Thermoplastic Materials (Engineering Plastics) High strength and stiffness; some may require reinforcement Retention of mechanical properties over a wide range of temperature (esp. at high temp) Toughness that is sufficient to incidental impact (occur during applications) Dimensional stability throughout the temperature range of normal use Easy to shape and finish

Engineering Plastics Other properties for specific applications; Abrasion resistance Extended fatigue life Lubricity Electrical properties, etc

Engineering Plastics Examples –Polyamides/nylon, TP polyester, polycarbonate, PMMA, fluoropolymer, etc

Polyamides or Nylon (PA) Refer to polymer repeating units for PA Subscript a and b indicates that in nylon family the CH 2 groups can vary from 1 particular nylon type to another The polarity of the amide group makes nylon sensitive to polar solvent such as water (absorptivity of water is a problem in processing because nylon resin must be dried before any processing process) Tensile strength and modulus can decrease by 20% with water absorption Polymer repeating units for polyamides

Specific Nylon Types Number of carbons in the molecular sections between amide groups determine various types of nylon For example, if the nylon is made from a six-carbon diamine (a), and a 12- carbon diacid (b), the resulting polyamide namely nylon (6/12) or nylon-six- twelve Polyamide can also be formed by one monomer with amine group on one end and an acid group on the other (c), namely nylon (6)

Aramid Contain amide group with benzene rings between them This polymer has been given a generic name of aramid. When made into fiber, the materials is called kevlar The aramids are nonburning, solvent resistant, and very high melting

Thermoplastic Polyesters (PBT/PET) Example; polyethylene terephthalate (PET) & polybutylene terephthalate (PBT) PET used for soft drink bottle (tough & inexpensive), high performance film (magnatic tapes, etc) and fiber (textile) PBT- easier processing because it crystallizes more rapidly than PET The mechanical properties of PBT are lower than PET Applications of PBT- slide bearing, roller bearing, gear, protective headgear, etc. Polymer repeating unit for the most common thermoplastic Polyester where m can be 1 (for PET) and 2 (for PBT)

Properties of PBT & PET Contain polar carbon-oxygen double bond, but the percentage is small for entire molecules, thus it has low moisture absorptivity low moisture absorptivity give consistent electrical properties- led to numerous electrical applications (lamp socket, switches, connectors, etc) Excellent dimensional stability Melts of PBT & PET are of medium viscosity compared to other engineering plastics

Polycarbonate (PC) Formed by condensation polymerization, resulting in a carbon that is bonded to three oxygen (characteristics of carbonate) Large, complex and aromatic structure- noncrystalline yet it is nearlly strong as highly crystalline nylon Can be used continuously up to 135C Unique combination of properties; high optical clarity and toughness Applications; camera bodies, hair dryer, safety helmets, pump impellers, etc Polymer repeating unit for PC Try to relate the PC structure with its properties!!!

Acrylic (PAN, PMMA) Acrylic group is dominated by 2 resins, polyacrylonitrile (PAN) (used for blending with other resin and fiber)and PMMA (used for molding) PMMA compete with other engineering thermoplastic PMMA is atactic, thus amorphous Most important property-optical clarity (92% light transmittance)-the highest of any plastic materials The lowest sensitivity to UV light of other plastics, low oxidation sensitivity, whether resistance Polymer repeating unit for PMMA

Acrylic (PMMA) Shows better initial & long term optical properties (compete with PC), but not as tough as PC. Excellent optical properties- windshields (in planes and helicopter), outdoor sign, automobile tail-light, compact disc, etc PMMA scratch easily (solved with coated grade) PMMA has a significant advantage in price compared to PC

Fluoropolymer The presence of fluorine in the polymer-results in unique physical, mechanical & chemical properties Teflon- DuPont brand name Flourine is the most electronegative of the element, and strongly attracts electron to it- thus forming very stable bond with low chemical reactivity- nonstick property Chemical inertness and lack of bonding important in nonstick coating application on pan Polymer repeating unit for polytetrafluoroethylene (PTFE)

Applications; medical devices, industrial roller for printing, photocopying, process guide and dies Superior solvent resistance (not attack by solvent at operating condition) Nonflammable-used in electrical insulation Presence of fluorine atom results in problem in toxicity if fluoropolymer decomposes. Service temp; 260C Fluoropolymer

Thermoplastic in Medical Applications Every day, plastics are involved in critical surgeries, life- saving efforts, and routine medical procedures. Plastic materials can be sterilized hundreds of times without degradation. Lightweight plastics are used to form replacement joints, non-surgical supports, and therapy equipment. Clear plastics provide visibility for transfusions, surgeries, and diagnostic equipment of all kinds. And plastics can be machined, molded, or formed into almost any shape imaginable.

Polysulfone One of the first high temperature thermoplastic materials to be sterilizable by all techniques polysulfone meets the demanding requirements of FDA and USP. The availability of a clear grade makes this material the only choice for sterilizable vacuum-formed medical equipment.

UHMW-PE (Ultra High Molecular Weight Polyethylene) The diverse uses of lot-controlled UHMW-PE range from standard wear applications to implantable products. Biocompatibility, self-lubrication, and wear resistance are among the major requirements of articulating surfaces made from UHMW-PE. The biological response to UHMW in soft tissue and bone has been well characterized by a history of clinical use.

Polyetherimide Because of its superior physical properties and its ability to withstand a wide spectrum of sterilization methods, Ultem is often specified as the material of choice in demanding reusable medical device applications.

Surgical Blades and Medical Blades are demanding critical components wide range of applications such as catheter cutting blades, endoscopic blades, diagnostic, orthopedic, plastic surgeries, lasik blades, laproscopic blades, and skin grafting blades surgical blade is tough to produce with the high level of sharpness required for cutting human tissue Bone SawSurgical Blades

This surgical instrument is manufacture under the highest standards of sharpness, consistency and durability. Originally the blades were made of uncoated stainless steel However, one problem resulted was tissue sticking to the blade To overcome this problem, coat the blade with nonstick material Surgical Blades and Medical Blades What is the suitable thermoplastic material to create nonstick coating on the surgical blade???

Aspect of structure that influence properties Structure within the Mer Structure within the molecules Structure between molecules

Structure within the Mer Include elements involved and bond energy, the bulkiness of the mer, side groups, etc. –Example; bond energy determine the thermal decomposition Flexibility and bulkiness of mer- influence crystallinity

Structure within the molecules Include stereoisomerism, branching, molecular weight and distribution, end groups, etc –Example; Stereoisomers of PP; isotactic, synditactic & atactic- influence crustallinity Branching- long or short; rarely or frequently along a chain

Structure between molecules The interactions between polymer molecules have strong influence on properties Example; cross linking, secondary bonding and crystallinity –Example Crosslinking- network is produced by joining short chain Secondary bonding- Van der Waals bond

Properties of polymer Thermal properties –Dimensional stability- Tg (noncrystalline portion of the polymer change from glassy to rubbery) –Thermal decomposition- occur when primary covalent bonds are ruptured –Thermal expansion –Thermal conductivity

Mechanical properties; it is categorized based on (also can be categorized based on tensile, impact, flexural, etc); –Stiffness –Strength –Toughness Properties of polymer

Chemical properties –Solubility- in various solvent –Permeability to gases or other molecules –Chemical resistance towards chemicals, environment & radiation Properties of polymer

Electrical & Optical properties –Dielectric properties- most polymers are good insulators, able to store electrical charge effectively, thus serving as good dielectric –Conductivity- most polymers are poor conductors, because primary chemical bonding is covalent- thus no free electron or ion to conduct charge –Optical properties such as color, transparency, etc Properties of polymer