Preparation,crystallization, and properties of biodegradable poly(butylene adipate‐co‐terephthalate)/organomodified montmorillonite nanocomposites

Intercalated and exfoliated nanocomposites of biodegradable poly(butylene adipate‐co‐terephthalate) (PBAT) and Cloisite 30B (C30B) were fabricated by a solution‐casting method to study the effects of the clay loading on the crystallization behavior, thermal stability, and dynamic mechanical properties of PBAT in PBAT/C30B nanocomposites. X‐ray diffraction and transmission electron microscopy results indicated the formation of exfoliated nanocomposites at low clay loadings (<5 wt %) and a mixture of exfoliated and intercalated nanocomposites with a clay content of 8 wt % throughout the PBAT matrix. Nonisothermal melt crystallization studies indicated that C30B enhanced the crystallization of PBAT, apparently because of a heterogeneous nucleation effect. Moreover, an attempt was made to quantitatively study the influence of the presence of C30B and its contents on the nucleation activity of PBAT in the PBAT/C30B nanocomposites. The thermal stability of PBAT decreased slightly in the nanocomposites. However, the storage modulus of PBAT apparently increased with the C30B loading increasing in the PBAT/C30B nanocomposites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Biodegradable poly(L‐lactic acid)/poly(butylene succinate‐co‐adipate) blends: Miscibility,morphology, and thermal behavior

Blends of two biodegradable and semicrystalline polymers, poly(L ‐lactic acid) (PLLA) and poly(butylene succinate‐co‐adipate) (PBSA), were prepared by solvent casting in different compositions. The miscibility, morphology, and thermal behavior of the blends were investigated using differential scanning calorimetry and optical microscopy. PLLA was found to be immiscible with PBSA as evidenced by two independent glass transitions and biphasic melt. Nonisothermal crystallization measurements showed that fractionated crystallization behavior occurred when PBSA was dispersed as droplets, evidenced by multiple crystallization peaks at different supercooling levels. Crystallization and morphology of the blends were also investigated through two‐step isothermal crystallization. For blends where PLLA was the major component, different content of PBSA did not make a significant difference in the crystallization mechanism and rate of PLLA. For blends where PBSA was the major component, the crystallization rate of PBSA decreased with increasing PLLA content, while the crystallization mechanism did not change. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Miscibility and crystallization behaviors of biodegradable poly(butylene succinate‐co‐butylene terephthalate)/phenoxy blends

Miscibility and crystallization behaviors of biodegradable poly(butylene succinate‐co‐butylene terephthalate) (PBST)/poly(hydroxyl ether biphenyl A) (phenoxy) blends were investigated with various techniques in this work. PBST and phenoxy are completely miscible as evidenced by the single composition‐dependent glass transition temperature over the entire blend compositions. Nonisothermal melt crystallization peak temperature is higher in neat PBST than in the blends at a given cooling rate. Isothermal melt crystallization kinetics of neat and blended PBST was studied and analyzed by the Avrami equation. The overall crystallization rate of PBST decreases with increasing crystallization temperature and the phenoxy content in the PBST/phenoxy blends; however, the crystallization mechanism of PBST does not change. Moreover, blending with phenoxy does not modify the crystal structure but reduces the crystallinity degree of PBST in the PBST/phenoxy blends. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Multiwalled carbon nanotube nucleated crystallization behavior of biodegradable poly(butylene succinate) nanocomposites

Poly(butylene succinate) (PBS) nanocomposites with multiwalled carbon nanotubes (MWNTs) prepared by melt compounding were studied for the effect of MWNT dispersion on the modulus and crystallization kinetics. The nucleating effect of the addition of 0.1 wt % MWNT to PBS was clearly demonstrated. Differential scanning calorimetry nonisothermal crystallization studies showed a clear decrease in the half‐time of crystallization with increasing MWNT content in PBS/MWNT nanocomposites. It was observed with the Ozawa method that the Ozawa parameter values for the nanocomposites were lower than those for neat PBS, and this indicated that the crystal morphology was different. The storage modulus of the nanocomposites increased about 23% with the addition of only 0.1% MWNT in comparison with neat PBS, whereas the glass‐transition temperature was unaltered. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Biodegradable poly (butylene succinate‐co‐cyclohexanedimethylene succinate): Synthesis,crystallization, morphology,and rheology

