How to Create a Downproof but Breathable Insulation Fabric Composition
When the filling of an object penetrates through the fabric to its outer, this is described as migration. To counter this, it is necessary to check whether your fabric composition or layering system is downproof, also known as fillproof. This means that the fabric can contain the filling without it protruding or escaping.
A common misconception is that downproofness can be predicted using a fabrics air
permeability or breathability value, suggesting that a breathable insulation fabric composition is therefore susceptible to filling migration. Whilst this may sometimes be the case, it cannot be assumed.
Calculating Downproofness
An entire sample (jacket, vest, prototype, etc.) is placed in the rotating box downproof test machine. It is then struck by rubber stoppers. This procedure attempts to mimic the actual use of the product. After 15 and 30 minutes, the machine is stopped and the sample is examined to determine the source of leakage (fibers or feathers protruding from the fabric, stitch lines, or seams). After the 30 minute cycle, loose & protruding fibers and feathers are counted and recorded.
The results of leakage are then graded on a scale of 1 to 5, 1 being the worst and 5 being the best. The grading scale is dependent on the type of sample, size of the product and stitching density. The source or location of leakage is also reported. The approximate amount and proportion of fibers or feathers protruding from the seams versus fabric is listed. Downproofness is considered poor when many fibers or feathers are able to pass through the fabric.
Calculating Air Permeability for Fabric Breathability
This is the number of cubic feet of air passing through a square foot of fabric per minute (or liters per square meter per second), expressed as: ft3/ft2/min (or liters/m2/sec).
For cotton fabrics numbers below 8.0, and for synthetics numbers below 3.0 are generally desired for downproofness. Lower air permeability numbers indicate the reduced ability for air to pass through a fabric. This however means that a fabric will be less breathable. For cotton an 8.0 or for synthetics a 3.0 or below indicates a greater likelihood that the fabric is downproof. However, certain fabrics may have a good air permeability number (< 8.0 or < 3.0) but fail the downproof test. On the other hand, other fabrics may have a poor air permeability number but pass the downproof test.
Relating Air Permeability to Downproofness
We recommend testing both of these factors on your breathable insulation fabric composition. As each test measures a different physical aspect of the fabric, the numbers are often unrelated. One measures the transmission of air through a fabric, while the other measures the physical transmission of down/feather material through a fabric.
However, testing has shown correlation between the air permeability of a fabric and its downproofness. Further information can be found here:
Technical Sewing Recommendations
As well as from downproofness, it is important to prevent any filling migration not only via fabric, but also via seam or stitch. We recommend observing the following points.
.
Sewing Needle
Check the sewability of the breathable fabric composition prior to processing to ensure it is suitable and whether the needle is appropriate. To prevent filling migration, we recommend using needles with a small diameter in order to keep the size of the stitch holes as small as possible.
Stitch Length
Using a larger stitch length reduces the number of stitch holes. This therefore means that the filling will have fewer points of escape.
Sewing Thread Type
The construction of the sewing thread itself can also help prevent filling migration. The use of smooth and even sewing threads prevents filling and fibers from sticking to the thread and thus migrating easily to the outside.
Sewing Thread Thickness
Another factor is the thickness of the sewing thread. The better the stitch hole is covered by the interlocking of the thread, the less likely it is that filling material will penetrate through it.
Sewing Thread Tension
The tension settings of the needle and looper threads should be as low as possible. This is because high tensions can stretch or enlarge the stitch holes, providing another opportunity for filling migration.
Recommendations for getting Optimum Breathability Performance from your Downproof Fabric Insulation Composition
As downproofness often leads to a decrease in breathability, here are some recommendations to counteract this so as to achieve both. For optimal breathable performance, use not only breathable fabrics where possible but a breathable insulation filling as well. This will greatly increase the breathability of the whole composition. If you then have to choose a less breathable outer fabric to ensure downproofness, the overall composition breathability still won’t be compromised.
Recommendations for Preventing Filling Migration
Alternatively, to prevent filling migration, use a lightweight scrim between the insulation filling and the outer fabric layer. This will decrease the breathability or air permeability of the composition, but will prevent filling migration therefore ensuring downproofness. We recommend using a 15gsm nonwoven scrim behind the outer fabric for this.
