E nergy Procedia 34 ( 2013 )808 –817
1876-6102 © 2013 The Authors. Published by Elvier B.V .
Selection and peer-review under responsibility of COE of Sustainalble Energy System, Rajamangala University of Technology Thanyaburi (RMUTT)
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元旦晚会策划书0.pro.2013.06.817
Available online at
W atthanaphon Cheewawuttipong et al. / E nergy Procedia 34 ( 2013 )808 – 817 809 polymers, such as polyamide (PA), polyethylene (PE), polypropylene (PP), polyvinylidene fluoride (PVDF), polystyrene (PS), and epoxy, provide significant economic benefits in comparison with other materials as a result of their light weight and low costs [1]. However, the polymers have low thermal conductivities. Therefore, some rearchers have worked to improve the thermal conductivity and electrical insulation of polymers by adding ceramic fillers, such as boron nitride (BN), alumina (Al2O3) [2], aluminum nitride (AlN) [3,4], mica, glass fiber, and zinc oxide (Zn2O3) [5].
中国梦的本质Boron nitride (BN) has been widely ud in the thermal management industry for years. BN is a good lubricant and abrasive, and it has a high thermal conductivity, high electrical resistance, and high temperature resistance. The common structures of BN are the hexagonal (hBN) and cubic (cBN) crystal structures. The structure of hBN is more stable than that of cBN [6]. The in-plane thermal conductivity is greater than 300 W/(m K), whereas the through-plane thermal conductivity is approximately 3 W/(m
K). Polyphenylene sulfide (PPS) has been ud to demonstrate the improvement in the thermal cond
uctivity and mechanical properties by adding BN filler. The result supported that it is possible to increa up to 60wt% boron nitride with particle size of less than 45 μm which effectively enhanced thermal conductivity, impacting tensile strength or impact strength whereas strain at break is dropped [7].
As high-density polyethylene (HDPE) was added boron nitride at various contents. The result illustrated
that the network structure of BN was formed at a high BN content in an HDPE matrix, and the dispersion
state of BN changed with the BN particle size [8]. The effect of content of micro or nano size BN particle
was studied on thermal and mechanical properties, and morphology of silicone rubber. BN was disperd
well in silicon rubber matrix while agglomerate was shown in some areas. Commonly, to add BN particles
穿越三国in silicone matrix reduces tensile strength and strain at break, whereas it increas modulus, hardness, and thermal conductivity. Nano size filler significantly contributes to the improvement of tensile strength of composites as compared with micro size filler at same content. However, the nano size filler does not promote thermal conductivity. The apparent aspect ratio of filler enhances high thermal conductivity [9].
Polypropylene (PP) is a balanced polymer from the point of the view of the physical and mechanical properties, very good electrical insulator, and also simple fabrication with a low thermal conductivity. The thermal and mechanical properties of polypropylene could be developed by melt compounding with particle and fibrous filler [10]. In both industry and rearch, it is interesting to consider experimental results dealing with developing properties of composites.
The purpo of this study is to improve thermal conductivity of PP by adding functionality filler. BN
filler was lected as the functionality filler. PP/BN composites were prepared by melt compounding which is a uful mixing method in the industry. In addition, we discuss the effect of dispersion state of
BN on thermal and other properties of PP/BN composites.
2.Experimental
2.1.Material
Polypropylene (PP) was supplied by Sumitomo Chemical Co., Ltd., Japan. Two types of PP, low-viscosity PP (PP-L, Melt flow rate (MFR) = 26-29 g/10 min) and high-viscosity PP (PP-H, MFR = 7-8
函的格式及范文g/10 min), were ud in this study. Two types of BN with different particle sizes, such as small particle (BN-s, the average particle sizes 1-2 μm) and large particle (BN-l, the average particle sizes 7- 10 μm
were added to PP matrices), were added to PP. They were produced by Showa Denko K. K., Japan. Figure 1 shows the SEM photographs of both BNs. The both BNs form the scale-like particles.
810W atthanaphon Cheewawuttipong et al. / E nergy Procedia 34 ( 2013 )808 – 817
Fig. 1. SEM photograph of filler particles: (a) small particles (BN-s, particle size 1-2 μm )
(b) large particles (BN-l, particle size 7-10 μm)
聪明的公鸡
2.2.Preparation of PP composites教育讲座
PP/BN composites were mixed by using a batch kneader at a barrel temperature of 250 ºC. The mixing time was 15 min. All blend ratios described related to percentage by volume. The loadings of BN were 15 vol%, 21 vol% and 29 vol%. Materials were dried under vacuum at 80 ºC for at least 24 h before mixing. The mixing sample was the sheet molded by compression molding at 200 ºC, and compression pressure 19.6 MPa for characterizing the properties of PP composites.
