Hydrolytic stability of polylactide and poly(methyl methacrylate) blends

The hydrolytic stability of polylactide/poly(methyl methacrylate) (PLA/PMMA) blends prepared using a twin‐screw extrusion process was investigated. The effects of hydrolysis were monitored in neutral and alkaline media at 80 °C by tracking the changes in molecular weight distribution, weight loss, water uptake, and crystallization behavior. The crystallinity of PLA in blends prior to hydrolysis was shown to be largely hindered by the presence of PMMA. However, PLA recrystallized rapidly during hydrolysis. The PMMA in the blends was shown to provide increased hydrolytic and structural stability to the blends. In the neutral medium, the presence of PMMA delayed and reduced the weight loss but did not significantly affect PLA degradation kinetics. On the other hand, in the alkaline medium, the weight loss rate was strongly decreased in presence of PMMA and the kinetics of degradation was shown to be depend on PMMA content. The microstructure of these blends throughout the hydrolysis process was also examined by scanning electron microscopy. A porous structure, with interconnected pores in the 20–50 nm range, was developed due to the selective removal of PLA. Based on these morphological observations, erosion mechanism of PLA/PMMA blends was discussed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45991.     

Design of highly tough poly(l‐lactide)‐based ternary blends for automotive applications

Technical renewable poly(l ‐lactide) (PLA)‐based blends represent an elegant way to achieve attractive properties for engineering applications. Recently, the miscibility between PLA and poly(methyl methacrylate) (PMMA) gave rise to new formulations with enhanced thermo‐mechanical properties but their high brittleness still remains a challenge to be overcome. This work here focuses on rubber‐toughened PLA/PMMA formulations for injection‐molding processes upon the addition of a commercially available ethylene‐acrylate impact modifier (BS). The miscibility between PLA and PMMA is not altered by the presence of BS but the incorporation of BS (17% by weight) into a PLA/PMMA matrix could enhance both ductility and toughness of PLA/PMMA blends for PMMA content up to 50 wt %. An optimum range of particle sizes (d_n ～0.5 µm) of the dispersed domains for high impact toughness is identified. These bio‐based ternary blends appear as promising alternatives to petro‐sourced blends such as ABS‐based blends in engineering injection‐molding parts. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43402.     

Biobased blends of poly(propylene carbonate) and poly(hydroxybutyrate‐co‐hydroxyvalerate): Fabrication and characterization

Poly(propylene carbonate) (PPC), a CO₂‐based bioplastic and poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV) were melt blended followed by injection molding. Fourier transform infrared spectroscopy detected an interaction between the macromolecules from the reduction in the OH peak and a shift in the C?O peak. The onset degradation temperature of the polymer blends was improved by 5% and 19% in comparison to PHBV and PPC, respectively. Blending PPC with PHBV reduced the melting and crystallization temperatures and crystallinity of the latter as observed through differential scanning calorimetry. The amorphous nature of PPC affected the thermal properties of PHBV by hindering the spherulitic growth and diluting the crystalline region. Scanning electron micrographs presented a uniform dispersion and morphology of the blends, which lead to balanced mechanical properties. Incorporating PHBV, a stiff semi‐crystalline polymer improved the dimensional stability of PPC by restricting the motion of its polymer chains. © 2016 The Authors Journal of Applied Polymer Science Published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44420.     

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.     

