Morphology and hydrogen‐bond restricted crystallization of poly(butylene succinate)/cellulose diacetate blends

Poly(butylene succinate)/cellulose diacetate (PBS/CDA) blends were prepared by the solution blending method from poly(butylene succinate) (PBS) and cellulose diacetate (CDA). The influence of hydrogen bond on the structure, morphology, crystallization, as well as the physical properties of PBS/CDA blends was significantly investigated. The fourier transform infrared spectroscopy (FTIR) results indicated that the carbonyl groups of PBS shifted to higher wavenumbers and disappeared at the content of 60% CDA, due to the formation of hydrogen bond between PBS and CDA. The wide‐angle X‐ray diffractometer (WAXD) and differential scanning calorimeter (DSC) analysis suggest that the crystallization of PBS was significantly restricted by the incorporation of CDA, which is also attributed to the hydrogen bonding. The scanning electron miscroscope (SEM) and polarized optical microscopy (POM) results revealed that PBS and CDA were miscible without appearance of obvious phase separation. The hydrogen bonding interaction led to the change of decomposing mechanism of blends as determined by thermogravimetric analysis (TGA), as well as the increase of the elongation at break due to the reduced crystallinity of PBS. The existence of CDA led to the decrease of water contact angle, showing of the improved hydrophilicity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Structure and physical properties of cellulose acetate/poly(butylene succinate) blends containing a transition metal alkoxide

Two biodegradable polymers, that is, poly(butylene succinate) (BN) and cellulose acetate (CA), were solvent‐cast blended with chloroform. Homogeneous films were obtained from the blend by the addition of tetraisopropyl titanate (TP) as a compatibilizer. We measured the viscosity of the blend solution to investigate the function of TP during the blending process. From the measurement, we conclude that there are interactions among TP, BN, and CA. From optical observation and thermal measurements of the blend films, we found that the structure of blends is in a pseudostable state and that the addition of TP makes the structure units small. From thermogravimetric analyses, we found that the addition of TP decreases the thermal decomposition temperature of the BN/CA blends. From the measurements of mechanical properties of the blends, we found that changing the blend ratio can produce the materials with a wide range of mechanical properties. The hydrolysis of the blends was investigated. The molecular scission of BN/CA blends takes place uniformly not only from the outside but also from the inside of the films. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1750–1758, 2002     

Crystallization behaviour of poly(butylene succinate) copolymers

Poly(butylene succinate‐co‐butylene 2‐methyl succinate) (PBSMS) random copolymers were synthesized with various comonomer compositions and their crystallization behaviour and morphology were investigated by differential scanning calorimeter, small angle X‐ray scattering and polarized optical microscopy. The equilibrium melting temperature obtained by the Hoffman–Weeks plot significantly decreased with increasing comonomer concentration containing methyl side‐groups. Spherulitic growth rates were strongly dependent on comonomer concentration and were analyzed using the Lauritzen–Hoffman kinetic theory. The surface free energy (σσ_e) dramatically decreased with comonomer contents. From analysis of the SAXS data, the dependence of the lamellar thickness on crystallization temperature decreased with increasing comonomer concentration. © 2002 Society of Chemical Industry     

Crystallization kinetics,melting behavior,and morphologies of poly(butylene succinate) and poly(butylene succinate)‐block‐poly(propylene glycol) segmented copolyester

This article investigated the crystallization kinetics, melting behavior, and morphologies of poly(butylene succinate)(PBS) and its segmented copolyester poly(butylene succinate)‐block‐poly(propylene glycol)(PBSP) by means of differential scanning calorimetry, polarized light microscopy, and wide angle X‐ray diffraction. Avrami equation was used to describe the isothermal crystallization kinetics. For nonisothermal crystallization studies, the Avrami equation modified by Jeziorny, and the model combining Avrami equation and Ozawa equation were employed. The results showed that the introduction of poly(propylene glycol) soft segment led to suppression of crystallization of PBS hard segment. The melting behavior of the isothermally and nonisothermally crystallized samples was also studied. Results showed that the isothermally crystallized samples exhibited two melting endotherms, whereas only one melting endotherm was shown after nonisothermal crystallization. The spherulitic morphology of PBSP and wide angle X‐ray diffraction showed that the polyether segments were excluded from the crystals and resided in between crystalline PBS lamellae and mixed with amorphous PBS. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Crystallization kinetics of poly(ethylene terephthalate)/poly(ethylene 2,6‐naphthalate) blends

