Choosing film materials for your product too complicated? You'll understand after reading this!

With the acceleration of industrialization and the enhancement of people's awareness of environmental protection, film self-adhesive materials have developed rapidly. When choosing the most suitable film surface material for an application, companies need to consider many factors, such as material properties, application environment, printing process, and cost.
This article will focus on the key properties of the film and the advantages and disadvantages of some of the more popular film types.
PART 01
Key properties of the film
Key properties of film materials include thickness, gloss, color, haze/optical density, surface energy, shrinkage, tensile strength and elongation, tear resistance, and flexibility. While many of these features sound familiar, some deserve further knowledge.
Surface energy is the molecular force of a thin film substrate interacting with another material. It can indicate how wetted a liquid (such as adhesives, inks, etc.) is on the surface of the material. The surface energy is measured by measuring the wetting tension or contact angle, such as dyne solution in the case of wetting tension and water in the case of contact angle.
Film shrinkage is a measure of the change in the size of a film when heated, usually expressed as a percentage. It is important to note that sometimes the film also undergoes visual changes as it shrinks, which may leave the end user of the product feeling unsatisfactory.
The tensile strength of the film refers to the maximum stress that the film can withstand before it is pulled, in MPa. The elongation of the film and the tensile strength can be measured at the same time, and then the ability of the film to stretch without breaking. For example, 100% elongation means that the film can be stretched to 2 times its original length without breaking.
Film tear resistance refers to the ability of film materials to resist tear damage, and is one of the important indicators to measure the mechanical properties of film films. Tear resistance can be measured in two ways: tear initiation and tear endurance. Tear initiation force measures the force required to start tearing the film, while tear staying force measures the force required to continue tearing the cracks that already exist in the film.
Film flexibility refers to the ability of film materials to bend, stretch and other deformation without rupture when subjected to external forces. The lower the flexibility of the film, the harder the film is and the more difficult it is to conform to the surface.
Film haze (opacity) is an important parameter to measure the optical properties of thin films, which refers to the percentage of scattered light flux and total transmitted light flux in transmitted light that deviates from the direction of incidence by more than 2.5°. The lower the haze value, the closer the film is to glass-like transparency. A higher haze value indicates less light penetrating the film, i.e., higher opacity. The haze value is related to the surface roughness of the film or the internal molecules of the material.
PART 02
Mainstream film application characteristics
PET film: durable goods label
The thickness of this biaxially stretched film ranges from 0.5 mils to 10 mils. PET film usually comes in three types: clear, transparent, matte, and white.
PET film is dimensionally stable at high temperatures, has excellent initial tear and puncture resistance, and is highly 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 that is ideal for applications that require good adhesive wetting. In addition, it has a uniform thickness across the entire coil. It maintains good optical clarity over a wide temperature range, making it ideal for laminated films. In addition, PET is a non-reactive substrate that bonds well with many inks, coatings, and adhesives.
PET film can withstand many harsh environments such as extreme temperatures, humidity exposure, etc., making it ideal for durable goods material tracking labels as well as compliance, product identification and safety/hazard/instruction labels. In addition, it can be used for double-sided window stickers in store windows.
PVC film: outdoor advertising
PVC films range in thickness from 2 mils to 12 mils, making them highly flexible and ideal for applications involving composite curves. PVC is an extremely shaping film that can be easily embossed to create unique textures while also being easy to print.
PVC is generally weather-resistant, making it highly resistant to UV rays and other environmental conditions. As a reliable and durable substrate, PVC is also a popular choice for wall paintings and billboards. However, it is important to note that PVC can become brittle at very low temperatures and soft at extremely high temperatures.
PP film: Consumer product label
PP film is usually available in several types: clear, transparent matte, white or silver (metallized). Like PET, PP film is often stretched in both directions and is highly resistant to chemicals and can come into contact with various contents inside the container.
PP film is widely used in the food industry, such as bags, wrapping paper, and other flexible packaging. PP film is a very economical film. This economies of scale have driven the widespread application of this substrate in the pressure-sensitive label market, particularly as an alternative to paper labels.
PP film can be pre-coated to improve printability. This makes it a popular choice for labeling consumer goods with a labelless appearance, such as food and beverages (especially glass bottles), personal care, household/chemicals, and pharmaceuticals. It is ideal for semi-extruded and rigid containers. PP film is mainly recommended for indoor applications.
PE film: flexible container label
PE film is mainly available in clear, transparent matte and white matte, and also metalized, with thicknesses ranging from 1.5 mils to 4 mils. PE has excellent chemical resistance and can withstand exposure to container contents. It is typically produced through blow molding or casting extrusion processes. Blow molded products are stiffer than cast products, which are non-directional, flexible substrates that are ideal for applications requiring extreme deformation or extrudability.
High-density PE films are generally highly durable, offering excellent stiffness and medium elongation. This makes it relatively easy to dispense, but it tends to have more gel and blemishes compared to the medium-density version. These imperfections can make printing difficult. Currently, suppliers offer many medium/high density hybrids to achieve the best balance between the two.
Special films: customized application scenarios
Special film refers to functional film materials with unique functions, high performance indicators and customized application scenarios, which are different from traditional plastic films. It achieves precise control of environmental factors such as light, heat, water vapor, and oxygen through precision technology and material design, and is widely used in electronics, medical, new energy and other fields.
Polycarbonate (PC) films with excellent optical, mechanical, thermal, and chemical properties, and typical uses include graphic overlays on membrane switches, as well as backlit markers where one side of the logo is exposed to UV light and the other side is exposed to high temperatures due to internal illumination. At the same time, it is also ideal for applications that require repeated operation or continuous use. Instrument panels and dials usually use thicker polycarbonate sheets. In these cases, surface printing is often required and then the graphic is mounted onto the application surface using transfer tape.
Acrylic film has the characteristics of good transparency, weather resistance, flexibility and chemical stability, and can be used in optics, architectural decoration, electronic appliances, medical and other fields.
In summary, when selecting film materials, it is necessary to comprehensively evaluate factors such as label use, environmental requirements, printing process and cost. If high temperature resistance and environmental protection are required, PET film is preferred; If high shrinkage is required, PET film is more suitable; If cost sensitive, PVC film or PE film can be considered; If it is a special application, PC film or acrylic film is more suitable.