What hydrostatic head do plastic waterproof pillow cases need?

Answer: 5000 mm for household use, 8000 for bed care.

Can a stitched case be waterproof?

Answer: Yes, with tape over the seam. A plain stitch holds 1200 mm, taped overlock reaches 5000.

Answer: They approximate two years of laundering. Below 80 percent retention, the film is too thin.

Answer: Three assessors score after 24 hours sealed, and the majority decides; above grade 3 fails.

The sample passes and production fails. Where do we look?

Answer: Fabric weight, seam process, and tape supplier — in that order. ---

Plastic Waterproof Pillow Cases: Inspection Standards

Quick answer: Plastic waterproof pillow cases are accepted on four metrics: fabric weight, hydrostatic head, seam strength, and zipper endurance. Each needs a test method beside its limit, because the word waterproof gives an inspector nothing to measure.

Four Core Metrics for Plastic Waterproof Pillow Cases
Incoming Checks on Fabric and Laminate
Seam and Zipper Water Tests
Dimensions, Odour and Hygiene Verdicts
Batch Sampling and Nonconformity Handling
FAQ

1. Four Core Metrics for Plastic Waterproof Pillow Cases

Structure comes first. A single heat-sealed film, a PEVA laminate, and a three-layer TPU build carry different limits, so one set of numbers fails good stock. State structure, weight, and lamination in the purchase file before arguing any verdict.

The four metrics are weight, hydrostatic head, seam strength, and zipper endurance. Weight sets film thickness, hydrostatic head sets the water ceiling, seams are where leaks concentrate, and the zipper fails first in service. A high head over a poor seam still leaks.

Each metric needs a method beside its limit. Write only waterproof, and the cheapest construction wins.

Metric	Unit	Limit	Method
Fabric weight	g per sq m	90 ± 5	100 sq cm disc, weighed
Hydrostatic head	mm of water	5000 or more	Rising column, 20 mm per minute
Seam strength	N per 25 mm	8 or more	Strip tensile
Zipper endurance	cycles	5000, no failure	Reciprocating rig
Wash retention	percent	80 or more	10 washes, retest

2. Incoming Checks on Fabric and Laminate

Sampling opens the inspection. Take three running metres per lot, skipping the first metre, because tension at the roll head lifts the weight reading. Cut a 100 sq cm disc, weigh to 0.01 g, convert to grams per square metre, allow ±5.

Plastic waterproof pillow cases: a clear case open on a bench, lid upright, screwdrivers, pliers and coiled black cable on kraft paper, task lamp behind

Next is peel strength. Below 3 N per 25 mm, a PEVA build blisters after a few washes. Third is pinholes: hold the sample against a 1000 lux source, where each bright point is a hole, and more than three in a metre fails. A pinhole nearly always leaks in the hydrostatic test, so rejecting it at incoming costs less than rework.

3. Seam and Zipper Water Tests

The seam is the weakest point on plastic waterproof pillow cases. Stitching leaves a line of needle holes, and water follows them.

Verdicts follow the process. A plain stitch holds about 1200 mm; overlock plus heat-sealed tape reaches 5000; high-frequency welding pierces nothing and reaches 8000. Judge each against its own line, or stitched styles never pass.

The zipper is the second failure point. A waterproof zipper runs 5000 cycles, must still close fully, and must hold 3000 mm when closed. Sealant at both ends needs pressing, since one lifted edge leaks at one point.

4. Dimensions, Odour and Hygiene Verdicts

Dimensions are judged on the inner opening, not the outer panel. Too small and the case will not fit; too loose and it slides into creases. A 48 by 74 cm cover suits a 50 by 75 cm pillow, with ±1.5 cm on the inner size and three readings averaged per side.

Plastic waterproof pillow cases: a frosted case open on a workbench, moisture marks in the lid, black foam cut-outs, soldering iron and wire strippers beside

Odour and hygiene are usually skipped. After sealed packing, rate smell from 1 to 5, where anything above 3 fails, since the source is adhesive residue. Formaldehyde stays at or below 20 mg per kg, phthalates at or below 0.1 percent, and children's versions follow tighter limits.

Wash resistance is retested, not assumed. Run 10 cycles at 40 degrees Celsius, dry, then repeat the hydrostatic test: retention of 80 percent or more and no seam lift. Film loss, blistering, or stiffness fails the lot.

5. Batch Sampling and Nonconformity Handling

Plastic waterproof pillow cases are sampled under GB/T 2828.1 at general level II, AQL 4.0 for appearance and 2.5 for function. Function covers hydrostatic head, seams, and zipper; one failure rejects the batch, with no sorting allowed.

Nonconformity has three levels. Minor appearance defects go to rework; functional failures return the lot; two returns in a row suspend the supplier. Keep three retained units per batch, marked with lot and date, for 12 months.

Lot size	Sample	Appearance accept and reject	Function accept and reject
151 to 280	32	3 and 4	0 and 1
281 to 500	50	5 and 6	1 and 2
501 to 1200	80	7 and 8	1 and 2

Conclusion

Accepting plastic waterproof pillow cases means turning one word into numbers: grams per square metre, millimetres of water, newtons, zip cycles. Numbers in the file lock the process, and a locked process makes batches comparable. That is how plastic waterproof pillow cases stop being judged by feel.

This article discusses only the container (case body) side of specifications and design intent, and does not cover any handling, loading or use of the contents.