Bottle‐to‐bottle recycling of PET via nanostructure formation by melt intercalation in twin screw compounder: Improved thermal,barrier, and microbiological properties

Attempts have been made to modify the properties of the injection processing‐scraped PET (denoted as RPET) via intercalation with different levels of organically modified nanoclay (montmorillonite) by melt blending in a corotating twin screw compounder. The clay platelets dispersion state has been qualitatively correlated with the melt linear viscoelastic as well as tensile and barrier properties of the prepared nanocomposites. Oxygen permeation of the nanocomposite PET films showed significant reduction compared with the pristine PET polymer. All the PET/nanoclay composites exhibited no bacterial growth, with no potentiality to generate acetaldehyde, as measured by GC/Mass analyzer. X‐ray diffractometry and transmission electron microscopy performed on the scraped PET/organoclay nanocomposite samples showed increase in d₀₀₁ spacing of the clay layers and their dispersion throughout the PET matrix. Differential scanning calorimetry analysis showed higher crystallization temperature as well as crystallization enthalpy (ΔH_c) for the nanocomposite samples, compared with the unprocessed virgin PET. The RPET nanocomposite samples composed of 3 and 5% of nanoclay exhibited enhanced melt elastic modulus and pseudosolid‐like behavior at low shear frequencies measured by rheomechanical spectroscopy than the unfilled pristine‐scraped PET, indicating the formation of nanoscopic network structure by the clay platelets, which leads to the development of nanostructured resin. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Modification of polyethylene–octene elastomer by silica through a sol–gel process

In this study, tetraethoxysilane (TEOS) and a metallocene polyethylene–octene elastomer (POE) were chosen as the ceramic precursor and the continuous phase, respectively, for the preparation of new hybrids by an in situ sol–gel process. To obtain a better hybrid, a maleic anhydride‐grafted polyethylene–octene elastomer (POE‐g‐MAH), used as the continuous phase, was also investigated. Characterizations of POE‐g‐MAH/SiO₂ and POE/SiO₂ hybrids were performed by Fourier transform infrared (FTIR) and ²⁹Si solid‐state nuclear magnetic resonance (NMR) spectrometers, a differential scanning calorimeter (DSC), a thermogravimetry analyzer, and an Instron mechanical tester. The results showed that the POE‐g‐MAH/SiO₂ hybrid could improve the properties of the POE/SiO₂ hybrid because the interfacial force between the polymer matrix and the silica network was changed from hydrogen bonds into covalent Si? O? C bonds through dehydration of hydroxy groups in POE‐g‐MAH with residual silanol groups in the silica network. The existence of covalent Si? O? C bonds was proved by FTIR spectra. For the POE/SiO₂ and POE‐g‐MAH/SiO₂ hybrids, maximum values of the tensile strength and the glass transition temperature were found at 9 wt % SiO₂ since a limited content of silica might be linked with the polymer chains through the covalent bond. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 966–972, 2003     

Preparation and characterization of polymer/organosilicate nanocomposites based on unmodified LDPE

Low‐density polyethylene (LDPE)/silicate nanocomposites were prepared by the melt compounding and solution blend methods using unmodified LDPE polymer and layered silicates with different aspect ratio. X‐ray diffraction (XRD) analysis performed on composites obtained by dispersing the organosilicates in molten LDPE evidenced an exfoliated or partially exfoliated structure for the low aspect ratio silicate (laponite) in contrast to the high aspect ratio silicate (montmorillonite), which led to the formation of intercalated nanocomposites. With regard to the preparation method, the melt compounding method was more effective in forming exfoliated/highly intercalated LDPE nanocomposites compared with the solution blend method (using CCl₄ as a solvent). A gradual increase in crystallization temperatures (T_c) with increasing laponite content for LDPE‐organolaponite nanocomposites was revealed by differential scanning calorimetry (DSC) measurements. Thermogravimetric analysis and tensile measurements results indicated that thermal stability and elastic modulus increment were more prevalent for nanocomposites prepared using organomontmorillonite as filler. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Some relationships for the orientational drawing of polymers

