Plastic Manufacturing & FRP Dust Collection

• Conveying/moving/transporting: Moving and conveying plastic parts—and especially the pellets used for thermosetting and molding—results in large volumes of dust and fines created when plastic pieces bump against each other and against conveyor systems.
• Resin crushing/screening/packaging: Resins used in plastic production also create dust when moved, crushed or ground while in solid form.
• Machining, cutting and grinding: Machining and grinding, including grinding of polycarbonate lenses, produces a significant amount of fine plastic dust with a high static charge.
• Parts cleaning: Some molded parts will require abrasive cleaning or grinding to remove rough edges.
• Plastic recycling: Plastic recycling involves moving and sorting large amounts of plastic material, grinding the material to powder, and then melting and reforming the plastic into new pellets. Many of these steps produce plastic dust.
• Vibratory finishing: In vibratory finishing methods, the part to be cleaned or finished is placed in a specialized tumbler along with an abrasive medium. The tumbling action rubs the abrasive grit against the part until the desired finish is achieved. It is typically used to deburr, de-scale, burnish, clean, polish or brighten smaller components. Vibratory finishing works especially well for small parts that are oddly shaped or contain internal features (e.g., grooves and holes) that must be deburred and polished.

Common plastic dust types include:

• Acrylic (PMMA)
• Acrylonitrile Butadiene Styrene (ABS)
• Delrin/Acetal
• Nylon
• Polycarbonate
• Polyethylene Terephthalate (PET/PETE)

• Static charge: The primary difference between plastic dust and most other types of dust is that plastic dust carries an electrostatic charge. As microplastics and fines rub against each other in the airstream, they produce static electricity. Each plastic particle becomes slightly charged. The charged particles of plastic are attracted to the filter media, which makes them difficult to pulse off and leads to excessive filter loading. Static charge also creates a risk of sparks, which can lead to self-ignition of a combustible dust explosion.
• Combustion risk: Plastic dusts are highly combustible. That means they can generate an explosion when allowed to concentrate in the air or inside a dust collection machine. Special care must be taken when collecting combustible dusts to minimize the risks of an explosion inside the dust collector. Plastic dusts are especially dangerous because of their potential for self-ignition due to their static charge. When plastic dust builds up inside conveyor systems or other enclosed spaces, the combination of static electricity and confined combustible dust can be deadly.
• Health risks: Particulates created by plastics and FRPs present a danger to human health. Inhaled microplastics and fibers from FRPs can cause nose, throat and lung irritation and lead to coughing or choking. Very fine particles that are inhaled deep into the lungs have been associated with asthma, COPD, and other lung diseases. Microfibers in FRPs can be especially problematic because they can become entrapped by lung tissue when inhaled and are not easily expelled or broken down by the body. The effects of inhaling some types of fibers from FRPs may be similar to that of asbestos. Some types of plastic dust, particularly PVC, are associated with lung cancer. Many plastics or plastic additives (such as BPA) are also endocrine imitators, which may cause problems with hormonal systems. More research is still needed to determine the exact health risks of different types and levels of plastic and FRP dust exposure, but manufacturers should take precautions to reduce exposure as much as possible.
• Product contamination: In many manufacturing environments it is important to prevent plastic dust from migrating to other parts of the production line to avoid contamination and quality control problems.
• Nuisance dust: Uncontrolled dust of any type is also a housekeeping consideration. Plastic dusts can accumulate on floors and other surfaces, creating a slip-and-fall hazard.

• Combustible dusts: Combustion risk is common to all types of plastic and FRP dust. Combustible dusts are regulated under OSHA’s General Duty Clause (Section 5(a)(1)) with additional requirements under the Hazardous Locations (§1910.307), Hazard Communication (§1910.1200) and Housekeeping (§1910.22) standards. In addition, manufacturers dealing with combustible dusts must follow National Fire Protection Association (NFPA) standards for prevention of fires and explosions. Plastic and FRP dust falls under NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing and Handling of Combustible Particulate Solids. OSHA’s Combustible Dust National Emphasis Program (NEP) outlines policies and procedures for inspecting workplaces that create or handle combustible dusts.
• Nuisance dusts: Many plastic dusts fall under the OSHA definition of “nuisance dusts,” which are regulated under the general particulate matter concentration limit. The general limit for “Particulates Not Otherwise Regulated” (PNOLs) is 15 mg/m³ (8-hour TWA limit) for total particulate and 5 mg/m³ for respirable particulates. Employers must also follow general Housekeeping standards (OSHA 1910.22, Walking-Working Surfaces) to prevent accumulation of dust on surfaces.
• FRP dust: OSHA regulates synthetic mineral fibers used in FRPs (including fiberglass, mineral wool and refractory ceramic fibers) under the general “Inert or Nuisance Dust” standard. However, due to the health concerns related to breathing in mineral fibers, OSHA established a voluntary limit with industry associations in 1999. This limit, which is supported by the National Academy of Sciences, is one breathable glass fiber per cubic centimeter of air over an 8-hour shift.
• Hazardous dusts: OSHA has set specific exposure limits for certain hazardous substances found in some plastics, such as styrene, heavy metals and vinyl chloride. These are expressed as Permissible Exposure Limits (PELs), which are measured and averaged over a worker’s 8-hour shift and specific to each toxic substance present in the dust. Manufacturers are responsible for ensuring that workers are not exposed to hazardous dusts in levels above the PELs. Failure to control dust in areas where workers may be exposed can result in serious fines and legal action.
• Environmental regulations: Some of the substances used in plastic production are also subject to Environmental Protection Agency (EPA) regulation, which may impact how toxic plastic dusts are disposed of.

Relevant considerations in dust collection system design for plastics and FRPs include:

• Explosion mitigation: Combustible dusts such as plastic and FRP dust require a deflagration system to reduce the chances of an explosion inside the dust collector and mitigate damage to the facility if an explosion should occur. These systems may include an explosion vent to release built-up pressure in the collector, an isolation valve to prevent pressure waves from propagating back into the facility, and a rotary airlock to keep collected dust safely contained in the hopper.
• Fire suppression: The dust collector should be equipped with an internal fire suppression system for added protection against fires.
• Filters: A static-reducing filter media should be used to reduce the risk of self-ignition inside the dust collector and reduce clinging to the media. If plastics become heated during machining or grinding, molten plastic can accumulate on filters, causing them to cake and leading to early failure. A longer ductwork run can reduce these problems. Thermal processes such as melting and compounding will require different solutions for control of dust, odors and VOCs. If you are using thermal processes, contact us for more information.
• Filter Pulsing: In addition to choosing the right filter media, it is important to have an effective filter pulsing system to pulse off plastic dust clinging to the filters. A robust pulsing system combined with static-reducing filter media will extend the life of the filters.