Effect of TMB-5 on dispersion of MWCNTs in iPP and crystallization of β-nucleated iPP/MWCNTs composites

In this work, multiwall-carbon-nanotubes (MWCNTs), β nucleating agent(TMB-5) and isotactic polypropylene(iPP) were mixed to prepare MWCNTs/iPP composites, which were processed by a corotating twin screw extruder at 270 °C. MWCNTs at 0 wt%, 0.05 wt%, 0.3 wt%, 1 wt%, 2 wt% and 3 wt% were added into the composites respectively and the concentration of TMB-5 was 0.3 wt% consistently. Polarized light microscopy (POM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and Wide-angle X-ray diffraction (WAXD) were used to study the dispersion of MWCNTs in the β-Nucleated iPP and the crystallization of the composites. SEM and TEM graphs showed that MWCNTs dispersed individually in the iPP matrix when TMB-5 was added in the composites. In the contrast, there were many aggregates of MWCNTs in iPP matrix without TMB-5. DSC and WAXD results indicate that TMB-5 and individual MWCNTs have a synergistic effect on inducing the formation of β crystals. However, with the content of MWCNTs increasing in the composites, β crystal content decreased and α crystal content increased, which indicated that MWCNTs aggregating in the iPP matrix acted as α nucleating agent restricting the formation of β crystals and the effect of TMB-5 on dispersion became limited at a relatively high MWCNTs content.     

Mechanical and thermal characteristics and morphology of polyamide 6/isotactic polypropylene blends in the presence of a β‐nucleating agent

The mechanical and thermal characteristics and morphology of polyamide 6 (PA6)/isotactic polypropylene (iPP) blends (10/90 w/w) prepared with different processing procedures and incorporated with an aryl amide nucleating agent, a kind of β‐nucleating agent (β‐NA) for iPP, were investigated. The yield strength and flexural modulus of the blends decreased as β‐NA was introduced into the blends, whereas the impact strength and elongation at break improved. The crystalline structures of the blends closely depended on (1) the processing conditions and (2) competition between the β‐nucleating effect of β‐NA and the α‐nucleating effect of PA6 for iPP. Scanning electron microscopy, differential scanning calorimetry, and X‐ray diffraction were adopted to reveal the microstructures of the blends. At a low β‐NA content (<0.1 wt %), the α‐phase iPP dominated the blends, whereas the relative content of the β‐phase iPP increased remarkably when the β‐NA content was not less than 0.1 wt %. The processing conditions also showed profound influences on the supermolecular structures of iPP; this resulted in different mechanical properties of the blends. As for PA6, the crystallization behavior and crystalline structure did not exhibit obvious changes, but PA6 did play an important role in the epitaxial crystallization of iPP on PA6. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Mechanical,Rheological, and Electrical Properties of Multiwalled Carbon Nanotube Reinforced Nanocomposites of 50/50 Acrylonitrile–Styrene–Acrylate/Zn+2 poly(ethylene-co-methacrylic acid) Ionomer Blend

The effect of variable amount of multiwalled carbon nanotubes on mechanical, rheological, and electrical properties of acrylonitrile–styrene–acrylate/Zn⁺²-poly(ethylene-co-methacrylic acid) ionomer blend system has been evaluated. Optical micrographs as well as alternating current conductivity data shows the formation of nanotube percolation network at 1 wt% nanotube content. The polymer/nanotube interaction increased the rate of tensile modulus to 55 GPa at low nanotube content. The polymer chain relaxation time was increased upto 1 wt% of nanotube content, but higher nanotube loading reduced the time. The zero-shear viscosity was function of nanotube content whereas the infinite-shear viscosity was independent of nanotube content.     

Improved conductivity and thermal stability by the formation of a charge‐transfer complex in β‐nucleation‐agent‐nucleated and MWCNT‐filled iPP composites

