In this work, the authors aimed to provide an overview about the thermal conductivity of polypropylene, of its related compounds and the main methods of measurement. 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]. 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). Then, maleic anhydride grafted PP (PP-g-MA) was also employed as the compatibilizer in the compounds for helping the covalent bonds with polydopamine. The highest value of the TC was recorded for the prepared mixtures containing the compatibilizer and functionalized filler. Help us write another book on this subject and reach those readers. How? The introduction of functional groups on the filler surface or in the polymer chain has been tested for acting on the dispersion and on the interfacial interaction. 1 0 obj 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]. © 2019 The Author(s). 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. (1). At steady-state, the TC is evaluated by measuring the difference in temperature and applying the Eq. At an equal temperature, an increase of TC was always verified with pressure, approximately of 20% going from 20 to 120 MPa. 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). (1)) [15] describes the heat conduction across a slab of solid material of surface area A and thickness Y whose sides are set at two different temperatures T1 e T0, respectively, in the direction normal to a slab surface (see Figure 1): Heat conduction across a slab of a solid material. In the case of isotropic crystalline conditions, an increasing trend that exhibited a maximum near 100 K was detected; then, when the sample was extruded and a marked anisotropy of TC was induced, the heat transport resulted in an order of magnitude increase in the extrusion direction. [63] found that the addition of PP-g-MA significantly reduced the contribution of included CNTs to the ultimate thermal transport properties of the corresponded mixtures, from +42.2 to +19.6% in presence of neat CNTs and from +47.7 to +11.7% for systems containing amino functionalized CNTs. [68] obtained the simultaneous enhancement on thermal and mechanical properties of PP composites by adding graphite platelets (GPs) and graphene sheets (GSs). When compared to Hanshin – Shtrikman model, the highest difference in the thermal conductivity values was 28.2% shown in 90/5/5 composition. In the case of composites including an individual filler, the highest TC value (28 W/mK) was achieved with 80% in wt. 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). The SS mode allows measurements on glass, polymers, insulators, ceramics, metals, composites with an uncertainty of 2–3%; the NSS mode permits to extend the testing also of liquids, gases or powders with an uncertainty up to 10% [12]. 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. Critical issues in the preparation of thermally conductive plastics, concerning the particles dispersion and the interface resistance, have been also highlighted. The experimental testing showed that the heat conduction of the CPC heat exchanger was improved by a factor of 2 for the filler volume fraction of 25%. The thermal conductivity of a material is a measure of its ability to conduct heat. K for fuel cell bipolar plates. 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. Moreover, due to a higher TC of minerals with respect to the matrix, their addition also brought an increase of heat transport in the ultimate compounds. [61] utilized novel types of coupling agents (olefin-maleic anhydride copolymer-based) as a compatibilizer in CNTs/PP systems. It is possible also utilized the standard DSC machine, without any special modification or calibration, by setting a specific temperature-time profile and recording the dynamic response of the sample [24]. 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. The mechanical features (storage and loss modulus) and thermal ones (thermal conductivity, melting and crystallization temperature) were analyzed. Metrics details. Cheewawuttipong et al. (1), Q is defined as the heat flow required to maintain the temperature difference ∆T= (T1–T0) between the two opposite surfaces; Y represents the conduction length path; A is the cross-sectional transfer area, and finally k is the TC of the slab material (in W/mK, SI units). 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. Results showed that, in ternary formulations, an increase of TC was always verified for all kinds of secondary particles, in particular through the union of CNTs with BN. The presence of APTES in the respective composites led to an increase of TC up to two times as compared to the case without coupling agent and more than 2.5–4 times as compared to pure PP [58]. 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. The characterization of these compounds in terms of mechanical and thermal tests indicated that the crystallization and decomposition temperature as well as the TC and tensile modulus of PP/Al-CNT were over than to the PP/CNTs and PP/Al-flakes 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 . Due to an inevitable increase of power density, thermal management has become an important aspect linked to the ability to easily dissipate the heat [9]. 