Research Of Poly(1-butene)(PB)/Graphite Composite With Thermal Conductivity

The additive such as graphite with high thermal conductivity are commonly used to improve the thermal conductivity of polymer. Poly(1-butene)(PB), which exhibits excellent impact resistance, environmental stress cracking resistance, creep resistance and processability, is widely used as pipes. But due to the thermal conductivity of PB is only 0.23 W/(m·K), the application of conductive material was limited. It is both theoretically and practically meaningful of preparation of PB/graphite conductive composite.PB/graphite composite was prepared by means of melting compounding. In this paper, the influence of the coupling agents, the elastomer, the content of graphite and the aging durations of the PB/graphite composite on mechnical properties of PB/graphite composite was studied. The isothermal crystallization behavior, non-isothermal crystalization behavior and the crystal transformation process of PB/graphite composite were studied by differential scanning calorimetry(DSC), X-ray diffraction(XRD) and optical microscopy. The thermal conductivity of PB/graphite composite were also measured by the LFA 447 instrument, and some models such as Y.Agri equation were usd to predict thermal conductivity of PB/graphite composite, which provides the theoretical suggestions for preparation of the thermal conductive PB/graphite composite. The rheological properties of PB/graph- ite composite were tested by Capillary Rheometer, which provides the theoretical suggestions for preparation of the PB/graphite composite.The results show that the tensile strength of PB/graphite composite which contained 40wt％graphite and 8wt％EPDM-g-MAH reached to 27MPa, while the flexural strength was about 19MPa, the mechanical properties of the composite was excellent. The tensile strength and the flexural strength of the PB/graphite composite were improved significantly with increasing of the aging durations when the content of graphite was 15wt％and aging duration was less than 40 h, the best tensile strength and the flexural strength of composite was 25MPa and 17MPa, respectively. But the mechanical properties of the composite changed little with increasing of aging durations when the aging duration was over 40 h.The non-isothermal crystallization behavior of PB/graphite composite was analyzed by Jeziorny and Liu method. Graphite which can be used as nucleating agent to accelerate the crystallization of the PB/graphite composite when the content of graphite was lower than 15wt％. But the addition of the graphite impeded the crystallization of the system, leading to the reduction of the crystallization rate and the degree of crystallinity of PB/graphite composite when the content of graphite was more than 15wt％. The crystal structure of PB/graphite composite transform from formⅡto formⅠwith the crystallization time increasing, and the graphite accelerated the transformation of crystal form.The results showed that with increasing of the graphite content, the thermal conductivity of PB/graphite composite was increased. The thermal conductivity of PB/graphite composite was 3.9W/(m·K) when the average particle size of graphite was 5μm, and the content of graphite was 85wt％. Maxwell-EucKen, Cheng-Vochon and Y.Agri equations could predict thermal conductivity of PB/graphite composite at low content of graphite. The thermal conductivity of PB/graphite composite and the volume fraction of graphite fit the exponential growth:λ=-0.32+0.45e^{(100V)/(31.17)}The results show that the PB/graphite composite melt belonged to pseudoplastic fluid, the shear viscosity gradually decreasing with increasing the shear rate, while as the activation energy of viscosity flow decreased at first and then increased. but the activation energy of viscosity flow PB/graphite composite increased with increasing graphite content.