In this study, the influence of β‐nucleation agent (β‐NA) on the morphology and properties of multi‐walled carbon nanotube (MWCNT) filled isotactic polypropylene (iPP) composites was explored in details. The results show that the incorporation of β‐NA has promoted the dispersion of MWCNT in the iPP matrix, which is profitable for improving the thermal stability and conductivity properties of MWCNT‐iPP composites. Besides, the 0.05 wt % β‐NA nucleated samples exhibit higher impact toughness than that of un‐β‐NA‐nucleated ones. Further SEM observations show that the morphology of MWCNT changes from large agglomerations to small clusters with doping of β‐NA. The main reason is that the incorporation of β‐NA (TMB‐5) in MWCNT filled iPP matrix has led to the formation of a charge‐transfer complex. Some of these clusters act as nucleation sites for inducing crystallization of α spherulites, which have a compete growth with β‐NA induced β crystals. Meanwhile, other clusters exist in the inter‐lamella amorphous phase of β crystals, some of them even combine two adjacent β spherulites. Accordingly, a large conductive network comes into being. Based on the investigated results, a mechanism model is proposed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Photoelectrochemical properties of Fe-doped TiO2 nanotube arrays fabricated by anodization

Ti–Fe alloys with Fe contents of 0.05, 0.5 and 1.0 wt% were obtained using the arc-melting method. Fe-doped TiO₂ nanotube arrays were prepared by anodizing Ti–Fe alloys in ethylene glycol solution containing 0.25 wt% NH₄F and 10 wt% H₂O. The microstructure, crystal structure and photoelectrochemical properties of the nanotube arrays were characterized using scanning electron microscopy, X-ray diffraction, UV–Vis diffuse reflectance spectroscopy and electrochemical analyzer. Results show that doping of 0.05 wt% Fe improves the photoelectrochemical properties of titania nanotube arrays significantly, whilst further increasing the Fe contents to 0.5 and 1.0 wt% degrades these properties. The external potential has a considerable influence on the photocurrent density at doping content of 0.5 wt% Fe.     

Effect of carbon nanotube‐supported β nucleating agent on the thermal properties,morphology, and mechanical properties of polyamide 6/isotactic polypropylene blends

A new kind of β nucleating agent, multi‐wall carbon nanotube (MWCNT)‐supported calcium pimelate was introduced into polyamide 6 (PA 6)/isotactic polypropylene (iPP; 10/90 by weight) blend and the thermal properties, morphology, and mechanical properties were investigated. The results showed that β‐iPP appeared at low content of MWCNT‐supported calcium pimelate which surmounted the α‐nucleating effect of PA 6 for iPP, and the content of β‐iPP increased with increasing content of MWCNT‐supported calcium pimelate. The impact strength, elongation at break, and flexural modulus were improved with increasing content of MWCNT‐supported calcium pimelate without significantly deteriorating the tensile strength. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of nBaCO3 on mechanical,thermal and morphological properties of isotactic PP-EPDM blend

Isotactic polypropylene (iPP): ethylene propylene diene monomer (EPDM) blend is one of the most suited compatible and miscible blends. The blends of iPP and EPDM (80:20) filled with BaCO₃ nanoparticles (0.5, 1.5, 2.5 and 3 wt%) were prepared on Brabender Plasticorder, which was then subjected to injection molding to get dumbbell-shaped specimens. Meanwhile, BaCO₃ nanoparticles (nBaCO₃) were prepared using ultrasonic cavitation technique. The size and shape of nBaCO₃ particle was confirmed using transmission electron microscope and found to be capsule shape of diameter ~40–60 nm with aspect ratio (l/d) of 2.2–2.5. The reduction in particle size of nBaCO₃ leads to formation of uniform suspension. The solution was kept as such for long time so as to nullify the charges developed over the surface of nanoparticles. The mechanical properties of nBaCO₃-reinforced iPP-EPDM blends were studied using universal testing machine and impact tester. Moreover, thermal properties were studied using flammability tester, vicat softening temperature, thermo gravimetric analyzer and differential scanning calorimeter (DSC). Dispersion of nBaCO₃ in iPP-EPDM matrix was studied using scanning electron microscope and X-ray diffractometer. The mechanical and thermal properties of iPP-EPDM/nBaCO₃ blends were found to be improved significantly with increasing amount of nBaCO₃ up to 2.5 wt%, which is due to good compatibility in between iPP and EPDM with uniform dispersion of nBaCO₃. Moreover, due to agglomeration at 3 wt% loading of nBaCO₃ few of the properties found to be decreased marginally.     

