What is structural foam molding and Why Do We Use Them?

structural foam moldingThis is a molding process that allows manufacturers to produce very large structural parts. Though it bears some similarities to injection molding, this method can be accomplished with much less pressure than that which is required for more conventional processes. Therefore, parts are likely to have thicker wall sections. The end product tends to be lightweight and rigid with a relatively hard surface.
High Pressures Not Needed The structural foam molding process requires an inert gas (such as nitrogen) to be mixed with the chosen plastic material inside an extruder barrel. This mixture is then injected into a mold using less pressure than what is common in injection molding.

Once injected, the gas expands, filling the mold cavity. Alternatively, a chemical reaction within the blend itself may lead to the desired foaming action. When the foaming plastic touches the cold mold wall it solidifies, producing a thin layer of skin. This skin is supported by a cellular structure that is not dissimilar to wood products. Unlike injection molding, high pressures are not needed. The foaming action caused by the gas is sufficient to create the part.

Polyurethane structural foam is a lightweight, durable material created by injecting a two-part thermoset polyurethane resin into a mold. The chemical reaction produces a foam core with a solid surface skin that can be seamlessly in-mold painted. Known for its exceptional strength-to-weight ratio, structural foam is ideal for manufacturing large, complex parts requiring durability and reduced weight.

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Structural foam parts are extremely lightweight &#; typical weights vary from 55 pounds per cubic foot to a mere 2 pounds per cubic foot. In addition to this decrease in weight, structural foam is strong, durable, and extremely stiff &#; in fact, up to 8 times stiffer than similar materials such as solid polymers. The modulus of the material increases along with its density, up to a fantastic 250,000 psi. In addition to this, since it is a foam, the material makes for a great thermal and acoustic insulator.

Structural foam is also highly moldable; it is able to produce variant wall thicknesses across a single part. In some cases, structural foam has even been able to generate wall thicknesses greater than the previous maximum of ½ inch (13mm). It also allows for thick ribs and bosses and reduces the risk of &#;sinks&#; over ribs or heavy cross-sections due to the lower viscosity of the mixture. Structural foam products experience less stresses overall during the molding process, and are highly resistant to warpage or deformation.

In addition, structural foam retains the impact, element and temperature resistance common to thermoplastic and thermoset polymers. It experiences minimal to no thermal expansion, making it perfect for products which will be utilized in a wide variety of climates or temperatures. The acoustic and sound dampening properties of structural foam are also superior to those of standard solid polymers.

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Structural foam molding is also a highly cost-efficient process. Lower pressures and clamping forces are required during the injection and curing periods, allowing the tooling and molds to be made from lower cost materials such as aluminum. Cycle times are competitive with those of injection and reaction injection molding, making this a time-saving process as well as a money-saving one.

Structural foam products have a lower than average risk of damage in the mold or during the removal process, making it a highly efficient and easily repeatable method. In addition, structural foam produces no potentially harmful styrene fumes, lowering the health risks for workers involved in the molding process.

Lastly, structural foam also features highly paintable, aesthetically pleasing surfaces. In-mold painting (IMP) is possible for all structural foam products, further saving time and money. Multiple colors can also be applied to a single part in-mold. The surface is easy to clean and can be sawn, screwed, nailed or stapled without experiencing any problems.