Aliphatic TPU Film

Aliphatic TPU Film, Non-Yellowing Grades, and How to Verify the Claim

Aliphatic TPU film is a thermoplastic polyurethane film based on straight-chain isocyanates and has therefore no aromatic rings that would cause the plain polyurethane film to yellow when exposed to UV light. Every supplier knows how to sell you this. What very few know is that ‘aliphatic’ really only covers one layer of your laminate and one pathway to degradation. And that a yellow finished part is no proof of yellow film.

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Solution summary

What it is

optically clear aliphatic polyurethane film, extruded to customer specification for lamination, surface protection and glazing.

What it solves

The quinone-imide yellowing pathway aromatic TPU can’t evade.

What it doesn’t solve

topcoat degradation, adhesive discolouration and soft segment hydrolysis.

How you verify it

The four gates, below. All of them work on all suppliers, including ours.

What we haven’t published

Our own accelerated ageing results. We tell you. Plainly, rather than implying otherwise.

ISO 4892-2 Protocol

Why Aromatic TPU Film Yellows, and the Part Aliphatic Chemistry Does Not Fix

A converter applies a clear film over a white object. The object takes on a warm cast after 18 months. The owner photographs it and calls us to discuss warranty terms. On detailing forums, the discussion is predictable, often devolving to finger-pointing between the film supplier and the substrate manufacturer, with no resolution. In a popular thread about a yellowing car wrap, the highest-rated response actually had nothing to do with the wrap, and everything to do with the part beneath: “My bumper yellowed not the wrap.”

The Chemistry of Photo-Oxidation

Below that argument, the chemistry is solid, and we report it exactly because it’s only by precisely defining the terms of the problem that the rest of this page is made useful. Polyurethane is a block copolymer. It has a hard segment and a soft segment. If the isocyanate forming the hard segment is aromatic (from the diphenylmethane and toluene family used for standard TPU) then it absorbs UV light directly in its benzene ring.

That urethane bridge then becomes oxidised to a quinone-imide which absorbs light in the blue region of the spectrum, creating yellow. This mechanism, detailed by Rosu and his colleagues in Polymer Degradation and Stability, has been referenced several hundred times; the accelerated xenon-arc exposure that reproduces this photo-oxidation is standardised as ISO 4892-2.

Aliphatic isocyanates (isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate, the two most common in the market) contain no such ring and thus can’t absorb photons. There’s no ring to become oxidised, there’s no quinone-imide to form, there’s no colour to the material. Colour stability of aliphatic urethane materials isn’t the result of an additive or formulation trick; it’s an absence.

Laminate Complexity & Discolouration

Here’s where industry knowledge stops — and it shouldn’t. If you can prevent yellowing from the quinone-imide pathway, you prevent yellowing through that one mechanism. A paint protection film isn’t actually a film when finished; it’s a laminate – with a hardcoat at the top, an aliphatic TPU base film in the middle, a pressure-sensitive adhesive underneath, and a release liner.

People who do this professionally describe the yellowing of a laminate as either an indication that the hardcoat has degraded or that the base polymer was unstable, or both simultaneously. Adhesive layers discolour on their own schedule, and as the forum thread above illustrates, the underlying substrate will discolour on a completely third schedule.

A marketing claim, therefore, is weaker than the honest claim, but more useful. Aliphatic chemistry is a prerequisite for a laminate to remain colour stable in outdoor conditions. It’s not sufficient. Anyone selling you the word without the test data has sold you the prerequisite and expected you to assume it was the solution. Warranty claims are where this gap is found.

“Yellowing often indicates either the top coat has degraded or the base TPU itself is inherently unstable, or both.” a paint protection film converter

Structural Implications & Tengyang Specifications

On your line, the implications of this are structural, not visual. When yellowing or discolouration a customer photographs may start with the topcoat, the adhesive, the substrate or the film, proving the origin of the problem becomes extremely difficult after lamination unless each layer has been tested in isolation. That risk — the unknown — is what can turn a slight colour issue into a failed warranty claim.

