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Plastic Extrusion and Molding

A wire coating line with plastic extruders

Do I need a permit for a Plastic Extrusion or Molding Process?
In most cases, you will not need to obtain an air permit for a plastic extrusion or molding process, unless criteria pollutant emissions from the entire facility exceed five (5) tons or more per year. For certain types of resins and application processes, Hazardous Air Contaminant (HAC) emissions could potentially exceed Action Levels for specific compounds.  Action Levels are pound per eight-hour emission limits established for various compounds based on their level of toxicity.  It is important to keep in mind that even if total emissions of criteria pollutants are below five tons, and an Action Level is exceeded, an Air Permit would be required.

Why do we regulate Plastic Extrusion and Molding Facilities?
Air emissions from plastic extrusion and molding often begin at the initial heating stage, where plastic pellets are subjected to increased temperatures to transform the pellets into a molten state. This process has the potential to generate volatile organic compounds (VOCs), hazardous air pollutants (HAPs), and hazardous air contaminants (HACs) that are breakdown products of the resin and vary depending on the resin formulation and temperature. Additives may also be introduced to the resins at various steps in the process to either alter the final properties of the plastic product, or to serve as a lubricant to aid in the extrusion or molding process. These additives may also contain VOCs and HAPs that can volatilize into the facility and surrounding ambient air. The Agency typically takes a conservative approach and assumes all VOCs and HAPs are emitted into the ambient air unless the applicant can demonstrate otherwise. 

In injection molding, the molten plastic material is injected into a closed mold under high pressure. Once the mold is filled, the molded parts undergoes a cooling process that solidifies the plastic. After cooling, the injection molding machine separates the mold halves, and the part is then ready for further processing, such as trimming material, coating, milling, etc. Due to the enclosed nature of an injection molding process, the air emissions from this process are low compared to other types of plastic processing.

Open molding processes such as hand lay-up, spray-up and filament winding expose the resins to the open air as they cure, which increases the amount of air pollution potential from these processes. Indoor air quality should be monitored to prevent worker exposure in facilities performing this type of molding. Styrene emissions can often result from open molding of fiberglass materials, and diisocyanate emissions can result from applying polyurethane resins and coatings. If these processes occur at your facility, please contact the Air Quality and Climate Division Engineering Services section to understand the potential risks associated with these activities.

In a plastic extrusion process, an additional emission point is the die itself, where the molten resin material is forced through a small opening at high pressure that creates shear forces and generates fine particulate matter. Extrusion machines should be operated in an area with good ventilation and fume capture, such as an elephant trunk ventilation system, to capture the harmful particulate emissions from these processes.

After the plastic material has been applied, additional off-gassing can occur as the plastic material continues to cure. If the facility stores large amounts of recently applied plastic materials prior to shipping, this must be done in an area with good ventilation to prevent worker exposure.

What do I need to do to obtain an Air Permit?
A Permit to Construct application must be submitted with the appropriate application fee to the AQCD. The Permit must be issued before the applicant can commence construction of the proposed project. Please refer to our Permit to Construct Application Guidance webpage for more information. In addition to the information required to be submitted for a Permit to Construct Application, please also submit the following equipment specifications and designs.

Equipment Specifications and Designs

Plastic Extrusion Process

  • Extruder manufacturer, trade name, model number., serial number., date of manufacture, date of installation
  • Maximum rated capacity (lb/hour), diameter of barrel, length of heated portion of extruder (ft), number of heat zones and rating (Kw)
  • Mode of quenching (water/air/none/other), mode of venting (atmosphere/vacuum - inches of water)
  • Method of feed conveyance
  • Type of product manufactured, particle size, shape, density
  • Type of material processed - manufacture, trade name, code no., amount used (lb/hr), content of free monomer (%), particle size, shape, density, MSDS sheets for all products.
  • Types of additives used (eg. plasticizer, blowing agent), manufacturer, trade name, code number, amount used (parts/100 parts resin), particle size, shape, density, percent in feed, percent in product, MSDS's.
  • Operating parameters, methods for determining how equipment will operate, determining production capabilities, factors which influence production, method of cleaning parts and equipment (e.g., sandblasting, burn-off, clean furnace, chemical removal)

State Regulations
Regardless of whether §5-501 (Permits to Construct) and/or §5-1001 (Permits to Operate) of the Vermont Air Pollution Control Regulations (Regulations)apply to your plastic extrusion or molding facility, the following Regulations may apply:

§5-211 Prohibition of Visible Air Contaminants.  This regulation restricts the visible fumes that may be emitted by the facility.

§5-241 Prohibition of Nuisance and Odor.  This regulation prevents a facility from causing a public nuisance, of either dust or odors, off their premises.

§5-253.13 Control of Volatile Organic Compounds from Coating of Miscellaneous Metal and Plastic Parts.  This regulation applies to any Miscellaneous Metal or Plastic parts coating line that whose actual emissions without control devices equals or exceed three (3) tons per rolling twelve-month period. Applicable coating lines are required to limit the Volatile Organic Compound content of the coatings or apply compliant control technology.

§5-261 Control of Hazardous Air Contaminants.  This regulation applies to any process that emits Hazardous Air Contaminants (HACs) in excess of their respective Action Level found in Appendix C of the Regulations. Facilities subject to this Regulation are required to achieve the Hazardous Most Stringent Emission Rate (HMSER) that consists of control technology, production processes or other techniques adequate to reduce the emissions of the applicable HACs. HMSER determinations are valid for a period of five (5) years, so Facilities subject to this Regulation will be classified as an Air Contaminants Source under 5-401(a)(18) and required to obtain on Operating Permit pursuant to Subchapter X.

Potentially Applicable Federal Regulations for Plastic Extrusion and Molding Processes
The following federal regulations may apply to Facilities that perform spray coatings following a plastic extrusion or molding process. For more information of coating operations, please visit our Spray Coating Operations Source Category Page.

40 CFR Part 60, Subpart TTT – Standard of Performance for Industrial Surface Coating: Surface Coating of Plastic Parts for Business Machines

40 CFR Part 63, Subpart HHHHHH – National Emissions Standards for Hazardous Air Pollutants: Paint Stripping and Miscellaneous Surface Coating Operations at Area Sources. (Major Sources are subject to Subpart MMMM, or PPPP)

What other permits or requirements may be applicable to my project?
The Department of Environmental Conservation Environmental Assistance Office provides permit assistance through the Permit Navigator tool. The Permit Navigator can help you identify what environmental permits you may need for a project on a single parcel. If you have a linear, polygon, or multi-parcel project, contact a Community Assistance Specialist to get started.