Today on packaiging markets,transparent PP woven bags become new bright spot as the packaging, customer needs are mainly transparent plastic bag packaging for food, rice, and other granular chemicals or other substances want to see the product from the appearance of the bag.
Production of transparent bags of flat threads, currently mainly in the following:
Drawing using pure grade polypropylene drawing.
Polypropylene with a drawing class, without any additives such as calcium filler produced bags, with a certain degree of transparency. Adjusting the drawing process , if appropriate, also increase in transparency , because good tacticity polypropylene molecular chain, has a strong ability to crystallize, but the crystallization rate is slow, large spherulites are formed easily , especially small amount of extruded, cooled easier to form large spherulites water temperature is high , which will help improve the tensile strength of flat wire. However, the size of the spherulites is larger than the wavelength of light , and the refractive index difference between the larger amorphous region, when faced with light, easy to produce scattered light, so that the transparency of polypropylene is poor, just to meet the needs of opaque woven. Improve the transparency of polypropylene woven polypropylene crystallization method is to reduce the size of the spherulites to improve the uniformity of the crystal type. Therefore, to accelerate the membrane into the water drawing machine speed and reduce the water temperature, which is conducive to accelerate the crystallization rate to increase transparency.
Transparent polypropylene pellets, the pellets because the isotactic high, low ash impurities , a relatively narrow molecular weight distribution and a low content of chloride ions, high transmittance can be obtained . Antioxidants added to the transmittance of the impact is not large, but not join antioxidants occur in daylight woven thermal aging, polypropylene molecular chain scission degradation products, yellow, light transmittance decreased rapidly.However, the film drawing machine to accelerate the speed and reduce the water temperature into the water while reducing the degree of crystallinity, fine grain size, flat strength is reduced, but the film is hard water tank, film is not flat, easily broken wire in silk, drawing also easily broken wires. Therefore, the need to improve the transparency of bags is more difficult.
Transparent polypropylene drawing drawing class.With the increasing market demand for transparent woven bags, woven bags transparency customers have become increasingly demanding , without adding calcium transparency woven pure polypropylene filler material production can not meet the needs of the market, dedicated transparent polypropylene woven markets become a new selling point.