Crystallization behaviors and mechanical performance of polypropylene/tetrapod‐shaped zinc oxide whisker composites

Polypropylene (PP)/tetrapod‐shaped zinc oxide whisker (T‐ZnOw) composites are prepared via a melt‐mixing method in combination with a Haake rheometer. Differential scanning calorimetery (DSC) is used to investigate the nonisothermal and isothermal crystallization behaviors of the composites. Crystalline morphology is observed using hot‐stage optical microscopy, and the mechanical performance of the composites is investigated. Results indicate that T‐ZnOw has no heterogeneous nucleation effect on PP; in fact, it retards the growth of the crystal. Filled T‐ZnOw in PP matrix decreases the peak crystallization and melting temperatures of PP. T‐ZnOw shows either a reinforcing or toughening effect on the PP matrix at very lower weight ratios. These effects, however, decline with increasing T‐ZnOw contents because the size of the spherulitic crystals becomes bigger. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Enhanced thermal conductivity and wear resistance of polytetrafluoroethylene composites through boron nitride and zinc oxide hybrid fillers

In this study, the thermal conductivity and wear resistance of the polytetrafluoroethylene (PTFE)/boron nitride (BN), PTFE/zinc oxide (ZnO), PTFE/tetra‐needle‐shaped zinc oxide whiskers (T‐ZnO), and PTFE/hybrid filler composites were investigated. Moreover, hot‐press molding was used to prepare the composites, and scanning electron microscopy was used to observe the morphology of the fillers and the friction interface of the composites. The results show that continuous thermally conductive paths could be formed in the PTFE/hybrid fillers (T‐ZnO and BN) composites so that the thermal conductivity of the PTFE was improved through addition of the hybrid fillers. Meanwhile, the synergistic effects of the hybrid fillers were useful for reducing the wear rate of the composites. In addition, for the pure PTFE, abrasive and adhesive wear was found. Compared to the worn surface of the pure PTFE, the worn surface of the PTFE composites filled with ZnO, T‐ZnO, BN, and hybrid fillers presented much smoother surfaces, and slighter ploughing occurred. Therefore, the hybrid fillers improved not only the thermal conductivity but also the wear resistance of the PTFE composites. The data obtained in this study contributed to the construction of a technical foundation for the preparation of composites with a high thermal conductivity and wear resistance. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42302.     

Synergistic enhancement of glass fiber and tetrapod‐shaped ZnO whisker on the mechanical and thermal behavior of isotactic polypropylene

Improvement of mechanical and thermal properties is always the goal of high‐performance general plastic for engineering applications. Herein, isotactic polypropylene/glass fiber/tetrapod‐shaped zinc oxide (iPP/GF/T‐ZnOw) composites are developed via melt‐extrusion on twin‐screw extruder. To improve the distribution of T‐ZnOw in iPP matrix, T‐ZnOw is first modified by various silane coupling agents and its structure is characterized by scanning electron microscopy, Fourier transform infrared spectra, and X‐ray diffraction (XRD). The optimized treatment condition is determined via comparison of activation index. The introduction of GF and T‐ZnOw could improve the mechanical properties including tensile strength, elastic modulus, flexural strength, flexural modulus, and impact strength, indicating that the surface modification and compatibilizer could enhance the interfacial interaction of iPP/GF/T‐ZnOw composites. Moreover, XRD and differential scanning calorimentryresults show that T‐ZnOw as a novel β‐nucleating agent could induce the formation of β‐crystal and the existence of GF counteracts the formation of β‐crystal induced by T‐ZnOw. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44217.     

基于变径-变压塔的甲醇/氯仿二元共沸物精馏分离过程热集成与动态控制

研究了基于变径-变压塔(VDC-PSD)联合处理二元共沸物甲醇-氯仿分离过程的热集成,基于Aspen dynamics对动态控制方案进行了仿真验证,并通过改进控制结构实现了对进料流量和进料组成在±20%扰动下的自动控制;在没有增加控制难度的情况下,带有热集成的VDC-PSD可以实现热量的综合利用,提高PSD的经济性。     

Matching micro- and nano-boron nitride hybrid fillers for high-thermal conductive composites

Incorporating hybrid fillers into polymer has been considered as one of the effective ways to obtain composites with high-thermal conductivities (TCs). Herein, we fabricated polytetrafluoroethylene (PTFE) composites by using micro-boron nitride nanosheets (mBNNs) and nano-BNNs (nBNNs) as fillers, and studied the optimum ratios of mBNNs to nBNNs (i.e., mBNNs:nBNNs) for obtaining high-thermal conductive composites at different filler's contents. The results indicated that for the composites with total BNNs contents of 10, 20, and 30 wt%, the optimum mBNNs:nBNNs for obtaining the highest TC were 9:1, 9:1, and 5:5, respectively. The highest TC of the composites with 30 wt% BNNs could reach 1.46 W·m⁻¹·K⁻¹, which was 356% higher than that of PTFE. The reasons for optimum mBNNs:nBNNs values were interpreted by observing the composite's microstructures. Moreover, the fabricated composites also exhibited excellent electrical insulation properties. This study has important implications for obtaining high-thermal conductive composites using hybrid fillers.     

