Effect of Layered Silicates on the Crystallinity and Mechanical Properties of HDPE/MMT Nanocomposite Blown Films

Summary The highdensitypolyethylene (HDPE)/montmorillonite (MMT) nanocomposites were prepared by melt blending using twin screw extruder with two step process. The master batches were manufactured by melt compounding with maleic anhydride grafted HDPE (HDPE-g-MAH) and MMT. The HPDE/MMT master batches were subsequently mixed with HDPE. The blown nanocomposite films were obtained by a single screw extruder attached film blowing and take-off unit. The MMT dispersion in the nanocomposite films was characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM). The influence of MMT on the crystallinity, thermal properties and mechanical properties as a function of compatibilizer was investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and universal testing machine, respectively. X-ray and TEM images showed the partially exfoliated nanocomposites which have the 5:1 – 20:1 ratios of HPDE-g-MAH and MMT. The thermal and mechanical properties of nanocomposites were enhanced by increasing the contents of MMT and in the presence of compatibilizer.     

Photo-oxidative degradation of polypropylene/montmorillonite nanocomposites

The photo-oxidative behavior of the polypropylene (PP)/montmorillonite (MMT) nanocomposites and microcomposites has been investigated upon ultraviolet exposure using the technique of infrared spectroscopy. The rate of photo-oxidative degradation of PP/MMT nanocomposites is much faster than that of pure PP. The influence of pristine MMT, alkylammonium and compatibilizer were investigated, respectively. All these components can catalyze the photo-oxidation of PP matrix, in which the influence of compatibilizer and pristine MMT is primary. Moreover, the dispersion state of the clay particles in the polymer matrices has a little influence on the photo-oxidative degradation of polymer matrix. Consequently, an integrated catalysis mechanism of the photo-oxidative degradation of PP clay nanocomposite is proposed. It would provide benefit direction for the preparation and usage of polymer layered silicate nanocomposites (PLSN).     

Polypropylene-elastomer (TPO) nanocomposites: 1. Morphology

PP/PP-g-MA/MMT/elastomer nanocomposites were prepared in a twin-screw extruder at fixed 30 wt% elastomer and 0-7 wt% MMT content. The ratio of maleated polypropylene, PP-g-MA and organoclay was maintained at 1. Elastomer particle size and shape in the presence of MMT were evaluated for three different molecular weight grades of polypropylene (PP) and five different ethylene-co-octene elastomers (EOR) with different melt flow index (MFI) and octene contents. The MMT particles are located exclusively in the PP phase in the PP/PP-g-MA/MMT/EOR nanocomposites as seen from TEM images. Injection molded nanocomposite samples show significant decreases in elastomer particle size and increases in elastomer aspect ratio and particle density compared to as-extruded or pelletized samples. The elastomer particle size decreased significantly with increased MMT content and the molecular weight of PP. Low molecular weight PP based nanocomposite showed a greater reduction in elastomer particle size compared to medium and high molecular weight PP based nanocomposites. Elastomers having MFI in the range of 0.5-1.0 gave minimum elastomer particle sizes in the PP/PP-g-MA/MMT/EOR nanocomposite. The elastomer particles were deformed during injection molding leading to an increase in their aspect ratio. The nanocomposites containing high octene content elastomer gave smaller elastomer particle size and higher elastomer aspect ratios compared to nanocomposites containing low octene content elastomer.     

Exfoliation targeted toughness enhancement in polypropylene‐blend‐ montmorillonite nanocomposites

BACKGROUND: Both exfoliated and toughened polypropylene‐blend‐montmorillonite (PP/MMT) nanocomposites were prepared by melt extrusion in a twin‐screw extruder. Special attention was paid to the enhancement of clay exfoliation and toughness properties of PP by the introduction of a rubber in the form of compatibilizer toughener: ethylene propylene diene‐based rubber grafted with maleic anhydride (EPDM‐g‐MA). RESULTS: The resultant nanocomposites were characterized using X‐ray diffraction, atomic force microscopy, scanning electron microscopy, thermogravimetric analysis, dynamic mechanical analysis and Izod impact testing methods. It was found that the desired exfoliated nanocomposite structure could be achieved for all compatibilizer to organoclay ratios as well as clay loadings. Moreover, a mechanism involving a decreased size of rubber domains surrounded with nanolayers as well as exfoliation of the nanolayers in the PP matrix was found to be responsible for a dramatic increase in impact resistance of the nanocomposites. CONCLUSION: Improved thermal and dynamic mechanical properties of the resultant nanocomposites promise to open the way for highly toughened super PPs via nanocomposite assemblies even with very low degrees of loading. Copyright © 2008 Society of Chemical Industry     

