Structural,thermal, and gas transport properties of HDPE/LLDPE blend‐based nanocomposites using a mixture of HDPE‐g‐MA and LLDPE‐g‐MA as compatibilizer

Nanocomposites based on high density polyethylene (HDPE)/linear low density polyethylene (LLDPE) blend were prepared by melt compounding in a twin‐screw extruder using organoclay (montmorillonite) as nano‐filler and a 50/50 wt% mixture of maleic anhydride functionalized high density polyethylene (HDPE‐g‐MA) and linear low density polyethylene (LLDPE‐g‐MA) as the compatibilizing system. The addition of a maleated polyethylene‐based compatibilizing system was required to improve the organoclay dispersion in the HDPE/LLDPE blend‐based nanocomposite. In this work, the relationships between thermal properties, gas transport properties, and morphology were correlated. The compatibilized nanocomposite exhibited an intercalated morphology with a small number of individual platelets dispersed in the HDPE/LLDPE matrix, leading to an significant decrease in the oxygen permeation coefficient of the nanocomposites. A decrease in the carbon dioxide permeability and oxygen permeability with increase of nanoclay was observed for the compatibilized nanocomposites. The carbon dioxide permeability of the compatibilized nanocomposites was lower than the carbon dioxide permeability of the uncompatibilized nanocomposites even with the low intrinsic barrier properties of the compatibilizer. These effects were attributed to a good dispersion of the inorganic filler, good wettability of the filler by the polymer matrix, and strong interactions at the interface that increased the tortuous path for diffusion. Theoretical permeability models were used to estimate the final aspect ratio of nanoclay in the nanocomposite and showed good agreement with the aspect ratio obtained directly from TEM images. POLYM. ENG. SCI., 56:765–775, 2016. © 2016 Society of Plastics Engineers     

Use of purified and modified bentonites in linear low‐density polyethylene/organoclay/compatibilizer nanocomposites

Polyethylene‐based ternary nanocomposites were prepared with different clay structures, obtained by the modification of purified Resadiye bentonite as the reinforcement, a random terpolymer of ethylene, butyl acrylate, and maleic anhydride with the trade name Lotader3210 as the compatibilizer, and linear low‐density polyethylene (LLDPE) as the polymer matrix in an intensive batch mixer. The quaternary ammonium/phosphonium salts used for the modification of bentonite were dimethyldioctadecyl ammonium (DMDA) chloride (Cl), tetrakisdecyl ammonium (TKA) bromide (Br), and tributylhexadecyl phosphonium (TBHP) Br. The effects of the physical properties and structure of the organoclay on the clay dispersion were studied at different clay contents (2 and 5 wt %) and at a compatibilizer/organoclay ratio of 2.5. The extent of organoclay dispersion was determined by X‐ray diffraction (XRD) and was verified by transmission electron microscopy (TEM), mechanical testing, and rheological analysis. XRD analysis showed that the nanocomposite with the organoclay DMDA contained intercalated silicate layers, as also verified by TEM. The TEM analysis of the nanocomposites with TBHP exhibited intercalated/partially exfoliated clay dispersion. TKA, with a crowded alkyl environment, sheltered and hindered the intercalation of polymer chains through the silicate layers. In comparison to pure LLDPE, nanocomposites with a 33–41% higher Young's modulus, 16–9% higher tensile strength, and 75–144% higher elongation at break were produced with DMDA and TBHP, respectively (at 5 wt % organoclay). The storage modulus increased by 807–1393%, and the dynamic viscosity increased by 196–339% with respect to pure LLDPE at low frequencies for the samples with DMDA and TBHP (at 5 wt % organoclay). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of intercalating agents on clay dispersion and thermal properties in polyethylene/montmorillonite nanocomposites

