The film is usually made of polyvinyl chloride, polyethylene, polypropylene, polystyrene and

other resin materials, mainly used for packaging and as a coating layer. With the increasing

share of plastic packaging in the market, especially the application of composite plastic

flexible packaging in food, medicine, chemical and other fields has become more and more

extensive. Among them, food packaging is the largest application field, including beverage

packaging, frozen food packaging, cooking food packaging, fast food packaging, etc. These

packaging products greatly facilitate people's lives.

Plastic films made of polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP),

polystyrene (PS), polyethylene terephthalate (PET), polyamide (PA), etc., are widely used in

food, medicine, chemical and other fields of packaging. For example, biaxial polypropylene

film (BOPP) is widely used in the field of printing and packaging because of its high

transparency and good mechanical properties. However, its non-polar surface and high

crystallinity result in low surface free energy, which requires surface treatment to improve

printing performance.

The surface tension of various types of plastic films has its own specific range, which is

determined by the structure and properties of plastic molecules.

The surface tension of plastic film is one of its important physical properties, which directly

affects the secondary processing of ink printing, coating adhesion and bonding with other

materials. In plasma surface treatment, by changing the chemical and physical state of the

plastic surface, the surface tension can be effectively adjusted to adapt to different

application needs. The measurement of surface tension is essential for optimizing these

processes. In the solid state, because the molecules on the surface of the polymer do not

flow, the surface tension is usually determined by indirect methods, such as the Dyne pen

test.

The surface tension of plastic film not only affects its application effect, but also determines

its feasibility in printing, coating and other secondary processing. By understanding the

surface tension characteristics of different plastic films and its influencing factors, the

processing technology can be better selected and optimized to meet different application

needs.

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The surface tension of plastic film is an important physical property, which directly affects

the printability of the film, the adhesion after gluing and the adhesion with other materials.

Different materials of plastic film have different surface tension, which is mainly determined

by their molecular structure. The following is an introduction to the surface tension of

several common plastic films:

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1, polyvinyl chloride (PVC) : PVC film because of its good physical and chemical properties

are widely used in building materials, medical equipment and other fields. Its surface tension

is around 39 dyne/cm, which makes it exhibit good adhesion in processes involving coating

and printing.

Rigid PVC film: This film has high rigidity, good chemical resistance, and is often used in

building materials, outdoor billboards, etc.

Soft PVC film: Soft PVC film is more flexible and can be used to make artificial leather,

document covers, etc.

2, polyethylene (PE) : PE film is a widely used plastic film, with good toughness and water

resistance. The surface tension of PE is usually around 31 dyne/cm. Due to its non-polar

nature, special treatments are often required to improve its surface tension in order to better

adapt to process requirements such as printing and coating.

Low density polyethylene (LDPE) film: This film is extremely flexible and elastic, and is the

softest of all plastic films. Due to its excellent tear resistance and low temperature resistance,

LDPE film is often used in the manufacture of plastic bags, agricultural films and compressed

packaging films.

High-density polyethylene (HDPE) films: HDPE films are harder and more wear-resistant than

LDPE films. It is mainly used to produce stronger plastic bags, such as supermarket shopping

bags and garbage bags, as well as large covering films.

3, polypropylene (PP) : PP film because of its excellent bending resistance and chemical

stability, in the field of food packaging and textile has an important application. It has a

relatively low surface tension of about 29 dynes/cm and often requires corona treatment

or plasma treatment to increase its surface tension to improve printing and coating

performance.

Biaxially stretched polypropylene (BOPP) film: BOPP film is made by biaxially stretched

process, with excellent mechanical properties and gloss. It is widely used in food packaging,

tape, printed labels and other fields.

Casting polypropylene (CPP) film: CPP film is produced by casting process, has good heat

sealing performance and low temperature resistance, often used in snack packaging, textile

packaging and other applications that need heat sealing.

4, polystyrene (PS) : PS film with its excellent electrical properties and transparency is widely

used in the electronics and packaging industry. Its surface tension is similar to PE, about 31

dyne/cm. Although it is not as widely used as other plastic films, in some specific

applications, its unique properties make it the material of choice.

General purpose PS film: It has good chemical stability and electrical insulation, but it is easy

to brittleness and is usually used for packaging and disposable products.

Foamed PS film: This film increases the buffering performance through foaming treatment,

and is often used in packaging materials, such as the buffer layer of express packaging.

5, polyethylene terephthalate (PET) : PET film because of its excellent mechanical properties

and heat resistance, occupy an important position in the plastic bottle and packaging

industry. PET has a high surface tension of up to 46 dynes/cm, which makes it exhibit good

processing properties in a variety of post-treatment processes.

Bidirectional stretch polyester (BOPET) film: BOPET film has excellent strength and

transparency, as well as good gas resistance and fragrance preservation, so it is often used in

food packaging, such as beverage bottles, high-quality packaging films.

Silicon coated PET film: This film is commonly used in the packaging of electronic products,

such as mobile phone screen protection film, because of its special silicon coating, can

provide superior isolation and protection performance.

6, polyamide (PA) : PA film (often referred to as nylon film) is known for its high strength and

good flexibility, and is widely used in food packaging and outdoor sports clothing and other

fields. Its surface tension is similar to that of PET, about 46 dyne/cm, which allows PA films to

maintain excellent performance in complex processing processes.

Nylon 6 (PA6) : Nylon 6 is made of polycaprolactam, has good mechanical properties and

elasticity, easy to process, widely used in the production of clothing, carpets, fishing nets and

ropes.

Nylon 66 (PA66) : Nylon 66 is made of polyhexamethylenediamine adipate, which is

characterized by high mechanical strength, good wear resistance and good heat resistance,

and is often used in automation equipment, motor parts, gears and bearings.

Understanding the surface tension of these plastic films not only helps to select the right

material to meet the specific application needs, but also has important significance for

optimizing the production process and improving the product quality. In practical

applications, through various surface treatment methods, such as corona treatment, plasma

treatment, etc., the surface tension of plastic film can be effectively adjusted to adapt to a

wider range of industrial applications.