160 Chapter Two Thermosets, Reinforced Plastics, and Composites Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Thermosets, Reinforced Plastics, and Composites 161 catalyst pigment, and lubricants. The compounds are free-flowing granular in form and are available in opaque colors (mostly red). They are readily moldable in compression, trans- fer, and injection molding processes. 2.7.7.3 Reinforcements. The reinforcements available are quartz, “E”-type glass fi- bers, and fused silica. 2.7.7.4 Specifications Military (MII-M-14) MSG: Mineral filler, heat resistant MSI-30: Glass filler, impact value of 3.0 ft-lb, heat resistant UL. The UL ratings are (1) thermal index rating of 464°F (240°C) and(2) flammability rating of 94 VO in 1/16-in sections. 2.7.7.5 Data sheet values. Table 2.30 provides a property value list for the silicone family of molding compounds. 2.7.7.6 Applications. The silicones are nonconductors of either heat or electricity; have good resistance to oxidation, ozone, and ultra-violet radiation (weatherability); and are generally inert. They have a constant property profile of tensile, modulus, and viscosity values over a broad temperature range 60 to 390°F (13 to 166°C). They also have a low glass transition temperature (T g ) of –185°F. Encapsulation of semiconductor devices such as microcircuits, capacitors, and resistors, electrical connectors seals, gaskets, O-rings, and terminal and plug covers all take advantage of these excellent properties. 2.7.7.7 Suppliers Dow Corning Corporation Cytec Fiberite General Electric Company Silicone Products Division (See App. C for supplier addresses.) 2.7.8 Composites 2.7.8.1 History. 15 The introduction of fiberglass-reinforced structural applications in l949 brought a new plastics application field which began with the consumption of 10 lb and burgeoned into the annual usage of over 1 to 2 billion lb over the next several de- cades. This usage has been, and still is, taking place in application areas that take advan- tage of the extraordinarily low-weight/high-strength ratio inherent in these composite materials. Thermosets, Reinforced Plastics, and Composites Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. 162 Chapter Two A thermosetting matrix is defined as a composite matrix capable of curing at some tem- perature 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 that causes the matrix to poly- merize (cure) at room temperature, or a resinous matrix and curing agent that, when sub- jected to elevated temperatures, will commence to polymerize and cure. 2.7.8.2 Resins (matrices). The available resins are polyester and vinyl esters, poly- ureas, epoxy, bismaleimides, polyimides, cyanate ester, and phenyl triazine. Polyester and vinyl esters. Polyester matrices have had the longest period of use, with wide application in many large structural applications (see Table 2.31). They will Thermosets, Reinforced Plastics, and Composites Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. 163 Thermosets, Reinforced Plastics, and Composites Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. 164 Chapter Two cure at room temperature with a catalyst (peroxide), which produces an exothermic reac- tion. The resultant polymer is nonpolar and very water resistant, making it an excellent choice in the marine construction field. The isopolyester resins, regarded as the most wa- ter-resistant polymers in the polymer group, have been chosen as the prime matrix materi- als for use on a fleet of U.S. Navy mine hunters. Epoxy. The most widely used matrices for advanced composites are the epoxy resins, even though they are more costly and do not have the high-temperature capability of the bismaleimides or polyimide. The advantages listed in Table 2.32 show why they are widely used. Bismaleimides (BMIs). The bismaleimide resins have found their niche in high-tem- perature aircraft design applications where temperature requirements are in the 177°C (350°F) range. BMI is the primary product and is based on the reaction product from me- thylene dianiline (MDA) and maleic anhydride: bis (4 maleimidophynyl) methane (MDA BMI). 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 (Table 2.33). Polyimides. Polyimides are the highest-temperature polymers in the general advanced composite, with a long-term upper temperature limit of 232 to 316°C (450 to 600°F). Ta- ble 2.34 is a list of commercial polyimides being used in structural composites. Polyureas. Polyureas involve the combination of novel MDI polymers and either amine or imino-functional polyether polyols. The resin systems can be reinforced with milled glass fibers, flaked glass, Wollastanite, or treated mica, depending on the compound requirements as too processability or final product. Thermosets, Reinforced Plastics, and Composites Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Thermosets, Reinforced Plastics, and Composites 165 Thermosets, Reinforced Plastics, and Composites Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. 