Polypropylene Nanocomposites Research Articles

Enhanced breakdown strength of the BaTiO3/polypropylene nanocomposite film based on the biaxial stretching process

AbstractThe significant progresses of polymer‐based nanocomposites with improved dielectric performances are urgently calling for an effect way to realise commercial production. Up to now, the biaxial stretching technology is still a powerful method to produce the high‐performance dielectric films applied in the film capacitors due to its full‐blown applications. In this work, a classical composite system of BaTiO3/polypropylene was applied to reveal the connection between the microstructure changes and dielectric properties of the corresponding nanocomposite films in the biaxial stretching process. The permittivity of BT‐30 wt% nanocomposite reached 2.8 at 103 Hz after stretching, and its breakdown strength reached 340 MV/m. In addition, the breakdown strength of BT‐10 wt% nanocomposite could even be promoted to 452 MV/m, which was 1.3 times higher than that before stretching. The microstructure test demonstrated that the rearrangement of nanofillers, high crystallinity and the oriented polypropylene crystals were advantageous to the improvement of breakdown strength for the stretched nanocomposite films. Therefore, the application of biaxial stretching technology into the preparation of nanocomposite dielectric film is an enormous potential way for the energy storage film capacitors.

Friction stir welding of polypropylene based graphene nanocomposites fabricated with 3-D printing: An investigation on the microstructure and mechanical properties

Polymer nanocomposites find diverse applications in the aerospace, automobile and electronic industries due to good corrosion resistance, high specific strength and excellent processing ability. However, the production of complex and larger parts typically requires welding technology. In this research, fused filament fabrication technique was used to prepare polypropylene nanocomposite reinforced with graphene nanoplates. The polypropylene/graphene nanocomposites were then joined using the friction stir welding. Afterward, different analyses such as thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy, tensile testing and hardness testing were applied to examine the effects of the process parameters on the microstructure and mechanical properties of the nanocomposite. The results of thermal analysis indicated that the addition of graphene nanoplates improved the melting point and crystallinity percentage of the polypropylene nanocomposite. Mechanical characterization of the welded samples indicated that the increase of rotational speed from 500 to 750 rpm enhanced the tensile strength of weld joint, while it reduced the hardness. Moreover, an increase in the welding speed from 10 to 30 mm/min resulted in a reduction in the tensile strength and an improvement in the hardness. The highest tensile strength of the weld was obtained by addition of 1 wt% graphene to polypropylene, whereas the hardness of the weld was maximized by addition of 2 wt% graphene. Nevertheless, the desirable combination of the process parameters for simultaneous enhancement of tensile strength and hardness was achieved by rotational speed of 667 rpm, welding speed of 16 mm/min and graphene content of 1.5 wt%.

Polypropylene (PP) nanocomposites with transition metal (MgCoAl, MgNiAl, MgCuAl, MgZnAl) layered double hydroxides (t-LDHs): Flammability, thermal and mechanical analysis

Over the last few years, transition metal based LDHs are drawing more and more attention. This is especially true for tri-metal LDHs due to their wide range of applications. This research work highlights four types of tri-metal layered double hydroxide (t-LDH) that were synthesized and used in polypropylene (PP) nanocomposites. The effect and interaction of cobalt (Co), nickel (Ni), copper (Cu) and zinc (Zn) containing MgAl LDHs in PP nanocomposite were prepared and tested. These t-LDHs (MgCoAl, MgNiAl, MgCuAl, MgZnAl) were synthesized using the urea hydrolysis method. The t-LDH/PP nanocomposites were prepared using melt mixing in a small-scale compounder. Structural and morphological analysis of t-LDH and their PP nanocomposites were done using XRD spectroscopy and SEM. The thermal behaviour of the nanocomposites was studied using DSC and TGA. Rheological analysis was done using a rheometer, flammability was analysed using limiting oxygen index (LOI) and UL94 testing. Mechanical properties were compared by a UTM and Charpy impact test. The thermal stability, flame retardancy and mechanical strength are increased with the addition of these t-LDHs. MgCuAl/PP nanocomposites showed superior thermal and mechanical properties as compared to MgAl/PP, MgCoAl/PP, MgNiAl/PP, MgZnAl/PP nanocomposites. In comparison to pure PP with the addition of only 5 wt.% of MgCuAl-LDH the degradation temperature was 43 °C higher.