Poly (butylene succinate‐co‐cyclohexanedimethylene succinate) (PBCSs), which are composed of various amounts of cyclohexanedimethylene succinate (CS) with butylene succinate (BS) were synthesized via polycondensation. The composition of PBCSs was analyzed by a ¹H‐nuclear magnetic resonance (¹H‐NMR). Crystallization, morphology, and rheological properties of PBCSs were investigated by a polarized optical microscopy (POM), a differential scanning calorimetry (DSC), a X‐ray diffraction (XRD), and a parallel‐plate rheometer (PPR). The studies revealed that the composition of PBCSs played an important role in controlling their properties. Only one T_g can be seen for PBCSs by DSC, which demonstrate they are miscible copolymers. PBCSs exhibited lower crystallization capacity than its homopolyesters either Poly (butylene succinate) (PBS) or poly (cyclohexanedimethylene succinate) (PCS). It also proved that the cyclohexyl group of CHDM not only affected the crystalline formation, but also changed spherulitic morphology during crystallization. The spherulitic size gradually decreased with an increase of CS content. When CS content approached 50 wt %, the crystallization ability reached minimum. By comparing the effect of temperature with shear rate, it concluded that the viscosities of PBCSs were more sensitive to temperature rather than shear rate, and flow activation energies of PBCSs linearly increased with an increase of CS content. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40103.     

Elongational rheology of biodegradable poly(lactic acid)/poly[(butylene succinate)‐co‐adipate] binary blends and poly(lactic acid)/poly[(butylene succinate)‐co‐adipate]/clay ternary nanocomposites

A series of blends based on poly(lactic acid) (PLA) and poly[(butylene succinate)‐co‐adipate] (PBSA) as well as their nanocomposites with nanoclay (PLA/PBSA/Clay ternary nanocomposites) were prepared using the twin‐screw extruder. The blends were prepared for PBSA contents ranging from 25 to 75 wt % and their corresponding nanocomposites were prepared at a single‐clay concentration. The morphology and structure of the blends and the nanocomposites were examined using field emission scanning electron microscopy, transmission electron microscopy, and X‐ray diffraction. Rheological properties (dynamic oscillatory shear measurements and elongational viscosities) of the blends, nanocomposites, and pure components were studied in detail. The strain hardening intensity of different blends and nanocomposites was compared with the behavior of the pure components. Strong strain hardening behavior was observed for blends composed of 50 wt % and higher PBSA content. However, the effect of PBSA content on the elongational viscosity was less pronounced in PLA/PBSA/Clay ternary nanocomposites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Biodegradation of poly(butylene adipate‐co‐butylene terephthalate)/layered‐silicate nanocomposites

The biodegradability of poly(butylene adipate‐co‐butylene terephthalate) (PBAT) and PBAT/starch composites with layered silicates prepared by melt intercalation was evaluated with aerobic biodegradability tests in soil and in an aqueous medium containing activated sludge. Nonmodified montmorillonite (MMT) and octadecylamine‐modified montmorillonite (ODA‐M), known to give a microcomposite and an intercalated nanocomposite for PBAT, respectively, were used as layered silicates. After they were buried in the soil for 8 months, the PBAT/MMT microcomposite exhibited a higher weight loss than the control PBAT, whereas the PBAT/ODA‐M nanocomposite showed a lower weight loss instead. Also, the biodegradability test in the aqueous medium, by determining the biochemical oxygen demand, showed that the addition of MMT and/or starch to PBAT promoted biodegradation, whereas the addition of ODA‐M did not. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Morphology,mechanical properties,and thermal stability of poly(L‐lactic acid)/poly(butylene succinate‐co‐adipate)/silicon dioxide composites

Poly(butylene succinate‐co‐adipate) (PBSA) and two types of SiO₂ (hydrophilic or hydrophobic) were used to modify poly(L ‐lactic acid) (PLLA). The mechanical properties, rheological and thermal behavior, phase morphology, and thermal stability of PLLA/PBSA/SiO₂ composites were investigated. The impact strength, flexural strength, and modulus of PLLA/PBSA blends increased after the addition of hydrophobic SiO₂ without decreasing the elongation at break, and the elongation at break monotonically decreased with increasing hydrophilic SiO₂ content. The melt elasticity and viscosity of the PLLA/PBSA blend increased with the addition of SiO₂. The hydrophilic SiO₂ was encapsulated by the dispersed PBSA phase in the composites, which led to the formation of a core–shell structure, whereas the hydrophobic SiO₂ was more uniformly dispersed and mainly located in the PLLA matrix, which was desirable for the optimum reinforcement of the PLLA/PBSA blend. The thermogravimetric analysis results show that the addition of the two types of SiO₂ increased the initial decomposition temperature and activation energy and consequently retarded the thermal degradation of PLLA/PBSA. The retardation of degradation was prominent with the addition of hydrophobic SiO₂. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Enhanced mechanical and thermal properties of biodegradable poly(butylene succinate‐co‐adipate)/graphene oxide nanocomposites via in situ polymerization

