Dynamic mechanical properties and morphology of polypropylene/maleated polypropylene blends

The dynamic mechanical properties of both homopolypropylene (PPVC)/Maleated Poly-propylene (PP-g-MA) and ethylene-propylene block copolymer (PPSC)/Maleated Poly-propylene (PP-g-MA) blends have been studied by using a dynamic mechanical thermal analyzer (PL-DMTA MKII) over a wide temperature range, covering a frequency zone from 0.3 to 30 Hz. With increasing content of PP-g-MA, α relaxation of both blends gradually shift to a lower temperature and the apparent activation energy ΔE_α increases. In PPVC/PP-g-MA blends, β relaxation shifts to a higher temperature as the content of PP-g-MA increases from 0 to 20 wt % and then change unobviously for further varying content of PP-g-MA from 20 to 35 wt %. On the contrary, in the PPSC/PP-g-MA blends β₁ relaxation, the apparent activation energy ΔE_β1 and β₂ relaxation are almost unchanged with blend composition, while ΔE_β2 increases with an increase of PP-g-MA content. In the composition range studied, storage modulus É value for PPSC/PP-g-MA blends decreases progressively between β₂ and α relaxation with increasing temperature, but in the region the increment for PPVC/PP-g-MA blends is independent of temperature. The flexural properties of PPVC/PP-g-MA blend show more obvious improvement on PP than one of PPSC/PP-g-MA blends. Scanning electron micrographs of fracture surfaces of the blends clearly demonstrate two-phase morphology, viz. the discrete particles homogeneously disperse in the continous phase, the main difference in the morphology between both blends is that the interaction between the particles and the continuous phase is stronger for for PPVC/PP-g-MA than for PPSC/PP-g-MA blend. By the correlation of the morphology with dynamic and mechanical properties of the blends, the variation of the relaxation behavior and mechanical properties with the componenet structure, blend composition, vibration frequency, and as well as the features observed in these variation are reasonably interpreted. © 1996 John Wiley & Sons, Inc.     

Rheologically determined phase behavior and miscibility of reactively compatibilized poly(ethylene terephthalate)/polypropylene blends

Rheology, phase behavior and morphology of poly(ethylene terephthalate)/polypropylene (PET/PP) blends compatibilized with maleic-anhydrate-grafted-PP (PP-g-MA) and n-butyl-acrylate-glycidyl-methacrylate-ethylene (EBGMA) were studied. According to infrared spectroscopy results, whereas PP-g-MA was merely capable of reacting with hydroxyl groups of PET, epoxy groups of EBGMA could react with both the hydroxyl and carboxyl end groups of PET. The enhanced compatibilizing effect of EBGMA on PET/PP systems over PP-g-MA was also revealed by scanning electron microscopy and mechanical experiments. From frequency and temperature sweep rheological experiments, the dynamic characteristics of the compatibilized blends found to be improved in comparison with those of the uncompatibilized system. Such enhancement was interpreted as a result of the higher miscibility of the compatibilized blends which was further supported by Cole–Cole plot analyses.     

Compatibilization effectiveness of maleated polypropylene compared to organoclay in PBT/PP blends

The compatibilization efficiency of a conventional compatibilizer (PP-grafted maleic anhydride) is compared with an organoclay of hydrophilic modifier (Cloisite 30B) in poly(butylene terephthalate)/polypropylene (PBT/PP) immiscible polymer blend. Moreover, the effect of PP-grafted maleic anhydride (PP-g-MA) on localization of Cloisite 30B organoclays is investigated, in this research. Accordingly, PBT/PP blends containing PP-g-MA, organoclay and PP-g-MA/organoclay are prepared by melt mixing method. According to morphological analysis, organoclays are more efficient than PP-g-MA in dispersion and distribution of droplets in PBT/PP blend. Additionally, the size of dispersed-droplets in PBT/PP/organoclay nanocomposite is lower than PBT/PP/PP-g-MA/organoclay sample. From X-ray diffractometry (XRD) and transmission electron microscopy illustrations, it is shown that organoclays represent the higher level of intercalation structure in PBT/PP/organoclay compared to PBT/PP/PP-g-MA/organoclay nanocomposite. PBT/PP/Organoclay nanocomposite indicates higher viscosity and elasticity in comparison with PBT/PP/PP-g-MA/organoclay, as well. The present subject can be explained by the role of PP-g-MA in transferring some parts of organoclays from PBT matrix into PP droplets which hinders the break-up of dispersed-droplets. According to non-linear viscoelastic properties, PBT/PP/organoclay sample shows stronger stress overshoots than PBT/PP/PP-g-MA/organoclay in start-up of shear flow. Modified De Kee-Turcotte model is studied to investigate the yield stress and viscoelastic behavior of different samples. PBT/PP/Organoclay nanocomposite shows higher yield stress compared to PBT/PP blend filled by PP-g-MA/organoclay system.     

