Water-Induced Breaking of Interfacial Cohesiveness in a Poly(lactic acid)/Miscanthus Fibers Biocomposite

The impact of the immersion in water on the morphology and the thermomechanical properties of a biocomposite made of a matrix of poly (lactic acid) (PLA) modified with an ethylene acrylate toughening agent, and reinforced with miscanthus fibers, has been investigated. Whereas no evidence of hydrolytic degradation has been found, the mechanical properties of the biocomposite have been weakened by the immersion. Scanning electron microscopy (SEM) pictures reveal that the water-induced degradation is mainly driven by the cracking of the fiber/matrix interface, suggesting that the cohesiveness is a preponderant factor to consider for the control of the biocomposite decomposition in aqueous environments. Interestingly, it is observed that the loss of mechanical properties is aggravated when the stereoregularity of PLA is the highest, and when increasing the degree of crystallinity. To investigate the influence of the annealing on the matrix behavior, crystallization at various temperatures has been performed on tensile bars of PLA made by additive manufacturing with an incomplete filling to enhance the contact area between water and polymer. While a clear fragilization occurs in the material crystallized at high temperature, PLA crystallized at low temperature better maintains its properties and even shows high elongation at break likely due to the low size of the spherulites in these annealing conditions. These results show that the tailoring of the mesoscale organization in biopolymers and biocomposites can help control their property evolution and possibly their degradation in water.

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Reinforcing abilities of microfibers and nanofibrillated cellulose in poly(lactic acid) composites

Science and Engineering of Composite Materials ◽

10.1515/secm-2016-0113 ◽

2018 ◽

Vol 25 (2) ◽

pp. 395-401 ◽

Cited By ~ 4

Author(s):

Supachok Tanpichai ◽

Jatuphorn Wootthikanokkhan

Keyword(s):

Mechanical Properties ◽

Lactic Acid ◽

Young’S Modulus ◽

High Speed ◽

Young's Modulus ◽

Nanofibrillated Cellulose ◽

Degree Of Crystallinity ◽

Poly Lactic Acid ◽

Regenerated Cellulose ◽

The Matrix

AbstractThe reinforcing abilities of cellulose microfibers and nanofibrillated cellulose (NFC) in poly(lactic acid) (PLA) were evaluated. NFC successfully prepared from regenerated cellulose fibers using high-speed blending for 60 min was introduced in a PLA matrix. The physical and mechanical properties of NFC-reinforced PLA composites were investigated in comparison with those of the composites with microfibers. NFC fibrils with diameters in the range of 100–500 nm were disintegrated from micron-sized regenerated fibers. A slight decrease in the degree of crystallinity and degradation temperature obtained for NFC after mechanical treatment was found compared with untreated microfibers. The introduction of NFC in the PLA effectively increased the tensile strength and Young’s modulus of the composites by 18% and 42%, respectively. The use of micron-sized fibers to reinforce PLA, on the other hand, showed a slight improvement in Young’s modulus (13%). The improvement in the mechanical properties of the composites reinforced with NFC was found because of the higher surface area of NFC and better interaction between the matrix and NFC fibrils. This allowed stress to transfer from the matrix to the reinforcement. NFC prepared using the high-speed blending could be an alternative to use as reinforcement in composites.

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Poly(Lactic Acid)–Poly(Butylene Succinate)–Sugar Beet Pulp Composites; Part I: Mechanics of Composites with Fine and Coarse Sugar Beet Pulp Particles

Polymers ◽

10.3390/polym13152531 ◽

2021 ◽

Vol 13 (15) ◽

pp. 2531

Author(s):

Rodion Kopitzky

Keyword(s):