The crystallization kinetics of poly(ethylene terephthalate)/poly(ethylene 2,6‐naphthalate) (PET/PEN) blends were investigated by DSC as functions of crystallization temperature, blend composition, and PET and PEN source. Isothermal crystallization kinetics were evaluated in terms of the Avrami equation. The Avrami exponent (n) is different for PET, PEN, and the blends, indicating different crystallization mechanisms occurring in blends than those in pure PET and PEN. Activation energies of crystallization were calculated from the rate constants, using an Arrhenius‐type expression. Regime theory was used to elucidate the crystallization course of PET/PEN blends as well as that of unblended PET and PEN. The transition from regime II to regime III was clearly observed for each blend sample as the crystallization temperature was decreased. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 23–37, 2001     

Crystallization behavior of partially crosslinked poly(β‐hydroxyalkonates)/poly(butylene succinate) blends

Partially crosslinked poly(β‐hydroxybutyrate‐co‐β‐hydroxyvalerate)/poly(butylene succinate) (PHBV/PBS) and poly(β‐hydroxybutyrate)/poly(butylene succinate) (PHB/PBS) blends were prepared by melt compounding with dicumyl peroxide. The effect of partial crosslinking on crystallization of the PHBV/PBS and PHB/PBS blends was investigated systematically. Differential scanning calorimetry results showed that the overall crystallization rates of both PHBV and PBS in their blends were enhanced considerably by the partial crosslinking. Similar results were also detected in the PHB/PBS blends. The polarized optical microscope observation displayed that the nuclei density of PHBV was increased while the spherulitic morphology did not change much. Conversely, the PBS spherulites turned into cloud‐like morphology after the partial crosslinking which is a result of the decrease in spherulite size, the reduction in interspherulite distance and the interconnection of fine PBS domains. Wide angle X‐ray diffraction patterns confirmed the enhancement in crystallization of the PHBV/PBS blends after the partial crosslinking without modification on crystalline forms of the PHBV and PBS components. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41020.     

聚丁二酸丁二醇酯的等温结晶动力学研究

采用差示扫描量热仪(DSC)对聚丁二酸丁二醇酯(PBS)的等温结晶动力学进行了研究,并用Avrami方程对实验数据进行了量化分析。研究结果表明:在等温结晶时,PBS倾向于以均相成核的三维生长方式结晶,并通过偏光显微镜进行了验证;同时,随着结晶温度的升高,PBS的结晶速率常数K值下降,半结晶时间t1/2延长。     

Nonisothermal crystallization behavior of poly (butylene terephthalate)–poly (ethylene terephthalate‐co‐isophthalate‐co‐sebacate) segmented copolyesters

In this paper, two different analytical methods were applied to investigate nonisothermal crystallization behavior of copolyesters prepared by melting transesterification processing from bulk polyesters involving poly (butylene terephthalate) (PBT) and ternary amorphous random copolyester poly(ethylene terephthalate‐co‐isophthalate‐co‐sebacate) (PETIS). The results show that the half‐time of crystallization of copolyesters depended on the reaction time and decreased with the content of ternary polyesters in the amorphous segment. The modified Avrami model describes the nonisothermal crystallization kinetics very well. The values of the Avrami exponent range from 2.2503 to 3.7632, and the crystallization kinetics constant ranges from 0.0690 to 0.9358, presenting a mechanism of three‐dimensional spherulitic growth with heterogeneous nucleation. Ozawa analysis, however, failed to describe the nonisothermal crystallization behavior of copolyesters, especially at higher cooling rate. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1232–1238, 2003     

Modeling of flow‐induced crystallization in blends of isotactic polypropylene and poly(ethylene‐co‐octene)

Poly(ethylene‐co‐octene) (PEOc) has been shown to provide a high toughening contribution to isotactic polypropylene (iPP). The theoretical modeling of flow‐induced crystallization (FIC) of blends of iPP and PEOc is not much reported in the literature. The aim of the present work is to clarify the FIC of iPP upon addition of PEOc in terms of theoretical modeling. The crystallization of iPP and PEOc blends in flow is simulated by a modified FIC model based on the conformation tensor theory. Two kinds of flow fields, shear flow and elongational flow, are considered in the prediction to analyze the influence of flow field on the crystallization kinetics of the polymer. The simulation results show that the elongation flow is much more effective than shear flow in reducing the dimensionless induction time of polymer crystallization. In addition, the induction time of crystallization in the blends is sensitive to the change of shear rate. In comparison with experimental data, the modified model shows its validity for the prediction of the induction time of crystallization of iPP in the blends. Moreover, the simulated relaxation time for the blends becomes longer with increasing percentage of PEOc in the blends. Copyright © 2012 Society of Chemical Industry     

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     

Crystallization and melting behavior of biodegradable poly(ethylene succinate‐co‐6 mol % butylene succinate)

