Abstract:
The ternary copolymerization of ethylene/propene/8-furyl-1-octene was conducted with metallocene
rac-Et(Ind)
2ZrCl
2 as the catalyst and methylaluminoxane (MAO) as the cocatalyst to synthesize the ethylene/propylene copolymer with furyl-side groups. The copolymerization was proved to be of high efficiency with controllable copolymer composition. The copolymer structures were characterized by
1H-NMR, DSC and GPC. Ethylene/propylene copolymers with thermoreversible cross-linking structure were prepared via Diels-Alder reaction using different bismaleimide molecules, that is, with –C
6H
4(CH
2)C
6H
4―, ―(CH
2)
6―, and ―(CH
2)
12― as the middle segment of bismaleimide which were named as Ph2, C6, and C12, respectively, as the cross-linking agent. The cross-linking degree was determined quantitatively by equilibrium swelling measurements, and the properties of the cross-linked materials were determined by tensile test. Results showed that the cross-linking degree of copolymers could be controlled by changing the structure of cross-linking agent and adjusting the mole ratio of maleimide to furan. The cross-linking degree of the materials prepared by flexible bismaleimides C6 and C12 was more stable. Whereas for the cross-linked specimens obtained from rigid Ph2, the gel content and swelling ratio changed significantly after repeated processing. When bismaleimide was sub-stoichiometric, the cross-linking reaction could be fully implemented, so as to ensure the stability of cross-linking degree of the sample after repeated processing. The flexibility of the cross-linking agent could also promote the cross-linking reaction. In summary, the thermal reversibility of the Diels-Alder rings formed between the maleimide and furan groups rendered the cross-linked materials with repeatable processability.