Mechanical Properties ◽

Lactic Acid ◽

Sugar Beet ◽

Cell Structure ◽

Sugar Beet Pulp ◽

Poly Lactic Acid ◽

Butylene Succinate ◽

Fracture Patterns ◽

Beet Pulp ◽

The Impact

Sugar beet pulp (SBP) is a residue available in large quantities from the sugar industry, and can serve as a cost-effective bio-based and biodegradable filler for fully bio-based compounds based on bio-based polyesters. The heterogeneous cell structure of sugar beet suggests that the processing of SBP can affect the properties of the composite. An “Ultra-Rotor” type air turbulence mill was used to produce SBP particles of different sizes. These particles were processed in a twin-screw extruder with poly(lactic acid) (PLA) and poly(butylene succinate) (PBS) and fillers to granules for possible marketable formulations. Different screw designs, compatibilizers and the use of glycerol as a thermoplasticization agent for SBP were also tested. The spherical, cubic, or ellipsoidal-like shaped particles of SBP are not suitable for usage as a fiber-like reinforcement. In addition, the fineness of ground SBP affects the mechanical properties because (i) a high proportion of polar surfaces leads to poor compatibility, and (ii) due to the inner structure of the particulate matter, the strength of the composite is limited to the cohesive strength of compressed sugar-cell compartments of the SBP. The compatibilization of the polymer–matrix–particle interface can be achieved by using compatibilizers of different types. Scanning electron microscopy (SEM) fracture patterns show that the compatibilization can lead to both well-bonded particles and cohesive fracture patterns in the matrix. Nevertheless, the mechanical properties are limited by the impact and elongation behavior. Therefore, the applications of SBP-based composites must be well considered.

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Functionalized Cellulose Nanocrystals for Improving the Mechanical Properties of Poly(Lactic Acid)

Volume 12: Materials: Genetics to Structures ◽

10.1115/imece2018-87691 ◽

2018 ◽

Author(s):

Jamileh Shojaeiarani ◽

Dilpreet Bajwa

Keyword(s):

Mechanical Properties ◽

Lactic Acid ◽

Cellulose Nanocrystals ◽

Mechanical Test ◽

Poly Lactic Acid ◽

Injection Molding Process ◽

Molding Process ◽

Dynamic Mechanical ◽

Uniform Dispersion ◽

The Impact

Biopolymers are emerging materials with numerous capabilities of minimizing the environmental hazards caused by synthetic materials. The competitive mechanical properties of bio-based poly(lactic acid) (PLA) reinforced with cellulose nanocrystals (CNCs) have attracted a huge interest in improving the mechanical properties of the corresponding nanocomposites. To obtain optimal properties of PLA-CNC nanocomposites, the compatibility between PLA and CNCs needs to be improved through uniform dispersion of CNCs into PLA. The application of chemical surface functionalization technique is an essential step to improve the interaction between hydrophobic PLA and hydrophilic CNCs. In this study, a combination of a time-efficient esterification technique and masterbatch approach was used to improve the CNCs dispersibility in PLA. Nanocomposites reinforced by 1, 3, and 5 wt% functionalized CNCs were prepared using twin screw extrusion followed by injection molding process. The mechanical and dynamic mechanical properties of pure PLA and nanocomposites were studied through tensile, impact and dynamic mechanical analysis. The impact fractured surfaces were characterized using scanning electron microscopy. The mechanical test results exhibited that tensile strength and modulus of elasticity of nanocomposites improved by 70% and 11% upon addition of functionalized CNCs into pure PLA. The elongation at break and impact strength of nanocomposites exhibited 43% and 35% increase as compared to pure PLA. The rough and irregular fracture surface in nanocomposites confirmed the higher ductility in PLA nanocomposites as compared to pure PLA. The incorporation of functionalized CNCs into PLA resulted in an increase in storage modulus and a decrease in tan δ intensity which was more profound in nanocomposites reinforced with 3 wt% functionalized CNCs.