Cold plasma modification of boron nitride fillers and its effect on the thermal conductivity of silicone rubber/boron nitride composites

Hexagonal boron nitride (h‐BN) fillers were first coated with low‐molecular‐weight polydimethylsiloxane (PDMS) by solution dispersion and then treated in argon plasma for different times. The modified h‐BN fillers were characterized by high‐resolution transmission electron microscopy, X‐ray photoelectron spectroscopy, and contact angle analysis. The results revealed that a thin PDMS film several nanometers thick was tightly coated on the surface of the h‐BN filler after plasma treatment, and this thin film could not be removed by 48 h Soxhlet extraction with n‐hexane at 120°C. Furthermore, the effect of plasma modification on the h‐BN filled silicone rubber composites was investigated. The results indicated that the plasma modification improved the interfacial interaction between h‐BN and the matrix, but hardly affected the distribution state of the h‐BN in the composites. The composites filled with the modified h‐BN exhibit significantly higher thermal conductivity than the composites filled with untreated h‐BN. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Synergistic improvement of thermal conductivity of thermoplastic composites with mixed boron nitride and multi-walled carbon nanotube fillers

The thermal conductivity of composites with a polyphenylene sulfide (PPS) matrix and a mixture of boron nitride (BN) power and multi-wall carbon nanotube (MWCNT) fillers was investigated. Synergistic improvement in thermal conductivity of the composite was observed due to the generation of three-dimensional thermal transfer pathways between the BN and MWCNT. The improvement strongly depended on surface treatment of the MWCNTs, such as hydrogen peroxide and acid treatments. The thermal conductivity of the composite was affected by the interaction and interfacial thermal resistance between the PPS matrix and the MWCNTs. The maximum thermal conductivity achieved was 1.74 W/m K for a composite that was pelletizable, injection moldable, and thermally conductive with low electrical conductivity and good mechanical properties.     

Thermal conductivity of polypropylene composites with hybrid fillers of boron nitride and vapor‐grown carbon fiber

High thermal conductivity fillers of boron nitride (BN) and vapor‐grown carbon fiber (VGCF) were used alone or incorporate to prepare polypropylene (PP) composites. The effects of filler content, particle size and shape, and single vs. hybrid BN/VGCF fillers were investigated with respect to the thermal conductivity of the PP composites. The thermal conductivity of PP/BN composites depended upon the content and particle size of the BN. Increased content and length of VGCF had the effect of increasing the thermal conductivity of the PP composites. Hybrid fillers were created with a mixture of medium‐sized BN and long‐length VGCF; hybrid BN/VGCF fillers enhanced the thermal conductivity of PP composites with a lower total content compared with PP composites containing only medium‐sized BN particles. POLYM. COMPOS., 37:936–942, 2016. © 2014 Society of Plastics Engineers     

Solvent-free fabrication of thermally conductive insulating epoxy composites with boron nitride nanoplatelets as fillers

A solvent-free method for the fabrication of thermally conductive epoxy-boron nitride (BN) nanoplatelet composite material is developed in this study. By this method, polymer composites with nearly any filler fractions can be easily fabricated. The maximum thermal conductivity reaches 5.24 W/mK, which is 1,600% improvement in comparison with that of pristine epoxy material. In addition, the as-fabricated samples exhibit excellent overall performances with great mechanical property and thermal stability well preserved.     

Synergistic effects of hybrid fillers on the development of thermally conductive polyphenylene sulfide composites

The future of integrated circuits with three‐dimensional chip architecture hinges on the development of practical solutions for the management of excessive amounts of heat generation. This requires new polymer–matrix composites (PMCs), with good processibility, high effective thermal conductivity (k_eff), and low but tailored electrical conductivity (σ). This article explores the synergy of hybrid fillers: (i) hexagonal boron nitride (hBN) platelets with different sizes and shapes; (ii) hBN platelets with carbon‐based fillers promoting the k_eff of the polyphenylene sulfide (PPS) composites. It explores the promotion of interconnectivity among the fillers in the PPS matrix, leading to higher k_eff, by the uses of hybrid fillers. It discusses using carbon‐based fillers as secondary fillers to tailor the PMCs' σ. Finally, it presents the effects of hybrid fillers on the PMCs' coefficient of thermal expansion. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Polymer composites with enhanced thermal conductivity via oriented boron nitride and alumina hybrid fillers assisted by 3-D printing

