Yarn Abrasion Resistance Ranking for Knit Bags: Martindale Cycles by Fibre, Gauge and Finish

How to Read an Abrasion Number on a Yarn Sheet

An abrasion figure is only meaningful when three things are stated with it: the test method, the load and the endpoint. A number quoted without all three is marketing, and it is the most common reason two labs disagree about the same fabric.

The method for bags is ISO 12947-2, the Martindale method, which rubs a fabric against a standard worsted wool abradant in a Lissajous figure. The load is stated in kilopascals, and 12 kPa is the usual choice for a bag body while 9 kPa suits a liner. The endpoint is either fabric breakdown, which is two broken threads, or a subjective assessment at a fixed cycle count.

Insist on breakdown figures rather than assessment figures when you are comparing yarns. An assessment at 20,000 cycles tells you the fabric survived; a breakdown number tells you how much margin it had. Margin is what absorbs lot-to-lot variation in a 30-day bulk run.

The Ranking: Nine Yarns by Martindale Cycles to Breakdown

The table below ranks the yarns that realistically appear in a knitted bag programme, tested as single-polymer panels at a common construction: 300D equivalent, E12 gauge, 420 g/m², ISO 12947-2 at 12 kPa to breakdown, conditioned under ISO 139.

Read it as a ranking of families rather than of individual yarns. Within a family a tenacity grade, a filament count or a finish can move a specific yarn one row up or down, but the order of the families is stable across constructions.

Why PA6 Sits at the Top of the Ranking

Nylon 6 leads because it combines high tenacity with high elastic recovery, and abrasion is largely a recovery problem. Each rub cycle deforms the surface; a fibre that springs back dissipates the energy, and a fibre that stays deformed accumulates damage.

PA6 recovers about 98 percent from a 4 percent strain where PET recovers roughly 90 percent. That difference compounds over thousands of cycles and it is why a PA6 panel reaches 30,000 cycles against 25,000 for PET of identical count and construction.

The second reason is toughness at the filament level. PA6 filaments resist surface crack propagation better than PET, so the damaged layer that forms in the first few thousand cycles stays thin. On a bag the practical consequence is that a PA6 base panel survives a concrete floor, and a PET one shows a grey worn band.

Where Polyester Lands and Why Recycled PET Differs

Polyester is the default for a reason: it reaches 25,000 cycles, which is ample for a bag body, at a lower cost per kilogram than PA6 and with better light fastness. The gap to nylon matters only in the highest-wear zones.

Recycled PET lands at roughly 22,000 cycles, about 12 percent below virgin, because the polymer chains are shorter after mechanical recycling and the molecular weight distribution is wider. That is a small penalty for a Global Recycled Standard claim, and it is easy to offset by moving up one count or one filament count.

The offset that works best is filament count rather than count. Going from 300D/48f to 300D/96f recycled PET recovers most of the 12 percent, because finer filaments distribute the contact load over more surface. It costs nothing in weight and adds a slightly softer hand, which most bag programmes want anyway.

Polypropylene, Cotton and the Bottom of the Table

Polypropylene reaches about 12,000 cycles and it is included in the ranking because it is specified often, usually for the wrong reason. Its specific gravity of 0.91 makes it the lightest option per volume, which is genuinely valuable on a bag sold by weight, but it abrades poorly and it has a low melting point of 165 °C.

Cotton sits at the bottom at about 8,000 cycles, and it fails differently. Rather than forming a worn band, a cotton knit fibrillates and then holes, so the failure is sudden and visible. For a natural-look liner in a low-load bag that is acceptable; for any load-bearing panel it is not.

The lesson at the bottom of the table is about fit for purpose rather than about quality. A promotional bag that will be carried twice does not need 30,000 cycles, and paying for nylon there is money spent on a property the product will never use.

When the Ranking Is the Wrong Tool: Edge and Fold Abrasion

Martindale rubs a flat surface, and a bag wears at edges and folds. A ranking built on flat abrasion will rank a monofilament panel highly while that panel cracks at a fold, and it will not predict the most common field failure on a knitted bag.

Edge abrasion happens where a strap meets a body, where a zip tape runs along an opening, and where a bag is set down on a corner. Those are line contacts at high local pressure, and the failure mode is filament cutting rather than surface wear. A flat Martindale result does not describe it.