Tengyang engineers to specifications — an aliphatic TPU film at the required gauge, and precisely manufactured with control on both width and thickness, effectively taking one layer out of the variable pool. In automotive lamination, particularly paint protection film, where a warm-toned panel under a 340 nm exposure is a failed product, not a rework, eliminating that one factor can mean significantly more than an attractive name. Order film samples and test your base layer independently before a full production run.

The 3 Soft Segment Failure Paths

Whether an isocyanate is aliphatic or aromatic affects the hard segment of the polymer, not the soft segment, and the vast majority of in-service failures attributed to UV originate in the soft segment. This is by far the most expensive misunderstanding in the category, because it’s entirely possible to buy an aliphatic-graded product, pay the premium that comes with it, and still observe failures for reasons entirely unaddressed by that aliphatic grade designation.

Hydrolysis resistance in a TPU is the result of the polyol, not the isocyanate. A polyester soft segment contains an ester linkage that’s attacked by water; a polyol-containing material will be weakened in hot and humid environments as its chain links are broken and it loses strength and form. A polyether soft segment doesn’t contain an ester linkage that’s prone to water attack, giving it an edge in damp conditions, though polyether has reduced wear and abrasion resistance and greater vulnerability to thermal degradation. Polycarbonate diol sits above both the polyester and polyether TPU film cost wise, and below both with compromise on properties. Making the decision between polyester TPU films, polyether TPU films, or a polycarbonate grade depends on your operating conditions, and this decision is orthogonal to whether the isocyanate is aliphatic.

The 3 Soft Segment Failure Paths — how an aliphatic film still fails

Polyester

(adipate, polycaprolactone)

Failure path Chain scission by water.

Where it bites Hot, humid, or wash-down service; tropical outdoor applications.

Specify it when Service is dry and you need maximum mechanical strength, toughness and abrasion resistance. The best physical properties in the family, on the condition that water stays away.

Polyether

(placeholder)

Failure path Thermal and oxidative attack on the ether linkage.

Where it bites Sustained high temperature; long ultraviolet exposure without stabilisation.

Specify it when Service is wet or humid, or the part must retain elasticity at low temperature. Hydrolytic stability is the reason polyether TPU films dominate wet-service lamination.

Polycarbonate

(PCDL)

Failure path Cost, and processing window.

Where it bites Budget, not the field.

Specify it when The part must survive both moisture and heat, and the failure cost justifies the premium. Named by market analysts as the chemistry of the premium grades, alongside isophorone and hydrogenated diphenylmethane isocyanates.

Now, read the matrix again with your purchasing perspective. Two out of the three points of potential failure have no relationship to ultraviolet (UV) light, and not a single one is helped by mentioning the word “aliphatic” on your specification. Simply asking for “aliphatic isocyanate” means that you’re only addressing about half the polymer.

An error Tengyang sees repeatedly runs like this: a purchaser asks for and pays for an aliphatic TPU, yet never names the soft segment in the material specification – and then blames UV exposure when the polyester-based TPU film degrades on a wash-down line. UV exposure is given credit because it occurs over a similar timescale, but it is water, not the sun, that attacks the polyester film. In as little as one humid season the mechanical strength can disappear! Unlike manufacturers who use the same material for all jobs, Tengyang extrudes our polyester, polyether, and polycarbonate soft segments in-house to specifically meet your environment; we guarantee dimensional tolerances on film width and thickness as well. As an incorrect soft segment is a design mistake that you cannot fix once the tools are made, this is the critical decision you must lock down first. Order a sample of the material with the soft segment suited to your application and test it under a UV-exposure regimen equivalent to ISO 4892-2 against your moisture exposure profile.

Aliphatic vs Aromatic: 11 Decision Rows

This table hasn’t been published by anyone else in the industry. For that reason, its omissions can be more important than its contents. Those rows where the matrix shows no numerical data indicate that suppliers don’t publish that information. If verified numbers exist, they’ve been cited. In any case where data hasn’t been found, we’ve said so, rather than leaving blank or inserting descriptive adjectives. Each dash in this table indicates a question you’ll need to ask every supplier, including ourselves.