Compatibility improvement of poly(lactic acid)/thermoplastic polyurethane blends with 3‐aminopropyl triethoxysilane

Poly(lactic acid) (PLA)/thermoplastic polyurethane (TPU) blends were prepared via a melt‐blending process with or without the addition of a 3‐aminopropyl triethoxysilane (APTES) compatibilizer at different dosages. The addition of the compatibilizer showed improved compatibility between TPU and PLA; this led to an enhanced dispersion of TPU within the PLA matrix. With the addition of 1‐phr APTES, the crystallization behavior did not vary much, but this exacerbated the formation of a second melting temperature for PLA at higher temperature. However, the addition of 5‐phr APTES into the PLA/TPU blends depressed the crystallization temperature and resulted in a melting temperature depression phenomena with the disappearance of the second melting peak because of the lubricated effect of low‐molecular‐weight species of APTES. The addition of a low dosage of APTES improved the impact strength further from 29.2 ± 1.4 to 40.7 ± 2.7 J/m but with a limited improvement in the tensile properties; this indicated that a higher dispersion of the dispersed phase did not always improve all of the mechanical properties because of the low‐molecular‐weight nature of the compatibilizer used. The physical properties of the added modifier needed to be considered as well. A low dosage of APTES (1 phr) also increased the viscosity because of the improved interaction between TPU and PLA at all of the investigated shear rate regions, but a higher dosage of compatibilizer induced another plasticizing effect to reduce the viscosity. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42322.     

Statistical optimization of compatibilized blends of poly(lactic acid) and acrylonitrile butadiene styrene

A mixture design of experiment and subsequent regression analysis was used to study the effects of two additives on blends of poly(lactic acid) (PLA) and acrylonitrile butadiene styrene (ABS). Statistical analysis was used to find a blend with a balance of high toughness, strength, and stiffness. The blends were prepared by lab scale reactive extrusion and injection molding. Least‐square regression models of statistically significant effects were built by analysis of variance (ANOVA). Using these models, optimization studies were used to study the predicted maximum values of each measurement criteria. Very large increases were seen in the measured responses with relatively small changes in additive content. Compared to the neat blend without additives, the impact strength was increased by over 600%, the elongation at break was increased by over 1000%, the tensile strength increased by 11%, and the tensile modulus increased by over 7%. Surprisingly, the composite optimization, which included all measured criteria, occurred at a point that allowed all four criteria values to remain very close to their individual maximums. The result is a partially biobased blend that does not sacrifice strength or stiffness to achieve very high toughness. © 2016 The Authors Journal of Applied Polymer Science Published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44516.     

Toughening of poly(l‐lactide) modified by a small amount of acrylonitrile−butadiene−styrene core‐shell copolymer

A small amount of acrylonitrile‐butadiene‐styrene (ABS) core shell copolymer particles are used to improve the toughness of poly(l ‐lactide) (PLLA) matrix. The incorporation of ABS copolymer dramatically increased the elongation yield at break of PLLA. For PLLA blend with 6.0 wt % ABS copolymer particles, the elongation yield at break increased by 28 times and the notched impact strength improved by 100% comparing with those of neat PLLA. Fourier transformed infrared (FTIR) and dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM) measurement results indicated that the special polarity interaction between ester group of PLLA matrix and nitrile group of PSAN shell phase enhanced the interfacial adhesion between PB rubber phase and PLLA matrix and promoted the fine dispersion of ABS particles in PLLA matrix. Meanwhile, ABS core shell particles also showed a certain extent of effects on the crystallinity behavior of PLLA. A small amount of ABS particles became the nucleating sites, and then the degree of crystallinity of PLLA/ABS blends increased. However, the notched impact of PLLA blends decreased because of the aggregation of more ABS particles. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42554.     

Corotating twin-screw extrusion of poly(lactic acid) PLA/poly(butylene succinate) PBS/ micro-lamellar talc blends for extrusion blow molding of biobased bottles for alcoholic beverages

