Polyurethane adhesives are widely used in the field of film lamination due to their excellent performance. The following are the main film substrates it is applicable to and the precautions for use.
1. Applicable film substrates
(1)Polyurethane adhesives have excellent bonding effects on a variety of polar and non-polar films and can mainly be classified into the following categories:
(2)Plastic film: This is the most important application field.
(3)Polyester films, such as PET, feature high strength and good heat resistance, and are often used in packaging, electronics and other fields.
(4)Polyolefin films: including BOPP, CPP, PE, etc., are the most commonly used base materials for flexible packaging (such as food and pharmaceutical packaging).
(5)Nylon film: It has excellent puncture resistance and strength, and is often used in heavy-duty packaging that requires steaming.
(6)Vinyl films, such as PVC, are also frequently used in some specific packaging and industrial applications.
(7)Others: such as special films like polystyrene and polycarbonate.
(8)Metallized film: A material formed after vacuum aluminum plating on the surface of films such as PET and BOPP. Polyurethane adhesives can effectively penetrate into the pores of the aluminum layer, forming a firm "anchoring" effect, which is the key to making high-barrier packaging bags.
(9)Aluminum foil: Pure aluminum foil is an excellent high-barrier material. Polyurethane adhesives can form a strong and tough bonding layer with it, and it is widely used in moisture-proof and light-proof packaging of medicines and foods.
2. Relevant matters during Use
To ensure the bonding effect and the safety of the final product, the following points should be noted when using
(1)Surface treatment: The cleanliness, tension and halo treatment effect of the film surface are of vital importance. Oil stains, dust or low surface energy can seriously affect adhesion. Before use, ensure that the surface of the base material is clean and has undergone appropriate corona treatment to enhance its surface energy and wettability.
(2)Proportioning and mixing: The main agent and curing agent of two-component polyurethane adhesives have strict mixing ratios. Precise metering and mixing equipment must be used to ensure that the two are thoroughly and evenly mixed. Incorrect proportions or uneven mixing can lead to incomplete curing, seriously affecting the bonding strength and toughness.
(3)Curing conditions: The bonding strength of
Polyurethane Adhesive requires a certain period of time to be fully formed. Sufficient curing time and appropriate curing temperature must be provided (usually a curing room of 50-55℃ is required). If the curing time is insufficient, the performance of the composite film will not reach the best state.
(4)Solvent residue control: For solvent-based products, the drying process must be thorough to prevent solvent residues in the composite film, which is particularly crucial for the safety of food and pharmaceutical packaging.
(5)Application compatibility: The appropriate type of polyurethane adhesive should be selected based on the final product's usage (such as whether it needs to be heat-resistant, resistant to media, flexible, etc.) to ensure that it meets the requirements of the terminal environment.
In conclusion, polyurethane adhesives are versatile in film lamination, but their successful application depends on an understanding of the substrate's properties, strict process control, and the right product selection.
