Compression molding and melt‐spinning of the blends of poly(lactic acid) and poly(butylene succinate‐co‐adipate)

Poly(lactic acid) (PLA) is a biobased polymer made from biomass having high mechanical properties for engineering materials applications. However, PLA has certain limited properties such as its brittleness and low heat distortion temperature. Thus, the aim of this study is to improve toughness of PLA by blending with poly(butylene succinate‐co‐adipate) (PBSA), the biodegradable polymer having high toughness. Polymer blends of PLA and PBSA were prepared using a twin screw extruder. The melt rheology and the thermal property of the blends were examined. Further the blends were fabricated into compression molded parts and melt‐spun fiber and were subjected to tensile and impact tests. When the PBSA content was low, PBSA phase was finely dispersed in the PLA matrix. On the other hand, when the PBSA content was high, this minor phase dispersed as a large droplet. Mechanical properties of the compression molded parts were affected by the dispersion state of PBSA minor component in PLA matrix. Impact strength of the compression molded parts was also improved by the addition of soft PBSA. The improvement was pronounced when the PBSA phase was finely dispersed in PLA matrix. However, the mechanical property of the blend fibers was affected by the postdrawing condition as well as the PBSA content. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41856.     

Nanocomposites of poly[(butylene succinate)‐co‐(butylene adipate)] (PBSA) and twice‐functionalized organoclay

A new method is described to prepare composites of poly[(butylene succinate)‐co‐(butylene adipate)] (PBSA) with an organophilic clay having a particular functional group, namely twice‐functionalized organoclay (TFC). TFCs were produced by treating Cloisite 25A^® with (glycidyloxypropyl)trimethoxy silane (GPS) or (methacryloyloxypropyl)trimethoxy silane (MPS). Reaction of the silane compound with the organoclay surface was monitored by Fourier‐transform infrared spectroscopy (FTIR). PBSA composites with the three different clays were prepared successfully via melt mixing. The d spacing and the morphology of the composites were monitored by X‐ray diffraction and by transmission electron microscopy. The linear storage modulus of the composites in the melt state increased significantly as a result of incorporation of TFC. Tensile modulus and strength at break of PBSA/TFC–GPS and those of PBSA/TFC–MPS were far superior to those of PBSA/C25A. Copyright © 2005 Society of Chemical Industry     

Biodegradable biocomposites from poly(butylene adipate‐co‐terephthalate) and miscanthus: Preparation,compatibilization, and performance evaluation

Miscanthus fibers reinforced biodegradable poly(butylene adipate‐co‐terephthalate) (PBAT) matrix‐based biocomposites were produced by melt processing. The performances of the produced PBAT/miscanthus composites were evaluated by means of mechanical, thermal, and morphological analysis. Compared to neat PBAT, the flexural strength, flexural modulus, storage modulus, and tensile modulus were increased after the addition of miscanthus fibers into the PBAT matrix. These improvements were attributed to the strong reinforcing effect of miscanthus fibers. The polarity difference between the PBAT matrix and the miscanthus fibers leads to weak interaction between the phases in the resulting composites. This weak interaction was evidenced in the impact strength and tensile strength of the uncompatibilized PBAT composites. Therefore, maleic anhydride (MAH)‐grafted PBAT was prepared as compatibilizer by melt free radical grafting reaction. The MAH grafting on the PBAT was confirmed by Fourier transform infrared spectroscopy. The interfacial bonding between the miscanthus fibers and PBAT was improved with the addition of 5 wt % of MAH‐grafted PBAT (MAH‐g‐PBAT) compatibilizer. The improved interaction between the PBAT and the miscanthus fiber was corroborated with mechanical and morphological properties. The compatibilized PBAT composite with 40 wt % miscanthus fibers exhibited an average heat deflection temperature of 81 °C, notched Izod impact strength of 184 J/m, tensile strength of 19.4 MPa, and flexural strength of 22 MPa. From the scanning electron microscopy analysis, better interaction between the components can be observed in the compatibilized composites, which contribute to enhanced mechanical properties. Overall, the addition of miscanthus fibers into a PBAT matrix showed a significant benefit in terms of economic competitiveness and functional performances. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45448.     

