Lesson #8: Polymer Processing PDF

EG 4391 A Manufacturing Processes Fall 2024 Lesson # 8 - Polymer Processing Chapter 10 Polymer Processing and Additive Manufacturing Copyright © 2017, 2008 Pearson Education, Inc. All Rights Reserved ...

EG 4391 A Manufacturing Processes Fall 2024 Lesson # 8 - Polymer Processing Chapter 10 Polymer Processing and Additive Manufacturing Copyright © 2017, 2008 Pearson Education, Inc. All Rights Reserved  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Plastics (polymers) Image Courtesy: https://augustrs.com/wp-content/uploads/2020/02/Polymer-Chain_1.jpg  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Plastics (polymers) - Characteristics: Low Density Low Strength, stiffness Low electrical and thermal conductivity Good chemical resistance High coefficient of thermal expansion Useful tmp range generally < 350o C Can be machined, cast, formed, and joined Doesn't typically require surface finishing  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Plastics (polymers) - History: The term polymer first used in 1866 Originally made from natural organic materials First synthetic polymer developed in 1906 called Bakelite Image Courtesy: https://www.quora.com/What-was-Bakelite-and-how-does-it-differ-from-modern- plastics  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Plastics (polymers) - Mechanical properties at room temp  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Plastics (polymers) - Mechanical properties at room temp  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Plastics (polymers) - The Structure of Polymers: Monomer - the basic building block of a polymer Polymer many mers or units repeated, generally in a chainlike structure Macromolecules/giant molecules formed by polymerization – the linking and cross-linking of different monomers  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Plastics (polymers) - Basic Structures  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Plastics (polymers) - Polymerization: Condensation polymerization – polymers produced by the formation of bonds between two types of reacting mers. Reaction by-products are condensed out. Addition polymerization – Aka chain-growth. Or chain reaction polymerization. Bonding takes place without reaction by-products. High rate of formation of long molecules occurring simultaneously. An initiator is added to open the double bond between the carbon atoms and begins the linking process by adding more monomers to a growing chain.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Plastics (polymers) - Basic Characterizations: Molecular weight, and molecular weight distribution. Increasing molecular weight increases tensile and impact strength, resistance to cracking, and viscosity in the molten state Degree of polymerization (DP): the ratio of the molecular weight of the polymer to the molecular weight of the repeating unit. Higher DP means higher viscosity/resistance to flow which can affect the ease of shaping and overall cost of processing Bonding: Covalent bonds link the monomers in the polymer chain (also called primary bonds). Van der Waals, hydrogen and ionic bonds from the weaker secondary bonds between polymer chains  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Plastics (polymers) - Basic Characterizations: Linear polymers: chainlike polymers, as shown below, with a linear structure Branched polymers: have side branch chains that are bonded to the main chain Cross linked polymers: have adjacent chains linked by covalent bonds. Polymers with cross-linked structure are called thermosets or thermosetting plastics (plastics that permanently harden through curing)  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Plastics (polymers) - Basic Characterizations: Examples: a) acrylics b) Polyethylene c) rubbers d) thermosets  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Plastics (polymers) - Basic Characterizations: Cross-linked polymers: Network polymers consist of three- dimensional networks of active covalent bonds Copolymers and terpolymers: Homopolymer: Polymers where the repeating units in the polymer chain are all of the same type Copolymer: Contain two types of polymers Terpolymers: Contain three types of polymers  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Crystallinity: Amorphous polymers: those polymers whose chains exist without long range order (think bowls of spaghetti)  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Crystallinity: Crystallinity: In some polymers it is possible to impart some crystallinity Crystalline regions called crystallites. Partial crystalline (semicrystalline) polymers considered two-phase materials (Note polymers can never be 100% crystalline) Effects of crystallinity: As crystallinity increases, stiffness, hardness, density and resistance to solvents and heat increases. Ductility, and rubberiness decrease  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Glass-transition temperature: Amorphous polymers don't have a melting point, but experience a distinct change in their mechanical behavior across a narrow range of