Glazing Instructions Laminated Polycarbonates

The glazing characteristics of these plastics are substantially different from those of glass. Particular attention must be paid to expansion and contraction, adhesion and compatibility with glazing materials, preparation of the glazing rabbet and deflection. The modulus of elasticity of polycarbonate is 345,000 psi and glass id 10,400,000 psi. If polycarbonate and glass of the same size and thickness are subjected to identical uniform loads, the deflection of the polycarbonate will be approximately 30 times that of the glass.

The following general recommendations should always be compared and supplemented with the latest information available from manufacturers.

1. Plastic sheets or panels should be installed in a metal frame engaging the edges of the material so the material is free to expand and contract without restraint.

2. The rabbet depth should be sufficient to allow for the thermal contraction or deflection of the plastic without withdrawal of the edges from the frame.

3. Through-bolting or other inflexible fastenings, which do not provide for expansion and contraction, can cause failure of the installation.

4. Before installation in the metal frame, plastics should be cut sufficiently shorter than the channel frame dimensions to allow for thermal expansion.

5. Sealant compounds and tapes should be types that are sufficiently extensible to accommodate thermal expansion and contraction and which adhere to both the plastic and frame.

6. Depth and width requirements of the rabbet are determined by type, thickness, and wind load requirements. See plastic manufacturer's recommendations for minimum rabbet size limitations.

7. With pressure equalization and weep systems, it may be necessary to use setting blocks to prevent blockage of weep holes. With non-pressure equalization system, it is permissible to set the sheets directly on the bottom of the sill member.

8. Wash with mild soap or detergent and water. Use as much water as possible in washing. Apply to large areas with a bristle mop used in a window washing and to smaller areas with a clean, soft cloth, sponge, or chamois.

9. Use a clean, damp chamois if it is necessary to dry the washed surface.

10. Sash designs suited for glass are not necessarily suited for glazing plastics. At dimensions (height or width) greater than 72", more bite is required than on glass.

11. Glazing systems should be installed in accordance with a good glazing practices.

12. Plastic sheets with major dimension greater than 24" should be installed with a continuous bead. Glazing compound should never be used; only elastomeric sealants with adequate elongation characteristics and proven adhesion to the particular substrate should be used.

13. All surfaces of wood and steel should be prime painted as required by the manufacturer before application of sealants. Aluminum sash should be cleaned with an appropriate solvent to remove protective finishes and grease. Under no circumstances should plastic be exposed to solvents such as Xylol, Toluol, MEK, ect. VM & P Naphtha may be used as effective cleaner.

14. Unmask plastic sheet edges before installing. This will protect glazing during installation. Unmask entire sheet immediately after installation.

15. The edges of a plastic lite should be thoroughly cleaned with VM & P Naphtha before setting in sash.

16. Protect plastic from excess sealant smear with a paper-backed adhesive tape around the edges adjacent to the rabbets.

17. Plastic glazing should be regarded as a finishing operation and should be scheduled as one of the last steps in the completion of the building. If this is not practical, acrylic plastics should be protected from paint, plaster, and tar splashes with a drop cloths or other suitable covering.