Alkyl pyridinium, 1‐vinyl alkyl imidazolium, 1,3‐dialkyl imidazolium, and tetraalkyl phosphonium bromides were successfully used as intercalants for the preparation of highly thermally stable organophilic montmorillonites. Nanocomposites of linear low density polyethylene (LLDPE) and linear low density polyethylene grafted with maleic anhydride (LLDPE/LLDPE‐g‐MAH) were prepared from those organoclays. The micro‐ and nano‐dispersions were analyzed through X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM): intercalation and/or partial exfoliation were found to occur only for formulations based on organoclays having an initial basal distance higher than 20 Å, suggesting the existence of a critical interfoliar distance for the delamination of silicate layers in a noninteracting polymer matrix. The properties of the nanocomposites were analyzed through differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and oscillatory rheometry. The dynamic crystallization of LLDPE was not significantly affected by the presence of clay. TGA in oxidative atmosphere proved to be very sensitive to the dispersion state of the organoclay: the thermal stability was drastically enhanced for intercalated and partially exfoliated formulations. However, the inherent thermal stability of the organoclay did not appear to influence significantly the overall thermal stability of the composite in the range of temperatures investigated (160–230°C). POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.     

Organoclay localization in polyamide 6/ethylene-butene copolymer grafted maleic anhydride blends: the effect of different types of organoclay

Localization of organoclays between two phases of polyamide 6 (PA6)/maleic anhydride grafted ethylene-butene copolymer (EB-g-MAH) blends, prepared via melt mixing, was investigated as a function of organoclay type. Cloisite 30B, Cloisite 20A and Cloisite 15A were used as different types of organoclay. The influence of different blend compositions and clay contents were also studied. Contact angle measurements have been applied to determine surface tension of components and then to calculate the wetting coefficient which is a useful parameter for prediction of the organoclay location. In general, all organoclays were found to locate in the more hydrophilic polyamide 6 phase. However, for Cloisite 20A and Cloisite 15A transmission electron microscopy (TEM) observations revealed some organoclay layers in the EB-g-MAH phase. Phase structure and nanocomposite morphology were evaluated using scanning and transmission electron microscopy and small angle X-ray scattering (SAXS). Results indicated the formation of an exfoliated or an intercalated morphology in different samples. Dynamic-mechanical thermal analysis and thermal gravimetric analysis were used as an experimental probe to confirm the location of nanoclays predicted via wetting coefficient. The shifting of glass transition temperature for PA6 phase confirmed that nanoclays are more distributed in this phase.     

Effect of organoclay structure characteristics on properties of ternary PP‐EP/EVA/nanoclay blend systems

In this study, the effect on the degree of organoclay exfoliation in polypropylene‐ethylene (PP‐EP)/Ethylene vinyl acetate (EVA)/organoclay blend system was studied while varying organoclay structural characteristics. Cloisite 6A, Cloisite 15A, Cloisite 20A, Cloisite 25A, Cloisite 30B, Cloisite 93A, and Cloisite 10A were used because they have different type of modifier. Ternary PP‐EP/EVA/organoclay system was obtained with each type of clay and results were organized to analyze the effect of type of clay chemical modification (C20A, C15A, and C6A), steric effect caused by surfactant structure (C15A and C10A), length of substitute groups on the surfactant (C20 and C25A), and surfactant polarity (C30B and C93A). Samples were characterized by: wide angle X‐ray diffraction, scanning transmission electron microscopy (STEM), dynamic mechanical analysis, and capillary rheometry. Results showed that clay galleries can be saturated with chemical modifier complicating the polymer chain intercalation into the clay galleries. Some clay modifier substituent groups could cause certain steric effect promoting less exfoliated platelets structures. Finally, longer chains in the modifier substituent group can promote a better intercalated–exfoliated structure. Among all the studied organoclays, best results were obtained in the ternary system when using C20A, which modifier has two hydrogenated tallows. In this case, interlayer spacing was increased more noticeable after ternary system was formed. This was corroborated with the obtained increase in viscosity and the intercalated–exfoliated structure observed by STEM. POLYM. COMPOS., 35:2241–2250, 2014. © 2014 Society of Plastics Engineers     

