Another of the original polymeric materials, PHENOLIC, known originally as BAKELITE®, has been available since 1909. Past their prime due to the advent of polymers that are more easily processed to finished products, are less damaging to the environment to manufacture and are better suited to end uses, PHENOLICS are still significant in the production of electrical insulating parts, which helps to explain the large number of specifications shown above. As well, large amounts of PHENOLIC adhesives are used in the production of wafer board, particleboard and plywood. Still used in items such as gears, bearings and wear plates, PHENOLICS are being replaced in these areas by Nylons, Acetals and for higher temperature uses PET, PEEK and PAI; mainly because of the allergic and dust hazards involved in machining PHENOLICS.

PHENOLICS, often referred to as "industrial laminates", are produced by moulding items with a laminated structure. To enhance and vary the properties of PHENOLIC resin, reinforcing media such as paper (X-grades), cotton woven fabric (C-grades), linen woven fabric (L-grades) and Nylon or aramid woven fabric (N-grades) are used. Compound variations result in grades that are hard surfaced, tough enough to be punched, higher temperature resistant, flame retardant, possess higher stiffness and strength, have lower abrasion resistance and lower frictional properties. Since PHENOLICS are thermosetting, they do not soften when heated; in fact, when overheated they embrittle and char. Usually, paper based grades are least expensive, have quite good primary electrical insulation properties, reasonable mechanical properties and poor machinability; cotton fabric grades have greater strength, better machinability and lower, non-primary, electrical insulation qualities; linen fabric grades, due to the fine weave of the fabric, have higher strength than the cotton fabric grades, have higher dimensional stability and slightly better electrical insulation properties but still non-primary; nylon or aramid grades have better abrasion resistance, greater impact resistance and temperature resistance plus lower moisture absorption. Although cotton and linen based grades machine well, problems with phenol and formaldehyde fumes and dust from dry machining often out-weigh the better machinability. Also, due to their laminated structure, exposed inner surfaces absorb lubricants, coolants or liquid chemicals causing swelling and poor dimension results. Thus, machining dry is a must and usage for parts exposed to liquids is a low priority. PHENOLICS do not possess good abrasion resistance and thus are not suitable for wear resistant parts subject to grit or dust. With good hardness and compressive strength, PHENOLICS are suitable for use as bushings, thrust washers, bearing plates, etc. but due to a high coefficient of friction, particularly when the reinforcing media is exposed, lubrication is a must.

PLEASE NOTE:
Values shown in the above table are averages and there will be variances from lot to lot. After selecting a material based upon these values, you must conduct tests specific to your application to be assured the material suits your needs.

Since PHENOLICS are a laminated structure, there is considerable variation in tensile and impact properties depending whether measured lengthwise (LW) with the reinforcing media producing the greatest effect; or, crosswise (CW) with the "grain" of the structure causing lower results. Items such as gears must be made from plate discs or rings with teeth cut across the laminations. This produces a much stronger part than gears cut from moulded rod, which has a radial lamination pattern, and teeth cut with the laminations would have little reinforcement. As well, drilling and/or tapping in the "grain" of the reinforcing media causes cracking or splitting.

Moulded Rod is produced by rolling resin impregnated fabric or paper and heating the piece which cures the resin to final properties. The cured piece is then centre-less ground to the final size. The Moulded Rod has the same grain structure as a tree.

Turned Rod, sometimes called "sheet rod", is produced by cutting square strips from finish-cured plate. These strips are then machine turned to a round section. The Turned Rod has the same grain structure as a piece of machine turned plywood.

The GRAIN of the rod is as important a consideration as is the type of material. Orientation of teeth, under-cuts, holes, key-ways and other cuts into the material must be carefully evaluated during design. An under-cut or hole tapped in the wrong direction can result in a part that will fall apart with only slight force applied. At Claremont Polymer Shapes, our expertise is available to help you avoid pitfalls like this.