Processing and characterization of polyurethane nanocomposite foam reinforced with montmorillonite–carbon nanotube hybrids

This study investigates the effect of montmorillonite carbon nanotube hybrids on the final properties of polyurethane (PU) nanocomposite foams. The hybrids were fabricated by chemical vapour deposition and dispersed in rigid polyurethane foam by an in situ polymerization process. The resulting morphology and dispersion were evaluated by scanning electron microscopy, optical microscopy and transmission electron microscopy. PU nanocomposite foams have revealed the presence of cells of smaller size and an increase of cell density when compared to neat polymer foams. Thermogravimetric studies revealed that addition of the hybrids nanoparticles improve the thermal properties of the resulting nanocomposites. Addition of small amounts of montmorillonite carbon nanotube hybrids has enhanced the compressive properties of the resulting PU nanocomposite foams making it suitable for several applications.     

Optimization of the mechanical properties of polypropylene-based nanocomposite via the addition of a combination of organoclays

The properties of polypropylene (PP) nanocomposites are dependent on the quaternary ammonium salt in the montmorillonite (MMT). A nanocomposite with C-15A, which has a high cation exchange capacity (CEC), exhibits an increase in its impact properties, while one prepared with C-20A, which has a low CEC, shows an increase in the flexural modulus. In order to obtain enhancements in both properties, PP nanocomposites were prepared using a combination of 1:1 of C-15A/C-20A. X-ray, TEM, thermal properties, dynamical mechanical analysis (DMA), and mechanical tests were used to evaluate the properties of this novel mixture. Nanocomposites of partially exfoliated morphology were obtained, especially when 5 wt% of poly(propylene-graft-maleic anhydride) (PP-g-MA) was used. The mechanical tests showed that the use of a 1:1 mixture of C-15A/C-20A caused a simultaneous gain of approximately 12% in flexural modulus and a five times higher impact strength. In addition, the dispersion of the clay was more homogeneous, with the absence of agglomerated structures that were present when either the individual C-15A or C-20A was used. The DMA results showed that while the organoclay improved the modulus of PP, the T_g was decreased slightly.     

Morphological, rheological and mechanical characterization of polypropylene nanocomposite blends

In the present work, the effectiveness of styrene/ethylene-butylene/styrene rubbers grafted with maleic anhydride (MA) and a metallocene polyethylene (mPE) as toughening materials in binary and ternary blends with polypropylene and its nanocomposite as continuous phases was evaluated in terms of transmission electron microscopy (TEM), scanning electron microscopy (SEM), oscillatory shear flow and dynamic mechanical thermal analysis (DMA). The flexural modulus and heat distortion temperature values were determined as well. A metallocene polyethylene and a polyamide-6 were used as dispersed phases in these binary and ternary blends produced via melt blending in a corotating twin-screw extruder. Results showed that the compatibilized blends prepared without clay are tougher than those prepared with the nanocomposite of PP as the matrix phase and no significant changes in shear viscosity, melt elasticity, flexural or storage moduli and heat distortion temperature values were observed between them. However, the binary blend with a nanocomposite of PP as matrix and metallocene polyethylene phase exhibited better toughness, lower shear viscosity, flexural modulus, and heat distortion temperature values than that prepared with polyamide-6 as dispersed phase. These results are related to the degree of clay dispersion in the PP and to the type of morphology developed in the different blends.     

Experimental and theoretical analyses of mechanical properties of PP/PLA/clay nanocomposites

Compatibilized and non-compatibilized blends of polypropylene (PP) and poly(lactic acid) (PLA) with various compositions containing nanoclay particles were prepared by one step melt compounding in a twin screw extruder. Two nanocomposite systems with different matrices i.e. PP-rich (75/25 composition) containing Cloisite 15A and PLA-rich (25/75 composition) containing Cloisite 30B were selected for investigation of effect of nanoclays and n-butyl acrylate glycidyl methacrylate ethylene terpolymers (PTW) as compatibilizer on mechanical properties of PP/PLA/clay nanocomposites. Tensile and impact properties of the nanocomposite systems were investigated and correlated with their microstructures. Tensile modulus and strength of the blends were increased while elongation at break decreased by increasing PLA content. There was an irregular relationship between impact strength of the blends and PLA content. Several proposed models for blends and nanocomposites were used for prediction of tensile modulus of the samples. Most of the proposed models for blends could predict the tensile modulus of the blends successfully at low content of PLA. Another notable point was that most of the micromechanical models for nanocomposites fitted well to experimental values at low content of the clays and showed deviations at high clay loadings.     