The second test that belongs in a specification is therefore a fold or edge abrasion test, rubbing a folded specimen against itself or against the abradant for 5,000 cycles. Monofilament drops sharply here while a fine-filament multifilament holds up, which inverts part of the flat ranking.

Test, flat abrasion

ISO 12947-2, Martindale, 12 kPa to breakdown

Test, edge and fold

5,000 cycles on a folded specimen, assessed at 10x

Abradant

Standard worsted wool, replaced every 50,000 cycles

Conditioning

ISO 139, 20 °C and 65 percent RH, 24 hours

Endpoint

Two broken threads, or 30 percent surface disturbance

Assessment

Grey scale for change in shade, grade 4 minimum

Gauge and Stitch Move the Number by More Than You Expect

Two panels of identical yarn can differ by 30 percent in abrasion simply because they were knitted at different gauges. Gauge sets loop size, and loop size sets how much of the yarn sits proud of the surface where the abradant can reach it.

At E7 the loops are large and the crowns stand high, so the abradant catches them early and the count to breakdown falls. At E14 the surface is flatter and more contact area is presented, so the same yarn lasts longer. Measured on 300D PET, E7 gave about 18,000 cycles against 25,000 at E12.

Stitch structure is the second lever and it is often worth more than the yarn choice. A tuck or miss structure that places a float on the wear face can halve the result; a structure that presents the loop legs rather than the crowns can add 20 percent. On a base panel this is the lowest-cost abrasion improvement available.

Finishes That Buy Abrasion Without Changing the Yarn

When the yarn is already chosen and the number is short, three finishing routes add abrasion resistance without changing count or polymer. Each has a different cost and a different effect on hand.

Heat setting is the first and it is free in the sense that you are probably doing it anyway. Setting a PET panel at 180-190 °C stabilises the loops and typically adds 10-15 percent to the cycle count, because a stable loop does not shift under the abradant and expose new surface.

A resin or polyurethane coating is the second and it is the heavy option. A light PU back-coat can take a PET panel from 25,000 to beyond 40,000 cycles, but it adds 30-50 g/m², stiffens the hand and can complicate a recycled-content claim. Use it on the base only.

The third route is a harder yarn in the wear zone only. Knitting the base course in PA6 and the body in PET costs a few grams and moves the base from 25,000 to 30,000 cycles, which is the most targeted way to spend the money.

Specifying Abrasion: Load, Endpoint and Acceptance Criteria

An abrasion clause is complete when it names the method, the load, the endpoint, the acceptance number and the sampling rule. Five lines, and anything less leaves an argument open at final inspection.

• Method: ISO 12947-2, Martindale, abradant replaced at the standard interval.
• Load: 12 kPa for a bag body, 9 kPa for a liner, stated explicitly rather than implied.
• Endpoint: two broken threads, or a stated percentage of surface disturbance if the panel will not break.
• Acceptance: a cycle floor with margin, typically 20 percent above the field requirement, not the field requirement itself.
• Sampling: one specimen per colour per lot, tested after conditioning to ISO 139, with the report kept against the bulk record.

The acceptance number deserves a note. A bag expected to see 15,000 cycles of real wear should be specified at 18,000 or more, because laboratory abrasion and field abrasion are not the same thing and because lot variation on recycled yarns runs wider than on virgin.

Cost per Cycle: What the Ranking Means for Price

Ranking by cycles is useful; ranking by cost per cycle is what a buyer actually needs. On a bag costing about USD 4.80 in yarn at 100 pcs, the difference between the first and fourth row of the table is real money that has to be justified by the use case.

Abrasion Checklist Before Bulk Release

Use this list before committing a 30-day bulk run. It is written as pass or fail items so an inspector can work through it without interpretation.

1. Confirm the abrasion clause names ISO 12947-2, the load in kPa and the endpoint, all three on one line.
2. Check the trial panel reached at least 20 percent more cycles than the field requirement.
3. Run the 5,000-cycle fold test on any panel containing monofilament or a coarse gauge above E10.
4. Verify the abradant and the conditioning: worsted wool within its change interval, 20 °C and 65 percent RH for 24 hours.
5. Confirm the finishing recipe is locked, because heat setting alone moves the result by 10-15 percent.
6. Record the yarn lot reference against the test report so a future lot can be compared like for like.

Six items, and each one closes a specific argument that otherwise resurfaces when a container is already booked. The cost of running them is one sample cycle at 7 working days, which is a fraction of a bulk reorder.

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