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Crystallization Kinetics of Poly(lactic acid)–Graphene Nanoscroll Nanocomposites: Role of Tubular, Planar, and Scrolled Carbon Nanoparticles

C – Journal of Carbon Research ◽

10.3390/c7040075 ◽

2021 ◽

Vol 7 (4) ◽

pp. 75

Author(s):

Oluwakemi Ajala ◽

Caroline Werther ◽

Rauf Mahmudzade ◽

Peyman Nikaeen ◽

Dilip Depan

Keyword(s):

Mechanical Properties ◽

Lactic Acid ◽

Crystallization Kinetics ◽

Crystallization Rate ◽

Melting Behavior ◽

Degree Of Crystallinity ◽

Poly Lactic Acid ◽

Avrami Model ◽

Superior Mechanical Properties ◽

Kinetics Of

Graphene nanoscrolls (GNS) are 1D carbon-based nanoparticles. In this study, they were investigated as a heterogeneous nucleating agent in the poly(lactic acid) (PLA) matrix. The isothermal and non-isothermal melting behavior and crystallization kinetics of PLA-GNS nanocomposites were investigated using a differential scanning calorimeter (DSC). Low GNS content not only accelerated the crystallization rate, but also the degree of crystallinity of PLA. The Avrami model was used to fit raw experimental data, and to evaluate the crystallization kinetics for both isothermal and non-isothermal runs through the nucleation and growth rate. Additionally, the effect of the dimensionality and structure of the nanoparticle on the crystallization behavior and kinetics of PLA is discussed. GNS, having a similar fundamental unit as CNT and GNP, were observed to possess superior mechanical properties when analyzed by the nanoindentation technique. The scrolled architecture of GNS facilitated a better interface and increased energy absorption with PLA compared to CNTs and GNPs, resulting in superior mechanical properties.

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Barrier Properties and Hydrophobicity of Biodegradable Poly(lactic acid) Composites Reinforced with Recycled Chinese Spirits Distiller’s Grains

Polymers ◽

10.3390/polym13172861 ◽

2021 ◽

Vol 13 (17) ◽

pp. 2861

Author(s):

Zhi-Jun Chen ◽

Chi-Hui Tsou ◽

Meng-Lin Tsai ◽

Jipeng Guo ◽

Manuel Reyes De Guzman ◽

...

Keyword(s):

Mechanical Properties ◽

Lactic Acid ◽

Barrier Properties ◽

Poly Lactic Acid ◽

Control Group ◽

Scanning Calorimetry ◽

Melt Mixing ◽

Distiller's Grains ◽

The Matrix ◽

Section Structure

Adding natural biomass to poly(lactic acid) (PLA) as a reinforcing filler is a way to change the properties of PLA. This paper is about preparing PLA/biomass composites by physically melting and blending Chinese Spirits distiller’s grains (CSDG) biomass and PLA to optimize the composite performance. Composites of modified PLA (MPLA) with varying amounts of CSDG were also prepared by the melt-mixing method, and unmodified PLA/CSDG composites were used as a control group for comparative analysis. The functional groups of MPLA enhanced the compatibility between the polymer substrate and CSDG. The composite water vapor/oxygen barrier and mechanical properties were studied. It was found that the barrier and mechanical properties of MPLA/CSDG composites were significantly improved. SEM was adopted to examine the tensile section structure of the composites, and the compatibility between the filler and the matrix was analyzed. An appropriate amount of CSDG had a better dispersibility in the matrix, and it further improved the interfacial bonding force, which in turn improved the composite mechanical properties. X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry were conducted to determine the crystalline properties and to analyze the stability of the composites. It was found that the CSDG content had a significant effect on the crystallinity. Barrier and biodegradation mechanisms were also discussed.

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Effect of various enzymatic treatments on the mechanical properties of coir fiber/poly(lactic acid) biocomposites

Journal of Thermoplastic Composite Materials ◽

10.1177/0892705719864618 ◽

2019 ◽

pp. 089270571986461

Author(s):

Kubra Coskun ◽

Aysenur Mutlu ◽

Mehmet Dogan ◽

Ebru Bozacı

Keyword(s):

