Hydraulic‑fracturing tools live in a punishing world. Your frac plugs see 10 000 psi, 225 °F (107 °C), heavy compressive loads, and a 0.20‑inch extrusion gap—all for hours on end. Fail the seal and the entire stage fails with it.
The good news: you don’t need a gold‑plated recipe to survive. You need a smarter one. Below is a step‑by‑step look at how to reach that sweet spot of performance and price—plus two quick‑reference tables you can take straight to your compounder (or skip the trial‑and‑error and call us for an off‑the‑shelf solution).
| Challenge | What the compound must resist |
|---|---|
| 10 000 psi pressure | Extrusion and mechanical tear |
| 60 000 lb compressive load | Permanent set and stress cracking |
| 225 °F for ≥ 2.5 h | Thermal softening and oxidation |
| 0.20‑in extrusion gap | Nibbling and seal blow‑by |
| Shorter element length | Less rubber, more efficiency |
These forces set the bar for every formulation lever you pull next.
Base Polymer – Medium‑to‑high ACN NBR (36‑45 %) for hot tensile; sprinkle in XNBR (≤ 10 phr) if tear strength is a concern.
Cross‑Link System – EV/SEV sulfur for low reversion, or a peroxide/co‑agent package when ultra‑low compression set is non‑negotiable.
Cross‑Link Density – Target ≈ 3 × 10⁻⁵ mol g⁻¹ to hit 80‑90 Shore A without turning the element into a rock.
Filler Package – Blend reinforcing N330 with process‑friendly N550; add N990 in extrusion zones to dampen stress peaks.
Additives – Silica micro‑dose for tear, TMQ + 6PPD for heat aging, high‑temp‑stable plasticizer only if you must.
Processing Aids – A single low‑fog wax bead (≈ 1 phr) keeps viscosity in check and shortens mold cycles.
| Formulation Lever | Typical Targets | Why It Counts |
|---|---|---|
| Base Polymer | NBR 36–45 % ACN Mooney 70–85 ML(1 + 4) @ 100 °C + ≤ 10 phr XNBR | Heat strength; XNBR bonds to filler for tear resistance |
| Cross‑Link System | EV/SEV sulfur (S 0.5–0.8 phr, CBS 0.7, TMTD 0.1) or DCP 1.2 phr + TMPTMA 3 phr | Sulfur = cost‑efficient; peroxide = best for compression set |
| Filler Blend | N330 25 phr + N550 30 phr Optional N990 5 phr | Balances modulus and viscosity; protects against extrusion |
| Secondary Fillers | Silica 3 phr + TESPT 1 phr | Hybrid network lifts hot tear, curbs die‑swell |
| Antidegradants | TMQ 1 phr + 6PPD 1 phr | Guards against thermo‑oxidative aging |
| Misc. | ZnO 5 phr + stearic 1 phr Wax‑coated PE 1 phr | Cure activation; smoother mold flow |
Use this table as a talking sheet with your compounder to make sure you’re pulling the right chemical levers.
| Smart Move | Why It Saves |
|---|---|
| Medium ACN vs. ultra‑high ACN | +10 % ACN can add > 25 % to polymer cost; heat spec doesn’t need it. |
| Dual carbon‑black system | N550 is ~40 % cheaper than N330; modulus loss fixed with a touch of XNBR. |
| EV sulfur vs. full peroxide | Sulfur cure is ≈ ⅓ the cost; reserve peroxide for < 15 % compression‑set specs. |
| Silica micro‑dose | 3 phr gives +20 % tear for pennies—no expensive nano‑fills required. |
| Lean process aid | 1 phr wax costs ~$0.05/kg and can cut cycle time by 10 %. |
| Property | Spec | How We Hit It |
|---|---|---|
| Shore A Hardness | 80–90 | Cross‑link density + 55 phr filler |
| 100 % Modulus | ≥ 8 MPa | High‑surface black, XNBR bonding |
| Tensile Strength | ≥ 18 MPa | Balanced filler + EV cure |
| Compression Set (22 h @ 225 °F) | ≤ 18 % | Low‑sulfur EV or peroxide system |
| Extrusion Test (0.20 in gap @ 10 k psi) | No nibbling/tear | FEA‑driven durometer gradient |
| Aging ΔHardness (70 h @ 225 °F) | +≤ 5 pts | TMQ + 6PPD package |
We’ve already blended, molded, and pressure‑tested compounds that meet every spec above. If you want to shortcut the trial‑and‑error, or just need a second opinion- let’s talk.
Click on the link below to book a 15‑minute consult or request a price on our in‑stock compounds.