Characterization of the mechanical and thermal properties and morphological behavior of biodegradable poly(L‐lactide)/poly(ε‐caprolactone) and poly(L‐lactide)/poly(butylene succinate‐co‐L‐lactate) polymeric blends

Two series of biodegradable polymer blends were prepared from combinations of poly(L ‐lactide) (PLLA) with poly(?‐caprolactone) (PCL) and poly(butylene succinate‐co‐L ‐lactate) (PBSL) in proportions of 100/0, 90/10, 80/20, and 70/30 (based on the weight percentage). Their mechanical properties were investigated and related to their morphologies. The thermal properties, Fourier transform infrared spectroscopy, and melt flow index analysis of the binary blends and virgin polymers were then evaluated. The addition of PCL and PBSL to PLLA reduced the tensile strength and Young's modulus, whereas the elongation at break and melt flow index increased. The stress–strain curve showed that the blending of PLLA with ductile PCL and PBSL improved the toughness and increased the thermal stability of the blended polymers. A morphological analysis of the PLLA and the PLLA blends revealed that all the PLLA/PCL and PLLA/PBSL blends were immiscible with the PCL and PBSL phases finely dispersed in the PLLA‐rich phase. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Rheological,thermal, and mechanical properties of P (3HB‐co‐4HB) and P (3HB‐co‐4HB)/EVA blends

Poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) [P(3HB‐co‐4HB)] fiber and P(3HB‐co‐4HB)/EVA fiber were obtained by single screw extrusion machine. The rheology of P(3HB‐co‐4HB) and P(3HB‐co‐4HB)/EVA blends was characterized by capillary rheometer, and the chemical groups of the blends were characterized with Fourier transform infrared spectroscopy (FT‐IR). The crystallization behavior and thermal, mechanical and elastic properties of the fibers were measured by differential scanning calorimeter (DSC), thermogravimetric analyzer (TGA) and single fiber strength tester, respectively. Besides, the moisture regain and drying shrinkage rates of the fibers were tested. These results showed that P(3HB‐co‐4HB)/EVA blends have better flowability, crystallinity, and thermal stability than P(3HB‐co‐4HB) fiber. The fracture strength of the P(3HB‐co‐4HB)/EVA fiber decreases with increasing the EVA content, but the elongation at break shows the contrary tendency. The rebound resilience ratio of P(3HB‐co‐4HB)/EVA fiber reaches 100%. Both moisture regain and drying shrinkage increase first and then decrease with increasing the EVA content. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41206.     

Mechanical and thermal properties of poly(butylene succinate)/poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) biodegradable blends

Biodegradable polymer blends of poly(butylene succinate) (PBS) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) were prepared with different compositions. The mechanical properties of the blends were studied through tensile testing and dynamic mechanical thermal analysis. The dependence of the elastic modulus and strength data on the blend composition was modeled on the basis of the equivalent box model. The fitting parameters indicated complete immiscibility between PBS and PHBV and a moderate adhesion level between them. The immiscibility of the parent phases was also evidenced by scanning electron observation of the prepared blends. The thermal properties of the blends were studied through differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The DSC results showed an enhancement of the crystallization behavior of PBS after it was blended with PHBV, whereas the thermal stability of PBS was reduced in the blends, as shown by the TGA thermograms. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42815.     

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     

Electrical conductivity and thermal properties of poly(m‐aminophenyl acetic acid) and its copolymers with aniline

Poly(m‐aminophenyl acetic acid) was synthesized under different conditions from the respective monomer, using ammonium persulfate as oxidizing agent in both the presence and the absence of CuCl₂ in HCl(aq). Moreover, the copolymers between aniline and m‐aminophenyl acetic acid were prepared at several feed mol ratios (f₁) of aniline. Copper was introduced by the Batch method in the homo‐ and copolymers of different compositions. The polymers were characterized by FTIR and UV‐vis spectroscopy, elemental analysis, thermal analysis, and electrical conductivity. The thermal stability and the content of copper increased as the content of aniline was increased in the copolymers. Moreover, the copolymers showed a high thermal stability; at 400°C a weight loss < 10% was observed. The electrical conductivity was increased with a higher content of aniline in the copolymers, achieving semiconduction values. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1484–1492, 2003     

Rheological,mechanical, thermal,and morphological properties of polypropylene/ethylene‐octene copolymer blends

