In an internal combustion engine, an elevated heat transfer affects performance, efficiency and emissions because it reduces the average combustion gas temperature and pressure, and the work per cycle transferred to the piston, for a given mass of fuel within the cylinder [10]. It’s based on principles of collaboration, unobstructed discovery, and, most importantly, scientific progression. 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 . The effect of acting pressure on TC of polypropylene seemed to be always positive, probably for the induced stress in a longitudinal direction that led to anisotropy of the tested feature. Most of the work … Results showed that initially, as the temperature rose between 25 and 125°C, the TC of PP slight decreased from 0.25 to 0.15 W/mK; then, it underwent a sudden increase reaching a peak of approximately 0.47 W/mK during the melting process, and finally it decreased. Anderson [16] reported that the TC of polymers decreased as the disorder increased: imperfections, by decreasing the order of the molecular structure, caused a large phonon scattering that reduced the heat transport. In the modern car engine, the electronic control unit (ECU) involves both hardware and software, required to perform the functions as mixture formation, combustion and exhaust gas treatment. Furthermore, the TC of PP in molten form was not significantly affected by temperature but it appeared to be a complex function of the molecular weight distribution and possible long chain branching [34]. By making research easy to access, and puts the academic needs of the researchers before the business interests of publishers. Although the experimental evidences seem to be lesser and to be explored in greater detail, it should be emphasized that the increasing the compatibility between filler and matrix not always a positive effect on heat transport has been verified. In the molten state, the TC of polypropylene appeared to be a complex function of molecular weight and chain branching; it continued to increase by pressure but resulted almost unaffected by temperature. Patti et al. <> The filler functionalization (i.e., the introduction of functional group on filler surface) and the addition of compatibilizer in polymer/particles mixtures, have been considered a useful approach for developing the compatibility between the two phases, and consequently for improving the dispersion and the interfacial interaction. The growing spread of polypropylene in the industrial world together with the increasing demand of thermally conductive plastics represented the driving force of studying the heat transport in the polypropylene, and of recent progress and development of the thermal conduction in polypropylene-based materials. K for fuel cell bipolar plates. However, the first approach is more time consuming and not suitable for shaped samples as concentric cylinder or sphere. DOI: 10.1016/j.jhazmat.2013.08.062 Corpus ID: 42908529. They found that neither the chemical structure of coupling agent nor the application methods (masterbatch and impregnation) have been conclusive on the heat conduction of prepared compositions. The analysis has been performed by incorporating a temperature sensor [22] or a made in-house accessory into the common apparatus [23]. Weidenfeller et al. Polymers are thermal insulators, and due to defects, grain boundaries, and/or scattering with other phonons the mean free path of phonons (l) is very low and consequently also their TC [16]. [25] and Osswald et al. The former assumes that all phonons propagate as a planar wave, so the transmitted energy is related to different acoustic impedances of two materials. For example, in the case of polyolefins, maleic anhydride is commonly grafted to polypropylene for improving the filler-matrix interface through both physical and chemical interactions, as covalent linkages and hydrogen bonds [59]. 6, 01069 Dresden, Germany; krause-beate@ipfdd.de (B.K. A homogeneous filler dispersion in the resin led to a consistent load transfer from the matrix to particle and in the realization of a conductive network for electrical and thermal energy. Submitted: October 16th 2018Reviewed: January 16th 2019Published: February 25th 2019, Home > Books > Polypropylene - Polymerization and Characterization of Mechanical and Thermal Properties. Dawson et al. A cubic polynomial trend of the TC as a function of the filler concentration was found, for all three families of nanocomposites. [66] analyzed the effect of single carbonaceous fillers (CB, GP, CNTs) and their combination on the TC of PP in the light of a potential market of fuel cell bipolar plates. In many previous works, it has been reported that two essential components for an optimal effect of the reinforcement in a composite are filler dispersion and orientation. In Eq. A hybrid has been conceived as a mixture of two or more raw materials with own intrinsic properties and different shape and size (“A + B + shape + scale”) to enhance or diminish