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Plastic film, especially BOPP and other biaxially oriented film, there is an obvious molecular orientation, in a state of stress concentration, when there is no cut, it is difficult to tear, but once there is a cut, it can be more convenient to tear, so a large number of applications in the market, from biaxially oriented film as the base material of the composite film bag packaging goods, people are usually designed, processed to facilitate the opening of the cut, tear cut at which the seal can be opened more easily.
However, this type of film products, tearing although easier to open, but the crack propagation is irregular, the lack of linearity, open when the crack is irregular, easy to lead to leakage or damage to the contents, so this type of packaging is not the ideal easy to open film bags. A more ideal, functional film aimed at easy tearing needs to consider the following aspects:
(i) the film splits where it is desired to open when opened;
¢Ú the tear propagation force, which should be as small as possible to facilitate tearing while ensuring an effective protection function for the packaged object;
(iii) the line of crack propagation, which should hopefully be in a straight line or close to it. Compared to easy-peel easy-open films, easy-tear easy-open films are currently less commonly used. Examples of easy-to-tear easy-to-open films are as follows.
A, polyethylene plastic easy to tear type easy to open and seal film
The Shanghai Institute of Plastic Products has developed a polyethylene class of easy-to-tear film, which preserves many of the basic features of conventional polyethylene plastic films, but has the characteristic of being able to be torn in both vertical and horizontal directions: the film split is only linear along the longitudinal or horizontal direction. The characteristics of the film are as follows.
1. Good and balanced mechanical properties
The film has good and balanced tensile strength, elongation at break and right-angle tear strength, except for the longitudinal right-angle tear strength which is slightly lower than the national standard for blown polyethylene films for packaging.
2. Excellent tearability
The film has good tearing properties, it is easy to tear in the longitudinal or transverse direction, and the crack propagation is strong and regular, all appearing as a straight line; and the crack only propagates along the longitudinal or transverse direction of the film and does not expand in other directions. The longitudinal and transverse tear propagation forces (3.32 N/mm and 25.5 N/mm respectively) measured by ISO 6783/1983E Part I (trouser method) are much lower than the longitudinal and transverse tear propagation forces of the comparative PE film (49.9 N/mm and 90.3 N/mm respectively), which is convenient for application.
3. Good moisture resistance
The film has good moisture resistance, with a moisture permeability of 23.79g/(m©O-d) (film thickness of 0.036mm), which is roughly equivalent to the moisture permeability of the pure PE blown film of the comparison sample of 19.30g/(m©O-d) (film thickness of 0.039mm), and can be used for packaging of goods requiring moisture resistance.
4. Good hygiene
The easy-tear film has good hygienic properties and can meet all the requirements of food packaging for the hygienic properties of PE film. In addition to the above, the easy-tear film is "end-tearable" and can be torn even where there is no cut. The film is printed using common production plastic printing equipment and common polyethylene inks, under the same production process conditions as common PE films, to produce a strong print. In addition, the easy-tear film has good heat sealing properties and can be heat sealed with a common sealing machine, so it has good practical value. It can be used on its own or in combination with BOPP to produce tearable laminated films.
5. Contact transparency
This easy-tear film has poor transparency and is only contact transparent, so it is not suitable for use in situations where highly transparent packaging is required, but for products that require light-proof packaging, it is advantageous to use this film in combination with aluminium foil or aluminised-BOPP film for sealing film bags.
Nanjing Sumino Precision Machinery Co., Ltd. has professional cast film production lines, the company's main cast film manufacturing lines are: TPU hot melt film production line, CPP/CPE cast film production line, EVA solar encapsulation film production line, PE hygiene breathable film production line, PVDF cast film production line, PP three-dimensional film production line, medical blood purification film production line, multi-layer co-extrusion barrier film production line, LLDPE winding film production line, etc.
However, this type of film products, tearing although easier to open, but the crack propagation is irregular, the lack of linearity, open when the crack is irregular, easy to lead to leakage or damage to the contents, so this type of packaging is not the ideal easy to open film bags. A more ideal, functional film aimed at easy tearing needs to consider the following aspects:
(i) the film splits where it is desired to open when opened;
¢Ú the tear propagation force, which should be as small as possible to facilitate tearing while ensuring an effective protection function for the packaged object;
(iii) the line of crack propagation, which should hopefully be in a straight line or close to it. Compared to easy-peel easy-open films, easy-tear easy-open films are currently less commonly used. Examples of easy-to-tear easy-to-open films are as follows.
A, polyethylene plastic easy to tear type easy to open and seal film
The Shanghai Institute of Plastic Products has developed a polyethylene class of easy-to-tear film, which preserves many of the basic features of conventional polyethylene plastic films, but has the characteristic of being able to be torn in both vertical and horizontal directions: the film split is only linear along the longitudinal or horizontal direction. The characteristics of the film are as follows.
1. Good and balanced mechanical properties
The film has good and balanced tensile strength, elongation at break and right-angle tear strength, except for the longitudinal right-angle tear strength which is slightly lower than the national standard for blown polyethylene films for packaging.
2. Excellent tearability
The film has good tearing properties, it is easy to tear in the longitudinal or transverse direction, and the crack propagation is strong and regular, all appearing as a straight line; and the crack only propagates along the longitudinal or transverse direction of the film and does not expand in other directions. The longitudinal and transverse tear propagation forces (3.32 N/mm and 25.5 N/mm respectively) measured by ISO 6783/1983E Part I (trouser method) are much lower than the longitudinal and transverse tear propagation forces of the comparative PE film (49.9 N/mm and 90.3 N/mm respectively), which is convenient for application.
3. Good moisture resistance
The film has good moisture resistance, with a moisture permeability of 23.79g/(m©O-d) (film thickness of 0.036mm), which is roughly equivalent to the moisture permeability of the pure PE blown film of the comparison sample of 19.30g/(m©O-d) (film thickness of 0.039mm), and can be used for packaging of goods requiring moisture resistance.
4. Good hygiene
The easy-tear film has good hygienic properties and can meet all the requirements of food packaging for the hygienic properties of PE film. In addition to the above, the easy-tear film is "end-tearable" and can be torn even where there is no cut. The film is printed using common production plastic printing equipment and common polyethylene inks, under the same production process conditions as common PE films, to produce a strong print. In addition, the easy-tear film has good heat sealing properties and can be heat sealed with a common sealing machine, so it has good practical value. It can be used on its own or in combination with BOPP to produce tearable laminated films.
5. Contact transparency
This easy-tear film has poor transparency and is only contact transparent, so it is not suitable for use in situations where highly transparent packaging is required, but for products that require light-proof packaging, it is advantageous to use this film in combination with aluminium foil or aluminised-BOPP film for sealing film bags.
Nanjing Sumino Precision Machinery Co., Ltd. has professional cast film production lines, the company's main cast film manufacturing lines are: TPU hot melt film production line, CPP/CPE cast film production line, EVA solar encapsulation film production line, PE hygiene breathable film production line, PVDF cast film production line, PP three-dimensional film production line, medical blood purification film production line, multi-layer co-extrusion barrier film production line, LLDPE winding film production line, etc.