Reinforcing And Flame-retardant Effects Of Mesoporous Molecular Sieve On Polydicyclopentadiene

Mesoporous molecular sieve has attracted a great deal of interests for its particular characteristics, such as large internal surface area, uniform framework and easily controlled pore diameter. Thus, some of their applications including catalysts, sorbents, separating materials and reinforcing material of polymer are expected. In this paper mesoporous molecular sieve was employed to enhance the performance of PDCPD (polydicyclopentadiene). The perpared methods of PDCPD/mesoporous molecular sieve composites and their mechanism were studied.SBA-15 mesoporous molecular sieve was synthesized by hydrothermal synthesis, and the best reaction condition of in-situ polymerization of DCPD (dicyclopentadiene) compounding with SBA-15 was investigated. Four kinds of methods were employed to prepare PDCPD/SBA-15 composites by self-mading RIM device, which are in-situ composite of: DCPD and SBA-15 (Method 1), DCPD and SBA-15 modified with couple reagent (Method 2), DCPD and SBA-15 supported catalyst (Method 3), DCPD and modified SBA-15 supported catalyst respectively (Method4).Four kinds of PDCPD/SBA-15 composites (Method 1 to Method 4) were characterized and tested by XRD, TG, and determination of cross-linking degree. The results showed that for the composites prepared by methods 1 and 2, the polymerization of DCPD is difficult to occur in the pores of SBA-15, causing that few molecular chains of PDCPD can form in the pores of SBA-15, resulting in that the cross-linking degree of composites was lower than that of PDCPD. The employ of prepared methods 3 and 4 is benefited to the form of PDCPD molecular chains in the pores of SBA-15, as a result, SBA-15 and PDCPD can form a kind of crosslinked and entanglement structure, enhancing the cross-linking degree of composites greatly. Due to be surface modified, the composite prepared by method 4 had a lower degree of cross-linking than method 3. Because after modification, coupling agent molecules entered into the pores of SBA-15 and occupied a certain space of pores, causing that fewer molecular chains of PDCPD can form in the narrower pores of SBA-15, and the cross-linking degree of composite declined correspondingly.The mechanical properties of four kinds composites and pure PDCPD were analysed and compared. The results showed that, for the composites prepared by Method 3 and Method 4, the tensile properties, bending properties and shore hardness enhanced greatly, while elongation at break decreased slightly. Besides, the composite prepared by Method 3 possessed a stronger effect of enhancement. The mechanism of enhancement is that, SBA-15 can form a unique cross-linked structure between organic and inorganic phases after supporting catalyst, this structure enhance the cross-linking degree of composite and interface interaction between two phases, resulting in the improvement of the mechanical properties effectively. As for the composite prepared by Method 3, benefiting to the larger pore size of unmodified SBA-15, can absorb more molecular chains into its pores and has a stronger effect of enhancement.The flame-retardant properties of four kinds composites and pure PDCPD were analysed and compared. The results showed that, for the comosites prepared by Method 3 and Method 4, compared with PDCPD, their horizonal burning velocity declined, ratio of solid residue increased, density of smoke decreased, and the amount of residual carbon increased, the flame-retardant properties of composites had improved significantly. Furthermore, the composite prepared by Method 3 has a stronger effect of flame-retardance than composite prepared by Method 4. The mechanism of improvement in flame-retardant properties is that the nanochannels of SBA-15 can confine the movement of polymer chains inside them effectively, and the nano-sccaled hole walls with outstanding thermal insulation properties can delay the pyrolysis process of PDCPD and restrain the release of the pyrolysate. Similarly, because of the larger size of pore, a larger amount of molecular chains can enter into the pores of unmodified SBA-15, consequently the flame-retardant properties of composite prepared by Method 3 were improved more effectively than composite prepared by Method 4.