Nanocellulose reinforced lightweight composites produced from cotton waste via integrated nanofibrillation and compounding

Cotton is a natural fiber containing more than 95% of cellulose. With worldwide cotton consumption continuously increasing, the amount of cotton waste generated is enormous. Most of the cotton waste ends up in landfill or incinerators, resulting in a huge waste of this excellent natural resource. In this project, cotton waste was recycled to produce polypropylene nanocomposites. Instead of using the traditional two-step nanofiber extraction and compounding technique, an integrated process was adopted to combine nanofibrillation and compounding into one step. Results showed that cotton fibers with a slight prefibrillation and hydrophobic surface modification were successfully fibrillated into tens to hundreds of nanometers in width during compounding. The nanofibers reinforced polypropylene composites exhibited significantly enhanced tensile and flexural strength and moduli. For instance, when 30% fibers from bleached white and indigo-dyed denim fabrics were introduced, the tensile moduli of the resultant composites reached 4.57 and 4.59 GPa, respectively, compared to 1.60 GPa, the modulus of neat PP. Meanwhile, denim fabrics had a remarkable reinforcing effect on the composites’ impact strength attributing to the hydrophobic indigo dyes that improved the interfacial bonding between cotton fibers and the matrix. The highest impact strength of denim reinforced composites was 4.96 kJ/m2 with 20% fiber loading; while the impact strength of neat polypropylene was 2.46 kJ/m2. The low water uptake of the composites further indicated the excellent adhesion at the filler/matrix interface. In general, a very promising processing technique to recycle cotton waste for high-value products was demonstrated.

The Effects of Humidity on Dielectric Permittivity of Surface-Modified TiO₂- and MgO-Based Polypropylene Nanocomposites

This work reports on the effects of titanium dioxide (TiO2) and magnesium oxide (MgO) nanofillers modified with polar silane coupling agents (SCAs) on the dielectric response of polypropylene (PP) nanocomposites, in the presence of water molecules. A thermogravimetric analysis (TGA) demonstrates that the surface structure of the SCA layer between TiO2 and MgO is significantly different, since the SCA graft density of MgO is ten times higher than for TiO2. Surface-modified nanofillers tend to agglomerate, and that the distribution is determined by the polarity of the surface functional groups. Agglomerations in methacrylate systems are similar in size to those found in untreated samples (3– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5~\mu \text{m}$ </tex-math></inline-formula> ), while those with amino functional groups are reduced to 1– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2~\mu \text{m}$ </tex-math></inline-formula> . Nanoparticles also act as nucleating agents, which increases the crystallization temperature by 7 °C–8 °C compared with neat PP. The measured increase in relative permittivity in the composites is attributed to absorbed water. Surface modification significantly reduces this increase, especially in MgO samples. Relaxation peak frequencies vary, depending on the water bonding states, due to differences in polarities of the respective surface functional groups. Two overlapping dielectric mechanisms of dipolar and interfacial relaxation can be detected, especially at low frequencies (LFs; 20 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> Hz) in TiO2 samples. Ethoxy-modified samples containing amino functional groups have the lowest dielectric permittivity under humid conditions.

Enabling High-Performance Polypropylene Nanocomposites With Interfacial Deep Traps

Polymer nanocomposites are the material of choice for dc insulation. The emerging demand for high-capacity high voltage direct current (HVdc) power transmission requires polymer nanocomposites capable of safe and stable operation at high temperatures. However, the high-temperature electrical properties of current polymer nanocomposites are still unsatisfactory. Here, we report that the modulation of polymer/nanoparticle interfaces can greatly improve the high-temperature insulation properties of polypropylene (PP)-based nanocomposite for recyclable HVdc cable insulation application. The nanoparticles are surface-modified with PP-graft-maleic anhydride (PP- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${g}$ </tex-math></inline-formula> -mah), which is not only well miscible with PP but also contains polar groups to act as interfacial deep traps. We demonstrate that the interfacial deep traps can improve the dc breakdown strength and the electrical resistivity of polymer nanocomposite by inhibiting the charge injection. This work deepens the understanding of interfacial effects in polymer nanocomposites and provides new opportunities for designing high-performance recyclable insulation materials for HVdc cables.