Property enhancement in polypropylene ternary blend nanocomposites via a novel poly(ethylene oxide)‐grafted polystyrene‐block‐poly(ethylene/butylene)‐block‐polystyrene toughener–compatibilizer system

Synthesis and characterization of a novel toughener–compatibilizer for polypropylene (PP)–montmorillonite (MMT) nanocomposites were conducted to provide enhanced mechanical and thermal properties. Poly(ethylene oxide) (PEO) blocks were synthetically grafted onto maleic anhydride‐grafted polystyrene‐block‐poly(ethylene/butylene)‐block‐polystyrene (SEBS‐g‐MA). Special attention was paid to emphasize the effect of PEO‐grafted SEBS (SEBS‐g‐PEO) against SEBS‐g‐MA on morphology, static/dynamic mechanical properties and surface hydrophilicity of the resultant blends and nanocomposites. It was found that the silicate layers of neat MMT are well separated by PEO chains chemically bonded to nonpolar SEBS polymer without needing any organophilic modification of the clay as confirmed by X‐ray diffraction and transmission electron microscopy analyses. From scanning electron microscopy analyses, elastomeric domains interacting with MMT layers via PEO sites were found to be distributed in the PP matrix with higher number and smaller sizes than the corresponding blend. As a benefit of PEO grafting, SEBS‐g‐PEO‐containing nanocomposite exhibited not only higher toughness/impact strength but also increased creep recovery, as compared to corresponding SEBS‐g‐MA‐containing nanocomposite and neat PP. The damping parameter of the same nanocomposite was also found to be high in a broad range of temperatures as another advantage of the SEBS‐g‐PEO toughener–compatibilizer. The water contact angles of the blends and nanocomposites were found to be lower than that of neat hydrophobic PP which is desirable for finishing processes such as dyeing and coating. © 2018 Society of Chemical Industry     

SBS/蒙脱土复合材料的制备及其性能Ⅱ.复合材料的性能

分别采用大分子溶液插层法和大分子熔融插层法制备了苯乙烯-丁二烯-苯乙烯共聚物（SBS）／蒙脱土纳米复合材料．研究了材料的力学性能。纳米结构的形成对复合材料的性能产生显著影响,少量蒙脱士的引入可以明显改善SBS／蒙脱土复合材料的力学性能。无论溶液插层法制备的星型SBS／蒙脱土纳米复合材料,还是熔融插层法制备的线型SBS／蒙脱土纳米复合材料,其拉伸强度和断裂伸长率都同时增加。其中,溶液插层法制备的纳米复合材料的拉伸强度和断裂伸长率分别较纯SBS增加了75％和55％;熔融法制备的纳米复合材料的托伸强度和断裂伸长率分别较纯SBS增加了70％和18％。     

Effect of polymer matrix/montmorillonite compatibility on morphology and melt rheology of polypropylene nanocomposites

In this study, Ca²⁺‐montmorillonite (Ca²⁺‐MMT) and organo‐montmorillonite (OMMT) were modified by three compatibilizers with different degrees of polarity [poly(ethylene glycol) (PEG), alkyl‐PEG, and polypropylene (PP)‐g‐PEG]. PP/MMT nanocomposites were prepared by melt blending and characterized using X‐ray diffraction and transmission electron microscopy. The results showed the degree of dispersion of OMMT in the PP/PP‐g‐PEG/OMMT (PMOM) nanocomposite was considerably higher than those in the PP/PEG/OMMT and PP/alkyl‐PEG/OMMT nanocomposites, which indicated that the dispersion was relative to the compatibility between modified OMMT and PP matrix. Linear viscoelasticity of PP/MMT nanocomposites in melt states was investigated by small amplitude dynamic rheology measurements. With the addition of the modified MMT, the shear viscosities and storage modulus of all the PP/MMT nanocomposites decreased. It can be attributed to the plasticization effect of PEG segments in the three modifiers. This rheological behavior was different from most surfactant modified MMT nanocomposites which typically showed an increase in dynamic modulus and viscosity relative to the polymer matrix. The unusual rheological observations were explained in terms of the compatibility between the polymer matrix and MMT. In addition, the mechanical properties of PP/MMT nanocomposites were improved. A simultaneous increase in the tensile strength and toughness was observed in PP/PMOM nanocomposites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Enhancing antibacterial properties of polypropylene/Cu‐loaded montmorillonite nanocomposite filaments through sheath–core morphology