Herein, oriented boron nitride (BN)/alumina (Al₂O₃)/polydimethylsiloxane (PDMS) composites were obtained by filler orientation due to the shear-inducing effect via 3-D printing. The oriented BN platelets acted as a rapid highway for heat transfer in the matrix and resulted in a significant increase in the thermal conductivity along the orientation direction. Extra addition of spherical Al₂O₃ enhanced the fillers networks and resulted in the dramatic growth of slurry viscosity. This, together with filler orientation induced the synergism and provided large increases in the thermal conductivity. A high orientation degree of 90.65% and in-plane thermal conductivity of 3.64 W/(m∙K) were realized in the composites with oriented 35 wt% BN and 30 wt% Al₂O₃ hybrid fillers. We attributed the influence of filler orientation and hybrid fillers on the thermal conductivity to the decrease of thermal interface resistance of composites and proposed possible theoretical models for the thermal conductivity enhancement mechanisms.     

Study on thermal conductive PA6 composites with 3-dimensional structured boron nitride hybrids

To develop thermally conductive PA6 composites with the aim of decreasing filler content, structure-complexed fillers were fabricated. This research presented an effective approach by noncovalent functionalization of poly(dopamine) (PDA) followed by silver nanoparticles decoration to fabricate 3-dimensional (3-D) structured boron nitride hybrids (BN@PDA@AgNPs). BN hybrids were then introduced into PA6 to prepare thermally conductive PA6 composites. The results demonstrated that PA6/BN hybrids (PMB) composites exhibited higher thermal conducivity compared with PA6/BN composites, which revealed more effective construction of thermal conductive network in the composites with the addition of 3-D structured fillers. The effects of BN hybrids with different loadings on thermal stability, mechanical property, as well as electrical resistance of the composites were also analyzed. Overall, the prepared PMB composites exhibited outstanding performance in thermal conductivity, thermal stability, mechanical property, while retaining good electrical insulating property, which showed a potential application in electronic packaging fields. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47630.     

Highly antibacterial and toughened polystyrene composites with silver nanoparticles modified tetrapod‐like zinc oxide whiskers

In this work, high‐performance multifunctional composites were obtained by melt blending silver deposited tetrapod‐like zinc oxide whiskers (Ag‐ZnOw) with polystyrene (PS). The chemical, spectroscopic, antibacterial, mechanical, and morphological properties of the PS/Ag‐ZnOw composites were carefully investigated and discussed. The obtained PS/Ag‐ZnOw composites characterized remarkable antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Moreover, it is found that impact strength of the composite increase with increasing nanofiller concentration (up to 0.25 wt %). Morphological characterization of the impact fractured surface of composites revealed that toughening was achieved through uniform filler distribution in the polymer matrix, and anchoring effect was imparted by the tetrapod‐like shape of ZnO whiskers. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40900.     

Thermal conductivity improvement in electrically insulating silicone rubber composites by the construction of hybrid three-dimensional filler networks with boron nitride and carbon nanotubes

In this study, we constructed hybrid three-dimensional (3D) filler networks by simply incorporating a relatively low content of one-dimensional carbon nanotubes (CNTs; 0.0005–0.25 vol %) and a certain content of two-dimensional boron nitride (BN; 30 phr) in a silicone rubber (SIR) matrix. As indicated by transmission electron microscopy observation, flexible CNTs can serve as bridges to connect BN platelets in different layers to form hybrid 3D thermally conductive networks; this results in an increase in thermally conductive pathways, and the isolation between CNTs can prevent the formation of electrically conductive networks. Compared to the SIR–BN composite with the same BN content, the SIR–BN–CNT composites exhibited improved thermal conductivity, slightly increased volume resistivity, and comparable breakdown strength without a largely decreased flexibility. When 0.25 vol % CNTs were incorporated, the SIR–BN–CNT composite exhibited 75 and 25% higher thermal conductivities relative to the neat SIR and SIR–BN composite with 30 phr BN, respectively, and a thermal conductivity that was even comparable to SIR–BN composite with 40 phr BN. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46929.     