Rheological and morphological studies were performed on polymer blends of ethylene‐octene copolymer [polyethylene elastomer (PEE)] and polypropylene (PP). The viscosities of PEE, PP, and PEE/PP blends were analyzed using an Instron capillary rheometer and a Rheometrics Dynamic Stress Rheometer, SR 200. A non‐Newtonian flow behavior was observed in all samples in the shear rate range from 27 to 2700 s⁻¹, whereas at shear rates in the range from 0.01 to 0.04 s⁻¹, a Newtonian flow behavior was verified. The scanning electron micrographs showed that dual‐phase continuity may occur between 50 and 60 (wt %) of PEE. This result is consistent with the Sperling's model. The mechanical analysis showed that PEE/PP, with 5 wt % of PEE, presented an increase on the mechanical properties and as the PEE content increased, a negative deviation in relation to an empirical equation was observed. Thermal analysis showed that there were no change in the crystallization behavior of the matrix when different elastomer contents were added. Dynamic mechanical thermal analysis showed that samples with low PEE contents presented only one peak, indicating a certain degree of miscibility between the components of these blends. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 692–704, 2000     

Effects of compatibilizer on the morphological,mechanical, and rheological properties of poly(methyl methacrylate)/poly(N‐methyl methacrylimide) blends

The effects of compatibilizer on the morphological, thermal, mechanical, and rheological properties of poly(methyl methacrylate) (PMMA)/poly(N‐methyl methacrylimide) (PMMI) (70/30) blends were investigated. The compatibilizer used in this study was styrene–acrylonitrile–glycidyl methacrylate (SAN‐GMA) copolymer. Morphological characterization of the PMMA/PMMI (70/30) blend with SAN‐GMA showed a decrease in PMMI droplet size with an increase in SAN‐GMA. The glass‐transition temperature of the PMMA‐rich phase became higher when SAN‐GMA was added up to 5 parts per hundred resin by weight (phr). The flexural and tensile strengths of the PMMA/PMMI (70/30) blend increased with the addition of SAN‐GMA up to 5 phr. The complex viscosity of the PMMA/PMMI (70/30) blends increased when SAN‐GMA was added up to 5 phr, which implies an increase in compatibility between the PMMA and PMMI components. From the weighted relaxation spectrum, which was obtained from the storage modulus and loss modulus, the interfacial tension of the PMMA/PMMI (70/30) blend was calculated using the Palierne emulsion model and the Choi‐Schowalter model. The results of the morphological, thermal, mechanical, and rheological studies and the values of the interfacial tension of the PMMA/PMMI (70/30) blends suggest that the optimum compatibilizer concentration of SAN‐GMA is 5 phr. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43856.     

Properties of soy protein isolate/poly(ethylene‐co‐ethyl acrylate‐co‐maleic anhydride) blends

Blends of soy protein isolate (SPI) with 10, 20, 30, 40, and 50% poly(ethylene‐co‐ethyl acrylate‐co‐maleic anhydride) (PEEAMA), with or without addition of 2.0 wt % methylene diphenyl diisocyanate (MDI), were prepared by mixing with an intensive mixer at 150°C for 5 min, and then milling through a 1‐mm sieve. Blends were then compression‐molded into a tensile bar at 140°C. Thermal and mechanical properties and water absorption of the blends were studied by differential scanning calorimetry (DSC), dynamical mechanic analysis (DMA), a test of modulus and tensile strength (with an Instron tensile tester), a water absorption test, and scanning electron microscopy (SEM). The blends showed two composition‐dependent glass transition temperatures. Furthermore, as the SPI content increased, the melting temperature of PEEAMA remained constant but the heat of fusion decreased. These results indicate that SPI and PEEAMA were partially miscible. Morphology observations support these results. Increasing the PEEAMA content resulted in decreases in the modulus and tensile strengths and increases in the elongation and toughness of the blends. Water absorption of the blends also decreased with increased PEEAMA content. Incorporating MDI further decreased the water absorption of the blends. The mechanism of water sorption of SPI was relaxation controlled, and that of the blends was diffusion controlled. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 407–413, 2003     

Reactive compatibilization of poly(l‐lactic acid)/poly(propylene carbonate) blends: Thermal,thermomechanical, and morphological properties

Poly(l ‐lactic acid) (PLLA) was blended with poly(propylene carbonate) (PPC) with various compositions by a melt‐blending process to evaluate their general properties for a potential flexible packaging field. The mechanical properties, including the tensile strength and modulus, revealed a tendency to decrease with the addition of ductile PPC; this was induced by the poor interfacial adhesion between PLLA and PPC with the cavities and clear edges and was observed through morphological observation. Reactive compatibilization was applied to improve the interfacial adhesion between PLLA and PPC, and the elongation at break was profoundly enhanced because of the improved interfacial adhesion between the two phases. The compatibilized PLLA/PPC blends showed considerable improvements in the storage modulus in the transition region with stable thermal stability; this could be a benefit for thermal processing. The addition of PPC had a great effect on the solidlike behavior and increased the elasticity of the PLLA/PPC blends. Up to 2.0 phr maleic anhydride showed a great efficiency in enhancing the dynamic storage modulus and complex viscosity of the PLLA/PPC blends. We also confirmed that it was feasible to fabricate PLLA/PPC blends with controllable barrier properties with combination of PLLA and PPC under reactive compatibilization while retaining the biodegradability. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43388.     