Highly conductive polypropylene nanocomposites containing copper nanowire

AbstractHighly thermally and electrically conductive polypropylene (PP) nanocomposites were prepared by incorporating high‐aspect‐ratio copper nanowires (CuNW). Surface treatment of the CuNW was important for dispersion and compatibility. A CuNW network was first embedded in a PP matrix, followed by removal of the protective layer on CuNW. At a volume fraction of 2.5%, the thermal conductivity was enhanced by 234% compared to the neat PP. The electrical conductivity significantly increased to 500 S/cm, which is 16 orders of magnitude greater than the neat PP. This PP nanocomposite is attractive for housings for electronic devices and antistatic packaging.

Nanomechanical and thermomechanical evaluation of polypropylene nanocomposites containing functionalized boron nitride decorated with barium titanate

ABSTRACT This study developed polypropylene (PP) nanocomposites containing surface-functionalized boron nitride (BN) decorated with BaTiO3 (BT). The developed nanocomposites showed well-dispersed nanoparticles in the PP matrix. The nanocomposites showed optimal hardness, elastic modulus, and stiffness of about 166.6 MPa, 2.7 GPa, and 0.12 mN/nm for PP/15BN-5BT nanocomposite compared to 79.4 MPa, 1.7 GPa, and 0.089 mN/nm measured for the pure PP, which are increments of about 110%, 59%, and 35% respectively. Heat deflection temperature and dynamic mechanical properties were also enhanced. Therefore, this study discussed the effects of BN decorated with BT on the nanomechanical and thermomechanical properties of PP nanocomposites.

HACIA LA COPOLIMERIZACIÓN DE NANOCOMPUESTOS DE PROPILENO ESTEREOESPECÍFICOS CON COMONÓMEROS POLARES MEDIANTE POLIMERIZACIÓN IN SITU. OPTIMIZACIÓN DE LAS PROPIEDADES MECÁNICAS.

The use of different stereospecific metallocene catalysts: isotactic (iPP, C2-symmetry) and syndiotactic (sPP, Cs-symmetry) has been investigated in order to improve the mechanical properties of polypropylene/nanoclay nanocomposites obtained by in-situ polymerisation. Stereoregular nanocomposites have been synthetized in the presence of polar comonomers (1-undecenol (R-OH) and acid-undecenoic (R-COOH) for improving the matrix-nanoclay chemical compatibility. An important study of variables: amount of nanoparticles used as co-catalyst support, type of catalyst, type and amount of comonomer have been studied in a full factorial design of experiments in order to identify the main factors that achieve a balance between the stiffness and toughness of the polypropylene nanocomposites. Important results were found from ANOVA (analysis of variance): the nanoclay has a greater influence on the syndiotactic configuration and, the amount of polar comonomer is the main factor in maximising mechanical properties, irrespective of stereospecificity of the polypropylene nanocomposites. &nbsp

Hydrophobization of nanodiamond for polypropylene nanocomposites

Purified and de-aggregated nanodiamonds (ND) synthesized by detonation of explosives provide high surface to volume ratio and unique modification opportunities of their surface groups. In general, ND possesses polar groups, therefore, easily forms agglomerates in non-polar polymer matrix. In this study, the effects of hydrophobization of ND on the structure and the properties of polypropylene (PP) nanocomposites were investigated. Long alkyl chains of octadecyl amine (ODA) were introduced on the surface of ND with the substitution ratio of 68 %. The structural study showed that the dispersibility of ND was remarkably improved by the hydrophobization so that the PP/ND-ODA nanocomposites showed higher transparency than that of the PP/ND nanocomposites. The increased crystallinity of PP in the nanocomposites indicates that ND and ND-ODA acted as crystallization nuclei in the nanocomposites. As for the mechanical properties, the increased Young's modulus of PP/ND nanocomposites was further increased by the addition of ND-ODA. The Young's modulus of the nanocomposites with 0.5 wt% ND-ODA was 64 % higher than that of PP. The strong reinforcement effects also appeared as high heat resistances of the nanocomposites.