The Effect of Spray-Freeze Drying of Montmorillonite on the Morphology,Dispersion, and Crystallization in Polypropylene Nanocomposites

The spray-freeze drying (SFD) technique was applied to sonicated aqueous suspensions of spray-dried montmorillonite clay (MMT) to produce highly porous agglomerates (SFD-MMT). Both MMT (used as a reference) and SFD-MMT were subsequently incorporated in polypropylene (PP) via melt compounding to produce 2 wt % nanocomposites with and without maleic anhydride grafted polypropylene (PP-g-MA). Polypropylene nanocomposites containing SFD-MMT exhibited thinner silicate flake layers compared to large agglomerates in PP/MMT nanocomposites. SFD-MMT particles became even more finer in the presence of PP-g-MA (i.e., in PP/PP-g-MA /SFD-MMT) where it hindered PP crystallization instead of serving as nucleation sites for the PP crystallization during rapid cooling. SFD-MMT improved the thermal stability of PP/PP-g-MA by 30°C compared to only 5–8°C for MMT/nanocomposites. MMT acts as a heterogeneous nucleating agent in the nucleation-controlled PP nanocomposites, but the hindrance effect was observed for the PP/PP-g-MA with SFD-MMT. PP/PP-g-MA/SFD-MMT exhibited twice the edge surface energy as compared to PP/PP-g-MA/MMT. The incorporation of both types of MMT raised the tensile moduli of PP and PP/PP-g-MA, with no improvement in their tensile strength and a decrease in the elongation at break. The PP/PP-g-MA/SFD-MMT showed brittle failure. POLYM. ENG. SCI., 60:168–179, 2020. © 2019 Society of Plastics Engineers     

Morphology and properties of polypropylene nanocomposites based on a silanized organoclay

A silanized organoclay (s-M₂(HT)₂) was prepared by reaction of trimethoxyphenyl silane with an organoclay with a M₂(HT)₂ surfactant structure. Nanocomposites were formed from polypropylene (PP) and a blend of PP and maleic anhydride-grafted polypropylene (PP-g-MA) and the M₂(HT)₂ and s-M₂(HT)₂ organoclays by melt processing to explore the extent of exfoliation and the mechanical properties. Wide angle X-ray scattering (WAXS) and transmission electron microscopy (TEM) coupled with detailed particle analysis were used to determine the effect of the organoclay used and the PP-g-MA compatibilizer on exfoliation and mechanical, rheological, and thermal expansion properties. The PP/s-M₂(HT)₂ nanocomposites have higher particle densities than the PP/M₂(HT)₂ nanocomposites though the aspect ratio remains the same. Platelet dispersion is significantly improved by using PP-g-MA compatibilizer for both organoclays. The rheological properties and the relative modulus improve for the PP/s-M₂(HT)₂ nanocomposites but not to the same degree as either organoclay in a PP-g-MA compatibilized matrix. The thermal expansion properties, however, are not improved by using the s-M₂(HT)₂ organoclay. The s-M₂(HT)₂ organoclay is less prone to agglomeration during extrusion than the M₂(HT)₂ organoclay.     

