Hot melt adhesive, also known as hot melt adhesive, is solid at room temperature. When heated to a certain temperature, it melts into a viscous liquid and becomes solid again when cooled to room temperature. , and has a strong bonding effect. Hot melt adhesive has the advantages of fast bonding speed, non-toxicity, simple bonding process, and good bonding strength and flexibility. Therefore, it is widely used in book binding, packaging sealing, and manufacturing. It has been widely used in shoes, textiles, etc., and in recent years there have been new developments in variety and performance.
Most hot melt adhesives are prepared using hot melt resins such as ethylene-vinyl acetate (eva), polyester, and polyamide. Due to the strength of eva and polyester hot melt adhesive It has poor elasticity and cannot withstand too much external force. Moreover, due to the high melting point and hardness of polyamide hot melt adhesive, its use is subject to certain restrictions. Hot-melt polyurethane adhesives mainly use the hydrogen bonds in the composition to cause physical cross-linking, so that polyurethane hot-melt adhesives have excellent elasticity and strength.
Hot-melt polyurethane gluewill lose its hydrogen bonding effect when heated and turn into a molten viscous liquid. It will return to its original physical properties after cooling. Therefore, polyurethane hot melt adhesive has the characteristics of high bonding strength, solvent resistance, wear resistance, etc. It has high reliability in use, good chemical and physical uniformity, simple bonding process (lower production costs), and less waste (unused The adhesive can be saved for later use), there are no mixing problems, and the adhesive can achieve optimal physical properties.
In addition, because hot melt adhesive does not use organic solvents, the production site will not be polluted, so it is welcomed by users. It can be widely used in bonding various materials, especially suitable for Fabric bonding. Polyurethane hot melt adhesive can be divided into two categories: one is thermoplastic polyurethane elastomer hot melt adhesive, and the other is reactive polyurethane hot melt adhesive.
The latter is divided into closed types and moisture-curing hot-melt type. Sealed type: Since the dissociation temperature of the sealing agent is as high as 100°C or above, which may cause bubbles to form in the adhesive layer, it is only used for maintenance and treatment. The moisture-curing hot-melt polyurethane adhesive is one-component, solvent-free, complies with environmental protection regulations, is easy to use, and its performance is comparable to solvent-based and reactive types, so it has good development prospects.
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