The orientational drawing of films from different thermoplastics has been studied. The value of the activation energy of drawing in the regions of forced elasticity (necking), high elasticity, and viscous flow (ΔE₁, ΔE₂, ΔE₃) has been found to vary directly with the activation energy for viscous flow of the melt (ΔE_η). Here ΔE₁ < ΔE₂ < ΔE₃ = ΔE_η. Thus Δ E_η characterizes the potential of thermoplastics for orientational drawing under different deformation conditions, since it reflects simultaneously both the intermolecular interaction level and chain flexibility. For maximum chain orientation, the calculated values for the change in the entropy are close to that of the entropy change during crystallization (melting) of the same polymer. The deformation of polymer may be described as a deformation of an entanglement network from the standpoint of classic elasticity theory. Some parameters for an entanglement network were calculated from the results of the drawing experiments. The density of the entanglement network (DEN) depend on the polymer composition: For flexible-chain polymers the DEN is less, for rigid-chain polymers (with coiled chains) it is higher. The DEN affects the maximum (prebreak) drawing ratio: The greater the DEN, the smaller the ratio to which a film can be drawn. At high orientation, the tensile strength of different polymer films tend to be similar, if drawing is not accompanied by crazing.     

Construction of reversible crosslinking–decrosslinking system consisting of a polymer bearing vicinal tricarbonyl structure and poly(ethylene glycol)

In this article, we report a novel reversible crosslinking–decrosslinking system consisting of a polymer bearing vicinal tricarbonyl moieties in its side chains and poly(ethylene glycol) (PEG). A mixture of the tricarbonyl polymer and PEG (0.1 equiv of OH groups relative to the vicinal tricarbonyl moieties) in CH₂Cl₂ spontaneously turned into an orange-colored gel, in which a network structure was formed through hemiketal linkages. Conversely, the resulting networked polymer could be decrosslinked by treatment with water-containing solvent to recover the linear vicinal tricarbonyl polymer as its hydrate in 90 % yield. Following dehydration process by heating at 100 °C under reduced pressure regenerated the original vicinal tricarbonyl polymer.     

Mechanical,thermal properties and isothermal crystallization kinetics of biodegradable poly(butylene succinate-<Emphasis Type="Italic">co</Emphasis>-terephthalate) (PBST) fibers

Biodegradable copolymer poly(butylene succinate-co-terephthalate) (PBST), with 70 mol% butylene terephthalate (BT), was melt-spun into fibers with take-up velocity of 2 km/min. The mechanical and thermal properties of the as-spun fibers were investigated through tensile test, DSC and TGA. Compared to poly(butylene terephthalate) (PBT) fibers, PBST fibers exhibited lower initial tensile modulus and higher tensile elongation at break which indicated their better flexibility. DSC results showed high melting temperature (ca.180.7 °C) of PBST fibers helpful to the textile processing compared to other biodegradable polyesters. Furthermore, isothermal crystallization behaviors of PBST fibers at low and high supercoolings were investigated by DSC and DLI, respectively. The measurement of crystallization kinetics at low supercoolings indicated that Avrami exponent n for PBST fibers was at a range of 2.9 to 3.3, corresponding to the heterogeneous nucleation and a 3-dimensional spherulitic growth. Similar results were given for isothermal crystallization behavior at high supercoolings investigated by DLI technique. Additionally, the equilibrium melting temperature of PBST fibers was obtained for 206.5 °C by Hoffman-Weeks method. Further investigation through DLI measurement provided the temperature at maximum crystallization rate for PBST fibers located at about 90 °C, which was very useful to polymer processing.     

Mechanical and morphological properties of lyocell blends: Comparison with lyocell nanocomposites (I)

The mechanical properties and morphologies of polyblends of lyocell with three different fillers are compared. Poly(vinyl alcohol) (PVA), poly(vinyl alcohol‐co‐ethylene) (EVOH), and poly(acrylic acid‐co‐maleic acid) (PAM) were used as fillers in blends with lyocell produced through solution blending. The variations of their properties with polymer matrix filler content are discussed. The ultimate tensile strength of the PVA/lyocell blend is highest for a blend lyocell content of 30 wt %, and decreases as the lyocell content is increased up to 40 wt %. The ultimate tensile strengths of the EVOH/lyocell and PAM/lyocell blends are highest for a lyocell loading of 20 wt %, and decrease with the increasing filler content. The variations in the initial moduli of the blends with filler content are similar. Of the three blend systems, the blends with PVA exhibit the best tensile properties. Lyocell/organoclay hybrid films were prepared by the solution intercalation method, using dodecyltriphenylphosphonium–Mica (C₁₂PPh‐ Mica) as the organoclay. The variation of the mechanical tensile properties of the hybrids with the matrix polymer organoclay content was examined. These properties were found to be optimal for an organoclay content of up to 5 wt %. Even polymers with low organoclay contents exhibited better mechanical properties than pure lyocell. The addition of organoclay to lyocell to produce nanocomposite films was found to be less effective in improving its ultimate tensile strength than blending lyocell with the polymers. However, the initial moduli of the nanocomposites were found to be higher than those of the polyblend films. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Crystallization and melting behavior of HDPE in HDPE/teak wood flour composites and their correlation with mechanical properties