Poly(butylene succinate‐co‐butylene adipate) (PBSA)/graphene oxide (GO) nanocomposites were synthesized via in situ polymerization for the first time. Atomic force microscopy demonstrated the achievement of a single layer of GO, and transmission electron microscopy proved the homogeneous distribution of GO in the PBSA matrix. Fourier transform infrared spectroscopy results showed the successful grafting of PBSA chains onto GO. With the incorporation of 1 wt % GO, the tensile strength and flexural modulus of the PBSA were enhanced by 50 and 27%, respectively. The thermal properties characterized by differential scanning calorimetry and thermogravimetric analysis showed increases in the melting temperatures, crystallization temperatures, and thermal stability. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4075–4080, 2013     

Preparation and characterization of poly(hydroxybutyrate‐co‐hydroxyvalerate)–organoclay nanocomposites

This study describes the microstructure and thermal and mechanical properties of poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHB/HV)–organoclay nanocomposites prepared by melt intercalation using Cloisite 30B, a monotallow bis‐hydroxyethyl ammonium‐modified montmorillonite clay. X‐ray diffractometry and transmission electron microscopy analyses clearly confirm that an intercalated microstructure is formed and finely distributed in the PHB/HV copolymer matrix because PHB/HV has a strong hydrogen bond interaction with the hydroxyl group in the organic modifier of Cloisite 30B. The nanodispersed organoclay also acts a nucleating agent, increasing the temperature and rate of crystallization of PHB/HV; therefore, the thermal stability and tensile properties of the organoclay‐based nanocomposites are enhanced. These results confirm that the organoclay nanocomposite greatly improves the material properties of PHB/HV. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 525–529, 2003     

Isothermal crystallization of poly(ethylene‐co‐glycidyl methacrylate)/clay nanocomposites

Poly(ethylene‐co‐glycidyl methacrylate) (PEGMA)/clay nanocomposites with clay concentrations of 1, 3, or 5 wt % were prepared via y melt blending in a twin‐screw extruder. Wide‐angle X‐ray diffraction showed that the clay layers were intercalated by PEGMA. Differential scanning calorimetry was used to analyze the isothermal crystallization, and the equilibrium melting temperature was determined with the Hoffman–Weeks method. The Avrami, Tobin, Malkin, and Urbanovici–Segal models were applied to describe the kinetics of crystallization from the melt state under isothermal conditions. The crystallization kinetics showed that the addition of clay facilitated the crystallization of PEGMA, with the clay functioning as a heterophase nucleating agent; at higher concentrations, however, the physical hindrance of the clay layers to the motion of PEGMA chains retarded the crystallization process. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1051–1064, 2005     

Nonisothermal crystallization kinetics of poly(butylene terephthalate)/montmorillonite nanocomposites

The melt intercalation method was employed to prepare poly(butylene terephthalate) (PBT)/montmorillonite (MMT) nanocomposites, and the microstructures were characterized with X‐ray diffraction and transmission electron microscopy. Then, the nonisothermal crystallization behavior of the nanocomposites was studied with differential scanning calorimetry (DSC). The DSC results showed that the exothermic peaks for the nanocomposites distinctly shifted to lower temperatures at various cooling rates in comparison with that for pure PBT, and with increasing MMT content, the peak crystallization temperature of the PBT/MMT hybrids declined gradually. The nonisothermal crystallization kinetics were analyzed by the Avrami, Jeziorny, Ozawa, and Mo methods on the basis of the DSC data. The results revealed that very small amounts of clay (1 wt %) could accelerate the crystallization process, whereas higher clay loadings reduced the rate of crystallization. In addition, the activation energy for the transport of the macromolecular segments to the growing surface was determined by the Kissinger method. The results clearly indicated that the hybrids with small amounts of clay presented lower activation energy than PBT, whereas those with higher clay loadings showed higher activation energy. The MMT content and the crystallization conditions as well as the nature of the matrix itself affected the crystallization behavior of the hybrids. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3257–3265, 2006     

