BOPE film is a kind of high-performance film material which is made of polyethylene resin with special molecular structure as the raw material and flat film method biaxial stretching technology. After the BOPE film is stretched and formed, each performance has been greatly improved. Sinopec North Chemical Research Institute, through the study of raw material molecular structure design and film stretching technology, has developed the first BOPE special material with both high draw ratio and draw rate in China.
The special material can be produced on the existing BOPP double-pull production line, which fully satisfies the requirements of the production line for the stretching and film forming of the raw material, which also makes it possible for large-scale industrial production and application of BOPE.
Film Formation Mechanism
In terms of mechanism, the development of BOPE special materials is based on the molecular structure of polyethylene raw materials, combined with advanced double-drawing processing technology to produce a class of high-performance film, the traditional PE film is through extrusion blow and extrusion Casting process molding, blow molding and casting is a kind of melt processing, so the forming process is in an unsteady state, but the BOPE film is formed by the flat film method like BOPP stretching, that is, after the extrusion molding. After the slab has been preheated for a second time and then stretched, it is stretched to form a film in a semi-solid state. Relatively speaking, the forming process is a steady state structure. Therefore, the degree of orientation of the film is high, and particularly, the uniformity of the thickness is relatively good. However, the existing polyethylene raw material does not have the desired molecular structure and cannot be biaxially stretched.
The advantages of BOPE film
Due to its high orientation and molecular weight orientation and crystal orientation, excellent impact resistance and puncture resistance, the puncture strength is probably increased by 2-5 times, and the deformation is particularly small after impact.
With higher tensile strength, the strength is 2-8 times higher than the existing blown film. Both directions can reach 100Mpa or more.
After BOPE is casted and then stretched, the casting process is a rapid cooling process, and the crystal structure is relatively fine, so the optical performance is good, and the film haze is reduced by 30% to 85%, so it has very excellent optical properties.
Flat film stretching has good thickness uniformity, which is suitable for high-speed printing and high-speed recombination. BOPE film also has certain tearability.
In summary, BOPE film has these advantages. In packaging applications, due to its excellent anti-pinhole performance, low temperature impact and puncture resistance, it can effectively reduce the package breakage rate and reduce costs for manufacturers.
BOPE film application
At present, BOPE film has been applied in the fields of daily chemical packaging, food packaging, and agricultural film, and has achieved certain results. The BOPE film applications that have been developed include heavy-duty bags, food packaging, composite bags, daily chemical bags, white film, and the like.
Among them, the application of BOPE composite bag is relatively successful. It is mainly based on BOPE as a layer through composite as packaging material. The packaging material possesses features such as spur resistance, impact resistance, high strength and low temperature resistance. As BOPE’s high strength provides the possibility of thinning packaging materials, thinning existing packaging, increasing package strength can reduce package breakage, reduce packaging waste, and reduce costs. We believe that reducing the amount of plastic and thinning It can also be used as a more practical packaging green technology.
1 Development of BOPE heat seal film: According to the application of BOPE heat seal film in the field of packaging materials, the requirements of the film sealing temperature, heat seal strength, etc., the film heat seal layer was designed, and the film stretch process was optimized. A BOPE heat sealable film with a single-side heat seal layer and a double-sided heat seal layer structure has been developed. At present, the heat-sealing film developed has a relatively high heat-sealing strength, reaching a maximum of 20N.2 In terms of BOPE composite heavy-duty bags, BOPE film was used as the inner layer, composite nylon or PET or BOPP, and BOPE was used as the inner layer to replace the existing relatively thick PE film. We have successfully replaced the existing 110um with 50um BOPE film. PE composite film bags made by PE blown film.
By comparing the performance of BOPE composite repacking, we can see that for the two key indicators of tensile strength and puncture strength, the structural composite package with 30um BOPE composite 15um BOPA has reached even its tensile strength and puncture strength Ultra-large 105um blown film composite structure of 15um BOPA, so the packaging strength has greatly improved.
3 In terms of food packaging, BOPE film still maintains good anti-low temperature performance of PE resin, the glass transition temperature can reach minus tens of degrees, so BOPE film maintains good impact at low temperature and pinhole resistance, so it can effectively reduce Low temperature food package. By comparing the low-temperature impact properties of BOPE film and existing packaging, it can be seen that the impact strength of 30um BOPE film at a low temperature of minus 30°C can achieve the strength of the food packaging prepared by the existing 90um PE blown film. Therefore, the BOPE film is used for freezing. Meat and seafood have certain advantages.4 Bag making: BOPE is used as the inner layer to prepare high-strength packaging bags to replace the existing more expensive BOPA film. BOPE film can replace BOPA in existing packaging because of its strength and high resistance to puncture and impact. Thin film, to ensure the performance of the bag body, significantly reducing the cost of packaging.
For this application, we probably have two designs. One is BOPE as the middle layer, and the other material is made up and down to make a high-strength, puncture-resistant bag instead of some middle layer BOPA. The other is not to block. Under the application, using BOPET/BOPE structure instead of BOPA/IPE (CPE) structure not only reduces cost instead of nylon, but also achieves a certain thinning effect, and has the easy tearability that existing IPE does not have.
5 Environmental green application: At present, it is more realistic to use BOPE as the outer layer and CPE or PE blown film as the inner layer and composite all-PE packaging bag. BOPE provides puncture resistance and tensile strength, and thus the prepared packaging bag is environmentally friendly. , easy to recycle, the same material at the same time feel soft and difficult to scratch, etc., can be used in the washing powder packaging maternal and child supplies, etc., in addition to efforts to develop BOPE aluminum film, matte film, and even high shrink film BOPE.
BOPE film properties
Mechanical properties: Above the BOPE and PE blown film tensile curves, the existing PE blown film tensile yield at very low strength, about 10-20Mpa yield, breaking strength 30-50Mpa, but because of processing characteristics of BOPE, processing During the forming process, BOPE has almost no yield, and the breaking strength can reach more than 100Mpa. Moreover, the elongation and BOPA and BOPET have a good match, and they have a good synergistic effect after being compounded into packaging materials.
The impact properties of blown film and BOPE film are compared: the impact strength of ordinary PE blown film is relatively low, or the impact deformation is relatively large, but the BOPE film has less impact deformation and does not affect the secondary use of the packaging material completely without breaking.
Demonstration of BOPE optical performance: Due to advanced processing technology, BOPE film has lower haze and better light transmittance, and it can be seen that the 60um BOPE film has better light transmittance.
Currently BOPE special materials developed by Beihua Institute can be produced industrially. At the same time, with the help of Sinopec downstream customers and partners, BOPE film can already be mass-produced industrially. The developed BOPE industrial product 16-55um film, 25um-55um single-sided Heat seal film, 25um, 35um double-sided heat seal film, 25-35um self-adhesive film, etc., more applications are under development.
Show BOPE film industrial products performance: comparison shows that BOPE main performance indicators, tensile strength, puncture strength, haze, impact strength than the existing blown film PE have a greater improvement, 35um BOPE film strength can be The strength of the 105um PE blown film is higher than that of the existing metallocene, so it should have a good application prospect as a new packaging substrate.