Thermo Stability Of Thermoplastic Polyurethanc Elastomers

The mechanical property and thermo stability of TPU made by single softsegment are studied and the TPU with best property is selected. Besides, theproperty including thermo stability of selected TPU modified by organicmaterials （epoxy resin） and inorganic material encapsuled by organic materials（MUF/TiO₂） are also studied. The thermo stability of TPU related by molecularstructure as well as their degradation properties are concerned.The conclusions of this study are as follows:1. The study of TPU modified by organic materials1) The elasticity, elongation at break and tensile strength property of TPUsare favorable. TPU modified by organic materials have a less elongation at breakbut higher tensile strength. The elongation at break and tensile strength ofPCL-PTMG-TPU are both greater than700%and35MPa, respectively, whichare higher than TPU made from single soft segment. And the TPU mechanicalproperty of TPU is best as PCL/PTMG=3/7; The elongation at break and tensilestrength of TPU modified by epoxy resin （EP-PTMG-TPU） are both greater than500%and25MPa, respectively. and the mechanical properity increase first butdecreased behind. When EP/PTMG=3/7, the TPU has the best mechanicalproperty.2) The thermo stability of TPUs modified by organic materials is better thanthat made by sole soft segment. The PCL-PTMG-TPU （PCL/PTMG=3/7,6/4）and EP-PTMG-TPU （EP/PTMG=1/9,2/8,5/5） undergo three stage of thermodegradation. While, the rest undergo two stages of thermo degradation. Thethermo stability of polyurethane stiff foam with cross link structure is worse forthe content of soft segment and the molecular weight of raw material are less.Besides, they undergo two stage of thermo degradation.2. The study of TPU modified by MUF/TiO₂1) Polyurethane microspheres are prepared, which indicate that the grains sizes of microspheres made from PCL-2000, PTMG-2000, PEG-800are uniform.The grains sizes of microspheres made from PCL-2000, PTMG-2000decreasedue to the addition of1,4-BD. While The grains sizes of microspheres madefrom PEG-800increase due to the addition of1,4-BD.2) TPU modified with TiO₂microencapsulated by melamine-Urea-Formaldehyde were obtained, which indicate that the size of grain and breakingelongation decrease, however, the degree of crystallinity and tensile strengths aswell as the thermo stability of modified TPU are improved.3. The thermo stability of TPU related by molecular structureThe thermo stability of TPU influenced by modification methods was alsostudied, which indicated that: C-TPU synthesized by copolymerization has abetter thermo stability as well as microphase separation degree than B-TPUsynthesized by blend.The C-TPU and B-TPU undergo two stages of thermo degradation. wherethe urethane-S-ester and urethane-S-ether degrade initially followed by theurethane-BD. The hydrogen bonding formed between the soft domain and harddomain becomes weak due to the introduction of PTMG as soft segment whichdestroyed the regularity of original materials. Therefore, the micro phasesegregation gets higher as well as its thermo stability.4. The study of degradation of TPU:1) The degradation of TPU indicates that the weight of TPUs made fromsingle soft segment seldom decrease in pH=1hydrochloric acid solution, besides,the PTMG-2000-TPU is better than PCL-2000-TPU. The TPU made of bothPTMG and PCL also have a good state in hydrochloric acid solution, and thestability of TPU is PCL/PTMG-9/1-TPU<PCL/PTMG-7/3-TPU<PCL/PTMG-5/5-TPU.2) The chloroform experiment shows that: the TPUs made from single softsegment and two soft segments have good weight maintenance in half year. Thesoft segment ratio is odd number,9/1,7/3,5/5,（7/3）,9/1have a better weightmaintenance than that in even number.