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Understanding Thermoset Plastic Materials

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1 Understanding Thermoset Plastic Materials
Prepared by the IAPD Education Committee (Module 6) Presented courtesy of Modern Plastics Inc. The IAPD Plastics Primer, Module 6

2 Thermosets Resin Thermoset vs. thermoplastic
One definition of resin is “any class of solid, semi-solid, or liquid organic material, generally the product of natural or synthetic origin with a high molecular weight and with no melting point.” The ten basic thermosetting resins all possess a commonality in that they will, upon exposure to elevated temperature from ambient to upwards of 232°C/450°F, undergo an irreversible chemical reaction often referred to as polymerization or cure. Each family member has its own set of individual chemical characteristics based upon their molecular makeup and their ability to either homopolymerize, copolymerize, or both. This transformation process represents the line of demarcation separating the thermosets from the thermoplastic polymers. Crystalline thermoplastic polymers are capable of a degree of crystalline cross-linking but there is little, if any, of the chemical cross-linking that occurs during the thermosetting reaction. The important beneficial factor here lies in the inherent enhancement of thermoset resins in their physical, electrical, thermal, and chemical properties due to that chemical cross-linking polymerization reaction which, in turn, also contributes to their ability to maintain and retain these enhanced properties when exposed to severe environmental conditions. A thermoset plastic is a polymeric material that can be formed by application of heat and pressure, but can not be reformed upon further applications of heat and pressure. A thermoset is like a cooked egg and can not be re-melted and reshaped into another solid shape. In comparison, a thermoplastic can be compared to wax and ice — those materials can be hardened and formed into other shapes. The IAPD Plastics Primer, Module 6

3 Thermosets Types Laminates Composites Polyurethanes
We will cover three primary plastic materials in the thermoset family of products: laminates, composites and polyurethanes. The IAPD Plastics Primer, Module 6

4 Thermoset Laminates Phenolics Epoxies Melamines Silicones Polyesters
Composites The resin systems primarily used for laminates are bismaleimides, epoxies, melamines, polyesters, polyimides, silicones, and phenolics and cyanate esters. Thermosetting resin systems are the backbone of a large, versatile and important family of molding compounds which provides the industrial, military, and commercial markets with plastic molding materials exhibiting exceptional electrical, mechanical, thermal, and chemical properties. These important property values enable the product designer, manufacturing engineer, and research and design engineer to select from a wide choice of products, and enable them to choose the most suitable molding compound to meet their specific needs and requirements. These versatile materials are covered by military, industrial, and commercial specifications that are designed to ensure the quality of the molded articles utilizing thermosetting molding compounding. Most of these resins are used in laminated form with a number of sandwich-like mediums. This medium can be paper, wood, cotton, linen or other materials. We’ll go through each of these resins individually. The IAPD Plastics Primer, Module 6

5 Laminates Key Characteristics
Corrosion resistant Good insulating characteristics at low temperatures Good machinability Thermoset plastic industrial laminates are uniformly dense and structurally strong materials that will not soften appreciably under the reapplication of heat. Industrial laminates are available in sheet, rod, tube and profile. Since these laminates are comprised of a combination of materials, they are also referred to as composites. Thermoset engineering plastics replace metals, ceramics, woods and engineering thermoplastics in many applications. Some examples of thermoset materials are phenolics, epoxies and melamines. The IAPD Plastics Primer, Module 6

6 Laminates Process Resin Binder Reinforcing Substrate
Laminates can be defined as combinations of liquid thermosetting resins with reinforcing materials that are bonded together by the application of heat and pressure, forming an infusible matrix. Plywood is a good example of a thermosetting laminate with the phenolic resin serving as the binder to bond the layers of wood sheets together when compressed with heat in a molding press. Glass fibers are the most commonly used laminate reinforcement and are available in some six formulations with the E glass providing excellent ties along with other valuable properties. Many different fabrics are made for reinforced plastics, E glass being the most common. Filament laminates using glass types of D, G, H, and K are also common with the filaments combined into strands, and the strands plied into yarns. These yarns can be woven into fabrics on looms. Heat and pressure applied to the top and bottom of the material. The IAPD Plastics Primer, Module 6

