One of the most destructive and expensive mistakes in plumbing and piping is choosing the wrong type of sealant for the material. This is particularly true when dealing with plastic fittings like ABS, PVC, or CPVC.

If you’ve ever seen a plastic fitting suddenly crack or split after assembly, the sealant itself may be the culprit. This failure is usually due to a chemical reaction called Stress Cracking or a material mismatch that causes mechanical damage.

The Plastic Problem: Stress Cracking

Many sealant pastes, “pipe dopes,” and even certain industrial-grade anaerobic liquids contain solvents, carriers, or oilsthat are chemically incompatible with common thermoplastics (plastics).

When these incompatible chemicals come into contact with a plastic thread that is already under tensile stress (from being tightened), the chemical causes the plastic polymer structure to break down locally. The result is:

• Sudden Cracking: The fitting may crack or split hours, days, or weeks after assembly, leading to a catastrophic leak.
• Loss of Integrity: The plastic loses its strength, making it vulnerable to failure from pressure or system vibration.

The Danger of Misapplied Anaerobics (Metal Sealants)

Anaerobic thread sealants, including the entire Incure ProGrip™ series, are high-performance adhesives designed onlyfor metal-to-metal connections.

• Anaerobics Do Not Cure on Plastic: These products cure when air is excluded AND in the presence of active metal ions (like iron or copper). They simply will not cure on plastic fittings.
• Risk of Stress Cracking: Furthermore, the resins and activators in some anaerobic formulas may cause stress-cracking in certain sensitive polymers (plastics). Therefore, the golden rule is: NEVER use anaerobic thread sealants on plastic threads.

The Danger of PTFE Tape on Plastic

Even seemingly harmless PTFE (Teflon) tape can lead to failure on plastic fittings:

• Over-Tightening: PTFE tape acts as an excellent lubricant. When used on plastic threads, it makes it far too easy to over-tighten the joint, placing excessive tensile stress on the female fitting and causing it to split or crack.
• Wedging Action: Wrapping too much tape creates a wedging action that physically strains the plastic threads,which are much more brittle than metal threads.

The Best Choice for Metal Systems: Incure ProGrip™ 201

Since anaerobic sealants are only for metal, we recommend a product from the list that is built for reliability in metal systems where system integrity is paramount: Incure ProGrip™ 201 Hydraulic & Pneumatic Thread Sealant.

Why ProGrip™ 201 is the Go-To for Metal:

• Contaminant-Free: ProGrip™ 201 is specially formulated to be non-contaminating and filler-free. It contains no PTFE or particles that could break off and clog sensitive components like pneumatic solenoid valves or hydraulic filters.
  
• Low Strength (Easy Service): As a low-strength sealant, it provides a secure, pressure-tight seal that is easily disassembled with standard hand tools, making it perfect for frequently serviced equipment in hydraulic and pneumatic lines.
  
• Fills All Voids: It cures into a resilient plastic that seals threads up to M36 against high pressure (up to 69 MPa or 10,000 psi), ensuring no leaks, which is critical for maintaining efficiency in air and fluid power systems.

For metal systems, ProGrip™ 201 ensures a clean, reliable, and easily serviceable seal.

A Critical Note on Plastic Fittings

For sealing ABS, PVC, or CPVC threads, you must use a specialized, plastic-compatible sealant.

• Look for Certification: Only use sealants certified by the plastic pipe manufacturer or explicitly labeled as safe for the specific plastic (e.g., “Safe for PVC and CPVC”). These products are non-hardening and free of the specific solvents that cause stress cracking.
  
• Technique is Key: Regardless of the product, always finger-tighten the plastic joint, and then add no more than one to one-and-a-half additional turns to prevent over-tightening and cracking.