A novel β‐nucleating agent for isotactic polypropylene

The nucleating ability of p‐cyclohexylamide carboxybenzene (β‐NA) towards isotactic polypropylene (iPP) was investigated by differential scanning calorimetry, X‐ray diffraction, polarized optical microscopy and scanning electron microscopy. β‐NA is identified to have dual nucleating ability for α‐iPP and β‐iPP under appropriate kinetic conditions. The formation of β‐iPP is dependent on the content of β‐NA. The content of β‐phase can reach as high as 96.96% with the addition of only 0.05 wt% β‐NA. Under non‐isothermal crystallization the content of β‐iPP increases with increasing cooling rate. The maximum β‐crystal content is obtained at a cooling rate of 40 °C min^–1. The supermolecular structure of the β‐iPP is identified as a leaf‐like transcrystalline structure with an ordered lamellae arrangement perpendicular to the special surface of β‐NA. Under isothermal crystallization β‐crystals can be formed in the temperature range 80–140 °C. The content of β‐crystals reaches its maximum value at a crystallization temperature of 130 °C. © 2012 Society of Chemical Industry     

The effects of melt vibration blending on the subsequent crystallization and melting behavior of polypropylene/ultra high molecular weight polyethylene

Pure isotactic polypropylene (iPP) and 90/10 wt iPP/ultra high molecular weight polyethylene (UHMWPE) blends, prepared by a novel vibration internal mixer reformed from a coventional internal mixer via parallel superposition of an oscillatory shear on a steady shear, were investigated by differential scanning calorimetry (DSC) and wide angle X‐ray diffraction. After plasticating pure iPP in the vibration field, the number of β form crystals of iPP was increased. The β form exhibited a single DSC melting peak different from that of the bulk α form crystals of iPP. After mixing of UHMWPE with iPP, the melting point of the UHMWPE component shifted to a lower temperature. For blends mixed at the higher‐frequency and/or larger‐amplitude vibrations, the melting point of the UHMWPE component was further gently lowered while the bulk melting point of the iPP component was slightly increased. The crystallization peaks of the two components overlapped into one single peak, and the total crystallinity became higher, together with a larger amount of the β iPP. These results showed that the two components influenced each other in blending. Hence, the resultant morphology affected the subsequent crystallization and melting behaviors. Additionally, vibration in mixing possibly affected the conformation of some polypropylene chains to favor the subsequent packing in the β form.     

Interphase layer formation in isotactic polypropylene/ethylene–propylene rubber blends

The influence of the interphase layer, formed by the introduction of an oil in ethylene–propylene rubber (EPR), on the structure and properties of isotactic polypropylene (iPP)/EPR blends was studied. The dispersity of the rubber phase in the iPP matrix did not depend on presence of oil. The melting temperature of iPP decreased with increasing content of oil‐extended EPR, and it did not change if the oil was absent. The compatibility parameter was determined from the dependency of the iPP melting point on the rubber content with the Nishi–Wang equation. A negative value of the parameter indicated a limited compatibility of iPP with oil‐extended EPR. The latter also reduced the temperature and heat of crystallization of iPP. The mechanical properties of iPP/EPR blends were investigated as functions of temperature and elongation rate. It appeared that elastic modulus and yield stress of the blends linearly depended on the logarithm of the elongation rate. Activation volumes, calculated with the Eyring equation, increased with increasing content of elastomer; moreover, this increase was more pronounced for the oil‐extended elastomer. It is suggested that the oil influenced the structure of the interphase layer and, accordingly, the characteristics of the iPP/EPR blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 249–257, 2003     

Morphology and mechanical properties of polypropylene and poly(ethylene‐co‐methyl acrylate) blends

The morphology and mechanical properties of isotactic polypropylene (iPP) and poly(ethylene‐co‐methyl acrylate) (EMA) blends were investigated. Various EMA copolymers with different methyl acrylate (MA) comonomer content were used. iPP and EMA formed immiscible blends over the composition range studied. The crystallization and melting reflected that of the individual components and the crystallinity was not greatly affected. The size of the iPP crystals was larger in the blends than those of pure iPP, indicating that EMA may have reduced the nucleation density of the iPP; however, the growth rate of the iPP crystals was found to remain constant. The tensile elongation at break was greatly increased by the presence of EMA, although the modulus remained approximately constant until the EMA composition was greater than 20%. EMA with a 9.0% MA content provided the optimum effect on the mechanical properties of the blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 175–185, 2003     

Morphological,Dynamic Mechanical,Creep and Weathering Behavior of Carbon Nanotube-Reinforced 50/50 ASA/Zn-Ionomer Blend