Preparation and characterization of poly[(butylene succinate)‐co‐(butylene adipate)]/carbon nanotube‐coated silk fiber composites

Biodegradable composites consisting of aliphatic polyesters (poly[(butylenes succinate)‐co‐(butylenes adipate)] (PBSA)) and Bombyx mori silk fibers coated with carbon nanotubes (CNTs) were prepared by melt compression molding. The mechanical properties of PBSA were enhanced by the incorporation of a small amount (3 wt%) of CNT‐coated silk fibers, while allowing its potential biodegradability to be retained, which could make these composites good candidates for commodity materials such as general‐purpose plastics. This improvement is attributed to the interactions between PBSA and CNT‐coated silk fibers in the composites. The average interfacial shear strength of the composites consisting of CNT‐coated silk fibers and PBSA matrix was 1.7 MPa, as measured by the microbond droplet test, while that of composites consisting of pure silk fibers and PBSA was only 1.1 MPa. The morphology of the CNT‐coated silk fiber‐reinforced composites was observed using scanning electron microscopy. Copyright © 2007 Society of Chemical Industry     

Enhanced biodegradation and processability of biodegradable package from poly(lactic acid)/poly(butylene succinate)/rice-husk green composites

This work aims to study the possibility to process PLA/PBS/RH green composites into hexagonal plant-pots employing a large-scale industrial operation using injection molding. Green composites based on poly(lactic acid) (PLA), poly(butylene succinate) (PBS), and rice husk (RH) with various RH contents (10–30%wt.) were produced successfully using a twin-screw extruder. The compatibility of RH-matrix was improved by chemical surface modifications using a coupling agent. RH was analyzed as an effective filler for PLA to develop green composites with low cost, high biodegradability, improved processability, and comparable mechanical properties as unfilled PLA. With increasing RH content, tensile modulus of the composites increased gradually. The addition of PBS, at PLA/PBS ratio of 60/40, improved the elongation at break and impact strength of PLARH30 by 55% and 7.1%, respectively. The suitable processing temperatures for PLA decreased from 220–230°C to 170–180°C when 30%wt. RH was composited into PLA matrix and were further reduced when PBS was applied. After biodegradation via either enzymatic degradation or hydrolysis, surface erosion with a large number of voids, mass loss, and the substantial decrease in tensile strength of all the composites were observed. In addition, the biodegradation of the composites has been improved by the addition of either RH or PBS.     

Crystallization,mechanical properties,and enzymatic degradation of biodegradable poly(ε‐caprolactone) composites with poly(lactic acid) fibers

Biodegradable polymer composites based on poly(ɛ‐caprolactone) (PCL) and poly(lactic acid) (PLA) fibers were prepared by melt compounding. The effects of PLA fibers on the crystallization, mechanical properties, and enzymatic degradation of PCL composites were investigated. The addition of PLA fibers enhanced the crystallization of PCL due to the heterogeneous nucleation effect of fibers. However, the final crystallinity of the PCL in the composites was little changed in the presence of PLA fibers. With the addition of PLA fibers, significant improvement in storage modulus (E′) of PCL in the composites was achieved. A significant increase in E′ was 173% for the composites as compared to that of the neat PCL at 20°C. With the increase in PLA fibers content, the PCL composites showed decreased elongation and strength at break; however, the tensile yield strength and modulus were increased significantly, indicating that PCL was obviously reinforced by adding PLA fibers. Although the PLA fibers retarded the enzymatic degradation of PCL, it was possible to be completely degraded without much degradation time for PCL blending with suitable amounts of PLA fibers. POLYM. COMPOS., 34:1745–1752, 2013. © 2013 Society of Plastics Engineers     

Preparation and properties of L‐lactide‐grafted sisal fiber–reinforced poly(lactic acid) composites

Pretreatment of the sisal fiber (SF) grafting with L‐lactide (LA) monomer via a ring‐opening polymerization catalyzed by a Sn(II)‐based catalyst was performed to improve the interfacial adhesion between SF and poly (lactic acid) (PLA). Biocomposites from LA‐grafted SF (SF‐g‐LA) and PLA were prepared by compression molding with fiber weight fraction of 10, 20, 30, and 40%, and then were investigated in contrast with alkali‐treated sisal fiber (ASF) reinforced PLA composites and untreated SF reinforced PLA composites. PLA composites reinforced by half‐and‐half SF‐g‐LA/untreated SF (half SF‐g‐LA) were prepared and studied as well, considering the disadvantages of SF‐g‐LA. The results showed that both the tensile properties and flexural properties of the SF‐g‐LA reinforced PLA composites were improved noticeably as the introduction of SF‐g‐LA, compared with pure PLA, untreated SF reinforced PLA composites and ASF reinforced PLA composites. The mechanical properties of the half SF‐g‐LA reinforced PLA composites were not worse, even better in some aspects, than the SF‐g‐LA reinforced PLA composites. Fourier transform infrared analysis and differential scanning calorimetry analysis exhibited that both the chemical composition and crystal structure of the SFs changed after LA grafting. In addition, the fracture surface morphology of the composites was studied by scanning electron microscopy. The morphological studies demonstrated that a better adhesion between LA‐grafted SF and PLA matrix was achieved. POLYM. COMPOS., 37:802–809, 2016. © 2014 Society of Plastics Engineers     

Mechanical properties of injection‐molded short‐fiber thermoplastic composites. Part 1: The elastic moduli and strengths of glass‐filled poly(butylene terephthalate)

