There are waterproof backpacks for shoulders, rock climbing backpacks, 40L, 1000D pvc mesh, standard professional carrying system ~ waterproof backpacks are rarely used professionally, so it is worth a look.
There is also a 420d backpack with a capacity ranging from 18 to 35L that fits tpu. The above waterproof level is international ipx7. Knapsack waterproof knowledge: the traditional waterproof backpack, the traditional one is to add some small repairs on the basis of the sewing bag, such as increasing the coating in the fabric, and adding glue on the zipper. In fact, it can't prevent water. This is rainproof. Or water-repellent level, if moderate or heavy rain, a rain cover must be added. The main problem is that the material and the bag mouth cannot be waterproof for a long time-this is a low-level waterproof backpack, in fact, the waterproof level is ipx3-4. Mid-end waterproof backpack, this kind of backpack is a roll pocket, no longer a zipper pocket, relying on the physical extrusion of the roll to achieve the purpose of sealing after folding, its waterproof performance is about 1-5 meters deep and 30 minutes waterproof level, ipx6- Level 7.
Although the tpu laminated cloth or pvc mesh material is used, the waterproof problem of this backpack is that the bag mouth cannot be compressed for a longer time. Because the bag is constantly deformed by external forces during use, the curling mouth exists. Larger risk of loosening. High-end waterproof backpack, airtight zipper pocket, relying on advanced airtight zipper sealing technology to achieve the goal of waterproofing.
The material is a double-sided adhesive film tpu laminated cloth, and the zipper is airtight, which basically solves the pain points of the above two waterproof backpacks, and the waterproof level can reach ipx8.