Some fundamental and easily implemented work practices that can be used to minimize exposures when working with advanced composites are: Employee exposures also can be controlled by scheduling operations with the highest exposures at a time when the fewest employees are present. Additives   Ingredients mixed into resin to improve properties. Co-cured   Cured and simultaneously bonded to another prepared surface. More dust is usually generated in finishing and repair processes since large surface areas are involved. At present, both manual and automated processes are employed in making advanced-composite parts. ASM International, Metals Park, Ohio: 1987. To achieve proper cure, the part is placed into a plastic bag inside an autoclave (Figure III:1-9). Due to the solvents' defatting properties, repeated or prolonged skin contact with these liquids may cause dermatitis. Hazards of Isocyanates (TDI, MDI, HDI) In Resins, Coatings and Paints. The National Institute for Occupational Safety and Health (NIOSH) Section Navigation. This means that, in many cases, glove and clothing selection must be a trial and error process. Permeation data are available for many industrial chemicals, especially solvents. Impact strength   A material's ability to withstand shock loading as measured by the work done in fracturing a specimen. This process is often fully automated. Summary of Health Effects Phenol may cause irritation and burns by any route of exposure. Stress   The internal force that resists change in size or shape, expressed in force per unit area. The potential synergism has not been clearly defined. Again, the choice of curing agent depends on the cure and performance characteristics desired for the finished part. Phenol formaldehyde resins are an impeccable alternative for resorcinol. A-basis allowable: material property exceeds the design allowable 99 times out of 100. As automated processes become more predominant, the costs of advanced composites are expected to decline to the point at which these materials will be used widely in electronic, machinery, and surface transportation equipment. Solvents in the workplace may be found in several areas: A brief description of each process is given, followed by a basic diagram. Pressure-bag molding   A molding technique in which a flexible bag is placed over the contact layup in the mold, sealed, and clamped in place, and pressure applied by compressed air, which forces the bag against the part while the part cures. The Department of Labor does not endorse, takes no responsibility for, and exercises no control over the linked organization or its views, or contents, nor does it vouch for the accuracy or accessibility of the information contained on the destination server. Isolation (e.g., isolated storage, separate process areas, enclosures, closed systems) and local exhaust ventilation are the primary engineering controls found in advanced composites processes. However, respirators may be required where: Dust levels are high (resin mixing, finishing, repair); Large surface areas and significant hand work are involved; and. Likewise, machining these phenolics often creates a huge amount of abrasive … Pot life   The length of time a catalyzed thermosetting resin system retains a viscosity low enough for it to be suitable for processing. Contact molding   A technique in which reinforcement and resin are placed in a mold, with cure taking place at room temperature with a catalyst/promoter system, or in a heated oven. Acute exposure to high concentrations of benzene vapour can result in central nervous system depression (eg impaired thinking, blurred vision), arrhythmias as well as irritation of the skin, eyes and respiratory system. This page requires that javascript be enabled for some elements to function correctly. Still another may be used for cleanup. Wet layup   The application of resin to dry reinforcement in the mold. The skin staining has been attributed to MDA; dermal absorption is approximately 2% per hour. Typically, a synthetic blasting agent, e.g., plastic media blast, is used. It is used in organic metal-matrix composites. Wetting agent   A surface-active agent that promotes wetting by decreasing the cohesion within a liquid. Shelf life   The length of time a material can be stored and continue to meet specification requirements and remain suitable for its intended use. Vacuum Bagging and Autoclave. Polyurethanes are another group of resins used in advanced composite processes. Carbon/graphite fibers dominate the advanced composites industry and may be made from any of three precursors, as discussed in Section C. However, the PAN-based carbon fibers are the predominant form in use today. Thermosets are by far the predominant type in use today. Glass-transition temperature (Tg)   The approximate temperature at which increased molecular mobility results in significant changes in properties of a cured resin. Autoclave molding   A molding technique in which an entire assembly (layup) is placed into an autoclave at 50 to 100 psi, in order to consolidate layers of the part by removing entrapped air and volatiles. Dry winding   A type of filament winding in which preimpregnated roving is used. Several of the solvent classes most commonly found in the PMC workplace are listed below, along with general hazard information. This large industry utilizes various resin systems including polyester, epoxy, and other specialty resins. For problems with accessibility in using figures and illustrations in this document, please contact the Office of Science and Technology Assessment at (202) 693-2095. The sizing materials are typically epoxy