Mechanical Properties ◽

Lactic Acid ◽

Mechanical Performance ◽

Mechanical Analysis ◽

Poly Lactic Acid ◽

Coir Fiber ◽

Test Results ◽

Fiber Reinforced ◽

Remarkable Effect ◽

The Impact

The effects of enzymatic treatments on the properties of coir fiber-reinforced poly(lactic acid) (PLA) were not found in the literature. Accordingly, the effects of various enzymatic treatments on the mechanical performance of the coir fiber-reinforced PLA composites were investigated in the current study. Four different enzymes, namely lipase, lactase, pectinase, and cellulase, were used. The mechanical properties of the composites were determined by the tensile, flexural, impact tests, and dynamic mechanical analysis. According to the test results, the use of enzyme treated coir fibers affected the mechanical properties except for the flexural properties with different extents depending upon their type. The tensile strength increased with the treatments of lipase and lactase, while the treatments with pectinase and cellulase had no remarkable effect. The impact strength was improved with enzymatic treatments except for pectinase. All enzymatic treatments improved the elastic modulus below the glass transition temperature. In brief, enzymatic treatments improved the interfacial adhesion between coir fiber and PLA via the waxes and fatty acids removal and/or the increment in surface roughness.

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Properties of Poly(Lactic Acid) Filled with Hydrophobic Cellulose/SiO2 Composites

International Journal of Polymer Science ◽

10.1155/2019/7835172 ◽

2019 ◽

Vol 2019 ◽

pp. 1-8 ◽

Cited By ~ 7

Author(s):

Kittithorn Lertphirun ◽

Kawee Srikulkit

Keyword(s):

Mechanical Properties ◽

Lactic Acid ◽

Hydrolytic Degradation ◽

Poly Lactic Acid ◽

Twin Screw Extruder ◽

Screw Extruder ◽

Twin Screw ◽

Hydrolysis Of Cellulose ◽

One Step ◽

Hydrolysis Of

Hydrophobic cellulose/SiO2 composites were prepared. Resultant hydrophobic cellulose/SiO2 composites were melt mixed with PLA using a twin-screw extruder to obtain 10 wt% masterbatch. Again, 10 wt% masterbatch was melt mixed with virgin PLA, resulting in PLA containing hydrophobic cellulose/SiO2 at various contents (1 wt%, 3 wt%, and 5 wt%) using a twin-screw extruder (barrel zone temperature: 150/160/170/180/190°C (die zone)). Injection-molded samples were prepared for mechanical properties evaluation. Results showed that poor mechanical properties found at low percent loadings were associated with a significant depolymerization of masterbatch composition due to twice thermal treatments. Note that 10 wt% masterbatch was subjected to injection molding straight away in a one-step process. Results showed that 10 wt% hydrophobic cellulose/SiO2/PLA composites exhibited mechanical properties equivalent to neat PLA. Importantly, the addition of hydrophobic cellulose/SiO2 at high percent loading could favor landfill degradation of PLA via water absorption ability of cellulose. It was expected that enzymatic hydrolysis of cellulose resulted in the formation of lactic acid and silicic acid which consequently catalyzed the hydrolytic degradation (acid hydrolysis) of PLA. The hydrolytic degradation produced carboxylic acid end group which further accelerated the degradation rate.

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Poly(lactic acid)/polypropylene and compatibilized poly(lactic acid)/polypropylene blends prepared by a vane extruder: analysis of the mechanical properties, morphology and thermal behavior

Journal of Polymer Engineering ◽

10.1515/polyeng-2014-0312 ◽

2015 ◽

Vol 35 (8) ◽

pp. 753-764 ◽

Cited By ~ 3

Author(s):

Rong-yuan Chen ◽

Wei Zou ◽

Hai-chen Zhang ◽

Gui-zhen Zhang ◽

Zhi-tao Yang ◽

...

Keyword(s):