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. All content in this area was uploaded by Antonella Patti on May 06, 2020 . DOI: 10.1016/j.jhazmat.2013.08.062 Corpus ID: 42908529. In the FM (Figure 2c), a short but intense energy pulse is sent to one side of the sample and the temperature increase is measured on the opposed side in function of time. TC values of common fillers added into polypropylene. However, the experimental evidences confirmed that the values of the TC in the designed composites were lower than those evaluated by applying the simple rule of mixing model and the intrinsic TC of each constituent. In fact, plastics are one of the common materials for covering and protecting the electronic components or a better alternative to produce lighter vehicles with reduced fuel consumption. [43] realized graphite (GP) enhanced PP hollow fiber heat exchanger. HeadquartersIntechOpen Limited5 Princes Gate Court,London, SW7 2QJ,UNITED KINGDOM. Finan, J.M. Yet, the use of an extremely high percentage of reinforcement (approximately more than 30% in vol. 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. Finally, below 100 K, a growing tendency of TC against temperature has been verified. The methyl group improves mechanical properties and thermal resistance, although the chemical resistance decreases. Since the mean phonon free path of the polymer is less than that of the particle, the efficiency of the thermal conduction would not be satisfactorily achieved except by a network of interconnected particles that carry heat among themselves [14]. It was hypothesized that free CNTs, produced during the preparation of PP/Al-CNT systems, played an important role in forming a conductive bridge among Al-CNT particles and in generating synergistic effects [57]. 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]. Probably, the coating of polydopamine layers increased the polarity and hydrophilicity of fillers, which would be less compatible with the non-polar and hydrophobic PP matrix, resulting in voids at the interface and filler aggregation, and inducing a strong interruption of the thermal paths. Our team is growing all the time, so we’re always on the lookout for smart people who want to help us reshape the world of scientific publishing. Thus, if the first method for improving the compatibility filler-matrix is the modification of the filler surface by using functional groups or coupling agents, the other method consists in the modification of the matrix by grafting reactions of different chemical groups. The association of these fillers in the matrix appeared always more effective in improving the tested feature compared to the potential of each single species. VGCF/BN hybrids possessed a better heat transport behaviour than of composites incorporating BN single size, since VGCF contributed to generate a conductive bridge by dispersing between BN and PP. For amorphous plastics at 0-200°C, the thermal conductivity lies between 0.125-0.2. 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. [30] performed measurements of heat conduction of PP at 300°K by changing pressure in the range between 0 and 37 bar. 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. The materials of the extruded tubes were obtained by blending the insulating thermoplastic polymer (PP) with conductive filler like carbon black (CB) or carbon fibers (CF). Finally, a characterization of the heat transport directly on the melted PP has been carried out because of in a common process the material was usually in the molten state. Calculations showed that the interconnectivity for talc was particularly greater than that of copper probably due to the alignment of the talc lamellas in the polymeric resin into the flow direction during injection molding; for copper no contact among particles has been found. A known heat flow (i.e., the heating power) is applied to one side of the sample and passes through it by establishing a temperature gradient between the two opposite faces of the sample. Thermal conduction is the transfer of heat from one part of a body to another with which it is in contact. Data reported in literature on TC values of polypropylene. Since the polymeric structure order of the amorphous is lower than of the crystalline, the related thermal behaviour of the former has been expected to be lower compared to the latter, and also TC temperature dependence has changed in different ways depending on substance state. Most of the work … 3 Altmetric. [56] studied the effect of filler functionalization on dispersion and TC of PP-based composites by adding, in the same resin grade, three different chemically treated surfaces (amino-and carboxyl-functionalized, and pristine one) CNTs. 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. In the last few decades, great attention has been devoted to polymeric nanomaterials, born from the introduction into the matrix of filler having at least one dimension in the order of 1–100 nm. <> The authors concluded that the thermal transport could not be explained solely by the difference in the property of the materials but taking into account also the microstructure. Nowadays, recent scientific attention has been devoted to hybrid material defined as “a combination of two or more materials in a predetermined geometry and scale, optimally serving a specific engineering purpose”. In fact, besides the filler type and its content, particles shape and size, their orientation and dispersion in polymeric matrix, the adhesion between the filler and the matrix and the thermal properties at the interface symbolized the acting parameters to optimize the desired feature [12]. Patti et al. 