temperature called the glass-transition temperature (Tg) At low temps polymers are hard, rigid, brittle and glassy At high temps they are rubbery or leathery Glasses exhibit this same behavior  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Glass-transition temperature:  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Glass-transition temperature:  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Polymer Blends: Improve the brittle behavior of amorphous plumbers below their Tg. Rubber-modified polymers: Blended with small quanties of an elastomer to enhance toughness and impact strength by limiting crack propagation Polyblends: blending involving several components Miscible blends: mixing without separation of two phases (similar to alloying metals) improving ductility.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Polymer Blends: Additives in Polymers Fillers: wood flour, silica flour, clay, powdered mica, short fibers of cellulose or glass Plasticizers: impart flexibility and softness by lowering the glass transition temp of the polymer Colorants: added pigments used to color the polymer Lubricants: May be added to reduce friction during subsequent processing  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Polymer Blends: Properties: Effects of UV radiation and oxygen: Weaken and break primary bonds, splitting long-chain molecules and making the material brittle. Accelerates degradation, coatings and antioxidants help protect against oxidation related degradation Flammability: Can be reduced by using less flammable raw materials, or through the addition of flame retardants  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Thermoplastics: Behavior and properties Plastics which retain their original hardness and strength after heating and cooling; though repeated heating and cooling may degrade them (thermal aging) Acrylics, cellulosics, nylons, polyethylenes, polyvinyl chloride (PVC)  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Thermoplastics: Behavior and properties In the glassy region (below the glass-transition temperature, behavior like an elastic solid) Stress and strain Torsion Where: Sigma is normal stress G is shear modulus E is elastic modulus Gamma is shear strain Epsilon true strain Tau is shear stress  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Thermoplastics: Behavior and properties a) Elastic b) Viscous (Dashpot vs. Spring) c) Viscoelastic (Maxwell model) d) Viscoelastic (Voight or Kelvin model)  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Thermoplastics: Behavior and properties  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Thermoplastics: Behavior and properties Effects of temperature and deformation rate Increasing temp decreases strength and modulus elasticity, increases toughness (resistance to fracture and deformation)  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Thermoplastics: Behavior and properties Effects of temperature and deformation rate  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Thermoplastics: Behavior and properties Above Tg thermoplastics polymers become leathery and the rubbery At higher temps (above Tm for crystalline thermoplastics) they become a viscous fluid (viscosity decrease as temperature and strain rate are increased) Viscous behavior similar to the strain-rate sensitivity of metals Where: Sigma is normal stress C is a constant Epsilon^o true strain rate m is 1 for Newtonian behavior, is higher for thermoplastics  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Thermoplastics: Behavior and properties Thermoplastics can undergo large uniform deformations in tension before fracture  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Thermoplastics: Behavior and properties Between Tg and Tm thermoplastics exhibit leathery and rubbery behavior depending on their structure and degree of crystallinity. Their viscoelastic modulus can be calculated as Where: Sigma is normal stress ee is elastic behavior ev is elastic flow  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Thermoplastics: Behavior and properties Viscosity (n) of polymers (the ratio of shear stress to shear strain rate) can be calculate as Where: Eta is viscosity of a polymer Etao is a material constant E is the activation energy K is the Boltzmann's constant (13.8 x 10-24) T is the temperature in Kelvin  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Thermoplastics: Behavior and properties Relationship between temp and viscosity Where  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Thermoplastics: Behavior and properties Creep and stress relaxation: Thermoplastics are particularly susceptible to creep and stress relaxation (Creep – gradual permanent deformation under constant load) (Stress relaxation – a steady decrease in force under constant applied deformation or strain)  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Thermoplastics: Behavior and properties Creep and stress relaxation: Creep Function Creep function (Voight model) Where K is the stiffness Eta is the coefficient of viscosty for the dashpot F is the applied