| The development of electronic product advances towards the direction of high integration, high power and high frequency, and the technological process to manufacture the product is complex, exigent and difficult. The new material and process technique are needed. The materials used poessess not only the good thermal conductive performance but also the good mechanical, flame retardant, electrical insulating and processing performance. Polymeric materials have received increasing interest and concern in recent years. Polyurethane (PU) elastomer has excellent comprehensive performance, such as high strength, wide range of hardness, excellent wear resistance and good fatigue resistance, etc., and its structure and performance are easily adjustable and controlled. PU is extremelly suitable for the preparation of polymer based material with different excellent performance. The paper synthesized a kind of PU with high strength, high hardness and good thermal property by molecular structure design and obtained good flame retardant and thermal conductive performance by filling different kinds of fillers. This kind of material has good prospect of marketing due to its low manufacturing cost and functional diversity.The PU elastomers were synthesized by using polytetrahydrofuran glycol (PTMG), polyether polyol (4110), six methylene diisocyanate trimer (HDI trimer) and triethanolamine (TEOA) as raw materials. The effect of the amount of PTMG,4110 and TEOA on its tensile performance and hardness were studied and the effect of the amount of TEOA and 4110 on the thermal performance was also discussed. When the weight percent of PTMG,4110 and TEOA was 37,38 and 25, respectively, PU had high tensile strength of 27.2 MPa, high shore D hardness of 70°and good thermal performance with 5wt% loss temperature of 306℃. Meanwhile, PU had thermal conductivity of 0.272 W/(mK) and limiting oxygen index value (LO1 value) of 25.1% dut to high degree of crosslinking, but it could not reach UL94 V-0 rank.Polyoxypropylene triol phosphate (PPT-P) was synthesized by phosphoric acid and polyoxypropylene triol as raw materials. Aluminum hydroxide (ATH) and magnesium oxide (MgO) were modified by PPT-P to become ATH-P and MgO-P, respectively. PPT-P had the similar structure to PU soft segment, and it could greatly improve the compatibility between ATH or MgO and PU matrix. When the filling amount was same, PU/ATH-P had higher mechanical and flame retardant than PU/ATH, and PU/MgO-P had higher mechanical, thermal conductive performance, flame retardant and thermal performance compared to PU/MgO.PU/ATH-P had good mechanical performance with tensile strength of 23.8 MPa and flame retardant performance which it could reach UL94 V-0 rank when ATH-P amount was 40 vol%, but it did not reach the demand of high thermal conductivity. As thermal conductive filler, MgO-P might be filled in PU, and PU/MgO-P reached its percolation threshold when the tilling amount was 30 vol%. When the filling amount was 45 vol%, PU/MgO-P had good mechanical performance with tensile strength of 27.9 MPa and good thermal conductive performance with thermal conductivity of 1.276 W/(m-K), but it could not reach UL94 V-0 rank. For the preparation of composite with both good thermal conductive and flame retardant performance, the mixture of MgO-P and ATH-P was uesd. When the filling amount of MgO-P and ATH-P was 30 vol% and 15 vol%, respectively, PU/MgO-P/ATH-P had both good thermal conductive and flame retardant performance. Its thermal conductivity was 1.009 W/(m·K) and it could reach UL94 V-0 rank. It could be concluded that MgO-P and ATH-P had synergistic effect on thermal conductive and flame retardant performance. It could futher improve the thermal conductive performance of PU/MgO-P/ATH-P composite by changing the size and shape of MgO. For instance, it could increase thermal conductivity by 34%to 1.356 W/(m·K) by filling MgO with irregular shape and large particle distribution instead of filling MgO with plane shape, meanwhile, it could pass UL94 V-0 rank. |
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