Chip-In-Place Pattern Guidelines
The following guidelines are based on laboratory experimentation and may not be representative of results obtained in an actual production environment. However, they appear to be directionally correct, and may be used as starting points to identify actual desired patterns. The following data was derived using 3/16 inch thick float glass.
Note: It is imperative to follow all safety guidelines and protocols that apply to the Chip-In-Place polymer and selected UV curing equipment. Appropriate safety glasses, protective clothing, and gloves should be worn at all times during this process. Read and comprehend all MSDS and instruction manuals before proceeding.
Fine Chip Pattern
To achieve a chip pattern that is more delicate and subtle, a polymer coating weight of between 0.6 and 0.85 grams/in2 is recommended. This coating weight would translate to a wet coating thickness of about 50 mils. These weights should be reduced if areas greater than 2 ft2are being chipped. If very small areas (less than 2 in2) are to be chipped a greater coating weight might be required.
Typically, the polymer will generate enough internal stress to self-chip: no mechanical action is required. Chip-in-place should occur within 30-45 minutes after UV curing. Occasionally, when using these lighter coating weights, it may become necessary to initiate the chip-in-place process by tapping the cured polymer with a razor knife. This should be done very cautiously as a great deal of stress will be present in the polymer. After the fracturing occurs, it may be necessary to lightly scrape the surface of the chipped area with a razor knife blade to assure all glass and cured polymer has been removed.
Large Chip Pattern
To obtain a pattern that is similar to double or triple glue chipped glass, a coating weight of 1.0 to 1.5 grams/in2 is required. This coating weight would translate into a wet film thickness of about 75 mils.
Due to the heat and stress generated by this amount of polymer, these coating weights are not recommended for areas greater than 2 ft2. This high coating weight typically does not require initiation to begin the chip-in-place process; enough stress is typically formed inside the cured polymer to self-initiate the chip-in-place process.
Self-initiation typically occurs within 30-45 minutes after UV curing the polymer. Extreme care should be taken in the event that chip initiation using a razor knife is required after this time period. Large surface areas with high coating weights impart great stress on the polymer. There is a chance that the glass can shatter from aggressive tapping and scraping with the razor knife.
It is not uncommon for a small amount of polymer to be firmly affixed to the extreme edge of the chipped area. This polymer might even be extremely sticky. This material can be removed using a razor. As with the lower coating weight process, it might be necessary to scrape the surface of the chipped area with a razor blade to assure all the glass and polymer has been removed.
Curing The Polymer
Chip-In-Place polymers must be cured using UV light of moderate to high intensity. The UV energy produced by black lights is not sufficient for use with this material.
A wide range of UV-curing equipment is commercially available that is suitable for this Chip-In-Place polymer. The amount of exposure time required to completely cure the polymer depends upon the energy output of the UV lamp and its distance from the glass surface.
As a minimum, a UV lamp capable of producing 50mW/cm2 fitted with a parabolic reflector (flood type lamp that generates collimated light) is recommended. With most UV flood lamps of this intensity, an exposure of 1 to 3 minutes is required to fully cure the polymer. Using higher intensity UV lamps can reduce the required curing time.
UV curing typically produces heat, both from the lamp and the polymer. Because relatively thick films of polymer are being UV cured, a noticeable amount of heat can be expected. This is normal for this process. There will also be some gases liberated upon curing. It is recommended that curing be conducted in an area with good ventilation.