PROCESSING OF POLYMERS and POLYMER COMPOSITES PE335, Lecture 7 PROCESSING OF POLYMERS and POLYMER COMPOSITES
PE335_Lecture7_ Processing© Caroline Schauer 2008 Background PE335_Lecture7_ Processing© Caroline Schauer 2008
Thermoplastics and Thermosets PE335_Lecture7_ Processing© Caroline Schauer 2008
Thermoplastics and Thermosets - can be reversibly cooled and reheated repeatedly, i.e. recycled - ex: polyethylene, polypropylene, polystyrene, etc. Thermoset – forms a network – degrades (not melts) when heated – mold the prepolymer then allow further reaction – ex: unsaturated polyester, urethane, epoxy Viscoelastic PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 Viscoelasticity PE335_Lecture7_ Processing© Caroline Schauer 2008
Thermal Characteristics of Linear Polymers: Thermoplastics Tg = glass transition temperature – glass to rubber transition Tm = crystalline melting point – typically 1.5Tg if the polymer can crystallize T = service or “operation” temperature Processing Temperature ≥ Tg +100˚C amorphous polymers form a melt ≥ Tg + 50˚C semicrystalline polymers form a melt PE335_Lecture7_ Processing© Caroline Schauer 2008
Thermal Characteristics of Linear Polymers: Thermosets Tg = glass transition temperature – glass to rubber transition T = service or “operation” temperature Cure Temperature Determined by the (curing) chemical reaction PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 Thermal Transitions Amorphous vs. Crystalline Modulus Amorphous Crystalline (Stiffness) Amorphous TG Crystalline TG Crystalline TM Temperature PE335_Lecture7_ Processing© Caroline Schauer 2008
Thermal Transition: Calorimetery PE335_Lecture7_ Processing© Caroline Schauer 2008
Service Temperature Tests Vicat Softening Point ASTM D-1525 is the temperature at which a .040" steel rod will penetrate into a solid sample. Heat Deflection ASTM D-648 is the temperature at which a center loaded bar deflects 0.010" under a stress of 66 psi or 264 psi. PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 Thermal Transitions As the side chain becomes “longer”,Tg becomes lower. PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 Melt Flow Index . . is defined as the mass of polymer, in grams, flowing in ten minutes through a capillary of a specific diameter and length by a pressure applied via prescribed alternative gravimetric weights for alternative prescribed temperatures. (ASTM D1238 and ISO 1133). . . is inversely proportional to viscosity of the melt at the conditions of the test, though it should be borne in mind that the viscosity for any such material depends on the applied force (shear stress). PE335_Lecture7_ Processing© Caroline Schauer 2008
Processing Temperature PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 Polymers Processing Converting raw plastics to useful final products with desirable properties Plastics Polymers (Plastics = Polymer + Additives) PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 Additives Fillers: to improve mechanical properties and reduce cost. Plasticizers: to improve flexibility, ductility, and toughness of polymers. Their presence also produces reductions in hardness and stiffness. Stabilizers: to protect against atmospheric oxidation or UV radiation. Colorants: to classify application of materials. Flame retardants: may function by interfering with the combustion process through the gas phase, or by initiating a chemical reaction that causes a cooling of the combustion region. etc PE335_Lecture7_ Processing© Caroline Schauer 2008
Compounding/ Master Batch Compounding is the process by which colour or additives are added to the basic thermoplastics material. It involves melting the thermoplastics material then mixing it with the required pigments and/or additive material in an extruder. The melt is then extruded and chopped into pellets as it cools, which can then be used directly by the plastics processor. An associated process is masterbatch. This is where a high concentration of pigment and/or additives are dispersed in a carrier medium which can then be used directly by the processor in small quantities to pigment or modify the virgin polymer material. PE335_Lecture7_ Processing© Caroline Schauer 2008
Compounding Pelletizer PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 Processing Methods PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 Processing Overview The molten plastic is forced through “channels” in order to be shaped into products. The “formed” plastic is solidified by cooling, e.g. EXTRUSION (80% of plastics processed by extrusion) Pipes Sheet Film Profile INJECTION MOLDING BLOW MOLDING Blow Stretch-blow THERMOFORMING COMPRESSION MOLDING (tires) FIBER SPINNING etc PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 Processing Methods Thermoplastic Injection Molding Extrusion Blow Molding Injection-blow Molding Compression Molding Calendaring Rotational Molding Thermo-forming (Vacuum Forming) Cold Drawing Casting Fiber Spinning Themosets Reaction Injection Molding (RIM) Compression Molding Casting Elastomer Extrusion Short Fiber Composites Hand Layout Injection Molding Sheet Molding (Compression) Bulk Molding (Compression) Continuous Fiber Composites Pultusion Filament Winding Lamination PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 Injection Molding PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 Injection Molding * PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 Process Cycle PE335_Lecture7_ Processing© Caroline Schauer 2008