The nonisothermal crystallization behavior and melting characteristics of high‐density polyethylene (HDPE) in HDPE/teak wood flour (TWF) composites have been studied by differential scanning calorimetry (DSC) and wide angle X‐ray diffraction (WAXD) methods. Composite formulations of HDPE/TWF were prepared by varying the volume fraction (?_f) of TWF (filler) from 0 to 0.32. Various crystallization parameters evaluated from the DSC exotherms were used to study the nonisothermal crystallization behavior. The melting temperature (T_m) and crystallization temperature (T_p) of the composites were slightly higher than those of the neat HDPE. The enthalpy of melting and crystallization (%) decrease with increase in the filler content. Because the nonpolar polymer HDPE and polar TWF are incompatible, to enhance the phase interaction maleic anhydride grafted HDPE (HDPE‐g‐MAH) was used as a coupling agent. A shift in the crystallization and melting peak temperatures toward the higher temperature side and broadening of the crystallization peak (increased crystallite size distribution) were observed whereas crystallinity of HDPE declines with increase in ?_f in both DSC and WAXD. Linear correlations were obtained between crystallization parameters and tensile and impact strength. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Nylon-6 containing metal halides II: Tensile properties

Following the reported pronounced effects of metal halides incorporated into nylon-6 on its glass transition temperature, melting temperature, melt viscosity, crystallization rate and final crystallinity, the tensile mechanical properties and crystallinity of nylon-6 as affected by the absorption of metal halides were studied. At low salt content, some of the mechanical properties are substantially altered and at higher salt concentrations the ductile polymer becomes brittle. There is no marked difference between the salts studied (CuCl₂, CuBr₂, FeCl₃) regarding their effects on the polymer mechanical properties. In the concentration range studied, absorbed Cu salts do not significantly change the polymer's degree of crystallinity, whereas absorbed FeCl₃ results in a pronounced reduction, indicating its effect also on the crystalline phase.     

Structure and crystallization behavior of Nylon 66/multi-walled carbon nanotube nanocomposites at low carbon nanotube contents

Multi-walled carbon nanotubes (MWNTs) were modified with poly(hexamethylene adipamide) (also known as Nylon 66) via a controlled polymer solution crystallization method. A “nanohybrid shish kebab” (NHSK) structure was found wherein the MWNT resembled the shish while Nylon 66 lamellar crystals formed the kebabs. These Nylon 66-functionalized MWNTs were used as precursors to prepare polymer/MWNT nanocomposites. Excellent dispersion was revealed by optical and electron microscopies. Nitric acid etching of the nanocomposites showed that MWNT formed a robust network in Nylon 66. Non-isothermal DSC results showed multiple melting peaks, which can be attributed to lamellar thickness changes upon heating. The crystallite sizes L₁₀₀ and L₀₁₀ of Nylon 66, determined by WAXD, decreased with increasing MWNT contents. Isothermal DSC results showed that crystallization kinetics increased first and then decreased with increasing MWNT contents in Nylon 66. This study showed that the effect of MWNTs on Nylon 66 crystallization is twofold: MWNTs provide heterogeneous nucleation sites for Nylon 66 crystallization while the tube network structure hinders large crystal growth.     