physical, mechanical, thermal and electrical properties, as stiffness or strength, and also to manipulate the percolation limit [64]. [70] added BN and vapor-grown carbon fiber (VGCF) into the PP resin. The PP-Gr & PP-CB composites were prepared using extrusion and the hot compression mold technique. Login to your personal dashboard for more detailed statistics on your publications. In the case of composites including an individual filler, the highest TC value (28 W/mK) was achieved with 80% in wt. [49] added different micro-size particle of magnetite in various proportions to a standard polypropylene copolymer. On the contrary, an opposite trend of the TC of PP against temperature was found by dos Santos et al. Che et al. [26],developed not only on PP, but also on high-density polyethylene (HDPE), low-density polyethylene (LDPE) and other polymers. <>>> Szentes et al. the BaTiO3/PP and Al2O3/PP composites exhibited the same increment in TC approximately equal to 100%, while for BaTiO3/Al2O3/PP systems an abnormal heat-conducting properties (of an order of magnitude higher compared to the pristine PP) was recorded. Thermal conductivity of the polypropylene is increased from 0.27 up to 2.5 W/ (m K) with 30 vol% talc in the polypropylene matrix. of magnetite, nearly independent of the particle size and distribution; whereas the electrical resistivity decreased more than seven orders of magnitude. This attitude was confirmed in the case of injection molding and extrusion [32] or foaming [33] processes during which a macromolecular orientation of polymer chain was inferred. In this work, the thermal conductivity of polypropylene (PP) was increased by adding thermally conductive fillers, which were boron nitride (BN) and titanium dioxide (TiO 2). This indicates that the geopolymer can be applied for thermal insulating material. In a solid, the main mechanism of heat transport is the conduction corresponding to the transfer of particle vibration energy to the adjacent particles without any motion of the matter but exclusively due to collision [12]. These studies confirmed that, as the hydrostatic pressure increased on melt state, also the TC of thermoplastics in general, and of PP in particular, increased for a reduction in free volume. A radial heat flow takes place around the wire that spreads in the tested sample. On the contrary, the formulations containing pristine BN possessed a higher TC with respect to that prepared with modified one. x��]mo#7�� �A_�q���݇`��'�&�ٛd��~�x4�������_�'�/r��l�Ez�ⱥ��T�U���"O��{���=X}�����_w�W?������������ۋ˛�����ŋ��Wg��o?���k��A��~���j�d%�F�:�����^���yӭ.�?��]]�z��7�~��z�����w�~����Wߟ�NP^���Kh� �p���_1~�v��"�I!I�%}d/��[Q��z�i��m�Vw�K?j%�ޜ��ņ�w�Ofm����?�I�A���X� F�7'b�aӇ[Ю��4� � %�����'. Experimental data, related both to atactic and isotactic PP, demonstrated that the TC increased strongly with pressure with a continuous change in the slope of curve until it reached an asymptotic value. Results showed that the addition of GP fairly improved the crystalline, thermal stability and conductivity of the PP. These particles are added in the hosting matrix by prevalently melt blending: one among the classical processes for compounding, particularly preferred in an industrial context. Data reported in literature on TC values of polypropylene. It was also conducted thermogravimetric analysis (TGA) on PP and HMPE fibers. At an equal temperature, an increase of TC was always verified with pressure, approximately of 20% going from 20 to 120 MPa. Furthermore, if the particles were oriented in the direction of applied force or heat, their full potential could be achieved both in terms of load and energy transport. This led to an intensification of power and a significant heat flow that can negatively affect the lifetime and reliability of the device, if it is not opportune dissipated away in time [8]. Polypropylene Characteristics. [68] obtained the simultaneous enhancement on thermal and mechanical properties of PP composites by adding graphite platelets (GPs) and graphene sheets (GSs). Licensee IntechOpen. @article{Yao2013MechanicalAT, title={Mechanical and thermal properties of polypropylene (PP) composites filled with modified shell waste. The size and shape of particles, their orientation and distribution in the polymer, the interfacial interaction between filler and matrix and between filler and filler, have been identified as crucial aspects in the optimization of final heat transport in the polymeric composites. Request PDF | On Feb 15, 2014, D.S. By Maria Alejandra Costantino, Caren Rosales and Valeria Pettarin, By Mohamed F. Ibrahim, Mohamed H. Abdelaziz, Herbert W. Doty, Salvador Valtierra and Fawzy H. Samuel. Abstract. The physical consequence is a constriction of flux lines, responsible of the heat resistance best known as “thermal contact resistance” [54]. Brief introduction to this section that descibes Open Access especially from an IntechOpen perspective, Want to get in touch? They found that by increasing the content, the distance between fillers could be reduced and the development of conductive structure was attained. All content in this area was uploaded by Antonella Patti on May 06, 2020 . The common apparatuses for evaluating the performance in heat transport of PP and its related compounds are: the “Guarded Hot Plate Method (GHPM)” and the “Heat Flow Meter Method (HFMM)”, based on SS approach, or the “Flash Method (FM)” and the “Transient Hot Wire Method (THWM)”, instead based on NSS approach. The TC remained almost the same as the temperature increase until it decreased during melting due to a possible breakup of crystalline regions. 