Thermoplastics Polymers soften or melt on heating are called Thermoplastic Polymers Characterized by liner chain molecules Ex: Polyesterene , Polyethylene
Definition-Thermosetting Polymer A thermosetting polymer is a prepolymer in a soft solid or viscous state that changes irreversibly into an infusible insoluble polymer network by curing. Curing can be induced by action of heat or suitable radiation or both . A cured thermosetting polymer is called Thermostat
DIFFERENCES Thermosets Thermoplastics Resin Cost is low Resin Cost is High Exhibits moderate Shrinkage Is low shrinkage Exhibits good resistance Poor resistance to fluids to fluids and solvents and solvents Interlaminar fracture Interlaminar fracture toughness is low toughness is high
DIFFERENCES Thermosets Thermoplastics Long processing cycles Low processing cycle time Poor Recycling Recyclability and capabilities environmental protection More difficult to repair High reparability ability Good wetting and Draping difficulties adhesion to reinforcement
EPOXY The term epoxy is a general description of a family of polymers which are based on molecules that contain epoxide groups An epoxide is a cyclic ether with three ring atoms. This ring approximately defines an equilateral triangle, which makes it highly strained An epoxide group is an oxirane structure, a three-member ring with one oxygen and two carbon atoms.
EPOXY A polymer formed by reacting epoxide units is called a polyepoxide or an epoxy. Epoxy is a copolymer; that is, it is formed from two different chemicals. These are referred to as the "resin" or "compound" and the "hardener" or "activator". Epoxy, also known as PolyEpoxide, is a thermosetting polymer formed from reaction of an Epoxide "resin" with Polyamine "hardener". .
EPOXY Epoxies are polymerizable thermosetting resins containing one or more epoxide groups curable by reaction with amines, acids,amides, alcohols, phenols, acid anhydrides, or mercaptans. The polymers are available in a variety of viscosities from liquid to solid.
EPOXY The Common starting material : Diglycidyl Ether of Bisphenol A(DGEBA) which contain two epoxide groups , one at each end of the molecule
EPOXY Most common epoxy resins are produced from a reaction between Epichlorohydrin and Bisphenol-A The hardener consists of polyamine monomers, for example Triethylene tetramine (TETA). When these compounds are mixed, the amine groups react with the epoxide groups to form a covalent bond. Each NH group can react with an epoxide group from distinct prepolymer molecules, so that the resulting polymer is heavily crosslinked, and is thus rigid and strong
Manufacturing of Epoxy Resin Diluents – Reduce the viscosity Flexibility agents – make epoxy flexible Other agents – Protection against UV Curing agents – organic amino compounds (To obtain cross linking by introducing chemicals that react with the epoxy and hydroxyl groups between adjacent chains )
EPOXY Crosslinking :Stiffness, strengh increases but toughness decreases B-Stage: An epoxy before it is fully cross linked is said to be in stage B In stage B , epoxy has characteristic tackiness The curing reaction can be lowered by lowering the reaction temperature
PROPERTIES OF EPOXY Make an excellent matrix material because of their versatility, • Good handling characteristics, • Low shrinkage, • Excellent adhesive properties, • Flame resistant, • Good chemical resistance, • Good mechanical properties including toughness, • Offer considerable variety for formulating Prepreg resins, • Hot molding (cold molding rarely), • High smoke emission, • Curing temperature is 120-175°C (250-3500F), and • No by-products formed during cure
EPOXY Disadvantages : Brittleness and reduction in the properties in the presence of moisture Slower processing time then polyester More expensive then polyesters
EPOXY –Applications Used in Aircraft Construction Croyogenic applications Epoxy-nylon, Epoxy-amide have good retention of both tensile strength and elongation at cryogenic temperatures and are usually the only materials that will work well at these temperatures. Bridge Structures : Epoxy reinforced concrete Carbon reinforced Epoxy Structures Glass reinforced Epoxy Structures
POLYESTER (Thermosetting) Polyester is a category of polymers which contain the ester functional group in their main chain. The term "polyester" as a specific material most commonly refers to polyethylene terephthalate (PET) Esters are chemical compounds consisting of a carbonyl adjacent to an ether linkage
POLYESTER A condensation reaction between the GLYCOL ( Ethylene, Propylene, diethylene glycol) + Unsaturated Dibasic Acid = Linear Polyester
POLYESTER PET(polyethylene terephthalate) is made from Ethylene Glycol and Terephthalic Acid by splitting out water molecules (-H from alcohol and -OH from acid. The units are joined to make the ester group.