Effects of different compatibilizers on the rheological,thermomechanical, and morphological properties of HDPE/LLDPE blend‐based nanocomposites

The influence of two different compatibilizers and their combination (maleic anhydride grafted high density polyethylene, HDPE‐g‐MA; maleic anhydride grafted linear low density polyethylene, LLDPE‐g‐MA; and 50/50 wt % mixture of these compatibilizers) on the rheological, thermomechanical, and morphological properties of HDPE/LLDPE/organoclay blend‐based nanocomposites was evaluated. Nanocomposites were obtained by melt‐intercalation in a torque rheometer in two steps. Masterbatches (compatibilizer/nanoclay 2:1) were obtained and subsequently diluted in the HDPE/LLDPE matrix producing nanocomposites with 2.5 wt % of nanoclay. Wide angle X‐ray diffraction (WAXD), steady‐state rheological properties, and transmission electron microscopy (TEM) were used to determine the influence of different compatibilizer systems on intercalation and/or exfoliation process which occurs preferentially in the amorphous phase, and thermomechanical properties. The LLDPE‐g‐MA with a high melt index (and consequently low viscosity and crystallinity) was an effective compatibilizer for this system. Furthermore, the compatibilized nanocomposites with LLDPE‐g‐MA or mixture of HDPE‐g‐MA and LLDPE‐g‐MA exhibited better nanoclay's dispersion and distribution with stronger interactions between the matrix and the nanoclay. These results indicated that the addition of maleic anhydride grafted polyethylene facilitates both, the exfoliation and/or intercalation of the clays and its adhesion to HDPE/LLDPE blend. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1726–1735, 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     

Dynamic rheological,morphology and mechanical properties of compatibilized LLDPE/EMA blends

Blends of linear low density polyethylene (LLDPE) and ethylene-co-methyl acrylate (EMA) having 60/40 composition was studied with and without compatibilizing agent. The compatibilizing agent used was maleic anhydride grafted linear low density polyethylene (LLDPE-g-MA). The LLDPE backbones of the compatibilizer are compatible with LLDPE blend component, whereas the maleic anhydride is affinated with carbonyl groups of EMA. The effectiveness of the compatibilizing agent was evaluated using different techniques like mechanical, thermal, scanning electron microscopy and rheological studies. Best compatibilization effect was found in the blend at a loading of 3 wt% of compatibilizer since at this level of compatibilizer complex viscosity, tensile strength, modulus, elongation at break, impact strength was found to be higher. The increase in the melt viscosity, storage modulus and thermal stability of the compatibilized blends indicated enhanced interactions between the discrete LLDPE and EMA phases induced by the functional compatibilizer.     

Morphology development,melt linear viscoelastic properties and crystallinity of polylactide/polyethylene/organoclay blend nanocomposites

Polylactide/polyethylene blends (PLA/PE) and their nanocomposites were prepared via the melt blending process. The effects of organoclay, compatibilizer (PE‐g‐MA), and PE content on morphology, linear viscoelastic properties of the melt and cold crystallization of the samples have been studied. The Palierne model is applied to predict the rheological behavior of unfilled blends. It implies that there is a quantitative agreement between model and experimental data for low PE content blend. From WAXD and the rheological behavior, it is shown that organoclay exhibits a higher extent of intercalation and dispersion in PLA/PE/organoclay nanocomposite than in PLA/organoclay nanocomposite. The DSC results present that the addition of compatibilizer into blend nanocomposite increases cold crystallization temperature of PLA by about 3°C. This can be explained by the role of compatibilizer in transfer of a part of organoclay from PLA matrix to droplets resulting in increase of PLA chain mobility and, therefore, slightly greater cold crystallization temperature. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41300.     