force t is time  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Thermoplastics: Behavior and properties Creep and stress relaxation: Relaxation function Where k is the stiffness l is the elongation A is the instantaneous cross-sectional area t is time  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Thermoplastics: Behavior and properties Orientation: the alignment of the long-chain molecules in the general direction of the elongation, causing anisotropy Crazing: Some polymers (e.g. polystyrene) when subjected to tensile stress or bending develop localized and wedge-shaped narrow regions of highly deformed material typically containing about 50% voids. Eventually leading to cracking and failure Stress whitening: When subjected to tensile stress (e.g. folding/bending) the plastic becomes lighter in color due to the formation of micro voids Water absorption: Some polymers have the ability to absorb water (hygroscopy). The water acts as a plasticizing agent (increased ductility and formability). As moisture absorption increases, the Tg, yield stress and elastic modulus are all severely lowered  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Thermoplastics: Behavior and properties Thermal and electrical properties: Plastics generally characterized by low thermal and electrical conductivity, low specific gravity, and a relatively high coefficient of thermal expansion. Though plastics can be made conductive by doping (introducing certain impurities) Shape-memory polymers: Behave similarly to shape-memory alloys. The polymers can be stretched or compressed to a very large strains, and then when subjected to heat, light or a chemical environment they recover their original shape.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Thermosets: Behavior and properties Thermosetting polymers: Polymers with long-chain molecules cress-linked in a three-dimensional arrangement thus becoming one giant molecule with strong covalent bonds Image Courtesy: https://www.hpmanufacturing.com/wp-content/uploads/2022/04/hpm-soc- thermoplastics-vs-thermosets-v02-3.png  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Thermosets: Behavior and properties Thermosetting polymers: During polymerization, the network is completed, and the shape of the part being formed is permanently set. This curing (cross-linking) reaction is irreversible Thermosetting polymers do not have a sharply defined glass- transition temperature Thermoplastics are not as sensitive to temperure or rate of deformation, generally possessing better mechanical, thermal, and chemical properties, electrical resistance, and dimensional stability. Increased temperature will begin to degrade and char them  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Thermoplastics: General Characteristics and Applications Acetals Acrylics Acrylonitrile-butadiene-styrene (ABS) Cellulosics Fluorocarbons Polyamides Nylons Aramids Polycarbonates Polyesters Polyethylenes Polyimides Polypropylenes  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Thermoplastics: General Characteristics and Applications Polystyrenes Polysulfones Polyvinyl chloride (PVC)  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Thermoplastics: General Characteristics and Applications  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Thermosets: General Characteristics and Applications Alkyds Aminos Epoxies: Excellent mechanical and electrical properties, good dimensional stability, strong adhesive properties and good resistance to heat and chemicals. Maby be fiber-reinforced. Phenolics Polyesters Polymides Silicones  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o High-Temperature Polymers: Some polymers, and polymers blends for high temp applications are available (particularly in aerospace). High temp resistance may be for short term at relatively high temps. Or long term at lower temps. Ablatives used in short term exposure. Long term exposure confined to around (500oF ) o Electrically Conducting Polymers: Doping can be used to increase the electrical conductivity of a polymer. Doping is the addition of certain impurities , such as metal powder, salts, and iodides. Moisture absorption also increases conductivity. Irradition can alter a polymers electrical properties.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Biodegradable Plastics: Plastics contribute to about 10% of municipal solid waste Most plastics traditonally made form synthetic polymers derived from: a) Nonrenewable natural resources b) Are not biodegradable (microbial species in the environment will degrade a portion (or all of) the material) without producing toxic by-products) Starch based systems (extracted from potatoes, wheat, rice, and corn) Lactic-based systems (from fermented corn or other feedstock) Organic acids added to a sugar feedstock  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Biodegradable Plastics: Fully biodegradable plastics: Continually under development Long range performance of biodegradable plastics (both during their lifecycle and during their end of life) have not been fully assessed. Potential harm to recyclability and conservation Why aren't they more commonly used? Cost.