A pvc blinds and slats claim almost never arrives in the first month. It arrives after a season, in a specific climate, on a specific batch. The four patterns below account for most of them.
Why failures cluster around one or two parameters
In PVC slats, the parameters in the table below are not independent. UV stabiliser and Yellowing resistance between them explain most field failures, and both are routinely omitted from quotations because they are expensive to guarantee and easy to leave vague.
| Parameter | Typical range | Why it decides failure |
|---|---|---|
| UV stabiliser | required, stated in phr | Without it, white goes yellow and colours fade within a season outdoors. |
| Yellowing resistance | QUV 300-500 h, dE <= 3 | The test that separates outdoor-grade from indoor-grade PVC. |
| Heat deflection | >= 65 C | Slats in a sun-facing window reach 60 C+ behind glass. |
| Colour | white / woodgrain / solid colours | Woodgrain is a film or co-extrusion; co-extrusion lasts longer. |
1. Yellowing
What you see. White slats turn cream within a year in a sunny window.
Why it happens. Insufficient or wrong UV stabiliser; often TiO2 grade rather than a true UV package.
How to catch it before you order. QUV 300 h, measure dE and yellowing index.
What to specify instead. Specify the stabiliser system and require the QUV report; do not accept ‘UV treated’.
2. Heat warping
What you see. Slats bow in a south-facing window in summer.
Why it happens. Heat deflection temperature below the in-window temperature.
How to catch it before you order. Deflection test at 60 C for 4 h under load.
What to specify instead. Higher HDT formulation and a minimum 2.0 mm wall.
3. Cold brittleness
What you see. Slats crack when handled in an unheated warehouse in winter.
Why it happens. High filler content (calcium carbonate) to cut cost.
How to catch it before you order. Impact test at -10 C.
What to specify instead. Limit filler content and specify impact-modified compound for cold markets.
4. Woodgrain film peeling
What you see. The decorative film lifts at the edges.
Why it happens. Laminated film without adequate primer or edge sealing.
How to catch it before you order. Cross-hatch plus 72 h at 40 C / 90 % RH.
What to specify instead. Co-extruded woodgrain for contract work; laminated film only for dry indoor use.
Building a test plan you will actually run
| Test | Method | Acceptance |
|---|---|---|
| Yellowing | QUV 300 h | dE <= 3 |
| Heat deflection | ISO 75 / 60 C load test | no visible warp |
| Impact at low temperature | -10 C drop test | no crack |
| Colour fastness to light | ISO 105-B02 | >= grade 4 |
| Fire performance | EN 13501-1 | B-s1,d0 where specified |
Five tests is enough for a first order. The point is not comprehensiveness, it is that the same five run on every lot, so a change becomes visible. A test nobody repeats is a story, not a control.
Run them on production material, not on a development sample. Ask for the report to carry the lot number and the date, and keep it with the shipment file. When a claim arrives two years later, that file is the difference between a discussion and a write-off.
What the report should contain
- The method, by standard number, not by description.
- The measured value, not only pass or fail. A marginal pass tells you where the risk sits.
- The sampling position: which roll, which metre, which batch.
- The conditioning before testing, because humidity changes several of these results.
- The laboratory name and the date, so the report can be traced.
Specification ranges for PVC slats are on the product page. If a failure you are seeing is not covered here, send the batch details and photographs — we will tell you what we think caused it, including when the cause is upstream of the material.
Questions buyers ask before ordering
Will white PVC yellow in a sunny window?
Not if it is properly stabilised. Ask for a QUV 300 h report with dE <= 3. Without that report, assume it will yellow.
Is PVC allowed in the EU?
Yes for window coverings, but the compound must comply with REACH and heavy-metal limits, and some buyers restrict PVC on brand policy grounds. We supply both and will tell you which is more common in your market.
How does PVC compare with basswood on price?
Typically 20-30 % cheaper per set at the same size, and lighter to ship than wood but heavier than paulownia.
Seven lines that turn a quotation into a specification
Most post-delivery arguments are not about quality. They are about a document that never said which figure would be measured, on which instrument, at whose cost.
- Colour: agree the test method with the number. Two labs, two methods, two answers, one argument.
- Fire performance (available to EN 13501 B-s1): state where in the band this order sits. The middle of the band is not what a tolerance is for.
- Warp tolerance: the figure you will accept inside the <= 1.0 mm per 1 m at 60 C band, the tolerance on it, and the method used to measure it.
- Slat width (25 / 35 / 50 mm): name the number, not the word. If the answer only repeats the band, ask which point inside it is being offered for this order.
- Deviation rule: anything outside the agreed bands is reported before shipment, not after arrival.
- Packing and marking: shipping mark, roll or carton count and the tolerance on quantity, since a short shipment is a claim too.
- Who inspects: third-party, in-house or none, decided in advance, with the AQL level written down.
Three questions, and the answers that separate mills
If the claim you are handling is going to be decided on a call, take these three questions into it.
| Question | Answer that should worry you | Answer that holds up |
|---|---|---|
| Which test catches cold brittleness? | “We have never had a complaint.” | Impact at low temperature — on the production lot, with the acceptance figure written into the report and not into the email. |
| May I see a report for a lot you shipped last month? | “That is confidential customer information.” | A redacted report, which carries every number that matters and none of the customer’s identity. |
| Where in the available to EN 13501 B-s1 band will this order sit? | “In the middle, normally.” | A stated target and the readings behind it. Fire performance drifting inside the band is how a conforming lot still fails. |
Dealing with a failure now, or trying to avoid one?
Send a window schedule or a single set size and we will return a quotation with the loading plan, the safety standard that applies to your market and the lead time for the colour you need. Catalogue and current price list on request.
Related reading
Catalogue and current price list · Neutral packing and private label · Consolidation, documents and lead times
