What is stretch film
Wrapping film, also known as stretch film or heat shrink film, was the earliest domestically produced PVC wrapping film using PVC as the base material and DOA as a plasticizer with self-adhesive properties. Due to environmental issues, high costs (relatively high PE ratio, small unit packaging area), and poor stretch ability, PE stretch film was gradually phased out when it was produced domestically in 1994-1995. PE stretch film was first made of EVA as a self-adhesive material, but it was expensive and odorous. Later, PIB and VLDPE were developed as self-adhesive materials, with LLDPE as the main substrate, including C4, C6, C8, and metallocene PE (MPE).
Introduction
LLDPE stretch film was mainly blown film, which developed from single-layer to two-layer and three-layer; The production of LLDPE stretch film is mainly based on the casting method, because the casting line production has the advantages of uniform thickness and high transparency, which can meet the requirements of high magnification pre stretching. Due to the inability of single-layer casting to achieve single-sided adhesion, its application field is limited. Single layer and double-layer casting have less material selection and higher formulation costs than three-layer casting, so the three-layer co extrusion structure is still more ideal. High quality stretch film should have high transparency, high longitudinal elongation, high yield point, high transverse tear strength, and good puncture performance.
Production process conditions
Produced using imported linear polyethylene LLDPE resin and special additives with thickening agents, it can produce multifunctional winding films for hand use, resistance type machine use, pre stretching type machine use, UV protection, anti-static, and rust prevention. It has the following advantages:
1. By using double-layer co extrusion equipment, the extruded film can maximize the characteristics of each polymer, including transparency, tensile strength, and puncture resistance, reaching the optimal state at the melting point.
2. Has good tensile properties, good transparency, and uniform thickness.
3. It has good longitudinal extension, good rebound force, good transverse tear resistance, and excellent self-adhesive overlap.
4. It is an environmentally friendly and recyclable material that is odorless, non-toxic, and can be directly packaged for food.
5. It can manufacture single-sided adhesive products, reduce the noise generated during the winding and stretching process, and minimize dust and sand particles during transportation and storage.
Control of viscosity
Good adhesion ensures that the packaging film and layers on the outside of the goods are firmly attached, and there are two main methods to obtain adhesion: one is to add PIB or its masterbatch to the polymer; Another method is to blend VLDPE. PIB is a semi transparent viscous liquid, and direct addition requires specialized equipment or modification of the equipment. Generally, PIB masterbatch is used. The migration of PIB has a process that usually takes three days, and is also affected by temperature. When the temperature is high, the viscosity is strong.
When the temperature is low, it is not very sticky, but after stretching, the viscosity is greatly reduced. Therefore, it is best to store the finished film within a certain temperature range (recommended storage temperature is between 15 ℃ and 25 ℃). Blended with VLDPE, the viscosity is slightly poor, but there are no special requirements for the equipment. The viscosity is relatively stable and not controlled by time, but it is also affected by temperature. When the temperature is above 30 ℃, the viscosity is relatively high, and when it is below 15 ℃, the viscosity is slightly poor. The desired viscosity can be achieved by adjusting the amount of LLDPE in the adhesive layer. This method is commonly used for three-layer co extrusion.
Usage form
1. Sealed packaging
This type of packaging is similar to shrink wrap packaging, where the film wraps around the tray to wrap it all around, and then two heat grippers heat seal the two ends of the film together. This is the earliest form of use of stretch film, which has led to the development of more packaging forms
2. Full width packaging
This type of packaging requires a film width sufficient to cover the tray, and the shape of the tray is regular, so it is suitable for use with a film thickness of 17-35 μ m
3. Handmade packaging
This type of packaging is the simplest type of wrapping film packaging, where the film is mounted on a rack or held by hand, rotated by a tray, or wrapped around a tray. Mainly used for repackaging damaged pallets and ordinary pallet packaging. This type of packaging has a slow speed and is suitable for a film thickness of 15-20 μ m;
4. Stretch film winding machine packaging
This is the most common and widely used form of mechanical packaging, which is rotated by a tray or film around the tray, and the film is fixed on a bracket and can move up and down. This packaging has a large capacity, about 15-18 plates per hour. The suitable film thickness is about 15-25 μ m;
5. Horizontal mechanical packaging
Different from other packaging, it is wrapped around the item with a film, suitable for packaging long goods such as carpets, boards, fiberboards, profiled materials, etc;
6. Packaging of paper tubes
This is one of the latest uses of wrapping film, which is better than using wrapping film for old-fashioned paper tube packaging. The suitable film thickness is 30-120 μ m;
7. Packaging of small items
This is the latest packaging form of wrapping film, which can reduce material consumption and also reduce the storage space of pallets. In foreign countries, this type of packaging was first introduced in 1984, and just one year later, many such packaging forms appeared on the market, which has great potential. Suitable for film thickness of 15-30 μ m;
8. Packaging of pipes and cables
This is an example of the application of stretch film in special fields. The packaging equipment is installed at the end of the production line, and the fully automatic stretch film can not only replace the tape to bind the material, but also provide protection. The applicable thickness is 15-30 μ m.
9. Stretch form of tray mechanism packaging
The packaging of stretch film must be stretched, and the stretching forms of tray mechanical packaging include direct stretching and pre stretching. Pre stretching can be divided into two types: roller pre stretching and electric stretching.
Direct stretching is the process of stretching between the tray and the film. This method has a low stretching ratio (about 15% to 20%). If the stretching ratio exceeds 55% to 60% and exceeds the original yield point of the film, the film width decreases, the puncture performance is also lost, and the film is easily broken. And at a 60% elongation rate, the tensile force is still very high, which may cause deformation of light goods.
Where to buy stretch film?
Whether you're looking to buy in bulk or for individual use, For top-quality stretch film, Shenzhen JYE packing materials Co., Ltd ( JYE stretch film) extensive experience in the industry, combined with their commitment to innovation, makes them a trusted choice. You can reach directly at +86 13632970701 or email sales8@jyestretchfilm.com. to inquire about purchasing options and further details