How to Create a Downproof but Breathable Insulation Fabric Composition
When the filling of an object penetrates through the fabric to its outer, this is described as migration. To counter this, it is necessary to check whether your fabric composition or layering system is downproof, also known as fillproof. This means that the fabric can contain the filling without it protruding or escaping.
A common misconception is that downproofness can be predicted using a fabrics air
permeability or breathability value, suggesting that a breathable insulation fabric composition is therefore susceptible to filling migration. Whilst this may sometimes be the case, it cannot be assumed.
Calculating Downproofness
An entire sample (jacket, vest, prototype, etc.) is placed in the rotating box downproof test machine. It is then struck by rubber stoppers. This procedure attempts to mimic the actual use of the product. After 15 and 30 minutes, the machine is stopped and the sample is examined to determine the source of leakage (fibers or feathers protruding from the fabric, stitch lines, or seams). After the 30 minute cycle, loose & protruding fibers and feathers are counted and recorded.
The results of leakage are then graded on a scale of 1 to 5, 1 being the worst and 5 being the best. The grading scale is dependent on the type of sample, size of the product and stitching density. The source or location of leakage is also reported. The approximate amount and proportion of fibers or feathers protruding from the seams versus fabric is listed. Downproofness is considered poor when many fibers or feathers are able to pass through the fabric.
Calculating Air Permeability for Fabric Breathability
This is the number of cubic feet of air passing through a square foot of fabric per minute (or liters per square meter per second), expressed as: ft3/ft2/min (or liters/m2/sec).
For cotton fabrics numbers below 8.0, and for synthetics numbers below 3.0 are generally desired for downproofness. Lower air permeability numbers indicate the reduced ability for air to pass through a fabric. This however means that a fabric will be less breathable. For cotton an 8.0 or for synthetics a 3.0 or below indicates a greater likelihood that the fabric is downproof. However, certain fabrics may have a good air permeability number (< 8.0 or < 3.0) but fail the downproof test. On the other hand, other fabrics may have a poor air permeability number but pass the downproof test.
Relating Air Permeability to Downproofness
We recommend testing both of these factors on your breathable insulation fabric composition. As each test measures a different physical aspect of the fabric, the numbers are often unrelated. One measures the transmission of air through a fabric, while the other measures the physical transmission of down/feather material through a fabric.
However, testing has shown correlation between the air permeability of a fabric and its downproofness. Further information can be found here:
Technical Sewing Recommendations
As well as from downproofness, it is important to prevent any filling migration not only via fabric, but also via seam or stitch. We recommend observing the following points.
.
Sewing Needle
Check the sewability of the breathable fabric composition prior to processing to ensure it is suitable and whether the needle is appropriate. To prevent filling migration, we recommend using needles with a small diameter in order to keep the size of the stitch holes as small as possible.
Stitch Length
Using a larger stitch length reduces the number of stitch holes. This therefore means that the filling will have fewer points of escape.
Sewing Thread Type
The construction of the sewing thread itself can also help prevent filling migration. The use of smooth and even sewing threads prevents filling and fibers from sticking to the thread and thus migrating easily to the outside.
Sewing Thread Thickness
Another factor is the thickness of the sewing thread. The better the stitch hole is covered by the interlocking of the thread, the less likely it is that filling material will penetrate through it.
Sewing Thread Tension
The tension settings of the needle and looper threads should be as low as possible. This is because high tensions can stretch or enlarge the stitch holes, providing another opportunity for filling migration.
Recommendations for getting Optimum Breathability Performance from your Downproof Fabric Insulation Composition
As downproofness often leads to a decrease in breathability, here are some recommendations to counteract this so as to achieve both. For optimal breathable performance, use not only breathable fabrics where possible but a breathable insulation filling as well. This will greatly increase the breathability of the whole composition. If you then have to choose a less breathable outer fabric to ensure downproofness, the overall composition breathability still won’t be compromised.
Recommendations for Preventing Filling Migration
Alternatively, to prevent filling migration, use a lightweight scrim between the insulation filling and the outer fabric layer. This will decrease the breathability or air permeability of the composition, but will prevent filling migration therefore ensuring downproofness. We recommend using a 15gsm nonwoven scrim behind the outer fabric for this.