166 Chapter Two Cyanate ester and phenolic triazine (PT). The cyanate ester resins have shown supe- rior dielectric properties and much lower moisture absorption than any other structural resin for composites. The physical properties of cyanate ester resins are compared to those of a representative BMI resin in Table 2.33. The PT resins also possess superior elevated- temperature properties, along with excellent properties at cryogenic temperatures. They are available in several viscosities, ranging from a viscous liquid to powder, which facili- tates their use in applications that use liquid resins such as filament winding and transfer molding. 2.7.8.3 Reinforcements Fiberglass. Fiberglass possesses high tensile strength and strain to failure, but the real benefits of its use relate to its heat and fire resistance, chemical resistance, moisture resis- tance, and very good thermal and electrical values. Some important properties of glass fi- bers are shown in Table 2.35. Graphite. Graphite fibers have the widest variety of strength and moduli and also the greatest number of suppliers. These fibers start out as organic fiber, rayon, polyacryloni- trile, or pitch called the precursor. The precursor is stretched, oxidized, carbonized, and graphitized. The relative amount of exposure to temperatures from 2500 to 3000°C will then determine the graphitization level of the fiber. A higher degree of graphitization will usually result in a stiffer (higher modulus) fiber with greater electrical and thermal con- ductivities. Some important properties of carbon and graphite fibers are shown in Table 2.36. Aramid. The organic fiber kevlar 49, an aramid, essentially revolutionized pressure vessel technology because of its great tensile strength and consistency coupled with low density, resulting in much more weight-effective designs for rocket motors. Boron. Boron fibers, the first fibers to be used in production aircraft, are produced as individual monofilaments upon a tungsten or carbon substrate by pyrolytic reduction of boron trichloride (BCL) in a sealed glass chamber. Some important properties of boron fi- bers are shown in Table 2.37. 2.7.9 Molding Compound Production 16 2.7.9.1 Introduction. The selection of production equipment and processes for ther- mosetting molding compounds commences with the compound designer’s formulation, which designates the type and quantity of the various ingredients that make up the com- pound. These molding compounds are a physical mixture of resin, reinforcement or filler, catalyst, lubricant, and color. The resin, by far, is the key component in any thermosetting molding compound, since it is the only component that actually goes through the chemical reaction known as polymerization or cure during the molding process. Also, because of this curing quality, the resin, production process, and equipment are governed by the need to understand this chemical reaction with its effects on the production process and/or equipment. Also, the resin is the primary flow promoter and chief provider of the desired electrical insulating properties of the final molded product. The next most important component is the reinforcement or filler, because the type and quantity of either will determine the manufacturing process and equipment. This will be seen in the following sections, which describe the various processes and their equipment. Thermosets, Reinforced Plastics, and Composites Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. 167 Thermosets, Reinforced Plastics, and Composites Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. 168 Chapter Two Thermosets, Reinforced Plastics, and Composites Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Thermosets, Reinforced Plastics, and Composites 169 The compounds utilizing “fillers” as opposed to “reinforcements” can be processed with either the “dry” or the “wet” (solvent) process, since the compound formulations include free-flowing granular fillers that are not as susceptible to degradation when exposed to the hot roll mill phase of the operation. The catalyst in each compound serves as the reaction controller, with the type and quantity of catalyst acting to either accelerate or inhibit the curing rate in both the production and the molding phases. Lubricants, which provide a measure of flow promotion, mold release, and barrel life during molding, are generally internally supplied but are occasionally provided as an ex- ternal addition. All thermosetting molding compound colors are opaque, with the pig- ments or dyes heat stable within the molding process temperature range of 200 to 400°. Coloring does have a large effect on the manufacturing process when the product line in- cludes a wide variety of colors such as are common to the DAP, melamine, urea, and ther- moset polyester compounds. Choice of production equipment has to be designed to meet the need for quick and easy color changes. 2.7.9.2 Production processes Dry process (batch and blend). The dry or nonsolvent process, illustrated in Fig. 2.15, employs low-strength, low-cost, free-flowing granular fillers and involves the use of ribbon or conical mixers to homogenize the dry ingredients prior to feeding the mix onto the heated roll mills where the mix is compounded (worked) for a specific time and tem- perature. Once the mix or hatch has been worked to the proper consistency and tempera- ture, it is then fed onto a three-roll calendering mill where it is shaped to a specific width and thickness to allow the sheet to pass into a grinder, and then onto screens to obtain the desired granulation and for dust removal. The thickness and temperature of the calendered sheet is controlled for ease of granulation. If the sheet is too warm, it will not cut cleanly; if the sheet is too cool, it will be too fragile to produce clean, even size particles. An individual batch is generally 200 lb, which eventually is blended with other hatches into 2500- to 5000-lb blends that are ready for shipment to the customer. The batch and Figure 2.15 Batch and blend dry production method. Thermosets, Reinforced Plastics, and Composites Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. [...]