Osmotic Dehydration of Apple Cylinders: II. Continuous Medium Flow Heating Conditions

Mass transfer of apple cylinders during osmotic dehydration was quantitatively investigated under continuous medium flow conditions. The influences of the main process variables (solution concentration, operation temperature, contact time, and solution flow rate) were determined. A second-order polynomial regression model was used to relate weight reduction (WR), moisture loss (ML), solids gain (SG), and mass diffusivity (D _m and D _s ) to process variables. The conventional diffusion model using a solution of Fick's unsteady state law involving a finite cylinder was applied for moisture diffusivity and solute diffusivity determination. Diffusion coefficients were in the range of 10^?9–10^?10 m²/s, and moisture diffusivity increased with temperature and flow rate, increased with solution concentration (> 50°Brix), and decreased with increasing solution concentration (< 50°Brix), but solids diffusivity increased with temperature and concentration and decreased with increasing flow rate. A continuous-flow osmotic dehydration (CFOD) contactor was developed to be a more efficient process in terms of osmotic dehydration efficiency: time to reach certain weight reduction (T _w ) and moisture loss (T _m ) were shorter than that of conventional osmotic (COD) dehydration processes. Effectiveness evaluation functions used in this study could be widely applied to osmotic dehydration system evaluation.     

Solid state NMR analysis of poly(L‐lactide) random copolymer with poly(ε‐caprolactone) and its reactive extrusion process

A random copolymer based on poly(L ‐lactide) (PLA) with poly(ε‐caprolactone) (PCL) was prepared and characterized by mechanical testing and solid state NMR, compared with a polymer blend. For a monofilament sample consisting of PLA/PCL random copolymer, there were negative correlations between the CL content and the mechanical properties: tensile strength, tensile elastic modulus, flexural rigidity, and flexural hysteresis decreased with increasing CL content. In contrast, the mechanical properties of the polymer blend were only slightly changed by addition of the CL unit. For the random copolymer, the addition of a small amount of CL reduced relaxation times, T₁C and T_1ρH, gradually. The T₁C and T_1ρH values correlated closely with the tensile elastic modulus and the tensile strength, respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Structure,crystallization, and properties of poly(aryl ether ether ketone ketone)s containing meta-phenyl links and their copolymers

Poly(aryl ether ether ketone ketone)s (PEEKK) containing meta-phenyl links and their series of copolymers were synthesized and investigated by both X-ray and differential scanning calorimetry (DSC) methods. Results showed that the heat properties of this kind of copolymer depended greatly on the content of meta-phenyl links in the copolymer system, in which occurred the lowest melting point. Results from X-rays showed that PEEKK containing meta-phenyl links had no (111) crystal face diffraction. These proved that meta-phenyl links had introduced asymmetrical factors, which had produced poor crystal structure and difficulty in crystallization. Even so, the modification of PEEKK by introducing the meta-phenyl links improved the polymer composite performances, e.g., the copolymer M₂, which kept performances close to PEEKK but better than PEEK. DSC results of M₂ showed that its Avrami number (n) was 1.5 and its crystal grew fibrously from isothermal crystallization of the melting state, while for the nonisothermal crystallization from the melting state, n was 4.4 to the spherical crystal growth, and the activation energy (ΔE) of crystallization was 184 kJ/mol, which was less than the ΔE of 296 kJ/mol for PEEKK crystallized from the nonisothermal melting state. When M₂ was isothermally crystallized from the rubber state, its n was 2 to the disklike crystal growth, while its n was 4.6 to the spherulitic crystal growth for the nonisothermal crystallization state of melting. The isothermal crystallization process was different from the nonisothermal process in the crystal nucleation and growth for M₂. © 1996 John Wiley & Sons, Inc.     

Effects of zinc oxide nanoparticles on the physical properties of polyacrylonitrile

Polyacrylonitrile (PAN)/zinc oxide (ZnO) nanocomposites were prepared by solution mixing in dimethylacetamide, followed by film casting, and their physical properties were investigated. The heating scan of differential scanning calorimetry displayed only a single crystallization peak (T_c) without a melting peak, regardless of the presence of ZnO. The incorporation of ZnO nanoparticles decreased T_c by 13°C, and increased the heat of crystallization by 18%. Further, it greatly improved the thermal stability of PAN, even at the ZnO content as low as 0.1 wt %. The nanocomposites showed the UV transmittance peak at 365 nm, whose intensity was increased as ZnO content was increased. The presence of ZnO did not produce new peak nor shift the peaks with respect to PAN in wide angle X‐ray diffraction pattern. Introduction of a small amount of ZnO nanoparticles did not have notable effect on the tensile properties. However, 5 wt % loading of the nanoparticles increased the tensile modulus of PAN by 14.5% and decreased elongation at break dramatically. PAN nanocomposites with 5 wt % ZnO did not show any plateau region in stress–strain curve. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1854–1858, 2006     