Preparation and characterization of low density polyethylene/ethylene methyl acrylate glycidyl methacrylate/organoclay nanocomposites

The effects of organoclay type, compatibilizer, and the addition order of components during melt‐blending process on the morphology and thermal, mechanical, and flow properties of ternary nanocomposites based on low‐density polyethylene (LDPE) were investigated. As a compatibilizer, ethylene/methyl acrylate/glycidyl methacrylate (E‐MA‐GMA), as organoclays Cloisites® 15A, 25A, and 30B were used. All samples were prepared by a corotating twin screw extruder, followed by injection molding. The highest increase of the basal spacing for ternary nanocomposites was obtained in LDPE/E‐MA‐GMA/Cloisite® 30B nanocomposites with interlayer spacing of 59.2 Å. Organoclay and compatibilizer addition did not influence the melting/crystallization behavior of the compositions, and both compatibilizer and organoclays had no significant nucleation activity in LDPE. Among the ternary nanocomposites, the maximum increase in tensile strength and tensile modulus values was observed for nanocomposites containing organoclay Cloisite® 15A. The improvement with respect to neat LDPE was 43% for tensile strength and 44% for tensile modulus. According to the mechanical analysis, the best sequence of component addition was the one in which LDPE, organoclay, and compatibilizer were simultaneously fed to the extruder in the first run, and the product of the first run was extruded once more. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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.     

Thermoplastic Elastomers Derived from Scrap Rubber Powder/LLDPE Blend with LLDPE‐graft‐(Epoxidized Natural Rubber) Dual Compatibilizer

Summary: Attempts were made to prepare thermoplastic elastomers (TPE) from scrap rubber powder (SRP) and linear low‐density polyethylene (LLDPE) as thermoplastic polymer matrix. The solid‐phase grafted copolymer of LLDPE (LLDPE‐g‐VM) and epoxidized natural rubber (ENR) were used as dual compatibilizers to improve the interfacial adhesion between SRP and LLDPE. The compatibilized SRP/LLDPE blends had obviously improved the interfacial properties between SRP particles and LLDPE. Using this method, thermoplastic elastomer was prepared successfully. The mechanical properties especially elongation at break was improved significantly. SEM and TEM studies showed that the ENR/LLDPE‐g‐VM dual compatibilizer improved the distribution state of SRP particles in LLDPE and the adhesion between SRP and LLDPE. DSC results showed a distinct glass transition at 74 °C of the interfacial region. The improvement in mechanical properties was attributed to the enhanced interfacial properties of the blend.

Surface of SRP particles of the composites compatibilized by the dual compatibilizer.     

Preparation of Cu/Dickite/LLDPE nanocomposites and synergistic effect of exfoliated dickite and nano‐Cu in LLDPE matrix

A novel anticorrosion packaging nanocomposite composed of LLDPE (linear low‐density polyethylene), nano‐sized Cu, and exfoliated dickite was prepared via melt mixing combined with melt extruding process. X‐ray diffraction and transmission electron microscopy (TEM) were employed to characterize the resultant nanocomposite. The results showed that most dickite layers were exfoliated and the nano‐Cu particles were distributed uniformly in the polymer matrix. The characteristic properties of the Cu/dickite/LLDPE nanocomposite were investigated using salt spray test, thermogravimetry analysis, mechanical test, and antibacterial test. The salt spray test results showed that exfoliated dickite and nano‐Cu improved the anticorrosion properties of the Cu/dickite/LLDPE nanocomposite in simulated ocean environment, respectively. Furthermore, the coexistence of exfoliated dickite and nano‐Cu in Cu/dickite/LLDPE nanocomposite produced a synergistic effect on enhancing the anticorrosion properties. Additionally, the co‐incorporation of exfoliated dickite and nano‐Cu in LLDPE matrix also improved the thermal‐oxidative stability and mechanical properties of the polymer matrix. The bactericidal properties evaluation showed that the Cu/dickite/LLDPE nanocomposite had better bactericidal ability because of the presence of nano‐Cu in LLDPE matrix. POLYM. COMPOS., 34:1061–1070, 2013. © 2013 Society of Plastics Engineers     

