Preparation And Properties Of Vinyl Polysiloxane Modified By Rosin And Its Derivatives

Polysiloxane combines the structures of organic and inorganic compounds, and is widely used in cosmetics, coatings, rubbers and medicals. However, its application is limited by the low mechanical strength, and its thermal stability is also needed to be improved. In this paper, without using the traditional coal and petroleum based chemicals, the regenerable rosins were used to modify the vinyl polysiloxane.Four kinds of novel vinyl polysiloxane and two kinds of novel vinyl fluorosilicone resins(VFS) were synthesized from natural rosin(CR), hydrogenated rosin(HR), maleated rosin(MR) and maleopimaric acid(MPA). The four kinds of novel vinyl polysiloxane include natural rosin modified vinyl polysiloxane(CR-VMS), hydrogenated rosin modified vinyl polysiloxane(HR-VMS), maleated rosin modified vinyl polysiloxane(MR-VMS) and maleopimaric acid modified vinyl polysiloxane(MP-VMS). The two kinds of novel vinyl fluorosilicone resin(VFS) include maleated rosin modified vinyl fluorosilicone resin(MR-VMS) and maleopimaric acid modified vinyl fluorosilicone resin(MP-VMS). For comparison, common vinyl polysiloxane(C-VMS) and common vinyl fluorosilicone resin(C-VFS)were also synthesized without using any natural rosin and modified rosins. Based on this, C-VFS, MR-VFS and MP-VFS were respectively used as crosslinkers to prepare the common fluorosilicone rubber(C-FSR), maleated rosin modified fluorosilcone rubber(MR-FSR) and maleopimaric acid modified fluorosilicone rubber(MP-FSR), while the pure fluorosilicone rubber(P-FSR) was also prepared without using any VFS. Fourier transmission infrared spectroscopy(FT-IR) and nuclear magnetic resonance(NMR) were used to characterize the synthesized vinyl polysiloxane; Differential scanningcalorimeter(DSC) and thermal gravimetric analysis(TGA) were used to study the curing behavior of the synthesized vinyl polysiloxane, and the low temperature resistance and high temperature resistance of the curing products from the synthesized vinyl polysiloxane; The micro-morphology, mechanical properties and oil-resistance properties of the fluorosilicone rubbers were investigated in detail. The results have the theoretical guiding significance for the modification of silicone with rosins as the raw materials.From the analysis results of FT-IR, 1H NMR and 13 C NMR, amidization reaction can occur between the aminopropyl group in the side chain of polysiloxane and the carboxylic group in CR and HR, imidization reaction can occur between acid anhydride and aminopropyl group. Based on these reactions, HR, CR, MR and MPA can be grafted onto the side chain of polysiloxane, MR-VMS and MR-VFS contain maleated rosin based fused ring(MRBFR), while MP-VMS and MP-VFS contain maleopimaric acid based imide heterocycle(MPABI).The four kinds of novel vinyl polysiloxanes can cure by the free radical polymerization reaction with 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane as the initiator. When the loading of rosins in the synthesis formula were equal, their curing behaviors were studied by DSC. The results showed that the order of the heat output per unit weight of C-VMS and the four kinds of novel vinyl polysiloxanes with the same contents of vinyl group was as following: C-VMS > MP-VMS > HR-VMS > MR-VMS > CR-VMS. It seemed that the conjugated double bonds in rosins might have the effect of chain-transfer reaction on the free radical vulcanization of polysiloxane.Scanning electron microscope(SEM) and energy-dispersive X-ray spectroscopy(EDX) were used to investigate the morphology of fluorosilicone rubber, and it was found that MRBFR and MPABI could intensify the micro-phase separation.The mechanical investigations of fluorosilicone rubbers revealed that MRBFR could decrease the specific density, hardness, tensile strength and rebound resilience of fluorosilicone rubber, while the tearing strength and breaking elongation were improved effectively. Compared with MRBFR, MPABI could effectively improve the cohesion energy and the comprehensive properties, while it has a little effect on the crosslinking density. Both MRBFR and MPABI could slightly decrease the oil-resistance properties of fluorosilicone rubber. When the mass percentage of VFS was 2.0%, compared with P-FSR and C-FSR, the tearing strength of MR-FSR respectively increased 20.1% and 9.1%; compared with MR-FSR, the hardness of MP-FSR increased 4.6%, tensile strength increasing 45.0%, breaking elongation decreasing 18.0%, tearing strength increasing 2.8%, rebound resilience increasing 36.0%, crosslinking density increasing 77.7%; compared with C-FSR, the hardness of MP-FSR increased 4.6%, tensile strength increasing 6.1%, breaking elongation increasing 18.0%, tearing strength increasing 23.5%, rebound resilience increasing 9.7%; compared with P-FSR, the hardness of MP-FSR increased 9.7%, tensile strength decreasing 5.4%, breaking elongation increasing 4.0%, tearing strength increasing 12.2%, rebound resilience increasing 21.4%.The thermal stabilities of MR-FSR, MP-FSR and the curing products from HR-VMS, CR-VMS, MR-VMS and MP-VMS were measured by TGA. The results showed that introduction of HR, CR, MR and MPA could improve the high-temperature resistance of silicone, which should be ascribed to the formation of three-membered phenanthrene ring and five-membered imide heterocycle ring. Compared with the curing products from C-VMS, all curing products from HR-VMS, CR-VMS, MR-VMS and MP-VMS showed better thermal stability above 350 oC, and the curing products from MP-VMS was 55.7% higher than the curing product from C-VMS. The order of their thermal stability was as following: MP-VMS > MR-VMS > HR-VMS > CR-VMS > C-VMS. When the mass percentage of VFS was 2.0%, the temperature corresponding to the maximum weight-loss rate(Tmax) of MR-FSR was 19.6 oC higher than P-FSR, 3.7 oC higher than P-FSR; the thermal stability of MP-FSR was better than MR-FSR, which should be ascribed to the higher content of MPABI in MP-VFS.The low-temperature resistance of MR-FSR, MP-FSR and the curing products from HR-VMS, CR-VMS, MR-VMS and MP-VMS were investigated by DSC. The results showed that introduction of MPABI and MRBFR did not affect the low-temperature resistance of silicone.