I have been invited to carry out an occupation exposure assessment in a large manufacturing building. My customer was carrying out a variety of processes some of which represented a significant exposure and health risk to his employees. In this project I have assess the operatives exposure to oil mist from metal working operation, microbiological exposure from bacteria residing in the cooling liquids, soldering fumes and injection moulding plastic fumes.
In this article I would like to focus on the topic of the injection moulding plastic fumes and potentially hazardous contaminates that can be release from this process.
But first I will give you some background information about the place so you understand the setting. My client has a factory in the Manchester area and specialises in production of safety valves for the oil and gas industry. The factory consists of main metal component production area, central stores, assembly area, and metal working area coils area. They have a large number of working machines which use mainly water based coolants. Small proportion of metal working machines was using oil based coolants. There were approximately 30 employees working in the main production area likely to be exposed to oil and water aerosol from the metal working machines and potentially bacterial pathogens.
There was also a relatively small section in the factory housing two plastic moulding machines and three soldering stations. All stations were equipped with dedicated local exhaust ventilation system. There were about 6 employees working in this area and they were all likely to be exposed to solder flux fumes and injection moulding plastic fumes.
There are two main categories of plastic materials which are used in injection moulding processes. The first group is call thermoset materials which when cured set into hard object that cannot be reshaped or softened by heat. Other group of materials are thermoplastic materials which can be reheated and reshaped if necessary. The thermoplastic materials use a variety of resigns such as Polyethylene , Polyvinyl Chloride, Polypropylene, Polystyrene, Polyethlene Terephthalate, Acrylonitrile-butadiene-styrene, Styrene-Acrylonitrile, Acrylic, Polyamide, Styrene-Acrylonitrile, Polycarbonate.
The base material is usually delivered into the injection moulding system in the form of pellets, granules or powder. It is rapidly melted and various additives are added depending on specific requirements. Under normal operation and when using modern machinery the release of fumes is very small. The majority of uncontrolled release happens during short periods of time during system purging, cleaning or maintenance.
Depending on the base materials and additives the released fumes will contain decomposition product of the base material, possibly combustion products and vapours from different constitutes. The most common constitutes of the injection moulding fumes are hydrogen chloride, Styrene, Phenols, Butadiene, Acrolein, Acetone, Formaldehyde and other aldehyde and butane.