Hygroscopic Behavior of Polypropylene Nanocomposites Filled with Graphene Functionalized by Alkylated Chains.

Owing to stringent international environmental and fuel efficiency requirements for lightweight automotive systems, polymer composites have attracted widespread attention. Polypropylene (PP) is a widely employed commercial polymer because of its lightweight and low cost. In this study, PP nanocomposites were fabricated to reduce the moisture absorption of PP composites in automotive headlamp housings. Alkylated chemically modified graphene (CMG-R) was synthesized to reduce the surface hydrophilicity of graphene and increase compatibility with the PP matrix. Fourier transform-infrared spectroscopy and scanning electron microscopy were performed to analyze the nanofillers. X-ray diffraction was performed to determine the interlayer spacing of the nanofiller resulting from surface treatment. Differential scanning calorimetry was used to analyze the crystallinity of the nanocomposites. The results indicated that the improved hydrophobicity of the nanofiller due to alkylation reduced the maximum moisture absorption of the PP nanocomposites by 15% compared to PP composites. The findings of this study are useful for reducing fogging in automotive headlamps.

Characterisation of Nanoclay and Spelt Husk Microfiller-Modified Polypropylene Composites.

Current research is devoted to the investigation of spelt husk (SH) and nanoclay-modified compatibilised polypropylene (PP) binary and ternary composites for injection-moulding applications. PP composites were obtained using twin-screw extrusion. The content of mechanically milled SH microfiller with aspect ratio within 2 and 6 was fixed at 40 wt.%, whereas the amount of nanoclay functional filler in the polypropylene matrix was changed in the range from 0.5 to 5 wt.%. Nanoclay filler was introduced in the polypropylene matrix either in the form of nanoclay powder (C) or as a masterbatch (M). Regular distribution of the clay nanofiller within the polymer matrix has been observed, disregarding its form and concentration. The effects of the individual or combined addition of SH microreinforcement and nanoclay fillers on the rheological, mechanical, calorimetric, and thermal properties of the developed PP composites were investigated. It is revealed that the addition of the nanoclay fillers insignificantly influences the viscosity of both PP nanocomposites and hybrid composites with SH. Additionally, for PP nanocomposites, remarkable increases in tensile and flexural modules and strength are observed by maintaining considerable ultimate deformations, mainly in the case of M-containing systems. Concomitantly, because of the addition of the nanoclay filler, the improvement in thermal stability of PP nanocomposites and PP hybrid composites with SH is observed. As a result of SH addition, considerable increases in tensile and flexural modules are also observed. Results of the research demonstrate the potential of the use of natural materials (agricultural residues and clay minerals) for the development of PP composites with increased stiffness and thermal properties.

An innovative binary nano-catalytic flame retardant system for improving the fire safety performance of polypropylene

• The combined catalytic charring and flame-retardant strategy was proposed. • The binary nano-catalytic system exhibits excellent flame-retardant performance. • The catalytic charring and flame-retardant mechanisms are well documented. Phosphomolybdic acid-modified reduced graphene oxide (RGO-PMoA) and nickel nanoparticles loaded with reduced graphene oxide (RGO-Ni) were synthesized. An innovative binary nano-catalytic flame-retardant system was designed and incorporated into the polypropylene (PP) matrix. Thermal stability and decomposition behaviors of PP nanocomposites were explored by Thermogravimetric analysis and Thermogravimetric-mass spectrometry, respectively. Fire behaviors of PP and its nanocomposites were investigated by cone calorimeter test. This binary nano-catalytic system with the optimal ratio is much more efficient than RGO-PMoA or RGO-Ni alone in improving the thermal stability and char yield, resulting in better flame retardancy. This combined catalytic system significantly reduces PP's peak heat release rate and total heat release. Its catalytic charring and flame-retardant mechanisms are revealed. RGO-PMoA, with solid acid characteristics, acts as a pyrolysis catalyst to accelerate the aromatization of PP’s decomposition products, and then the carbonization reaction catalyzed by RGO-Ni will be favorable. This work proposes a novel “combined catalytic charring strategy”, which integrates the advantages of nano-flame retardant technology and catalytic charring.

