Structure and thermal/mechanical properties of poly (ϵ-caprolactone)-clay blend

Montmorillonite was organically modified with distearyldimethylammonium chloride. This organically modified clay (OMON) and poly (ϵ-caprolactone) (PCL) were solvent-cast blended with chloroform, and the structure and properties of the resulting PCL-clay blends were investigated. From isothermal crystallization experiments, it was found that a small amount of OMON in the blend accelerated the crystallization of PCL, whereas a large amount of the organophilic clay delayed it. From small-and wide-angle X-ray scattering measurements, it was found that the silicate layers forming the clay could not be dispersed individually in the PCL blends. In other words, the clay seemed to exist as the tactoids consisting of some silicate layers. These tactoids formed a remarkable geometric structure; that is, their surface planes lay almost parallel to the blend film surface. Furthermore, the tactoids were stacked with insertion of PCL lamellae in the film-thickness direction. Preferred orientation of the PCL crystallites was induced by the presence of the clay. During the drawing process of the blends, fibrillation took place with formation of planelike voids developed on the plane parallel to the film surface. From dynamic viscoelastic measurements, it was shown that intercalation of PCL chains into the layered silicates did not take place in the blends prepared by the solvent-cast method used in this work. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2211–2220, 1997     

Biodegradable polyester layered silicate nanocomposites based on poly(ϵ‐caprolactone)

Nanocomposites based on biodegradable poly(?‐caprolactone) (PCL) and layered silicates (montmorillonite, MMT) were prepared either by melt interaction with PCL or by in situ ring‐opening polymerization of ?‐caprolactone as promoted by the so‐called coordination‐insertion mechanism. Both non‐modified clays (Na⁺ ‐MMT) and silicates modified by various alkylammonium cations were studied. Mechanical and thermal properties were examined by tensile testing and thermogravimetric analysis. Even at a filler content as low as 3 wt% of inorganic layered silicate, the PCL‐layered silicate nanocomposites exhibited improved mechanical properties (higher Young's modulus) and increased thermal stability as well as enhanced flame retardant characteristics as a result of a charring effect. It was shown that the formation of PCL‐based nanocomposites depended not only on the nature of the ammonium cation and related functionality but also on the selected synthetic route, melt intercalation vs. in situ intercalative polymerization. Interestingly enough, when the intercalative polymerization of ?‐caprolactone was carried out in the presence of MMT organo‐modified with ammonium cations bearing hydroxyl functions, nanocomposites with much improved mechanical properties were recovered. Those hybrid polyester layered silicate nanocomposites were characterized by a covalent bonding between the polyester chains and the clay organo‐surface as a result of the polymerization mechanism, which was actually initiated from the surface hydroxyl functions adequately activated by selected tin (II) or tin (IV) catalysts.     

Study of the biodegradable poly(ε‐caprolactone)/clay nanocomposite foams

In this article, biodegradable poly(ε‐caprolactone)/layered silicate nanocomposites were prepared and characterized. The dispersion state of modified clay in PCL matrix and its effect on thermal, rheological and mechanical properties of PCL were studied. The PCL/clay nanocomposites were then foamed using chemical foaming method. Cellular parameters such as mean cell size, cell wall thickness and cell densities of nanocomposite foams with different clay loading were collected. Effect of layered silicate on the structure and mechanical properties of PCL foams were evaluated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

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     

Using maleic anhydride grafted poly(lactic acid) as a compatibilizer in poly(lactic acid)/layered‐silicate nanocomposites

The goal of this work was to prepare exfoliated poly(lactic acid) (PLA)/layered‐silicate nanocomposites with maleic anhydride grafted poly(lactic acid) (PLA–MA) as a compatibilizer. Two different layered silicates were used in the study: bentonite and hectorite. The nanocomposites were prepared by the incorporation of each layered silicate (5 wt %) into PLA via solution casting. X‐ray diffraction of the prepared nanocomposites indicated exfoliation of the silicates. However, micrographs from transmission electron microscopy showed the presence of intercalated and partially exfoliated areas. Tensile testing showed improvements in both the tensile modulus and yield strength for all the prepared nanocomposites. The results from the dynamic mechanical thermal analysis showed an improvement in the storage modulus over the entire temperature range for both layered silicates together with a shift in the tan δ peak to higher temperatures. The effect of using PLA–MA differed between the two layered silicates because of a difference in the organic treatment. The bentonite layered silicate showed a more distinct improvement in exfoliation and an increase in the mechanical properties because of the addition of PLA–MA in comparison with the hectorite layered silicate. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1852–1862, 2006     