Simulated Process Cycle http://alexpb.com/notes/articles/category/manufacturing/ PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 Compression Molding Compression molding is almost exclusively used for thermosets, elastomers and short-fiber composites. PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 Extrusion Ancillary Equipment i.e. Sizing, Cooling, Cutting, Printing,… Produces continuous lengths having constant cross-sectional geometries. PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 Blow Molding Injection-blow Molding Extrusion Blow Molding PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 Blown Film Extrusion The extruder is fitted with an annular die, pointing (usually) upwards. The tube produced is inflated with air and at the same time is drawn upwards in a continuous process. PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 Fiber Spinning The strength of fibers is improved by a post forming process called drawing. PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 FLAT FILM CASTING PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 THERMOFORMING PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 ROTATIONAL MOLDING PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 CALENDERING PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 COATING PE335_Lecture7_ Processing© Caroline Schauer 2008
Processing of Thermosets and Composites PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 Compression Molding Compression molding is almost exclusively used for thermosets, elastomers and short-fiber composites. PE335_Lecture7_ Processing© Caroline Schauer 2008
Reaction Injection Molding (RIM) Polyol and Isocyanate liquids are injected into a closed mold and reacted to form a polyurethane. PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 Polyurethane Polyurethane can be made in a variety of densities and hardnesses by varying the type of monomer(s) used and adding other and other additives. Diol Diisocyanate PE335_Lecture7_ Processing© Caroline Schauer 2008
Spray Coating of Liquid Epoxy PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 Epoxy Resins The most widely used epoxide monomer is the diepoxide prepared by treating one mole of bisphenol A with two moles of epichlorohydrin PE335_Lecture7_ Processing© Caroline Schauer 2008
Epoxy Cross-linking (Hardening) PE335_Lecture7_ Processing© Caroline Schauer 2008
Unsaturated Polyesters − crosslinking (curing) Unsaturated portion Polyesters must have unsaturated portions to crosslink PE335_Lecture7_ Processing© Caroline Schauer 2008
Polyesters − crosslinking (curing) Initiator I ● C C C C PE335_Lecture7_ Processing© Caroline Schauer 2008
Fiber Reinforced Composite Processing PE335_Lecture7_ Processing© Caroline Schauer 2008
Fiber-Reinforced Composites Processing of Fiber-Reinforced Composites PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 All-composite Jet PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 Hand Lay-Up Method mold is treated with mold release agent; (2) thin gel coat (resin) is applied; (3) when gel coat has partially set, layers of resin and fiber are applied, the fiber is in the form of mat or cloth; each layer is rolled to impregnate the fiber with resin and remove air; (4) part is cured; (5) fully hardened part is removed from mold. (6) Parts are stored for full cure. PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 Spray-Up Method PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 SUNSEEKER 120 Built at Sunseeker International UK. She was successfully launched in Poole in 2006 before being transferred to the owner. Her hull was crafted from composite. The motor yacht main superstructure is made for the most part using composite. PE335_Lecture7_ Processing© Caroline Schauer 2008
Reinforced Reaction Injection Molding Reinforced reaction injection molding (RRIM) - similar to RIM but includes reinforcing fibers, typically glass fibers, in the mixture. Advantages: similar to RIM (e.g., no heat energy required, lower cost mold), with the added benefit of fiber‑reinforcement PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 Pultrusion Process PE335_Lecture7_ Processing© Caroline Schauer 2008
Sheet Molding Compound Polyester PE335_Lecture7_ Processing© Caroline Schauer 2008
Resin Transfer Molding (Polyester or Epoxy) Preform is inserted into a matched die mold. The heated mold is closed and the liquid resin is injected The part is cured in mold. The mold is opened and part is removed from mold. PE335_Lecture7_ Processing© Caroline Schauer 2008
Fiber Preform Architcture PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 Filament Winding Polyester or Epoxy Glass or Carbon PE335_Lecture7_ Processing© Caroline Schauer 2008
FILAMENT WINDING: Overview FILAMENT WINDING is a continuous process for fabricating a composite structure in which continuous reinforcements (filament, wire, yarn, tape, or other), either previously impregnated with a matrix material or impregnated during winding, are placed over a rotating form or mandrel in a prescribed way to meet certain strength conditions. When the required number of layers is applied, the wound form is cured and the mandrel can be removed or left as part of the structure. PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 Pipes PE335_Lecture7_ Processing© Caroline Schauer 2008
PE335_Lecture7_ Processing© Caroline Schauer 2008 Tanks PE335_Lecture7_ Processing© Caroline Schauer 2008