What is the practical difference between a monocomponent and a bicomponent permeable route?

The interface count, and everything that follows from it. A monocomponent coating produces its transmission inside one layer, so there is no bonded permeable interface to protect and no peel clause to write. A bicomponent build combines two permeable functions, which raises the transmission ceiling and adds an interface that has to survive washing — so peel testing enters the clause set where it was not needed before.

Our transmission figure is lower than the supplier's for what should be the same build - why?

Most often because the method is not the same. Transmission is read under GB/T 12704.1, GB/T 12704.2-A, GB/T 12704.2-B, JIS L1099-B1 or ASTM E96 in this scope, and for a waterproof-and-breathable construction the inverted-cup method GB/T 12704.2-B is the usual clause. The figure is quoted in g/m²·24h, and the method has to be named with it before two figures are compared.

Do I need a peel clause if the construction is a single coating with no membrane?

Not as a bonded-interface clause, because there is no separate permeable layer to delaminate. Peel under FZ/T 01010 applies where a build has an interface, which is exactly what a bicomponent route introduces. If the programme moves from monocomponent to bicomponent, the peel clause should be added at the same time rather than after the interface is already in production.

Which route gives the better handfeel?

Generally the monocomponent route, because it reaches its transmission inside one layer and needs no bonding pass. A bicomponent build adds a second function and an interface, and both firm up the handle and add mass, which is verified under GB/T 4669. Handfeel should be judged on the washed article against a retained reference swatch, because the difference appears at garment stage rather than on the development table.

The interface on our bicomponent build survived delivery and failed after washing - what should have been written into the specification?

A post-wash peel requirement: FZ/T 01010 on the coated or laminated fabric, with a named tier and a washing standard under GB/T 8629, ISO 6330 or AATCC 135. An as-received figure does not describe the interface after washing, and the tier cannot be read without the washing standard, because the three candidate standards do not apply the same mechanical action.

Monocomponent and Bicomponent Moisture-Permeable Coating: Buying Breathability with Steps or with Layers

For fabric development, sourcing and product teams Prepared by the Technical Department, Suzhou TTK Textile Technology Group Co., Ltd. The standard numbers below come from TTK's commissioned testing scope; the process statements come from TTK's own capability record.

Bottom line

A monocomponent coating reaches breathability inside one layer; a bicomponent build stacks two mechanisms and adds an interface to keep intact.

1. The two routes, in process terms

	Monocomponent permeable coating	Bicomponent permeable coating
What is on the fabric	One coating layer that is itself permeable — the layer transmits without a separate membrane and without a bonding pass	Two permeable functions combined in one build, drawn from the same four permeable routes available in this scope
How the vapour leaves	Through the single layer, by the mechanism that layer uses	Through both functions in series
Interfaces created	None beyond the coating-to-fabric interface	At least one additional interface where the two functions meet
Process consequences	Fewer process steps, less mass, better drape	More steps, more mass, more process control

Both routes are available here, alongside four permeable mechanisms in the scope: a hydrophilic, non-porous route that transmits by molecular transport with no pores; a microporous route produced by wet-process PU foaming; a monocomponent route where a single layer is permeable on its own; and a bicomponent route where two of these are stacked.

The distinction that matters commercially is the interface count. A monocomponent coating has no bonded permeable interface to protect. A bicomponent build introduces one, and every interface has to survive washing, which puts peel testing into a clause set where it did not previously appear.

2. What each route is good at, and what it costs

Property	Monocomponent	Bicomponent
Transmission	Set by the single layer's mechanism; the practical ceiling is the layer itself	Higher ceiling, because two mechanisms act in series and each can be optimised for its own part of the range
Water resistance	Set by the layer's own continuity, read under GB/T 4744, ISO 811 or AATCC 127	Set by the combined build; an extra dense function can raise it further
Handfeel and drape	Generally softer, because there is one layer and no bonding pass	Firmer, because a second function and its interface both add structure
Mass per unit area	Lower, verified under GB/T 4669	Higher, and it rises with each added function
Process steps	Fewer: the permeable function is produced in the coating step	More: the two functions have to be produced and combined
Peel requirement	Not applicable as a bonded-interface clause, since there is no permeable interface to delaminate	Applies, under FZ/T 01010, with a wash tier under GB/T 8629, ISO 6330 or AATCC 135
Failure mode if process drifts	Coating weight and film formation, which show up in transmission and water resistance	The above, plus interface failure, which appears after washing rather than on the delivered roll
Where it fits	Programmes where mass and handfeel matter and the transmission target is reachable in one layer	Programmes where the transmission target cannot be reached in one layer without losing water resistance

3. The interface is the hidden cost of a bicomponent build

A bicomponent build is chosen when one layer cannot deliver the transmission and water resistance targets at the same time. What is usually left unsaid is what the extra function costs on the quality side:

An additional bonded interface that has to survive the wet process, drying and then washing.
A peel clause where there was none — FZ/T 01010 on the coated or laminated fabric — plus a post-wash peel figure at a named tier.
A wider process window to control, because the two functions interact during drying: the drying condition that suits one can be wrong for the other.
More mass, and a firmer handle, which the programme feels at garment level even when the laminate figures look the same.
A more complicated complaint path, because a transmission loss after washing can come from the layer, from the interface, or from the drying profile.

A useful rule of thumb for the development meeting: if the transmission target can be reached inside one layer, the monocomponent route removes an entire class of failure. If it cannot, the bicomponent route is the answer and the peel clause has to be written at the same time as the transmission clause.