2.3.Testing
Differential scanning calorimetry (DSC) was carried out using an apparatus (DSC model 6220 produced by Seiko Instruments) for the characterization of the composites. Samples were aled in an aluminum pans. The samples were heated from 25 to 200 ºC at the heating rate of 10 ºC/min. After that, they were cooled to 40 ºC at the cooling rate of 10 ºC/min. During this period of time, matrix crystallization was completed and the samples were further heated from 40 to 200 º C at the heat rate of 10 º C/min in order to obtain the melting endotherms.
The thermal conductivity was measured with the hotwire method using the QTM-500 by Kyoto Electronics Manufacturing Co., Ltd., Japan. The sample for measurement of thermal conductivity was the sheet molded by press molding. The sample size was 170x120x0.5 mm. In addition, we u
d reference plates and software for measuring thermal conductivity of sheet type samples. In this study, the orientation of BN can be assumed as randomness becau the samples were molded by press molding.
The dynamic mechanical analysis (DMA) was measured using the E400-TYPE-DVE (UBM Co., Ltd., Japan). The temperature range was 40to 165 °C. The sampling frequency was 1 Hz (6.28 rad/s) and heating rate 2 °C/min in tension mode. In this study, storage modulus and loss modulus of PP composites were studied at 25 °C.
Scanning electrical microscopy (SEM) was carried out by using the instrument S-2600H. The instrument was produced by Hitachi, Co., Ltd., Japan, in order to investigate the dispersion behavior of BN in the composites.
X-ray diffraction (XRD) was measured by using the SWXD-FK manufactured by Ringaku Corporation, Japan. The wide-angle X-ray spectrum of the specimen was inspected using Cu-radiation. The XRD parameters were 40 kV, 40 mA for the X-ray source under vacuum
range of 10° to 50° and a scan rate of 0.2°/s at room temperature.
W atthanaphon Cheewawuttipong et al. / E nergy Procedia 34 ( 2013 )808 – 817 811 3.Results and discussions
3.1.Thermal conductivity
Firstly we will discuss the thermal conductivity of PP/BN composites. Figure 2 shows the thermal conductivity of the composites as a function of the BN contents. Obviously, the thermal conductivity incread with BN contents. And the thermal conductivity of PP/BN composite is almost independent of
the melt viscosity of PP at various BN content. The thermal conductivity of PP/BN-l composite was larger than that of PP/BN-s one at the same BN content. This result is a prerved one. In addition, the increasing rate of thermal conductivity as a function of BN content in ca using large size of BN (BN-l) became large in high BN contents
Fig. 2. Thermal conductivity as a function of BN content for each PP/BN composite.
3.2.Morphological investigation
The thermal conductivity of PP/BN composites would depend on the dispersion state of BN in the composites. Then, we will discuss the dispersion state of BN in the composites by using SEM photographs.
Figure 3 shows the SEM photographs on the cutting surface of the composites after cooled by liquid nitrogen. The dark part and the white one reprent the PP and BN, respectively. From Fig. 3. (a), for PP-
H/BN-s composite at BN content of 15 vol%, it is obrved clearly that the small particles agglomerated
and non-uniformly disperd in the PP matrix. In contrast, in Fig. 3. (c), for the PP-H/BN-l composites at
BN content of 15 vol%, the large particles were uniformly disperd and were well connected with other particles. The difference of the connection of BN particles between BN-l using ca and BN-s u
sing ca would contribute the thermal conductivity of the composite. At the high content of BN (the content of 29 vol%) shown in Figs. 3. (b) (for PP-H/BN-s) and (d) (for PP-H/BN-l), the BN filler displayed cloly packed particles in the PP matrix. It should be noted that at a high BN content, the denness of packing particles contributed to improve connections between the large particles. As a result, the incread BN network structure caud a dramatic increa in the thermal conductivity of the composites. In addition,
812 W atthanaphon Cheewawuttipong et al. / E nergy Procedia 34 ( 2013 ) 808 – 817
the cracked particles of the BN in the PP matrix is shown in Fig. 3. (d) (for PP-H/BN-l at content of 29 vol%). This would be occurred by filler friction in the melt compounding process.
舒筋草的功效与作用
Fig. 3. SEM photographs of PP/BN composites on the cutting surface of the composites after cooled by liquid nitrogen.
(a) PP-H/BN-s at 15 vol%, (b) PP-H/BN-s at 29 vol%, (c) PP-H/BN-l at 15 vol%, and (d) PP-H/BN-l at 29 vol%. 3.3. Dynamic mechanical analysis
新宿事件结局Next, we will discuss dynamic mechanical analysis results. From the results, we focud the results at a solid state. Figure 4 shows the dynamic mechanical analysis data of the composites with different contents of BN at 25 °C. The storage modulus and loss modulus incread with the BN content for each composite. The correlativity between the modulus and melt viscosity of PP could not be clear. On the contrary, the storage and loss moduli of PP/BN-l composite were totally larger than tho of PP/BN-s one, especially at high BN content. In addition, large particles significantly become increasing the storage modulus and loss modulus of composites. This tendency would agree with thermal conductivity at high BN content. This implies that the network structure of BN in PP/BN composite would have an influence on the solid mechanical properties.
