PET film thinning technology

1. Thinning of the film

Currently used the thinnest PET film thickness of about 0.5 μm, it is much thinner than other films, for example, bi-oriented PP film is 3 μm thick, polycarbonate (PC) film thickness of 2 μm, PE film thickness of 8 μm. Suitable for the production of thinner films is the bi-directional stretching process or solution casting process. The former is suitable for PET and PP films and the latter for PC films. The usual blowing process for blown films and the T-shaped casting die head process are not suitable for the production of very thin films. Roughly speaking, it is quite difficult to produce films with a thickness of 10 μm through the die head gap. Some literature suggests that the plasma polymerisation method, which is characterised by a glow discharge in a monomer gas, is a good way to produce very thin films. However, the production of thinner films by this process is still a detached product at present.

2. Thinning technology

It is very easy to produce PET films with extremely thin thickness trends in the size of a handkerchief. Even some 30 years ago, PET films with a thickness of 1 μm were produced in limited sizes. Of course, such limited sizes cannot be used in industry, and the film has to be wound on a core roll (usually several thousand to tens of thousands of metres long) with a reasonable width and length. This wound film is called - "roll". The development of thinning technology can therefore be described as "the development of film from the size of a handkerchief to a roll".

(1) Stretching process

Stretching is a major factor in the production of thin films. Many patents have been published on stretching methods and conditions.

(2) Accuracy of the machine

The film machine consists of many rollers and other mechanical elements, and it should have high mechanical accuracy.

(3)Sliding property

Good sliding properties of the film are very important for proper machining and disposal of thin films. In order to get good sliding properties, some additives such as inorganic or organic fillers are usually added to the film. However, these additives can sometimes cause the film to break down and lose its electrical and insulating properties. It is usually necessary to choose some wise compromise to overcome these difficulties.

(4) Removal of impurities

Impurities such as dust, carbonised polymers and agglomerates usually cause cracking, porosity and loss of physical properties. Therefore, pure polymers, a clean working environment and a good filtration system are required. Thickness

(5) Film hardness

Since the hardness of the film is related to the cube of the thickness, wrinkles and sagging are very likely to occur in the production of thin films. For this reason, it is desirable to use polymers with high modulus in the production of thin films.PET has a relatively high modulus, which provides an advantage in the manufacture of thin films. The reduction in hardness is also susceptible to static electricity. It is therefore important to prevent the build-up of static charges and to remove them.

(6) Thickness Measurement

The thickness of very thin films is usually measured with a β-measuring instrument using a Pm147 as a β-ray generator. However, the accuracy of this meter is limited to 0.1 μm, which is not sufficient for the measurement of films with a thickness of less than 1 μm. More accurate measurement techniques are now required.

3. Thinning limit

The thinning of PET films is determined by factors such as the molecular structure of the polymer, surface roughness, mechanical properties (ease of handling), dust and impurities, and the final application. By summarising these factors, the practical lower limit of PET film thickness is expected to reach 0.3-0.5 μm in the near future, and 0.025-0.05 μm in the more distant future [58]. Efforts to obtain thinner films will continue, especially for use in capacitors. Recently at an electronics exhibition, a capacitor manufacturer demonstrated ultra-small film capacitors, which consist of 0.65 μm PET film manufactured by Toray, and which are expected to be competitive in size with tantalum electrolytic capacitors and ceramic capacitors.

Nanjing Suminoe Precision Machinery Co., Ltd. is a collection of scientific research, production, sales in one of the high-tech enterprises, and has always adhered to the integrity, equality, the interests of the customer first business philosophy, in order to better improve the quality of the equipment, into a more professional and standardised production track. We set up a plastic sheet, sheet, casting, bi-oriented, non-woven nonwoven meltblown cloth, film composite, renewable granulation and environmental protection recycling system and coating machine manufacturing system and other seven categories of equipment, independent research and development technology centre and production departments, to provide a professional full set of technical solutions to meet the special needs of each customer. Among them, the bi-directional stretch film manufacturing system has: BOPP bi-directional stretch film manufacturing system, PVC bi-directional stretch shrink film production line, PET bi-directional synchronous stretch film production line, BOPA bi-directional stretch film production line, BOPLA bi-directional stretch film production line and so on.