“Polypropylene is made from the polymerization of gas after high temperature cracking of petroleum under the action of catalysts, according to the different film processing methods can be obtained from different performance films, commonly used mainly general-purpose BOPP, matte BOPP, pearl film, heat-sealed BOPP, cast CPP, blow molding IPP, etc.. This article analyzes the printing and bag-making performance of these types of films in detail.
1、General purpose BOPP film
BOPP film is processed so that the amorphous part or part of the crystalline film is stretched in the longitudinal and transverse directions above the softening point, so that the film surface area increases, the thickness is thinned, and the gloss and transparency are greatly improved. At the same time, the mechanical strength, air tightness, moisture barrier and cold resistance are greatly improved due to the orientation of the stretched molecules.
Properties of BOPP film:
High tensile strength, high modulus of elasticity, but low tear strength; good rigidity, outstanding elongation and resistance to bending fatigue performance; heat and cold resistance is high, the use of temperature up to 120 ℃, BOPP cold resistance is also higher than the general PP film; high surface gloss, good transparency, suitable for a variety of packaging materials; BOPP chemical stability is good, in addition to strong acids, such as fuming sulfuric acid, nitric acid has a corrosive effect on it In addition, it is insoluble in other solvents, and only some hydrocarbons have a swelling effect on it; excellent water resistance, one of the best materials for moisture and moisture resistance, water absorption rate <0.01%; poor printability, so the surface must be corona treated before printing, good printing effect after processing; high static electricity, the resin used in the production of film needs to be added to the antistatic agent.
2、Matte BOPP
The surface layer of matte BOPP is designed as a matte layer, which makes the appearance of the texture similar to paper and comfortable to the touch. Matte surface layer is generally not used for heat sealing, due to the existence of matte layer, compared with general-purpose BOPP, has the following characteristics: matte surface layer can play a shading role, the surface gloss is also greatly reduced; matte layer can be used for heat sealing when necessary; matte surface layer is smooth and good, because the surface roughened with anti-adhesive, film rolls are not easy to stick; matte film tensile strength is slightly lower than the general-purpose film, thermal stability is also called ordinary BOPP slightly worse.
3、Pearlescent film
The pearlescent film is made of PP, CaCO3, pearlescent pigment and rubber hood modifier are added and mixed with bi-directional stretching. As the PP resin molecules are stretched during the biaxial stretching process, and the CaCO3 particles are stretched apart from each other, thus forming pore bubbles, so the pearlescent film is a microporous foam film with density around 0.7g/cm³.
PP molecule loses its heat sealability after biaxial orientation, but still has certain heat sealability as rubber and other modifiers, but the heat seal strength is very low and easy to tear, which is often used in the packaging of ice cream, popsicle, etc.
4、Heat sealing BOPP film
Double-sided heat-sealed film:
This film is ABC structure, A and C sides for the heat seal layer. Mainly used as packaging materials for food, textiles, audio and video products, etc.
Single-sided heat seal film:
This kind of film is ABB structure, with A layer as the heat sealing layer. After printing patterns on the B side, it is laminated with PE, BOPP and aluminum foil to make bags, which are used as high-grade packaging materials for food, beverages, tea, etc.
5、Flow-delayed CPP film
Cast CPP polypropylene film is a non-stretch, non-directional polypropylene film.
CPP film is characterized by high transparency, good flatness, good high temperature resistance, a certain degree of flexibility without losing flexibility, good heat sealing properties. Homopolymer CPP has a narrow range of heat sealing temperature and high brittleness, making it suitable for use as a single-layer packaging film.
Co-polymer CPP has a balanced performance and is suitable as the inner layer of the composite film. At present, the general are co-extruded CPP, can make full use of a variety of polypropylene characteristics of the combination, making the CPP performance more comprehensive.
6、Blown IPP film
IPP blown film is generally produced by down-blowing method, PP is extruded and blown in the ring die mouth, immediately after initial cooling by the wind ring, shaped by water emergency cooling, dried and rolled, the finished product is a cylinder film, which can also be cut to become a sheet film. Blown IPP has good transparency, good rigidity and simple bag making, but its thickness uniformity is poor and film flatness is not good enough.
Post time: Jun-08-2023