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Recycling: Image Courtesy: https://hips.hearstapps.com/hmg-prod/images/recycling-symbols-cheat-sheet- copy-1582142071.png?crop=1.00xw:0.502xh;0,0.220xh&resize=1200:*  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Elastomers (Rubbers): General Characteristics and Applications: Elastomer – capable of recovering substantially in size and shape after a load has been removed - Amorphous polymers with: o Low Tg o Th ability to undergo large elastic deformations without rupture o Low hardness o Low elastic modulus Unstressed, stressed elastomer Image Courtesy: https://en.wikipedia.org/wiki/Elastomer  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Elastomers (Rubbers): General Characteristics and Applications: Rubber - capable of quickly recovering from large deformations Vulcanization – Rubber and sulfur chemically cross-linked with heat and pressure – used in auto tire manufacture. Once vulcanized the rubber annot be softened and reshaped Hardness – measured with a durometer, increases with additional cross-linking. Additives can be used to impart specific properties to the material Hysteresis – when stretched or compressed mechanical energy converted to heat Major Types: Natural, synthetic, silicones, polyurethane  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Reinforced Plastics: (Composites) Engineered materials, a combination of two or more chemically distant and insoluble phases whose properties and structural performance are superior to those of the constituents acting independently Examples: Straw and clay, reinforced concrete o Structure of Polymer-Matrix-Reinforced Plastics: Reinforced plastics consist of fibers (discontinuous or dispersed phase) in a polymer matrix (continuous phase)  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Structure of Polymer-Matrix-Reinforced Plastics: Matrix w/particles, matrix w/ short or long fibers, flakes, continuous fibers, laminate or sandwich composite structures using a foam or honeycomb core  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Structure of Polymer-Matrix-Reinforced Plastics:  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Reinforcing Fibers: Characteristics and Manufacture Polymer Fibers: Most commonly aramids (such as Kevlar)  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Reinforcing Fibers: Characteristics and Manufacture Ration of tensile strength-to-density and specific tensile modulus for various fibers  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Reinforcing Fibers: Characteristics and Manufacture  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Reinforcing Fibers: Characteristics and Manufacture Aramids and nylons absorb moisture, meaning hygrothermal (the movement of heat and moisture) stresses must be considered Spectra has ultrahigh molecular weight and high molecular-chain- orientation, better abrasion resistance and flexural fatigue as compared to aramid fibers, as well as high specific strength and stiffness. However, it has low melting point and poor interfacial fiber-matrix adhesion characteristics as compared to other fibers. Most syntehtic fibers used in reinforced plastics are extruded through tiny holes of a device called a spinneret.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Reinforcing Fibers: Characteristics and Manufacture Spinning: Melt Spinning -  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Reinforcing Fibers: Characteristics and Manufacture Spinning Melt Spinning: Nylon, olefin, polyester, and PVC Wet Spinning: Polymers dissolved in a solvent; spinnerets submerged in a chemical a bath – as the filaments emerge they precipitate in the chemical bath Image Courtesy: https://www.nal.res.in/sites/default/files/2020-08/FIBER%20WET%20SPINNING %20TECHNIQUE.png  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Reinforcing Fibers: Characteristics and Manufacture Spinning Dry Spinning: (thermosets carried by solvent). Polymers precipitated by evaporating the solvent in a stream of air or inert gas. Acetate, triacetate, polyether-based elastane, and acrylic fibers produced this way. Gel Spinning: Polymer not completely melted or dissolved in liquid, but instead are bonded at various stages in liquid crystal form. Filmanets first pass through air, and then are cooled further in a liquid bath (also called dry-wet spinning). Some high strength polyethylene, and aramid fibers made this way.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Reinforcing Fibers: Characteristics and Manufacture Glass fibers: Most widely used and least expensive of all fibers. Glass-fiber reinforced plastic (GFRP): contains 30 to 60% fibers by volume. Produced by drawing molten glass through small openings in a platinum die, the biers are then wound on a roll. Protective coatings (sizing) may be applied. The fibers treated with silane for improved wetting and bonding. o E type – calcium aluminoborosilicate glass o S type – magnesia-aluminosilicate glass o E-CR – high temp and acid corrosion resistance Carbon fibers: (more expensive than glass fibers) - low density, high strength.