The two-component polyurethane adhesive is composed of a main agent composed of a hydroxyl group-OH and a curing agent composed of an isocyanate group-NCO. When used, the main agent and the curing agent are mixed in a certain proportion, and after the molecules are extended by the chemical reaction, a high molecular weight polymer is formed. As an adhesive, the composition, molecular structure, and molecular weight distribution of the polyurethane have an important influence on the bonding. Polyurethane can be considered as a block copolymer containing a soft segment and a hard segment. The soft segment is composed of oligomer segments such as polyester, polyether, and polyolefin, and is very compliant and assumes a random curl state due to its The glass transition temperature is lower than room temperature, and it is called rubber phase; the hard segment is composed of aromatic group, substituted urea group, urethane group, allophanate, biuret and other groups, and it is stretched into a rod shape at room temperature. It is easy to change its conformational conformation and the cohesive energy is very large. They associate with each other to form many microcells. The microspheres have a glass transition temperature much higher than room temperature, and they are glassy, ​​cold or microcrystalline at room temperature. Crystal, called the plastic phase. Due to the incompatibility of the thermodynamics of the two segments, microscopic phase separation occurs and phase or microphase regions form within the polymer matrix.
The excellent properties of polyurethane can be solved by two-phase morphologies: the hard segment phase provides multi-functional physical cross-linking, ie, the formation of hydrogen bonds and cross-linking, plays a reinforcing role; the soft segment is reinforced by the hard segment region. Because the physical properties of aluminum, plastic film, etc. vary greatly, if the adhesive structure design is not reasonable, the stress concentration will occur during the curing process; in addition, the two-component polyurethane adhesive is formed by the chemical reaction after the main agent and the curing agent are mixed. Molecular polymer (curing) bonding, this process takes a long time, usually requires 48H at room temperature. During this period, residual monomers and small molecules in the adhesive will enter the interface between the VM layer and the CPP layer through the aluminum plating layer. The VM layer and CPP will be reduced due to the curing shrinkage of the adhesive and the stress caused by the aluminum and CPP wire expansion coefficients. The bond strength of the layer.
2. Effect of material properties and aging conditions on the peel strength The films of three different thicknesses were compounded and cured under different conditions. The peel strengths are shown in Table 1 (slightly) (unit: N/15mm).
It can be seen from the table that the YH501SL/VM10 adhesive has a higher initial tack; composite films of different thicknesses have slightly different peel strengths; the film thickness is greater and the peel strength is also slightly larger. After aging for 24 h, the peel strength was very high. After aging for 48 h, the peel strength reached the maximum, and the aging strength continued to decrease, and the aluminum layer was partially transferred. It is recommended that the aging time at 50°C should not exceed 48H.
3. The influence of coating amount The composite film composite effect is not only affected by the amount of adhesive coating, aging temperature and time, but also related to the production environment humidity, composite temperature, film tension control and other factors. The factors affecting the aging temperature and time have been discussed above. The effect of the coating amount on the peel strength of full-print BOPP/VMCPP is shown in Table 2 (abbreviated).
It can be seen from the table that when the coating weight is greater than 2.0B/M2, the peel strength of the YH501SL/VM10 composite full-print BOPP/VMCPP reaches and exceeds that of the YH501S and the imported glue D, but it is recommended that the peel strength be maximized if the peel strength is to be maximized. The amount is not lower than 3.0B/M2.
4. Effect of the amount of curing agent The results of the different peeling strength of YH501SL and VM10 with different mass ratio (-OH/NCO) are shown in Table 3 (slightly).
 5. Water boiling resistance YH501S and imported plastic D is not resistant to boiling at 100 °C. The composite films of YH501SL compounded were aged at 50° C. for 48 hours and then boiled in boiling water at 100° C. The peel strength was measured immediately after cooking. The results are shown in Table 4 (omitted).
According to the data in the table, YH501SL/VM10 composite film adhesive has good boiled performance, but different films have different boiling resistance performance. The smaller the thickness of the film used, the better the resistance to boiled water.
6. Plastic/Plastic Composite YH501SL is used for compounding PET/PEP, PET/CPP and NNNY/PE composite films. After aging at 50°C for 48 hours, the peel strength is measured. The results are shown in Table 5 (omitted).
From the table it can be seen that YH501SL is used for plastic/plastic composites and has a high peel strength.
 7. Performance comparison The performance comparison of YH501S, imported adhesive D and YH501SL is shown in Table 6 (abbreviated).
 From the table, it can be seen that the YH501SL performs better than the YH501S and the imported glue D.
Through the adhesive composition, molecular structure, molecular weight distribution design and control, developed the excellent performance of aluminum alloy composite film adhesive YH501SL; the adhesive used in aluminum composite film has good initial tack, excellent peel strength and boiling resistance For plastic / plastic composite also has a higher peel strength.
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