The word chemistry invokes a vision of a glass beaker with swirling liquid, but it is much more. Chemical processes are by their nature exacting; as a result, the characteristics of the dry products and the associated gas stream are usually well known, aiding in the selection of the appropriate dust collector.
special Process and Material Property Considerations
- Cross Contamination
- Combustibility and Explosivity
The plastics and resins industry is unique in the chemical industry. There are two broad classifications of plastics: thermoplastic resins produced by addition polymerization processes, and thermosetting resins made by condensation polymerization processes. Thermoplastic resins may be remolded with the addition of heat and thermosetting resins can't. The four areas of production are:
Primarily a wet process, dust control is still required on the crushing and screening as well as packaging or bulk handling.
Various compounds added to the base resin enhance the plastics properties. Examples include fiberglass for strength, glass beads for weight reduction, colorants, oxidizers, etc. Dust created when handling these compounds prior to adding them to the resins offer a need for dust collection.
Thermosetting and Molding
These processes typically do not require dust collection, though other forms of emission control may be required.
Many molded items come from the mold ready to use, requiring no additional processing. Others require grinding mold parting lines and/or blasting of the surface before they are ready for use. Many of these operations will require local exhaust ventilation systems and dust collection.
Machining and Grinding
Machining and grinding plastics offers special challenges for dust collectors because of static charge, and dust characteristics. Donaldson Torit collectors can meet those challenges. As an example, most eyeglass lenses are machined polycarbonate with each of the grinders requiring some form of dust control and Donaldson Torit has over 500 collectors installed on Polycarbonate lens grinding.
Recycling conserves raw materials and energy and lowers the cost of production. Recycling has become a major objective of many industries and the plastics industry is a leading proponent, recycling everything from computer and copier cases to water bottles. In fact, in excess of 25% of water and soda bottles are recycled and over 1,600 businesses are involved in post consumer plastic recycling in the United States.
Plastic dust is a combustible material and those operations generating or handling plastic dust can require special mitigation efforts to minimize fire and explosion risks. Standards such as NFPA 654 can provide guidance for those who generate and handle these types of dusts. See the Donaldson Torit Dust Collectors and Combustible Dust Strategies brochure.
- Static Charge Dissipation
Plastic production, machining, and material handling can all lead to the development of a static charge on the plastic dust particles. These charges can lead to severe complications in any dust collection system unless addressed with proper bonding and grounding practices and procedures. Standards such as NFPA 77 can provide guidance for those who generate and handle these types of dusts.
- Material Discharge Equipment
Plastic production and material handling often involves large volumes of materials that nest and agglomerate at transfer points. Special consideration for dust discharge can be a critical factor in proper duct collector operation for many of these types of dusts.
- Worker Productivity and Morale
A dust-free manufacturing environment leads to greater productivity and accuracy, and contributes to worker satisfaction.
- Reclaim Value
Many plastic dusts, in sufficient production quantities, have intrinsic resale value in a secondary market.
LEGISLATION (OTHER FEDERAL AND LOCAL LEGISLATION MAY APPLY)
Particulate Matter (PM):
- PM 2.5 = 15 µg/m3 (annual), and 35 µg/m3 (24-hour)
- PM 10 = 150 µg/m3 (24-hour)
- National Emissions Standards for Hazardous Air Pollutants includes topics on Flexible Polyurethane Foam Fabrication Operations, Reinforced Plastic Composites Production, and Rubber Tire Manufacturing
- 29 CFR 1910.1000 - Air Contaminants
NOTE: Twenty-five states, Puerto Rico and the Virgin Islands have OSHA-approved State Plans and have adopted their own standards and enforcement policies. For the most part, these States adopt standards that are identical to Federal OSHA. However, some States have adopted different standards applicable to this industry or may have different enforcement policies.
Industrial Ventilation Manual
NIOSH Publication No. 76-179