Polypropylene (PP) loaded with copper‐exchanged montmorillonite (Cu‐MMT) nanocomposite filaments and films with excellent antimicrobial activity have been reported for the first time. A sheath–core morphology filament in which only the sheath contains Cu‐MMT was prepared for maximizing bioactivity. Sodium MMT clay was modified to acid‐activated MMT and further to Cu‐MMT via an ion exchange process. The exchange operation was confirmed using wide‐angle X‐ray diffraction and energy‐dispersive X‐ray spectroscopy (EDX) which suggested increased interlayer spacing and confirmed the loading of copper in Cu‐MMT. Further, Cu‐MMT was melt‐mixed in PP in the form of PP/Cu‐MMT nanocomposite filament, film and sheath–core morphology PP/Cu‐MMT nanocomposite filament. The surface morphology and elemental composition of the nanocomposites were studied using scanning electron microscopy coupled with EDX. Transmission electron micrographs were obtained to understand the dispersion characteristics of Cu‐MMT phase in PP. X‐ray diffraction analysis of nanocomposites suggested increased crystallinity at lower loading due to heterogeneous nucleating action of MMT. The PP nanocomposite filaments and films were tested for antimicrobial activity against Gram‐negative bacterium Escherichia coli, which is the main pathogenic bacterium found abundantly in water, and were found to exhibit excellent antimicrobial activity. © 2018 Society of Chemical Industry     

SBS/蒙脱土复合材料的制备及其性能Ⅰ.复合材料的结构

分别采用大分子溶液插层法和大分子熔融插层法制备了苯乙烯-丁二烯-苯乙烯共聚物(SBS),蒙脱土纳米复合材料,采用X射线衍射和透射电子显微镜对材料的结构进行了表征。结果表明,无论是采用大分子溶液插层法还是大分子熔融插层法,都能得到SBS／蒙脱土纳米复合材料。对于溶液插层法,蒙脱土插层剂的种类、SBS牌号对插层效果都有影响：对于熔融插层法,SBS牌号对是否形成插层型纳米复合材料影响最大,淬火对熔融挤出后得到的纳米复合材料无益。星形结构的SBS适宜于采用溶液插层法、线形结构的SBS适宜于采用熔融插层法制备纳米复合材料。     

聚合物／蒙脱土纳米复合材料研究进展

介绍和分析了目前聚合物／蒙脱土纳米复合材料研究的热点。包括有关带有极性基团的插层剂、反应性插层剂和带有POSS基团的插层剂的研究,以及有无相容剂存在下熔融插层制备纳米复合材料方面的研究。讨论了插层剂和相容剂的作用及其机理,并展望了本领域的发展方向。     

Investigation of the influence of processing conditions on the thermal,rheological and mechanical behavior of polypropylene nanocomposites

The use of polypropylene (PP)‐layered silicate nanocomposite has attracted great interest in the polymer industry over the last years. On one hand, PP is widely used in many fields of applications because of good performance and cost. On the other hand, the major advantage of layered silicate nanofiller in the polymer matrix is the small amount of filler (<5 wt%) needed to enhance various properties such as Young's modulus. The most commonly used layered silicates are organomodified montmorillonite (MMT). In this study, a PP/organoclay nanocomposite, filled with layered silicate Nanofil SE3010 (1 and 5 wt%), provided by Rockwood Additives, USA, was used. The polymer nanocomposites were prepared via melt intercalation in a laboratory kneader. The compatibilizer (PP grafted with maleic acid anhydride) admixture content relative to the organoclay content (1 and 5 wt%) was chosen at a ratio of 1:1 (clay:compatibilizer). The influence of different processing conditions (rotation speed and residence time) on the thermal, rheological, and mechanical properties and the interlayer distance was investigated. It was the target to determine whether a short and intensive or a long and soft process performs better. Different properties prefer different states of dispersion of MMT in the polymer matrix. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Combination of double‐modified clay and polypropylene‐graft‐maleic anhydride for the simultaneously improved thermal and mechanical properties of polypropylene

Double‐modified montmorillonite (MMT) was first prepared by covalent modification of MMT with 3‐aminopropyltriethoxysilane and then intercalation modification by tributyl tetradecyl phosphonium ions. The obtained double‐modified MMT was melt compounded with polypropylene (PP) to obtain nanocomposites. The dispersion of the double‐modified MMT in PP was found to be greatly improved by the addition of PP‐graft‐maleic anhydride (PP‐g‐MA) as a “compatibilizer,” whose anhydride groups can react with the amino groups on the surface of the double‐modified MMT platelets and thus improve the dispersion of MMT in PP. Fourier transform infrared, X‐ray diffraction, transmission electron microscopy, thermogravimetric analysis, scanning electron microscopy, and tensile test were used to characterize the structure of the double‐modified MMT, morphology, and the thermal and mechanical properties of the nanocomposites. The results show that PP‐g‐MA promotes the formation of exfoliated/intercalated morphology and obviously increases the thermal properties, tensile strength, and Young's modulus of the PP/double‐modified MMT nanocomposites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Properties of polypropylene/layered-silicate nanocomposites and melt-spun fibers

