Bonding and Fastening TUFFAK® GP Polycarbonate sheet.

Mechnical Fastening Aluminum rivets and machine screws may be used to join TUFFAK^® Polycarbonate Sheet to other materials by utilizing proper attachment methods. Drill oversized holes and use washers to distribute and cushion localized stress. Be sure to consider differentials in expansion factors for dissimilar materials. Be sure drilled holes are smooth and free from cracks.

Solvent Bonding Many applications for TUFFAK^® Polycarbonate Sheet involve the fabrication of sheets to construct three-dimensional shapes. The most popular method is to solvent bond. TUFFAK^® Polycarbonate Sheet solvent bonding can be achieved using methods employed in fabricating other thermoplastics such as acrylic. The most common methods are needle-type applicator capillary action and edge dipping. Both methods rely on smooth edge preparation, pressure, and curing. It should be noted that solvent bonding will significantly reduce the strength of polycarbonate.

Procedure:

• Smaller items with flat surfaces can be bonded by placing the pieces together and applying the solvent along the edges using a needle applicator or hypodermic syringe. Make sure the solvent flows along the entire joint.
• For bonding larger items, immerse the surfaces to be joined in the solvent until the material is softened.
• Clamp them in position and hold until the bond is set.

Helpful Hints:

• Edges must be clean and dirt-free.
• Surfaces should be smooth and properly aligned.
• Apply even pressure to reduce bubbles in the bond area.

Techniques To Reduce Whitening:

1. Fabricate in a climate-controlled area with low relative humidity.

2. The addition of 10% glacial acetic acid in the solvent reduces whitening.

3. Thickening the solvent with polycarbonate resin or sawdust promotes slower curing and reduces whitening.

4. Joint cure time is somewhat longer than acrylic. Be sure to retain fixture pressure until the joint is solid.

Note: Use extreme caution when working with solvents. Adequate ventilation is essential. Control exposure levels according to OSHA guidelines. Obtain Material Safety Data Sheets from the solvent manufacturer.

Transfer Tape Bonding

Achieving a strong edge bond using solvents on thin-gauge thermoplastics is challenging due to the reduced size of the bond area. Structural bonding of thin-gauge TUFFAK^® Polycarbonate Sheet can be accomplished, however, by utilizing acrylic-based transfer

tapes along with slight design modifications.

Procedure:

• Bend a small return on the right part to be fastened approximately the width of the transfer tape.
• Clean tape contact areas with 50/50 isopropyl alcohol-water mixture.
• Apply transfer tape to the return.
• Remove tape masking and press the part into place.

Helpful Hints:

• Rolling the bonded area with a small wood or rubber roller improves bond strength.
• A nonstick slip sheet is useful for properly positioning large or hard-to-handle parts.
• Peel strength of long, lineal bonded areas can be increased by adding a mechanical fastener at both ends of the bond.

Welding

While mechanical fastening and solvent bonding are the most often recommended methods for joining plastics, another alternative is welding. Ultrasonic, radio frequency and spin welding have proven to be appropriate. Contact manufacturers of ultrasonic welding equipment for recommendations on section and joint design.