Mechanical and tribological behavior of clay–polypropylene nanocomposites

This study deals with the wear rates and quasi-static mechanical properties of polypropylene (PP) infused with layered organo-modified montmorillonite nanoclays. Test results show that PP infused with 2 wt.% of organo-modified montmorillonite gives improved mechanical strength, higher fracture toughness, and lower wear rates. Transmission electron microscopy shows that the structure of the modified nanocomposite changes from an exfoliated structure at 1 wt.% nanoclay loading to an intercalated structures at 5 wt.% nanoclay loading. The general improvement in properties, which includes but not limited to the thermal barrier properties, may be attributed to the change in structure.     

Effects of modified hyperbranched polyester as a curing agent on the morphology and properties of dynamically cured polypropylene/polyurethane blends

The dynamic vulcanization process, usually used for the preparation of thermoplastic elastomers, has been applied to prepare polypropylene (PP)/polyurethane (PU) blends. Boltorn^TM H20 (H20) hyperbranched polyester containing 16 hydroxyl end gropus and pentaerythritol are used as curing agents, respectively, for curing PU oligomer during blending with molten PP. To improve the compatibility of cured PU particles with PP matrix, H20 is partly functionalized with stearic acid. The morphology, mechanical properties, thermal properties and melt flow index (MFI) of the PP/PU blends with different curing agent are investigated. Compared with pentaerythritol, SEM photographs show that H20 partly functionalized with stearic acid effectively reduces the size and size distribution of cured PU particles in PP/PU blends which also is proved by MFI measurement. Consequently, the dynamically cured PP/PU blends with modified H20 have better mechanical properties than those cured with pentaerythritol. The shifts of crystallization peaks to higher temperatures for all PP/PU blends indicate that PU particles in the blends can act as effective nucleating agents. Moreover, due to the smaller size of PU particles PP/PU blends cured with modified H20 have higher crystallization temperatures than those blends cured with pentaerythritol at the same PU content.     

RSMA增容PA6/PP共混物的形态结构与增容机理

采用ＲＳＭＡ为增容剂制备了ＰＡ６／ＰＰ共混物,研究了ＲＳＭＡ增容ＰＡ６／ＰＰ共混物的形态结构和热行为以及晶态结构,并探讨ＲＳＭＡ增容ＰＡ６／ＰＰ共混物的增容机理结果表明,ＰＡ６／ＰＰ共混物为热力不相容的海岛型两相结构,ＲＳＭＡ的加入改善ＢＰＡ６与ＰＰ相间的相容性,使两相分均匀,分散度提高。ＲＳＭＡ对ＰＡ／ＰＰ共混物的增容机理可用界面－分散相复合模型描述。     

Thermo-mechanical characteristics of thermally aged polyethylene/polypropylene blends

Polyethylene (PE), polypropylene (PP) and their blends have attracted a lot of attention due to their potential industrial applications. Therefore, the current work has been carried out with the main objective of investigating the impact of the thermal aging/treatment and blend ratio (composition range) on the mechanical (tensile and hardness) and thermal characteristics (using thermogravimetric analysis in a dynamic air atmosphere) of PE, PP and PE/PP binary blends. Samples of PE/PP blends containing 100/00, 75/25, 50/50, 25/75 and 0/100 wt.% were prepared via injection moulding technique and thermally treated/aged at 100 °C for 0, 2, 4, 7, 14 days. The tensile measurements indicated that the yield strength and the modulus decrease with increasing PE content. It was also observed that PE, PP and their blends deform in ductile modes. They undergo a uniform yielding over a wide range of deformation, which is followed by strain hardening and then failure. The strain to break for pure PE is found to be much higher than that for pure PP and for their blends, intermediate values have been observed. The hardness measurements have also revealed that increasing PE content in PE/PP blends reduced the hardness value of PP, however, thermal aging at 100 °C has not affected the polymers hardness which holds also true for the tensile properties, showing a good correlation between tested mechanical properties. The thermogravimetric analysis (TGA) in a dynamic air atmosphere and derivative thermogravimetric analysis (DTA) were conducted to study the thermal degradation and stability of thermally unaged and aged PE, PP and PE/PP blends in terms of the initial (T_d and T_d(1%)) and final (T_d(99%)) decomposition temperatures and maximum decomposition rate temperature (T_max). All polymers start to decompose at no less than 365 °C. As for mechanical properties, the blend ratio has affected the thermal properties however, aging time has not.     