POLYESTER A simple representation is -[A-B-A-B-A-B]-.
Polyester- Properties Hard strong and extremely tough High abrasion resistance Low coefficient of friction Good chemical resistance Good surface appearance Electrical properties are stable upto the rated temperature limits
Polyester-Advantages The relatively easy accessible raw materials. The very well understood and described simple chemical process of polyester synthesis. The low toxicity level of all raw materials and side products during polyester production and processing
Polyester-Advantages The possibility to produce PET in a closed loop at low emissions to the environment The outstanding mechanical and chemical properties of polyester The recyclability The wide variety of intermediate and final products made of polyester.
POLYESTER – APPLICATIONS It can also be made into textile fibers known as Dacron and accounts for 50% of all fibers used to make clothing. Blended with cotton, made into no-iron clothes. Industrial polyester fibers, yarns and ropes are used in tyre reinforcements, fabrics for conveyor belts, safety belts, coated fabrics and plastic reinforcements Polyesters are also used to make bottles, films, tarpaulin, canoes, liquid crystal displays, holograms, filters, dielectric film for capacitors, film insulation for wire and insulating tapes
Nylon Matrices Nylon is a generic designation for a family of synthetic polymers known generically as polyamides Nylon is a thermoplastic, silky material, first used commercially in a nylon-bristled toothbrush. Nylon is made of repeating units linked by amide bonds and is frequently referred to as polyamide (PA)
NYLON Chemically, nylon is formed by chains of amide molecules. The chains are arranged parallel to each other, attached by hydrogen bonds. To make nylons fibers strong, a polymerizing process must occur that allows the molecules to combine without retaining any water. In effect the process of making nylon is a condensation reaction. Nylon 6,6
NYLON –CHEMISTRYNylons are condensation copolymers formed by reactingequal parts of a diamine and a dicarboxylic acid, so thatamides are formed at both ends of each monomer in aprocess analogous to polypeptide biopolymers A molecule of water is given off and the nylon is formed. Its properties are determined by the R and R groups in the monomers
NYLON - Characteristics Variation of luster: nylon has the ability to be very lustrous, semilustrous or dull. Durability: its high tenacity fibers are used for seatbelts, tire cords, ballistic cloth and other uses. High elongation Excellent abrasion resistance Highly resilient (nylon fabrics are heat-set) Paved the way for easy-care garments High resistance to insects, fungi, animals, as well as molds, mildew, rot and many chemicals Used in carpets and nylon stockings Melts instead of burning Used in many military applications Good specific strength Transparent to infrared light (−12dB)
NYLON –PROPERTIES Excellent material for machining Tough, strong, and impact resistant material Very low coefficient of friction Abrasion resistant. Excellent resistance (no attack) to Oils, Bases and THF Good resistance (no attack) to Solvents, Formaldehyde and Alcohols Limited resistance to Dilute Acids Poor resistance (not recommended for use with) Phenols, Alkalis, Iodine and Acids
NYLON – APPLICATIONS Nylon is commonly used in the production of tire cords, rope, belts, filter cloths, sports equipment and bristles. It is particularly useful when machined into bearings, gears, rollers and thread guides. Solid nylon is used for mechanical parts such as machine screws, gears and other low- to medium- stress components previously cast in metal.