The effects of processing and part geometry on the local mechanical properties of injection‐molded, 30 wt% short‐fiber‐reinforced filled poly(butylene terephthalate) (PBT) are characterized by mechanical tests on specimens cut from rectangular plaques of different thicknesses injection molded at several different processing conditions. Stiffness data from tensile tests at 12.7‐mm intervals on 12.7‐mm‐wide strips cut from injection‐molded plaques—both along the flow and cross‐flow directions—and flexural tests on these strips show consistency of plaque‐to‐plaque local properties. Also, in addition to the well‐known anisotropic properties caused by flow‐induced fiber orientation, injection‐molded short fiber composites exhibit in‐plane and through‐thickness nonhomogeneity—as indicated by in‐plane property variations, by differences between tensile and flexural properties, and by the flexural strength being significantly higher than the tensile strength. The sensitivity of these mechanical properties to process conditions and plaque geometry have also been determined: the flow‐direction tensile modulus increases with fill time, the differences between flow and cross‐flow properties decrease with increasing thickness, and both the flow and cross‐flow flexural moduli decrease with increasing plaque thickness. While the flexural modulus is comparable to the tensile modulus, the flexural strength is significantly higher than the tensile strength. POLYM. COMPOS., 26:428–447, 2005. © 2005 Society of Plastics Engineers     

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     

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     

Effects of the matrix crystallinity,dispersed phase,and processing type on the morphological,thermal, and mechanical properties of polylactide-based binary blends with poly[(butylene adipate)-co-terephthalate] and poly[(butylene succinate)-co-adipate]

In this study, we prepared immiscible blends of 75 wt % polylactide (PLA) with 25 wt % poly[(butylene adipate)-co-terephthalate] (PBAT) through an injection-molding (IM) process and a twin-screw extruder (TSE) followed by IM. An amorphous polylactide (A-PLA) and a semicrystalline polylactide (SC-PLA) were used as the matrixes to investigate the matrix crystallization effect on the morphology and property development of the blends with only IM. A blend of A-PLA with 25 wt % poly[(butylene succinate)-co-adipate] (PBSA) was also prepared through IM to compare its properties with those of the A-PLA–PBAT blends. The morphological, thermal, solid viscoelastic, tensile, and flexural properties of the blends were compared, and their dependency on the evolution of the blend morphology was analyzed. The tensile results show that when IM was used as the sole processing technique, the ductility and toughness were significantly improved only when SC-PLA was used as the matrix. Preprocessing through TSE also resulted in the enhancement of the blend ductility. In A-PLA–PBSA, the vitrification of PLA hindered the crystallization of PBSA to very low temperatures (<0°C) and resulted in a very nonuniform structure with weak intermolecular bonding between phases. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47636.     

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.     

The effect of poly(ethylene glycol) as plasticizer in blends of poly(lactic acid) and poly(butylene succinate)

The effect of polyethylene glycol (PEG) on the mechanical and thermal properties of poly(lactic acid) (PLA)/poly(butylene succinate) (PBS) blends was examined. Overall, it was found that PEG acted as an effective plasticizer for the PLA phase in these microphase‐separated blends, increasing the elongation at break in all blends and decreasing the T_g of the PLA phase. Significant effects on other properties were also observed. The tensile strength and Young's modulus both decreased with increasing PEG content in the blends. In contrast, the elongation at break increased with the addition of PEG, suggesting that PEG acted as a plasticizer in the polymer blends. Scanning electron microscope images showed that the fracture mode of PLA changed from brittle to ductile with the addition of PEG in the polymer blends. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43044.     

Poly(lactic acid)–thermoplastic poly(ether)urethane composites synergistically reinforced and toughened with short carbon fibers for three‐dimensional printing

In this study, we prepared short‐carbon‐fiber (CF)‐reinforced poly(lactic acid) (PLA)–thermoplastic polyurethane (TPU) blends by melt blending. The effects of the initial fiber length and content on the morphologies and thermal, rheological, and mechanical properties of the composites were systematically investigated. We found that the mechanical properties of the composites were almost unaffected by the fiber initial length. However, with increasing fiber content, the stiffness and toughness values of the blends were both enhanced because of the formation of a TPU‐mediated CF network. With the incorporation of 20 wt % CFs into the PLA–TPU blends, the tensile strength was increased by 70.7%, the flexural modulus was increased by 184%, and the impact strength was increased by 50.4%. Compared with that of the neat PLA, the impact strength of the CF‐reinforced composites increased up to 1.92 times. For the performance in three‐dimensional printing, excellent mechanical properties and a good‐quality appearance were simultaneously obtained when we printed the composites with a thin layer thickness. Our results provide insight into the relationship among the CFs, phase structure, and performance, as we achieved a good stiffness–toughness balance in the PLA–TPU–CF ternary composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46483.     