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     

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     

Curing behavior and thermal mechanical properties of cyanate ester blends

Cyanate esters are a class of important thermally resistant polymers. To tailor their processability and thermomechanical properties, a series of cyanate ester blends based on a trifunctional novolac cyanate ester (HF‐5), a difunctional bisphenol E cyanate ester (HF‐9), and a reactive catalyst [2,2′‐diallyl bisphenol A (DBA)] were formulated. The effect of the blend composition on the rheology and curing behavior of these cyanate ester blends and the corresponding thermal and mechanical properties of the cured cyanate ester blends was studied. The results showed that HF‐5 contributed to good mechanical property retention at high temperatures because of its trifunctionality, whereas HF‐9 imparted processability by reducing the viscosity and extending the pot life of the formulated cyanate ester blends at the processing temperature. On the basis of the results, an optimal cyanate ester blend suitable for resin transfer molding was determined: the HF‐5/HF‐9/DBA weight ratio of 80 : 15 : 5 exhibited good processability and thermomechanical properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4284–4290, 2006     

Microstructural,mechanical, and thermal‐insulation properties of poly(methyl methacrylate)/silica aerogel bimodal cellular foams

Novel poly(methyl methacrylate) (PMMA)/silica aerogel bimodal cellular foams were prepared by melt mixing and a supercritical carbon dioxide foaming process. The effects of the silica aerogel content on the morphologies and thermal‐insulating and mechanical properties of the foams were investigated by scanning electron microscopy, mechanical tests, and heat‐transfer analysis. The experimental results show that compared to the pure PMMA foam, the PMMA/silica aerogel microcellular foams exhibited more uniform cell structures, decreased cell sizes, and increased cell densities (the densities of the foams were 0.38–0.45 g/cm³). In particular, a considerable number of original nanometric cells (ca. 50 nm) were evenly embedded in the cell walls and on the inner surfaces of the micrometric cells (<10 μm). A 62.7% decrease in the thermal conductivity (0.072 W m⁻¹ K⁻¹) in comparison to that of raw PMMA after 0.5 wt % silica aerogel was added was obtained. Mechanical analysis of the PMMA/silica aerogel foams with 5 and 2 wt % silica aerogel showed that the compressive and flexural strengths were distinctly improved by 92 and 52%, respectively, and the dynamic storage moduli increased. The enhanced performance showed that with the addition of silica aerogel into PMMA, one can obtain thermal‐insulation materials with a favorable mechanical strength. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44434.     

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     

Thermal,mechanical, and surface characterization of starch–poly(vinyl alcohol) blends and borax‐crosslinked films

Starch–poly(vinyl alcohol) (PVA) blends with different compositions were prepared and crosslinked with borax by in situ and posttreatment methods. Various amounts of glycerol and poly(ethylene glycol) with a molecular weight of 400 were added to the formulations as plasticizers. The pure starch–PVA blends and the crosslinked blends were subjected to differential scanning calorimetry, thermogravimetry, and X‐ray photoelectron spectroscopic studies. Broido and Coats–Redfern equations were used to calculate the thermal decomposition kinetic parameters. The tensile strengths and elongation percentages of the films were also evaluated. The results suggested that the glass‐transition temperature (T_g) and the melting temperature strongly depended on the plasticizer concentration. The enthalpy relaxation phenomenon was dependent on the starch content in the pure blend. The crosslinked films showed higher stability and lower T_g's than pure PVA and starch–PVA blends, respectively. High‐resolution X‐ray photoelectron spectroscopy provided a method of differentiating the presence of various carbons associated with different environments in the films. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1313–1322, 2005     

Evaluation of mechanical properties and physical interactions of a ternary blend of poly(ethylene‐co‐octene)/poly(ethylene‐co‐vinyl acetate)/poly(vinyl chloride) in the molten state

