Among the carbonaceous fillers, given the extremely high intrinsic TC, the carbon nanotubes (CNTs) have been also considered [44]. The resulting void appearance shown in SEM images and the sample density lower than the theoretical prediction both confirm the worsening compatibility between the filler and the matrix for the PP/f-BN composites. Is the Subject Area "Composite interfaces" applicable to this article? The TC behaviors of polymer composites can also be investigated quantitatively by using theoretical models [41–44]. In book: Polypropylene [Working Title] Authors: Antonella Patti. Antonella Patti and Domenico Acierno (February 25th 2019). As PhD students, we found it difficult to access the research we needed, so we decided to create a new Open Access publisher that levels the playing field for scientists across the world. It is also worth pointing out that the introduction of PP-g-ma alone also helps improve the composite TCs as the TCs of PP/PP-g-ma/BN composites are always higher than that of PP/BN composites at the same filler content, as shown in S1 Fig. (4-3). Schematic representation of TC measuring devices: (a) GHPM; (b) HFMM; (c) FM; (d) THWM. The parameter of t should be close to 2 for three-dimensional randomly distributed objects when the percolation happens. where ϕm is the maximum packing fraction of the dispersed fillers, and A is a parameter depending on the shape and orientation of fillers. Compared to that of neat PP, the incorporation of 25 wt% (12 vol%) f-BN alone showed an enhancement of only 1.95 times in composite TC, while there was a TC enhancement of 2.14 times for the PP/BN composites with the same filler content. (6-1) The functionalization, i.e., the introduction of functional groups on filler surface, obtained by covalent or non-covalent means, is a common approach widely adopted for changing the chemistry of inert inorganic particles. The mechanical features (storage and loss modulus) and thermal ones (thermal conductivity, melting and crystallization temperature) were analyzed. In details, below the glass temperature, as the temperature grew up, the TC of the amorphous remained the same or increased with temperature (probably for the effect of raising chain mobility), while for crystalline the TC initially remained the same and then diminished. PP, PP-g-ma and BN fillers were dried at 80°C for 12 h before being mixed and extruded at 190°C in a twin-screw extruder. A similar study was conducted by Cheewawuttipong et al. Different parameters have been considered in order to optimize the ultimate thermal performances in the realized composites: (i) filler dispersion, (ii) filler/matrix and filler/filler interactions. Compared to the polypropylene (PP) composites filled with pristine BN at the same filler content, thermal conductivity was much higher for those filled with both functionalized BN (f-BN) and maleic anhydride grafted PP (PP-g-ma) due to the improved filler dispersion and better interfacial filler-matrix compatibility, which facilitated the development of more thermal paths. In the first case, the measurement is carried out after reaching the equilibrium state, while in the second case, the test is performed during the heating phase [18]. With the addition of PP-g-ma and f-BN, PP/PP-g-ma/f-BN composites exhibit larger TC increase, with the highest TC of 0.58 W/mK achieved at the filler content of 25 wt%, an enhancement of 2.64 times compared to that of PP. The surface-modified h-BN is denoted as f-BN. In improving the heat conduction of the plastics different efforts have been spent in the scientific research with the addition of fillers characterized by a TC superior to the matrix [12, 13, 14]. Thermogravimetry analysis (TGA) was carried out on a thermal analyzer (Q500, TA, USA) under nitrogen atmosphere at a heating rate of 20°C/min. As shown in Fig 1, the surface of f-BN becomes much rougher compared to the pristine h-BN. This review was devoted to summarizing the main literature studies about TC of polypropylene and the recent developments of heat transport ability in PP based compounds. Data Availability: Data are all contained within the paper. Yes By increasing filler loading, positive but not always satisfactory increases of TC in the respective compounds have been achieved. Based on the experimental results obtained in this work, φf,C is assumed to be 9.3 vol%. Yet, the use of an extremely high percentage of reinforcement (approximately more than 30% in vol. All materials were used as received. The first was concerned with the reduction in thickness wall by requiring a new type of design; the second consisted in an increase of the thermal conductivity (TC) of the polymer resins [7]. Mussel-inspired approach was attempted to non-covalently functionalize the surfaces of boron nitride (BN) with self-polymerized dopamine coatings in order to reduce the interfacial thermal barrier and enhance the thermal conductivity of BN-containing composites. The TC of polymers is affected by several factors as crystallinity, chemical constituent, bond strength, molecular weight, side pendent groups, defects or structural faults, processing conditions and temperature [14]. Although few works are carried out on this way, it is not excluded that between functional groups may arise interactions, stronger than van deer Waals forces, which, binding more particles between them, also promote a reduction in the contact resistance. In general, the common approach for enhancing the thermal transport behaviour of plastics foresees the addition of thermally conductive particles. While for PP/f-BN composites, there showed the most voids and the most severe filler aggregation, causing the strongest interruption of the thermal paths. So, in the case of poor dispersion and low filler loading, the isolated agglomerates resulted not effective as well the dispersed ones. Such phenomenon may be correlated with the increased hydrophilicity of f-BN fillers that leads to the higher incompatibility with the hydrophobic PP matrix. Beyond an increase encountered during this phase, the TC remained fairly constant with the temperature. ), is needed to achieve the TC values in the composites, required for the modern technologies. On the contrary, an opposite trend of the TC of PP against temperature was found by dos Santos et al. 2015CB251503) and the Fundamental Research Funds for the Central Universities (2016YQ03, 2016YQ06). The heat capacity was measured by using a differential scanning calorimetry analyzer (DSC 404 C, Netzsch, Germany). By comparing data on PP-based compounds, despite the difference in filler loading, the greater efficiency in improving the TC of the matrix seemed to be realized in the case of combined micro- and nano-sized carbonaceous particles in the resin. Table 3 shows some values of TC reached in the PP-based composites, according to the filler type, its size and added content. Generally, an increment of the TC of polymers by raising the molecular weight was verified since a larger number of energy transactions took place in a substance with shorter chains [16]. Predicting thermal conductivity and mechanical property of bamboo fibers/polypropylene nonwovens reinforced composites based on regression analysis. At regard, some measurements have been reported in order to verify the effect of pressure on TC of polymers. 4, Fig. Copyright: © 2017 Chen et al. By considering geometry and packing efficiency of fillers, the Nielsen model [49, 50] is utilized to predict the composite TCs according to the following equations: In steady state condition, Fourier’ law (Eq. Polypropylene (PP, Moplen RP344RK) with molecular weight of ~100,000 Dalton and density of 0.9 g/cm3, was manufactured by PolyMirae, Korea. [11]. The first model applied here is the classical Maxwell-Eucken model [45] and the composite TC is calculated by Eq (3). Andersson et al. 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