL ACETATE(EVA) with a structure of (-CH2-CH2-)n- combined yielding a (-CH2-CH-)m-
• Vinyl Acetate lends confers flexibility and reduces crystallinity 1 – 10 % mol de VA  More rigid 30 - 40 % mol de VA  Adhesive
• ETHYLENE - VYNIL ALCOHOL (EVOH)
• (-CH2-CH2-)n- and gives a structure of (-CH2-CH-)m-, is Semicrystalline regardless of VOH content a High barrier to 02 (Molecular "auto-association" by H2 bridge) Showing a Tg = 60 ºC and Tm = 185 a 200 ºC , typically High barrier to 02 and is Hydrophilic!!!!! (absorbs humidity)

Hallogenated Plastics

• Are commodities that display a POLYVYNILCHLORIDE (PVC) and a Semicrystalline structure and show a structure of -(-CH2-CH-)- a with a 8 Tg = 80 ºC and a * Tm = 230 ºC Thermal UNSTABLE(TD  80 -90ºC) producing HCI Which is typically Rigid and fragile with plasticizers which catalyze degradation

• Special Hallogenated plastics includes VINYLIDENE POLYCHLORIDE (PVDC) with has a -(-CH-CH-)- chain, is More termal stable, Hard to process, Excellent gas barrier

Styrene Plastics

• A commodity are POLYa STYRENE (PS) , is Transparent, UV sensible and Very fragile! Structure shows -(-CH2-CH-)- a with a Tg = 100 ºC Polyexpan can be created with Polystyrene (emulsión grade) which is Expanded (PS + n-pentano (volatile) And for a More durable and long use plastic HIGH IMPACT POLYSTYRENE (HIPS) has a High impact resistance and is still Opaque! has -(-CH2-CH-)n-(CH2-CH=CH-CH2-)n-

Styrene Copolymers

• Are of commodity – engineering grade in the form of ABS (Acrylonitrile-Butadiene-Styrene) with -(-CH2-CH-)n-(CH2-CH=CH-CH2-)n- -(-CH2-CH-)- shown
• A is Acrilonitrile, B-S is Butadiene & Styrene
• And with added components in the form ofSAN (Styrene- Acrylonitrile): with -(-CH2-CH-)−(-CH2-CH-)n- And can be modified into MBS (Methacrylate-Butadiene-Styrene), ASA (Acrilonitrile-Styrene-Ethyl Acrylate) with shown -(-CH2-CH-)- S-A , also -(-CH2-C-)- with added modifiers

Polyamides

• Polyamides are an engineering grade plastic shown as Vía 1 or Via 2

Acrylic Enginnering

• Is an engineering grade acrylic compound displayed showing various structires
• and the following grades of "Casting" or "in-situ polymerization" grades
• And is an addition of Monomer + initiator in the mold (mass) as well as "Prepolymer" + initiator in the mold which produces a T (exothermic reaction) and T volumetric contraction
• Showing a Molecular mass (Mn = 106) and Very low fluidity (impracticable) which yields Atactic > 37, Sindiotactic > 54% and Isotactic > 9%

Engyneering and solar radiation resistant acrylics

• Tranparent to UV solar radiation which shows High resistance to Photodegradation!
• And as a result shows a Refraction index of 1,492 which is high in comparision to 1,59 of (PS)
• Independent from time
• Aslo shows a Critical angle for total internal reflection in the 42 ° Air-PMMA interface All enabling the development or OOTIC FIBERS In contrast it shows a Low resistance to "Scratch" Which shows a limited utilization in use of car headlights because possible limitation in the use of car headlights has been developed which helps mitigatates the problem of Coating with siloxanes

Acrylics PMMA

Copolymers MMA – Butyl Acrylate and PMMA / Polymethacrylate (PBA) mixtures Show higher transparency that in turn makes them not very sensitive to UV - The material is quite brittle - "Casting" grade (MMA polymerizes during forming) enabling Optical applications (high purity) with ASA