Synthesis of epoxy encapsulated organoclay nanocomposite latex via phase inversion emulsification and its gas barrier property

Waterborne epoxy–clay nanocomposites were prepared by encapsulation of organoclays in epoxy latex particles via phase inversion emulsification. The organoclays were exfoliated in the epoxy backbone before compounding with a hardener and subsequently dispersing in water. The encapsulation of clay platelets into the waterborne epoxy latex particle resulted in an exponential increase in particle size, from 5 to 10 times at a clay loading of only 1–2 wt%, respectively. The XRD patterns and TEM images show that clay platelets were well intercalated and exfoliated in the epoxy matrix. The gas barrier performance of the epoxy–clay nanocomposite strongly depended on the kind of organoclay. The best oxygen barrier efficiency was approximately 14% at 2 wt% clay loading.     

Subsurface mechanical properties of polyurethane/organoclay nanocomposite thin films studied by nanoindentation

A series of the exfoliated or intercalated PU/organoclay nanocomposite thin films were prepared by in situ polymerization of polyol/organoclay mixture, chain extender and diisocyanate. The surface mechanical properties of the PU/organoclay nanocomposite films were investigated by means of nanoindentation. The results show that the hardness, elastic modulus and scratch resistant of the nanocomposites dramatically improved with the incorporation of organoclay. This improvement was dependent on the clay content as well as the formation structure of clay in the PU matrix. At 3% clay content, the hardness and elastic modulus of intercalated nanocomposites increased by approximately 16% and 44%, respectively, compare to pure PU. For exfoliated nanocomposite, the improvements in these properties were about 3.5 and 1.6 times higher than the intercalated ones. The exfoliated PU nanocomposites also had greater hardness and showed better scratch resistance compared to the intercalated ones.     

Effect of heat treatment on the microstructural change of syndiotactic polystyrene/poly(styrene-co-vinyloxazolin)/clay nanocomposite

The fabrication of a syndiotactic polystyrene (sPS)/organoclay nanocomposite was conducted via a stepwise mixing process using poly(styrene-co-vinyloxazolin) (OPS), i.e. melt intercalation of OPS into organoclay followed by blending with sPS. The effects of several parameters, including type of organoclay and mixing temperature on the microstructure of the nanocomposite were investigated through X-ray diffraction patterns and rheological properties. The microstructure of the nanocomposite mainly depended on the arrangement type of the organic modifiers in the clay gallery. Using organoclays having lateral a bilayer arrangement exfoliated structure was obtained, whereas intercalated structure were obtained when organoclay with a paraffinic monolayer arrangement was employed in our sPS/OPS/organoclay system. In this work, a simple heat treatment on a previously prepared OPS/organoclay nanocomposite induced microstructural evolution with a favorable direction from intercalation to exfoliation. This phenomenon is attributed to a strong interaction between OPS and the clay surfaces, which is revealed by plateau behavior of the storage modulus in rheological properties. When heat is applied to the OPS/organoclay, the OPS chains and clay layers move together by promoted thermal motion of OPS chains, which results in disordering of stacked clay layers and exfoliation.     

Influence of maleated elastomer on filler dispersion,mechanical and antimicrobial properties of hybrid HDPE/clay/silver nanocomposites