7 Laminates Types Paper based Cotton based Glass based
Synthetic fabric based Paper based grades are made almost exclusively with phenolic resins. They are light in weight, easy to machine, good electrical insulators and are resistant to chemical corrosion. These grades are the least expensive laminates and are excellent for a wide variety of electrical and not-too-demanding mechanical applications. Cotton based grades are available with phenolic or melamine resins. These exhibit good electrical properties, good mechanical strength, are easy to machine and are resistant to chemical corrosion. These materials can withstand a great deal of abuse. Grade designations are C, CE, CYB, L, LE, LYB and LM. The L indicates a finer fabric than the C, the E indicates a material more suited for electrical applications, and the M indicates the uses of melamine resin. The Y designates the addition of graphite powder to the resin to give you lower coefficient of friction characteristics for bearing applications. Glass based laminates are the most universally used today. Phenolic, melamine, epoxy, silicones and polyester resins are all used with glass fabric to produce a wide variety of grades. All glass grades are excellent in electrical, mechanical and thermal properties. The major differences are in price, heat resistance, flammability and track resistance. Synthetic nylon phenolic laminates are produced in limited quantities but remain available. They exhibit good electrical properties and have very high impact strength. Because the base material is nylon, the material is more subject to creep than any other laminate material. It designation is N-1. The IAPD Plastics Primer, Module 6

8 Phenolic Laminates Strengths
High degree of resistance to deforming under load Can withstand 149°C/300°F continuously One of the hardest plastics available Cross-linked phenolics are very resistant to compressive loads Phenolic resins came into being when Dr. Leo Baekeland, in the early 1900s, discovered that a successful reaction between phenol and formaldehyde in a heated pressure kettle produced an amber colored liquid thermosetting resin. This resin became the foundation of the entire thermosetting molding compound industry, and an entire family of thermosetting resins and compounds were developed over the next several decades. Phenolic molding compounds became the primary insulating material for a wide and diversified range of applications for industrial, commercial, and military applications. Today’s phenolic resins offer a versatile combination of heat and flame resistance, chemical resistance, electrical insulation and process adaptability at a high performance to price ratio. The IAPD Plastics Primer, Module 6

9 Phenolic Laminates Limitations
Brittleness Impact resistance Moisture resistance is limited Resins darken when exposed to heat and ultra violet light The IAPD Plastics Primer, Module 6

10 Phenolic Laminates Types
Paper based Grades X, XX, XXX, XP, XXP, XXXP, XPC, XXPC and XXXPC Cotton based Grades C, CE, CYB, L, LE, LYB, LM The two basic types of phenolic resins, novolacs and resoles, are produced by chemically combining phenols and aldehydes with a catalyst. Novolacs, or two-stage resins, are produced with an acid catalyst and are initially thermoplastic. Resoles, or single-stage resins, are catalyzed by basic compounds and are self-curing. The paper grade designations are X, XX, XXX, XP, XXP, XXXP, XPC, XXPC, and XXXPC. More X’s in the designation indicate better electrical properties, the P indicates materials that are suitable for punching, and the C indicates materials that can be punched without preheating. The IAPD Plastics Primer, Module 6

11 Phenolic Laminates Applications
Wiring devices Switch gear Circuit breakers Insulators Gears Wear guides Pulleys Rollers Phenolic resin has inherent resistance to fire, UV-radiation, moisture and thermal cycling. When subjected to fire, phenolics simply char and emit minimal volatile organic compounds making phenolic composites a cost effective alternative for use in construction and mass transportation. The high cross-link density of cured phenolic molding materials provides rigidity, minimizes creep, and retains physical properties at elevated temperatures extremely well at low cost. This makes phenolics ideal for applications where physical properties and structural integrity must be maintained, at elevated temperatures, under working loads. Such applications include automotive transmission spacers and brake pads, kitchen range temperature controls, and rocket nozzles and heat shields. The IAPD Plastics Primer, Module 6

12 Epoxy Laminates Strengths
Offer virtually no water absorption Good insulating and electrical properties Excellent dimensional stability Good temperature and chemical resistance Epoxy resins have been true workhorses of industry since they were commercially introduced in the U.S. in These materials have broad usage in: laminates and encapsulants for electrical/electronics applications, fiber-reinforced vessels, pipes and structural materials, construction applications in flooring and paving, tooling, high-performance protective coatings, and adhesives and bonding. In their cured (cross-linked) form, epoxy resins offer excellent chemical and corrosion resistance, outstanding adhesion, good mechanical properties, low shrinkage, flexibility in formulating for a broad array of desired end use properties, excellent electrical properties, and the ability to be processed under a wide variety of conditions. Glass cloth increases temperature resistance to the material. The IAPD Plastics Primer, Module 6

