Research On The Synthesis Of Polyhydroxylated Polybutadiene And Preparation Of Elastomer

Polyolefin polyols is an important raw materials for preparing polyurethane elastomer.Hydroxyl-terminated polybutadiene(HTPB)is commonly used as polyolefin polyol and its chain segment contains two hydroxyls.It has many advantages,for example,good transparency,low viscosity,oil resistant,aging resistant,low temperature performance and good machining performance.However,the polyurethane elastomer has a low tensile strength and elongation at break prepared by it.Polyhydroxylated polybutadiene(PHPB)is a type telechelic liquid material which has more hydroxyl than HTPB.The number of Ammonia ester base hydrogen bond of the branched polyurethane elastomer generated by PHPB and isocyanate root is more than that of linear polyurethane elastomer.Owing to the increased of the number of the hydrogen bonds,the cohesion between molecules increased and the mechanical properties of the polyurethane elastomer is improved simultaneously.Thus,the modification of HTPB to produce PHPB which contains multiple hydroxyls has a certain practical value and scientific theory significance.1.In this paper,the PHPB was synthesiszed by HTPB and epichlorohydrin(ECH)through molecular design under the alkaline condition of sodium hydroxide.The tetrabutyl ammonium bromide(TBAB)was used as the catalyst in this reaction.It is the first time to synthesis PHPB by adding hydroxys on two terminals of HTPB.It was tested by infrared spectrometer(IR)and hydrogen nuclear magnetic resonance(1H-MNR).The technological condition of synthesis of PHPB was optimized by single factor experiment.The optimal conditions for synthesizing polyhydroxylated polybutadiene were as follows: reaction temperature of 55? and reaction time of 1.5 h,the molar ratio of raw material,sodium hydroxide and catalysts was n(HTPB):n(ECH): n(Na OH): n(TBAB)=1: 2.9: 3: 0.03.TG results showed that the thermal stability of PHPB was better than the HTPB.2.The polyurethane elastomer was synthesized by one-step method with polyhydroxylated polybutadiene as raw material,toluene diisocyanate(TDI)as curing agent,1,4-butanediol(BDO)as chain extender and dibutyltin dilaurate(DBTDL)as catalyst.The mechanical properties and the thermal performance of polyurethane elastomer were tested by differential scanning calorimeter(DSC),thermogravimetric analyzer(TG)and electronic universal tensile test analyzer.The experiment results showed that,when curing parameter R was 1.2,the catalyst was 0.6%,n(BDO): n(PHPB)= 3: 1,and curing temperature was 65?,the mechanical performance of prepared polyurethane elastomer was good.The tensile strength of the polyurethane elastomer prepared in optimal conditions was 4.04 MPa,elongation at break was 282.02%,and glass transition temperature was about-20?,the thermal decomposition temperature was 226?,and thermal maximum weight loss rate was 278.71? and 464.18?.Meanwhile it showed excellent performance of thermal property.Compared with the HTPB polyurethane elastomer,PHPB polyurethane elastomer has better mechanical properties.3.The viscosity change of different curing system is different along with the change of time.Using DV2 T type rotary viscosimeter,the viscosity changes with time of different HTPB and PHPB curing system was determined.The results show that: property of HTPB-TDI and PHPB-TDI curing system is better when BDO was used as chain extender,DBTDL as the catalyst,and the curing parameter R was 1.2.When curing parameter R were identical,PHPB-TDI-BDO-DBTDL system required a shorter curing time than that of HTPB-TDI-BDO-DBTDL system.4.The effect of dibutyltin dilaurate on kinetics of HTPB-TDI-BDO and PHPB-TDI-BDO curing reaction were studied by non-isothermal differential scanning calorimetry.The results showed that the apparent activation energy of uncatalyzed HTPB-TDI-BDO curing system was 60.28 k J·mol-1,and the apparent activation energy of HTPB-TDI-BDO curing system was 48.39 k J·mol-1 using dibutyltin dilaurate,and the reaction series were 0.886 and 0.864,respectively.The apparent activation energy of uncatalyzed PHPB-TDI-BDO curing system was 52.38 k J·mol-1,the apparent activation energy of PHPB-TDI-BDO curing system was 39.16 k J mol-1 using dibutyltin dilaurate,and the reaction series were 0.873 and 0.843,respectively.The results show that,adding of dibutyltin dilaurate reduced the apparent activation energy of HTPB-TDI-BDO and PHPB-TDI-BDO curing system,accelerated the curing reaction rate and shortened the curing time.The apparent activation energy of PHPB-TDI-BDO system is lower than that of HTPB-TDI-BDO system,which leading to the curing time is shorter.