Polymer Solid-Phase Grafting at Temperature Higher than the Polymer Melting Point through Selective Heating
2019
Wang, Songhe | Zhang, Xiaohong | Jiang, Chao | Jiang, Haibin | Tang, Yujing | Li, Juan | Ren, Minqiao | Qiao, Jinliang
A new polymer grafting method, which is a solid-phase reaction but its grafting temperature is higher than the polymer melt point, is reported in this paper. This solid grafting reaction at high temperature can be achieved by using microwave which selectively heats the substance that can absorb microwave. Maleic acid-grafted polypropylene (PP-g-MA) was prepared by this new method. It is well known that polypropylene (PP) is transparent to microwave while maleic anhydride (MAH) can be heated by microwave. Under microwave irradiation, MAH dispersed in the micropores of PP spherical powder can absorb microwave to generate high temperature and cause PP nearby and MAH itself to generate free radicals. MAH-grafted PP (PP-g-MAH) can be prepared without using an initiator. The new method has many advantages that traditional methods do not have. For example, the prepared graft polymer has no initiator and MAH residue and thus is odorless; the prepared graft polymer also has excellent mechanical properties because the graft polymer has not undergone high-temperature degradation. It has also been found that trace amounts of partially reduced graphene oxide can increase the grafting ratio and properties of grafted PP. Furthermore, the monomers which do not absorb microwave can be also grafted onto PP with the help of NaCl which can be heated by a microwave and removed completely with water after grafting. Therefore, this new method is believed to be a general method and suitable to almost all kinds of polymers and monomers.
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