Are Woven Polypropylene Bags Waterproof?
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.
The production equipment and process of the first kind of separated inner lining membrane woven bag are relatively simple, the equipment investment is low, and the application is very wide. The inner and outer bags are separated. The inner bag is blown film bag, which can be divided into LDPE and HDPE. The outer bag is ordinary PP woven bag, and the length and width of the inner bag are slightly larger than the outer bag. When loading materials, the inner and outer bags are uneven and easy to be damaged. In the early years, the inner and outer bags of the inner lining membrane bag and the outer bag need to be set together manually, and the inner and outer bags at the mouth of the bag need to be aligned and sewed, so the production efficiency is low, the waste of manpower is large, and the continuous and efficient production cannot be carried out. A skilled operator can only complete about 1000 bags by hand every day, and only about 300 bags can be sewn by hinge sewing machine every day. Nowadays, with the improvement of all-in-one machine, there are many machinery manufacturers in China that can produce all-in-one machines for bag cutting, sewing and lining. The technology has been widely used and tends to be mature, greatly improving the production efficiency.
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.
WHAT IS ARE VALVE BAGS?
Valve bags are packaging bags filled by machines. They come in plastic or paper. Here at Western Packaging, we are a wholesale manufacturer who offers the paper version, with many options. The three main things to consider are size, closure type, and coatings.
CHOOSE THE RIGHT SIZE
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.
Plastic bags were invented in 1967, but only became widely used in stores in the 1970s. The most commonly found thin plastic shopping bag given out at cash registers are usually made of high-density polyethylene (HDPE), but some are made of low-density polyethylene plastic (LDPE).
Once the trees are cut down, the logs are moved to a mill where they can wait up to three years until they dry out. Once ready, bark is stripped off and the wood is chipped into one-inch cubes that are subjected to high heat and pressure. They are then mixed with limestone and sulfurous acid until the combination becomes pulp. The pulp is washed with fresh water and bleach then pressed into paper, which is cut, printed, packaged and shipped. As a result of the heavy use of toxic chemicals in the process, paper is responsible for 70 times more air pollution and 50 times more water pollution than plastic bag production according to a Washington Post analysis, resulting in more toxicity to humans and the environment than HDPE bags. And while 66 percent of paper and paperboard are recycled, the recycling process requires additional chemicals to remove the ink and return the paper to pulp, which can add to paper’s environmental impact.