Melt blend studies of nanoclay-filled polypropylene (PP)–high-density polyethylene (HDPE) composites

The objective of this work is to study how the rheological factors of unfilled and nanoclay-filled HDPE–PP blend series influence the structure, morphology, and mixing characteristics. For this study, a series of HDPE–PP blends (0–100 wt % HDPE), with and without nanoclay, was prepared by using melt-mixing method. Nanoclay was varied from 0 to 5 wt % in all the blend and polymer series. The rheological properties were examined by melt viscosity, scanning electron microscopy, and theory of mixing. The result indicated that the viscosity of the blend increased as HDPE and nanoclay content increased, and also affected the structure and morphology of the resulting blend. The thermal properties were examined by using differential scanning calorimetry and suggest improved crystalline and melting characteristics of PP and PP-rich phase of blend. The structure of nanoclay-filled blend was examined by X-ray diffraction and transmission electron microscopy, confirming the formation of nanocomposite with improved tensile properties.     

PP/PMMA接枝剑麻纤维复合材料的结构和性能

用注塑成型方法制备了PP／PMMA接枝剑麻纤维（SF）复合材料，研究了它的热性能、晶态结构、微观结构和力学性能。结果表明PMMA表面接枝的SF增强了PP与SF之间的作用力，改善了PP／SF的热稳定性，降低了PP相的熔点，同时SF的加入诱导了β－晶型PP的生成，提高了PP相的结晶度，降低了无定型PP的玻璃化转变温度。PMMA接枝的SF提高了PP的模量，对PP有明显的增韧效果。     

采用β成核动态硫化PP/EPDM共混物增韧聚丙烯

采用β成核的动态硫化iPP/EPDM共混物即热塑性硫化胶(TPV)改性聚丙烯,并与通用增韧剂聚烯烃弹性体(POE)、三元乙丙橡胶(EPDM)增韧聚丙烯进行比较,考察了增韧体系的力学性能、热性能和相形态.结果表明,随增韧剂含量的增加,增韧体系的拉伸屈服强度和弯曲模量均有所下降,而冲击强度提高.TPV改性体系的强度、模量和...     

PP-g-MAH对PP/OMMT纳米复合材料阻燃性能的影响

采用聚丙烯接枝马来酸酐(PP-g-MAH)作为相容剂,通过熔融插层法制备了具有阻燃性能的聚丙烯/有机蒙脱土(PP/OMMT)纳米复合材料。考察了相容剂、蒙脱土的用量等对纳米复合材料的阻燃性能的影响,并用X射线衍射(XRD)、透射电镜(TEM)和热重分析(TG)等对材料进行了表征。TEM照片和XRD结果,表明PP-g-MAH能够很好地改善OMMT与PP的相容性,OMMT能在基体中达到剥离。当OMMT和PP-g-MAH质量分数分别为5%和10%时,热释放速率峰值(PHRR)和平均热释放速率(MHRR)分别为491 kW/m2和286 kW/m2,比纯PP降低了42%和30%,TG分析表明PP/PP-g-MAH/OMMT纳米复合材料具有了更高的热稳定性。     

Morphology,rheology and mechanical properties of polypropylene/ethylene–octene copolymer/clay nanocomposites: Effects of the compatibilizer

The objective of this study was to investigate the effects of two compatibilizers, namely maleated polypropylene (PP-g-MA) and maleic anhydride grafted poly (ethylene-co-octene) (EOC-g-MA), on the morphology and thus properties of ternary nanocomposites of polypropylene (PP)/ethylene–octene copolymer (EOC)/clay nanocomposite. In this regard the nanocomposites and their neat polymer blend counterparts were processed twice using a twin screw extruder. X-ray diffraction, transmission electron microscopy, Energy dispersive X-ray spectroscopy, and scanning electron microscopy were utilized to characterize nanostructure and microstructure besides mechanical and rheological behaviors of the nanocomposites. Clay with intercalated structure was observed in EOC phase of the PP/EOC/clay nanocomposite. Better dispersion state of the intercalated clay in EOC phase was observed by adding EOC-g-MA as a compatibilizer. On the other hand, adding PP-g-MA resulted in migration of the intercalated clay from the EOC to the PP and to the interface regions. It was also demonstrated that the elastomer particles became smaller in size where clay was present. The finest and the most uniform morphology was found in the PP/EOC/clay nanocomposite. In addition, the rheological results illustrated a higher complex viscosity and storage modulus for PP/EOC/PP-g-MA/clay nanocomposite in which clay particles were present in the matrix. Mechanical assessments showed improvements in the toughness of the nanocomposites with respect to their neat blends, without significant change in stiffness and tensile strength values. These results highlight a toughening role of clay in the polymer blend nanocomposites studied.     