Structure and properties of poly(lactic acid)/poly(ε‐caprolactone) nanocomposites with kinetically induced nanoclay location

Poly(lactic acid)/poly(ε‐caprolactone)/organically modified montmorillonite (PLA/PCL/OMMT) nanocomposites were melt‐processed in a twin‐screw extruder under high shear conditions. As a result of the processing conditions employed, the OMMT layers located in the less compatible PCL phase in all the ternary nanocomposites. The morphology of the PLA/PCL blend evolved from “sea‐island” to co‐continuous upon the addition of OMMT. Both the X‐ray diffraction (XRD) and viscoelastic characterization suggested similar OMMT dispersion in the reference PLA binary and in the PLA/PCL ternary nanocomposites, regardless of its location in the PLA and PCL phase, respectively. The reinforcing effect of the organoclay was also similar. The addition of OMMT to the PLA/PCL blend fully compensated the loss in stiffness and oxygen barrier performance produced by PCL in PLA; the nanocomposite with 3% OMMT showed the same modulus and permeability values as those of pure PLA. Moreover, the ductile behavior (elongation at break > 80%) of the PLA/PCL blend remained constant even in the nanocomposite containing 5% OMMT. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43815.     

An investigation of melt rheology and thermal stability of poly(lactic acid)/ poly(butylene succinate) nanocomposites

A systematic investigation of the rheological and thermal properties of nanocomposites prepared with poly(lactic acid) (PLA), poly(butylene succinate) (PBS), and organically modified layered silicate was carried out. PLA/PBS/Cloisite 30BX (organically modified MMT) clay nanocomposites were prepared by using simple melt extrusion process. Composition of PLA and PBS polymers were fixed at a ratio of 80 to 20 by wt % for all the nanocomposites. Rheological investigations showed that high clay (> 3 wt %) contents strongly improved the viscoelastic behavior of the nanocomposites. Percolation threshold region was attained between 3 and 5 wt % of clay loadings. With the addition of clay content for these nanocomposites, liquid‐like behavior of PLA/PBS blend gradually changed to solid‐like behavior as shown by dynamic rheology. Steady shear showed that shear viscosity for the nanocomposites decreased with increasing shear rates, exhibiting shear‐thinning non‐Newtonian behavior. At higher clay concentrations, pseudo‐plastic behavior was dominant, whereas pure blend showed almost Newtonian behavior. Thermogravimetric analysis revealed that both initial degradation temperature (at a 2% weight loss) and activation energy of thermal decomposition nanocomposite containing 3 wt % of C30BX were superior to those of other nanocomposites as well as to those of PLA/PBS blend. Nanocomposite having 1 wt % of C30BX did not achieve expected level of thermal stability due to the thermal instability of the surfactant present in the organoclay. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Epoxy/poly(ɛ‐caprolactone) nanocomposites: Effect of transformations of structure on crystallization

The influence of morphology of the epoxy/poly(?‐caprolactone) (PCL) system and corresponding nanocomposites with organophilized layered silicate on PCL crystallization was studied by differential scanning calorimetry, scanning, and transmission electron microscopy. The results obtained indicate a significant affecting of nonisothermal PCL crystallization by phase morphology brought about by the reaction‐induced phase separation (RIPS) influenced either by various nanoclay contents or the epoxy/PCL ratio. Dispersed morphology of PCL matrix with epoxy globules induces crystallization at higher temperatures. The inverse dispersed morphology of epoxy matrix with PCL inclusions causes crystallization at lower temperature. The co‐continuous morphology induces crystallization in both steps. Rate of the second crystallization step is substantially higher than that in the first step. No nucleation effect has been found in the nanocomposites with the added nanofiller. Multicomponent samples show retarded crystallization, i.e., lower crystallinities and lower overall crystallization rate compared with neat PCL. The results obtained suggest that it is primarily morphological/interfacial effects that play a decisive role in the crystallization behavior of PCL in the epoxy/PCL/clay system. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3197–3204, 2013     

Mechanical and rheological properties of the maleated polypropylene–layered silicate nanocomposites with different morphology

