When we first started to design the backpack, durability was put in front of everything else, no matter how innovative the idea was. This raised a lot of challenges during the design process, especially when it comes to the fabric choice. There are so many fabrics out there, made of different materials, weave patterns, coating/lamination. All of them have different effects on the fabric characteristics. Let's start with the difference of materials.
Nylon and polyester are both synthetic fabric that commonly used in bag manufacture due to their strong, durable and lightweight characteristics. They are both invented by US DuPont Company. One of the most common fabric used in backpack is 600D Polyester. D stands for denier, which is the unit of measurement to determine the fiber thickness of individual threads or filaments to make the fabrics. Fabrics with a high denier count usually tend to be thick, sturdy, so more durable. However, in order to balance the between weight and durability, lower denier fabric may be used. Of course, prices also differ. Polyester are usually cheaper than Nylon. With similar characteristics, polyester is therefore more popular than nylon. Polyester do have some advantages over Nylon. It is easier to dye, more wrinkle resistant, higher UV resistance than Nylon. Nylon, however is stronger in terms of durability. Codura, which is a highly durable fabric to be used in outdoor products are made of mainly Nylon. Therefore, PU coated nylon has always been the main material in making luxury bags by brands like Gucci and Longchamp.
Therefore, after all, how durable is nylon when compared to polyester and other fabrics? Is Codura very superior? First of all, to define what is durable, it usually comes to two measurements, tearing strength and abrasion resistance.
To start, let's compare the tearing strength. Here is what return from a test result*.
Nylon is stronger than Polyester
The above chart show that 1050D PU coated Nylon can withstand 291.7N force (1N =1kg m/s2), more than double of 600D Polyester. Of course, this doesnt include the difference in weave pattern and also the thickness of coating. However, it shows the difference of tearing strength between Nylon, Polyester and also Canvas, which is also famous for its durability.
Why Codura not stronger?
Surprisingly, Cordura, which is also commonly coated with PU because of their water resistance, has a lower tearing strength than Nylon with the same denier 1050D in this case. it is because it is famous for its durability against abrasion.
How strong is enough?
In general case, 600D polyester is used in most backpacks like school bags and daily backpacks. For military backpack and high quality bags, nylon or Cordura with 900D or above are usually chosen.
Why not PVC?
As PVC is harmful to environment, it is becoming less favorable in bags' industry. Instead PU is commonly used.
Abrasion is another important measurement on the durability of a fabric.
Using Martindale method, after 25600 cycles, 600D Polyester has moderate abrasion which means it should last for years under normal and fair usage, while 500D Nylon and 1050D Nylon has very slight abrasion, therefore, they can be used in military uses.
Why Polyester is so popular then?
The answer is simple, because polyester is cheaper. 600D Polyester is only half of the price of 500D Nylon. 900D Nylon is even more expensive. However, a 600D polyester is still a strong fabric, so it is used in most of the backpacks you can find in mass market. Big brands like North Face uses different materials in different bags, but you may find backpacks with price between £50-110 are made of 600D Polyester while more expensive and professional gears with price £110-200 are made of 420D/600D Nylon. 900D are rarely used because of their expensive price.
Although Nylon is far more superior than polyester, durability of a fabric and further as a backpack also depends on a lot of details. During the design and prototyping process, we did a lot to find out the best solution. Therefore, it took a year and a half for us to develop Instinct the backpack and the Incubes. From fabric choices to constructions and functions, everything counts. (Note: An extra custom PU backing is added to both fabrics of Instinct Backpack and Incubes to further enhance the durability and water resistance.) The ultimate goal is to create a product not only stylish, but easy to use, innovative to solve problems, and durable to last.