Aliphatic vs Aromatic TPU — 11 decision rows, with sources

Decision factor	Aromatic TPU	Aliphatic TPU	Evidence
Hard-segment isocyanate	Contains a benzene ring (MDI, TDI families)	No benzene ring (IPDI, H12MDI)	QYResearch, 2025
Ultraviolet yellowing pathway	Urethane bridge oxidises to quinone-imide	Pathway chemically absent	Rosu et al., Polym. Degrad. Stab., 2009
Colour stability outdoors	Degrades; rate depends on stabiliser package	Retained — only if the topcoat and adhesive also hold	Converter field reports; see the four gates
Global average selling price, 2020–2025	Commodity band, below the aliphatic figure	USD 3,900 to 5,000 per metric ton	QYResearch, 2025
Raw material share of manufacturing cost	Lower	65 to 80 percent	QYResearch, 2025
Hardness range in the patent record	not comparable	80 to 98 Shore A	Patent CN111574822A
Tensile strength, patent-disclosed range	not comparable	20 to 45 MPa	Patent CN111574822A
Tear strength, patent-disclosed range	not comparable	60 to 110 N/mm	Patent CN111574822A
Light transmittance, patent-disclosed	not comparable	up to 95 percent	Patent CN104140517A
Hydrolytic stability	Governed by the soft segment. This axis changes nothing.		Material-science consensus
Thermal softening onset	Both soften above roughly 80 to 85 °C		Published TPU limitation reviews

Traditional

Aromatic TPU

Urethane bridge oxidises to quinone-imide under UV exposure, leading to yellowing.

Tengyang Advanced

Aliphatic TPU

Pathway chemically absent, ensuring superior long-term optical clarity outdoors.

There are two important figures worth highlighting. That price isn’t a negotiation tactic; it represents a cost driven by the material structure shown in the following row. This second point illustrates why the cost is what it is. We’ve included the hydrolysis row across both columns on purpose: this is the property most frequently mistaken for an “aliphatic problem.” And note that the patent ranges simply state what’s achievable within a material family, not what Tengyang sells in a single part. We aren’t presenting a datasheet on this page.

Formulating the Right Questions

A costly mistake this table is meant to prevent is purchasing on a price-per-kilogram basis only to be burned at the warranty stage. The aliphatic TPU PPF vs TPU query that search-box users make is, at heart, that same question about the base film-what polymer underlies the hardcoat. As about half the rows here lack any published numbers, any buyer who fails to ask for them in writing is making an assumption that’s in the case of a laminated structure a costly bet that might be paid in recalls instead of rework.

Tengyang will post ranges it can back up, asterisk ones it can’t, and produce the aliphatic TPU film or aliphatic TPU PPF base stock that actually has the values needed for your part. This table, as opposed to a data sheet full of adjectives in every field, should guide you in formulating the right questions. You can have a copy of this sheet with a service-environment worksheet and a column you can send to any supplier.

The Four Gates of a Non-Yellowing Spec

Every maker of aliphatic films—including us—claims they don’t yellow. That’s just an untestable statement as written. This below is a protocol that turns the untestable into testable; try it on any three suppliers and gauge their answers; often silence will be the best telltale. These tests are constructed not with our marketers’ hype but with published standards, which is why they aren’t always the most convenient for us, either.

Gate 1 xenon arc weathering chamber cycle test for TPU film

Gate 1, Name the standard and the cycle

An ASTM G155 is not a specification; there are 14 distinct cycles in this standard practice, not interchangeable ones. Most common Cycle 1 tests run using a Daylight filter at 0.35 W/(m²·nm) @ 340 nm irradiance, a black-panel temperature of 63 °C and a light/water-spray pattern of 102 minutes of light alternating with 18 minutes of light and spray. A vendor that sells and calibrates this chamber calls the irradiance low and cautions that it can result in slow results. Harsher cycles 7 and 8 use an Extended UV filter to deliver higher levels of UVB than would reach earth from the sun-a more common selection in the automotive industry and one that demands more of a material than Cycle 1 requires. What cleared in Cycle 1 does not tell you much about what cleared in Cycle 7. Which one did it pass?

