Backpack Construction

Backpack Material Delamination

Delaminating of the Polyurethane Coating

Over a long period of time all synthetic laminated backpack materials are prone to the delaminating of the Polyurethane (PU) Coating. This can occur naturally or be hasten by exposure of the Polyurethane Coating to direct sunlight for long periods, heat and high humidity.

All Polyurethane Coated synthetic backpacks with a PU Coating will eventually delaminate. Generally most backpacks will have worn out before delimitation takes place. However, with a good quality backpack this isn’t the case. Removing the flaky delaminated PU coating can be done with a little effort and the material can be reproofed with NIKWAX 'Tent & Gear SolarProof®' Waterproofing.

An effective instant solution to the sticky PU coating is to coat the delaminated area with Talcum Powder.
This may not be a long term solution but is recommended to solve this problem in the short term.

Delay Delamination of the Polyurethane Coating

A little common sense will prevent premature aging of the synthetic material's PU Coating. Always clean and dry your backpack before you put it away. Never pack or store you’re a backpack if it is dirty or damp. Wet synthetic material can also mildew which causes corroded zippers, delaminating, leaks, and foul smells. There is no cure for delaminating and severe mildew damage.

When put in storage the backpack must be 100% dry and preferably stored hanging in a cool shaded area so air can circulate around the backpack. Storing your pack while it is damp will cause the PU Coating to soften become sticky and stick to itself (a chemical reaction called hydrolysis). With prolonged exposure to moisture, the coating will flake and peel away from the fabric and create leakage.

Delaminating of the Polyurethane (PU) Coating can prematurely occur with the use of Harsh Chemicals used to clean the backpack, long periods of exposure to Salt Water, exposure to Swimming Pool Chlorine. Always rinse well immediately and dry thoroughly by hanging in a shady area after immersion in seawater or exposure to chlorine. Long periods of storage in either damp or occasionally damp areas, particularly on cement floors can also cause premature delaminating, mildew and zipper corrosion.

Never place any backpack in a washing machine as this will cause immediate damage to the PU Coating of your backpack.

Note: Mildew damage and hydrolysis (delaminating) are not covered by the White Mountain™ Lifetime Warranty.

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), mould, 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 the Backpack

Having tested an ironing technique we have found it basically works in arresting the continual delaminating of PU material in a backpack. Use 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.

After treating your backpack to arrest the delaminating of the PU coating we recommend using NIKWAX 'Tent and 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 I used the hair dryer on this as well. All in all an excellent outcome!

Repair Severe Delamination and Reproof Backpack

First remove all the delaminated PU coating. We have found that using a stiff brush on a vacuum cleaner works very well with wholly deteriorated and fully flaking PU coating, and stops the delaminated PU coating from spreading and sticking to everything. Make sure you get under all the seams and thoroughly remove all the delaminated PU coating.

If some of the delaminated PU coating is more persistent and still adheres to the backpack, we have found that wiping with inexpensive white vinegar removes the delaminated PU coating with ease on nylon and polyester material with great success.

With stubborn and difficult to remove PU coating or when removing the PU coating from textured material we have found that using Isopropyl Alcohol is the better option, although this is a more expensive solution. Using a nail brush on textured material is recommended to assist in the removal of PU coating that is difficult to remove, and using a tooth bush in the seams may also make the removal process easier.

Make sure you wipe down the cleaned material thoroughly with a water dampened cloth and leave to dry before reproofing.

After cleaning off all the PU and making sure the backpack material is thoroughly clean and dry apply the NIKWAX 'Tent and 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.

This can be a time consuming process, however with some effort you will restore your backpack to as new condition, and your backpack material should now be as waterproof as it was when new.