Lecture 8

compounding

rubber is always compounded with additives to enhance the rubber's mechanical properties or to extend the rubber to reduce cost

calendering

rubber stock is passed through a series of gaps of decreasing size by a stand of rotating rolls

injection molding

same as metal but with PMC

three principle process parameters in curing

time, temp, pressure

reinforcing agent

ceramics, metals, other polymers, or elements such as boron or carbon. can be fibers, flakes, or particles

compression mold

charge is placed in lower mold section, and the mold sections are brought together under pressure, forcing charge to take the shape of the cavity

transfer mold

charge of thermosetting resin with short fibers is placed in a pot or chamber, heated, and squeezed by a ram action into one or more mold cavities

shaping processes for rubber

extrusion, calendaring, coating, molding and casting

prepregs

fibers impregnated with partially cured TS resins to facilitate shape processing

open mold FRP processes

hand lay-up, spray-up, automated tape-laying machines and fiber placement machines

spray up method

liquid resin and chopped fibers are sprayed onto an open mold

synthetic rubber

made from petroleum

carbon black

most important reinforcing filler for tires (increases tensile strength, resistance to abrasion and tearing, provides UV protection

rubber industries

natural rubber producers, synthetic rubber producers, processers that turn the rubber into products

two types of rubber

natural, synthetic

categories of fiber reinforced plastic shaping processes

open mold processes, closed mold processes, filament winding, pultrusion

how is rubber delivered

bales

vulcanization

the treatment that accomplishes cross-linking of elastomer molecules, increases the stiffness and strength of the rubber

polymer matrix

thermosetting (TS) polymers are the most common matrix materials

rubber industry is dominated by

tires

hand lay-up method

open mold shaping where successive layers of resin and reinforcement are manually applied to an open mold to build the laminated FRP composite structure

closed mold processes

performed in molds consisting of two sections that open and close each molding cycle

filament winding

resin-impregnated continuous fibers are wrapped around a rotating mandrel that has the internal shape of the desired FRP product

extrusion

screw extruders are generally used to force rubber through hole

pultrusion processes

similar to extrusion but the workpiece is pulled through the die rather than pushed