Plastics - Manufacturing

____________ plastics undergo a chemical reaction that causes the material to cross-link. Once this reaction takes place the material can not be returned to its original state.

____________ plastics undergo a chemical reaction that causes the material to cross-link. Once this reaction takes place the material can not be returned to its original state.

thermoset

When was the first plastic developed?

1869

________________ plastics can be heated to a point that it becomes viscous. This process can occur many times.

thermoplastic

LDPE (Low Density Polyethylene) would be used in what application?

• soda bottles

• cd cases

• plastic food wrap

• grocery/trash bags

soda bottles

What are two of the primary advantages of plastics as opposed to metals. (PICK TWO)

• mass/ weight

• stiffness/ rigidity

• manufacturing/ material cost

• look/ aesthetics

• mass/ weight

• manufacturing/ material cost

The closed molding process that forms a part by injecting liquid plastic into the mold and then letting it solidify is known as _________________.

Injection Molding

_____________ is a process that uses a mold and a liquid thermoplastic or thermoset. The plastic is allowed to flow into the mold using gravity until set. The mold is then opened to release the part. The mold may or may not be destroyed in the process.

casting

_____________ is a closed molding process that creates a seamless part that is hollow on the inside through the use of a rotating mold.

Rotational Molding

__________________ is a continuous process the forms a shaped plastic using a die.

Extrusion

____________ is a process that causes parts to rub over each other inside a rotating drum.

Tumbling

_____________ process is used to chop up failed parts to be reprocessed, most likely in a molding process.

Grinding

Plastics can be machined. (Milled, Cut, Turned, Planed, Shaped, Routed, Stamped, Drilled, and Tapped) WRONG OR CORRECT

CORRECT

_____________ is the most common type of cutting of plastic foam.

Hot wire cutting

A degating tool would most likely be used on what type of plastic?

Injection

Plastics can not be welded together. TRUE OR FALSE

False

_________________ uses a hot die to clamp and weld two pieces together. This is a common way to seal thin films such as that used to package products.

Thermal Heat Sealing

In the hot wire welding process the wire is left in the joint. TRUE OR FALSE

True

______________ is a welding process that rubs two pieces together under pressure along with an electrical current to create heat that will weld the two pieces together.

 Vibration Welding

________________ is an additive manufacturing process that melts a thermoplastic or similar material and extrudes it though a nozzle depositing it one layer at a time to create a 3d model.

Fused Deposition Modeling (FDM)

This process heats a material to just under its melt temperature and slowly cools to allow the part to relieve any internal stresses.

Annealing

What additive increases plastics ability to survive in hostile environments?

Antioxident

Plastic can not be conductive. TRUE OR FALSE

False

What are two common reinforcing agents added to plastic? (PICK TWO)

• wood fibers

• carbon fibers

• glass fibers

• carbon fibers

• glass fibers

_______________ is a process that causes plastic to polymerization, cross-link, and graft.

  Radiation Processing

______________ is a process that coats the part in a material like plastisol to create a smooth outer surface.

Dip Coating

________________ is a process that causes parts to rub over each other to create a better surface finish and, in some cases, remove flash from a molded part.

Tumbling

___________ is a process that uses an electric charge to cause particles of paint to stick to the part. The paint is then cured in an enclave. 

Power Coating

____________ is a process that uses a chemical that will dissolve the outer layer of the part to create a smooth surface.

Solvent Polishing

This is the process of adding a thin layer of material, typically chromium, silver, nickel, gold, ect, to a part

Electroplating

heat and pressure is applied to a material inside a metal mold, causing the material to soften and take shape of the mold

Compression molding

melted plastic is put inside a mold cavity, the plastic then cools and solidifies, resulting in the desired shape

Injection molding

involves the inflation of heated plastic withing a mold to form the desired shape; used to create hollow plastic products such as bottled, containers, and tanks

Blow molding

involves heating and rotating a mold filled with plastic powder until it coats the interior of the mold and forms the desired product; used to create complex hollow parts

rotational molding / rotomolding

relies on heating a thermoplastic sheet, forming it over a mold, and cooling it to create the desired shape; used to make packaging, trays, and automotive components

Thermoforming

involves forcing molten plastic through a die to form the desired shape as it cools and solidifies

Extrusion

involves heating material, typically pellets, and pressing it into a mold cavity to achieve the desired shape

Compression molding

involves pouring liquid plastic into a mold, allowing it to cure, and then removing the finished part

Casting

involves layering reinforcing fibers and resin by hand in a mold to form the desired shape; used to make fiberglass, carbon fiber, and Kevlar

Hand layup (Composite)

electricity is used to heat up a wire that can slice through plastic; used to cut foam into desired shapes

Hot wire cutting

used to remove undesired plastic from the seams of the mold and the gate

Deflashing / deburring - degating

parts are placed in a rotating drum, the parts bump into each other and / or media which removes undesired plastic

Tumbling

involves melting a plastic rod and extruding it onto the joint to create a strong seal

plastic extrusion welding

employs a heated wire to create strong, precise welds

Hot wire welding

pressure is applied to the plastic to soften in and high-frequency vibrations fuse together the joint

Ultrasonic Welding

plastic is heated then pressure is applied causing them to fuse together

Heat sealing

a heated adhesive is applied to one or both of the plastic components; the components are then brought together

Hot melts

heating plastic to very near its molding temperature and then slowly cooling it down; relives internal stress

annealing

causes crosslinking of polymers which changes the parts dimensional stability, temperature resistance, impact resistance, and chemical resistance.

Radiation processing

What are these?

• flame retardants

• lubricants

• UV absorbers

• heat stabilizers

• preservatives

• antioxidants

Plastic additives

What plastic additive:

• increases electrical conductivity

• increases thermal conductivity

• increases EMI/RFI shielding

metal

What plastic additive:

• increases strength

• increases rigidity

• decreases elastic modulus

Glass/carbon fibers