Mechanical and thermal properties of wood‐plastic composites reinforced with hexagonal boron nitride

Mechanical, thermal, and morphological properties of injection molded wood‐plastic composites (WPCs) prepared from poplar wood flour (50 wt%), thermoplastics (high density polyethlyne or polypropylene) with coupling agent (3 wt%), and hexagonal boron nitride (h‐BN) (2, 4, or 6 wt%) nanopowder were investigated. The flexural and tensile properties of WPCs significantly improved with increasing content of the h‐BN. Unlike the tensile and flexural properties, the notched izod impact strength of WPCs decreased with increasing content of h‐BN but it was higher than that of WPCs without the h‐BN. The WPCs containing h‐BN were stiffer than those without h‐BN. The tensile elongation at break values of WPCs increased with the addition of h‐BN. The differential scanning calorimetry (DSC) analysis showed that the crystallinity, melting enthalpy, and crystallization enthalpy of the WPCs increased with increasing content of the h‐BN. The increase in the crystallization peak temperature of WPCs indicated that h‐BN was the efficient nucleating agent for the thermoplastic composites to increase the crystallization rate. POLYM. COMPOS., 35:194–200, 2014. © 2013 Society of Plastics Engineers     

High thermally conductive PLA based composites with tailored hybrid network of hexagonal boron nitride and graphene nanoplatelets

Bio‐based polymers and multifunctional polymeric composites are promising for the development of new environmentally sustainable materials and are becoming increasingly popular compared to their oil based counterparts. This research aims to develop new multifunctional bio‐based polymer composites with improved thermal conductivity and tailored electrical properties to be used as heat management materials in the electronics industry. A series of parametric studies were conducted to clarify the science behind the hybrid composites' behavior and their structure‐to‐property relationships. Using bio‐based polymers [e.g., polylactic acid (PLA)] as the matrix, heat transfer networks were developed and structured by embedding hexagonal boron nitride (hBN) and graphene nanoplatelets (GNP) in a PLA matrix. The effects of random uniform thermal hybrid networks of hBN‐GNP on improving the effective thermal conductivity (k_eff) of produced composites were studied and compared. Composites were characterized with respect to physical, thermal, electrical, and mechanical properties for practical application in the electronics industry. The use of high thermally conductive hybrid filler systems, with optimized filler content, was found to promote the composites' effective thermal conductivity to more than 12 times over neat PLA. The thermally conductive composite is expected to provide unique opportunities to injection mold three‐dimensional, net‐shape, lightweight, and eco‐friendly microelectronic enclosures with superior heat dissipation performance. POLYM. COMPOS., 37:2196–2205, 2016. © 2015 Society of Plastics Engineers     

Studies on the strength and wear resistance of tetrapod‐shaped ZnO whisker–reinforced rubber composites

Zinc oxide whisker with a tetrapod shape was treated with a coupling agent using an orthogonal design and was mixed into the substrate of natural rubber to obtain the composites. The results of the experimental tests show that the tensile strength of the composites progressively increases with an increased amount of the related whisker. The experiments also indicate that the rubber reinforced by the tetrapod‐shaped ZnO whisker is distinct isotropy. The wear tests demonstrate that the composites containing ZnO whisker appear to have good wear‐resistance behavior. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1520–1525, 2001     

Effect of orientation and content of carbon based fillers on thermal conductivity of ethylene‐propylene‐diene/filler composites

In this study, synthetic graphite, carbon fiber, and carbon nanotube were used as thermal conductive fillers and ethylene‐propylene‐diene (EPDM) as matrix. Oriented EPDM/filler composites were prepared with two‐roll mill, and the effects of orientation and content of carbon based fillers on thermal conductivity and tensile strength of the composites were investigated. Parallel thermal conductivity of the oriented composites is significantly higher than normal thermal conductivity of the oriented composites. Especially, at 31.6% graphite content, parallel thermal conductivity of oriented composites is 7.14 W/mK. Very high thermal conductivity was achieved for oriented EPDM/graphite composites. Orientation of the fillers using two‐roll mill significantly improves the thermal conductivity in the orientation direction. For all the EPDM/filler composites, tensile strength of orientation direction is higher than that of normal direction. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41000.     

Noncovalent functionalization of boron nitride and its effect on the thermal conductivity of polycarbonate composites

Polycarbonate (PC) is an engineering thermoplastic with excellent insulation and mechanical properties. However, the low thermal conductivity restricted its application in electronic devices. Hexagonal boron nitride (h ‐BN) microparticle, a promising material with high thermal conductivity, was functionalized with cationic polyacrylamide (CPAM) and introduced into PC matrix to improve the thermal conductivity. SEM and XRD analysis showed that the modified BN (CBN) particles oriented and formed thermal conductive pathways within PC matrix. The formation of large‐area oriented CBN significantly improved the thermal conductivity and thermal stability of composites. At 20 wt % CBN loading, the thermal conductivity of 0.7341 Wm^?1 K^?1 and the temperature for 5% weight loss (T ₅) of 498.6 °C were obtained, which was 3.1 times and 77 °C higher than that of pure PC, respectively. Furthermore, outstanding electrical insulation property of matrix was retained in the composites. These results revealed that PC/CBN composite was a promising material for thermal management and electrical enclosure. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44978.