Thermoset vs. Thermoplastics

September 12, 2017

Thermosets are an attractive alternative to metals and thermoplastics due to its exceptional physical properties and surface appearance. Thermoset composites remain stable in high and dynamic temperature applications, a beneficial quality in the rapidly shifting world of manufacturing.

Thermosetting resins are popular because they are processed at low pressures and viscosities. This allows for convenient impregnation of reinforcing fibers such as fiberglass, carbon fiber, or Kevlar.

Properties and Benefits of Thermoset Resins

A room temperature liquid resin is easy to work with. Laminators can easily remove all air during manufacturing, allowing the ability to rapidly produce products using a vacuum or positive pressure pump. Beyond ease of manufacturing, thermosetting resins can exhibit excellent properties at a low raw material cost.

While all thermoset plastics share the same basic manufacturing process, one of the best things about their material specifications is their flexibility. There are many types of different thermosetting plastics, including; epoxies, silicones, polyesters, polyurethanes, and phenolics. Each of these will have its own unique characteristic that will make it suitable for a different type of part. For example, epoxies typically provide elasticity, toughness, and excellent chemical resistance while phenolics will usually provide similar benefits with exceptional flame resistance.

Thermosetting is extensively used in everything – from electrical insulation to automotive manufacturing. Every day, new thermosetting composites are created to match a wider array of complicated industrial applications. The right thermoset plastic composite can not only match, but exceed, the material specifications of a huge variety of other production materials (without compromising the ease of manufacture that makes thermoset plastics so valuable).

The Advantages of RIM Process:

Compared to thermoplastic injection molding, which requires high heat and high pressure to press melted plastic
pellets into a steel mold, RIM parts are formed when two liquid components (polyol and isocyanate) chemically
react inside a mold.

The RIM process offers many advantages over competing technologies including:

Very large, lightweight parts

The “flowability” of polyurethane components means the material is distributed evenly inside the mold. This lets
you produce large parts, which is not possible with injection molding. Because mold pressures are much lower,
large presses are not necessary.

Varied Wall Thickness

Producing significant variable wall thickness within the same molded part is achievable with RIM. Wall
thickness ranges between .25 inches and 1.125 inches are possible cross-sections in the same molded part. This is
NOT true for thermoplastic injection molding, blow molding, sheet molding compound and other polymers

Low Tooling Costs

RIM tooling costs are significantly less than that of an injection mold. Because the RIM process incorporates low
temperatures and low mold temperatures and pressure, the tool can me made out of less expensive mold materials
other than steel such as cast aluminum, aluminum, kirksite alloys, nickel, epoxy, silicone and fiberglass. The
choice depends on such factors as the number of parts to be made; dimensions, shapes, and tolerances; the quality
and texture of the surface; mold life; required mold cost; and part performance. The larger the mold, the greater
the savings.

Freedom of design

RIM lets you mold highly detailed, intricate parts at relatively low tooling and capital equipment costs. Parts with
varying wall thicknesses can be designed into the same molded part.

Encapsulation of Inserts

Different types of inserts and be placed into a mold prior to injection of the RIM material, and the RIM material
can encapsulate many inserts during molding. Inserts such as steel, aluminum, glass, wood, electronic sensors,
PC boards and wiring harnesses are some examples of material that have been encapsulated.

Rapid prototypes

Excellent working prototypes can be developed with lead times of 3-15 days, at a cost much less than traditional
injection molding.

Class A Surfaces

The surface finish of RIM parts allows manufacturers to produce Class A painted parts – high-gloss finishes that
match high-gloss painted metal parts.

In-Mold Painting

With the RIM process, it’s possible to apply gel-coats and two-component polyurethane in-mold paints into the
mold prior to injection. The injected polyurethane material bonds to the gel-coat or paint during molding,
allowing a decorated part to be produced in the mold. This can significantly reduce secondary finishing costs.

Other Benefits

High strength, dimensional stability, good weatherability, scratch resistant, heat resistant, impact
resistant, resistant to organic and inorganic acids, and high R Value.

Romeorim design guide