13 Epoxy Laminates Limitations
Brittle Poor UV resistance Poor weathering resistance The IAPD Plastics Primer, Module 6

14 Epoxy Laminates Types G-10 FR-4 G-11 FR-5
G-10 is a thermosetting industrial laminated plastic consisting of a woven glass cloth material and an epoxy resin matrix. First introduced in the 1950s, G-10 was the original glass epoxy laminate used in printed circuitry. Today most of what is called G -10 is actually FR-4, the flame retardant version of G-10. FR-4 is also at times referred to as G-10FR. G-11 and FR-5 are thermosetting resins using woven glass-based material with a high temperature epoxy resin matrix. Again, as is above the FR-5 is the flame retardant grade of G-11. The FR-5 is UL-94V-0 rated. Please note that G-10 and FR-4 are not replacements for G-11 and FR-5 as these are much higher temperature rated. G-11 and FR-5 are rated at 182°C/360°F. The IAPD Plastics Primer, Module 6

15 Epoxy Laminates Applications
Electrical insulators Circuit board backing Construction Aviation/aerospace Epoxy laminates find use in the electrical/electronic area in computers, telecommunications, automotive, consumer, military and industrial applications. Heavy equipment and machinery uses include mechanical and electrical assemblies, wire windings for coils and motors, casting of switch gears and circuit breakers, and molding of small electronic parts. Adhesives and bonding are used in furniture and appliances, packaging laminates, and bonding electrical components in machinery. In aviation, epoxy film adhesives fuse component parts, or join dissimilar materials in cars and trucks. Construction uses include industrial, commercial, and decorative flooring, including pebbled floors in hotels, restaurants and private homes. Tooling uses epoxy resins to create accurate prototypes, develop experimental models, and also yield production efficiencies in limited-run manufacturing for aircraft, automotive, and industrial applications. High performance coatings are used for beverage can interiors, automotive coatings; maintenance and marine finishes, appliance, machinery and equipment coatings, and sheet and coal coatings. Composites make use of epoxy resins in high-performance applications in aviation and aerospace, sports equipment, fiberglass pipe and specialty automotive parts. The IAPD Plastics Primer, Module 6

16 Melamine Laminates Strengths
Made from melamine and formaldehyde resins Usually used as a laminate with cloth Easily produced in an unlimited range of colors Good electrical properties under humid conditions Excellent arc-tracking resistance Excellent compressive strength Good physical properties Very good solvent resistance Can withstand temperatures of 204°C/400°F Good chemical and weather resistance Strong mechanical properties Melamine and urea belong to the family of amino resins, of which they are the two most common examples. Like all amino resins, melamine is formed by the controlled reaction of formaldehyde with compounds that contain the amino group NH2. Melamine can be formulated into coatings, laminates, molding compounds, and adhesives. In neat versions or with the use of various fillers, the material offers varying degrees of hardness, strength, flame resistance, dimensional stability, high dielectric properties, and humidity, water and abrasion resistance. These are the many strengths of this laminate. For those strengths, there are just as many limitations. The IAPD Plastics Primer, Module 6

17 Melamine Laminates Limitations
Can be attacked by strong acids Brittleness Poor resistance to organic solvents Difficult to bond High cost The IAPD Plastics Primer, Module 6

18 Melamine Laminates Types
G-5 G-9 The key difference between these two grades of material is that G-9 is more resistant to the elements of the environment. G9 can be safely substituted where G5 is called for. The IAPD Plastics Primer, Module 6

19 Melamine Laminates Applications
Welding rod holders Heavy duty switch gears High temperature switches Electrical insulators Applications from molding compounds include toilet seats, closures, wiring devices (circuit breakers, wall plates, receptacles), buttons, housings, knobs, and handles. The IAPD Plastics Primer, Module 6