The nanocomposite of 50/50 acrylonitrile styrene acrylate/Zn-ionomer blend uses varying weight ratios (0.5–5.0%) of multiwalled carbon nanotubes. The morphological, thermal, thermomechanical, and creep behavior along with metal adhesion were evaluated. The phase-separated surface morphology of the blend formed non-uniform microscale nanotube dispersion and resulted in nanotube network formation at 1 wt%. Lowest creep compliance and increased complex modulus were found at 1 wt% nanotube loading. The presence of weather resistant acrylonitrile styrene acrylate and carbon nanotubes made the nanocomposite excellent weather resistant.     

Greatly improved toughness of isotactic polypropylene blends with traces of carbon nanotubes

In this work, the β‐nucleated isotactic polypropylene (iPP)/ ethylene‐octene copolymer (POE) blends demonstrated greatly enhanced impact toughness by adding traces of carbon nanotubes (CNTs) (only 0.05 wt%). When the POE content was 30 wt%, the impact strength of β‐nucleated iPP/POE blends with CNTs was as high as 51.7 kJ/m², about 5.6 kJ/m² higher than β‐nucleated iPP/POE blends, 15.2 kJ/m² higher than CNTs‐filled iPP/POE blends, and almost 19 times of pure iPP sample. This significantly improved impact toughness was considered to be attributed to the shear yielding and multiple‐crazing, originating from the presence of abundant β‐crystals in the iPP matrix, the enhanced mobility of the molecular chains in the confined amorphous region of iPP lamellae and the homogenous distribution of POE dispersed phase with a small size, indicating the synergistic effect of CNTs, β‐nucleating agent and POE on the toughness of iPP. POLYM. ENG. SCI., 59:757–764, 2019. © 2018 Society of Plastics Engineers     

Crystallization behaviour of isotactic polypropylene/linear low density polyethylene blends

Crystallization behaviour of isotactic polypropylene/linear low density polyethylene (iPP/LLDPE) blends has been investigated by optical microscopy and DSC. Crystallization of iPP depends upon blend composition and thermal history. When blended with LLDPE, the crystallization temperature of iPP, T_c, decreased slightly. Crystallinity did not change in the range 0-80wt% LLDPE; there were only slight changes in the crystalline structure, but LLDPE seemed to resist forming the β type of spherulites. Below 80 wt% of LLDPE, iPP was a continuous phase. The iPP spherulite growth rate was almost constant; however, overall crystallization decreased due to decreasing primary nuclei density.     

Physical and mechanical behavior of single‐walled carbon nanotube/polypropylene/ethylene–propylene–diene rubber nanocomposites

The effects of the incorporation of single‐walled carbon nanotubes (SWNTs) on the physical and mechanical properties of thermoplastic elastomers based on blends of isotactic polypropylene (iPP) and ethylene–propylene–diene rubber (EPDM) are described. A marked decrease of the half‐time of PP–EPDM crystallization and a sensible increase of the overall crystallization rate were observed in the presence of SWNTs. These results confirmed the expected nucleant effect of nanotubes on the crystallization of polypropylene. This effect was not linearly dependent on the SWNTs' content, showing a saturation of the nucleant effect at high nanotube concentrations. Dynamic mechanical analysis results showed a significant and controversial change of the mechanical behavior of the PP–EPDM/SWNT composites depending on the nanotube content. In particular, the storage modulus increased at the lowest incorporation of SWNTs, whereas a further increase of nanotubes led to a reduction of the storage modulus with respect to the pristine polymer matrix. Raman spectroscopy and scanning electron microscopy were successfully applied to demonstrate that in the composite films, the changes in the crystallization kinetics and mechanical properties could be explained in terms of the changes of the distance between nanotubes in bundles after a different intercalation of the polymer matrix. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2657–2663, 2003     