Three types of maleated polypropylene–layered silicate nanocomposites with different dispersion states of layered silicate (deintercalated, intercalated, and exfoliated states) are prepared from two kinds of polypropylenes with different molecular weights, organically modified layered silicate and pristine montmorillonite to investigate the effect of the final morphology of the nanocomposite on the rheological and mechanical properties. Maleated polypropylene with high molecular weight intercalates slowly and the other with low molecular weight exfoliates fast into the organophilic layered silicates. Rheological properties such as oscillatory storage modulus, nonterminal behavior, and relative viscosity has close relationship with the dispersion state of layered silicates. The exfoliated nanocomposite shows the largest increase and the deintercalated nanocomposite shows almost no change in relative shear and complex viscosities with the clay content. The exfoliated nanocomposite shows the largest drop in complex viscosity due to shear alignment of clay layers in the shear flow. In addition, the final dispersion state of layered silicates intimately relates to the mechanical property. The dynamic storage moduli of nanocomposites show the same behavior as the relative shear and complex viscosities. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1526–1535, 2003     

Poly(ϵ-caprolactone)/poly(ethylene oxide) diblock copolymer II. Nonisothermal crystallization and melting behavior

The nonisothermal crystallization behavior and melting process of the poly(ϵ-caprolactone) (PCL)/poly(ethylene oxide) (PEO) diblock copolymer in which the weight fraction of the PCL block is 0.80 has been studied by using differential scanning calorimetry (DSC). Only the PCL block is crystallizable, the PEO block with 0.20 weight fraction cannot crystallize. The kinetics of the PCL/PEO diblock copolymer under nonisothermal crystallization conditions has been analyzed by Ozawa's equation. The experimental data shows no agreement with Ozawa's theoretical predictions in the whole crystallization process, especially in the later stage. A parameter, kinetic crystallinity, is used to characterize the crystallizability of the PCL/PEO diblock copolymer. The amorphous and microphase separating PEO block has a great influence on the crystallization of the PCL block. It bonds chemically with the PCL block, reduces crystallization entropy, and provides nucleating sites for the PCL block crystallization. The existence of the PEO block leads to the occurrence of the two melting peaks of the PCL/PEO diblock copolymer during melting process after nonisothermal crystallization. The comparison of nonisothermal crystallization of the PCL/PEO diblock copolymer, PCL/PEO blend, and PCL and PEO homopolymers has been made. It showed a lower crystallinity of the PCL/PEO diblock copolymer than that of others and a faster crystallization rate of the PCL/PEO diblock copolymer than that of the PCL homopolymer, but a slower crystallization rate than that of the PCL/PEO blend. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1793–1804, 1997     

Thermal properties and flammability of acrylic nanocomposites based upon organophilic layered silicates

Summary Thermal and mechanical properties of poly(methylmethacrylate-co-dodecylmethacrylate) nanocomposites based upon exfoliated organophilic layered silicates, were investigated as a function of the silicate and comonomer content. Layered silicates such as sodium bentonite were rendered organophilic by means of ion-exchanging sodium cations for N,N,N,N-dioctadecyl-dimethyl-ammonium cations. Silicate exfoliation was enhanced by means of 5 and 10 wt.-% dodecyl-methacrylate (LMA) addition to afford translucent reinforced acrylic nanocomposites. In contrast to conventional filled acrylic polymers, only 10 wt.-% organophilic silicate was sufficient to increase Young's modulus from 2200 to 4030 MPa, glass temperature from 72 to 80 °C and degradation temperature from 220 to 256 °C with respect to the neat MMA/LMA (90 wt.-%/10 wt.-%) copolymer. Flammability studies, performed on a cone calorimeter, revealed that the maximum heat release rate of MMA/LMA copolymer nanocomposite decreased from 837 kW/m² to 566 kW/m². The nanocomposite morphology was examined by means of transmission electron microscopy (TEM). Received: 28 May 1999/Revised version: 24 September 1999/Accepted: 24 September 1999     

Effect of organically modified layered silicates on the morphology of symmetrical blends of polystyrene and poly(methyl methacrylate)

The changes in morphology caused by the addition of organically modified layered silicate on equal volume fraction blends of polystyrene and poly(methyl methacrylate) are investigated. In thin films supported on silicon, without layered silicates, the PMMA forms a layer on the silicon, while the PS tend to minimize contact with both the hydrophilic silicon substrate and the PMMA phase, and tend to form discrete domains on top of the PMMA layer. With the introduction of layered silicates, the characteristic length scale of the structure decreases. On the other hand, in bulk samples, without the layered silicates, the equal volume fraction blend has the PS domains in a PMMA matrix. At 0.6 wt% of added silicate, in both thin film and bulk, the blend morphology converts from discrete to co-continuous. Electron micrographs reveal well dispersed silicate sheets locating at the interface between small PS domains in the PMMA phase. The change in morphology is conjectured to be the result of the interfacial location of the layered silicates rather than the change in viscosity ratio between the two phases.     