In this work, ethylene‐co‐vinyl acetate (EVA), poly(ethylene‐co‐octene) (POE), and poly(vinyl chloride) (PVC) blends were processed in a molten state process using a corotating twin‐screw extruder to assess both the balance of mechanical properties and physical interactions in the melt state. Tensile measurements, scanning electron microscopy, and oscillatory rheometry were performed. By means of flow curves, the parameters of the power law as well as the distribution of relaxation times were assessed with the aid of a nonlinear regularization method. The mechanical properties for the EVA‐POE blend approximated the values for POE, while inclusion of PVC shifted the modulus values to those of neat EVA. The rise in modulus was corroborated by the PVC phase dispersion as solid particles that act as a reinforcement for the ternary blend. The rheological properties in the molten state show that the POE does not present molecular entanglement effects and so tends both to diminish the EVA mechanical properties and increase the fluidity of the blend. However, the addition of PVC both restored the EVA typical pseudoplastic feature and promoted the increase in the viscosity and the mechanical properties of the ternary blend. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Polyhydroxybutyrate/acrylonitrile‐g‐(ethylene‐co‐ propylene‐co‐diene)‐g‐styrene blends: Their morphology and thermal and mechanical behavior

Polyhydroxybutyrate (PHB) is a biodegradable bacterial polyester emerging as a viable substitute for synthetic, semicrystalline, nonbiodegradable polymers. An elastomer terpolymer of acrylonitrile‐g‐(ethylene‐co‐propylene‐co‐diene)‐g‐styrene (AES) was blended with PHB in a batch mixer and in a twin‐screw extruder to improve the mechanical properties of PHB. The blends were characterized with differential scanning calorimetry, dynamic mechanical analysis, scanning electron microscopy, and impact resistance measurements. Despite the narrow processing window of PHB, blends with AES could be prepared via the melting of the mixture without significant degradation of PHB. The blends were immiscible and composed of four phases: poly(ethylene‐co‐propylene‐co‐diene), poly(styrene‐co‐acrylonitrile), amorphous PHB, and crystalline PHB. The crystallization of PHB in the blends was influenced by the AES content in different ways, depending on the processing conditions. A blend containing 30 wt % AES presented impact resistance comparable to that of high‐impact polystyrene, and the value was about 190% higher than that of pure PHB. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Influence of thermal and morphological characteristics on mechanical responses of polypropylene/γ‐irradiated elastomer blends

The approach of this paper is to examine the mechanical responses of polypropylene (PP)/γ‐irradiated ethylene acrylic elastomer blends and subsequently compare them with the PP/unirradiated ethylene acrylic elastomer blends. Thorough correlations were drawn between the mechanical characteristics of blends and their morphological, thermal, thermomechanical, and fractured surface morphological aspects. The idea of carrying out γ‐irradiation was to introduce crosslinking points in the elastomer phase. For better understanding, correlations between the impact test results and the fractured surface morphologies were analyzed. The limited tensile properties of PP/γ‐irradiated elastomer blends were attributed not only to the poor interfacial adhesion, obtained by fitting with several theoretical mechanical models, but also to the substantially higher elastomer particle size in the blends than in the PP/unirradiated elastomer blends. The higher loss modulus and tan δ values for PP/unirradiated elastomer blends along with the attainment of much smaller particles of elastomers were responsible for the phenomenal increase in impact properties, which was actually attributed to the formation of crazes inside the dispersed phase during applied impact stress. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46597.     

Mechanical,rheological, thermal,and morphological properties of blends based on poly(propylene)/poly(propylene‐co‐1‐octene)/poly(ethylene‐co‐1‐octene)

The effect of addition of propylene copolymer, produced by metallocene catalysts, on the mechanical, rheological, and morphological properties of blends based on poly(propylene) (PP) and ethylene–1‐octene copolymer (EOC) was evaluated. It was observed that the addition of 2 wt % propylene–1‐octene copolymer (POC) improved the impact strength of the EOC/PP blends. The rheological analysis indicated that the addition of propylene copolymer produced materials with improved processability. Thermal and morphological analysis showed that the POC acts as a compatibilizer on the EOC/PP blends. © 2003 Wiley Periodicals, J Appl Polym Sci 89: 1690–1695, 2003     

Influence of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) on miscibility and properties of atactic poly(methyl methacrylate)

Miscibility and properties of two atactic poly(methyl methacrylate)‐based blends [containing 10 and 20% of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)] have been investigated as a function of thermal treatments. Differential scanning calorimetry and dynamic mechanical thermal analysis of blends quenched in liquid nitrogen or ice/water, after annealing at T > 190 °C, showed a single glass transition temperature, indicating miscibility of the components for the time‐temperature history. Two glass transition temperatures, equal to those of the pure components, are instead found for blends after annealing at T < 190 °C. Scanning electron microscopy confirmed the homogeneity for the former quenched blends and phase separation for the latter. These results indicate the presence of an upper critical solution temperature (UCST). Tensile experiments, performed on two series of samples annealed at temperatures above and below the UCST, showed that the copolyester induces a decrease of Young's modulus and stresses at yielding and break points, and a marked increase of elongation at break. Differences in tensile properties between the two series of annealed blends are accounted for by the physical state of the components at room temperature after annealing above or below the UCST. Copyright © 2004 Society of Chemical Industry