Structure and properties of polypropylene-based nanocomposites: Effect of PP-g-MA to organoclay ratio

The structure-property relationships of polypropylene (PP)-based nanocomposites prepared by melt processing have been investigated with a main focus on the ratio of polypropylene grafted with maleic anhydride (PP-g-MA) to organoclay. The morphological observations by transmission electron microscopy and X-ray diffraction are presented in conjunction with the mechanical, rheological and thermal expansion properties of these nanocomposites. Detailed morphological studies and subsequent quantitative particle analyses for the dispersed clay phase reveal that the aspect ratio of clay particles decreases as the amount of clay increases, and it increases as the amount of PP-g-MA increases. The rheological properties suggest that the extent of a percolation network can be enhanced by increasing the number of organoclay particles at a fixed ratio of PP-g-MA to organoclay and by increasing the degree of exfoliation at fixed clay content. However, mechanical and thermal expansion behaviors do not improve correspondingly in all cases because of the reduction of matrix properties by PP-g-MA. The reduction of the modulus and the increase in the expansion of the polymer matrix caused by the presence of PP-g-MA are compared to the prediction of the Chow model. Clearly, the amount of PP-g-MA added along with its lower crystallinity are important factors affecting the mechanical and thermal expansion properties of PP-based nanocomposites.     

Dispersion of nanoclay into polypropylene with carbon dioxide in the presence of maleated polypropylene

The effect of maleic anhydride grafted polypropylene (PP-g-MA) on the mechanical and rheological properties of polypropylene (PP)–clay nanocomposites prepared with nanoclay expanded with CO₂ and direct melt blending was studied. The results from the studies of the mechanical properties, rheological properties, and transmission electron microscopy show that when PP-g-MA was combined with the technique that used CO₂, greater enhancements in the mechanical properties and degree of dispersion of nanoclay in PP were observed. Furthermore, yieldlike behavior in the viscosity and a tail in the low-frequency behavior of the elastic modulus was attributed to the reaction of PP-g-MA with the nanoclay surface and not exfoliation. A fairly well-dispersed morphology was observed for concentrations as high 6.8 wt % clay when the clay was expanded and mixed with CO₂. At this concentration, mechanical properties such as yield strength and modulus increased by as much as 13 and 69%, respectively, relative to the pure PP. Furthermore, the modulus of the composite samples prepared with PP-g-MA and CO₂ was some 15% higher than that of samples prepared by direct melt compounding (without the use of CO₂). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of compatibilizer concentration on dynamic rheological behavior and morphology of thermoplastic starch/polypropylene blends

The reactive compatibilization of blends consisting polypropylene (PP) and thermoplastic starch (TPS) (70/30) with different portions of PP-grafted maleic anhydride (PP-g-MA) is carried out by melt mixing. The esterification reaction between the starch hydroxyl and the PP-g-MA groups proved by the FTIR leads to a compatibility improvement. The dynamic rheological properties, morphology, elongation at break, and the impact strength of the blends were studied. The SEM images show that increasing the compatibilizer concentration reduces the dispersed TPS droplet size. The generalized Zener model states that an elastic interface is established (minimum α value) and enables us to predict the dynamic rheological properties of our blends in a longer frequency range to where the current experimental limitation exists. The modified Cross model is implemented to confirm better adhesion between phases when 20 wt % PP-g-MA is used (minimum a_c value). The increase in the dynamic viscoelastic moduli at concentrations up to 20 wt % and the observed plateau at the elongation at break point at this concentration confirmed that this concentration is the optimum for the maximum stress transfer. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48742.     

Novel strategy for ternary polymer blend compatibilization

A novel strategy for compatibilization of ternary polymer blends was described. PP (polyolefins)/PA6 (engineering plastics)/PS (styrene polymers) was selected as a model ternary blend system, and the compatibilization effect was investigated by means of SEM, rheometer, dynamic mechanical thermal analysis and mechanical testing. The results indicated that, as a ternary polymer blend compatibilizer, styrene and maleic anhydride dual monomers melt grafted polypropylene [PP-g-(MAH-co-St)] showed more effective compatibilization in the PP/PA6/PS ternary blend system than PP-g-MAH, PP-g-St and their mixture. The good compatibilizing effect of PP-g-(MAH-co-St) can be explained by two mechanisms. One is the in situ formation of [PP-g-(MAH-co-St)]-g-PA6 copolymer at the PP/PA6 interface, and the other is that it also contains styrene blocks, resulting in chemical affinity with PS and PP homopolymers.     