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Reinforcing Fibers: Characteristics and Manufacture Glass fibers: Most widely used and least expensive of all fibers. Carbon fiber: (continued): Made by pyrolysis(the process of inducing chemical changes by heat) of organic precursors, commonly polyacrylonitrile (PAN) due to lower cost. Rayon and pitch (residue from catalytic crackers in petroleum refining) also can be used. o Carbon fibers generally at least 92% carbon o Graphite fibers are usually more than 99% carbon Conductive graphite fibers: Enhance the electircal and thermal conductivity of reinforced plastics.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Reinforcing Fibers: Characteristics and Manufacture Boron fibers: boron deposited by Chemical Vapor Deposition (CVD) ton tungsten and carbon fibers. Good strenght and stiffenss in tension and compression, as well as resistance to high temperatures. Higher density, and weight as well as expense. Misc. Fibers: Silicon carbide, silicon nitride, aluminum oxide, sapphire, steel, tungsten, molybdenum, boron carbide, born nitride, and tantalum carbide o Whiskers:used as reinforcing fibers, tiny needleklike single cristles 1-10 µmin diameter.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Reinforcing Fibers: Characteristics and Manufacture Cross section of a tennis racket with graphite and Aramid (Kevlar) reinforcing fibers. A cross section of boron fiber reinforced composite material  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Fiber Size and Length: Fibers in reinforced plastics typically less than 0.01 mm. Strong and rigid in tension, low size means low chance of defects. Short Fibers – aspect ratio (ratio of width to height) 20-60 Long fibers- aspect ratio 200-500 -Generally, for a given fiber, if the mechanical properties of the composite improve as a result of increasing the fiber length, then the fiber is denoted as a short fiber. When mechanical properties do not improve – long fiber Discontinuous Fibers - Continuous fibers – Roving (slightly twisted strands of fibers, Woven (similar to cloth) yarn (twisted strand) and mats of various combinations  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Matrix Models: Matrix reinforced plastics Support and transfer the stress to the fibers which carry most of the load Protect the fibers from physical damage and the environment Reduce propagation of cracks in the composite by virtue o the ductility and toughness of the plastic matrix o Matrix material examples: Epoxy, polyester, phenolic, fluorocarbon, polyethersulfone, or silicon. Most commonly epoxies and polyesters.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Properties of reinforced plastics: Type, shape and orientation of reinforcing material Length of the fibers Volume fraction of the reinforcing material.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): Effects of the percentage of reinforcing fibers and fiber length on Reinforced Nylon  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): Effects of the percentage of reinforcing fibers and fiber length on Reinforced Nylon  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Properties of reinforced plastics: Critical factor in reinforced plastics is the strength of the bond between the fiber and the polymer matrix. Weak bonding in the composite causes fiber pullout and delamination (particularly under adverse environmental conditions) Image Courtesy: https://upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Delamination-CFRP.jpg/1200px-Delamination-CFRP.jpg  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): Fibers 10 µm in diameter with random orientation, and fracture surface of a graphite-fiber reinforced epoxy composite. Note the fibers are 9-11 µm in diameter and are all aligned in the same direction.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): Tensile strength of glass-reinforced polyester as a function of fiber content and fiber direction in the matrix.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): Tensile strength of glass-reinforced polyester as a function of fiber content and fiber direction in the matrix.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Reinforced plastics can be optimized for specific service conditions. I.E. in a pressure vessel subjected to biaxial forces, the fibers can be crisscrossed in the matrix. Image Courtesy: https://www.m-chemical.co.jp/carbon-fiber/images/case/pressure/pressure-item-img01.jpg  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Strength and elastic modulus of reinforced plastics: Where: Ec is the elastic modulus of the composite x is the fiber volume fraction Ef is the elastic modulus of the fiber Em is the elastic modulus of the matrix Ff / F the load fraction fiber/matrix m Af is the cross-sectional area of the fiber Am is the cross-sectional area of the matrix  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Applications of reinforced plastics: Fiberglass Aircraft (Boeing 787 50% weight