Study on Surface Modification of Polyethylene Film by Argon/Air Glow Discharge

Use argon/air mixed gas glow discharge to modify the surface of polyethylene (PE) material. Mainly studied the effect of single gas plasma and mixed gas plasma on the surface modification of PE film. The surface properties of PE film before and after treatment were characterized by the contact angle measurement of distilled water and the contact angle of diiodomethane. The changes in energy were analyzed. The experimental results show that the liquid contact angle of the PE film surface treated by glow discharge plasma decreased significantly, and the solid surface energy was significantly increased. Under a fixed voltage and pressure, the water contact angle of the PE film surface increased with the argon/air The increase of the mixing ratio first decreases and then increases, indicating that glow discharge is better than filament discharge in improving the wettability of polyethylene materials. After the treated sample is placed in the air, the water contact angle of the sample surface increases, but it is always smaller than the contact angle before treatment.

Polyethylene (PE) film is a colorless, odorless, odorless, translucent, non-toxic insulating material. It is widely used as packaging bags, food bags, and various containers. However, due to the existence of non-polar groups in the polyethylene chain, its surface wettability is poor, and it has become a typical type of difficult-to-adhesive material. It must be processed to print better results, which greatly limits its use in medical and health care. And other industrial technology applications. To improve the adhesion of these difficult-to-stick materials, surface modification must be performed on them.

In recent years, a lot of research has been conducted on the surface modification of PE materials at home and abroad. The surface modification methods mainly include chemical methods such as chemical oxidation, heat treatment, coupling agent modification, etc., and physical methods such as spraying Sand, polishing, shot peening, filling, blending treatment, etc., there are other mixing methods such as: functionalization treatment, blending modification, laser treatment, plasma modification treatment, etc. As a clean dry process, low-temperature plasma technology has become a commonly used method for surface modification of materials due to its specific environmental and cost advantages. It has great market potential and development prospects. When treated with low-temperature plasma, the high-molecular hydrophobic material will produce corrosion, and the surface roughness of the material will increase, which is beneficial to improve the hydrophilicity. At the same time, polar groups will be introduced into the surface of the treated polymer hydrophobic material, which can increase the surface energy of the material and eliminate the weak interface layer on the surface of the product.

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At present, many researchers have used corona discharge or low-voltage high-frequency radio frequency and microwave electron cyclotron resonance plasma to modify the surface of polymers. However, the corona discharge is not uniform, and it is easy to damage the substrate when modifying the polymer surface, resulting in dents or pinholes on the surface of the processed material. In the glow discharge mode, the product p·d value of the discharge gas pressure and the discharge gap is low, which can form a uniform and stable plasma. Therefore, the glow discharge mode has received more and more attention and research on the surface modification of polymer materials.

In the process of research on the surface modification of materials by glow discharge plasma, a single gas is often used for ionization. In fact, the mixed gas and the ratio of the mixed gas have an influence on the surface modification effect of the plasma material. In this paper, the representative PE film in polymer is taken as the research object. The surface modification effect of the PE film is analyzed by air plasma, argon plasma, and argon/air mixed gas plasma, and the surface modification of the material is given. The relationship between the performance effect and the treatment time, gas pressure, discharge power and other parameters. At the same time, under a fixed discharge power and gas pressure, the influence of the gas mixing ratio on the surface treatment effect of the PE film was studied.

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The glow discharge experimental system used in this article is shown in. The experimental system is equipped with two sets of power supplies. The peak output voltage of the high-voltage AC power supply is 0-30 kV, the frequency is 1-100 kHz, and the power is 0-500 W. The vacuum chamber is connected to a two-stage vacuum system, and the sample is placed on the experimental bench in the vacuum chamber. The discharge voltage and discharge current waveform are measured by the digital oscilloscope Tektronix TDS 1012C-EDU. The discharge gas is a mixture of air and 99.99% argon. During the experiment, the mixing ratio of the two gases is adjusted by a flow meter. The photo was obtained from a digital camera (model: Canon MF4400). The contact angle of the test sample surface was tested with a contact angle tester (model: JGW-360A). The test liquid was distilled water and diiodomethane.

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The PE film is made into a rectangular sheet of 40 mm × 30 mm, and then it is washed in an acetone solution for 12 h, then rinsed with alcohol, and finally placed in an oven to dry. Put the cleaned and dried PE film on the test bench in the vacuum chamber. After the pressure in the vacuum chamber is below 0.1 Pa, argon and air with a purity of 99.99% are passed into the reaction chamber in proportion to meet the requirements Stop ventilation after air pressure. According to the needs of the experiment, adjust different discharge parameters to discharge the PE film, record the corresponding discharge parameters, voltage and current waveforms during discharge, etc. After the discharge is over, the sample is taken out, and the contact angle test is performed on the treated sample with a contact angle tester. The test liquid is distilled water. Each time, 3 different positions of the sample are measured, and then the measured values are weighted and averaged. At the same time, use diiodomethane as the second test liquid to characterize the surface energy of the sample. During the characterization process, the dispersion force and polar force of distilled water used are 52 and 20.9, respectively, and the dispersion force and polar force of diiodomethane are They are 2.5 and 46.9 respectively.

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This paper uses argon/air mixed gas glow discharge to systematically study the surface modification of PE polymer materials. A large-scale uniform glow discharge was realized in the entire vacuum chamber. The effect of single gas plasma and mixed gas plasma on the surface modification of PE film was compared. The surface properties of PE film before and after treatment were characterized by measuring the contact angle of distilled water. At the same time, the contact angle measurement of distilled water and diiodomethane was used to analyze the change of the surface energy of the PE film.

The experimental results show that the liquid contact angle of the PE film surface treated by glow discharge plasma is significantly reduced, and the surface energy is significantly improved. Under a fixed voltage and pressure, the surface treatment effect of the PE film changes with the gas mixing ratio. However, the hydrophilicity of the sample after the glow discharge plasma treatment is gradually weakened after being placed in the air, but its hydrophilicity is better than that of the sample before the treatment.

Founded in 2015,Zunhua Baorui Titanium Equipment Co.,Ltd. is a manufacturer specializing in pvd vacuum ion coating equipment. The company’s products mainly include large plate coating machine, large tube collating machine, tool coating machine and LOW-E glass production line. Mr.Wang baijiang ,general manager of the company ,has been engaged in vacuum coating industry for more than 30 years. He continuously improve production technology, improve product performance and devote himself to provide customers with better product experience and higher production efficiency.