Poly(lactic acid)/coplasticized thermoplastic starch blend: Effect of plasticizer migration on rheological and mechanical properties (original) (raw)
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Mechanical, Thermal and Morphological Properties of PLA/PP Melt Blends
2012
In this study, polylactic acid (PLA) was melt blended with polypropylene (PP) and liquid natural rubber (LNR) with the ratio of PLA/PP (90/10) and PLA/PP/LNR (90/10/10) in the Haake Rheomix internal mixer. The mechanical properties of such as stress- strain, flexural and impact were studied. It was found that the elongation at break, flexural and notched impact strength increased significantly for the LNR compatibilized PLA/PP blend. The DSC and FTIR showed the PLA/PP and PLA/PP/LNR were not miscible.
Effect of chain extension on the properties of PLA/TPS blends
Journal of Applied Polymer Science, 2011
ABSTRACT Multifunctional Epoxy-based copolymers can be used as chain-extender (CE) to increase the molecular weight and create branching in polylactides (PLA). In this study, the effect of a multifunctional epoxy-acrylic-styrene copolymer on the properties of PLA/Thermoplastic Starch (PLA/TPS) blends was investigated. The PLA/TPS blends were prepared by twin-screw extrusion. The dry-starch and plasticizers were mixed together in the first half of the extruder to complete starch gelatinization. Water was removed by devolatilization at midex-truder and the PLA matrix was mixed with the water-free TPS in the latter portion of the compounding process. The standard blends comprised 27% TPS in the PLA matrix. The TPS phase itself comprised 36% plasticizer in the form of glycerol or sorbitol. A maleic anhydride grafted PLA (PLAg) was also used in selected blends to examine the effect of interfacial modification on the morphology of chain-extended blends. The blends were injection molded into standard test bars and their tensile properties were measured. Differential scanning calorimetry was carried out to examine the effect of chain extension on PLA's ability to crystallize. Oscillatory-shear rheology was used to monitor changes in blend viscosity. Finally, scanning electron microscopy on microtomed and acid-etched samples was carried out to assess the blend morphology. It was found that the combination of interfacial modification and chain-extension strategies led to greatly improved ductility. The viscosity of the PLA/TPS blends was also dramatically increased by adding a small amount of epoxy-based chain extender. This is of great interest for polymer processing techniques (such as foaming or film blowing) that require high melt strength. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Strong synergistic effects in PLA/PCL blends: Impact of PLA matrix viscosity
Journal of the mechanical behavior of biomedical materials, 2017
Blends of two biodegradable polymers, poly(lactic acid) (PLA) and poly(ϵ-caprolactone) (PCL), with strong synergistic improvement in mechanical performance were prepared by melt-mixing using the optimized composition (80/20) and the optimized preparation procedure (a melt-mixing followed by a compression molding) according to our previous study. Three different PLA polymers were employed, whose viscosity decreased in the following order: PLC ≈ PLA1 > PLA2 > PLA3. The blends with the highest viscosity matrix (PLA1/PCL) exhibited the smallest PCL particles (d∼0.6μm), an elastic-plastic stable fracture (as determined from instrumented impact testing) and the strongest synergistic improvement in toughness (>16× with respect to pure PLA, exceeding even the toughness of pure PCL). According to the available literature, this was the highest toughness improvement in non-compatiblized PLA/PCL blends ever achieved. The decrease in the matrix viscosity resulted in an increase in the a...
Polymers
In this work poly(lactic) acid (PLA)/poly(butylene succinate-co-adipate) (PBSA) biobased binary blends were investigated. PLA/PBSA mixtures with different compositions of PBSA (from 15 up to 40 wt.%) were produced by twin screw-extrusion. A first screening study was performed on these blends that were characterized from the melt fluidity, morphological and thermo-mechanical point of view. Starting from the obtained results, the effect of an epoxy oligomer (EO) (added at 2 wt.%) was further investigated. In this case a novel approach was introduced studying the micromechanical deformation processes by dilatometric uniaxial tensile tests, carried out with a videoextensometer. The characterization was then completed adopting the elasto-plastic fracture approach, by the measurement of the capability of the selected blends to absorb energy at a slow rate. The obtained results showed that EO acts as a good compatibilizer, improving the compatibility of the rubber phase into the PLA matrix...
Journal of Polymers and the Environment, 2018
The blends of polylactic acid plasticized with acetyl tributyl citrate (P-PLA) and thermoplastic wheat starch (TPS) were prepared by a co-rotating twin screw extruder and the effect of maleic anhydride grafted PLA (PLA-g-MA) content as reactive compatibilizer on blends compatibility through morphological, rheological and tensile properties of the blends was investigated. Considerable improvement in properties of P-PLA/TPS (70/30 w/w) blend with incorporating the optimum PLA-g-MA content of 4 phr was achieved as this blend exhibited better morphological and rheological properties with an increase by 158 and 276% in tensile strength and elongation at break, respectively, compared to the uncompatibilized blend. Also the thermal stability and moisture sorption properties of the blends as effected by TPS content were studied. Decreasing in thermal stability and increasing in equilibrium moisture content of the blends were observed with progressively increasing of TPS content. For prediction the moisture sorption behaviour of blends with various TPS contents at different relative humidity, the moisture sorption isotherm data were modeled by GAB (Guggenheim-Anderson-de Boer) model.