composite) Electrical equipment Sporting goods Spacecraft  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Processing of plastics  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Processing of plastics: Extrusion - pellets Image Courtesy: https://www.canadianenergycentre.ca/wp-content/uploads/2021/10/GettyImages-1248463993-scaled.jpg  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Processing of plastics: Extrusion  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Processing of plastics: Extrusion  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Processing of plastics: Extrusion Image Courtesy: https://esi-extrusion.com/wp-content/uploads/2023/12/Job1313blue.jpg https://www.extruderscreens.org/img/extruder-screen-different-mesh.jpg  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Processing of plastics: Sheet and film extrusion  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Processing of plastics: Sheet and film extrusion  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Processing of plastics: Extrusion of plastic tube, and coextrusion Image Courtesy: https://www.researchgate.net/publication/269132085/figure/fig2/AS:295301928767494@1447416874795/Final-spider-head-geometry.png  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Processing of plastics: Injection molding  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Processing of plastics: Injection molding – Molds: Cold-runner two-plate  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Processing of plastics: Injection molding – Molds: Two-plate  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Processing of plastics: Injection molding – Molds: Three-plate  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Processing of plastics: Injection molding – Molds: Hot-runner  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Processing of plastics: Injection molding – Molds: Metallic embedded components  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Processing of plastics: Injection molding – Machines:  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Processing of plastics: Injection molding – Reaction-injection molding  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Processing of plastics: Injection molding – Overmolding ice-molding: Used for producing, in one operation, hinged joints and ball-and-socket joints. Two different plastics used so no bond forms between the two. Ice-cold molding: Same kind of plastic used; however cooled inserts used to ensure no bond forms between the two pieces  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Processing of plastics: Structural-foam-molding: used to make plastic products with a solid skin and a cellular inner structure. o Injection foam molding (gas assist moldings) thermoplastics are mixed with a blowing agent (usually an inert gas) or a chemical agent that produces gas during mold which expands the polymer leaving a cellular core and rigid skin. Image Courtesy: https://www.universalplastics.com/wp-content/uploads/2019/11/Structural-Foam-Injection-Molding-Process.jpg  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Blow molding: a modified combination of extrusion and injection molding. Injection blow molding: a short tubular preform (parison) is first injection molded. The parison can be stored and used for future molding, or used immediately. Hot air is injected into the parison which expands and fills the mold cavity. Multilayer blow molding involves the use of coextruded tubes, or parisons, allowing the use of multilayer structures.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Blow molding process for making plastic bevarge bottles from tubing, and using a preformed parison  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Three station Injection-Blow-Molding machine  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Rotational molding (rotomolding, rotocasting)  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Thermoforming process for thermoplastic sheet  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Compression molding – Positive, semipositive, and flash, die design w/undercuts  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Compression molding – Positive, semipositive, and flash, die design w/undercuts  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Casting – Similar to metal casting, liquid plastic heated and poured into a mold o Potting and encapsulation- (used in electrical nd electronics industry) casting plastic around an electrical component, totally embedding it. Potting – performed in a housing or case which becomes an integral part of the product Encapsulation – The component is covered with a layer of the solidified plastic. May be partial  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Casting – Casting, Potting, and encapsulation of plastics  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Foam molding – Examples: Styrofoam cups, insulating blooks, shaped packaging materials Expandable polystyrene made by placing polystyrene beads containing a blowing agent in a mold and exposing them to heat (usually steam). The beads expand to the shape of the mold Image Courtesy: https://www.offshore-technology.com/wp-content/uploads/sites/20/2021/10/shutterstock_1255157578.jpg  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Polyurethane foam processing – Examples cushions and insulating blocks. o Cold Forming and Solid-Phase forming: Cold working: e.g. rolling, deep drawing, extrusion, closed-die foring, coining, and rubber forming can all be used on thermoplastics at room temperature (cold forming), contingent on a) Material ductility at room temp b) Material deformation must be nonrecoverable Advantages – Strength, toughness, and uniform elongation of the material are increased High molecular weight polymers can be used to make parts with superior properties Forming speeds not affected by thickness, due to lakc of heating Short cycle times compared to molding  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Solid-phase forming - (about 10o to 20o C) below the melting temp of the plastic, lower springback than cold-working. NOt as widely used as hot-processing, restricted to special applications.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Processing Elastomers: Thermoplastic elastomers are polymers in terms of their processing characteristics; however they are elastomers in terms of function and performance. Calendaring – warm mass of the elastomer feedstock is fed through a series of rolls (masticating rolls) and is then stripped off in the form a sheet.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Processing Elastomers: Thermoplastic elastomers are polymers in terms of their processing characteristics; however they are elastomers in terms of function and performance. Dipping (dip molding) - e.g. gloves, ballons, swim caps. A solid metal form, such as in the shape of a hand for making gloves, is repeatedly dipped into a liquid compound that adheres to the form. The compound is then vulcanized (usually in steam). Image Courtesy: https://blog.ammex.com/wp-content/uploads/2022/12/AdobeStock_236203276.jpg  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Processing of Polymer-Matrix-Reinforced plastics: Great strength and stiffness to weight, and creep resistance. High cost of processing Prepregs - (fibers already impregnated with reinforcement) the continuous fibers are aligned and subjected to surface treatments to enhance their adhesion to the polymer matrix Sheet-molding compound (SMC) – Continous strands of reinforcing fiber are chopped into short fibers and deposited over a layer of resine past (usually a polyester mixture carried on a polymer film (e.g. polyethylene). A second layer of resin paste is deposited on top dn the hseet is pressed through rollers, then manured.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Manufacturing process for polymer matrix composite and Boron-Eposy prepreg tape  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Manufacturing process for producing reinforced-plastic sheets.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Processing of Polymer-Matrix reinforced plastics Illustration of calendaring  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Processing of Polymer-Matrix reinforced plastics Bulk-molding Compound (BMC) - Compounds in the shape of billets (generally up to 50 mm in diameter) processed into products with flow characteristics similar to dough (sometimes called dough- molding compounds) Thick-molding compound - Combines the characteristics of BMCs (lower cost) and SMCs (higher strength). Usually, injection molded using chopped fibers of various lengths. Used in electrical components due to its high dielectric strength.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Molding: Compression molding w/ reinforced plastics – Bulk material of polymers, fibers and additives is shaped into a log befor being cut to length and placing it in the mold. Vacuum bag-molding – Prepregs laid in in a mold, then vacuum applied through a covering layup with a plastic bag. Autoclaves used where additional heat and pressure needed. Contact-molding used in making products with high surface are to thickness rations. (e.g. swimming pools, boats, tubs). A single male or female mold used.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Molding: Vacuum-bag forming and pressure bag forming Image Courtesy: https://blog.ammex.com/wp-content/uploads/2022/12/AdobeStock_236203276.jpg  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Molding: Hand Lay-up and Spray up Open mold processing  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Molding: Boat building Image Courtesy: https://images.boats.com/resize/wp/2/files/2000/08/boat-building-1.jpg  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Molding: Resing transfer molding – A resin, mixed with a caalyste is forced by a piston type positive displacement pump into a mold cavity filled with fiber reinforcement. Transfer/injection molding – An automated operation that combines the processes of compression molding, injection molding, and transfer molding.