Structure and properties of new reversibly crosslinked iPP/LDPE blends

Reversibly crosslinked blends of isotactic polypropylene and low density polyethylene (iPP/LDPE) were prepared in the presence of crosslinking agents using reactive extrusion. The structure and properties of the modified blends were investigated by means of wide-angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), and macro- and micro-mechanical measurements. The crystallinity of the modified samples (LDPE, iPP, and their blends) does not seem to be so much affected by the crosslinking process. Results show that the microhardness of the iPP/LDPE blends notably increases with the iPP content. The micromechanical properties of the modified blends only improve slightly as a consequence of the crosslinking process. In the iPP samples, and also in the iPP/LDPE blends, this process gives rise to the appearance of new, crystalline ethylenic chains, as evidenced by the calorimetric measurements. Furthermore, the impact strength of the modified materials is improved as compared with that of the original ones, while some of the crosslinked blends show a ductile fracture behavior. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

PROPERTIES OF POLYPROPYLENE/NATURAL RUBBER/RECYCLE RUBBER POWDER BLENDS

Thermoplastic elastomers have been prepared by blending polypropylene (PP), natural rubber (NR), and recycle rubber powder (RRP). The blends were melt-mixed using a Brabender Plasticorder torque rheometer at 190°C and 50 rpm. A fixed 70:30 blend ratio (wt%) of PP and rubber was prepared. The effect of partial replacement of NR with RRP at a fixed rubber content (NR+RRP), 30 wt% on mechanical properties, swelling behavior, torque development, and morphological properties of PP/NR/RRP blends was studied. Results show that the tensile strength, Young's modulus, and swelling resistance increase with increasing RRP content in the PP/NR/RRP blends whereas the stabilization torque and elongation at break exhibit opposite trend.     

Mechanical and Morphological Properties of Polypropylene and Regenerated Tire-Rubber Blends

Mechanical properties and morphology of blends prepared from polypropylene (PP) and 5–20 wt% of regenerated tire-rubber (RgR) were studied. The samples were prepared in a twin-screw extruder. The addition of maleic anhydride-functionalized polypropylene (PP-g-MAH) was also investigated. Tensile and flexural moduli, tensile strength at break, elongation at break and Izod impact resistance at 23°C were increased by the addition of 15 wt% of regenerated rubber and 5 wt% of PP-g-MAH. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) analyses showed some interaction between PP and RgR and considerable modification of the compatibilized mixture morphology. The fracture surface of the blend with PP-g-MAH showed a better interaction between the PP matrix and the regenerated rubber domains, for all blends. Well-dispersed particles of the rubber in the polypropylene matrix were observed. DSC showed that PP crystallizes on cooling at lower temperatures as the RgR content increases. The decrease in crystallization temperature is more evident for blends with 5 wt% PP-g-MAH.     

Synthesis and properties of polyamide/LLDPE composites with compatibilizer used as hot melt adhesive

In this work, a new polyamide (PA155) was synthesized from higher purity dimer acid, sebacic acid, ethylenediamine, and piperazine, and the ternary blends were prepared by blending PA155 with LLDPE in the presence of the compatibilizer, maleic anhydride grafted linear low-density polyethylene (LLDPE-g-MAH). The weight ratio of PA155 to LLDPE of the samples was kept constant at 80/20 and the amount of LLDPE-g-MAH was varied at 0, 3, 6, 9, and 12 wt% over the total weight of the blend respectively. The scanning electron microscope and mechanical properties tests showed that the compatibility and the mechanical properties were improved with the increase in LLDPE-g-MAH content, and the blend containing 9.0 wt% LLDPE-g-MAH exhibits an optimal miscibility behavior and mechanical properties. The hot melt adhesives which were prepared from the ternary blends were assessed by 180°peel tests of Al/adhesive/polypropylene stack. The peeling strength for the sample containing 9.0 wt% compatibilizer (82.5 N/2.5 cm) is much more than that of the samples without compatibilizer (<20 N/2.5 cm).     

Studies on Ethylene Propylene Diene Rubber and Thermoplastic Polyurethane Blends: The Effect of Maleation

Blends of maleated ethylene propylene diene rubber (EPDM) and thermoplastic polyurethane (TPU) have been studied to understand the effect of the maleation level of EPDM on the compatibility and morphology of the blends. Blends with different maleation levels on EPDM (0.25, 0.50, and 0.75 wt%) were compared for mechanical, thermal, and other properties. The appearance of single T _g for 0.5% and 0.75% confirms that a maleation level of more than 0.5 wt% is required for EPDM blends with TPU. However, best mechanical properties are obtained for 0.5% maleated EPDM and TPU blends. Aging, filler reinforcement, and weather resistance measurements were also studied for the blends of varying maleation levels.