In this work, the positive-temperature-coefficient (PTC) effect of resistivity of low density polyethylene/graphite powder (45%) composites (LDPE/GP) in the presence of graphene before and after crosslinked was comparatively investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy, Raman spectrum, and resistivitytemperature test. The composites showed the repeatability of the PTC effect with heating cycles and a certain improvement in the room temperature resistivity. After crosslinked, the composites presented a higher PTC trip temperature at about 140 C than pure LDPE (T m 5 112 C), and stronger PTC intensity than room temperature resistivity (over 5 orders of magnitude). The results from DSC, XRD, and Raman spectrum indicated that the addition of graphene resulted in the gradual enhancement in the crystallization of LDPE matrix, which was the origin of the improvement of the PTC behavior of the composites. As a result, we could conclude that the additional conducting filler could improve the PTC effect of the conducting composite system. POLYM. COMPOS., 00:000-000, 2013.

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The new microparticles, 2-formylthiophene (FT)/TiO 2 and (E)-1,2-bis(5-formyl-2-thienyl) ethylene (EBFTE)/TiO 2 were synthesized with a silane coupling agent. The prepared TiO 2 composites were characterized using Ultraviolet-Vis absorption (UV-Vis), X-ray diffraction (XRD), scanning electron microscope (SEM) and thermogravimetric analyzer (TGA). Methylene blue was used as a model material to examine the photocatalytic activities of the prepared catalysts under both Ultraviolet-Vis (UV) and visible (Vis) light. The enhanced photocatalytic activities were observed in the presence of (FT)/TiO 2 and EBFTE/TiO 2 under Vis light. It suggests that FT or EBFTE plays a block or active role in the photodegradation mechanisms under UV and Vis light irradiation, respectively. Organic dyes are widely used in textile industry and the released industrial waste has caused serious damages to the water system [1][2][3][4][5]. In 1976, Carey et al. [6] first reported that TiO 2 was used as a photocatalyst in the degradation of biphenyl and chlorobiphenyls. Frank and Bard [7] studied the photocatalysis oxidation of cyanide ion with oxygen in the presence of TiO 2 powders as a heterogeneous photocatalyst. TiO 2 with the non-toxicity, chemically stability and low cost is a dramatic photocatalyst in degradation of colored water. However, TiO 2 can only make use of ultraviolet (UV) light that accounted for about 3%-5% of sunlight due to its rather broad band-gap (3.2 eV) [1]. Therefore, researches have been done to explore the mechanism of photocatalytic degradation with TiO 2 [8][9][10][11][12][13][14][15] and improvement of the degradation efficiency. Thus, some effective methods have been developed, such as dye-sensitization, ion doping and semiconductor coupling [16][17][18]. In particular, dye-sensitization is utilized to expand the spectral response region extending from UV light to visible (Vis) light. Sensitizers that showed a better energy match with the conduction band (CB) and the valence band (VB) of TiO 2 are introduced to improve the utilization efficiency of sunlight. The composites are desired to be active, Vis-responsive and highly stable [12]. For example, porphyrin/TiO 2 [19] and poly(acrylamide-co-(acrylic acid))/TiO 2 [20] were applied in photodegradation and showed high degradation efficiency. In addition, thiophene and its derivatives are considered as a kind of promising sensitizers due to its high absorption in Vis light region. Zhu et al. [21] and Lu and Yang [22] reported that polythiophene/TiO 2 and poly(3-hexylthiophene)/TiO 2 microparticles were synthesized and provided an apparent additive effect on their adsorption capacities under both UV light and Vis light.However, small molecule organic compounds modified TiO 2 are seldom reported. On the other hand, (E)-1,2-bis-(2-thienyl) ethylene [23] was reported as a kind of high performance material in Vis light region with narrow energy

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