Compatibilizing effect of maleated polypropylene on the mechanical properties of injection molded polypropylene/polyamide 6/functionalized-TiO2 nanocomposites

TiO₂ nanoparticles were pretreated with excessive toluene-2,4-diisocyanate to synthesize TDI-functionalized TiO₂ (TiO₂-NCO), and then the polypropylene/polyamide 6/(PP/PA6, 70/30 wt%) blends containing 3 phr of the TDI-functionalized TiO₂ were prepared using twin-screw extruder followed by injection molding. Maleated polypropylene (PP-g-MAH) was used to compatibilize the blends. The mechanical properties of PP/PA6 blends based nanocomposites were studied through tensile and flexural tests. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to assess the fracture surface morphology and the dispersion of the TDI-functionalized TiO₂, respectively. The dynamic mechanical properties of PP/PA6 based nanocomposites were analyzed by using dynamic mechanical thermal analyzer (DMTA). The strength and stiffness of the PP/PA6 compounds were improved significantly in the presence of PP-g-MAH. This has been attributed to the synergistic effect of TDI-functionalized TiO₂ and PP-g-MAH. The PP-g-MAH compatibilized PP/PA6 compounds showed a homogeneous morphology supporting the compatibility improvement between PP, PA6 and TDI-functionalized TiO₂. TEM results revealed that the TDI-functionalized TiO₂ nanoparticles were exfoliated and uniformly dispersed in blends matrix. Possible chemical interactions between PP, PA6, TDI-functionalized TiO₂ and PP-g-MAH were proposed based on the experimental work.     

Crystal morphology,mechanical property and non-isothermal crystallization kinetics of poly(trimethylene terephthalate)/maleinized poly(ethylene-octene) copolymer binary blends

The crystal morphology, impact strength and nonisothermal crystallization kinetics of poly(trimethylene terephthalate)/maleinized poly(ethylene-octene) (PTT/PEO-MA) copolymer blends were studied by using the polarized optical microscopy, impact tester and differential scanning calorimetry (DSC). Avrami theory modified by Jeziorny, Ozawa and Mo theories were used to study the non-isothermal crystallization kinetics of the blends, respectively. The results suggest that these methods are suitable for analyzing the crystallization kinetics of the PTT/PEO-MA blends. The PEO-MA component, serving as a nucleation agent in blends, can increase the start crystallization temperatures and accelerate the crystallization rate of the blends. The crystal dimensions are predominantly three-dimensional growths, judged from the Avrami exponent n and the Ozawa exponent m, but the spherulites in blends are much smaller than those in pure PTT. The crystallization active energy suggests that the PEO-MA component can make the PTT component easy to crystallize in blends. The blend has the highest Izod impact strength as PEO-MA content is 3wt.%. Considering both the crystallization kinetic analyses results and the crystal morphology of the blends, the modified Avrami method is believed to be the most useful in reflecting the crystallization of the blends.     

Crystal morphology, mechanical property and non-isothermal crystallization kinetics of poly(trimethylene terephthalate)/maleinized poly(ethylene-octene) copolymer binary blends

The crystal morphology, impact strength and nonisothermal crystallization kinetics of poly(trimethylene terephthalate)/maleinized poly(ethylene-octene) (PTT/PEO-MA) copolymer blends were studied by using the polarized optical microscopy, impact tester and differential scanning calorimetry (DSC). Avrami theory modified by Jeziorny, Ozawa and Mo theories were used to study the non-isothermal crystallization kinetics of the blends, respectively. The results suggest that these methods are suitable for analyzing the crystallization kinetics of the PTT/PEO-MA blends. The PEO-MA component, serving as a nucleation agent in blends, can increase the start crystallization temperatures and accelerate the crystallization rate of the blends. The crystal dimensions are predominantly three-dimensional growths, judged from the Avrami exponent n and the Ozawa exponent m, but the spherulites in blends are much smaller than those in pure PTT. The crystallization active energy suggests that the PEO-MA component can make the PTT component easy to crystallize in blends. The blend has the highest Izod impact strength as PEO-MA content is 3 wt.%. Considering both the crystallization kinetic analyses results and the crystal morphology of the blends, the modified Avrami method is believed to be the most useful in reflecting the crystallization of the blends.     

