Backpack Material Delaminating
Polyurethane Coating Information
PU coated fabric is made up of a synthetic woven base fabric (usually polyester or nylon) with a waterproofing Polyurethane Coating or laminate. The polyurethane coating is applied to a single side of the base fabric, this makes the fabric water resistant, light weight, and flexible. Applications include: camping tents, light duty covers, clothing, bags, and backpacks.
Wholesalers and manufacturers see PU Coatings as having a limited lifespan, and do not guarantee for life the integrity of fabric coatings, and neither can White Mountain Backpacks™. The good news of coatings peeling is the fabric strength usually increases - and in wet weather rain covers are generally recommended. Many things can have an impact on the life of PU Coatings just as environmental factors affect foam. Moisture (dry your backpack well after wet weather), mold,
excessive heat (this may apply to tropical climates, especially with high humidity), and chemical contamination (harsh cleaning products, salt water, and chlorinated pool water to name a few) can contribute to the break down or delaminating of the PU Coating. Also, these PU Coatings will wear off over time; anywhere between 5-15 years depending on the use and care of the product. To extend the life of the PU Coating, always store backpacks in well ventilated areas and take care of
these PU Coated products as you would anything valuable.
It is important to remember that the deteriorating of the PU Coating over time does not mean your backpack requires replacing, and this event is expected with all PU Coated materials. We have listed some suggestions for restoring the water proofing of your backpack in the following, however, please note we cannot take responsibility for any mishaps that may occur using these techniques.
Prevent Continual Delamination and Reproof Backpack
Having tested an ironing technique we have found it basically works in arresting the continual delaminating of PU material in a backpack.
By using a modern iron on synthetic (the iron just does not need to be that hot) on DRY (no steam) and ironing the affected area through two (2) sheets of 80gsm copy paper it does seem to do the trick. However, any very loose material will strip away from the material and stick to the paper (it is very important NOT to over iron and to NOT over heat any one area). Better to do it briefly throughout the affected area ironing just past where the delaminating begins. This needs to
be done very carefully and the iron should never make contact with the material directly (there is a risk of melting the material), or be in contact with the one area of the material for very long (will heat all the laminate to a point where it adheres to the paper). Finish by spraying the coated face of the fabric with a silicon or Teflon based water repellent. Your specialist outdoor store will have a suitable product.
This is one method of arresting the continual delaminating, after treating your backpack to arrest the delaminating of the PU coating we do recommend to NIKWAX 'Tent & Gear SolarProof®' Waterproofing.
Customer Response to this Repair Technique
I have followed the procedure you suggested and it has worked a treat - I'm really pleased with the result. Some of the seams were quite hard to get to so I used a hair drier and just gave the heated areas a squeeze with fingers. There was enough heat to laminate the film back onto the fabric without burning fingers. The edges of the pen pockets were just starting to shed so used the hair dryer on this as well.
All in all an excellent outcome!
Many thanks Graeme - (Tested on a 10 year old University II Daypack)
Repair Severe Delamination and Reproof Backpack
First remove all the delaminated PU material. We have found that using a stiff brush on a vacuum cleaner works very well, and stops the delaminated PU from spreading and sticking to everything. Make sure you get under all the seams and thoroughly remove all the delaminated PU material.
Next make sure the backpack material is clean and apply a NIKWAX 'Tent & Gear SolarProof®' Waterproofing. We have had great success with this, and you need to carefully follow the instructions provided. Remember a little goes a long way and there is no need to saturate the material, simply apply a light spray on the material and wipe the excess spay away with a damp cloth. Also, the instructions recommended spraying the outside of the material, however we had great success
spraying the inside, the reverse side of the material.
Your backpack material should now be as waterproof as it was when new.