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]. Instead, the latter assumes that all phonons, colliding into the interface, are randomly scattered. Air voids in the matrix of foamed concrete allow it to reduce the thermal conductivity and dry density; however, due to its reduced density, foamed concrete is prone to microcracking which results in loss of strength. 49 Citations. Antonella Patti and Domenico Acierno (February 25th 2019). Finally, filler functionalization and hybrid materials have been presented as methods to support the heat conduction in the PP-based composite systems. 3 Altmetric. This quantity represents a real challenge for the processability of the material and makes difficult or impossible extrusion and injection molding processes [14]. Ren et al. 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. All these factors contributed to realize effective thermally conductive pathways in the composites, actualized among particles with an advanced dispersion, good interfacial adhesion with the pristine material (lower interfacial resistance) and the proper contact among themselves (lower contact resistance). Amir Ershad‐Langroudi. Box 14965/115, Tehran, Iran===Search for more papers by this author. Compared to the polypropylene (PP) composites filled with pristine BN at the same filler content, thermal conductivity … In addition to Kapitza resistance, in a composite a further resistance to the heat transport, involving the solid-solid interface, i.e., particle-particle interface has to be considered. In the 1932, Debye introduced the concept of mean free path of thermal waves, simply called phonons, for explaining the thermal conduction in a dielectric crystal, in which the electrons are not free to move. Finally, a nearly linear temperature dependence without any detectable plateau of the TC of PP copolymer was observed by Barucci et al. A wide variety of thermal conductivity polypropylene options are available to you, such as pp, 100% polypropylene. [60] functionalized the surfaces of micrometric BN with a thin layer of polydopamine coatings (f-BN). In order to analyze this influence, the present work carried out thermal conductivity, thermal expansion, and compressive strength after exposure to a temperature of 200 °C on specimens made of concrete with addition of polypropylene (PP) fibers and concrete with addition of high modulus polyethylene (HMPE). Fourier transform infrared (FTIR) spectra indicated that PP/clay nanocomposites were successfully prepared. Polypropylene (PP), once discovered, immediately has been appreciated for its remarkable and various qualities like low density (the lowest compared to all thermoplastics), excellent chemical and corrosive resistance, dimensional stability, recyclability, flexibility, good processability, and low cost. *Address all correspondence to: antonlla.patti@unina.it, Polypropylene - Polymerization and Characterization of Mechanical and Thermal Properties. In this perspective, the aspect ratio of particles became an interesting and important parameter to be considered because bigger was the length of particles, lower could be the filler/matrix interface and scattering of phonons, and greater was the TC value in the final system. At steady-state, the TC is evaluated by measuring the difference in temperature and applying the Eq. Two solid bodies, which are apparently in contact, actually touch together only in a few points due to their roughness and geometrical defects. 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]. (5) [21]: in which ln C is the Euler’s constant, q is the applied thermal flow, r is the wire radius and T0 is the cell temperature. In Table 1 the TC values for polypropylene are shown. In injection molding or extrusion, the greater would be the TC of the processed materials, lower would be the heating or cooling time and the operating costs of the overall processes. By balancing in the polymeric resin the filler content and type, it is possible to obtain the desired features in the final products. 4 0 obj An effective comparison of reported TC values has not been possible due to differences in the filler loadings in each study. Comparison among TC enhancement in some PP-based formulations due to the effect of different introduced nano-sized and/or micro-sized fillers into the matrix. 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