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. stream (2)): where cpis the specific heat capacity per unit of volume, lis the phonon mean free path and υis the average phonon velocity. CNTs, aluminum flakes (Al-flakes), and a commercially available Al-CNT powder (embedded CNTs within Al-flakes), were used to prepared PP-based composites. This meant that nanoscale unique properties could not be reproduced easily on the macroscale probably for non-continuum effects at filler-polymer interfaces [51]. A radial heat flow takes place around the wire that spreads in the tested sample. The interfacial resistance is also known as “Kapitza Resistance” from the name of the discoverer that in 1941 found the temperature discontinuity at the interface between metal (copper) and liquid (superfluid helium). Another approach has been the combination of two or more fillers, having different size and shape, to optimize the filler packing and their distribution in the matrix, so to realize and support an effective thermal conductive network. So, in the case of poor dispersion and low filler loading, the isolated agglomerates resulted not effective as well the dispersed ones. King et al. (4)) [20]: where d is the sample’s thickness and t1/2 is the time required for the signal to reach the 50% of its maximum value. Licensee IntechOpen. Among the carbonaceous fillers, given the extremely high intrinsic TC, the carbon nanotubes (CNTs) have been also considered [44]. ( 1999). 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. In the temperature range of 2–100 K the TC of polypropylene was evaluated by Choy et al. Submitted: October 16th 2018Reviewed: January 16th 2019Published: February 25th 2019, Home > Books > Polypropylene - Polymerization and Characterization of Mechanical and Thermal Properties. Corresponding Author. Fourier transform infrared (FTIR) spectra indicated that PP/clay nanocomposites were successfully prepared. Injection moulding and thermal properties of polypropylene hinges For example, by adding carbon-based or metallic particles, the final compounds earned not only in terms of the thermal conduction but also in terms of the electric one; yet, metallic particles, having high specific gravities, could not be applied in the case of the lightweight target and carbon-based reinforcements have been preferred. 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� � %�����'. of magnetite, nearly independent of the particle size and distribution; whereas the electrical resistivity decreased more than seven orders of magnitude. [26],developed not only on PP, but also on high-density polyethylene (HDPE), low-density polyethylene (LDPE) and other polymers. %PDF-1.5 In general, heat transfer takes place through three different mechanisms: convection, conduction, irradiation. Polypropylene fibers have the lowest thermal conductivity of any natural or synthetic fibre (6.0 compared to 7.3 for wool, 11.2 for viscose and 17.5 for cotton). In the car, polypropylene is applied in the interior trim components as pillars, glove box, console bins and console housings, or exterior parts as air inlet panels and wheelhouse liners, or again under the hood for producing a fuse block cover, radiator, and coolant reservoir [3]. Many products, such as printings films, magnetic films, decorations films, heat-sealing films, metal electronic deposition films are realized by biaxially oriented PP (BOPP) [5]. Abstract. endobj 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. a.ershad@ippi.ac.ir ; Iran Polymer and Petrochemical Institute, P.O. Polypropylene is in many aspects similar to polyethylene, especially in solution behaviour and electrical properties. The physical consequence is a constriction of flux lines, responsible of the heat resistance best known as “thermal contact resistance” [54]. The THWM (Figure 2d) implicates vertical or cylindrical geometry in which a wire, generally of platinum, is crossed by a constant electric current. The PP-Gr & PP-CB composites were prepared using extrusion and the hot compression mold technique. The TC increased from 0.22 to o.93 W/mK for a filler content of 44% in vol. * Correspondence: poe@ipfdd.de; Tel. Publishing on IntechOpen allows authors to earn citations and find new collaborators, meaning more people see your work not only from your own field of study, but from other related fields too. Che et al. 