... Reinhold Publishing, New York, 19 65 12.Charles A Harper, Chap 2 in Handbook of Plastics, Elastomers, and Composites, McGraw Hill, New York, 1996 13.Harry Raech, Jr., Chap 1 in Allylic Resins and Monomers, Reinhold Publishing, New York, 19 65 14.Harry Dubois, Plastics History USA, Cahners, Boston, 1972 15. Charles A Harper, Chap 3 in Handbook of Plastics, Elastomers, and Composites, McGraw-Hill, New York,... Plastics Handbook, Modern Plastics Magazine, McGraw-Hill, New York, 1994 8 H R Gillis, Plastics Handbook, Modern Plastics Magazine, McGraw-Hill, New York, l994 9 R Bruce Frye, Plastics Handbook, Modern Plastics Magazine, McGraw-Hill, New York, 1994 10.Charles A Harper, Chap 4 in Handbook of Plastics, Elastomers, and Composites, McGraw-Hill, New York, 1996 11.Harry Raech, Jr., Chap 1 in Allylic Resins and. .. Any use is subject to the Terms of Use as given at the website Source: Handbook of Plastics, Elastomers, and Composites Chapter 3 Elastomeric Materials and Processes* James M Margolis Montreal, Province of Quebec, Canada 3.1 Introduction Another important group of polymers is the group that is elastic or rubberlike, known as elastomers This chapter discusses this group of materials, including TPEs,... Companies All rights reserved Any use is subject to the Terms of Use as given at the website Thermosets, Reinforced Plastics, and Composites Thermosets, Reinforced Plastics, and Composites 177 Particle size analyzer (PSA) A particle size analyzer is an accurate and automatic development tool that allows for a very rapid measurement of particle size distribution in powder or slurry compounds Humidity... Terms of Use as given at the website Thermosets, Reinforced Plastics, and Composites Thermosets, Reinforced Plastics, and Composites 181 Figure 2.26 Orifice flow test and mold (II) from the center of the mold The runner configuration is 1 /8-in half-round, 100 in long The mold is heated to 300°F and run @ 300 lb/in2 The runner is marked in linear inches, and the test results are recorded as a flow of x... Companies All rights reserved Any use is subject to the Terms of Use as given at the website Thermosets, Reinforced Plastics, and Composites 188 Chapter Two 16.R E Wright, Chap 1 in Molded Thermosets, Hanser Verlag, Munich, 1991 17.Charles A Harper, Chap 1 in Handbook of Plastics, Elastomers, and Composites, McGraw-Hill, New York 1996 18.Bruce Fitts and David Daniels, Applications Report, Rogers Corporation,... the Terms of Use as given at the website Thermosets, Reinforced Plastics, and Composites Thermosets, Reinforced Plastics, and Composites 187 Postcure cycles1 Phenolics One-step resole compounds: At 1/8 in or less thick—2 hr @ 280°F (138°C), 4 hr @ 330°F (166°C), and 4 hr @ 3 75 F (191°C) Two-step novolac compounds: At 1 in or less thick—2 hr @ 300°F (149°C), 4 hr @ 350 °F (177°C, and 4 hr @ 3 75 F (191°C)... heavy-duty bags and sacks; and molded storage containers and lids.14 Engage®§ polyolefin elastomers (POEs), ethylene octene copolymer elastomers, produced by DuPont Dow Elastomers, use Insite catalytic technology .5 Table 3.2 shows their low density and wide range of physical/mechanical properties (using ASTM test methods) .5 The copolymer retains toughness and flexibility down to 40°F (–40°C) .5 When crosslinked... measurable and controllable, and the compound producer can, and often will, supply the molder with test data on each production blend the customer has received The special characteristics of each of these ingredients are as follows: Resin Viscosity, gel time, cure rate, and solubility Reinforcements and fillers Aspect ratio, moisture content, fiber size and length, purity, and color Pigments and dyes Solubility,... being covered on both lower and upper surfaces with a thin film of polyethylene The finished product is then conveyed onto a rotating mandrel and wound up until it reaches a preset weight, and then it is cut off The sheets ready for use or for shipment generally weigh about 50 lb, are 4 ft wide, and are approximately 0.0 75 to 0. 250 in thick Formulations generally consist of an unsaturated polyester resin . reserved. Any use is subject to the Terms of Use as given at the website. Thermosets, Reinforced Plastics, and Composites 1 65 Thermosets, Reinforced Plastics, and Composites Downloaded from Digital. designs, part configuration, number of cavities and their location in the mold, and size and location of the runner and gate system. Figure 2.21 Typical thermosetting curve. Thermosets, Reinforced Plastics,. subject to the Terms of Use as given at the website. Thermosets, Reinforced Plastics, and Composites 177 Particle size analyzer (PSA). A particle size analyzer is an accurate and automatic development