Effects of Nanofillers Based on Cetyltrimethylammonium-Modified Clays in a Polypropylene Nanocomposite.

Nanocomposites of hydrophobic organo-clay/polypropylene (organo-clay/PP) were efficiently developed through a solution-blending technique. For this, we utilized various smectite clays as host agents; namely, Na-montmorillonite (Mt, ~1000 nm), Na-fluorine mica (Mica, ~1500 nm), and Na-hectorite (Ht, ~60 nm) with varied sizes, layer charges, and aspect ratios. Such clays were functionalized with cetyltrimethylammonium (CTA) bromide via an intercalation technique to obtain hydrophobic organic clays. The as-made clay particles were further mixed with a PP/xylene solution; the latter was removed to obtain the final product of the CTA-clay/PP nanocomposite. An X-ray diffraction (XRD) analysis confirmed that there were no characteristic (001) diffraction peaks for CTA-Mica in the PP nanocomposites containing CTA-Mica, assuring the fact that the Mica layers could be completely exfoliated and thereby homogenously composited within the PP. On the other hand, the CTA-Mt and CTA-Ht incorporated composites had broader (001) peaks, which might have been due to the partial exfoliation of CTA-Mt and CTA-Ht in the composites. Among the three CTA-clay/PP nanocomposites, the CTA-Mica nanohybrid showed an enhanced thermal stability by ~42 °C compared to the intact host polymer matrix. We also noted that when the CTA-Mica content was ~9 mass % in the nanocomposites, the Young’s modulus was drastically maximized to 69%. Our preliminary results therefore validated that out of the three tested clay-PP nanocomposites, the CTA-Mica nanofiller served as the best one to improve both the thermal and mechanical properties of the PP nanocomposites.

A sustainable green electron reactive processing for fire safety of polypropylene nanocomposites

In this work, a sustainable green electron reactive processing for fire safety of polypropylene (PP) nanocomposites was designed and developed. Effect of electron reactive processing on the morphology, fire safety and tensile properties of PP nanocomposites were characterized. The results showed that the smoke production and heat release rate of PP nanocomposites were reduced by electron reactive processing. Moreover, the total heat release and rating level of PP nanocomposite in UL-94 measurement were not reduced by electron reactive processing. Furthermore, the quality of carbon layer of PP nanocomposites via electron reactive processing in the condensed-phase was also discussed. The results suggest that electron reactive processing is a sustainable green way toward fire safety of polymer nanocomposites without any negative influence on tensile properties.

Effect of aspect ratio, bulk density, and production date of multi-walled carbon nanotubes on the electrical conductivity of polypropylene and polycarbonate/multi-walled carbon nanotube nanocomposites

Effects of aspect ratio (AR), bulk density (BD), and fabrication date of multi-walled carbon nanotubes (MWCNTs) on the dispersion quality, electrical properties, and rheological properties were investigated for the nanocomposites of polypropylene and polycarbonate matrix. Six different MWCNTs with various AR and BD were adopted. Among six MWCNTs, two pairs have the same grade names but were produced on different dates. They are two Nanocyl NC7000s and two Hanwha CM130s. The two Nanocyl NC7000s produced on different dates showed different dispersion states and electrical resistivity for both PC and PP based nanocomposites. Characterizations of MWCNTs reveal that the length and diameter of two Nanocyl NC7000s are almost the same regardless of the production date, but the BD values of the two MWCNTs are significantly different. The same is noted for the two Hanwha CM130s. Therefore, the different electrical resistivity of the two nanocomposites using two MWCNTs of the same grade name but different production dates was attributed to the different BD. When comparing two nanocomposites with two MWCNTs (one has slightly higher AR and BD than the other), the nanocomposites with MWCNTs of lower AR and lower BD showed better dispersion and higher electrical conductivity. By various investigations with six MWCNTs, we concluded that BD is a very crucial factor in determining the electrical properties of polymer/MWCNT nanocomposites.