20 Silicone Laminates Strengths
Retain properties over a wide temperature range Remain flexible down to negative 16ºC/60ºF High degree of biocompatibility Silicones are semi organic, synthetic polymers. Their structure is composed of alternating silicon and oxygen atoms rather than the carbon-to-carbon backbone that characterizes organic polymers. Silicones, also known as polyorganosiloxanes, come in several forms: fluids, elastomers, gels, and resins. Plastics processing focuses primarily on elastomers, which find use in various markets: medical, automotive, electrical, industrial recreational, business machines, and construction. Silicone thermosetting resins are among the best of all polymer materials in resistance to temperature. Because of this, silicone is broadly used for high temperature electronic applications requiring low electrical losses. The IAPD Plastics Primer, Module 6

21 Silicone Laminates Limitations
Tensile strength low Abrasion resistance low Swell in oils, fuels and other solvents Some properties of silicone elastomers pale in comparison to other elastomers and plastics. Tensile strength is only 4.1 to 9.3 MPa, abrasion resistance is low, and they swell in oil, fuel, and many solvents. The IAPD Plastics Primer, Module 6

22 Silicone Laminates Type
G-7 (glass cloth reinforced silicone) G-7 is glass cloth reinforced silicone, with the natural color being typically cream to white. Composed of a continuous glass woven cloth base impregnated with a silicone resin binder, this grade has excellent heat and arc resistance. Silicon is not as strong as phenolics and epoxies upon aging at lower temperatures, but is stronger upon aging at higher temperatures over 204ºC/400ºF. The IAPD Plastics Primer, Module 6

23 Silicone Laminates Applications
Sealants Gaskets Medical The IAPD Plastics Primer, Module 6

24 Polyester Laminates Strengths
Low cost Good arc and track resistance Polyester laminates are composed of random fiberglass matt held together with a polyester resin binder. Polyesters are versatile resins which handle much like epoxies. It’s their physical application form that makes them similar. The IAPD Plastics Primer, Module 6

25 Polyester Laminates Limitations
Lower abrasion resistance Brittle Great change to electrical properties in humid environments Despite lower costs, the disadvantages of polyesters, as compared with epoxies, is lower adhesion to most substrates, higher polymerization shrinkage, a greater tendency to crack during cure or in thermal shock and greater change of electrical properties in a humid environment. The IAPD Plastics Primer, Module 6

26 Polyester Laminates Types
GPO-1 GPO-2 GPO-3 These grades are composed of random mat (non-woven) fiberglass reinforcement held together by a polyester resin binder. GPO-2 offers superior arc resistance over GPO-1 while GPO-3 offers both arc and track resistance. The IAPD Plastics Primer, Module 6

27 Polyester Laminates Applications
Structural profiles Sodering pallets The IAPD Plastics Primer, Module 6

28 Composites - Thermosetting Matrix
History Definition The introduction of fiberglass-reinforced structural applications in 1949 brought a new plastics application field. New composites are used in application areas that take advantage of the extraordinary low-weight-high-strength ratio inherent in these composite materials. A thermosetting matrix is defined as a composite matrix capable of curing at some temperature from ambient to several hundred degrees of elevated temperature and cannot be reshaped by subsequent reheating. In general, thermosetting polymers contain two or more ingredients — a resinous matrix with a curing agent which causes the matrix to polymerize (cure) at room temperature or a resinous matrix and curing agent that, when subjected to elevated temperatures, will commence to polymerize and cure. Due to the fact that most composites are custom blended and produced for specific applications we will not go into detail on the applications, properties, strengths or weaknesses of these materials. We did however feel it was necessary to give you this brief overview on these materials. The IAPD Plastics Primer, Module 6

29 Composites Materials Polyester and vinyl esters Epoxy
Bismaleimides (BMI) Polyimides Polyureas Cyanate ester and phenolic triazine (PT) Polyester matrices have had the longest period of use, with wide application in many large structural applications. They cure at room temperature with a catalyst (peroxide) which produces an exothermic reaction. The resultant polymer is non-polar and very water resistant making it an excellent choice in the marine construction field. The most widely used matrixes for advanced composites are the epoxy resins even though they are more costly and do not have the high-temperature capability of the BMIs or polyimide. The bismaleimide (BMI) resins have found their niche in the high-temperature aircraft design applications where temperature requirements are in the 177°C/350°F range. BMI is the primary product and is based upon the reaction product from methylene dianiline (MDA) and maleic anhydride. Variations of this polymer with compounded additives to improve impregnation are now on the market and can be used to impregnate suitable reinforcements to result in high temperature mechanical properties. Polyimides are the highest-temperature polymer in the general advanced polymer composite with a long-term upper temperature limit of °C/ °F. The cyanate ester resins have shown superior dielectric properties and much lower moisture absorption than any other structural resin for composites. The PT resins also possess superior elevated temperature properties, along with excellent properties at cryogenic temperatures. The IAPD Plastics Primer, Module 6