This work analyses the effect of using ethylene-propylene-diene-monomer-grafted maleic anhydride (EPDM-g-MA) as compatibilizer to improve the interfacial properties and toughness of high-density polyethylene–organoclay–silver (HDPE/clay/silver) nanocomposites. EPDM-g-MA was reacted using ultrasound with a solution of AgNO₃ 0.04 M and ethylene glycol using ammonium hydroxide to obtain the silver ammonium complex. This silver-coated maleated EPDM was then melt mixed with HDPE and organoclay (Nanomer I28E) using a twin-screw extruder. Transmission electron microscopy (STEM) and X-ray diffraction (XRD) results confirmed the filler dispersion of both organoclay and silver nanoparticles into HDPE matrix when maleated EPDM was used. Both fillers were better dispersed and exfoliated by using this compatibilizer. The thermal stability enhancement of nanocomposites was confirmed using thermogravimetric analysis. Mechanical and antimicrobial properties demonstrated that better dispersed filler obtained with maleated EPDM enhanced the toughness and antimicrobial behaviour of HDPE/clay/silver hybrid nanocomposites. This confirmed that maleated EPDM was an efficient compatibilizer to obtain hybrid nanocomposites with enhanced properties to be used for several HDPE applications.     

Effect of blending sequence on the microstructure and properties of PBT/EVA‐g‐MAH/organoclay ternary nanocomposites

Ternary nanocomposites based on poly(butylene terephthalate) (PBT), maleic anhydride grafted poly(ethylene‐co‐vinyl acetate) (EVA‐g‐MAH), and organically modified montmorllonite (organoclays) were prepared through four different blending sequences in a Haake rheocord mixer: (1) To blend PBT, EVA‐g‐MAH and organoclays in one step; (2) First to prepare EVA‐g‐MAH/organoclay nanocomposite, then mix it with PBT to get the final nanocomposite; (3) To mix PBT with organoclays first, then the PBT/organoclay nanocomposite with EVA‐g‐MAH. (4) To mix organoclays with the PBT/EVA‐g‐MAH blend. The microstructure of the PBT/EVA‐g‐MAH/organoclay ternary hybrids was characterized by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). It was found that the blending sequence significantly influences the microstructure of PBT/EVA‐g‐MAH/organoclay ternary hybrids and the dispersion behavior of the organoclays in the polymer matrix. Tensile and impact properties of the hybrids were also studied. The results showed that the mixing sequence (2) gives the best tensile and impact strength due to its fine “sea‐island” morphology of PBT/EVA‐g‐MAH blend and good dispersion of the organoclays in the continuous PBT matrix.     

Thermostimulative shape memory effect of linear low‐density polyethylene/polypropylene (LLDPE/PP) blends compatibilized by crosslinked LLDPE/PP blend (LLDPE–PP)

A novel linear low‐density polyethylene (LLDPE)/polypropylene (PP) thermostimulative shape memory blends were prepared by melt blending with moderate crosslinked LLDPE/PP blend (LLDPE–PP) as compatibilizer. In this shape memory polymer (SMP) blends, dispersed PP acted as fixed phase whereas continuous LLDPE phase acted as reversible or switch phase. LLDPE–PP improved the compatibility of LLDPE/PP blends as shown in scanning electron microscopic photos. Dynamic mechanical analysis test showed that the melt strengths of the blends were enhanced with increasing LLDPE–PP content. A shape memory mechanism for this type of SMP system was then concluded. It was found that when the blend ratio of LLDPE/PP/LLDPE–PP was 87/13/6, the blend exhibited the best shape memory effect at stretch ratio of 80%, stretch rate of 25 mm/min, and recovery temperature of 135°C. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Effect of exfoliation and dispersion on the yield behavior of melt‐compounded polyethylene–montmorillonite nanocomposites

The yield behavior of melt‐mixed nanocomposites containing 5 wt % organically modified montmorillonite in matrices of a linear low‐density polyethylene (LLDPE) or a modified polyethylene was studied as a function of the temperature and strain rate. In the melt‐mixed LLDPE nanocomposite, the montmorillonite showed a slight increase in the clay spacing, which suggested that the clay was at best intercalated. Transmission electron microscopy (TEM) images showed that the dispersion in this nanocomposite was poor. The use of the modified polyethylene promoted exfoliation of the clay tactoids in the nanocomposite, as assessed by X‐ray diffraction and TEM. In both nanocomposites, the yield mechanisms were insensitive to the addition of the organoclay, even though modest increases in the modulus were produced. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3044–3049, 2006