The crystallization, melting behavior, and spherulitic growth kinetics of biodegradable poly(ethylene succinate‐co‐6 mol % butylene succinate) [P(ES‐co‐6 mol % BS)] were investigated and compared with those of the homopolymer poly(ethylene succinate) (PES) in this work. The crystal structure of P(ES‐co‐6 mol % BS) was the same as that of neat PES, but the crystallinity decreased slightly because of the incorporation of the butylene succinate content. The glass‐transition temperature decreased slightly for P(ES‐co‐6 mol % BS) compared to that for neat PES. The melting point of P(ES‐co‐6 mol % BS) decreased apparently; moreover, the equilibrium melting point was also reduced. Two melting endotherms were found for P(ES‐co‐6 mol % BS) after isothermal crystallization; this was ascribed to the melting, recrystallization, and remelting mechanism. The spherulitic growth rate of P(ES‐co‐6 mol % BS) was slower than that of neat PES at a given crystallization temperature. Both neat PES and P(ES‐co‐6 mol % BS) exhibited a crystallization regime II to III transition; moreover, the crystallization regime transition temperature of P(ES‐co‐6 mol % BS) shifted to a low temperature compared with that of neat PES. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Miscibility,crystallization, and mechanical properties of poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate)/ poly(butylene succinate) blends

Naturally amorphous biopolyester poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) (P3/4HB) containing 21 mol % of 4HB was blended with semi‐crystal poly(butylene succinate) (PBS) with an aim to improve the properties of aliphatic polyesters. The effect of PBS contents on miscibility, thermal properties, crystallization kinetics, and mechanical property of the blends was evaluated by DSC, TGA, FTIR, wide‐angle X‐ray diffractometer (WAXD), Scanning Electron Microscope (SEM), and universal material testing machine. The thermal stability of P3/4HB was enhanced by blending with PBS. When PBS content is less than 30 wt %, the two polymers show better miscibility and their crystallization trend was enhanced by each other. The optimum mechanical properties were observed at the 5–10 wt % PBS blends. However, when the PBS content is more than 30 wt %, phase inversion happened. And the two polymers give lower miscibility and poor mechanical properties. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Peroxide modification of poly(butylene adipate‐co‐succinate)

We attempted to introduce crosslinking into poly(butylene adipate‐co‐succinate) (PBAS) to improve the properties, such as the mechanical strength and elasticity, by a simple addition of dicumyl peroxide (DCP). Prior to curing, the thermal stability of PBAS was investigated. Above 170°C PBAS was severely degraded, and the degradation could not be successfully stabilized by an antioxidant. The PBAS was effectively crosslinked by DCP, and the gel fraction increased as the DCP content increased. A major structure of the crosslinked PBAS was an ester and aliphatic group. The tensile strength and elongation of PBAS were improved with an increasing content of DCP, but there was little affect on the tear strength. The biodegradability of crosslinked PBAS was not seriously deteriorated. A higher degree of crosslinking gave a lower heat of crystallization and heat of fusion. However, the melt crystallization temperatures of the crosslinked PBAS were higher than that of PBAS. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 637–645, 2001     

Crystallization and melting properties of poly(butylene succinate) composites with titanium dioxide nanotubes or hydroxyapatite nanorods

Poly (butylene succinate) (PBS) nanocomposites with titanium dioxide nanotubes (TNTs) or hydroxyapatite nanorods (HAP) were prepared, and the effect of the nano‐inorganics on the nonisothermal crystallization and melting properties of PBS were studied in detail by differential scanning calorimeter. The nonisothermal crystallization kinetics of PBS and its nanocomposites were analyzed by the Avrami, Ozawa, and Mo methods. It is found that the presence of TNTs increases the crystallization temperature and rate of PBS composites, but decreases the crystallization activation energy and crystallinity. By comparison, the crystallization rate of the PBS composite is decreased with the addition of HAP. The melting, recrystallization, and remelting mechanism results in the formation of two melting endothermic peaks during the melting process of neat PBS and its nanocomposites. The model proposed by Mo could successfully describe the nonisothermal crystallization process of PBS and its nanocomposites. At a given crystallinity, the F(t) values decrease in the order of PBS/HAP, PBS, and PBS/TNTs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40335.     

Compatible and crystallization properties of poly(lactic acid)/poly(butylene adipate‐co‐terephthalate) blends

