A baby hiking backpack can be built with a combination of waterproof and non-waterproof materials.

    The non-flammable material is the water-resistant polyurethane (PU) and can be used to make any backpack or backpack-type pack that can hold a person up to a moderate level of heat.

    But the waterproof material used in hiking gear is made from the polyureths, polypropylene (PUP) and polyethylene (PE), which are highly flammable and can explode if heated enough.

    The flammability of these materials also makes them prone to catching fire.

    PU is also known as PVC, for PVC pipe.

    The PU material can be found in hiking boots and water-proof backpack bags, but many hikers also opt for a water-repellent hiking pack, which is made of polypropylene (PP), a flexible polyester made from cellulose fibers, that is resistant to water and heat.

    The downside to a water resistant hiking backpack is that it is heavier than a non-repelling hiking pack and it does not provide the breathability and water resistance of a watertight backpack.

    But, if you can’t afford a water tight hiking pack that will fit in your backpack, then the water resistant backpack is the way to go.

    Pros Waterproof, waterproof backpack bags are not the most comfortable or durable.

    The material is flammably and not water-resistant.

    They are expensive and hard to find.

    They can’t hold up to the same level of exposure as a water proof backpack.

    The materials are hard to clean up.