Gate 2 TPU film exposure duration monitoring in a weathering chamber

Gate 2, State the exposure duration, in hours

An accelerated-weathering value without a cycle duration can be compared to nothing. Two hundred hours and 2,000 hours on the same cycle is not the same test. And even in an ISO 16474 (ISO 4892-2), the standard specification that uses xenon light in the presence of humidity for plastics, cycle and duration are still the two variables that tell the story.

Gate 3 TPU film colour shift measurement with a colorimeter

Gate 3, Quantify the colour shift, with its illuminant and observer

Yellowness isn’t a verdict; it’s a mathematical outcome. Yellowness index, ASTM E313, is derived from the CIE tristimulus values as YI = 100·(Cx·X − Cz·Z) / Y. The coefficients Cx and Cz aren’t fixed constants, but are chosen from a table depending on the illuminant and the standard observer present during the measurement. Yellowness index without reference to that specific pairing can’t be replicated by any supplier. What the industry ought to be reporting is the delta-YI of the exposed specimens versus an unexposed control from the same lot-and often does not. An accepted grey-scale colour-change rating would be second best, provided the rating scale is also named.

Gate 4 TPU laminate layer threshold and haze test setup

Gate 4, Declare the pass threshold in advance, and say which layer was tested

A threshold set after data is available isn’t a threshold at all. Define the highest yellowness value you will accept, the maximum transmittance, and the maximum haze (ASTM D1003), prior to specimens going into the test chamber. Then answer this most critical of questions, the entire point of this page: Was it the bare film tested or the finished laminate? A bare aliphatic can pass; a laminate finished using it will fail, if only because the top coat and adhesive never went into the oven. Companies that test the film and market the laminate aren’t lying, they are just answering a question that’s different from yours.

These four gates are the reason this page exists. Between them, the top two sites in the category have no test cycle data, no exposure hours, no yellowness figure, no threshold… and consumers notice. Advice now dispensed in the Paint Protection Film space suggests that purchasers examine reported performance and test data, and end consumers are asking their installers for colour-fastness and accelerated life-test data. The demand is there. The supply, in its current form, isn’t.

STRATEGIC VISION

This is the space Tengyang wants to occupy. If the brochure sites only rank on the strength of domain authority, and not content, then a clear and transparent answer-specify the standard, name the hours, quantify the colour shift under ISO 4892-2, note which layer was tested-is its own unique differentiator. Tengyang engineers the film precisely, according to your published acceptance criteria, on gauge, and will never provide a grey-scale rating that hasn’t been personally measured.

ACTIONABLE PROTOCOL

Pass these four gates to us as part of your purchase order, just as you will pass them to any of the incumbent name brands you are considering, and compare the accuracy of the answers rather than the confidence of the rhetoric. Ask for a quote, along with your intended cycle time, exposure hours, and maximum acceptable colour shift.

What We Have Tested, and What We Have Not

A page that spends four gates demanding evidence from suppliers owes the reader its own answer to the same questions. Here it is, without the softening language that normally goes around it.

Our current evidence position

We haven’t published accelerated-ageing data for an aliphatic grade under the Tengyang name. No exposure cycle, no exposure hours, no YI figure, no grey-scale rating. Not “data available on request” – not published. If you need a film whose colour stability is already documented in a third-party report today, that report doesn’t yet exist here, and you should weigh that before you specify us.

Substances, not sunlight

Compliance testing that does exist covers substances, not sunlight. Restriction-of-hazardous-substances testing under EU 2015/863, including phthalate screening, has been performed by an accredited third-party laboratory on this manufacturing operation’s hot melt adhesive film products. Those reports measure heavy metals and plasticisers. They contain no ultraviolet exposure and no colour measurement of any kind. They can’t support a non-yellowing claim, and we won’t present them as though they could.

Our manufacturing base

Our manufacturing base is a hot melt adhesive materials operation: adhesive films, webs, powders and granules across thermoplastic polyurethane, ethylene-vinyl acetate, polyamide, polyester and polyolefin chemistries, serving garment accessories, footwear, leather lamination, heat transfer printing, reflective materials, automotive interiors, packaging and building decoration. Extrusion capability, thickness and width customisation, and melt-point tailoring are what that operation does. What it hasn’t yet done is publish weathering data on an aliphatic film, and the distance between those two statements is exactly the distance this page refuses to blur.

