Molders

Molders were the production-floor workers who operated compression molding presses to produce thermoset plastic parts from phenolic compound. Through the 1930s–1970s asbestos era, the compound they handled was asbestos-filled in nearly all electrical, defense, and high-performance applications.

What the job involved

The typical molder workday included:

  1. Loading compound — picking up bags of asbestos-filled phenolic compound granules and pouring them into press hoppers or directly into mold cavities. Each pour generated airborne fiber from the granule disturbance.
  2. Pre-heating — for many compounds, the granules were preheated before loading. Preheating sometimes released volatiles and fiber.
  3. Cycling the press — closing the press, applying heat (typically 300-350°F) and pressure (typically 1,000-2,000 psi), curing the resin, opening the press.
  4. Removing the part — sometimes still hot, with flash (excess material) attached.
  5. Cleaning between cycles — wiping mold faces, removing residue. Compressed-air cleaning was common and aerosolized fiber.

A single press operator might run 50-200 cycles per shift, with each cycle generating compound handling and finished-part removal exposures.

Exposure intensity

NIOSH measurements at phenolic molding operations documented 8-hour TWA exposures from 0.006 to 0.08 fibers/cm³, with peak short-term concentrations substantially higher during specific tasks. Some operations were documented at fiber concentrations more than 140 times the then-current exposure limit (notably some Rogers Corporation operations).

Plants where molders worked

Molders were employed throughout the asbestos era at:

  • Compound manufacturer captive operations — UCC Bound Brook NJ, Monsanto St. Louis MO, Durez North Tonawanda NY, Plenco Sheboygan WI, GE Pittsfield MA
  • Independent molding shops nationwide — including Koller Craft (Fenton, MO), Carter Carburetor (St. Louis, MO), Reichhold Chemicals (Valley Park, MO and Morris, IL), Resinoid Engineering (IL), Rostone Corporation (Lafayette, IN), Belden Manufacturing (Richmond, IN), Motor Wheel (Lansing, MI), Allen-Bradley (Milwaukee, WI), and hundreds of others.
  • Defense / aerospace contractors — producing components meeting MIL-M-14 specification

Trade unions

Molders were sometimes organized through industrial unions (UAW, IUE, Teamsters, IAM) depending on the plant. Union pay records and pension data may help establish employment history for case evaluation. Non-union molding shops are also well-documented in public records.

Latency and case timing

Mesothelioma latency from initial asbestos exposure is typically 20-50 years. Molders who worked during the 1950s-1970s asbestos era may be presenting with mesothelioma now in 2020s-2030s. Statutes of limitation begin running from the date of diagnosis, not the date of exposure.

If you (or a family member) worked this occupation

Free, confidential case evaluation: Speak with O’Brien Law Firm — (314) 936-2956

Most workers in these occupations did not know that the “plastic” they handled contained asbestos. The compound manufacturers and downstream molding shops are documented in publicly filed litigation. Trust-fund claims and civil lawsuits can both be pursued — see the Trust Funds page for the compensation pathways.

References to manufacturers, products, and exposure intensities reflect what has been alleged or documented in publicly filed asbestos litigation, NIOSH and OSHA measurements, and industry archives.