Facile fabrication of CdTe/montmorillonite nanocomposite films with stable photoluminescence properties

We report herein the facile synthesis of CdTe/montmorillonite (MMT) nanocomposite films via charge-charge interactions between the CdTe quantum dots (QDs) and MMT platelets. Firstly, negatively charged CdTe QDs were prepared with the use of thioglycolic acid (TGA) as ligand. Then hybrid of the as-prepared TGA-stabilized CdTe QDs with sodium montmorillonite (Na-MMT) and cetyltrimethylammonium-modified montmorillonite (CTA-MMT), respectively, afforded novel CdTe/MMT nanocomposite films. The structure and optical properties of CdTe/MMT nanocomposite films were thoroughly investigated by scanning electron microscope (SEM), ultraviolet transmittance reflection and photoluminescence (PL) measurements. Results showed that CdTe/(CTA-MMT) nanocomposite films exhibited highly enhanced PL intensity compared with CdTe/(Na-MMT) nanocomposite films. More importantly, CdTe QDs in CdTe/(CTA-MMT) nanocomposite films well maintained PL properties even after thermal annealing at 100 °C for 10 h.     

Blends of PP/PE co‐octene for modified atmosphere packaging applications

The aim of this work was to obtain films of polypropylene (PP)/polyethylene co‐octene (POE) blends and study the influence of their composition and mixing conditions on final morphology and ultimate properties (thermal, mechanical, oxygen and water vapour transmission rates). Scanning electron microscopy showed segregation of POE domains in the PP matrix. Thermal analysis indicated that the addition of POE modified neither the melting temperature nor the crystallinity of PP in the pressed films. It was found that permeabilities of films were mainly related to POE content rather than morphological features. For the maximum POE concentration used (40%), the oxygen permeability increased up to ∼100% from that of neat PP. A similar trend was found for water vapour permeability. Rigidity of blends dropped significantly with the addition of POE although their ductility slightly increased when compared to pure PP. No significant effect of blend preparation conditions on these properties was found. Mechanical and permeability characteristics of films make them very attractive to be used for MAP of fresh produce such as apple, blueberry and mushroom. Copyright © 2011 John Wiley & Sons, Ltd.     

Development, structure and strength properties of PP/PMMA/FA blends

A new type of flyash filled PP/PMMA blend has been developed. Structural and thermal properties of flyash (FA) filled polypropylene (PP)/polymethyl methacrylate (PMMA) blend system have been determined and analysed. Filled polymer blends were developed on a single screw extruder. Strength and thermal properties of FA filled and unfilled PP/PMMA blends were determined. Addition of flyash imparted dimensional and thermal stability, which has been observed in scanning electron micrographs and in TGA plot. Increase of flyash concentration increased the initial degradation temperature of PP/PMMA blend. The increase of thermal stability has been explained based on increased mechanical interlocking of PP/PMMA chains inside the hollow structure of flyash.     

Mechanical, Thermal, Morphological and Rheological Properties of Polypropylene/Ultrahigh Molecular Weight Polyethylene Blends

In this study, the blends of polypropylene (PP) and ultrahigh molecular weight polyethylene (UHMWPE) were prepared by the four-and twin-screw extruders, and ethylene-propylene-diene monomer (EPDM), as the third component, was added to the binary blends. The mechanical.thermal, morphological and rheological properties of these two blends have been investigated.For the materials blended by the four-screw extruder, a 15 wt-% content of UHMWPE corresponds to a maximum lzod impact strength, and the miscibility enhancement effect of EPDM on PP/UHMWPE blends is very remarkable. Mechanical and thermal properties demonstrate that melt blending by the four-screw extruder is a better prcessing method for PP/UHMWPF blends than that by the twin-screw extruder. A co-continuous structure was observed in blends through TEM, and a novel "linear interpenetrating" toughening mechanism is proposed on the basis of this research work