Heat Sealable BOPP Film is a biaxially oriented polypropylene film that incorporates a specialized heat-sealable layer on one or both surfaces. This film grade is designed for high-speed packaging lines where reliable sealing, optical clarity, and moisture barrier performance are critical. HUA HENG manufactures BOPP film using multi-layer coextrusion technology, which allows precise control over the core layer, skin layers, and sealant layer chemistry. The result is a film that delivers consistent seal initiation, strong hot tack, and excellent machinability across a wide range of packaging formats.
Heat sealable BOPP film eliminates the need for additional adhesive or lamination steps in many applications. The sealing layer is coextruded during the orientation process, which means the film can be sealed directly to itself or to compatible substrates. This reduces packaging material costs, improves line efficiency, and simplifies inventory management. Typical end uses include overwrap for cigarette cartons, CD and DVD packaging, confectionery twist wrap, bakery bags, textile packaging, and horizontal form-fill-seal pouches for dry foods and non-food items.
The structure of heat sealable BOPP film typically consists of three or five layers. The core layer is made from homopolymer polypropylene, which provides mechanical strength, stiffness, and dimensional stability. The outer skin layers may include a heat sealable copolymer and a non-sealing layer that is treated for printing or metallization. HUA HENG uses a proprietary ternary copolymer blend for the sealant layer. This blend is optimized to achieve low seal initiation temperature while maintaining high seal strength and hot tack.
The sealant layer thickness can be adjusted during production to match the required sealing performance. For fruit and vegetable packaging, a thicker sealant layer may be specified to ensure seal integrity through contamination. For high-speed overwrap applications, a thinner sealant layer with excellent hot tack may be preferred to reduce dwell time. HUA HENG offers customized sealant layer thicknesses ranging from 1.0 micron to 5.0 microns per side. This flexibility allows converters to fine-tune the film for specific sealing jaws, temperature profiles, and packaging speeds.
Key design attributes of the HUA HENG sealant system include low odor, low migration, and compliance with food contact regulations. The film is suitable for direct food contact under EU Regulation 10/2011 and US FDA 21 CFR 177.1520. Heavy metal content is below the limits specified in EU Directive 94/62/EC and CONEG model legislation. The film does not contain phthalates, bisphenol A, or other substances of very high concern.
Q: Can BOPP film be used for liquid or high-moisture products?
A: It has good moisture barrier but is not a high oxygen barrier film. It can be used for dry or semi-dry products with moderate moisture content. For liquid products or products requiring extended shelf life, the film should be laminated to aluminum foil, metallized polyester, or a high-barrier substrate. The heat sealable layer still functions as the sealing medium in the laminate structure. HUA HENG recommends conducting migration and seal integrity tests for products with high moisture, oil, or alcohol content because these substances can affect the sealant layer performance over time.
Q: What seal strength can be expected from HUA HENG BOPP film?
A: At a seal temperature of 130°C, pressure of 0.2 MPa, and dwell time of 1 second, the typical seal strength ranges from 350 g/25mm to 450 g/25mm depending on the film grade. This value is measured on a tensile tester at 180° peel angle and 300 mm/min crosshead speed. In practical packaging applications, seal strength will vary based on jaw type, film thickness, product contamination, and machine settings. For critical applications such as sterile barrier or heavy product bags, HUA HENG recommends conducting seal strength tests on the actual package because the peel mode and stress direction in a real package differ from a flat laboratory sample.
Q: Is the film suitable for high-speed vertical form-fill-seal machines?
A: Yes, the film is designed for high-speed vertical form-fill-seal machines running at speeds up to 180 bags per minute. The key properties for high-speed operation are hot tack strength, low coefficient of friction, and consistent gauge. The hot tack values listed in the specification table ensure that the seal remains intact immediately after the sealing jaws open, even when product weight applies force to the bottom seal. The slip package is tuned to provide stable film tracking through the forming collar and film transport rollers. Operators should use a slightly higher seal temperature and shorter dwell time on high-speed machines to maintain production rate without sacrificing seal integrity.
Q: How should the corona treatment side be identified ?
A: The treated side is the non-sealing outer surface intended for printing or lamination. HUA HENG marks the treated side on each roll with a printed label or core tag. If the marking is lost, the treated side can be identified by applying a dyne pen solution. The treated side will wet uniformly and maintain a continuous film of solution for at least two seconds. The sealant side has a lower surface energy and will cause the solution to bead up. The treated side typically has a value of 38 dyn/cm or higher, while the sealant side is 36 dyn/cm or lower. Using the wrong side for printing will result in poor ink adhesion. Using the wrong side for sealing may result in weak seals or seal contamination.
