Six types of polypropylene film
1. General-purpose BOPP film
BOPP film is to make the amorphous part or part of the crystalline film stretched in the vertical and horizontal directions above the softening point during processing, so that the surface area of the film is increased, the thickness is reduced, and the gloss and transparency are greatly improved. At the same time, due to the orientation of the stretched molecules, its mechanical strength, air tightness, moisture barrier, and cold resistance have been greatly improved.
The characteristics of BOPP film: high tensile strength, high elastic modulus, but low tear strength; good rigidity, outstanding elongation and bending fatigue resistance; high heat and cold resistance, and the use temperature can be as high as 120 ℃, The cold resistance of BOPP is also higher than that of general PP film; the surface gloss is high, the transparency is good, and it is suitable as a variety of packaging materials; BOPP has good chemical stability, and it is insoluble except for strong acids, such as fuming sulfuric acid and nitric acid, which have corrosive effects on it. Compared with other solvents, only some hydrocarbons have a swelling effect; it has excellent water resistance and is one of the best materials for moisture and moisture resistance. The water absorption rate is less than 0.01%; the printability is poor, so surface corona treatment must be carried out before printing, and after treatment The printing effect is good; the static electricity is high, and the antistatic agent should be added to the resin used to produce the film.
2. Matte BOPP
The surface layer of the matte BOPP is designed as a matte layer, which makes the appearance of the texture look like paper, and the hand feels comfortable. The matting surface layer is generally not used for heat sealing. Due to the existence of the matting layer, compared with general BOPP, it has the following characteristics: the matting surface layer can play a role in shading, and the surface gloss is greatly reduced; the matting layer can be used as a heat cover if necessary; the matting surface layer The smoothness is good, and the film roll is not easy to stick due to the rough surface. The tensile strength of the matting film is slightly lower than that of the general film, and the thermal stability is also slightly worse than that of ordinary BOPP.
3. Pearlescent film
Pearlescent film is made of PP as raw material, adding CaCO3, pearlescent pigments, and rubber modifier, and then biaxially stretched after mixing. In the process of biaxial stretching, the PP resin molecules are stretched, and the CaCO3 particles are stretched to open the distance between each other, thereby forming pores, so the pearl film is a microporous foam film with a density of 0.7g /cm³. The PP molecule loses its heat-sealability after biaxial orientation, but it still has a certain heat-sealability as a modifier such as rubber, but its heat-seal strength is very low and it is easy to tear. It is often used in the packaging of ice cream and popsicles.
4. Heat-sealing BOPP film
Double-sided heat-sealing film: This film has an ABC structure, and both sides of A and C are heat-sealing layers. Mainly used as packaging materials for food, textiles, audio-visual products, etc.
Single-sided heat-sealable film: This film is of ABB structure, and layer A is the heat-sealable layer. After printing the pattern on the B side, it is compounded with PE, BOPP and aluminum foil to make a bag, which is used as high-end packaging materials such as food, beverage, tea and so on.
5. Cast CPP film
Cast CPP polypropylene film is a non-stretched, non-oriented polypropylene film.
CPP film is characterized by high transparency, good flatness, good high temperature resistance, a certain degree of stiffness without losing flexibility, and good heat sealability. Homo-CPP has a narrow heat-sealing temperature range and high brittleness, so it is suitable as a single-layer packaging film, and copolymerized CPP has balanced properties and is suitable as an inner layer material of a composite film. At present, CPP is generally co-extruded, which can make full use of the characteristics of various polypropylenes to combine to make the performance of CPP more comprehensive.
6. Blow molding IPP film
IPP blown film is generally produced by down-blowing. After PP is extruded and inflated at the annular die, it is quickly cooled by water after preliminary cooling by the wind ring, and then is rolled up after drying. The finished product is a cylindrical film. Cut into a film. Blow-molded IPP has good transparency, good rigidity, and simple bag making, but its thickness uniformity is poor, and the film flatness is not good enough.
