Studies On Modification Of Hyperbranched Polyurethane Solid-solid Phase Change Materials For Heat Storage

Polyurethane (PU) materials have been applied extensively in industry because of the many sorts of PU. Hyperbranched polymer has become one of the research focuses in polymer field and attracted a lot of attention in recent decades due to its novelty structure, unique properties and potential application prospect. It is a significant work that combined the two good performance materials together and synthesized phase change materials. According to the investigations from others, some modified hyperbranched polyurethanes for heat storage were prepared. The relationship between the structure and properties of the PU materials were characterized by various measurements. Concretely, the modified researches as follows:1. Using liquefaction modified 4,4'-diphenylmethane diisocyanate (L-MDI) reacted with polyethylene glycol (PEG) and hyperbranchend polyester, the solid-solid phase change materials of liquefaction modified hyperbranched polyurethane (L-HB-PUPCM) were prepared. The results showed that as well as the hyperbranched polyurethane (HB-PUPCM), the L-HB-PUPCM has good heat storage properties, great transition enthalpy, suitable phase transition temperature, good thermal stability, besides, it exist phase separation at room temperature. Moreover, the synthesis techniques of L-HB-PUPCM are simpler than HB-PUPCM. So it is a viable option that the L-HB-PUPCM does instead of the HB-PUPCM.2. According to several calculating methods, the nonisothermal crystallization kinetics of the L-HB-PUPCM for heat storage was investigated by DSC. Every method has its merits and limitation. To the system of L-HB-PUPCM, Jeziorny method has certain dependabilities for analyzing the crystallization behavior, the n values for L-HB-PUPCM are close to 3, it demonstrated that the nonisothermal crystallization of this material corresponds to three-dimensional growth with heterogeneous nucleation, and the crystallization is not a simple type, but has complexity. Ozawa equation is not suitable for analyzing the experimental data of nonisothermal crystallization kinetics because of the contraventions between hypothesis and fact. Mo method is fit for analyzing the nonisothermal crystallization behavior.3. The materials were doped with some organic, inorganic phase change materials, and then we synthesized hydrated magnesium chloride/L-HB-PUPCM, PEG eutectic/L-HB-PUPCM and tetrafunctional pentaerythritol/L-HB-PUPCM. The results indicated that the doped L-HB-PUPCMs had good properties and stable composition. Additionally, the phase transition temperature would be adjusted by the change of the content and kind of the doped materials.All in all, some properties of the modified hyperbranched polyurethane phase change materials were improved. This new kind of high performance solid-solid phase change heat storage material has extensive potential applications, thus become a development trend in macromolecule research area.