30 Polyurethane (PUR) Strengths
Good abrasion resistance Good toughness Very high tear resistance High load bearing ability High impact resistance Good elastomeric memory Life without polyurethanes is unthinkable. Polyurethanes are found everywhere: in the home, in the automobile, in the workplace, and where ever leisure and recreation activities are enjoyed. The polymer is integral to the performance of many products that people equate with modern living — from adhesives to athletic shoes to refrigerators. Polyurethanes (PUR) are one of the most versatile of polymers. They range from liquid adhesives, to gels, to flexible, semi-rigid, and rigid foams, to soft and hard solid elastomers. PUR can also be used in coatings, films or fibers. The history of PUR dates to 1937, when Dr. Otto Bayer invented the polyisocyanate polyaddition process, the basic principle for the manufacture of polyurethanes. Commercialization of the first PUR products began in the 1950s. The IAPD Plastics Primer, Module 6

31 Polyurethane Limitations
Hot water limitation 82°C/180°F Poor chemical resistance to strong acids, bases and certain solvents The IAPD Plastics Primer, Module 6

32 Polyurethane and the Environment
TDI MDI Processes Polyurethanes, with their versatility and unique properties of scuff resistance, flexibility, and exceptional chemical resistance, have become the choice of many formulators in designing products to meet demanding performance requirements. Passage of the Clean Air Act Amendments in 1990 limited exposure to many chemicals. The Environmental Protection Agency (EPA) and OSHA, in actively pursuing toluene diisocyanate (TDI) as a poison, have significantly affected the polyurethane industry. That TDI is a poison is always in the minds of formulators and developers. Formulators avoid TDI, a popular choice as the diisocyanate portion, owing to the inherent higher chemical reactivity of its aromatic polyisocyanates. Diisocyanates, such as MDI or aliphatic diisocyanates, are used as hopeful solutions. The IAPD Plastics Primer, Module 6

33 Polyurethane Hardness Chart
The IAPD Plastics Primer, Module 6

34 Polyurethane Applications
Automotive Building and construction Furniture and mattresses Insulation for refrigerators, shipping containers, tanks, pipes As versatile as PUR is, nearly 70 percent of annual worldwide consumption goes into just four markets: automotive, building and construction, furniture and mattresses, and insulation for refrigerators, shipping containers, tanks, and pipes. The two major markets are automotive and construction. The IAPD Plastics Primer, Module 6

35 Polyurethane Urethane Types
Polyether Polyester There are two types of polyurethane: polyether and polyester. We’ll go over each of these in more detail. The IAPD Plastics Primer, Module 6

36 Polyether Urethane Strengths
Better water resistance Better dynamic properties Better low temperature properties The IAPD Plastics Primer, Module 6

37 Polyether Urethane Limitations
Lower abrasion resistance than polyesters Stiffer material than polyesters More likely to tear The IAPD Plastics Primer, Module 6

38 Polyether Urethane Applications
Bushings Idler rollers Printing machine rolls Hydraulic seals Elevator wheels Paper mill rolls The IAPD Plastics Primer, Module 6

39 Polyester Urethane Strengths
Higher physical properties Generally softer than polyether Stronger cut and tear resistance Better oil and heat aging resistance Meets FDA requirements for wet food applications The IAPD Plastics Primer, Module 6

40 Polyester Urethane Limitations
Poor resistance to hydrolysis (moisture absorption) Less resilient than polyethers Poor low temperature performance The IAPD Plastics Primer, Module 6

41 Polyester Urethane Applications
Cutter bars on printing machines Wear pads Tumbler liners Squeegees Office equipment rollers The IAPD Plastics Primer, Module 6

42 Polyurethane's Product Range Comparisons to Other Materials
Urethane products come in a variety of hardness. These hardnesses are determined depending on the applications. The IAPD Plastics Primer, Module 6

43 The End The IAPD Plastics Primer, Module 6

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