Upscale recycling of nonwoven polypropylene waste using a novel blending method

AbstractWaste management of the nonwoven polypropylene (PP) fabric has become an emerging issue due to its increased usage. This study presents the upscale recycling of PP nonwoven fabric scrap generated during medical‐grade disposable gown manufacturing. To prepare PP and carbon black (CB) nanocomposite, a two‐step novel melt blending process is used. A maximum density of 937 kg/m3, shore D hardness of 74.45, and highest improvement in UV degradation resistance with a carbonyl index of 0.40 is recorded at 2 wt% of the CB while melt flow index is the lowest at 0.5 wt% of the CB. The results of this study revealed the peak melting point (161.81°C), thermal degradation temperature (421°C), highest flexural strength (49.16 MPa), and Izod impact strength (6.76 kJ/m2) are at 0.50 wt% of CB loading. A morphological study indicated that the highest agglomeration of CB particles was found at 2 wt% CB. The results showed that the optimum value of CB in PP nanocomposite is 0.5 wt%, at which the majority of the properties are maximized. This research might pave the way for the recycling of nonwoven PP waste fabric and provide an alternative to the exciting virgin raw materials.

Mechanical, antibacterial, and non-cytotoxic performance of polypropylene nanocomposites reinforced with sTiO2 deposited with AgNPs mediated by quercetin biomolecule

Mechanical, antibacterial, and non-cytotoxic performance of polypropylene nanocomposites reinforced with sTiO2 deposited with AgNPs mediated by quercetin biomolecule

Nanoindentation of Multifunctional Smart Composites.

Three multifunctional smart composites for next-generation applications have been studied differently through versatile nanoindentation investigation techniques. They are used in order to determine peculiarities and specific properties for the different composites and to study the charge/matrix, charge/surface, or smart functions interactions. At first, a mapping indentation test was used to check the distribution of hardness and modulus across a large region to examine any non-uniformity due to structural anomalies or changes in properties for a carbon nanotubes (CNTs)-reinforced polypropylene (PP V-2) nanocomposite. This smart composite is suitable to be used in axial impeller fans and the results can be used to improve the process of the composite produced by injection moulding. Secondly, the interfacial properties of the carbon fibre (CF) and the resin were evaluated by a push-out method utilizing the smaller indentation tip to target the individual CF and apply load to measure its displacement under loads. This is useful to evaluate the effectiveness of the surface modification on the CFs, such as sizing. Finally, nanoindentation at different temperatures was used for the probing of the in situ response of smart shape memory polymer composite (SMPC) usable in grabbing devices for aerospace applications. Furthermore, the triggering temperature of the shape memory polymer response can be determined by observing the change of indentations after the heating and cooling cycles.

Dielectric film with high energy density based on polypropylene/maleic anhydride-grafted polypropylene/boron nitride nanosheet ternary system

With the development of advanced power system, high energy storage polymer film capacitors have attracted more and more attention. Polypropylene (PP) membrane is the most commonly used polymer based membrane, accounting for 70% of the total market share of products. Due to its low dielectric loss, it has a high charge-discharge efficiency (η). However, its inherently low dielectric constant (2.2 at 1 kHz) seriously hinders the increase of energy storage density (1–2 J/cm3). In this study, a ternary PP nanocomposite are prepared by melting blending and die pressing crosslinking, which greatly improved the capacitive properties of PP films. The discharge energy density (Ue) of PP nanocomposite films increased from 1.63 J/cm3 to 4.11 J/cm3 by adding a small amount (1 wt%) of BNNSs into PP matrix. Ue increased significantly (152.1%). By utilizing the special layered structure provided by BNNSs, the energy storage capacity of PP/ PP-g-MAH /BNNSs is significantly improved.