Why this page exists. Most thermoplastic prepreg enquiries we receive are not about fibre or areal weight — they are about the processing window. A buyer has a press, a mould and a target cycle time, and needs to know what temperature and pressure will consolidate the laminate without degrading the polymer. Get this wrong and the failure is expensive: an under-consolidated panel delaminates in service, an overheated one loses molecular weight and turns brittle. This page sets out the window for each resin system we supply, and explains why the window is narrower than most people expect.
The structural difference: melting, not curing
Thermoset prepreg works by chemical crosslinking. You heat it, the resin cures irreversibly, and after that the part is what it is. Thermoplastic prepreg works by melting and re-solidifying — a physical process with no chemical bond forming. Three consequences follow, and they drive everything else on this page:
- The cycle is fast. Consolidation takes minutes, not the hours an autoclave cure needs — this is where the cost advantage at volume comes from.
- The part can be re-melted. This enables welding, thermoforming, repair and end-of-life recycling. It also means an overheated part cannot be rescued: you have degraded the polymer, not just “over-cured” it.
- The window is set by melt viscosity, not by cure kinetics. You need the polymer hot enough to flow and wet the fibre, but not so hot or so long that it oxidises or chain-scissions.
Processing window by resin system
The table below covers the systems we supply. Values are typical starting points for press consolidation, not acceptance criteria — every grade carries its own datasheet, and the correct window depends on fibre content, ply thickness, part geometry and press capability.
| 树脂 | Tg (°C) | Tm (°C) | Typical melt / processing temperature | Continuous service | Notes on the window |
|---|---|---|---|---|---|
| PP | −10 | 165 | 200–230 | 80–100 | Widest and most forgiving window. Lowest cost entry point for volume parts. |
| PA6 | 55–70 | 220 | 240–280 | 100–130 | Moisture-sensitive: dry before processing or you get voids and hydrolysis. |
| PA12 | ~40–50 | 178 | 200–240 | 90–110 | Low moisture uptake, dimensionally stable — common in tube and profile. |
| PC | 145 | 225 (amorphous) | 280–320 | 115–125 | Amorphous, so Tg governs stiffness above ~145 °C. A common error is to run PC at PP temperatures — it will not wet out. Also stress-cracking sensitive to some solvents. |
| PEI | 217 | amorphous | 320–360 | 170–180 | FST-compliant by nature; aerospace interior workhorse. Needs high press temperature. |
| PPS | 85–90 | 285 | 300–340 | 200–240 | Chemically inert, UL94 V-0. Very high melt viscosity — impregnation is hard, so tape quality matters more than for PP. |
| PEEK | 143 | 343 | 370–400 | 250–260 | Highest performance and highest temperature. Narrow window: below ~370 °C it will not consolidate, above ~400 °C it degrades. |
Read this table as a floor and a ceiling, not a target. Running at the bottom of the window gives you longer flow time and better wet-out but risks incomplete consolidation. Running at the top gives faster cycles but shortens the polymer’s thermal history budget.
Three parameters, one trade-off
Consolidation quality is set by the interaction of temperature, pressure and time — you cannot optimise one in isolation.
Temperature controls melt viscosity. Lower viscosity means better fibre wet-out and easier flow into corners, but every polymer has a thermal history limit: hold PEEK at 400 °C for an hour and you will lose mechanical properties even though nothing looks wrong.
Pressure drives out entrapped air and closes voids. Typical press consolidation sits in the range of a few bar to tens of bar depending on part thickness and resin viscosity. Too little pressure leaves porosity; too much can squeeze resin out of the laminate and cause fibre wash or resin-starved edges.
Time is the variable most often got wrong. Heat-up time is usually the dominant part of the cycle, not the hold. A thick laminate needs a slower ramp so the core reaches melt temperature before you start counting hold time — otherwise you consolidate the surface and leave the centre dry.
Practical check: if you are increasing hold time to fix porosity, you are usually treating the wrong variable. Check heat-up rate and pressure first.
The four failure modes and what they look like
| Symptom | Most likely cause | What to check |
|---|---|---|
| Porosity / white patches | Insufficient pressure, or moisture in the resin (especially PA6) | Pressure profile; dry the prepreg; check vacuum if used |
| 层间分层 | Hold time too short, or temperature never reached the core | Thermocouple in the laminate centre, not at the surface |
| Resin-rich edges, dry centre | Excessive pressure squeezing resin outward, or uneven mould temperature | Reduce pressure; check mould temperature uniformity |
| Brittle part, discolouration | Thermal degradation — too hot or too long | Cut the ramp/hold; verify actual melt temperature with a thermocouple rather than the press setpoint |
The last one is worth emphasising: the press setpoint is not the laminate temperature. Mould mass, insulation and part thickness all create a lag. Any window you develop should be validated with a thermocouple inside the laminate, not read off the controller.
How to establish your own window
A datasheet gives you a starting point; your part gives you the answer. The sequence that works:
- Confirm the melt behaviour — DSC on the actual grade gives you Tm and, for semi-crystalline systems, the crystallinity window. For amorphous systems (PC, PEI) the Tg is the governing number.
- Find the minimum consolidation temperature by pressing small plaques at increasing temperature with fixed pressure and time, then checking void content by microscopy or density.
- Fix temperature, then vary pressure to find where porosity stops dropping. That is your minimum workable pressure.
- Then shorten the hold time until you see delamination, and add margin back. Cycle time reduction is where the money is, but only after consolidation is proven.
- Validate on the real part geometry, not a flat plaque. Corners, thickness transitions and inserts all behave differently.
This is a few days of work for a new material, and it pays back immediately in scrap rate.
Choosing between systems: a decision sequence
The processing window is usually the second question, not the first. The order that avoids expensive mistakes:
- Service temperature first. If the part runs above 120 °C continuously, PP and PA are out; go to PPS or PEEK.
- Chemical exposure second. Solvents and aggressive fluids narrow the choice quickly — PPS and PEEK are the chemically inert options.
- Cycle time and volume third. If you need 30–60 second cycles, PP and PA6 are the practical answers; PEEK’s window does not permit that speed.
- Recyclability last, but decide it early. All thermoplastic systems are re-meltable, but the recycling route and the value of the recyclate differ by system.
What we supply
We impregnate thermoplastic prepreg on our production lines in PP, PC, PA, PEI, PETG, PET, PPS, PEEK and PAEK systems, supplied as UD tape, prepreg roll or woven prepreg. Fibre content, areal weight and width are set to your specification within our production capability.
If you are developing a process window, tell us the resin system, the part thickness and the cycle time you are targeting, and we will confirm what we can supply and which grade suits the press you have. A datasheet for the wrong grade is worse than no datasheet — we would rather work through the application with you first.
- Thermoplastic Prepregs — product range and resin systems
- How to Choose the Right Prepreg — thermoset vs thermoplastic
- Continuous Fiber Thermoplastic Composites (CFRT) — production process
- Request a quote or a sample
Processing temperatures on this page are typical industry starting points for the resin systems named, not acceptance criteria for any specific grade. Actual windows depend on fibre content, ply thickness, part geometry and press capability, and must be validated on your own tooling. Specific batches are governed by the accompanying datasheet / COA.