NYLON – APPLICATIONS Engineering-grade nylon is processed by extrusion, casting, and injection molding. Solid nylon is used in hair combs. Type 6,6 Nylon 101 is the most common commercial grade of nylon, and Nylon 6 is the most common commercial grade of molded nylon
Polypropylene Polypropylene is a plastic polymer, of the chemical designation C3H6.
Polypropylene- Isotacti c Most commercial polypropylene is isotactic and has an intermediate level of crystallinity between that of low-density polyethylene (LDPE) and high- density polyethylene (HDPE)
Polypropylene-Types 1. Homopolymer 2. Copolymer 3.Block Copolymer PP is also used for plastics reinforced constructions. For this typical application, it is possible to use two different types of polypropylene. PP sk is the traditional type polyether-backed but as standard product, it exist also PP copolymer polypropylene-backed: PP-DWU-SK: Homopolymer, permanent-heat resistant, grey, polyester-backed PP-C-PK: Copolymer, permanent-heat resistant, grey, polypropylene- backed
Those PP-C-PK sheets have a lot of advantage: Allows excellent three-dimensional thermoforming It is not necessary to finish the fabric at welding zones Better adhesive properties than PP polyester backing sheets PP-EL is an electrically conductive homopolymer polypropylene. This material is treated with electrically conductive particles which discharge the static. PP-EL has high surface resistivity and is ideal for use in potentially explosive atmospheres. PP-EL-S (special type) includes a flame-retardant additive
Polypropylene-Manufacturing It is manufactured from the propylene gas in the presence of catalyst such as titanium chloride Melt processing of polypropylene can be achieved by extrusion and moulding Common extrusion methods A) Injection moulding B) Blow moulding C) Injection stretch moulding
Polypropylene-properties Semi-rigid Translucent Good chemical resistance Tough Good fatigue resistance Integral hinge property Good heat resistance
Polypropylene-Applications Since polypropylene is resistant to fatigue, most plastic living hinges, such as those on flip-top bottles, are made from this material Polypropylene lid of a Tic Tacs box, with a living hinge and the resin identification code under its flap
Polypropylene-Applications Polypropylene is used in the manufacturing piping systems; both ones concerned with high-purity and ones designed for strength and rigidity. Many plastic items for medical or laboratory use can be made from polypropylene because it can withstand the heat in an autoclave Its heat resistance also enables it to be used as the manufacturing material of consumer-grade kettles
Polypropylene – Applications Food containers made from it will not melt in the dishwasher, and do not melt during industrial hot filling processes. For this reason, most plastic tubs for dairy products are polypropylene sealed with aluminum foil (both heat-resistant materials) Car batteries, wastebaskets, pharmacy prescription bottles, cooler containers, dishes are often made of polypropylene
Polypropylene Polypropylene, highly colorfast, is widely used in manufacturing carpets, rugs and mats to be used at home. Polypropylene is widely used in ropes, distinctive because they are light enough to float in water Polypropylene is also used as an alternative to polyvinyl chloride (PVC) as insulation for electrical cables for LSZH cable in low-ventilation environments, primarily tunnels. This is because it emits less smoke and no toxic halogens, which may lead to production of acid in high- temperature conditions.
Polypropylene-Polyester For equal mass and construction, polypropylene rope is similar in strength to polyester rope. Polypropylene costs less than most other synthetic fibers.
Polypropylene- Applications Used for plastic moldings, wherein it is injected into a mold while molten, forming complex shapes at relatively low cost and high volume; examples include bottle tops, bottles, and fittings. It can also be produced in sheet form, widely used for the production of stationery folders, packaging, and storage boxes. The wide color range, durability, low cost, and resistance to dirt make it ideal as a protective cover for papers and other materials.
Polypropylene Polypropylene is a major polymer used in nonwovens, with over 50% usedfor diapers or sanitary products where it is treated to absorb water (hydrophilic) rather than naturally repelling water (hydrophobic). polypropylene yarn is the lightest fibre of all synthetic and natural fibers. Final users gain more comfort because the garments are lighter.