Shaohui Yang
Shanghai Banzan macromolecule Material Co., Ltd
Hotmelt adhesive resin mainly consists of thermoplastic resin or elastomer grafted with functional groups.
To introduce polar or functional side groups to the backbone of polymer can improve the polarity of the polymer, which not only helps to improve the adhesive property of materials, but makes for blending with other polar material to prepare polymer alloy. The monomers used to graft to polyolefin include acrylic acid, unsaturated carboxylic acid, and its anhydride, for example, maleic anhydride (MAH). In order to extend the application of adhesive resin, it is necessary to improve its performance.
Therefore, the adhesive resin materials with high melting points, good mechanical properties and reactivity were developed by blending grafted polymer with modified resin, tackifier and filler with different proportion.
There are adhesive resins based on polyolefin grafted with maleic anhydride (PO-g-MAH), ethylene copolymers (EAA, EVA, EEA, etc) in the current market. Compared to common conventional synthetic resins, they have excellent compatibility property and good adhesive property with polar materials or metal.
Figure 1. molecule structure of polyolefin grafted with MAH.
The grafting reaction of polyolefin is radical reaction, which carried out by melt grafting of monomer and polymer in the presence of initiator. For polyethylene grafted with MAH, peroxide initiator was decomposed to primary radical at high temperature, which can couple with hydrogen proton on polyethylene molecular chain to form macromolecule radical. Then, MAH grafted to polyethylene molecular chain and the graft polymer PE-g-MAH was obtained via radical addition reaction of macromolecule radical and MAH as shown below.
initiator decomposition：
formation of macromolecular radical:
radical addition reaction with MAH:
radical transfer:
radical coupling:
