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     

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     

Miscibility and crystallization in crystalline/crystalline blends of poly(butylene succinate)/poly(ethylene oxide)

Miscibility and crystallization behavior have been investigated in blends of poly(butylene succinate) (PBSU) and poly(ethylene oxide) (PEO), both semicrystalline polymers, by differential scanning calorimetry and optical microscopy. Experimental results indicate that PBSU is miscible with PEO as shown by the existence of single composition dependent glass transition temperature over the entire composition range. In addition, the polymer-polymer interaction parameter, obtained from the melting depression of the high-T_m component PBSU using the Flory-Huggins equation, is composition dependent, and its value is always negative. This indicates that PBSU/PEO blends are thermodynamically miscible in the melt. The morphological study of the isothermal crystallization at 95 °C (where only PBSU crystallized) showed the similar crystallization behavior as in amorphous/crystalline blends. Much more attention has been paid to the crystallization and morphology of the low-T_m component PEO, which was studied through both one-step and two-step crystallization. It was found that the crystallization of PEO was affected clearly by the presence of the crystals of PBSU formed through different crystallization processes. The two components crystallized sequentially not simultaneously when the blends were quenched from the melt directly to 50 °C (one-step crystallization), and the PEO spherulites crystallized within the matrix of the crystals of the preexisted PBSU phase. Crystallization at 95 °C followed by quenching to 50 °C (two-step crystallization) also showed the similar crystallization behavior as in one-step crystallization. However, the radial growth rate of the PEO spherulites was reduced significantly in two-step crystallization than in one-step crystallization.     

Poly(hydroxybutyrate)/poly(butylene succinate) blends: miscibility and nonisothermal crystallization

Four blends of poly(hydroxybutyrate) (PHB) and poly(butylene succinate) (PBSU), both biodegradable semicrystalline polyesters, were prepared with the ratio of PHB/PBSU ranging from 80/20 to 20/80 by co-dissolving the two polyesters in N,N-dimethylformamide and casting the mixture. Differential scanning calorimetry (DSC) and optical microscopy (OM) were used to probe the miscibility of PHB/PBSU blends. Experimental results indicated that PHB showed some limited miscibility with PBSU for PHB/PBSU 20/80 blend as evidenced by the small change in the glass transition temperature and the depression of the equilibrium melting point temperature of the high melting point component PHB. However, PHB showed immiscibility with PBSU for the other three blends as shown by the existence of unchanged composition independent glass transition temperature and the biphasic melt. Nonisothermal crystallization of PHB/PBSU blends was investigated by DSC using various cooling rates from 2.5 to 10 °C/min. During the nonisothermal crystallization, despite the cooling rates used two crystallization peak temperatures were found for PHB/PBSU 40/60 and 60/40 blends, corresponding to the crystallization of PHB and PBSU, respectively, whereas only one crystallization peak temperature was observed for PHB/PBSU 80/20 and 20/80 blends. However, it was found that after the nonisothermal crystallization the crystals of PHB and PBSU actually co-existed in PHB/PBSU 80/20 and 20/80 blends from the two melting endotherms observed in the subsequent DSC melting traces, corresponding to the melting of PHB and PBSU crystals, respectively. The subsequent melting behavior was also studied after the nonisothermal crystallization. In some cases, double melting behavior was found for both PHB and PBSU, which was influenced by the cooling rates used and the blend composition.     

Crystallization behavior of poly(butylene succinate)/corn starch biodegradable composite

The effects of corn starch (CS) filler and lysine diisocyanate (LDI) as a coupling agent on the crystallization behavior of a poly(butylene succinate) (PBS)/CS ecocomposite were investigated using differential scanning calorimetry. In isothermal crystallization, n values for pure PBS were from 2.33 to 2.82. On the other hand, both composites showed values of 3 < n < 4. In nonisothermal crystallization, the Avrami exponent varied from 2.12 to 2.55 for pure PBS, from 1.58 to 1.96 for the composite without LDI, and from 1.79 to 1.91 for the composite with LDI, depending on the cooling rate. There was not a large difference of the crystallization rate constant (k) as adjusted by the Jeziornay suggestion. The activation energy for nonisothermal crystallization was also calculated on the basis of three different equations (Augis–Bennett, Kissinger, and Takhor equations). However, the values of the activation energy were in contradiction with the results of the kinetics. The addition of the filler (CS) and coupling agent (LDI) affected the morphological structure of PBS spherulites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1107–1114, 2005     

聚丁二酸丁二醇酯/聚乙二醇硬脂酸酯共混物非等温结晶行为

以聚丁二酸丁二醇酯（PBS）和聚乙二醇硬脂酸酯（PEOST）为原料,采用溶液共混法制备了PEOST质量分数分别为10%（POS-10）和30%（POS-30）的两种合金材料。通过差示扫描量热法（DSC）研究了合金材料的非等温结晶行为,用莫志深（Mo）法分析了PBS的非等温结晶动力学,采用Kissinger法和Friedman法计算PBS的结晶活化能,并用红外（FTIR）和偏光显微镜（POM）进行表征。研究结果表明：PBS先结晶形成结晶微区不利于PEOST结晶,而较高含量的PEOST有利于PBS的结晶。受PBS先结晶的影响,POS-10降温DSC曲线没有出现PEOST的结晶峰,而POS-30在低的降温速率情况下出现了PEOST双结晶峰;升温DSC曲线中两试样均出现了PEOST的熔融峰。在相同的冷却速率下,POS-30的PEOST熔融温度（T_m）和熔融焓（△H_m）大于POS-10;POS-30的PBS结晶峰温度（T_p）、结晶焓（△H_c）大于POS-10,而结晶半峰宽（D）值更小;但两者的T_m和△H_m相当。随冷却速率的增加,PBS的D值增大,而PEOST的D值却降低;冷却速率的增加对PBS的T_m值影响不大,但使PEOST的T_m略有减小。Mo法适合用于共混物中PBS的非等温结晶动力学分析。POS-30的PBS绝对值结晶活化能要大于POS-10。POS-30在红外光谱谱图中出现了PEOST结晶的红外响应峰（1109cm^-1和841cm^-1）而POS-10没有。     

Effects of shearing and comonomer content on the crystallization behavior of poly(butylene succinate‐co‐butylene 2‐ethyl‐2‐methyl succinate)

Poly(butylene succinate‐co‐butylene 2‐ethyl‐2‐methyl succinate) (PBSEMS) random copolymers were prepared with different comonomer compositions. The effects of shearing and comonomer content on the crystallization behavior of these copolymers were investigated at 80 °C. The thermal and morphological properties of the resulting samples were also discussed. The copolymers showed a longer induction time and a slower crystallization rate with increasing comonomer content. The promoting effect of shear on the overall crystallization behavior was more notable for those copolymers containing more 2‐ethyl‐2‐methyl succinic acid (EMSA) units. The melting temperature of ‘as‐prepared’ poly(butylene succinate) (PBS) was ca. 115 °C, while that of the copolymers varied from 112 to 102 °C. Higher comonomer contents in the copolymers gave rise to lower melting temperatures and broader melting peaks. In addition, the isothermally crystallized samples showed multiple melting endothermic behavior, the extent of which depended on the comonomer content. The copolymers showed different wide‐angle X‐ray diffraction (WAXD) patterns from that of neat PBS, depending on the comonomer content and shear applied during crystallization. With increasing comonomer content, the copolymers crystallized without shearing, showing the shifting of a diffraction peak to a higher angle, while those crystallized under shear did not show any peak shift. Copyright © 2004 Society of Chemical Industry     

Synthesis and characterization of poly(butylene succinate)/epoxy group functionalized organoclay

Poly(butylene succinate) (PBS)/clay nanocomposites were prepared by condensation polymerization of 1,4‐butanediol and succinic acid in the presence of an organoclay containing epoxy groups (TFC) and titanium(IV) butoxide as a catalyst. The intercalation and exfoliation of the clay layers in the resulting composite were examined using X‐ray scattering and transmission electron microscopy. The role of the epoxy groups of TFC was investigated for the improvement of the morphology of the composites. The silicate layers in the composite were exfoliated to a greater extent as the epoxy content of TFC was increased from 0.245 to 0.359 mmol g^?1, while only intercalated morphology was obtained when no epoxy was present. The improved morphologies were attributed to the enhanced interfacial interactions between PBS and TFC through a chemical reaction of the epoxy groups with the end groups of the PBS. The nonisothermal crystallization process of the composites as well as that of neat PBS is well represented by the Avrami equation as modified by Jeziorny [Jeziorny A, Polymer 19 :1142 (1978)]. The crystallization of the composite took place faster as the epoxy content of the clay increased, due to the more effective nucleation of the well‐dispersed TFC layers. Copyright © 2007 Society of Chemical Industry     

The effect of 60Co γ‐rays on the crystal structure,melting and crystallization behavior of poly(butylene succinate)

The results obtained for poly(butylene succinate) (PBS) after ⁶⁰Co γ‐ray irradiation, studied by wide‐angle X‐ray diffraction (WAXD), differential scanning calorimeter (DSC) and polarizing optical microscopy (POM), revealed that the degree of crystallinity, melting temperature and enthalpy decreased with increasing irradiation dose, but that the crystal structure of PBS did not vary when compared to non‐irradiated PBS. By using Scherrer equation, small changes occurred in the crystal sizes of L₀₂₀, L₁₁₀ and L₁₁₁. The spherulitic morphology of PBS was strongly dependent on irradiation dose and changed significantly at higher irradiation dosages. The crystallization kinetics of PBS indicated that the Avrami exponent (n) for irradiated PBS was reduced to 2.3, when compared to non‐irradiated PBS (3.3). Copyright © 2004 Society of Chemical Industry     

Investigation on isothermal crystallization,melting behaviors,and spherulitic morphologies of multiblock copolymers containing poly(butylene succinate) and poly(1,2‐propylene succinate)

In this article, isothermal crystallization, melting behaviors, and spherulitic morphologies of high‐impact multiblock copolymers, comprising of PBS as hard segment and poly(1,2‐propylene succinate) (PPSu) as soft segment with hexamethylene diisocyanate as a chain extender, were investigated. The results from differential scanning calorimetry (DSC) suggest that the two segments of multiblock copolymers are miscible in amorphous region. The crystallization kinetics were analyzed by the Avrami equation. The effect of PBS segment length as well as the introduction of PPSu segment on the crystallization kinetics and melting bebaviors of block copolymers was studied. Both crystallization rate (G) and spherulitic growth rate (g) are markedly increased with the increase of PBS segment length or decreased with the incorporation of PPSu segment. All the multiblock copolymers show the multiple melting behaviors, whose position and area depend on PBS segment length and the presence of PPSu segment. The melting peaks shift to higher temperature region with increasing PBS segment length. Spherulitic morphologies of the multiblock copolymers after being isothermally crystallized were examined by polarized optical microscopy. It is the first time to investigate the effect of one segment length on crystallization bebavior of block copolymers based on a fixed weight ratio systematically. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Poly(butylene succinate)/poly(vinyl phenol) blends. Part 1. Miscibility and crystallization

Miscibility has been investigated in blends of poly(butylene succinate) (PBSU) and poly(vinyl phenol) (PVPh) by differential scanning calorimetry in this work. PBSU is miscible with PVPh as shown by the existence of single composition dependent glass transition temperature over the entire composition range. In addition, the polymer–polymer interaction parameter, obtained from the melting depression of PBSU using the Nishi–Wang equation, is composition dependent, and its value is always negative. This indicates that PBSU/PVPh blends are thermodynamically miscible in the melt. Preliminary morphology study of PBSU/PVPh blends was also studied by optical microscopy (OM). OM experiments show the spherulites of PBSU become larger with the PVPh content, indicative of a decrease in the nucleation density, and the coarseness of PBSU spherulites increases too with increasing the PVPh content in the blends.     

Mechanical and thermal properties of poly(butylene succinate)/plant fiber biodegradable composite

Biodegradable polymeric composites were fabricated from poly(butylene succinate) (PBS) and kenaf fiber (KF) by melt mixing technique. The mechanical and dynamic mechanical properties, morphology and crystallization behavior were investigated for PBS/KF composites with different KF contents (0, 10, 20, and 30 wt %). The tensile modulus, storage modulus and the crystallization rate of PBS in the composites were all efficiently enhanced. With the incorporation of 30% KF, the tensile modulus and storage modulus (at 40°C) of the PBS/KF composite were increased by 53 and 154%, respectively, the crystallization temperature in cooling process at 10°C/min from the melt was increased from 76.3 to 87.7°C, and the half‐time of PBS/KF composite in isothermal crystallization at 96 and 100°C were reduced to 10.8% and 14.3% of that of the neat PBS, respectively. SEM analysis indicates that the adhesion between PBS and KF needs further improvement. These results signify that KF is efficient in improving the tensile modulus, storage modulus and the crystallization rate of PBS. Hence, this study provides a good option for preparing economical biodegradable composite. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Phase behavior and morphology in blends of poly(L‐lactic acid) and poly(butylene succinate)

Blends of poly(L ‐lactic acid) (PLA) and poly(butylene succinate) (PBS) were prepared with various compositions by a melt‐mixing method and the phase behavior, miscibility, and morphology were investigated using differential scanning calorimetry, wide‐angle X‐ray diffraction, small‐angle X‐ray scattering techniques, and polarized optical microscopy. The blend system exhibited a single glass transition over the entire composition range and its temperature decreased with an increasing weight fraction of the PBS component, but this depression was not significantly large. The DSC thermograms showed two distinct melting peaks over the entire composition range, indicating that these materials was classified as semicrystalline/semicrystalline blends. A depression of the equilibrium melting point of the PLA component was observed and the interaction parameter between PLA and PBS showed a negative value of ?0.15, which was derived using the Flory–Huggins equation. Small‐angle X‐ray scattering revealed that, in the blend system, the PBS component was expelled out of the interlamellar regions of PLA, which led to a significant decrease of a long‐period, amorphous layer thickness of PLA. For more than a 40% PBS content, significant crystallization‐induced phase separation was observed by polarized optical microscopy. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 647–655, 2002     

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     

Orientation microstructure and properties of poly(propylene carbonate)/poly(butylene succinate) blend films

The blends of high molecular weight poly(propylene carbonate) (PPC) and poly(butylene succinate) (PBS) were melt blended using triphenylmethane triisocyanate (TTI) as a reactive coupling agent. TTI also serves as a compatibilizer for the blends of PPC and PBS. The blend containing 0.36 wt % TTI showed that the optimal mechanical properties were, therefore, calendared into films with different degrees of orientation. The calendering condition, degree of orientation, morphologies, mechanical properties, crystallization, and thermal behaviors of the films were investigated using wide‐angle X‐ray diffraction, scanning electron microscopy, tensile testing, and differential scanning calorimetry (DSC) techniques. The result showed that the as‐made films exhibited obvious orientation in machine direction (MD). Both tensile strength in MD and the tear strength in transverse direction (TD) increased with increasing the degree of orientation. The orientation of the film also increased the crystallinity and improved the thermal properties of the PPC/PBS blend films. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Non‐isothermal crystallization kinetics and melting behaviors of poly(butylene succinate) and its copolyester modified with trimellitic imide units

With the help of differential scanning calorimeter (DSC), the basic thermal behaviors, nonisothermal crystallization kinetics, and subsequent melting behaviors of poly(butylene succinate) (PBS) and its copolyester (PBSTMA) modified with trimellitic imide units were investigated in this paper. The DSC thermograms of PBS and PBSTMA showed that the crystallization behaviors of PBS were affected seriously because of the addition of a small quantity of trimellitic imide units. The nonisothermal crystallization processes of them were represented by the Avrami equation modified by Jeziorny and the method developed by Ozawa. After that, the conception of “crystallization rate coefficient (CRC)” introduced by Khanna was employed. The values of CRC for PBS and PBSTMA are 174.6 and 88.2 h^–1, respectively. At the end of this paper, the melting behaviors of PBS and PBSTMA after being cooled from 130 to 30°C at different cooling rate were studied in detail. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2493–2499, 2006     

聚丁二酸丁二醇酯/乙烯-醋酸乙烯共混物的形态与性能研究

用乙烯-醋酸乙烯橡胶（EVM）对聚丁二酸丁二醇酯（PBS）进行增韧改性,通过添加过氧化二异丙苯（DCP）使得PBS与EVM的相容性增强。结果表明,随着DCP含量的增大,PBS/EVM共混物的拉伸强度、断裂伸长率、肖氏硬度等力学性能先升高,随后又降低,其中拉伸强度由7 MPa 提高到17 MPa,100 %定伸应力由2 MPa提高到10 MPa;加入DCP使得PBS的结晶由受限结晶变为正常结晶;DCP的适宜添加量为0.3份。     

Crystallization and photo‐curing kinetics of biodegradable poly(butylene succinate‐co‐butylene fumarate) short‐segmented block copolyester

Short‐segmented block copolymers of poly(butylene succinate‐co‐butylene fumarate) were synthesized and their crystallinity and crosslinking behavior were investigated. ¹H NMR was used to characterize the microstructure and composition of the copolyesters. Molecular weight determination was performed using gel permeation chromatography. Based on the DSC results all copolyesters were crystalline and the degree of crystallinity of the copolymers did not change with butylene fumarate mole fraction due to co‐crystallization of the butylene succinate and butylene fumarate groups. Crosslinked copolyesters showed a lower crystallization rate and degree of crystallinity while the crystallization temperature shifted to higher temperatures compared with uncrosslinked copolyesters due to the formation of nucleating agents by crosslinkages. Photo‐DSC was used to investigate the crosslinking kinetics for UV‐initiated photo‐curing. Three kinetics parameters including the rate constant (k) and the orders of the initiation and propagation reactions (m and n, respectively) were determined for the quenched and unquenched copolymers. © 2016 Society of Chemical Industry     

Crystallization behaviour of cellulose acetate butylate/poly(butylene succinate)‐co‐(butylene carbonate) blends

The kinetics of the isothermal crystallization process from the melt of pure poly(butylene succinate)‐co‐(butylene carbonate) (PBS‐co‐BC) and its blends with cellulose acetate butylate (CAB) (10–30 wt%) was studied by differential scanning calorimetry (DSC) and the well‐known Avrami equation. In the blends, the overall crystallization rate of PBS‐co‐BC became slower with increasing CAB content. The equilibrium melting temperature ( ) of PBS‐co‐BC decreased with increasing CAB content, which was similar to that with other miscible crystalline/amorphous polymer blends. The slower crystallization kinetics of PBS‐co‐BC in the blends was explicable in terms of a diluent effect of the CAB component. By application of Turnbull–Fisher kinetic theory for polymer–diluent blend systems, the surface free energy (σ_e) of pure PBS‐co‐BC and of the blends was obtained, indicating that the blend with CAB resulted in a decrease in the surface free energy of folding of PBS‐co‐BC lamellar crystals. Copyright © 2006 Society of Chemical Industry     

Rheology,crystallization behaviors,and thermal stabilities of poly(butylene succinate)/pristine multiwalled carbon nanotube composites obtained by melt compounding

Poly(butylene succinate) (PBS)/pristine raw multiwalled carbon nanotube (MWCNT) composites were prepared in this work via simple melt compounding. Morphological observations indicated that the MWCNTs were well dispersed in the PBS matrix. Moreover, the incorporation of MWCNTs did not affect the crystal form of PBS as measured by wide‐angle X‐ray diffraction. The rheology, crystallization behaviors, and thermal stabilities of PBS/MWCNT composites were studied in detail. Compared with neat PBS, the incorporation of MWCNTs into the matrix led to higher complex viscosities (|η*|), storage modulus (G′), loss modulus (G″), shear thinning behaviors, and lower damping factor (tan δ) at low frequency range, and shifted the PBS/MWCNT composites from liquid‐like to solid‐like, which affected the crystallization behaviors and thermal stabilities of PBS. The presence of a very small quantity of MWCNTs had a significant heterogeneous‐nucleation effect on the crystallization of PBS, resulting in the enhancement of crystallization temperature, i.e., with the addition of 0.5 wt % MWCNTs, the values of T_c of PBS/MWCNT composites could attain to 90°C, about 6°C higher than that of neat PBS, whereas the values of T_c increased slightly with further increasing the MWCNTs content. The thermogravimetric analysis illustrated that the thermal stability of PBS was improved with the addition of MWCNTs compared with that of neat PBS. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011