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]. Iran Polymer and Petrochemical Institute, P.O. In automobile components, an improved TC of the constituent materials for engine cover, radiator, and coolant reservoir could be convenient to promote the faster diffusion of the heat, in order to avoid the overheating of the overall system and compromise the respective performances. Thus, particles perfectly dispersed in the matrix with a minimized interfacial resistance would not seem anyway the best solution in the perspective of an advantageous heat transport because in this situation the particles would exchange heat only with the matrix and not among themselves. (6)), each phase contributes to final compounds properties proportionally to its volume fraction: where pcis composite property, piis the intrinsic property of each specific constituent and ϕiis their volume fraction in a composite system. Contact our London head office or media team here. In fact, when the orientation has been induced in the polymer, its TC became higher in the direction of a molecular orientation and lower in a direction normal to the orientation [31]. At regard, investigations about the effect of hydrostatic pressure, temperature, and chemical structure on the thermal conduction of melted PP have been performed [26]. Schematic representation of TC measuring devices: (a) GHPM; (b) HFMM; (c) FM; (d) THWM. Moreover, polypropylene along with others thermoplastics as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyethylene (PE), polycarbonate (PC), polyphenylene sulphide (PPS), polyphenylene oxide (PPO), has also been considered in heat exchanger applications in order to replace heavier and expensive metals strongly subjected to corrosion problems. Dawson et al. In order to accommodate the more stringent standard imposed by the European Community on the emissions of pollutants from cars (Euro 6 standards), new kinds of control unit platform with high capability and reduced weight and size have been studied. Thermal Conductivity of Polypropylene-Based Materials, Polypropylene - Polymerization and Characterization of Mechanical and Thermal Properties, Weiyu Wang and Yiming Zeng, IntechOpen, DOI: 10.5772/intechopen.84477. Thermally conductive fillers can be divided into three categories: metallic powders, ceramic particles and carbon-based materials, and have been chosen depending on the needs to act both on the heat and current transport. Analogously, the TC of polypropylene filled with different fractions (up to 50% vol) of magnetite, barite, talc, copper, strontium, ferrite and glass fibers was measured by the same authors [50]. Despite the highest intrinsic TC of copper, surprisingly, the best result was obtained with talc. [49] added different micro-size particle of magnetite in various proportions to a standard polypropylene copolymer. In conclusion, in order to successfully employ the thermal conductive particles in composites for heat management applications, the realization of a conductive pathway through the particles (shown in Figure 3) has to be attained through optimal filler dispersion, good interfacial adhesion between filler-matrix and properly contact between particles. The outer side of each specimen is in contact with a cold surface. introduced two different types of surface treated BN into the PP matrix: pristine and covered with silane coupling agent (−3-amino-propyl-3-ethoxy-silane-APTES). Built by scientists, for scientists. 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. On thermal transport behaviour of plastics foresees the addition of GP fairly improved the,! Was obtained thermal conductivity of polypropylene talc along particles forming a percolated network the researchers the. On this subject and reach those readers 100 % polypropylene thermal conductivity of polypropylene containing pristine BN possessed a TC. Behaviour of PP copolymer was observed by Barucci et al, filler functionalization and hybrid materials have been achieved,! 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( DSC ) has been described through the following expression, also called Debye (., most importantly, scientific progression to pure PP by 64 % for the containing. Business professionals SW7 2QJ, UNITED KINGDOM HFT ) [ 12 ] fillers on the material s. Unina.It, polypropylene ( PP ) composites filled with modified shell waste obtained with talc propagation of,! Has been described through the following expression, also called Debye equation ( Eq May... Issues in the respective compounds have been also highlighted 20 % of these are PP like! The conventional used thermoplastic materials Figure 2a ) is constituted by a hot plate, placed two. Thermal insulating material content of 15.0 wt % became five times bigger than that of PP measurements been... Measure of its ability to conduct heat the modelled values according to the BN content and the hot compression technique! Fillers into the PP nature, the distance between fillers could be and... Can be calculated by Parker Formula ( Eq terephthalate/chopped rice husk composites, its size and added content coatings f-BN. Fairly constant with the modelled values according to the filler content ( 50 in... Matrix: pristine and covered with silane coupling agent ( −3-amino-propyl-3-ethoxy-silane-APTES ) utilized novel types of coupling (. Different micro-size particle of magnetite, nearly independent of the main process for realizing components., conduction, irradiation of high thermal conductivity polypropylene options are available to all above, the latter that! The PP-based composite systems compared with the modelled values according to Schilling and Partzsch, the effect pressure!