Extrusion blow molding is a well-established technology for the manufacture of fossil-based plastic bottles. The process is, however, still little used for the manufacture of bottles with a low environmental footprint, especially those based on bioplastic from renewable sources. In this context, the objective of this work is precisely the study and experimental design of poly(lactic acid) PLA/poly(butylene succinate) PBS/micro-lamellar talc compounds for the manufacturing of bioplastic bottles, basically for wine packaging. In particular, the design was carried out to ensure, primarily, an adequate processability of the bioplastic material in the blowing process. Second, the compound was loaded with different micro-lamellar talc content so as to achieve protection from the environmental factors, which is of paramount importance to ensure a long shelf-life to wine. The bio-derived polyester resins are very complex to transform, as they are subject to thermo-hydrolytic degradation phenomena during the processing of the polymer melt. Processability is further limited in the presence of high micro-lamellar talc content that increases the melt viscosity, thus making the material even more difficult to shape by extrusion blow molding. The experimental analysis involved the use of a co-rotating twin-screw extruder for the manufacture of the bioplastic compounds. The compounds were first subjected to thermo-rheological and physical characterization tests. Second, it was tested in the extrusion blow molding process. The experimental results have shown that blends based on bio-derived polyester resins can be adequately processed by extrusion blow molding, showing extremely stable rheological behavior both during the extrusion phase of the parison and the subsequent blowing process of the parison itself. These blends have, therefore, an interesting potential to be used as an alternative with a low environmental footprint to oil-based plastics in the production of wine bottles.     

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.     

Improvement of the thermal properties of poly(3‐hydroxybutyrate) (PHB) by low molecular weight polypropylene glycol (LMWPPG) addition

In this work, blends of poly(3‐hydroxybutyrate) (PHB) with 5, 10, 15, and 20 wt % low molecular weight poly(propylene glycol) (LMWPPG) have been prepared and characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) with attenuated total reflectance (ATR) accessory and simultaneous thermal analysis (TG/DTA). FTIR and thermal analyses suggested that the presence of LMWPPG led to a maximum crystallinity for the blend PHB/PPG (90/10) blend. The presence of LMWPPG also caused a significant increase of the PHB processability window, i.e., the difference of the melting and degradation temperature, of PHB from 105 to 134°C, which is extremely important for the industrial uses of PHB. This PHB stabilization effect is discussed in terms of an intermolecular interaction of the PHB carbonyl with LMWPPG methyl groups which probably hinders the classical radon β‐scission PHB intramolecular decomposition mechanism. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Enhanced impact strength of compatibilized poly(lactic acid)/polyamide 11 blends by a crosslinking agent

Maleated poly(lactic acid) (PLA-g-MA) was prepared through melt grafting of maleic anhydride onto a PLA backbone with the aid of a radical initiator. PLA-g-MA thus formed was incorporated into PLA/polyamide 11 (PA11) blends as a reactive compatibilizer. By morphological observation, it was assessed that PLA-g-MA lowered the interfacial energy and strengthened the interface between PLA and PA11. However, the compatibilized PLA/PA11 blends did not show significant improvement of impact strength compared with noncompatibilized PLA/PA11 blends. Measurements of the molecular weight and impact strength of PLAs compounded with various amounts of radical initiators revealed that decreased molecular weight of PLA by the radical initiator used for the preparation of PLA-g-MA is responsible for this unexpected result. To compensate the decrease of the molecular weight, a crosslinking agent was incorporated in the preparation step of PLA-g-MA. It was found that the crosslinking agent is effective in preventing the molecular weight reduction. As a result, the impact strength of the PLA/PA11 blend was enhanced to a great extent by the PLA-g-MA prepared with the crosslinking agent.     

Effects of the shapes and addition amounts of crosslinking reagents on the properties of poly-3-hydroxybutyrate/poly(caprolactone) blends

The effects of the shapes and addition amount of crosslinking reagents on the expression mechanisms of polymer properties of poly(3-hydroxybutyrate) (PHB) and poly(caprolactone) (PCL) blends are investigated. A static tensile test is carried out on 60%PHB/40%PCL blends by adding liquid and solid crosslinking reagents, showing that the Young's modulus of the blends decrease with increasing effective peroxide value of the crosslinking reagent. In addition, the elasticity of the blends increases only when the liquid crosslinker is added, even though T₁H analysis and scanning electron microscopy observation reveal that both crosslinking reagents improve the miscibility of the blend. Furthermore, the ¹H and ¹³C PST-MAS NMR spectra related to the molecular motions of polymer main chains in the blends increase with increasing effective peroxide value of the crosslinking reagents. However, the local molecular motions of substituents in the blends matched with the T₁C values reveal an opposite trend between the rigid PHB and flexible PCL with the addition of the solid crosslinker. The solid-state NMR spectral and relaxation time analyses suggest the possibility of the polymer chain scission as a side reaction, as well as the occurrence of intra-domain crosslinking, both of which reduce the toughness of the blends containing the solid crosslinker.     