What we do offer instead: the specimens, and the protocol

Send us the four gates as a purchase-order condition. We’ll produce film to your specification, you nominate the accredited laboratory, and the report is issued to you rather than to us. That’s a slower answer than a certificate on a web page. It’s also the only kind of answer that survives a warranty dispute.

Certification 1

Certification 2

Certification 3

Certification 4

Certification 5

Certification 6

Qualifying a new supplier

Qualifying a new supplier carries substantial risk, and to deny it would fail the same honest test this page applies to every other party. Since Tengyang has never issued its own, third-party ageing report we have to state frankly that the reason to qualify us is not a piece of paper-it’s an operational one: your specification is our manufacturing mandate. We extrude your film in house to spec, with absolute precision on thickness and width, subject to third-party testing at your chosen laboratory, under ISO 4892-2, with the report issued to your firm. An independently certified, individually issued report withstands the tests of an audit, two years later-unlike a mere brand badge on a web page. Qualify us; do not trust us. Send a sample and a detailed written test plan before you approve the first roll.

Qualify us, then verify

Request a free sample swatch and submit it to your own test laboratory on your own schedule. We’d much rather you verified us than took us at our word.

Procurement: What to Send Us, and What Drives the Price

To request an aliphatic polyurethane film quotation, simply send us the following: the quotation you receive is the engineering answer to your part, not a generic catalogue estimate. Because two different suppliers will bid differently on nominally identical product, knowing these six details is critical.

01 Enquiry Requirements

02 Price Drivers

03 Custom Quotation Policy

Request a Quote →

What to send with the enquiry

Service environment

Temperature, humidity and ultraviolet exposure profile decide the soft segment. This is the single largest lever on both price and field life.

Thickness & width

Gauge and web width drive line configuration and yield. Tolerance drives scrap.

Substrate & bonding

Adhesion behaviour differs across textile, polyethylene, polyvinyl chloride (PVC) and metal. The bond window, not the film, usually governs whether a laminate works.

Optical requirement

Transmittance and haze limits under ASTM D1003, if the part is seen through.

Colour-stability requirement

The four gates, stated as acceptance criteria. Name the cycle, the hours, the ΔYI ceiling, and the layer to be tested.

Regulatory scope

Substance restrictions, flame retardant requirement, moisture vapour transmission target, food or medical contact, bio-based content.

Annual volume & pattern

Determines whether a dedicated run is economic.

What actually drives the price

From highest cost to lowest, these factors determine your price.

Isocyanate and polyol

With raw material costs at between 2/3 to 4/5 of manufacturing expense, the choice of raw materials-polycarbonate-diol based grades in particular-will be your largest cost.

Gauge and tolerance

Thinner film with tight tolerance demands more cycle time and generates higher waste.

Width

Width, and the resulting trim losses.

Qualification costs

Third-party testing, verification and samples do represent real costs that this page insists on building into your quotation.

Custom Quotation & Risk Management

We don’t provide a price list, minimum order quantity or standard lead times here-and for a good reason. All three are meaningless until we know the six inputs listed above; any that are presented now do nothing more than offer false assurance. Send your specification, then we’ll send your quotation. Request a Quote.

Treating film as a commodity transaction where cost is the driving factor misses the true point: specification is the risk factor. Because lifetime costs are so heavily influenced by such variables as the soft segment composition, tolerance specification and qualification burden, Tengyang offers custom quotations, not generic catalogue entries. Whether building in-house your aliphatic TPU film, or aliphatic TPU PPF base stock, to a documented specification with tight tolerance on thickness and width, and underwritten by independent third-party testing in accordance with ISO 4892-2, issued to your company; our specification-driven quote reflects the exact product you will receive, unlike a stock listing. Submit the six required inputs and receive your engineering quotation.

Non-Yellowing Spec Request Builder

Turn “it won’t yellow” into a testable purchase-order clause. Fill the four gates below; the tool writes an acceptance condition you can send to any aliphatic TPU film supplier — Tengyang included.