Compatibility,morphology, and crystallization behavior of compatibilized β-nucleated polypropylene/poly(trimethylene terephthalate) blends

β-Nucleated polypropylene (PP), uncompatibilized β-nucleated PP/poly(trimethylene terephthalate) (PTT), β-nucleated PP/PTT blends compatibilized with maleic anhydride (MA)-grafted PP (PP-g-MA), and styrene–ethylene–propylene copolymer were prepared with a twin-screw extruder. The morphology, compatibility, crystallization characteristic, melting behavior, and crystallization kinetics were investigated. The result shows that β-nucleated PP was incompatible with PTT, and the addition of the two compatibilizers decreased the interfacial tension between β-nucleated PP and PTT; this led to improved dispersion and strengthened interfacial bonding in the blends. PP-g-MA had a better compatibilization effect. All of the researched β-nucleated PP/PTT blends contained β crystals of PP, and the compatibilizers exhibited synergistic effects with the β-nucleating agent to further increase the content of β crystals. Nonisothermal kinetic analysis indicated that Mo's method described the nonisothermal crystallization behavior of the β-nucleated PP/PTT blends satisfactorily, and the Avrami approach could only describe the early stage of the crystallization appropriately, whereas the Ozawa method failed to have the same effect. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The Study of Reactively Compatibilized mPPO/PP Blend Systems

Polymer blends of commercial polyphenylene oxide (mPPO) and polypropylene (PP) are immiscible and incompatible in blend system. Maleic anhydride-grafted-copolymer has been employed as in situ compatibilizer for the mPPO and PP blends. This copolymer contains reactive anhydride functional groups that were able to react with mPPO at [sbnd]CH₃ side methyl groups [sbnd]OH terminal groups under the melt conditions. The PP-g-MA copolymer reduces the interfacial tension between the two polymers and act as a bridge between them to make compatible. The blends have been characterized using FTIR, SEM, and its mechanical behavior.     

The influence of filler treatment on the properties of TPU/PP blends: I. Thermal properties and stability

Commercially available organosilane (3‐glycidoxypropyltrimethoxysilane (GPTMS)) coupling agent was used to treat talc in order to improve the affinity relative between the filler and the polymer in composites as well as filler and polymer in the thermoplastic polyurethane/polypropylene (TPU/PP) blends (talc content was 5 wt%). The talc particles were first modified with GPTMS and then introduced into TPU, PP as well as TPU/PP blends with different weight ratios of polymers using blending method and subsequently injection molded in a hydraulic press. The aim was to report the effect of silane coupling agent on the thermal and morphological properties of talc filled composites and blends. The results showed that the thermal properties of the TPU, PP composites and TPU/PP blends were improved with the addition of silane treated talc (higher melting (T_m), crystallization (T_c) temperatures and degree of crystallinity (χ_c)). The glass transition temperature (T_g) obtained by dynamic mechanical analysis (DMA) of the TPU soft segments in TPU/PP blends increased with the addition of untreated and silane treated talc due to lower mobility of the soft segments in TPU and better miscibility of TPU and PP. TPU/PP blends with the silane treated talc show better thermal stability than the TPU/PP blends with untreated talc. POLYM. ENG. SCI., 55:1920–1930, 2015. © 2014 Society of Plastics Engineers     

Study on compatibilization of polypropylene-liquid crystalline polymer blends

The mechanical properties, melt rheology, and morphology of binary blends comprised of two polypropylene (PP) grades and two liquid crystalline polymers (LCP) have been studied. Compatibilization with polypropylene grafted with maleic anhydride (PP-g-MAH) has been attempted. A moderate increase in the tensile moduli and no enhancements in tensile strength have been revealed. Those findings have been attributed to the morphology of the blends, which is predominantly of the disperse mode. LCP fibers responsible for mechanical reinforcement were only exceptionally evidenced. Discussion of PP-LCP interfacial characteristics with respect to mechanical properties-morphology interrelations allowed evaluation of the compatibilizing efficiency of PP-g-MAH. Factors important for successful reinforcement of PP with LCP have been specified. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 969–980, 1997     

Effect of the ratio of maleated polypropylene to organoclay on the structure and properties of TPO-based nanocomposites. Part I: Morphology and mechanical properties

