How to choose the coating material of PP/PE woven fabric?

In PP and PE extrusion coating process,coating material is needed to be more stringent than which of yarn extrusion process, bad choice of raw materials, lack of liquidity and will produce insufficient peel strength. Thus, the choice of raw materials to pay attention to the performance of the following points:
a) Need nice flowing propertiesGood flowability to a uniform film thickness of the coating is uniform. Because of the longer die coating, in particular coated on both sides at once folded length of die head, double head, with a die width tarpaulin, the material in the die of the melt flow a longer distance through a relatively long time, resistance in the die is large, a good resin flowability is not selected, it will cause uneven thickness of the film , the flow rate range, the die lip temperature is not such , there will be a partial loss of viscoelasticity cooling, and braid cloth adhesive is not strong. Flowability index is a measure of the melt index M1, generally speaking, the polyethylene is 4-15g/10min, polypropylene is 7-30g/10min.
b) Need high melt strengthMelt flowing out from the die to have a certain viscoelasticity, that is higher melt strength. As the melt cast into the distance is a woven traction stretching process, there is some traction ratio, it requires a certain degree of melt strength to pull off without being pulled or broken. The distance from the mold woven mouth, because inertia weight and traction speed die due to reasons, the melt flow properties can not be good, in order to avoid uneven vertical thickness of the film or the heap , so the resin melt index can not too high. A melt index of polypropylene material used for flat yarn is approx value 2~6g/10min, it is inappropriate for the coating, the flow is too slow, prone to the phenomenon of uneven thickness.
c) Need good thermal stabilitySince the coating is carried out under high temperature conditions, the extrusion temperature is typically about 290 higher than yarn extrusion material. Melting the resin coating material in contact with air during the film, the surface oxidation reaction of a carbonyl group, to increase the adhesion capability. However, the high temperature causes the polyolefin resin, particularly polypropylene, thermal aging. And thus to choose a good thermal stability of the resin.
Types of coating materials market is currently more. Divided into two categories according to the type of raw materials, mainly are PP and PE. In principle, the substrate should be selected PP polypropylene woven material for the coating, the substrate is a woven polyethylene PE coating material should be selected. According to the production process can be divided into homopolymers and copolymers. Domestic material coated with homopolymers based. Currently, due to the different coating materials and the second substrate, the coating material on the functional requirements are different, so we had to blend modified based special coating material. Special coating material, although the scope is small, but highly targeted, can be applied to substrates coated with specific characteristics and access it needs. Such as low temperature coating materials, and anti-aging materials.