3350 W. 48th Pl. Chicago, IL 60632-3000. Phone 773-927-3484, FAX 773-650-5853.
Source for liquid thermosets: silicones, moldmaking urethanes, casting plastics, polyester resins, epoxy.
Fiberglass fabrics, release agents, fillers and dyes.
All products available in small quantity.

Technical Resources

Frequently Asked Questions

What is the shelf-life of liquid silicones and how long will my silicone mold last once it has been poured? Answer
What is the easiest way to replicate parts of the body? Answer
Should I make a brush-on rubber mold or a solid rubber mold? Answer
I've decided to make a brush on mold, should I use latex or urethane? Answer

How do I successfully make a crystal clear casting? Answer
What are the surface wrinkles of my crystal clear polyester casting and how do I buff them out? Answer
What is the difference between crystal clear urethanes and crystal clear polyester casting resins? Answer
What is the easiest way to cold cast metal parts? Answer
My plastic parts seem week and brittle. Can I do anything to strengthen them? Answer
What if want to cast PARTS out of silicone? Answer
What is the best mold making material for casting polyester or building fiberglass parts? Answer
Does Eager Polymers supply any low melting temperature metals such as pewter? Answer - Yes

Will you send me free samples of your products? Answer
Why can't you ship urethane foam to me during hot months? Answer
What is the Eager Polymers price structure? Why aren't prices shown on your website? Can I order Online? Answer

What are the white flakes in my epoxy resin and how do I get rid of them? Answer
What type of resin system is recommended for laminating carbon fiber, graphite fiber or Kevlar? Answer
What is the shelf-life of a typical urethane? Answer

BOAT REPAIR IN CHICAGO - Find products useful for do-it-yourself boat (sailboat, kayak, canoe, yacht) repair and find links to Chicago-area companies dedicated to boat repair.

Introduction to Plastics

A plastic is a sub-class of the material type called polymers. Polymers are partly amorphous (glass-like) and partly crystalline (like most metals and ceramics). You can imagine long chains of organic molecules like spaghetti that are tangled up in a mess. The specific surface chemistry and length of these molecules help determine how they behave.

The two main types of plastics are called Thermosets and Thermoplastics.

Thermoplastic materials require heat to form them. Typically, these systems start off as tiny pea-sized pellets that are melted and formed to net shape. One of the most common methods is by injection molding. After cooling, they retain the shape into which they have been formed. They are solids at low temperatures and begin to soften as the temperature is increased until finally, it melts and forms a liquid. You can think of thermoplastic plastics as a low melting temperature glass.

These systems are recylable. Some common examples include:

HDPE (high-density polyethylene) - Grocery bags, food containers
LDPE (low-density polyethylene) - Grocery bags, food containers
PVC (polyvinyl chloride) - Pipes
PP (polyproplyene)
PS (polystyrene)
ABS - car parts
PMMA (polymethyl methacrylate)

Thermosets, however, are formed into a net shape and "set" in place through a chemical reaction. Sometimes this chemical reaction can be induced by UV light or subjecting it to a tailored environment. More commonly, thermosets are comprised of two-component systems that will react with each other upon contact. This type of system cannot be recylced, and upon application of too high a tempeature, will begin to degrade or decompose.

Some examples include polyesters, silicones, urethanes and epoxies.

Thermosets are the only type of plastic material that Eager Polymers carries. There are millions of different types of thermosets. Some properties to consider when determining which system is best for you are: cure time, pot life, tensile strength, cured color, viscosity, hardness, etc.

Moldmaking Industry Definitions

Viscosity: A measure of the resistance to flow of a liquid, sometimes measured in terms of centipoise (cps). The higher the viscosity the thicker the liquid.

Hardness: The resistance of a material to permanent deformation. There are many scales to measure the hardness, but the most common in the plastics industry are Shore 'A' (softer materials) and Shore 'D' (for Harder materials). How easy it is to flex a rubber is dependent upon both the hardness and on the thickness. A soft material that is very thick may appear to be stiffer than a hard material that is very thin. Think of glass fibers that you can easily bend in a circle versus a window pane that will shatter if bent to far. Lowering the temperature of a material not only decreases its flexibilty, but it also makes it more susceptible to a brittle fracture. This is part of the reason the Challenger exploded shortly after take-off. The O-ring, which is normally flexible at room temperature, was very weak and brittle on the cold launch day.

Tensile strength: How much weight per unit area a material can withstand at room temperature until it begins to permanently be defomred, often measured in psi (pounds per square inch). A material with a tensile strength of 5,000 psi means that a 1" x 1" square rod would be able to withstand a 5,000 pound application before it would be permanently deformed. The tensile strength usually decreases as the temperature is increased.

Pot life: Amount of time you have after you have mixed the two components until reaction begins and the system begins to set.

Demold time: Amount of time after you first mix the two components and pour it into the mold until it is stiff enough to remove from the mold. At this point, the part has not reached full strength.

Cure time: Amount of time after first mix that the material has effectively achieved "full strength"

Filler: Materials that serve as thickening agents (cab-o-sil), act to take up space to reduce the amount of resin used and make the part more light-weight (microballoons, fillite), or to achieve a metallic appearance (bronze, brass, (aluminum, iron powders).

UV protection: Some clear plastic resins yellow over time when exposed to UV light. A special additive that protects the plastic from yellowing is added to some systems, but usually drives the cost up.

Transparent dye: A dye that will allow you to at a slight color to a clear system. Think about putting a tiny amount of food coloring in a large glass container of water. Light can still be transmitted through a system with transparent dye. This is the effect you can achieve in clear plastics systems with our product EP7701.

Opaque dye: A very concentrated pigment which acts to color a plastic system so that no light can travel through. Our selection of opaque dyes are named EP7702.

If you would like to learn more about the technical properties of plastics, check out some of the links below:

The American Plastics Council gives a great overview of the plastics industry including the history, processing and chemistry of plastics.

The Society of the Plastics Industry is another good source for plastics specifics.

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