The tenter method usually belongs to the multi-stage biaxial stretching method, while the double bubble tube film method belongs to the simultaneous biaxial stretching method. One can compare the properties of biaxially stretched nylon film (ONy film), which is a unique situation in which films are produced on a large scale using the aforementioned two film forming methods. This comparison involves tensile properties, impact strength (depending on temperature), heat shrinkage properties, and high-dimensional structures. Using different film forming methods, two samples of nylon 6 were produced when the MD/TD stretch ratio was 3.0/3.2, the thickness of which was a representative 15μm.

It can be seen that the film produced by the multi-stage biaxial stretching method is characterized by higher imbalance in the MD and TD directions compared with the simultaneous stretching method. As expected, the stretching effect in the TD direction in the latter stretching method has an impact on the film. The sample film produced by the simultaneous biaxial stretching method has better impact properties (impact strength), which may be due to the difference in balance characteristics. This balanced orientation has a significant impact on actual strength, which is important in film applications.

The impact strength of the film (depending on temperature) is the shrinkage characteristic. These characteristics become practical. In this respect, heat treatment, such as distillation or boiling treatment, is suitable for sterilizing the food packaged in the film bag. At this time, if the value of the shrinkage ratio on the surface of the film substrate is inconsistent, the film will be deformed, impairing its performance as a pocket.

However, the film produced by the multi-stage biaxial stretching method has inconsistent shrinkage due to the memory of stretching in the TD direction during the production process. The structural identification results of these films also indicate that this characteristic is caused by the inconsistent stretching effects in the MD and TD directions. Wide-angle X-ray diffraction (WAXS) shows that the film produced by the simultaneous biaxial stretching method is characterized by consistent shrinkage, while the film produced by the multi-stage biaxial stretching method has unbalanced shrinkage.

The focus of this research is represented by biaxially stretched films. PP shrink film is one of the typical products produced by the double film wrapped tube film method, and it also shows more consistent performance.

Nanjing Sumino Precision Machinery Co., Ltd. is a high-tech enterprise integrating scientific research, production and sales. It has always adhered to the business philosophy of integrity, equality, and customer benefits. In order to better improve the quality of equipment, it has entered a more professional and standardized Production track. We have established independent research and development technologies for seven categories of equipment including plastic sheet material, casting, bi-stretching, non-woven non-woven meltblown cloth, laminating film composite, recycled granulation environmental protection recycling system and coating machine manufacturing system. The center and production department provide a full set of professional technical solutions to meet the special needs of each customer. Among them, the biaxially oriented film manufacturing system includes: BOPP biaxially oriented film manufacturing system, PVC biaxially oriented shrink film production line, PET biaxially oriented film production line, BOPA biaxially oriented film production line, BOPA biaxially oriented film production line, etc.

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