Rheological,thermal, and mechanical properties of phosphorus‐containing wholly aromatic thermotropic liquid crystalline polymer‐filled poly(butylene terephthalate) composites

Phosphorus‐containing wholly aromatic thermotropic liquid crystalline polymer (TLCP) reinforced poly(butylene terephthalate) (PBT) composites were prepared. Dynamic rheological analysis displayed that the addition of TLCP led to the decrease of the complex viscosity of PBT. While the thermal stability and tensile modulus were found to be increased distinctly, the results of dynamic mechanical analysis, isothermal crystallization, and morphological observation indicated that these changes were related to the rigid chains and in situ fibrillation of TLCP phase, and the interfacial adhesion between PBT and TLCP. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

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     

Toward environment‐friendly composites of poly(ε‐caprolactone) reinforced with stereocomplex‐type poly(l‐lactide)/poly(d‐lactide)

In this work, stereocomplex‐poly(l ‐ and d ‐lactide) (sc‐PLA) was incorporated into poly(ε‐caprolactone) (PCL) to fabricate a novel biodegradable polymer composite. PCL/sc‐PLA composites were prepared by solution casting at sc‐PLA loadings of 5–30 wt %. Differential scanning calorimetry (DSC) and wide‐angle X‐ray diffraction (WAXD) demonstrated the formation of the stereocomplex in the blends. DSC and WAXD curves also indicated that the addition of sc‐PLA did not alter the crystal structure of PCL. Rheology and mechanical properties of neat PCL and the PCL/sc‐PLA composites were investigated in detail. Rheological measurements indicated that the composites exhibited evident solid‐like response in the low frequency region as the sc‐PLA loadings reached up to 20 wt %. Moreover, the long‐range motion of PCL chains was highly restrained. Dynamic mechanical analysis showed that the storage modulus (E′) of PCL in the composites was improved and the glass transition temperature values were hardly changed after the addition of sc‐PLA. Tensile tests showed that the Young's modulus, and yield strength of the composites were enhanced by the addition of sc‐PLA while the tensile strength and elongation at break were reduced. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40208.     

Properties of poly(butylene adipate‐co‐terephthalate) and sunflower head residue biocomposites

Utilization of low‐value agricultural waste for polymer composite materials has great environmental and economical benefits. Sunflower head residue (SHR) as an agricultural waste may be used as a reinforcement in polymeric materials because of its fiber characteristics. In this work, composites of biodegradable poly(butylene adipate‐co‐terephthalate) (PBAT) and SHR were prepared via melt‐extrusion compounding. To improve interfacial compatibility, maleic anhydride (MA) grafted PBAT (PBAT‐g‐MA) was prepared and used as a compatibilizer for the PBAT/SHR composites. The effects of the concentrations of SHR and PBAT‐g‐MA on the morphology, mechanical properties, melt rheology, and water resistance of the composites were examined. Interfacial adhesion between phases in the PBAT/SHR composites was enhanced by the introduction PBAT‐g‐MA as interface‐strengthening agent, resulting in improved mechanical properties and moisture resistance of the composite. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44644.     

Effect of a chain extender on the rheological and mechanical properties of biodegradable poly(lactic acid)/poly[(butylene succinate)‐co‐adipate] blends

Biodegradable polymer blends based on poly(lactic acid) (PLA) and poly[(butylene succinate)‐co‐adipate] (PBSA) were prepared with a laboratory internal mixer. An epoxy‐based, multifunctional chain extender was used to enhance the melt strength of the blends. The morphology of the blends was observed with field emission scanning electron microscopy. The elongational viscosities of the blends, with and without chain extender, were measured with a Sentmanat extensional rheometer universal testing platform. The blends with chain extender exhibited strong strain‐hardening behavior, whereas the blends without chain extender exhibited only weak strain‐hardening behavior. Measurements of the linear viscoelastic properties of the melts suggested that the chain extender promoted the development of chain branching. The results show that PBSA contributed to significant improvements in the ductility of the PLA/PBSA blends, whereas the chain extender did not have a significant effect on the elastic modulus and strain at break of the blends. The combined blending of PLA with PBSA and the incorporation of the chain extender imparted both ductility and melt strength to the system. Thus, such an approach yields a system with enhanced performance and processability. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Factors influencing viscoelastic properties of a poly (butylene terephthalate) reinforced with short glass fibers

Short glass fiber/poly(butylene terephthalate) composites with different glass fiber treatments were characterized within a temperature range from −150°C to + 150°C by dynamic tests in torsion and tensile modes. Untreated fibers or fibers coated by silane coupling agents associated or not with sticking agents were used. It was observed that the magnitude of β and α relaxations depends strongly on the microstructural parameters of such composites: fiber content, degree of crystallinity of the matrix, fiber length distribution, level of adhesion.