Liquid crystallization of poly(styrene‐co‐maleic anhydride) induced by intermolecular hydrogen bonds

The liquid crystallization of general polymer (GP) with maleic anhydride in the main chain has been realized through molecular recognition and self‐assembly based on intermolecular hydrogen bonds. Poly[styrene‐co‐(N‐4‐carboxylphenyl)maleimide] (SMIBA) was synthesized by imidization and dehydration of Poly(styrene‐co‐maleic anhydride) (SMA) with p‐aminobenzoic acid (ABA) for use as an H‐bonded donor polymer. 4‐Methoxy‐4′‐stilbazole (MSZ) and 4‐nitro‐4′‐stilbazole (SZNO₂) were prepared as an H‐bonded acceptor. SMIBA was complexed with MSZ or SZNO₂ by slow evaporation from pyridine solution to form a self‐assembly, which exhibits the mesophase, while neither of the individual components is mesogenic. The phase diagrams of a variety of mixtures between of SMIBA and stilbazoles have been established using DSC and POM. They show complete miscibility and high thermal stability of the liquid crystalline phase over the whole composition range. The tuning of liquid crystalline properties was achieved by changing the composition of the mixture and involving it with a mixture of SZNO₂ and MSZ. IR measurements strongly support the existence of an H‐bonded complex between the carboxylic acid of SMIBA and the pyridine group of stibazoles. Unlike conventional side‐chain liquid crystalline polymer (SLCP), supramolecular SLCP with a lower molecular weigh polymeric donor has higher thermal stability of the liquid crystalline phase due to the microphase separated in the hydrogen bonding case. Liquid crystallization of GP, such as SMA, induced by hydrogen bonds, offers a new route to prepare functional material with controlled molecular architecture from readily accessible and simpler precursors. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 97–105, 1999     

Effect of salt on the elastic modulus of poly(N-isopropylacrylamide) gels

The measurement of tensile modulus of poly(N-isopropylacrylamide) (PNIPA) gel in the solution of NaCl, NaI, LiNO₃ and NaNO₃ was carried out. It was confirmed that the tensile modulus of PNIPA gel in the solution of salt depends on the volume of gel regardless of the kind and concentration of salts. This result leads us to the conclusion that the addition of salt effect only on the mixing contribution to the Flory's type free energy of gel especially in the swollen state. Therefore, our result is in agreement with a recent remarkable discovery that the volume of PNIPA gel depends only on the chemical potential of water in spite of the kind of additives. On the other hand, it was found that on the volume phase transition point and in the deswollen state, the elasticity of PNIPA gel depended on the concentration and kind of the salt because the viscoelasticity emerged due to the shrinkage of polymer network.     

Crystallization kinetics of poly-ε-caprolactone from poly-ε-caprolactone/poly(vinyl chloride) solutions

The polymer–polymer solution of poly(vinyl chloride) and poly-ε-caprolactone yields an excellent system for studying the crystallization kinetics of a crystallizable component from a polymer–polymer solution. Unlike previous studies of isotactic–atactic polystyrene solutions for which the glass transition temperature is invariant with composition, this system exhibits a marked dependence of T_g on the composition. The experimental data dE^?(modulus)/dt (psi^?/min) were obtained over a composition range of 40 to 70 wt-% poly-ε-caprolactone. With the appropriate modification of the spherulitic growth rate equation, the expression approximated a reasonable fit of the experimental data. This demonstrates a marked dependence of the crystallization rate on concentration. Secondary observations of this investigation show a slower crystallization rate for high molecular weight poly-ε-caprolactone and a slow secondary crystallization step. Both homopolymer poly-ε-caprolactone and poly-ε-caprolactone in the poly-ε-caprolactone/poly(vinyl chloride) solution show a slow (relative to the nucleation-controlled step) crystallization stage considered to involve a slow diffusion mechanism.     