Access Builder

Aliphatic vs Aromatic TPU — Decision Helper

The aliphatic premium earns out against failure cost, not against the cheaper grade beside it on the shelf. Four questions decide whether your part needs it.

Use Decision Helper

Soft-Segment Selector

Choosing “aliphatic” fixes the hard segment and the UV-yellowing pathway. It says nothing about hydrolysis or low-temperature flex — those are the soft segment. Match it to your service, or an aliphatic film can still fail.

Open Selector

What is the difference between aliphatic and aromatic TPU?

The isocyanate making up the hard segment. Aromatic thermoplastic urethane is based on an isocyanate with a benzene ring. This ring can absorb UV light, then it oxidises the urethane bridge to a yellow quinone-imide chromophore. Aromatic TPU is tougher on price and for most industrial applications is fine. Aliphatic TPU uses a straight-chain isocyanate that doesn’t have the ring structure so there’s nothing for the oxidation to start on. Other polymer characteristics (hydrolytic stability, low-temperature elastic performance, wear resistance etc.) all rely on the soft segment, not this difference.

Does aliphatic TPU film ever turn yellow?

The hard segment of the film can’t yellow by the aromatic mechanism because it has no benzene ring. The structure that this film is assembled with, though, very well can. That base polymer can be qualified against a named accelerated-weathering standard such as ISO 4892-2. The hardcoat above it could photo-degrade, the pressure sensitive adhesive below could discolour and the substrate underneath the entire stack could yellow by itself. Even a polyester soft segment could hydrolyse under humid conditions, lose its physical integrity, and do all of this with absolutely no UV light. If you’ve been given a “no” as an answer you’re being told about the polymer, and you’ve the work of learning about the laminate cut out for yourself. In practice, ask which of the four layers went into the weathering chamber and for how many hours; a supplier who can answer for the base film but not the finished stack has told you only half of what a warranty dispute will later demand.

What are the disadvantages of thermoplastic polyurethane?

Published reviews of limitations all concur. Thermoplastic polyurethane begins to soften around 80 to 85 °C and this disqualifies it from any long-term sustained service in high temperature applications. Because thermoplastic polyurethane is hygroscopic it must be dried prior to clean extrusion; if it isn’t dried, it degrades in the processing barrel. Thermoplastic polyurethane has a narrow process window to the point that process excursions are typically attributed to material issues rather than processing problems. Polyester grades can be problematic in hot and humid conditions. In terms of cost it’s above any commodity polymer such as PVC or polyethylene. Of course, this doesn’t account for the aliphatic premium price adder.

Can aliphatic TPU film be applied to matte paint?

This isn’t a decision to be made by the film; the decision belongs to the hardcoat. A controlled level of light scattering dictates the matte finish. A self-healing gloss hardcoat is designed to achieve the opposite goal. Give your desired finish specification to your laminate manufacturer and have a four gate discussion about their hardcoat, because with a matte structure, your hardcoat will be the first layer to undergo colour change.

Is aliphatic TPU film bio-based or environmentally friendly?

Bio-based polyol is available on the polyurethane market and this content is on the rise, however “aliphatic” and “bio-based” aren’t synonymous and a vendor may claim one without necessarily offering the other. Thermoplastic polyurethane is mechanically recyclable by definition because it’s melt processable; however, a laminate with an acrylic adhesive and a hardcoat can’t be. If a purchaser of material specifies bio-based content as part of its material criteria, it should ask for a percentage of bio-based content, and request an indication of the standard on which this is reported. Currently we aren’t publishing one.

What is the lifespan of a paint protection film made with a high-quality aliphatic TPU base film?

Converters currently market five to ten year warranties on the finished laminate. While those are commercial ratings on a multilayer assembly, they aren’t a direct property of the base film – the base film manufacturer doesn’t control the topcoat, the adhesive, the installation, or the wash regime. Ask the converter which layer they’ll warranty, and what the evidence is; then use the four gates and their answer. Please ask us the same four-gate questions rather than take our word for it.