The structure-property relationships of thermoplastic olefin (TPO)-based nanocomposites prepared by melt processing are reported with a main focus on the ratio of maleic anhydride-grafted polypropylene (PP-g-MA) to organoclay. The morphological observations by transmission electron microscopy, atomic force microscopy, and X-ray diffraction are presented in conjunction with the mechanical and rheological properties of these nanocomposites. Detailed quantitative analyses of the dispersed clay particles revealed that the aspect ratio of clay particles decreased as clay content increased but increased as the amount of PP-g-MA increased. Analysis of the elastomer phase revealed that the aspect ratio of the elastomer phase increased in both cases. The presence of clay causes the elastomer particles to become highly elongated in shape and retards the coalescence of the elastomer particles. The modulus and yield strength are enhanced by increasing the PP-g-MA/organoclay ratios. High levels of toughness of the TPO can be maintained when moderate levels of (organoclay) MMT and PP-g-MA are used. The rheological properties suggested that the addition of clay particles and PP-g-MA has a profound influence on the long time stress relaxation of the TPO nanocomposites. Based on these analyses, it is clear that it is important to optimize the ratio of PP-g-MA and organoclay to obtain the desired balance of mechanical properties and processing characteristics for TPO nanocomposites.     

Improvement of mechanical properties for PP/PS blends by in situ compatibilization

The effect of the in situ compatibilization on the mechanical properties of PP/PS blends was investigated. The application of Friedel-Crafts alkylation reaction to the PP/PS-blend compatibilization was assessed. Styrene/AlCl₃ was used as catalyst system. The graft copolymer (PP-g-PS) formed at the interphase showed relatively high emulsifying strength. Scission reactions, occurring in parallel with grafting, were verified for PP and PS at high catalyst concentration, but no crosslinking reactions were detected. Tensile tests were performed on dog-bone specimens of the blends. Both elongation at break and toughness increased with catalyst concentration. At 0.7% AlCl₃, a maximum was reached, which amounted to five times the value of the property for the uncompatibilized blend. At higher catalyst concentrations these properties decreased along with the PP molecular weight due to chain-scission reactions. On the other hand, the tensile strength did not change with the catalyst concentration. The in situ compatibilized blends showed considerable improvement in mechanical properties, but were adversely affected by chain scissions at high catalyst contents.     

Aniline-Modified Polypropylene as a Compatibilizer in Polypropylene Carbon Nanotube Composites

Maleic anhydride-grafted polypropylene (PP-g-MA) was reacted with aniline (NH₂C₆H₅) to produce PP-g-NHC₆H₅ and used as a compatibilizer in polypropylene/carbon nanotube composites. Infrared spectroscopy (FTIR) and nuclear magnetic resonance confirmed the reaction between PP-g-MA and aniline. PP-g-NHC₆H₅ resulted a better compatibilizer than PP-g-MA, producing good dispersion and homogeneous distribution of the carbon nanotubes with less agglomerates, as observed by SEM analysis. Improved dispersion and distribution is assumed to be due to the π–π interactions between the –C₆H₅ ring in the prepared compatibilizer and the hexagonal carbon structure in the nanotubes. In addition, a higher degree of crystallinity (12%) was promoted, since it was favored by π–π interactions. This achieved higher crystallinity promoted an increase in tensile modulus, with only slight changes in tensile strength but with an adverse effect on elongation at break.     

Polystyrene/Polyolefin Elastomer Blends Loaded with Halloysite Nanotubes: Morphological,Mechanical, and Gas Barrier Properties

