Plastics Information

What is laminating?

Lamination occurs when two or more layers of material are put together by either cohesion or adhesion. Plastic laminates are usually various layers of material held together by some sort polymer or plastic material. Laminates and reinforced plastics can be difficult to distinguish from reinforced plastics because the layers often provide strength and reinforcement as well to the base plastic material. The primary way to tell the two products apart is that laminates are usually made up of layers of material. Laminates are also primarily made in to flat sheet or tubes and rods versus reinforced plastics can be molded into complex shapes or geometries.

There are many types of laminates processes to consider. Processes like co-extrusion are technically a laminate. Many different materials can be laminated together as is the case in bullet resistant polycarbonate which is made up of polycarbonate, acrylic and some sort of urethane interlayer. Another process yields what are considered either low pressure laminates or high pressure laminates. For the purpose of this article we will focus on high pressure laminates, also called high pressure laminates.

A paper, fabric or cloth are usually saturated or impregnated in a plastic resin system of some kind of thermosetting resin system like melamine, phenolic, polyester or epoxy. Originally high pressure laminates found applications as counter top material. Today, these materials are being used in much more dynamic applications like printed circuit boards, gears and pulleys and the like.

A major disadvantage of high-pressure laminates is the slow production process compared to other plastics technology processes. However, the properties of the material in regards to strength and stiffness at elevated temperature can be a useful product in solving certain challenging applications.

If you would like a more information regarding high pressure laminates, click on this link to our online sortable material chart.

Plastics Information

What is Compression Molding?

Compression molding is a common process used for both thermoplastic and thermoset stock shape materials. Compression molding is accomplished by placing the plastic material (can be a granular or pelletized form) in a mold cavity to be formed by heat and pressure. The process is someone similar to making waffles. The heat and pressure force the materials into all areas of the mold. The heat and pressure cycle of the process will harden the material and then it can be removed.

Typically, thermosetting compounds like polyesters, phenolics, melamines and other resin systems are compression molded using alternating layers of different reinforcement materials to create a final product. However, there are various thermoplastics that are commercially compression molded as well.

Advantages of injection molding:

– Extremely low to zero residual stress left in stock shape.

– Can economically provide large parts.

– Tooling costs are relatively low.

Disadvantages:

– Flask may require trimming, can be sharp.

– Cycle times can be slow, a factor in producing larger volume orders.

– Can be higher priced than extruded products (when comparing thermoplastics).

Compression molding is a valuable tool where it has a fit. Obviously for thermosets, it is a primary process but in thermoplastics it can often times be useful in creating a base stock shape to machine extremely complex geometries without having to take excessive time and steps to anneal parts. This can increase production cycle time and reduce overall cost while delivering exceptional finished parts. For a complete listing of available compression molded thermoplastics for machining, give Plastics International a call or email us at sales@plasticsintl.com.