Differential scanning calorimetry (DSC), wide angle X‐ray diffraction (WAXD) and dynamic mechanical analysis (DMA) properties of poly(lactic acid)/ poly(butylene adipate‐co‐terephthalate) (PLA/PBAT) specimens suggest that only small amounts of poor PLA and/or PBAT crystals are present in their corresponding melt crystallized specimens. In fact, the percentage crystallinity, peak melting temperature and onset re‐crystallization temperature values of PLA/PBAT specimens reduce gradually as their PBAT contents increase. However, the glass transition temperatures of PLA molecules found by DSC and DMA analysis reduce to the minimum value as the PBAT contents of PLA_xPBAT_y specimens reach 2.5 wt %. Further morphological and DMA analysis of PLA/PBAT specimens reveal that PBAT molecules are miscible with PLA molecules at PBAT contents equal to or less than 2.5 wt %, since no distinguished phase‐separated PBAT droplets and tan δ transitions were found on fracture surfaces and tan δ curves of PLA/PBAT specimens, respectively. In contrast to PLA, the PBAT specimen exhibits highly deformable properties. After blending proper amounts of PBAT in PLA, the inherent brittle deformation behavior of PLA was successfully improved. Possible reasons accounting for these interesting crystallization, compatible and tensile properties of PLA/PBAT specimens are proposed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Nonisothermal crystallization behaviors of biodegradable double crystalline poly(butylene succinate)‐poly(ethylene glycol) multiblock copolymers

Nonisothermal crystallization behaviors of both poly(butylene succinate) (PBS) and poly(ethylene glycol) (PEG) segments within PBS‐PEG (PBSEG) multiblock copolymers were investigated by differential scanning calorimetry (DSC). The nonisothermal crystallization kinetics of both PBS and PEG segments were analyzed by Avrami, Ozawa, and Mo methods. The results showed that both of Avrami and Mo methods were successful to describe the nonisothermal crystallization kinetics of PBS and PEG segments. The results of crystallization kinetics indicated that the crystallization rate of PBS segment decreased with PBS segment content and/or L_PBS, while that of PEG segment decreased with M_n,PEG or F_PEG. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40940.     

Poly(vinyl pyrrolidone‐co‐vinyl acetate)‐graft‐poly(ε‐caprolactone) as a compatibilizer for cellulose acetate/poly(ε‐caprolactone) blends

Poly(vinyl pyrrolidone‐co‐vinyl acetate)‐graft‐poly(ε‐caprolactone) (PVPVAc‐g‐PCL) was synthesized by radical copolymerization of N‐vinyl‐2‐pyrrolidone (VP)/vinyl acetate (VAc) comonomer and PCL macromonomer containing a reactive 2‐hydroxyethyl methacrylate terminal. The graft copolymer was designed in order to improve the interfacial adhesiveness of an immiscible blend system composed of cellulose acetate/poly(ε‐caprolactone) (CA/PCL). Adequate selections of preparation conditions led to successful acquisition of a series of graft copolymer samples with different values of molecular weight ( ), number of grafts (n), and segmental molecular weight of PVPVAc between adjacent grafts (M_n (between grafts)). Differential scanning calorimetry measurements gave a still immiscible indication for all of the ternary blends of CA/PCL/PVPVAc‐g‐PCL (72 : 18 : 10 in weight) that were prepared by using any of the copolymer samples as a compatibilizer. However, the incorporation enabled the CA/PCL (4 : 1) blend to be easily melt‐molded to give a visually homogeneous film sheet. This compatibilizing effect was found to be drastically enhanced when PVPVAc‐g‐PCLs of higher and M_n (between grafts) and lower n were employed. Scanning electron microscopy revealed that a uniform dispersion of the respective ingredients in the ternary blends was attainable with an assurance of the mixing scale of several hundreds of nanometers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Modified polyacrylonitrile blends with cellulose acetate: Fibers' properties

Fiber forming polyacrylonitriles (PAN) were modified by copolymerizing acrylonitrile monomer with methyl acrylate (MA) and 2-acrylamido-2-methyl propane sulfonic acid (AP), respectively, and blended with collulose acetate (CA). Fibers of MA-PAN, AP-PAN, and their blends with CA were wet-spun in dimethylformamide in a broad range of coagulation bath concentrations (CBC). The effects of hydrophilic and hydrophobic modification of PAN and the CBC, as well as the coagulation behavior, were studied in terms of morphology, mechanical properties, and water regain property of the fibers. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1937–1946, 1997     

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     

Melting behavior and crystallization kinetics of poly(butylene terephthalate‐co‐diethylene terephthalate) and poly(butylene terephthalate‐co‐triethylene terephthalate) copolyesters

The melting behavior of poly(butylene terephthalate‐co‐diethylene terephthalate) and poly(butylene terephthalate‐co‐triethylene terephthalate) copolymers was investigated by differential scanning calorimetry after isothermal crystallization from the melt. Multiple endotherms were found for all the samples, and attributed to the melting and recrystallization processes. By applying the Hoffman‐Weeks' method, the equilibrium melting temperatures of the copolymers under investigation were obtained. Two distinct peaks in the crystallization exothermic curve were observed for all the samples. Both of them appeared at higher times than that of PBT, indicating that the introduction of a comonomer decreased the crystallization rate. The observed dependence of this latter on composition was explained on the basis of the content of ether–oxygen atoms in diethylene and triethylene terephthalate units, and of the different sizes of these units. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3545–3551, 2001