The use of PVC shrink labels is diminishing due to environmental concerns. PVC is not eco-friendly. PETG, with its superior shrinkage rate and performance compared to PVC, has become the better choice. PETG shrink labels boast a shrinkage rate of around 75%, reaching up to 80%. It is more and more popular for uniquely shaped bottles.
Shrink film labels, it has the form of shrink sleeves or shrink-wrap labels. They are thin film labels printed with specialized inks on plastic film or tubing. During the labeling process, when heated (around 70°C), the shrink label quickly shrinks along the outer contour of the container. Then it adheres tightly to the container’s surface. Shrink film labels mainly include shrink sleeves and shrink-wrap labels.
1. Features
Shrink sleeves, made from shrink film, are cylindrical labels created through printing. They are convenient to use and particularly suitable for irregularly shaped containers. Applying shrink sleeves usually involves specialized labeling equipment. The process includes opening the sealed cylindrical sleeve and potentially punching holes. Floowing cutting it to the appropriate size, and it is applied to the container. Then, steam, infrared, or hot air is applied to ensure the sleeve adheres tightly to the container’s surface.
Key features include:
The high transparency of the film results in vibrant colors and a glossy finish.
The shrinkage process can lead to pattern distortion, especially for products with barcode markings.
Strict design and print quality control are necessary to avoid barcode quality issues caused by pattern distortion.
Shrink wrap labels can be applied using traditional labeling equipment. So it requires adhesives and higher temperatures. When shrinking, the adhesive in the overlapping portions creates stress. It is important to prefer hot melt adhesives.
2. Manufacturing Materials
Shrink-wrap labels are typically made from PP film. Since the shrinkage rate of PP film is low, it is generally within 20%. Hot melt adhesive is suitable for labeling. The use of solvent-based adhesives may cause wrinkling in PP film. Because the shrinkage temperature of PP film is relatively high. Heat treatment is usually performed using hot air. It can reach higher temperatures than steam heating.
3. Printing Guidelines
Unlike paper labels, shrink film labels use non-absorbent materials such as PVC, PP, PETG, OPS, OPP, and various multi-layer co-extruded films. The main printing method for shrink film labels is gravure printing. Gravure printing presses are common. It’s also cost-effective and capable of producing thick ink layers with vivid colors and rich detail. It becomes ideal for high-volume printing. Although flexographic printing is on the rise due to technological advancements. But gravure printing is still favored for mass production.
3.1 Tension control
The effect of tension changes can lead to inaccurate registration of film printing. Strict tension control is crucial to maintaining stability and balance. Adjustment of tension depends on film type and tensile strength. Wider films require higher tension than narrow films. While thicker films require higher tension than thinner films.
3.2 Drying temperature control
During the shrink film label printing process, controlling the drying temperature is crucial. Drying temperatures that are too high can cause the material to shrink. Insufficient temperature will result in incomplete drying of the ink. It leads to adhesion and backside contamination problems. Printing presses are often equipped with intercooler drying devices. It ensures that each color of ink dries thoroughly.
3.3 Ink selection
Shrink film printing mainly uses four types of ink: solvent-based ink, water-based ink, cationic UV ink, and free radical UV ink. In the field of shrink film label printing, solvent-based inks dominate. Followed by water-based inks and free-radical UV inks. Cationic UV inks are less common. Because they are more expensive and complex to print on shrink film.
3.4 Customer concerns
Flexographic printing is becoming more and more popular. Customer focus revolves around quality satisfaction and cost reduction. The choice of printing method is secondary among these priorities.
3.5 Surface treatment
Shrink film has the characteristics of high chemical stability and low surface energy. It has a smooth surface and non-absorbent water. Corona discharge treatment is required to increase surface energy and roughness.
4. Introduction to Types of Shrink Label Films
4.1 PE shrink film
There are many types of polyethylene (PE) shrink films such as LDPE, HDPE, and LLDPE. They are widely used for packaging beverages, fabrics, and other products. PE shrink film is famous for its flexibility and impact resistance. It is also tear-resistant and moisture-proof. His contractions were particularly severe.
4.2 PVC shrink film
Polyvinyl chloride (PVC) has added ingredients for heat resistance, toughness, and elongation. They are typically used for shrink labels. PVC shrink film has low shrinkage temperature and high-cost performance, so it is favored. But, due to environmental concerns, PVC is gradually being replaced by alternative materials.
4.3 POF shrink film
POF, or polyolefin, refers to multi-layer co-extruded polyolefin shrink film. It uses linear low-density polyethylene (LLDPE) as the middle layer. Copolymerized polypropylene (PP) is used as the inner and outer layers. POF shrink film is widely concerned because it is non-toxic and environmentally friendly. It also has the characteristics of high transparency and a high shrinkage rate. It has excellent heat sealability and high gloss. Its toughness, tear resistance, and uniform shrinkage are all very good. So it becomes a suitable substitute for traditional PVC shrink film.
4.4 PET shrink film
PET shrink film is a new type of shrink packaging material. It is recyclable, non-toxic, and odorless. It has good mechanical properties and is environmentally friendly. The shrinkage rate of traditional PET film reaches less than 30%. To obtain higher shrinkage, modified PET films are produced by copolymerization. The shrinkage rate of modified PET film can reach more than 70%.
In short, moving from PVC to PETG shrink labels shows a move to eco-friendly and high-performance options. The features, materials, printing tips, and shrink film types we talked about give a glimpse into the flexible and lively world of shrink labels.
