Synthesis And Application Of Phenyl And Piperazine-modified Polydimethylsiloxane

Since Ladenburg synthesized the first polysilioxane in 1872, polysiloxanes have made great progress and thousands of papers and patents have appeared. Various modified polysiloxane are also synthesized and widely applied for many fields. Amino-modified polysiloxanes attract the increasing attention due to its unique hydrophilicity, emulsibility,reactivity and adsorption.Most of the amino-modified polysiloxanes are modified with NH and-NH2. They are easily oxidized in the air because of the chromophore, while piperazine group is a six-member ring structure which containing two nitrogen atoms. They can form multiple hydrogen bonds, ionic bonds, exhibiting good hydrophilicity. Moreover, methyl groups bring about large steric effect, protecting the piperazine group from amino oxidation. So the piperazine group is introduced onto polysiloxanes, which solve the problem of oxidation. Phenyl group has unique radiation resistance, thermal stability and anti-UV property. Incorporating phenyl groups to polydimethylsiloxane can keep it stable, even in harsh conditions. Based on these investigations, polydimethylsiloxane modified with piperazinyl and phenyl is synthesized and it is also emulsified to applied the process of the pre-oxidation of the carbon fibers.1.Polydimethylsiloxane [(Ph-Pi) PDMS] modified with phenyl and piperazine is successfully prepared by the ring-opening polymerisation and hydrolytic polycondensation from Octamethylcyclotetrasiloxane(D4), Methylphenyl-dimethoxysilane(MPDS) and Piperazine-propyl- methyl-dimethoxysilane(PMDS) and both the initiator and the catalyst is KOH. It is confirmed by fourier transform infrared spectrum(FTIR), ultraviolet spectrum(UV), nuclear magnetic resonance hydrogen(1HNMR) and ultra-performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS). Catalyzed by KOH,the prime reaction conditions are founded: ratio among the MPDS and PMDS is 1:5 and reaction time was 2.5 hours and reaction temperature is 60 ℃.Their hydrophilicity and high-temperature oxidation resistances are carried out by contact angle test and thermogravimetric analysis. The results show that(Ph-Pi) PDMS exhibits excellent hydrophilicity and high-temperature oxidation resistance.2.(Ph-Pi) PDMS emulsion was prepared with a phase inversion by the emulsification of AEO-9. The results show that the emulsion has extremely low surface tension,nanosized diameter, narrow particle size distribution, alkali stability, dilution stability,centrifugal stability, thermostability, electrolyte stability and storage stability.3. Carbon fiber precusor is processed with the agent of(Ph-Pi) PDMS emulsion. Seen from SEM micrographs,(Ph-Pi) PDMS could form a good thin film on the surface of carbon fiber precursor. According to the FTIR information, we can calculate the relative cyclization degree. The results indicate that(Ph-Pi) PDMS emulsion can make a great contribution to the pre-oxidation process of Carbon fiber precusor, as well as imported ones.