Biodegradable composites of poly(butylene succinate‐co‐butylene adipate) reinforced by poly(lactic acid) fibers

Biodegradable composites of poly(butylene succinate‐co‐butylene adipate) (PBSA) reinforced by poly(lactic acid) (PLA) fibers were developed by hot compression and characterized by Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), dynamic mechanical analyzer, and tensile testing. The results show that PBSA and PLA are immiscible, but their interface can be improved by processing conditions. In particular, their interface and the resulting mechanical properties strongly depend on processing temperature. When the temperature is below 120 °C, the bound between PBSA and PLA fiber is weak, which results in lower tensile modulus and strength. When the processing temperature is higher (greater than 160 °C), the relaxation of polymer chain destroyed the molecular orientation microstructure of the PLA fiber, which results in weakening mechanical properties of the fiber then weakening reinforcement function. Both tensile modulus and strength of the composites increased significantly, in particular for the materials reinforced by long fiber. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43530.     

Antimicrobial activity and biodegradation behavior of poly(butylene adipate‐co‐terephthalate)/clay nanocomposites

Poly(butylene adipate‐co‐terephthalate) (PBAT) nanocomposites films are prepared by a solution intercalation process using natural montmorillonite (MMT) and cetyltrimethylammonium bromide (CTAB)‐modified montmorillonite (CMMT). Cation exchange technique has been used for modification of MMT by CTAB and characterized by Fourier transform infrared analysis, thermo‐gravimetric analysis, and X‐ray diffraction (XRD) studies. CMMT gives better dispersion in the PBAT matrix than MMT and is confirmed by XRD and transmission electron microscopy. Because of better compatibility of CMMT, water vapor transmission rate of PBAT decreases more in the presence of CMMT than MMT. The biodegradability of PBAT and its nanocomposite films are studied in compost and from the morphological analysis it is apparent that the PBAT/CMMT shows a lower biodegradation rate in comparison to the PBAT/MMT. The antimicrobial activity of PBAT and its nanocomposite films is tested by an inhibition zone method. Because of the presence of the quaternary ammonium group of CTAB‐modified MMT, PBAT/CMMT nanocomposites show adequate antimicrobial activity. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40079.     

Dielectric spectroscopy of poly(butylene succinate‐co‐butylene adipate) films

The results of dielectric studies in semicrystalline poly (butylene succinate‐co‐butylene adipate) (PBSA) by means of dielectric relaxation spectroscopy from 163 to 353 K and in the frequency range of 0.056–17,800 Hz are reported. The subglass β process is found to follow an Arrhenius temperature dependence, whereas the segmental α process follows a Vogel–Fulcher–Tammann temperature dependence. The higher temperature Maxwell–Wagner–Sillars (MWS) process was studied by applying the Bruggeman‐Hanai equation, which helped to understand the underlying relaxation dynamics. The MWS process originates from the charge accumulation at the interface between the low‐conductivity continuous medium and the high‐conductivity dispersed particles. A three‐phase model in which the medium comprises the crystalline and rigid amorphous phases (RAPs) and the particle comprises solely the mobile amorphous phases (MAPs) is required to explain the particle fraction variation with temperature. With increasing temperature, the MAP fraction increases at the expense of the RAP fraction within the continuous medium. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers.     

Crystallization behavior of fully biodegradable poly(lactic acid)/poly(butylene adipate‐co‐terephthalate) blends

Both poly(lactic acid) (PLA) and poly(butylene adipate‐co‐terephthalate) (PBAT) are fully biodegradable polyesters. The disadvantages of poor mechanical properties of PLA limit its wide application. Fully biodegradable polymer blends were prepared by blending PLA with PBAT. Crystallization behavior of neat and blended PLA was investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and wide angle X‐ray diffraction (WAXD). Experiment results indicated that in comparison with neat PLA, the degree of crystallinity of PLA in various blends all markedly was increased, and the crystallization mechanism almost did not change. The equilibrium melting point of PLA initially decreased with the increase of PBAT content and then increased when PBAT content in the blends was 60 wt % compared to neat PLA. In the case of the isothermal crystallization of neat PLA and its blends at the temperature range of 123–142°C, neat PLA and its blends exhibited bell shape curves for the growth rates, and the maximum crystallization rate of neat PLA and its blends all depended on crystallization temperature and their component. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Thermal properties and degradation behavior of poly(1,4‐butylene adipate)/modified layered double hydroxide nanocomposites