Polypropylene (PP)/layered-silicate organoclay nanocomposites and their fibers were prepared by melt compounding and melt spinning, respectively, in the presence or absence of compatibilizer (PP-based maleic anhydride compatibilizer) to examine the effects of the organoclay dispersion and rheological behavior on the internal structure and tensile properties of the nanocomposite fibers. The compatibilized nanocomposites showed solidlike plateau behavior and strain hardening due to a three-dimensional network structure in the shear and uniaxial elongational flows. The tensile properties of the nanocomposite fibers were reduced compared with those of the pure PP fibers because some of the layered silicates were present as partially aggregated forms and the molecular weight of the compatibilizer was lower than that of the pure PP matrix. It was also found that the tenacity of the nanocomposite fiber increased and then decreased as the compatibilizer content increased because the compatibilizer affected the internal structure of the nanocomposite fibers. The positive effect of the compatibilizer was to generate a more effective exfoliated structure of organoclay in the polymer matrix. The negative effect was that the melt-spun nanocomposite fiber had a lower molecular weight than the pure PP fiber because the compatibilizer had a lower molecular weight. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Comparison of polylactide/nano-sized calcium carbonate and polylactide/montmorillonite composites: Reinforcing effects and toughening mechanisms

Semicrystalline polylactide (PLA) exhibits high tensile strength and modulus but very low strain-at-break and toughness. In this study, PLA nanocomposites with nano-sized precipitated calcium carbonate (NPCC) and organically modified montmorillonite (MMT) clay were prepared by melt extrusion. Morphologies, tensile mechanical properties, dynamic mechanical and rheological properties, polymer–nanoparticle interactions, and toughening mechanisms of the PLA/NPCC and PLA/MMT nanocomposites were compared. MMT and NPCC showed significantly different effects on the strength, modulus and elongation of the PLA nanocomposites. Different toughening mechanisms were first elucidated for the two types of nanocomposites based on the evidence from both macroscopic and microscopic observations. Under uniaxial tension, large quantities of microvoids were created in both PLA nanocomposites. The microvoids in PLA/NPCC caused massive crazing, while in PLA/MMT they resulted in shear yielding, particularly in the nanocomposite with 2.5 wt% MMT. The MMT stacks and platelets were found to be located between the microvoids in the extended specimens and prevented them from collapsing and coalescing.     

Polypropylene-elastomer (TPO) nanocomposites: 2. Room temperature Izod impact strength and tensile properties

Room temperature Izod impact strength was determined for polypropylene (PP)/ethylene-co-octene elastomer (EOR) blends and nanocomposites, containing organoclays based on montmorillonite (MMT), at fixed elastomer content of 30 wt% and 0-7 wt% MMT. A ratio of maleated polypropylene, PP-g-MA to organoclay of unity was used as a compatibilizer in the nanocomposites. The organoclay serves to reduce the size of the EOR dispersed phase particles and facilitates toughening. The Izod impact strength is also influenced by the molecular weight of PP, elastomer octene content, elastomer MFI in addition to MMT content. Nanocomposites based on a low molecular weight polypropylene (L-PP) containing a higher octene content elastomer showed higher impact strength at lower MMT contents compared to those based on a low octene content elastomer. The effect of elastomer octene content on impact strength of high molecular weight polypropylene (H-PP) nanocomposites is not so significant. Elastomers having a melt flow index (MFI) in the range of 0.5-1.0 showed significant improvement in the impact strength of L-PP based nanocomposites. Most H-PP/EOR blends gave ‘super-tough’ materials without MMT and maintain this toughness in the presence of MMT. The critical elastomer particle size below which the toughness is observed is reduced by decreasing the octene content of the elastomer. For the similar elastomer particle sizes in nanocomposites, the impact strength varies as H-PP > M-PP > L-PP. The tensile modulus and yield strength improved with increasing MMT content; however, elongation at break was reduced. The extruder-made TPO showed a good-balance of properties in the presence of MMT compared to reactor-made TPO having similar modulus and elastomer content.     

