For many years the processing of polyurethane systems to manufacture a wide range of products has been routine practice. Experience has shown that, if the safety rules are followed, this processing can be conducted without risk or adverse effects. Those injuries and accidents which still occur are nearly always caused by ignorance or carelessness.
It is therefore important that everyone employed in the plant be fully informed about precautionary measures, be instructed in the use of safety equipment, and be repeatedly motivated to use them.
Polyurethane Systems generally consist of 2 components – the polyol and the isocyanate. In the USA and some other countries (Italy for instance), the isocyanate is designated as the A-Component – whereas in other countries the Polyol is designated as the A-Component. In order to avoid any confusion we should always refer to the components as polyol and isocyanate rather than A and B-Component or any other designation.
Besides the Polyol and Isocyanate there are also additives such as catalysts, blowing agents, surfactants, flame retardants, pigments and fillers which are generally contained in the polyol component.
The handling of the polyol component involves relatively little hazard. Splashes of material on the skin can be easily washed off with soap and water. Organic solvents such as acetone or methylene chloride should not be used for cleaning, as they can damage the skin.
Polyol blends generally contain tertiary amines as catalysts. These strongly basic substances irritate sensitive areas of the skin, even in a diluted form. They can, on longer exposure, cause inflammation of the cornea of the eye. Several of this type of amine are corrosive. Protective gloves and goggles should always be worn when working with polyol blends. Splashes of the material coming into contact with the eyes, should be rinsed out immediately using large volumes of fresh water. This irrigation should be sustained, but even more important is treatment without delay.
Effective ventilation is always recommended because of the odour caused by some of the catalysts contained in the polyol blend. This odour is often distasteful but not normally dangerous to health at the concentration normally encountered.
When containers containing polyol blend with a volatile blowing agent have been standing in the sun, a build up of pressure can occur. This could present a hazard if the container is opened while under pressure. Polyol leaks or spills should be taken up using a suitable adsorbent material such as sawdust or dry sand and then disposed of safely. Surfaces wetted with polyol present a skidding hazard similar to an oil spill. Small amounts of polyol can be removed with common household detergents and warm water. Since polyols are not readily biodegradable, they should not be permitted to enter the ground water, drainage systems or the soil.
Some polyol blends can cause corrosion in storage tanks and such containers should be inspected regularly.
The Flash Points for polyols are usually in excess of 100 C, meaning that they do not present any special flammability risk, and are not subject to regulations concerning flammable liquids. Where polyol blends contain flammable hydrocarbons such as pentane as the blowing agent, Flash Points less than 21 C are possible. In such cases the polyol blends fall into different flammability hazard classifications which must be taken into consideration without fail during storage and processing.
In a fire involving polyols, the usual extinguishing agents such as water spray, foam, carbon dioxide or chemical powder can be used.
The isocyanates used in Polyurethane systems consist essentially of highly reactive diisocyanates or diisocyanate preparations. The primary safety consideration concerns the inhaling of isocyanate vapours or aerosols (sprayed mists).
Aptane Polyurethane systems are generally based on MDI (diphenylmethane diisocyanate) which has a low volatility at room temperature so that a hazardous vapour concentration will not be reached. Normal room ventilation is recommended with 6 – 8 air changes per hour recommended for industrial working areas. When working with MDI at elevated temperatures or in spray applications or during the air flushing of mixing heads, controlled air extraction or a respiratory mask is essential.
Aptane Polyurethane systems never contain TDI (toluylene diisocyanate), which requires special precautionary measures. Because of it’s vapour pressure, a TDI spillage can quickly lead to a concentration of isocyanate fumes in the air at which damage to health can be expected. When the characteristic acrid almondy smell of TDI is noticeable, the maximum permissable concentration has already been exceeded. When working with TDI intensive air extraction is essential, and it is recommended that work areas are continuously monitored with commercial vapour detection devices. Isocyanate vapours irritate the mucous membranes of the nose, throat and lungs. They can lead to dryness of the throat and pressure on the chest, often combined with breathing difficulties and headaches. Often the effects appear some hours after the exposure. Should violent coughing or asthmatic symptoms occur, immediate medical treatment should be sought. Minor discomforts normally disappear after extended exposure to fresh air. The repeated exposure to TDI vapours above the permissable level can lead to the development of allergic reactions. Persons who have a tendency to illnesses of the respiratory tract or are sensitive to environmental influences should not work in the vicinity of the foaming operation. The precautionary medical examination for new hires should include a lung function test.