In this study, poly(1,4‐butylene adipate) (PBA)/organomodified layered double hydroxide (m‐LDH) nanocomposites were synthesized and characterized as a new material for green materials use. m‐LDH was initially prepared with magnesium nitrate hexahydrate, aluminum nitrate‐9‐hydrate, oleic acid, and sorbitol by a novel one‐step coprecipitation method to intercalate the oleic acid and sorbitol organomodifier into the interlayer of the layered double hydroxide. The solution mixing process was then applied and shown to be an efficient method for fabricating the PBA/m‐LDH nanocomposites. The m‐LDH characterized by X‐ray diffraction (XRD) showed a high interlayer spacing of 58.8 Å. The morphology and thermal properties of the PBA/m‐LDH nanocomposites were characterized with XRD, transmission electron microscopy, and thermogravimetric analysis. It was shown that the m‐LDH was well distributed in the PBA matrix and that the thermal properties of the PBA/m‐LDH nanocomposites significantly improved with a loading of 0.1 wt % m‐LDH. Finally, the biodegradability of the PBA/m‐LDH nanocomposites was tested with lipase from Pseudomonas fluorescens as a microbial catalyst. It was shown that an addition of m‐LDH up to 0.5% resulted in a significant difference in terms of the biodegradability. After 120 h of degradation, the residual weight and surface morphology of the composite films were affected by the presence of m‐LDH. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42083.     

Pressure‐volume‐temperature behavior of polylactide,poly(butylene succinate), and poly(butylene succinate‐co‐adipate)

Pressure‐Volume‐Temperature (PVT) behavior of three biodegradable polymers, Polylactide, poly(butylene succinate), and poly(butylene succinate‐co‐adipate), was measured at temperatures from 313 to 493 K and pressures up to 200 MPa. The PVF data in molten state were compared with predicted values of a group contribution modified cell model equation of state (GCMCM EOS). It was found that the GCMCM EOS coupled with one specific volume datum at atmospheric pressure could predict the PVT of the polymer melts to within 0.46% in an average relative deviation of specific volume.     

Crystallization behavior of poly(L‐lactic acid)/montmorillonite nanocomposites

In this study, we modified montmorillonite (MMT) with dilauryl dimethyl ammonium bromide (DDAB) and then exfoliated the structures in a poly(L ‐lactic acid) (PLLA) matrix. We used polar optical microscopy and X‐ray diffraction (XRD) to examine the morphologies of the resulting composites, differential scanning calorimetry to study the melting and crystallization behavior, and Fourier transform infrared (FTIR) and Raman spectroscopy to measure the influence of the intermolecular interactions between PLLA and MMT on the isothermal crystallization temperature. We found that the DDAB‐modified MMT was distributed uniformly in the PLLA matrix. At temperatures ranging from 130 to 140°C, the crystalline morphology resembled smaller Maltese cross‐patterned crystallites; at temperatures from 150 to 170°C, however, the number of crystallites decreased, their sizes increased, and they possessed ringed spherulite structures. In the XRD spectra, the intensity of the diffraction peaks of the 200/110 and 203 facets of the PLLA/MMT nanocomposites decreased as the crystallization temperature increased. In the FTIR spectra, the absorption peak of the C?O groups split into two signals at 1748 and 1755 cm^?1 when the isothermal crystallization temperature was higher than 140°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Polymorphism and spherulite morphology of poly(1,4‐butylene adipate)/organically‐modified layered double hydroxide nanocomposites

A novel biodegradable poly(1,4‐butylene adipate)/organically‐modified layered double hydroxide (PBA/m‐LDH) nanocomposites are synthesized using the solution mixing process. The m‐LDH is originally prepared with magnesium nitrate hexahydrote (Mg(NO₃)₂ 6H₂O), aluminum nitrate‐9‐hydrate (Al(NO₃)₃ 9H₂O), oleic acid, and sorbitol by a novel one‐step co‐precipitation method to intercalate the organo‐modifier of oleic acid and sorbitol into the interlayer of LDH. The structure and morphology of the PBA/m‐LDH nanocomposites are characterized using X‐ray diffraction and transmission electron microscopy (TEM). It has been shown that the m‐LDH is exfoliated and well distributed in PBA matrix. The effect of m‐LDH on the polymorphic crystal and morphology of PBA at various crystallization temperatures (T_cs) would be investigated using WAXD and POM. Both data indicate that the addition of m‐LDH can change the starting formation temperature of α‐form crystals. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42526.