Is Selecting Film Materials for Products Too Complicated? 
Self - adhesive label materials can be divided into paper - based self - adhesive labels and film - based self - adhesive labels according to the face material. With the acceleration of industrialization and the growing environmental awareness of people, film - based self - adhesive materials have developed rapidly. When enterprises choose the most suitable film face material for a particular application, they need to consider many factors, such as material characteristics, application environment, printing process, and cost. This article will focus on discussing the key properties of films, as well as the advantages and disadvantages of some popular types of films.

Key Properties of Films

The key properties of film materials include thickness, gloss, color, haze / optical density, surface energy, shrinkage rate, tensile strength and elongation, tear resistance, and flexibility. Although many of these properties sound familiar, some are worth further understanding.
•  Surface energy is the molecular force of interaction between the film substrate and another material. It can indicate the degree of wetting of liquids (such as adhesives, inks, etc.) on the material surface. Surface energy is measured by wetting tension or contact angle. For example, in the case of wetting tension, the test is conducted with dyne solution, while in the case of contact angle, water is used for testing.
•  Film shrinkage rate is an indicator of the dimensional change of the film when heated, usually expressed as a percentage. It should be noted that sometimes the film may also undergo visual changes during shrinkage, which may make the end - user of the product feel that the appearance is not satisfactory.
•  Film tensile strength refers to the maximum stress that the film can withstand before being pulled apart, with the unit being MPa. Film elongation can be measured simultaneously with tensile strength, thereby determining the film’s ability to stretch without breaking. For example, an elongation of 100% means that the film can stretch to twice its original length without breaking.
•  Film tear resistance is the ability of the film material to resist tearing and is one of the important indicators of the mechanical properties of the film. Tear resistance can be measured in two ways: tear initiation force and tear propagation force. Tear initiation force measures the force required to start tearing the film, while tear propagation force measures the force required to continue tearing an existing crack in the film.
•  Film flexibility refers to the ability of the film material to undergo bending, stretching, and other deformations without breaking when subjected to external forces. The lower the flexibility of the film, the harder it is, and the more difficult it is to adhere to curved surfaces.
•  Film haze (opacity) is an important parameter for measuring the optical properties of the film. It refers to the percentage of the scattered light flux, which deviates from the incident direction by more than 2.5° in the transmitted light, compared to the total transmitted light flux. The lower the haze value, the closer the film is to glass - like transparency; the higher the haze value, the less light passes through the film, that is, the higher the opacity. The haze value is related to the surface roughness of the film or the internal molecular structure of the material.

Mainstream Film Application Characteristics

01 PET Film: Durable Goods Labels

The thickness of this biaxially oriented film ranges from 0.5 mil to 10 mil. PET film is usually available in transparent, transparent matte, and white.
PET film is dimensionally stable at high temperatures and has excellent initial tear and puncture resistance, making it durable. It also has good heat and chemical resistance. PET film can also be pre - coated to improve printability.
PET film is produced to extremely high standards and is a very smooth substrate, making it ideal for applications that require good adhesive wetting. In addition, it has uniform thickness across the entire roll. It maintains good optical clarity over a wide temperature range and is an ideal choice for over - laminating films. Moreover, PET is a non - reactive substrate that can bond well with many inks, coatings, and adhesives.
PET film can withstand many harsh environments, such as extreme temperatures and humidity exposure, making it an ideal choice for durable goods tracking labels, as well as compliance, product identification, and safety / hazard / instruction labels. In addition, it can also be used for two - sided window decals in store windows.

02 PVC Film: Outdoor Advertising

The thickness of PVC film ranges from 2 mil to 12 mil and has a high degree of flexibility, making it suitable for applications involving compound curves. PVC is a very moldable film that can easily be embossed to create unique textures and is also easy to print.
PVC usually has good weather resistance and is highly resistant to ultraviolet light and other environmental conditions. As a reliable and durable substrate, PVC is also a popular choice for murals and billboards. However, it should be noted that PVC becomes brittle at extremely low temperatures and softens at extremely high temperatures.

03 PP Film: Consumer Goods Labels

PP film is usually available in transparent, transparent matte, white, or silver (metallized). Like PET, PP film is often biaxially oriented and has strong chemical resistance, allowing it to come into contact with various contents inside the container.
PP film is widely used in the food industry, such as bags, packaging paper, and other flexible packaging. PP film is a very economical film. This economy of scale has driven the widespread application of this substrate in the pressure - sensitive label market, especially as a substitute for paper labels.
PP film can be pre - coated to improve printability. This makes it a popular choice for no - label - look consumer goods labels, such as food and beverages (especially glass bottles), personal care, home / chemicals, and pharmaceuticals. It is very suitable for semi - rigid and rigid containers. PP film is mainly recommended for indoor applications.

04 PE Film: Flexible Container Labels

PE film mainly comes in transparent, transparent matte, and white matte, and also has metallized versions, with thickness ranging from 1.5 mil to 4 mil. PE has excellent chemical resistance and can withstand exposure to container contents. It is usually produced by blow - molding or cast - extrusion processes. Blow - molded products are harder than cast products, while cast products are a non - oriented, flexible substrate, making them ideal for applications requiring extreme deformability or squeezability.
High - density PE film is usually very durable, with excellent stiffness and moderate elongation. This makes it relatively easy to dispense, but compared to medium - density versions, it often has more gels and flaws. These flaws can make printing very difficult. Currently, suppliers offer many medium - density / high - density blended products to achieve the best balance between the two.

05 Specialty Films: Customized Application Scenarios

Specialty films refer to functional films with unique functions, high - performance indicators, and customized application scenarios, which are different from traditional plastic films. Through precision processes and material design, they can precisely control environmental factors such as light, heat, water vapor, and oxygen, and are widely used in fields such as electronics, medical care, and new energy.
Polycarbonate (PC) film has excellent optical, mechanical, thermal, and chemical properties. Typical applications include graphic overlay on membrane switches and backlit identification, where one side of the identification is exposed to ultraviolet light and the other side is exposed to high temperatures due to internal lighting. It is also very suitable for applications that require repeated operations or continuous use. Dashboards and dials usually use thicker polycarbonate sheets. In these cases, surface printing is usually required, and then transfer tape is used to install the graphics onto the application surface.
Acrylic film has good transparency, weather resistance, flexibility, and chemical stability, and can be applied in fields such as optics, architectural decoration, electronics, and medical care.

In summary, when selecting film materials, it is necessary to comprehensively evaluate factors such as label usage, environmental requirements, printing processes, and cost. If high - temperature resistance and environmental friendliness are needed, PET film should be prioritized; if high shrinkage is required, PET film is more suitable; if cost - sensitive, PVC film or PE film can be considered; for special applications, PC film or acrylic film is more appropriate.