Mechanical Properties ◽

Lactic Acid ◽

Thermal Resistance ◽

Flexural Modulus ◽

Weight Fraction ◽

Poly Lactic Acid ◽

Scanning Calorimetry ◽

Crystallization Property ◽

The Matrix ◽

Pp Blends

Abstract Poly(lactic acid) (PLA)/polypropylene (PP) blends with different weight fractions were prepared by a novel vane extruder. The mechanical properties, morphology, crystallization behavior and thermal stability of the blends were investigated. The tensile strength, flexural strength and elongation at break decreased nonlinearly when the PP content was not more than 50 wt% and then increased with an increase in the PP content. The flexural modulus decreased with increasing PP weight fraction. The PLA/PP 90:10 blend exhibited the optimum impact strength. Scanning electron microscopy measurements revealed that the PLA/PP blends were immiscible. Phase separation occurred significantly at a blend ratio of 50:50. Regarding the PLA/PP 90:10 blend, the mean diameter of the disperse-phase PP particles was the smallest at 1.11 μm. Differential scanning calorimetry measurements showed that low content of PP enhanced the crystallization of PLA. The PLA component in the blends impeded the crystallization of PP when PP was used as the matrix. The thermogravimetric analysis measurement involved a two-step decomposition process of the blends. The thermal resistance of the blends was improved by compounding with PP. As compatibilizers, both the maleic anhydride-grafted PP and the ethylene/n-butyl acrylate/glycidyl methacrylate terpolymer helped improve the mechanical properties, crystallization property and thermal resistance of the PLA/PP blends.

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Effects of Poly(Methyl Methacrylate)-Encapsulated Nanosilica on Mechanical Properties of Poly(Lactic Acid)/Ethylene Vinyl Acetate Nanocomposites

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.773.51 ◽

2018 ◽

Vol 773 ◽

pp. 51-55

Author(s):

Jasmine Pongkasem ◽

Saowaroj Chuayjuljit ◽

Phasawat Chaiwutthinan ◽

Amnouy Larpkasemsuk ◽

Anyaporn Boonmahitthisud

Keyword(s):

Mechanical Properties ◽

Lactic Acid ◽

Impact Strength ◽

Methyl Methacrylate ◽

Tensile Properties ◽

Vinyl Acetate ◽

Ethylene Vinyl Acetate ◽

Poly Lactic Acid ◽

Poly Methyl Methacrylate ◽

The Impact

In this study, poly(lactic acid) (PLA) was melt mixed with three weight percentages (10–30wt%) of ethylene vinyl acetate copolymer (EVA) in an internal mixer, followed by a compression molding. According to a better combination of mechanical properties, the 90/10 (w/w) PLA/EVA was selected for preparing hybrid nanocomposites with three loadings (1, 3 and 5 parts per hundred of resin , phr) of poly(methyl methacrylate)-encapsulated nanosilica (PMMA-nSiO2). The nanolatex of PMMA-nSiO2 was synthesized via in situ differential microemulsion polymerization. The obtained PMMA-nSiO2 showed a core-shell morphology with nSiO2 as a core and PMMA as a shell, having an average diameter of 43.4nm. The influences of the EVA and PMMA-nSiO2 on the impact strength and the tensile properties of the PLA/EVA nanocomposites were studied and compared. It is found that the impact strength and the tensile properties of the 90/10 (w/w) PLA/EVA were improved with the appropriate amounts of the EVA and PMMA-nSiO2.

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The Study on the Mechanical Properties of Poly(lactic acid)/Straw Fiber Composites

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.200.312 ◽

2012 ◽

Vol 200 ◽

pp. 312-315

Author(s):

Ping Zhang ◽

Bing Tao Wang ◽

De Gao ◽

Li Hua Wen

Keyword(s):

Mechanical Properties ◽

Lactic Acid ◽

Mechanical Characteristics ◽

Raw Materials ◽

Fiber Composites ◽

Poly Lactic Acid ◽

Corn Straw ◽

Renewable Raw Materials ◽

Pre Treatment ◽

The Impact

The paper describes the production and the mechanical characteristics of composites made completely from renewable raw materials, the corn straw fiber and the biodegradable plastic, poly(lactic acid). The effect of straw fiber content on the mechanical properties of the composites was studied and the optimum mass fraction was 15%. To enhance the mechanical properties of the composites, two different methods were tested. Maleic anhydride as the compatilizer was introduced into the composites but the changes of the mechanical properties were small. While the other method, pre-treatment for straw fiber before blending, the mechanical properties increased obviously. The tensile strength and the impact strength were 35.6 MPa and 1.67 kJ/m2, respectively.

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