What Makes a Backpack Durable?

When we think about high-performance pack fabrics, the woven textile usually gets most of the attention: nylon or polyester, denier, weave structure, and weight. But there’s another critical component that often goes overlooked: the coating. When applied to fabric, it is a thick, white liquid resin. The coating is then spread and pressed into the fibers using a knife blade or heavy rollers. Most of the coating volume at this stage is the solvent (the carrier of the coating). As it dries, the carrier evaporates off, leaving just a thin clear film on the fabric. 

A fabric is only as tough as its coating!

So let's dive into what these coatings do for the backpack. 

One of the most important roles of your pack is to keep your things dry. Manufacturers have developed a test that displays the level of water resistance. It’s called a hydrostatic head test. It tells you how many millimeters of a vertical water column the piece of fabric can hold before leaking. Whether you’re in heavy rain or placing your bag on wet ground, the bag should hold strong. A reliable bag should typically have a hydrostatic resistance of at least 3,000 mm, while high-performance bags can reach 10,000 mm or more. However, this test method has come under much scrutiny by users. Typically, bags don't wet out because of concentrated water pressure, but rather lengthy exposure to lighter pressure, like rain. Regardless of this fact, the industry chooses to keep hydrostatic head as its test of choice.

Hydrostatic head test (mm-H2O)AATCC 127

Punctures are another common failure point in backpacks, with everything from sharp gear to rough environmental conditions contributing to holes and tears in the fabric. The measure of this type of fabric strength is called puncture resistance. It tells you how many pounds of force a point in the fabric can withstand. To perform this test, a swatch of fabric is held tight between metal plates. A steel probe with a sharp tip is then aligned over the center of the fabric and slowly pushed downward at a precise speed. The pushback is then measured until the fabric gives. Standard outdoor use gear typically lies within the 30-100 Newton range for puncture resistance. The tip used for this test can differ between test methods, so be aware of this when comparing results. 

ASTM D7513

Not all holes come from a single sharp object. Some develop through abrasion, as the fabric repeatedly rubs against the ground, rocks, branches, and other rough surfaces. Over time, this friction can cause color degradation and gradually thin the fabric. This is a silent killer, as thin fabric is more susceptible to both water leaks and complete wear-through.

The test method used to measure abrasion resistance is the Taber test, where the fabric is secured between metal plates beneath a rotating arm fitted with abrasive wheels. Once the test begins, the arm is lowered onto the fabric with a specific weight and constantly rubs the fabric in a circular motion until failure. Again, use caution when comparing test results, as different test methods use different amounts of weight, different grits of sandpaper, and even different definitions of failure. 

The Taber Test ((Cycles) ASTM D3389 H-18 1KG SP:65) results shown here were conducted on the same fabric using the same number of abrasion cycles. The only variable is PolyCore’s Eco-Coating, which increases fabric abrasion resistance by up to 500%, setting a new benchmark for durability and long-term performance.

Together, these three tests give us a great start to practically measure a fabric’s durability.

Durability is greatly increased by the addition of a coating on fabric. Unfortunately, the solvent carriers that are used to apply coatings, such as DMF (Dimethylformamide) and toluene, are classified as CMR solvents. This means that when they evaporate, they release toxic fumes which are carcinogenic, mutagenic, or reprotoxic.

But there is a solution. Advanced materials and chemical innovations have given birth to a new type of coating. Waterborne coatings. 

Waterborne coatings use water as the primary carrier instead of relying on large quantities of organic solvents. This shift can dramatically reduce VOC emissions and worker exposure to hazardous chemicals during manufacturing while maintaining, and in some cases improving, the performance expected from technical textile coatings.

The result is a safer, lower-impact pathway to achieving the durability, water resistance, and performance required for demanding outdoor products.

The moral? Next time you buy a backpack, give some credit to the coating! Check the product description to see if the brand gives any insight into any of these three mechanical tests.