Thermoset Laminate Manufacturing
The two primary processes for manufacturing thermoset laminate sheet are (1) Low Pressure and (2) High Pressure.
Low Pressure Laminates
Low pressure laminates typically use a glass mat substrate. Typical resins used in the low pressure laminate manufacturing process include polyester, vinyl ester, and epoxy. The process produces an excellent combination of mechanical strength, dielectric properties, and thermal performance. One advantage of the low pressure laminate manufacturing process is the ability to use a variety of fillers and additives to create a range of desirable properties from flame retardance to track resistance.
The manufacturing process for our low pressure thermoset laminate sheet materials begins with the selection of the proper resin formulation to provide the properties required for a specific application. Low pressure laminates are typically made following the same basic steps as follows:
Step 1) Continous strand random mat glass is received in roll form with various weights, constructions, sizing, and thicknesses depending on the product being manufactured.
Step 2) Glass mat is cut to length to create glass packages of various builds depending on the sheet thickness and product formulation for the product being manufactured.
Step 3) Not Shown. Resins are received and stored in large tanks. Depending on the material grade, there may be as many as 20 resin system components.
Step 4) The various resin components are mixed with filler additivies to add properties such as track resistance, flame retardance, and thermal endurance. The resin is then applied to the glass fiber package on an automated press loading table with CNC controlled weight scales.
Step 5) The press is automatically loaded and computer controlled for the proper pressure and heat curing profile for the product being manufactured. The sheets are molded individually in a press cycle that can vary from several minutes to a half hour or so.
Step 6) Sheets are unloaded with automated material handling equipment. Sheets are inspected for quality and manufacturing tolerances with sample lots sent to the laboratory for verification testing for properties including flexural strength and dielectric strength.
Step 7) Sheets are labelled by lot and packaged for shipment to our fabrication plant for machining into finished parts per our customer requirements.
The low pressure laminate manufacturing process is considered to be more cost effective than the high pressure laminate process due to the faster cycle time from the beginning of the process to the end of the process. With composite materials, there are always trade-offs among the properties of the various materials depending, in part, on the manufacturing process.
High Pressure Laminates
High pressure laminates may use several substrates such as kraft paper, mica paper, canvas or linen (cotton) cloth, or glass cloth. Typical resins used in a high pressure laminate manufacturing process include phenolic, epoxy, melamine, silicone, and polyimide. The process produces outstanding mechanical strength, especially in compression. High pressure laminates also have excellent dielectric strength and related electrical properties. Each combination of substrate and resin provides a different set of properties.
The manufacturing process for our high pressure thermoset laminate sheet material begins with the selection of the proper substrate and resin for the particular application. All high pressure thermoset laminates follow the same basic process as follows:
Step 1) Substrate or base materials such as paper or glass cloth arrive at the plant in master rolls with a thickness ranging from .003" to .010".
Step 2) The base material is passed through a resin bath in order to impregnate the substrate with a resin such as phenolic, epoxy, melamine, or silicone.
Step 3) After the base material has been impregnated, it is passed through a treating oven to drive off the solvents in the resin and precisely allocate the correct amount of resin on the substrate.
Step 4) After being treated, the composite is now considered to be in its "B-Stage". The B-Stage composite is then cut to size and stacked (called Prebuild) depending on the thickness of the sheet being produced. The material is then loaded in the laminating press.
Step 5) The cut to size prebuild is placed in the press under heat and pressure which results in the finished laminate sheets. Typical press loads can hold anywhere from 8" - 14" worth of sheet material and may take up to several hours to fully cure depending on the grade being produced.
Step 6) After being removed from the press, the sheets are trimmed and sanded to thickness as required.
Step 7) The sheets are inspected for quality with lot samples tested in the laboratory for specification compliance. Sheets are then packaged and shipped to a TGC facility for fabrication into machined components according to customer drawings and specifications.
Though a longer process cycle than the low pressure laminate manufacturing process, the higher mechanical strengths and unique properties generally produced by the high pressure laminate manufacturing process allow for specific performance characteristics required by many demanding applications.
