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Thermoplastic Materials Engineering Plastics. Engineering Thermoplastics Replace metallic parts –Strength and stiffness –Retention of properties over.

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Presentation on theme: "Thermoplastic Materials Engineering Plastics. Engineering Thermoplastics Replace metallic parts –Strength and stiffness –Retention of properties over."— Presentation transcript:

1 Thermoplastic Materials Engineering Plastics

2 Engineering Thermoplastics Replace metallic parts –Strength and stiffness –Retention of properties over range of temperatures –Toughness to withstand incidental damage –Dimensional stability Low creep Low CTE –Withstand environmental factors (UV, O 2, chemicals) –Shaped easily

3 Engineering Thermoplastics Compared to commodity plastics –More expensive –The commodity resins are all lacking some critical property –Some Engineering Thermoplastics are formed through the condensation polymerization process

4 Polyamides or Nylons (PA)

5 ( ) n [ ] a [ ] b Polyamides or Nylons (PA) [ ] a [ ] b

6 PA General Family Characteristics Polarity Crystallinity Sharp meltpoint Strength Comparison of higher & lower nylon numbers

7 PA General Family Characteristics Transparent (barely)—cook in bag (turkey) Anti-friction—not like PTFE but good Toughness—excellent Fatigue resistance—excellent Water absorption—a weakness (.2-2.5%— must be dried for injection molding) Highly crystalline

8 Nylon 6,6 Hexamethylenediamine (6 carbons)

9 Nylon 6,6 Adipic Acid (6 carbons)

10 Nylon 6,6 Water Nylon 6,6

11 Nylon 6 Amine Group Acid Group

12 Nylon 6 Water

13 Properties of Specific Nylon Types Nylon 6,6 – General Nylon 6 – Copycat Nylon 6,10 – Less water absorption Nylon 6,12 – Flexibility and less water Nylon 2,2 – Strength

14 Processing Nylon Injection molding –Shrinkage—crystallinity—.018 in/in –Dry it first Extrusion –Low melt viscosity –Be careful of decomposition Fibers –Drawing –Crystallization –Orientation

15 Nylon History Nature of polymer bonding not understood Carothers Difunctional monomers Polymers—1000 units long –Larger units—molecular still to eliminate water Control of melting point and length –Many combinations of polyesters –Trying polyamides –Settling on 6,6 Carothers death –3 weeks after patents Tremendous success –Name Delawear, Wacra, Norun, Nuron, Nulon, Nilon, Nylon

16 Aramids

17

18 Acetals or Polyoxymethylenes (POM)

19 ( )n)n

20 Acetal General Family Characteristics Mechanical—do not embrittle, good impact strength Moisture—very little (shower heads) Chemical resistance—very high, resists stains, sensitive to strong acids and bases Weathering—fair Thermal—200 o F Electrical—good Machining—like cutting brass Adhesion—epoxy glues

21 Processing Acetals Do not heat above 440 o F Melt viscosity is not too dependant on temperature

22 Acetal Copolymer ( ( n

23 Thermoplastic Polyesters (PET/PBT)

24 ( )n)n

25 Thermoplastic Polyester General Family Characteristics PET –Higher mechanical stiffness –Strength by orienting chains not by H-bonding –Get 50% crystallinity forced by mechanical stretching PBT –crystallizes rapidly –processes faster –lower overall properties

26 Processing PET Shape it (film, tape, fiber, extrude, etc) –Amorphous structure Reheat and stretch in strength direction(s) Cool to below T g

27 Specific TP Polyester Types Dacron fiber—mix with cotton or wool-gives permanent creases Kodel – photo film Mylar—transparencies, tapes PETG—glycol modified, amorphous, like PVC

28 Polycarbonate

29 ()n)n

30 History Solvent resistance (DuPont) GE-Lexan Properties –Polar –Stiffness of backbone –Long repeat unit

31 Properties Solvent sensitivity—poor but nice for joining Clear—except for UV yellowing, slight crystallinity Hard Ductile—nailed, sawed, drawn, punched, sheared, drilled Tough—helmets, light covers, windows, roadside signs, bullet proof shields Dimensional stability—low creep Electrical resistance—good but not fantastic Machining—good

32 Acrylics (PAN, PMMA)

33 ()n)n ( )n)n

34 Properties Color (transparency)—20 years w/ <10% change Weathering—best Mechanical properties—average except for impact (brittle) Chemical—chlorinated solvents attack it, acetone gives it cracks Electrical—good

35 Uses Signs Counter tops—Corian Decorative pieces Floor waxes Paint, fingernail polishes Contact lenses, glasses

36 Processing Casting (sheets)—syrup Injection molding—good Thermoforming—ok but brittle Machining—similar to wood

37 Flouropolymers (PTFE, FEP, PFA)

38 )n)n )n)n ( (

39 History of Discovery Chambers plant –Making Freon –Gas cylinder

40 Properties Most are strengthened by the tight bond between the Fluorine and the Carbon atoms –Slippery (anti-stick surfaces) –Chemical inertness –High temperature melting –Non-flammable –High electrical resistance –Very dense— (high melt viscosity)

41 Uses O-rings Non-stick surfaces Insulation-electrical Lubricant Coatings Gears

42 Processing Not processable by extrusion or injection molding –Sintering Put in approx shape and heat–620 o F Similar to processing powdered metals Fusion –Ram extrusion Compaction Rods and tubes –Calendaring Very poor adhesion

43 High Performance Thermoplastics

44 PPO Properties Thermal stability—excellent (650 o F) High HDT = 375 o F Good cold properties (-275 o F) Low water absorption Low heat expansion Good solvent resistance, but can be solvent welded

45 PPO uses Used to replace stainless steel for surgical equipment Replace thermosets Pump housings Valve components Video terminal housings

46 Polyaryletherketones (PEEK, PEK, and Others)

47 Ether Linkage Ketone Linkage

48 Polysulfones (PSU and PES)

49

50 Properties Resistant to oils Heat stability (300 o F) Creep resistance SO 2 group adds stiffness More dimensionally stable than PPO Toughness—good

51 Uses Hot water pipes Coffee pots Dishwasher components Automobile applications near engines Compete with thermosets, but can be injection molded

52 Thermoplastic Polyimides (PI and PAI)

53 ( )n)n )n)n (

54 Properties Very stiff Highest thermal stability PI cannot be melted or melt processed PAI can be (Torlon) PI is sintered (Vespel) PI film is cast as monomers and heated to polymerize (Kapton)

55 Uses PI is used in circuit boards High temperature parts Low friction bearings, sliding parts Gears

56 Cellulosics

57 Nitrocellulose –Gun cotton Cellulose nitrate –Lacquers and plastics

58 Fire Hard –Plasticized with camphor Water repellent Fire Properties

59 Types of Cellulosics Rayon –Viscose process Cellophane Methyl cellulose –Filler –Edible

60 Thank You

61 Nylon History Carothers –Iowa—BS –Illinois—PhD –Harvard—Teach –DuPont—basic research

62 Polyphenylenes (PPE, PPO, and PPS) PPO


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