Processing Chapter 3 Introduction Introduction Introduction Thermoset Definition:
Laporte, Leo, Executive Producer/Host has reference to this Academic Journal, PHwiki organized this Journal Processing Chapter 3 Compression Molding Introduction In 1907 Dr. Leo Baekel in addition to achieved a reaction between Phenol, a caustic, crystalline acidic compound in addition to Formaldehyde, a colorless, pungent gas, by heating these ingredients under pressure in a reaction kettle. The resultant, hot liquid when cooled, became a hard brittle solid. It lacked physical strength, but possessed excellent thermal, chemical in addition to electrical insulating properties Introduction The hard brittle resin in a pulverized from could be mixed with fillers, rein as long as cement, colorants, lubricants in addition to catalyst. The end product was a molding compound capable of further processing on heated mills in addition to calendar mills. Thus the first thermosetting molding compound was created.
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Introduction In the following years additional thermoset resin systems were developed to meet the requirements of diverse applications in automotive, communications, construction, transportation, household appliances, business machines, aircraft in addition to aerospace fields. Thermoset Definition: A polymeric material which can be as long as med by the application of heat in addition to pressure, but as a result of chemical reaction permanently crosslinks in addition to cannot be re as long as med upon further application of heat Chemical crosslinking must occur as long as the resultant product to be called a thermoset. Monomeric precursors may or may not be polymeric Thermoset Families Allyls Aminos Epoxies Phenolics Polyesters Polyurethanes Silicones Crossed linked thermoplastics
Classifications General Purpose Average mechanical properties, lower resistance to heat, higher coefficient of expansion, low cost in addition to commodity production.(Phenolics, Aminos in addition to polyesters) Engineering Higher mechanical properties in addition to temperature resistance in addition to more durable. More expensive with moderate production rates. (Epoxies in addition to Polyurethanes) Classifications Specialty one or more highly specific in addition to unusual properties. Very expensive in addition to produced in small quantities. (Silicones, Allyls, Crossedlinked Thermoplastics) General Properties Thermal in addition to dimensional stability Electrical insulation Chemical resistance High flexural modulus Toughness Surface hardness Moldablilty Cost effectiveness
Phenolics Introduction First thermosetting plastic, first synthetic commercially available plastic resin Produced by chemical reaction between phenol (resin) in addition to as long as maldehyde (curing agent) First made by Dr. Leo Baekel in addition to in 1907 By far the most widely used of all thermosets as long as molding applications Chemistry Phenol Formaldehyde resins are general purpose thermosets as long as med mainly by the polycondensation reaction between phenol in addition to as long as maldehyde Resole process, other main process is Novalac Raw Materials Phenol Show phenol structure Formaldehyde Show as long as maldehyde structure
Phenol Cumene process as long as making phenol Formaldehyde Formaldehyde is produced by the controlled catalytic oxidation of methanol Phenolic Reaction Phenolic resin reaction process
Phenolic curing process The curing process to the final thermoset material can be initiated by just heating the resin in a mold above its gel temperature When heated, the resin as long as ms larger molecules without the use of additional catalyst The reaction is a typical polycondensation, since water is given off as a by product Phenolic curing process Processes that use Phenolics Compression Molding Transfer molding Injection Molding
Properties of Phenolics Physical Excellent dimensional stability Low water absorption High surface hardness High creep resistance Mechanical High compressive strength High modulus, stiffness Properties of Phenolics Thermal Phenolics retain a high percentage of properties at elevated temperatures Low coefficient of thermal expansion Good heat resistance Properties of Phenolics Electrical Good electrical resistance Chemical Good chemical resistance Other Good weather resistance Easily molded Good machining properties
Applications as long as Phenolics Appliances 17% Closures 7% Electrical 38% Housewares 23% Industrial 4% Transportation 11% Molding in addition to Molding Techniques Introduction There are three fundamental molding processes as long as thermoset compounds. Compression molding Transfer molding Injection molding The process used will be determined by which process can produce the part to appropriate specifications at the most economical rate
Production Methods in addition to Equipment The choice of methods in addition to equipment as long as use in the production of thermosetting molding compounds is usually determined by the type of rein as long as cement being used Rein as long as cements are added to thermosets to improve properties. Impact, flexural strengths, shrinkage, etc. Compression Molding Introduction Uses a hydraulically operated press Press consists of two heated mold platens, one stationary in addition to one movable Platens have either T slots or tapped holes to fix the mold halves to the platens Tie Rods, usually 4, provide as long as precise alignment as the press is opened in addition to closed The press open in addition to shut height in addition to the platen temperature are controlled.
Compression Molding Compression presses are rated by their closing as long as ce capacities Can be manual, semiautomatic or fully automatic Pre as long as m temperature, molding temperature, molding pressure, molding time in addition to cooling time are the most important design parameters Cavity depth is very important to achieve the proper molded density Transfer Molding Similar to compression molding Four basic types Pot type transfer molding old technology Plunger transfer molding Automatic Transfer molding Screw transfer molding
Automatic Transfer Molding The plunger feeds the mold Completely automatic, but confined to the use of free flowing granular materials They have been slightly redesigned as long as other materials Screw Transfer Molding Uses an extruder to supply a precise weight, temperature in addition to density, shot, that feeds into the mold on a completely automatic basis Screw Transfer Molding
Laporte, Leo Executive Producer/Host
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