Ultra High Modulus Fibers from Solution and Melt Spinning

Abstract

In recent years several methods for developing high strength-high modulus polymers have been reported. Restricting our consideration to the case of fibers, a general requirement for superior tensile properties appears to be a high degree of extended chains and of molecular orientation along the fiber axis. Various methods which have been used for developing ultra high modulus properties are summarized in Table I . The approach for maximizing chain extension and orientation differs depending whether the polymer molecule exhibits a flexible or a rigid conformation. In the case of flexible molecules, one seeks to reduce preformed chain folds, or avoid their formation, while simultaneously increasing the orientation. For samples crystallized under isotropic conditions this may be done by specialized cold drawing or extrusion processes, as reported by Capaccio and Ward, by Porter and co-workers, by Clark, and by others. The highest modulus thus obtained (E ₁₁) is already within a factor three from the theoretical modulus (E _T ). Alternatively, chain extension and orientation may be induced in a strain polymer solution, with the aid of a parallel velocity gradient, followed by crystallization of the oriented material. The approach has been discussed by Keller and co-workers in the case of polyethylene solutions flowing from opposed jets. Recently, Penning and coworkers have been able to grow continuous fibrilar polyethylene from seeded crystallization in a Couette apparatus. They reported the highest modulus so far attained for a polyethylene specimen. The case of melt spinning of flexible polymers is also based on the maximization of chain extension and orientation in a strained melt, followed by crystallization of the oriented material.     

Semi-interpenetrating polymer networks composed of poly(ethylene terephthalate) and vernonia oil

Semi-interpenetrating networks have been synthesized from vernonia oil-sebacic acid polyester network and poly(ethylene terephthalate) (PET). Bond interchange reactions during mixing of the two materials led to the formation of a miscible copolymer mixture, in which the vernonia oil was then cross-linked with sebacic acid. The materials were phase-separated, exhibiting two glass transitions, when the network was synthesized at 160°C, below the crystallization temperature of PET: however, a single stable glass transition (T_g) results after the material is heated to above the melting temperature of PET and cooled. When the vernonia polyester network was completely formed at 250°C, above the crystallization temperature of PET, noncrystalline, single-T_g material was created. The two-phase semi-IPNs were much tougher than were their constituent materials, with the 50% semi-IPN over 15 times tougher than the PET from which it was made and over 50 times tougher than the neat vernonia oil elastomer, with tensile energy to break of 1780 kJ/m³. The single-T_g material was nearly 2.5 times as tough as the two-phase material, with energy to break of 4400 kJ/m³. The microstructure of the two-phase 50% semi-IPN was investigated by transmission electron microscopy, which showed regularly shaped spherulites of 10–20 μm in diameter, as compared to irregularly shaped spherulites observed in a similar 50/50 castor oil urethane/PET semi-IPN, in which the network formed simultaneously with PET crystallization. Scanning electron microscopy of the semi-IPN fracture surfaces showed microscopic fibrils several hundred nanometers in diameter in both the two-phase and single-T_g materials, although only the two-phase semi-IPN had a macroscopically rough surface. © 1993 John Wiley & Sons, Inc.     

Crystallization kinetics of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/clay nanocomposites

The preparation and properties of nanocomposites, consisting of a poly(3‐Hydroxybutyrate‐co‐3‐hydroxyvalerate) and an organophilic clay are described. The effect of organophilic clay on the crystallization behavior of (PHBV) was studied. A differential scanning calorimeter (DSC) was used to monitor the energy of the crystallization process from the melt. During the crystallization process from the melt, the organophilic clay led to an increase in crystallization temperature (T_c) of PHBV compared with that for plain PHBV. During isothermal crystallization, dependence of the relative degree of crystallization on time was described by the Avrami equation. The addition of organophilic clay caused an increase in the overall crystallization rate of PHBV, but did not influence the mechanism of nucleation, and growth of the PHBV crystals and the increase caused by a small quantity of clay is move effective than that large one. The equilibrium melting temperature of PHBV was determined as 186°C. Analysis of kinetic data according to nucleation theories showed that the increase in crystallization rate of PHBV in the composite is due to the decrease in surface energy of the extremity surface. The mechanical test shows that the tensile strength of hybrid increased to 35.6 MPa, which is about 32% higher than that of the original PHBV with the incorporation of 3 wt % clay, and the tensile modulus was also increased. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 655–661, 2004