Miscibility and crystallization of poly(ethylene oxide) and poly(ε-caprolactone) blends

Blends of poly(ethylene oxide) (PEO) with poly(ε-caprolactone) (PCL), both semicrystalline polymers, were prepared by co-dissolving the two polyesters in chloroform and casting the mixture. Phase contrast microscopy was used to probe the miscibility of PEOB/PCL blends. Experimental results indicated that PEO was immiscible with PCL because the melt was biphasic. Crystallization of PEO/PCL blends was studied by differential scanning calorimetry and analyzed by the Avrami equation. The crystallization rate of PEO decreased with the increase of PCL in the blends while the crystallization mechanism did not change. In the case of the isothermal crystallization of PCL, the crystallization mechanism did not change, and the change in the crystallization rate was not very big, or almost constant with the addition of PEO, compared with the change of the crystallization rate of PEO.     

Nanoclay dispersion in a miscible blend: an assessment through rheological analysis

In this study, miscible polymer blend nanocomposite of Poly(ethylene oxide)/Poly(methyl methacrylate), (PEO/PMMA), with sodium montmorillonite (Na⁺-MMT) clay were prepared at a constant concentration of nanoparticles via different solution intercalation methods. The resultant nanocomposites possess different structure and dispersion of Na⁺-MMT clays which are assessed through a combination of transmission electron microscopy (TEM) and X-ray diffraction (XRD). The rheology of the neat blend and two different layered silicate nanocomposites were investigated using linear viscoelastic measurements with a parallel plate rheometry at small strain amplitudes. It was found that regardless of the extent of dispersion, the storage and loss modulus increased by incorporating the nanoparticles into the matrix of PEO/PMMA. Moreover, at low frequencies the rheological response of the nanocomposite in which layered silicates benefit from a better dispersion becomes relatively invariant with frequency and represents a mediocre solid-like behavior in comparison to the nanocomposite in which the nanoparticles are intercalated or agglomerated.     

Blends of cellulose with nylon 6 and poly(ε-caprolactone) prepared by a solution-coagulation method

Conditions are described for preparing blends of cellulose with nylon 6 (Ny6) and poly(ε-caprolactone) (PCL) from solutions in N,N-dimethylacetamide (DMAc)– lithium chloride (LiCl) by coagulation in a non-solvent. The binary blend films of both series, obtained over a wide composition range (10/90–90/10) from mixed polymer solutions, were characterized by wide-angle x-ray diffraction (WAXD), differential scanning calorimetry (DSC), and dynamic mechanical measurements. In the two series of cellulose blends the other component (Ny6 or PCL) was crystalline at every composition, but there was some degree of disproportional reduction of the crystallinity with an increase in cellulose content. From the dynamic Mechanical testing, the cellulose/Ny6 blends were found to be almost immiscible, although the possibility of a certain level of partial miscibility in the non-crystalline regions was admitted at high cellulose concentrations (>80 wt%). For the cellulose/PCL blends, it was found that there was evidently an amorphous phase where a limited amount of cellulose could be well mixed with PCL. A relatively large shift of the midpoint in the PCL glass transition region to the higher temperature side was noted at the compositions containing 20 and 30 wt% cellulose. This effect is discussed in relation to the requirement of an optimum balance in the density of the interacting hydroxyl and ester groups, for obtaining true miscibility of cellulosics with PCL at the molecular level.     

Nonisothermal crystallization behavior of poly(ϵ‐caprolactone)/attapulgite nanocomposites by DSC analysis

Nanocomposites based on biodegradable poly(ε‐caprolactone) (PCL) and attapulgite (AT) were prepared by solution mixing. The nonisothermal crystallization of the pure PCL and PCL/AT nanocomposites at different AT contents and different cooling rates were investigated by differential scanning calorimetry (DSC). There are significant dependence of nonisothermal crystallization behavior and kinetics of PCL/AT nanocomposites on the AT content and cooling rate. The Jeziorny method has been employed to analyze the DSC data. The results show that Jeziorny method could describe this system well. It can be concluded that AT can be used as an effective nucleating agent and has effects on the growth of crystallites in the crystallization process of PCL matrix. POLYM. ENG. SCI., 47:460–466, 2007. © 2007 Society of Plastics Engineers.     