Effect of TPU hard segment content on the rheological and mechanical properties of PLA/TPU blends
Journal of Applied Polymer Science, 2020
Blends of an amorphous polylactide (PLA) with three different thermoplastic polyurethane (TPU) grades having various hard segment (HS) contents are prepared at the blending ratio of 85/15 wt% through a twin-screw extruder (TSE) at processing temperatures of 150 and 190 C. Blends of a semicrystalline PLA with 15 wt% of the noted TPU grades are also processed in the TSE at 190 C to investigate the matrix crystallization effect on the morphology and property enhancements. The rheological experiments reveal that the increase in TPU HS content significantly increases the phase compatibility between PLA and TPU as also suggested by the finer morphology of the TPU phase, although the use of lower HS TPUs is more favorable to enhance the ductility and impact properties of the blends.
Melt Flow Behavior and Processability of Polylactic Acid/ Polystyrene (PLA/PS) Polymer Blends
The present investigation dealt with the flow behavior and processability of polylactic acid/polystyrene (PLA/PS) polymer blends using a capillary rheometer. For this purpose, PLA/PS blends with different ratios of the concentrations were prepared using a single screw extru-der. The shear viscosity, shear stress, shear rate, power-law index, viscous activation energy at a constant shear stress, and elongational stress were determined. PLA/PS blends exhibited a typical shear-thinning behavior over the entire range of shear rates tested, and the viscosity values of the blends would tend to decrease with increasing amount of PLA. In addition, the polymer blend of 70 % PLA and 30 % PS was found to be relatively less sensitive to the processing temperature, implying that the extrusion process was more desirable for fabrication of PLA/PS polymer blend than the injection process.
Iranian Polymer Journal, 2012
Effect of the blend ratios on the morphology and melt rheology of poly(lactic acid) (PLA)/poly(butylene succinate adipate) (PBSA) blends were investigated using scanning electron microscope, strain-controlled rheometer, and capillary rheometer techniques. The morphological analysis shows that the average radius of the dispersed droplets of PBSA particles increases with change in the blend composition, and a co-continuous structure was generated when PBSA content reached 40%. For the linear viscoelasticity, the increase in the storage modulus at low-frequency region was more distinct in PLA/PBSA blends than in their pure components. A second plateau is clearly observed when the PBSA content was 20% or higher. Weight relaxation spectra showed that there was a longer relaxation time for blend system. These relaxation times were considered to be the shape relaxation periods of the droplets, which increase with change in the blend composition. The interfacial tensions of the PLA/PBSA blends at different compositions were between 5.3 and 6.1 mN/m, calculated from the weighted relaxation spectra and slightly higher than those obtained from Palierne model. These values are relatively high, indicating the poor miscibility of the two polymers. Both pure PLA and PBSA follow the Cox-Merz rule, in good manner. Though, the rule does not satisfy with the PLA/ PBSA blends. In addition, PLA/PBSA blends show more non-Newtonian tendencies than their pure components.
Effects of Compatibilizer on Thermal and Mechanical Properties of PLA/NR Blends
Materials Science Forum, 2015
The aim of the research is to study the effects of compatibilizer on thermal and mechanical properties ofbiopolymer poly (lactic acid) (PLA) and natural rubber (NR) blends. PLA was blended with NR in the composition of 95/5 weight percentage with present of compatibilizer. The compatibilizers, PLA grafted maleic anhydride (MA) (PLA-g-MA) and NR grafted MA (NR-g-MA) were synthesized in a composition of 9 phr of MA by using internal mixer in presence of benzoyl peroxide (BPO). The formulations of PLA/NR blended with the compatibilizer were in the range of 1, 3, 5 and 10 wt.% of PLA-g-MA and NR-g-MA, respectively. Blending process was conducted using twin screw extruder then were pelletized and hot pressed before characterized. The mechanical (tensile, flexural, impact) and thermal properties of the blends was investigated and from the results, the addition of PLA-g-MA in PLA/NR blendimproved the impact strength and elongation at break of the blends as compared with neat PLA and PLA/NR blend without compatibilizer and for thermal stability, it only had a slight influence on the blends. Addition of NR-g-MA on contrary did not give improvement on mechanical properties but increasing in thermal stability.
Journal of Applied Polymer Science, 2011
a melt-blending technique in an attempt to improve the melt processability of PLA. Maleic anhydride (MAH)-grafted PP and glycidyl methacrylate were used as the reactive compatibilizers to induce miscibility in the blend. The PLA/PP blend at a blend ratio of 90 : 10, exhibited optimum mechanical performance. Differential scanning calorimetry and thermogravimetric analysis studies showed that the PLA/PP/MAH-g-PP blend had the maximum thermal stability with the support of the heat deflection temperature values. Furthermore, dynamic mechanical analysis findings revealed an increase in the glass-transition temperature and storage modulus with the addition of MAH-g-PP compatibilizer. The interaction between the compatibilizers and constituent polymers was confirmed from Fourier transform infrared spectra, and scanning electron microscopy of impact-fractured samples showed that the soft PP phase was dispersed within the PLA matrix, and a decrease in the domain size of the dispersed phase was observed with the incorporation of MAH-g-PP, which acted as a compatibilizer to improve the compatibility between PLA and PP.