resins. Warp   The yarns running lengthwise and parallel to the selvage in a woven fabric. Previous article in issue; Next article in issue; Keywords. The form around which resin-impregnated fiber or tape is wound to form structural shapes or tubes. Polyacrylonitrile (PAN)   A product used as a base material in the manufacture of certain carbon fibers. Sizing   A compound that binds together and stiffens warp yarn to provide resistance to abrasion during weaving; normally removed and replaced with finish before matrix application. The process produces more complex shapes and permits a faster putdown rate than filament winding. E-glass   "Electrical glass"; the borosilicate glass most often used for the glass fibers in conventional reinforced plastics. Synonyms & Trade Names Carbolic acid, Hydroxybenzene, Monohydroxybenzene, Phenyl alcohol, Phenyl hydroxide CAS No. Fatigue   The failure of a material's mechanical properties as a result of repeated stress. Skin rashes are common and reportedly more severe than from glass fibers. Technical literature including MSDS's from the solvent supplier should be consulted about these or any chemicals used with advanced composites. Phenolic resins are a group of the most versatile polymers yet invented. Symptoms may include irritation, redness, scratching of the cornea, and tearing. Fabric, nonwoven   A material formed from fibers or yarns without interlacing. This chapter deals with a segment of the polymer composite industry known as advanced polymer matrix composites, or advanced composites. | 2 / 13 SAFETY DATA SHEET Resin BASIC 2.2. Like the epoxies, these compounds have a very low vapor pressure and usually do not present an airborne hazard unless in a mixture that is sprayed or cured at high temperatures. Res., vol. Tape laying   A fabrication process in which prepreg tape is laid side by side or overlapped to form a structure. Washington, DC 20210 Related Pages. Unlike the thermosets, the thermoplastics can usually be reheated and reformed into another shape, if desired. Typically, heat and pressure are used to shape and "cure" the mixture into a finished part. In high concentrations, narcosis is produced with symptoms of headache, nausea, light-headedness, vomiting, dizziness, incoordination, and unconsciousness. Water jet   A high-pressure stream of water used for cutting organic composites. Many of the materials, particularly the resins, curing agents, and fibers, present a potential dermal-exposure hazard. Lap joint   A joint made by bonding overlapped portions of two adherends. Polymer-matrix composites manufacturing is a multibillion dollar industry in the U.S. and one of the few in which the U.S. is conceded to be slightly more advanced than competitors abroad. The continuous cured part, usually a rod or similar shape, is then cut to the desired length (Figure III:1-7). Also called resole. Practically all glass fibers for composite reinforcement are greater than six microns in diameter. Washington, DC 20210 Release film   An impermeable film layer that does not bond to the composite during cure. 1: Composites. These include aliphatic and cycloaliphatic amines, polyaminoamides, amides, and anhydrides. Many manufacturers have replaced the ketones with the above hydrocarbon solvents to reduce the risk of flammability. It is made with stronger yarns in a tighter construction than the body of the fabric to prevent raveling. Release agents   Materials that are used to prevent cured matrix material from bonding to tooling. Damping   Diminishing the intensity of vibrations. Breather   A loosely woven material that does not come in contact with the resin but serves as a continuous vacuum path over a part in production. Wrinkle   An imperfection in the surface of a laminate that looks like a crease or fold in one of the outer layers; it occurs in vacuum bag molding due to improper placement of the bag. Do not weld, flame cut metal or use naked flames in vicinity or products. The basic epoxy compounds most commonly used in industry are the reaction product of epichlorohydrin and bisphenol-A. The retina of the eye might be damaged not only by direct contact but also from MDA absorbed through ingestion. in process equipment containers (tanks, reactors, molds, etc.). Heat-distortion temperature   Temperature at which a test bar deflects a certain amount under specified temperature and a stated load. However, due to the same properties epoxy products are a notorious cause of allergic skin disease among workers. The principal hazards of carbon-fiber handling are mechanical irritation and abrasion similar to that of glass fibers. Van Nostrand Reinhold Co., New York: 1982. These and the other processes are discussed in more detail in. Fiber placement   A continuous process for fabricating composite shapes with complex contours and/or cutouts by means of a device that lays preimpregnated fibers (in tow form) onto a nonuniform mandrel or tool. The supplier's Material Safety Data Sheet (MSDS) should be consulted for more specific hazard information. Critical length   The minimum length of a fiber necessary for matrix shear loading to develop fiber ultimate strength by a matrix. The evidence from human and animal studies was evaluated by IARC as insufficient to classify continuous-filament glass fibers a possible, probable, or confirmed cancer-causing material. Automated tape application machine ( robot ) appears to be suitable for its intended use very for! An orderly, three-dimensional pattern the materials involved Safety data SHEET resin basic 2.2 effects from industrial exposures come from. 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