Matching imported PPF TPU: the four numbers that decide it
Domestic substitution in paint protection film is not a price argument — it is a colour-shift argument. Four measurements decide whether an aliphatic TPU actually replaces an imported grade: QUV colour shift, tear strength, process stability and adhesive compatibility.
What a film converter is really being asked
A PPF converter qualifying a new TPU is not comparing datasheets. They are answering one question: if I run this material on my line for a month and put the film on a car in Guangzhou, will the customer see a difference in two years.
That reframes the specification. Optical clarity and self-healing get the attention, but the qualification usually turns on weathering colour shift, handling toughness, and whether the extruder can hold gauge on an unfamiliar melt.
One: colour shift after accelerated weathering
The measurement that matters is ΔE* after QUV-A exposure — 340 nm lamps at 0.75 W/m² for 1000 hours, which is the conventional screen for automotive exterior film.
Below about 1.5, the shift is below the threshold most observers can see. Both PPF grades sit under that line, which is the whole point of using an aliphatic polycarbonate rather than an aromatic TPU: aromatic hard segments generate chromophores under UV, and no amount of stabiliser package fully stops the yellowing that follows.
| Grade | Hardness | Tensile strength | Elongation | Tear strength | ΔE* (QUV-A 1000 h) |
|---|---|---|---|---|---|
| NL2193 | 90A | 62 MPa | 410% | 80 kN/m | 1.10 |
| NL2188 | 88A | 60 MPa | 420% | 90 kN/m | 1.23 |
| NL2165D | 65D | Ask for TDS | Ask for TDS | Ask for TDS | Self-healing top layer |
Two: the trade between colour and toughness
NL2193 and NL2188 are the same chemistry at adjacent hardness, and the difference between them is instructive. NL2193 gives the lower colour shift, 1.10 against 1.23. NL2188 gives higher tear strength, 90 kN/m against 80.
In practice that is the choice between a film that stays invisible longest and a film that survives installation and handling with fewer defects. High-volume installers tend to value the tear number, because a film that tears during stretch costs more than a ΔE* difference nobody can see.
Three: process stability on the line
PPF is a co-extruded or cast multi-layer construction, and the TPU layer has to hold gauge while running thin. Consistent melt behaviour is what keeps the extruder controllable — the failure mode with an unstable melt is not a bad datasheet number, it is gauge drift that shows up as optical distortion in the finished film.
This is also why the top layer is often specified separately. NL2165D is positioned as a 65D self-healing top layer for multi-layer co-extrusion, where the requirement is surface recovery and stain resistance rather than bulk toughness. Physical data for it is not published — ask for the TDS before quoting a construction.
Four: compatibility with everything above and below
The TPU is one layer in a stack: clear coat above, adhesive below, sometimes ink in between. A grade that performs beautifully alone but does not bond to the adhesive system is not a candidate.
Adhesion, ink acceptance and coating compatibility therefore belong in the qualification plan from the first trial, not after the optical checks pass.
A practical qualification sequence
- Confirm the chemistry basis (aliphatic polycarbonate) and ask for the QUV report, not just the ΔE* figure.
- Run a gauge-stability trial on the actual line before judging optical quality.
- Laminate with the intended adhesive and clear coat, then re-measure haze and colour — the stack can shift what the single film measured.
- Run a handling trial at production stretch levels to find the tear limit in practice.
- Only then compare against the imported incumbent on cost per square metre of saleable film, not cost per kilogram.