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Filament Winding, Pultrusion, and Pulforming Filament Winding – Resin and the fibers are combined at the tie of curing. Reinforcements are impregnated by passing them through a polymer bath.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Filament Winding, Pultrusion, and Pulforming Filament winding process and aluminum liners for Boeing 767 slide rafts  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Filament Winding, Pultrusion, and Pulforming Pultrusion – Parts with high length-to-cross-sectional area rations and various constant profiles, i.e. rods, tubing. Continuous reinforcement (roving or fabric) pulled through a thermosetting polymer bath.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Filament Winding, Pultrusion, and Pulforming Pulforming – Constant cross section parts. After finishing the pultrusion process the composite is place in a die and cured.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Product Quality Internal voids and gaps between layers of materials – gases developed during processing must be allowed to escape through the vacuum bag to avoid porosity. Improper curing may cause microcracks – ultrasonic scanning can help to detect this.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Additive Manufacturing (AM) Prototyping, and Rapid prototyping A sample sliced CAD Model  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Additive Manufacturing (AM) Prototyping, and Rapid prototyping  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Additive Manufacturing (AM) Stereolithography (STL) or vat photopolymerization – a liquid photo polymer is cured into a specific shape through the applications of laser light.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Additive Manufacturing (AM) Stereolithography (STL) or vat photopolymerization – a liquid photo polymer is cured into a specific shape through the applications of laser light.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Additive Manufacturing (AM) Stereolithography (STL) or vat photopolymerization –  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Additive Manufacturing (AM) Polyjet - (similar to inkjet printing) printing heads deposit a photopolymer onto a build tray. UV bulbs cure an harden the photopolymer layers. Fused Deposition Modeling (FDM) - (aka roboextrusion) An extruder head moves in two principle directions over a table which controls the (z depth) of the build. A thermoplastic filament is extruded through the head of a heated die to build the part in layers (slices) Big Area Additve Manufacturing (BAAM)  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Additive Manufacturing (AM) FDM Process and Machine  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Additive Manufacturing (AM) Powder bed process – utilize powder as the workpiece material that is deposited layer-by-layer in a bed or build chamber or cylinder. Selective Laser Sintering (SLS) Polymeric or metallic powders sintered into an individual object. (Aka direct metal laser sintering (DLMS). The metal is actually melted instead of sintered.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Additive Manufacturing (AM) Selective Laser Sintering Process  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Additive Manufacturing (AM) Electron beam melting – Similar to SLS but more energy efficient, however an electron beam is used as the energy source to melt metal (e.g. titanium, stainless steel, cobalt-chrome) powder. Binder jet printing - (binder jetting) a print head deposits an inorganic binder material onto a layer of nonmetallic or metallic powder. A piston supports the powder bed and is incrementally lowered before a new layer is deposited. The finished part is then sintered (if metal powder used) to burn of the binder and partially fuse the powders.  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Additive Manufacturing (AM) Three-dimensional printing process  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Additive Manufacturing (AM) Laser-Engineered Net Shaping – A laser beam used to melt and deposti metal powders layer by layer. This process is called Laser- engineered net Shaping (LENS) or Direct Metal Deposition (DMD). Performed in argon environment. Friction stir modeling (FSM) - Similar to friction stir welding, powder is delivered to a build location by pushing it into a rotating tube, the friction between the tube and substrate densify the poser into a solid material. No Heat Affect Zone (HAZ)  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Additive Manufacturing (AM) - Summary  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Additive Manufacturing (AM) - Summary  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Additive Manufacturing (AM) - Summary  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Direct (Rapid) Manufacturing and Rapid Tooling Investment casting using rapid-prototyped wax part patterns  Lesson # 8 - Polymer Processing Polymer Processing and Additive Manufacturing (AM): o Direct (Rapid) Manufacturing and Rapid Tooling Investment casting using rapid-prototyped wax part patterns