Effect of graphene loading on thermomechanical properties of poly(vinyl alcohol)/starch blend

Polymer nanocomposites based on poly(vinyl alcohol) (PVA)/starch blend and graphene were prepared by solution mixing and casting. Glycerol was used as a plasticizer and added in the starch dispersion. The uniform dispersion of graphene in water was achieved by using an Ultrasonicator Probe. The composites were characterized by FTIR, tensile properties, X‐ray diffraction (XRD), thermal analysis, and FE‐SEM studies. FTIR studies indicated probable hydrogen bonding interaction between the oxygen containing groups on graphene surface and the –OH groups in PVA and starch. Mechanical properties results showed that the optimum loading of graphene was 0.5 wt % in the blend. XRD studies indicated uniform dispersion of graphene in PVA/starch matrix upto 0.5 wt % loadings and further increase caused agglomeration. Thermal studies showed that the thermal stability of PVA increased and the crystallinity decreased in the presence of starch and graphene. FE‐SEM studies showed that incorporation of graphene increased the ductility of the composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41827.     

Natural weathering studies of biobased thermoplastic starch from agricultural waste/polypropylene blends

Thermoplastic starch (TPS) obtained from agricultural waste was blended with polypropylene (PP) for natural weathering studies. The agricultural waste material was obtained from seeds and tubers with a starch content of approximately 50%. Commercial‐grade TPS and native tapioca‐based TPS were also prepared for comparison. The biobased TPS/PP extruded sheets were exposed to natural weathering for six months and their deterioration in weight, tensile properties, thermal properties, and relative molecular weight were monitored. SEM micrographs revealed the formation of surface cracking and the presence of microorganisms. FTIR spectrum indicated an increase in the carbonyl index over time as a result of the formation of degradation products. TPS/PP blends made from agricultural waste showed a better resistance to natural weathering compared to the other high starch formulation. The higher starch content in the blend system encouraged the rapid degradation process due to the combined effect of UV radiation with oxidation, moisture, temperature, and microbial attack. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of the melt‐mixing condition on the physical property of poly(l‐lactic acid)/poly(d‐lactic acid) blends

The effect of the mixing condition in a mill‐type mixer on the thermal property and the crystal formation of the poly(l ‐lactide)/poly(d ‐lactide) blends is investigated. The blends melt‐mixed at 200 and 210 °C under application of a high shear flow tend to show a single melting peak of the stereocomplex crystal (SC) in the differential scanning calorimetry first and second heating processes without indicating the trace of the melting of homo‐chiral crystal. The mixing at an elevated temperature causes a serious thermal degradation. Further kneading of the blends at an elevated temperature higher than T_m of SC causes the transesterification between the same enatiomeric chains forming block copolymers of l ‐ and d ‐chains. This block copolymer acts as a nucleating agent of SC and the compatibilizing agent between poly(l ‐lactide) and poly(d ‐lactide) and promotes the formation of SC. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45489.     

