Letters: 02/02

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BioPlastics On Burning Holes In BioThane Tack
I am writing in regard to the December 2001 article on BioThane bridles. It was wonderful, except for one potential problem with the heated nail and melting information in the article.

BioPlastics Company takes a proactive approach in explaining the dangers of fumes emitted when heating Beta material (PVC). Every Beta order that leaves our plant has a sheet with guidelines on heat-sealing PVC coated material. Our customers are familiar with this, but I doubt if the general public has a clue.

I’m including a copy of the guidelines in this letter (see below). We need to inform your readers of these guidelines to prevent inhalation possibilities. Burning or melting PVC emits hydrogen chloride (HCL), which is dangerous.

-Christine Kilen
BioPlastics Company


From The BioPlastics Company:
Heat-Sealing Edges and Holes When Using BioThane PVC-Coated Webbing Beta Series

The following guidelines and precautions are to assist our customers when heat-sealing the Beta Class PVC-coated webbing. BioPlastics recommends that our customers develop safe work practice programs specifically designed for their individual operations.

At degradation temperatures, this product will emit hydrogen chloride (HCL) fumes, which may cause irritation of the eyes, skin and respiratory tract. The amount of emissions will depend upon the time and temperature used by your heat-sealing apparatus.

CAUTION! Prolonged heating (approximately 10 minutes or more) of the product above 200?°C (392?°F), or short-term heating at 250?°C (482?°F), may result in rapid PVC degradation and evolution of hydrogen chloride.

As a general rule, PVC degradation begins to occur after about one hour at 177?°C (350?°F), after about 10 minutes at 204?°C (400?°F), and within five minutes at 232?°C (450?°F). Equipment should not be shut down for extended time periods with the product in or on it. Decomposition and possible corrosion of unprotected metal may result.

As previously mentioned, hydrogen chloride becomes an acid and will have a corrosive effect upon many metals. Since this corrosion can be a slow process which will take place long after initial exposure, prompt cleaning of surfaces with water-based detergents is recommended.

Perform sealing in a well-ventilated area. Effective exhaust ventilation should be provided to draw fumes or vapors out of the building and away from workers. Ventilation should include an exhaust fan system. You need to remove the contaminated air from the work area. Consult with your local safety equipment dealer for equipment recommendations.

Keep heat-sealing equipment and surfaces clean. Clean up following normal melt processing should be performed under well-ventilated conditions.

Time, temperature and pressure are important factors when sealing holes or edges. Belt surface temperatures of 121?°C (250?°F), to 157?°C (315?°F) should be sufficient for sealing the Beta class. These temperatures are well below the degradation temperatures as described above. If you heat the material to the point of bubbling or charring, PVC degradation has begun, and hydrogen chloride (HCL) fumes will occur. You do not need to burn the material to get it to melt.