4. Test clauses, and which ones change with the route

Clause	Standard in this scope	What changes between the two routes
Moisture vapour transmission	GB/T 12704.1 and GB/T 12704.2-A, or GB/T 12704.2-B as the inverted-cup clause for a waterproof-and-breathable construction; JIS L1099-B1 and ASTM E96 also sit in the scope	Nothing in the method — but the bicomponent figure is produced by two functions in series, so the method has to be named before the two routes are compared
Water resistance	GB/T 4744, ISO 811, AATCC 127	A dense second function can raise the figure; on a single layer the figure follows the layer's continuity
Repellency	AATCC 22 (points), ISO 4920 and GB/T 4745 (grades)	Applies on top of either route, and it is judged on the face fabric rather than on the permeable layer
Peel strength	FZ/T 01010, in N/25mm or N/cm	Applies to the bicomponent build's interface; there is no bonded permeable interface to test on a monocomponent coating
Air permeability	GB/T 5453, ISO 9237	A microporous function moves this figure as well as transmission, so it belongs in the clause set where wind or down-proofing matters
Mass per unit area	GB/T 4669	Rises with the second function, so it is worth writing into the clause set whenever the layer count is under discussion

Transmission is quoted in g/m²·24h and the method has to be named with the figure. GB/T 12704.1, GB/T 12704.2-A, GB/T 12704.2-B, JIS L1099-B1 and ASTM E96 are different methods, and figures from different methods are not interchangeable — which is also why the same bicomponent build can appear to perform differently in two buyers' hands.

5. Common pitfalls

Pitfall	What it looks like	Cause
Choosing bicomponent before checking whether one layer would do	Extra process steps, extra mass and an interface to defend, for a target a single layer could reach	The transmission target was never tested on a monocomponent trial
A transmission figure quoted with no method	Two suppliers disagree about the same build	GB/T 12704.1, GB/T 12704.2-A, GB/T 12704.2-B, JIS L1099-B1 and ASTM E96 are not interchangeable
No peel clause on a bicomponent build	The interface fails after washing, and there is no agreed figure to judge it against	Peel was treated as a lamination topic rather than as a consequence of the route
A wash tier written without a washing standard	"After wash" appears on the report	GB/T 8629, ISO 6330 and AATCC 135 differ in mechanical action
One drying condition applied to two functions	One function performs and the other drifts	The two functions interact during drying and each has its own window
Mass not written into the clause set	The garment is heavier than the approved sample	The second function adds mass, verified under GB/T 4669, and nobody checked
A microporous function chosen for transmission only	Wind resistance or down-proofing behaviour changes unexpectedly	A microporous structure moves air permeability as well, read under GB/T 5453 or ISO 9237
A monocomponent route expected to fail	The programme assumes more layers is always better	The layer count is a cost decision, not a quality grade

6. Working order for development teams

Test the target on a single-layer trial before committing to a second function, so the route is chosen against a measurement rather than an assumption.
Name the transmission method and the unit in the clause set — GB/T 12704.2-B for a waterproof-and-breathable construction, with the figure in g/m²·24h.
Add the peel clause on the same day as the transmission clause if the build has an interface, under FZ/T 01010 with a wash tier and a washing standard.
Write the mass target into the clause set, verified under GB/T 4669.
Add the air permeability clause where the end use needs it, under GB/T 5453 or ISO 9237.
Settle the water resistance standard and the ramp rate in writing, since the two routes reach the same figure from different constructions.
Test post-wash at sample stage, at the tier the programme intends to claim.

Criteria Table: How to Tell Whether the Route Was Chosen Correctly

Criterion	What Passing Looks Like	Common Failure
The transmission target was tested on a single layer	A monocomponent trial result exists against the target before a second function is added	A bicomponent build is specified by default, and the extra steps and mass are never questioned
The clause set matches the route	A monocomponent coating carries no bonded-interface peel clause, and a bicomponent build does	Peel is either written for a build that has no permeable interface, or omitted from a build that does
The transmission method is named with the figure	The clause names GB/T 12704.1, GB/T 12704.2-A, GB/T 12704.2-B, JIS L1099-B1 or ASTM E96, with the figure in g/m²·24h	A figure is quoted with no method, and two suppliers appear to disagree about the same build
The inverted-cup clause is used where it applies	A waterproof-and-breathable construction is judged under GB/T 12704.2-B	A method not intended for waterproof-and-breathable fabric is applied and the figure is not comparable
The peel clause carries a tier and a washing standard	Peel is required under FZ/T 01010 after a named tier and under GB/T 8629, ISO 6330 or AATCC 135	An as-received peel figure stands in for the behaviour of the interface after washing
The water resistance standard and ramp rate are fixed	The clause names GB/T 4744, ISO 811 or AATCC 127, and states the ramp rate where the standard permits a choice	The figure is argued after the bulk order, at a rate the sample was never tested at
Mass is written and verified	The target mass is in the clause set and verified under GB/T 4669	The added function pushes the article past the approved sample
Air permeability is covered where the end use needs it	The clause names GB/T 5453 or ISO 9237 where wind resistance or down-proofing matters	A microporous function changes airflow and nobody re-checked
The drying condition is set per function	The drying profile is set for the build's own functions and recorded with the roll	One profile is applied to two functions with different windows, and one of them drifts
The failure mode is named in the specification	The specification says what will be watched — layer weight, film formation, or the interface	Nothing is named, so a post-wash loss of transmission has no agreed route to being traced
Handfeel is judged on the washed article against a reference	The hand verdict is taken on the washed swatch of the same lot, against a retained reference	A firmer bicomponent handle is discovered at garment stage rather than at development stage
A retained sample exists per lot and per article	A same-lot retained sample is kept so a transmission or interface complaint can be traced	No retained sample survives, and the complaint cannot be separated from a later process change

Monocomponent and Bicomponent Moisture-Permeable Coating: Buying Breathability with Steps or with Layers