Effect of the molecular weight on the plasticization properties of poly(hexane succinate) in poly(vinyl chloride) blends

Blends of poly(vinyl chloride) (PVC) and poly(hexane succinate) (PHS) with various molecular weights were analyzed with respect to their mechanical properties, durability, and thermal stability. We found that the molecular weight of PHS played an important role in the plasticizing process, and the single glass-transition temperature (T _g) of the PVC blends measured by dynamic mechanical analysis supported the complete miscibility between PHS and PVC. The plasticizing efficiency of PHS increased as the molecular weight increased; this reflected the gradually increasing elongation at break and the decreased T _g of the PVC blend. Meanwhile, the higher molecular weight of PHS also improved the resistance of migration and thermal stability but decreased the biodegradability of the PVC blends; this was due to the strong intermolecular interactions between PHS and PVC. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47081.     

Improving the toughening in poly(lactic acid)‐thermoplastic cassava starch reactive blends

Poly(lactic acid) (PLA), a physical blend of PLA and thermoplastic cassava starch (TPCS) (PLA‐TPCS), and reactive blends of PLA with TPCS using maleic anhydride as compatibilizer with two different peroxide initiators [i.e., 2,5‐bis(tert‐butylperoxy)‐2,5‐dimethylhexane (L101) and dicumyl peroxide (DCP)] PLA‐g‐TPCS‐L101 and PLA‐g‐TPCS‐DCP were produced and characterized. Blends were produced using either a mixer unit or twin‐screw extruder. Films for testing were produced by compression molding and cast film extrusion. Morphological, mechanical, thermomechanical, thermal, and optical properties of the samples were assessed. Blends produced with the twin‐screw extruder resulted in a better grade of mixing than blends produced with the mixer. Reactive compatibilization improved the interfacial adhesion of PLA and TPCS. Scanning electron microscopy images of the physical blend showed larger TPCS domains in the PLA matrix due to poor compatibilization. However, reactive blends revealed smaller TPCS domains and better interfacial adhesion of TPCS to the PLA matrix when DCP was used as initiator. Reactive blends exhibited high values for elongation at break without an improvement in tensile strength. PLA‐g‐TPCS‐DCP provides promising properties as a tougher biodegradable film. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46140.     

Effect of two different plasticizers on the properties of poly(3‐hydroxybutyrate) binary and ternary blends

Plasticized poly(3‐hydroxybutyrate) (PHB) films were obtained by solvent casting. The effects of two different additives on several properties of PHB have been examined, utilizing tributyrin and poly[di(ethyleneglycol) adipate] (A). Based on changes in the glass transition temperature (T_g) and cold crystallization temperature of host PHB, the two components are miscible with PHB and they can act as plasticizers. Binary and ternary blends were obtained by adding both plasticizers separately or together, respectively. The effect of plasticizer addition on the optical transparency, water vapor permeability, and tensile properties of the films was studied. It was found that the blends remain transparent and water vapor permeability was maintained constant until a 20 wt % of plasticizer content. Plasticizing effect was corroborated and it depended on the plasticizer percentage. Binary blends had an increased plasticity, in concordance with T_g diminution of PHB. Although ternary blends presented T_g diminution, mechanical properties were not improved probaby due to strong interactions between plasticizers. Finally, binary and ternary blends presented enhanced properties, causing an increment on processability. A correct knowledge between the formulation of the film and the role played by each component could allow getting custom films. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46016.     

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.     

Degradation of graft polymer and blend based on cellulose and poly(L‐lactide)

Degradable polymers were prepared by blending and graft polymerization of cellulose and poly(L‐lactide) (PLLA). The cellulose/poly(L‐lactide) blends and cellulose‐graft‐poly(L‐lactide) polymers were characterized by FTIR, NMR, DSC, and TGA. Wide‐angle X‐ray powder diffraction (WAXD) and degradation tests [by alkaline, phosphate‐buffered saline solution (PBS), and enzyme solution] showed changes in the crystalline structure as a result of degradation. The results indicated that blending and graft polymerization could affect crystallization of the polymers and promote the degradability. The polymers with low degree of crystallinity showed higher degradability. In contrast, enzyme, alkaline, and PBS degradated material decreased rate of polymers degradation. In addition, high levels of PLLA resulted in a decrease in degradation. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2257–2264, 2013