Crystallization behavior of PEO in blends of poly(ethylene oxide)/poly(2‐vinyl pyridine)‐b‐(ethylene oxide) block copolymer

The crystallization behavior of two molecular weight poly(ethylene oxide)s (PEO) and their blends with the block copolymer poly(2‐vinyl pyridine)‐b‐poly(ethylene oxide) (P2VP‐b‐PEO) was investigated by polarized optical microscopy, thermogravimetric analysis, differential scanning calorimetry, and atomic force microscopy (AFM). A sharp decreasing of the spherulite growth rate was observed with the increasing of the copolymer content in the blend. The addition of P2VP‐b‐PEO to PEO increases the degradation temperature becoming the thermal stability of the blend very similar to that of the block copolymer P2VP‐b‐PEO. Glass transition temperatures, T_g, for PEO/P2VP‐b‐PEO blends were intermediate between those of the pure components and the value increased as the content of PEO homopolymer decreased in the blend. AFM images showed spherulites with lamellar crystal morphology for the homopolymer PEO. Lamellar crystal morphology with sheaf‐like lamellar arrangement was observed for 80 wt% PEO(200M) and a lamellar crystal morphology with grain aggregation was observed for 50 and 20 wt% blends. The isothermal crystallization kinetics of PEO was progressively retarded as the copolymer content in the blend increased, since the copolymer hinders the molecular mobility in the miscible amorphous phase. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Fabrication and characterization of biodegradable poly(lactic acid)/layered silicate nanocomposites

In this study biocompatible/biodegradable poly(lactic acid) (PLA)/layered silicate nanocomposites (PLSNs) were successfully prepared by the intercalation of PLA polymer into organically modified layered silicate through the solution mixing process. Both X‐ray diffraction data and transmission electron microscopy images of PLSNs indicate most of the swellable silicate layers were disorderedly intercalated into the PLA matrix. Mechanical properties of the 0.1 wt% silicate‐containing fabricated nanocomposites performed by dynamic mechanical analysis have significant improvements in the storage modulus when compared to that of neat PLA matrix. Adding more layered silicates into PLA matrix induced a decrease in the mechanical properties of PLSNs, probably due to the presence of a large dimension of porosity in the fabricated nanocomposites. POLYM. ENG. SCI., 45:1615–1621, 2005. © 2005 Society of Plastics Engineers     

Thermorheological properties of poly (ε‐caprolactone)/polylactide blends

Blends of poly (ε‐caprolactone) (PCL)/polylactide (PLA) were prepared by solution‐casting method to study their thermal and rheological properties. Differential scanning calorimetry thermographs have shown two separate melting peaks in the blends, which are indicative of immiscible structure at all compositions. Scanning electron microscopy images show droplet morphology of PCL into PLA matrix up to 40 wt% of PCL. Above this concentration, the co‐continuous morphology starts to appear, which becomes again droplet morphology for blends with concentration of PCL higher than about 60 wt%. The viscoelastic properties of the various blends were investigated using rotational rheometry. The enhancement of the elastic modulus of blends at small frequencies at which terminal zone behavior is expected, is a signature behavior of immiscible systems due to the presence of interface and contribution to the stress from interfacial tension. Two emulsion models were used to predict the viscoelastic properties of the blends from the corresponding properties of their pure components that led to the determination of the interfacial tension of PCL/PLA in agreement with experimental findings. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Porous biodegradable polyesters. II. Physical properties,morphology, and enzymatic and alkaline hydrolysis of porous poly(ϵ‐caprolactone) films

Porous poly(?‐caprolactone) (PCL) films were prepared by water extraction of poly(ethylene oxide) (PEO) from their solution‐cast phase‐separated blend films and the dependence of their blend ratio [X_PCL = PCL/(PEO + PCL)] and molecular weight of PEO on the porosity, pore size, crystallinity, crystalline thickness, mechanical properties, morphology, and enzymatic and alkaline hydrolysis of the porous PCL films were investigated. The film porosity or extracted weight ratio was in good agreement with the expected values, irrespective of X_PCL and molecular weight of PEO. The maximum pore size was larger for the porous films prepared using PEO having a lower molecular weight, compared with films prepared using PEO having a higher molecular weight at the same X_PCL. Differential scanning calorimetry of the porous PCL films revealed that their crystallinity and crystalline thickness were almost constant, regardless of X_PCL and molecular weight of PEO. The Young's modulus and tensile strength of the porous films decreased, whereas the elongation‐at‐break increased with decreasing X_PCL. The enzymatic and alkaline hydrolysis rates of the porous films increased with a decrease in X_PCL and an increase in the molecular weight of PEO. The porous PCL films having Young's modulus in the range of 2–24 kg/mm² and enzymatic hydrolysis rate in the range of one‐ to 20‐fold that of the nonporous PCL film could be prepared by altering X_PCL and the molecular weight of PEO. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2281–2291, 2001