Synthesis And Properties Of Organosilicon-Modified Polyurea Elastomers

Ami nopropyl-terminated polydimethylsiloxane(AP-PDMS)was prepared successfully with Octamethylcyclotetrasiloxane(D4)and 1,3-Bis(3-aminopropyl)tetramethyldisiloxane.Organosilicone-modified polyurea elastomers were prepared by the AP-PDMS or the AP-PDMS and polyether blended segments,isocyanate compounds and chain extender.The properties and structures of the elastomers were investigated by dynamic mechanic analysis(DMA),atomic force microscopy(AFM)and macroscopy mechanical testing.The macroscopy mechanical testing results of the elastomers show that the tensile strength and elongation at break were correlated with hard segment(HS)wt%and the molecular weight of soft segment.The highest tensile strength is 26MPa,the maximum elongation at break is 567%.The DMA results of the elastomers show that temperature insensitive rubbery plateaus exist between-50 ℃ and 120 ℃.The softening temperature of the elastomers is at approximately 170 ℃.The microscopic phase separation of the elastomers displays an upward trend with increasing the molecular weight of the soft segment and the mechanical strength of the elastomer become weak.The elastomers displays a mild microphase separation with in the low molecular weight of the soft segment and the mechanical strength of the elastomer become strong.The macro-mechanical properties and micromorphology of elastomers were analyzed,and the improved mechanical strength is thought to result from a mild microphase separation between the hard and soft segments.A new synthesis strategy was presented to prepare a organosilicone-modified polyurea elastomers.A new block soft segment(b-SS)was synthesised via an aza-Michael addition reaction of acryloxymethylterminated polydimethylsiloxane and amine-terminated polyoxypropylene(PPO).The hard segment(HS)was formed from bis(4-isocyanato cyclohexyl)methane(HMDI)and a 2-methyl-1,5-diaminopentane chain extender.The copolymers are tough and easily processed thermoplastic elastomers.The properties and structures of the elastomers were investigated by dynamic mechanic analysis(DMA),small angle X-ray scattering(SAXS),atomic force microscopy(AFM)and macroscopy mechanical testing.The DMA results of the elastomers show that temperature insensitive rubbery plateaus exist between-50 ℃and 80 ℃,which are independent of the HS wt%and the molecular weight of PDMS.The viscoelastic behavior of the elastomers was correlated with the molecular weight of PDMS used for the b-SS.The elastomers display improved mechanical strength compared with the published results of PDMS-based siloxane-urea segmented copolymers.The studies reveal that the mild microphase separation between the hard and soft segments leads to improved mechanical strength of the elastomers.In addition,for these copolymers,the introduction of b-SS is effective in avoiding a sharp phase separation assuming that the molecular weight of PDMS in the b-SS is appropriate.The macro-mechanical properties and micromorphology of elastomers were analyzed,and the improved mechanical strength is thought to result from a mild microphase separation between the hard and soft segments.we concluded that the introduction of the new type copolymers is an effective strategy to avoid sharp microphase separation between soft and hard segments.