Herein, a simple melt-blending method is utilized to disperse of halloysite nanotubes (HNTs) in polystyrene/polyolefin elastomer (PS/POE) blends. Based on morphological studies, the PS/POE/HNT nanocomposite containing up to 3 phr HNTs shows excellent nanofiller dispersion, while those filled with 5 phr HNTs exhibit nanofiller aggregation. To overcome the nanofiller aggregation issue, the polypropylene-grafted-maleic anhydride (PP-g-MA) compatibilizer is added to the PS/POE/HNT nanocomposite, which results in improved mechanical properties for the nanocomposite sheets. Furthermore, the addition of compatibilized HNTs to the PS/POE blends leads to decreased O₂ and N₂ gas permeabilities. Besides, incorporating POE, HNTs, and PP-g-MA leads to a decrease in water vapor transmission of PS. In the end, the experimentally-determined mechanical properties and gas permeabilities of the nanocomposite sheets are compared to those predicted by prevalent theoretical models, revealing a good agreement between the experimental and theoretical results. Molecular-dynamics simulations are also carried out to calculate the gas diffusion coefficients in the different sheets to further support the experimental findings in this study. Overall, the PS/POE/HNT/PP-g-MA nanocomposite sheets fabricated in this work demonstrate excellent mechanical and gas barrier properties; and hence, can be used as candidate packaging materials. However, the strength of the resulting PS/POE blend may be inferior to that of the virgin PS.     

Polypropylene-grafted nanoparticles as a promising strategy for boosting physical properties of polypropylene-based nanocomposites

SiO₂ nanoparticles grafted to terminally hydroxylated polypropylene (PP-g-SiO₂) with different molecular weights were melt mixed with PP to prepare a series of PP/PP-g-SiO₂ nanocomposites. PP/PP-g-SiO₂ offered several advantages over pristine PP and PP/unmodified SiO₂ such as highly uniform dispersion up to 10 wt.-%, +200–400% faster crystallization and +30% increments for both the Young's modulus and the tensile strength without largely sacrificing the melt viscosity of PP. We concluded that grafted chains act as crystallization nuclei and co-crystallize with matrix chains to make PP-g-SiO₂ nanoparticles as a physical cross-linker between lamellae, while the linkage disappears in melt and grafted chains minimize the cohesive attraction between nanoparticles.     

Role of organically modified layered silicate as an active interfacial modifier in immiscible polystyrene/polypropylene blends

The role of organically modified layered silicate as a compatibilizer for immiscible polystyrene (PS) with polypropylene (PP) or polypropylene grafted with maleic anhydride (PP-g-MA) blends was investigated. Scanning electron micrographs (SEM) revealed efficient mixing of the polymers in the presence of organically modified layered silicate. X-ray diffraction (XRD) patterns and transmission electron microscopic (TEM) observations showed that silicate layers were either intercalated or exfoliated, depending on their interactions with the polymer pair, and were located at the interface between the two polymers. The compatibilizing action of the organically modified layered silicate resulted in a decrease in interfacial tension and particle size and in a remarkable increase in mechanical properties of the modified immiscible blends.     

Morphology and mechanical properties of polypropylene‐POSS hybrid nanocomposites obtained by reactive blending

The polypropylene‐polyhedral oligomeric silsesquioxane (PP‐POSS) organic–inorganic hybrids were obtained and studied. The hybrids were prepared by grafting of POSS on PP chains during a reactive melt‐blending of polypropylene (iPP), maleic anhydride functionalized PP (PP‐g‐MA), and amine‐functionalized POSS (aminopropylheptaisobutyl‐POSS, ambPOSS, aminopropylheptaisooctyl‐POSS, amoPOSS, or aminoethylaminopropylheptaisobutyl‐POSS, am2bPOSS), taking advantage of the high efficiency of amino‐anhydride reaction in the molten state. The structure, morphology, and physical properties of the obtained hybrids and blends were studied by means of wide‐ and small‐angle X‐ray scattering, dynamic scanning calorimetry, scanning electron microscopy, dynamic mechanical thermal analysis, as well as tensile and impact experiments. The influence of POSS chemical structure and grafting degree on the morphological characteristics and mechanical properties was investigated. It was found that grafting of POSS cages on PP chains leads to the POSS dispersion on the molecular level. On contrary, when POSS was mixed with plain iPP any grafting of POSS on iPP chains was impossible, which resulted in phase‐separated blend with crystallites of POSS dispersed in iPP matrix. The mechanical tests revealed that modification of polypropylene by grafting with POSS molecules does not affect significantly its mechanical properties, both static and dynamic, except ultimate strain, which is markedly lower in hybrids and their blends than in plain iPP. Also the impact properties of PP were practically not improved by modification with POSS. POLYM. COMPOS., 34:929–941, 2013. © 2013 Society of Plastics Engineers