The static biaxial stretching test was conducted on the nylon/EVOH co-extruded film (ABA three-layer structure) using the Film Biaxial Stretching Machine from POTOP Co., Ltd. The test target was set to stretch the material to a thickness of 15 microns, and the results showed that the film had excellent stretching performance, no obvious defects and good transparency.
I. Material Properties: Synergistic Barrier and Mechanical Advantages of Nylon and EVOH
Nylon (PA) and Ethylene-Vinyl Alcohol Copolymer (EVOH) are the core material combination for high-barrier co-extruded films:
• Nylon: It has both high mechanical strength (excellent tensile strength and elongation at break), good heat sealability and transparency. It is often used as the support layer or barrier layer of co-extruded films, providing the film with basic mechanical support and the performance of blocking oxygen and water vapor.
• EVOH: Its barrier performance can be flexibly adjusted with ethylene content. It is the preferred barrier layer material for aseptic food packaging, which can effectively block oxygen and oils. In addition, it has excellent mechanical strength, wear resistance and cold resistance, and has excellent affinity with nylon. No additional adhesive layer is needed during co-extrusion, ensuring the stability of interlayer bonding.
In the ABA three-layer structure, nylon and EVOH are compounded by co-extrusion technology, which not only exerts the mechanical support of nylon, but also utilizes the barrier properties of EVOH, realizing the performance synergy of "barrier + mechanics" and providing a material foundation for film stretching.
The static biaxial stretching test was conducted on the nylon/EVOH co-extruded film (ABA three-layer structure) using the Film Biaxial Stretching Machine from POTOP Co., Ltd. The test target was set to stretch the material to a thickness of 15 microns, and the results showed that the film had excellent stretching performance, no obvious defects and good transparency.
II. Process Key Points: Parameter Control and Equipment Adaptation
The static film biaxial stretching process was adopted in this test, and the key process parameters and equipment adaptation logic are as follows:
• Temperature Control: The temperature must accurately match the material melting characteristics (the difference in melting temperature between nylon and EVOH is small; stretching at 80℃ can avoid material fogging caused by overheating, which affects transparency, while ensuring fluidity during stretching).
• Stretching Ratio and Speed: Balance stretching efficiency and material stress through "low ratio + moderate speed" to avoid film cracking or defects caused by excessive stretching speed.
• Width and Wind Speed: Wind speed adjustment can assist film cooling and setting to ensure thickness uniformity after stretching.
• Preheating Time: Set preheating time to fully activate material molecular chains and reduce the risk of stress concentration during stretching.
At the equipment level, the film biaxial stretching machine needs to accurately control parameters such as temperature, speed and ratio, and optimize the process window according to material characteristics (e.g., the temperature should not be too high, and the clamp temperature should match the material melting characteristics) to ensure that the film thickness meets the standard and has no defects after stretching. The static biaxial stretching test was conducted on the nylon/EVOH co-extruded film (ABA three-layer structure) using the Film Biaxial Stretching Machine from POTOP Co., Ltd. The test target was set to stretch the material to a thickness of 15 microns, and the results showed that the film had excellent stretching performance, no obvious defects and good transparency.
