Study On Microstructure And Dynamic Mechanical Properties Of HTPB-based Polyurethane Elastomer

Hydroxy-terminated polybutadiene(HTPB)is an oligomer diol with excellent properties.The polyurethane materials synthesized with it can be applied to various fields.It is of great significance to study the relationship between structure and performance for the performance control of materials.In this paper,the relationship between polyurethane structure and performance is explored.The prepolymer method is used to synthesize HTPB-based polyurethane with the hard segment content of 20%,30%,40%and the isocyanate of 2,4-toluene diisocyanate(TDI),4,4'-Diisocyanate diphenylmethane(MDI),hexamethylene diisocyanate(HDI),isophorone diisocyanate(IPDI);HTPB-PPG-based polyurethanes with a molar ratio of HTPB to polypropylene glycol(PPG)of 3:1,2:1,1:1,1:2,1:3 and a different isocyanates of TDI,MDI,HDI,IPDI were synthesized.Infrared spectroscopy(FTIR),X-ray diffraction(XRD),small-angle X-ray scattering(SAXS),atomic force microscope(AFM)were used to characterize its structure and morphology,through differential scanning calorimetry(DSC),thermogravimetric analyzer(TGA),dynamic thermodynamic analyzer(DMTA),and stress-strain curve to test the thermal properties,dynamic mechanical properties and mechanical properties of polyurethane materials.The results show that:(1)When the hard segment(HS)content increases ?from 20%to 40%,the degree of hydrogen bonding obtained by FTIR increases from 78.8%to 83.1%,the ordered hydrogen bonding in the system increases from 23.4%to 36.8%,this shows that the structure becomes regular;XRD shows a crystalline peak in a system with a content of 40%,indicating the presence of a crystalline structure;as the content of the hard segment increases,the long period of phase separation increases from 6.87nm to 7.43nm,the size of the hard phase region increases from a few hundred nanometers to a few microns,the surface roughness increases from 37nm to 95nm,and the thermal stability is improved;the dynamic mechanical properties show that the 20%hard segment polyurethane has better low-temperature damping performance,and the stress-strain curve shows that the 40%hard segment polyurethane has better mechanical properties.(2)The degree of hydrogen bonding of HDI-PU reaches 100%,crystal diffraction peaks appear in XRD,and a regular hard phase structure also appears in the AFM image.Its thermal stability is the best among the four types of polyurethane,the storage modulus has reached 29.9MPa;the thermal stability of rigid MDI-PU is second only to crystalline HDI-PU,the dynamic mechanical properties found that the damping factor tan 8=1.02,the effective temperature range is-100?-45.91?,indicating that it has good low temperature damping performance.(3)Compared with a single HTPB-based polyurethane,the two-soft segment polyurethane synthesized by PPG and HTPB decreases first and then increases in compatibility with increasing PPG content.The degree of hydrogen bonding has been reduced from 79.5%of the single soft segment to 48.2%of 1:3-PU.The thermal stability is reduced.With the increase of PPG content,the damping peak is reduced.The damping temperature range of 1:2-PU is the widest,95?.The tan ? at 0? and 60?increases simultaneously,that is,the wet skid resistance and the rolling resistance increases.(4)The double soft segment polyurethane synthesized by TDI,MDI,HDI,IPDI,which is denoted as TDI-PU-M,MDI-PU-M,HDI-PU-M,IPDI-PU-M,compared with a single HTPB polyurethane,the degree of hydrogen bonding of HDI-PU-M is still 100%,and the rest of the system decreases with the addition of PPG;HDI-PU-M has a crystalline structure,and it has excellent thermal stability and mechanical properties,Young's modulus even exceeds the system without PPG;in addition,the crystallization peak of MDI-PU-M also got by XRD,dynamic mechanical properties show that its damping performance is the best among several polyurethanes,and it has high wet skid resistance and excellent rolling resistance.