聚丙烯／蒙脱土纳米复合材料的制备与性能

用烷基季铵盐对钠基蒙脱土进行有机化处理,使其成为有机蒙脱土。X射线衍射（XRD）表明有机阳离子已同钠离子发生离子交换作用,导致层间距扩大。用熔融插层法制备聚丙烯／蒙脱土纳米复合材料,测试了力学性能。通过XRD、DSC等手段研究了其结构与结晶行为,并与聚丙烯进行了对比。实验表明,通过熔融插层可使聚丙烯插层于蒙脱土片层之中,且所得聚合物的冲击强度有所提高。     

SEP和蒙脱土复合增强PP／PS合金的研究

观察了聚丙烯(PP)/聚苯乙烯(PS)／(苯乙烯-乙烯/丙烯二嵌段共聚物)(SEP)合金的形态，测定了SEP、SEP/改性蒙脱土复合材料对PP／PS合金的力学性能的影响。结果表明：SEP在EPP／PS合金中作为增容剂，减小了分散相的平均粒子尺寸，大大改变了合金的形态，增强了两相间的粘合力，提高了合金的力学性能，并对PP/PS(20／80)合金的增容作用较为显著。结果还表明：SEP／改性蒙脱土复合材料对PP／PS(20／80)合金具有增韧增强的效果。     

Specific Fibre Formation in Flow of Melts of Polypropylene/Copolyamide Blends in the Phase Change Region

The rheological features and crosslinking processes in melts of PP/CPA [polypropylene/copolyamide] blends containing PEG [polyethylene glycol] or EVAC [ethylene-vinyl acetate copolymer]/PEG binary additive as compatibilizers were investigated. The possibility of realization of specific fibre formation was established for PP/CPA blends in the phase change region on addition of PEG as a compatibilizer. The study of decomposition of PP microfibres in compatibilized blends demonstrated a stabilizing effect on liquid jets of PP in a CPA matrix. __________ Translated from Khimicheskie Volokna, No. 4, pp. 23–26, July–August, 2005.     

Effect of montmorillonoite modification and maleic anhydride‐grafted polypropylene on the microstructure and mechanical properties of polypropylene/montmorillonoite nanocomposites

Two types of modified montmorillonite (MMT) were achieved using octadecylamine as the modifying agent by the methods of dry process and wet route. Polypropylene (PP)/MMT nanocomposites were prepared using the melt mixing technique and employing maleic anhydride‐grafted polypropylene (PP‐MA) as the compatibilizer. The modification of montmorillonite was characterized by fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), and scanning electron microscope (SEM). The effect of MMT modification and PP‐MA on the microstructure and properties of PP/MMT nanocomposites was investigated by SEM, differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and polarizing microscopy. The results show that organic montmorillonite modified by wet process (WOMMT) has a large d‐spacing increment; whereas montmorillonite modified by dry process (DOMMT) shows little d‐spacing increment. Furthermore, the mechanical properties of composites incorporating WOMMT are better than that containing DOMMT. As a third component, the addition of PP‐MA benefits the formation of exfoliated structure and the dispersion of MMT in PP matrix, and hence, enhances the physical properties of the nanocomposite. With the presence of PP‐MA, the highly dispersed MMT increases the number of spherulite crystals, enhances the melting enthalpy, improves the thermal stability, and induces the desired tiny crazes more effectively. MMT increases the storage modulus (E′) and glass‐transition temperature (T_g) of PP because of the stiffness of MMT layers, but PP‐MA decreases them owing to its high melt flow index, both of which were in favor of improving the physical properties. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3952–3960, 2013     

Preparation of extruded melt‐mixed polypropylene/montmorillonite nanocomposites with inline monitoring

This article advances the use of an inline optical detector to monitor the disaggregation of the montmorillonite (MMT) clay tactoids during the preparation of polypropylene (PP)/MMT nanocomposites via polymer melt compounding. During the exfoliation of the tactoids their size are reduced below the minimum particle size to produce light extinction and so, the signal of the inline detector reduces as the nanosize composite is formed. The measurement is done at the transient state with the MMT clay added as a pulse with constant weight into the PP extrusion melt flow and followed by the optical detector. The data comes out as the common residence time distribution curves having its maximum intensity related to the tactoids average particle size, keeping all other variables constants. The light extinction was measured for composites with different clays (Cloisite® 15A, 30B, Na⁺, and Sintered 20A) using the same PP grafted with maleic anhydride compatibilizer. The dissaglomeration/exfoliation efficiency increases as: ‘‘Sintered 20A’’ < ‘‘Na+ clay’’ < ‘‘organo‐modified clay’’ < ‘‘organo‐modified clay + compatibilizer’’. The best result is obtained using Cloisite® 15A and Cloisite® 20A following the expected reduction of the particle size obtained during a nanocomposite melt processing. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers