Are pp woven bags waterproof? As far as the woven bag itself is concerned, because the woven bag is made of warp and weft tapes, there is only overlap between the tapes, which does not have sealing property. Therefore, the liquid will be left through the gap between the tapes, so the woven bag itself is not waterproof.
However, due to the special requirements of chemical industry, cement, chemical fertilizer, sugar and other industries for packaging, a considerable number of plastic woven bags must have the function of waterproof and sealing. At present, there are mainly two types of waterproof and sealed woven bags produced and applied in the market: one is the ordinary separate combined packaging bag with outer woven bag and inside liner inserted or stitched bag. The other is the composite woven bag coated with a layer of plastic film on the PP woven cloth, which will include two types also, either polypropylene coated woven bag or pp woven laminated bag.
Another kind of Coated plastic woven bag production must go through the coating process, using the extrusion coating machine to coat a layer of plastic film with a thickness of about 0.02 ~ 0.04mm on the outside of the woven pp cloth. Or at the same time, to use the coating material as the bonding medium, and then composite a layer of BOPP film on the surface, can achieve better waterproof effect, it was named BOPP pp woven laminated bag. When doing coating, the temperature of the extruded film is about 300 ℃, and the newly extruded film is combined with the braid by a pair of cooling rollers. However, such high temperature reduces the strength of the cloth surface, reduces the elasticity, increases the brittleness of the bag surface, and makes the bag easier to be damaged in the falling tests.Paper valve bags come in a large range of sizes. We offer small to very large paper valve bags and multiple sizes in between. It is important to verify which sizes your valve bag machine handles.