Pultrusions

This process can produces products that meet very high structural requirements, high weight-to-strength performances, electrical requirements, etc. The material most commonly used is TS polyester with glass fiber. Other TS plastics, such as epoxy and polyurethane are used where their improved properties are needed. When required fiber material in mat or woven form is added for cross-ply properties. 

In contrast to extrusion, in this process a combination of liquid resin and continuous fibers (or combined with short fibers) is pulled continuously through a heated die of the shape required for continuous profiles. Extruder pushes the material. Glass content typically ranges from 25 to 75 wt% for sheet and shapes, and at least 75% for rods. 

Typical applications of pultruded products are extensive and serve many different industries  

Development in equipment continues. As an example, a line of low-cost pultrusion machines with electromechanical controls, eliminating high maintenance costs and minimizing noise, has been developed by Composites Machines Co, Salt Lake City, USA. The advanced technology pultrusion (A TP) line comprises three series  

Choice of carrier film offers two alternatives a relatively high-cost film, which can be re-used several times, or a lower-cost film that can be left adhering to the surface of the sheet, as a protection in transit. The process can also be used for production of simple open profiles without sharp angles. 

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The Automatic processes are those such as pultrusion, filament winding, centrifugal casting and injection moulding. 

Rosato, D.V. ed. Rosato, D.V. (ed.) Blow Moulding Handbook, Hanser, Munich (1989). Hepburn, C. Polyurethane Elastomers (ch 6-RIM) Applied Science Publishers, London (1982). Martin, L, Pultrusion Ch 3 in Plastics Product Design Handbook - B ed by E. Miller, Dekker Inc, New York (1983). 

Pultrusion is also used to make structural shapes from composite materials. The incoming material is generally unidirectional and must be pulled through the pultrusion die because the uncured composite material is entirely too flexible to push (as in extrusion processes). The incoming material can be preshaped by various guides and rollers as in Figure 1-18. 

For composite stiffeners, all shapes are builtup from individual layers of material. Of course, some stiffener shapes can be produced by roll forming or pultrusion, for example, and then fastened to panels. Or, the stiffened panel could be made in a single operation involving the placement, usually by hand, of individual laminae of various dimensions in positions such that a builtup structure results. Stiffeners can be fastened to panels by bonding, stitching, or mechanical fastening. 

Process used provides different control capabilities. As an example closed molding (injection, compression, etc.) provides fine detail on all surfaces. Open molding (blow molding, thermoforming, spray-up, etc.) provides detail only on the one side in contact with the mold, leaving the second side free-formed. Continuous production (extrusion and pultrusion) yields products of continuous length. Hollow (rotational or blow) produces hollow products. These processes can be used creatively to make different types of products. For example, two molded or thermo-formed components can be bonded together to form a hollow product, or they can be blow molded. 

Unidirectional construction Refers to fibers that are oriented in the same direction, such as unidirectional fabric, tape, or laminate, often called UD. Such parallel alignment is included in pultrusion and filament winding applications. 

Filament Winding, Hand Layup. Compression Molding. Iniectior. Molding. Vacuum Bag. Stamping. Coming. Pultrusion... 

Compression molding Filament winding Hand lay-up Mat molding Pressure bag molding Continuous pultrusion Injection molding Spray-up... 

Fluorocarbons Very high heat and chemical resistance, nonburning, lowest coefficient of friction, high dimensional stability Injection molding Encapsulation Continuous pultrusion... 

Contact Molding. Spray-up Pressure Bag Filament Winding Continuous Pultrusion Premix/ Molding Compound Matched Die Molding with Preform or Mat... 

Open-cast molding Fiber spinning Blow molding Injection molding Extrusion/pultrusion Reaction injection molding... 

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