PLA Blends Research Articles

Biodegradable package films of poly(L-Lactic) acid/extracted gelatin blend from white leather fibers

In food packaging area, the substantial utilization of synthetic plastics has a huge environmental impact and there is necessitate really for more biodegradable packaging materials. Blending of poly (lactic acid) (PLA) and extracted gelatin (EG) was investigated as prospective replacements for non-degradable petrochemical polymers. EG is a biopolymer extracted from white leather fibers wastes in the leather industry after alkaline hydrolysis. Both polymers need modification for food packaging requirements. PLA films are very brittle and gelatin is sensitive to water and the properties of its films are reliant on the moisture content with low mechanical strength. An investigation on the blending of PLA and EG films gives better properties more suitable for packaging depending on their paired characteristics. The resulting biodegradable films were characterized using by FTIR, SEM, TGA/DTA, and simulated soil burial respirometric testing. The properties of some characteristics of PLA and EG blends in terms of mechanical and thermal properties have been discussed as biodegradable packaging films. It was found that the addition of 30 wt % of EG offering blended films with good thermal processability, transparency and flexibility, as well as films with good mechanical.

Compatibility improvement of poly(lactic acid)/thermoplastic starch blown films using acetylated starch

AbstractThe present research aims to improve the compatibility between relatively hydrophobic poly(lactic acid) (PLA) and hydrophilic thermoplastic starch (TPS) and the properties of the PLA/TPS blends by replacing TPS from native cassava starch (TPSN) with TPS from acetylated starch (TPSA). The effects of the degree of acetylation (DA) of acetylated starch, that is, 0.021, 0.031, and 0.074, on the morphological characteristics and properties of PLA/TPS blend are investigated. The melt blends of PLA and TPS with a weight proportion of PLA:TPS of 50:50 are fabricated and then blown into films. Scanning electron microscopy confirms the dispersion of TPS phase in the PLA matrix. Better dispersion and smaller size of the TPS phase are observed for the PLA/TPSA blend films with low DA of acetylated starch, resulting in improved tensile and barrier properties and increased storage modulus, thermal stability, and Tg, Tcc, and Tm of PLA. Elongation at break of the PLA/TPSA blend increases up to 57%, whereas its water vapor permeability and oxygen permeability decrease about 15%. The obtained PLA/TPSA blend films have the potential to be applied as biodegradable flexible packaging.

Nonisothermal Crystallization Kinetics of Polylactic Acid under the Influence of Polyolefin Elastomers

Crystallization kinetics of various blends of poly(lactic acid) (PLA)/polyolefin elastomer (POE) was studied through nonisothermal experimental investigations and theoretical approaches. The PLA/POE blends were prepared in a melt mixing process by using two types of POEs and compatibilizers. The rubber phases used were adopted on the basis of polyethylene (PE) and polypropylene (PP) type olefin elastomers. The effects of two kinds of compatibilizers containing ethylene vinyl acetate copolymer (EVA) and ethylene acrylic ester-glycidyl methacrylate terpolymer (EGMA) on the morphology and various parameters of crystallization of PLA were investigated using scanning electron microscopy (SEM) and differential scanning calorimeter (DSC) measurements, respectively. The morphology investigations on PLA blends containing PP based olefin elastomers showed that the introduction of EGMA compatibilizer into the matrix led to a more than 100% reduction in the size of the rubber droplets. The experimental measurements of crystallization behavior of various PLA/POE blends showed that the POEs and compatibilizers could cause a fall in the initial crystallization temperature more than 13 °C. The theoretical approaches used for studying the kinetics of crystallization of PLA in the presence of various POEs and compatibilizers indicated a decrease in the crystallinity of PLA and a 64% reduction in the activation energy compared to the neat PLA. The results suggest that the largest variation in the crystallization kinetic parameters of PLA was resulted from the PP based olefin elastomer and EGMA compatibilizer.

Supertough and Transparent Poly(lactic acid) Nanostructure Blends with Minimal Stiffness Loss.

This contribution is an attempt to explore the effectiveness of a series of newly obtained thermoplastic elastomers (TPEs) as a toughening agent for modifying poly(lactic acid) (PLA). The TPEs, including ionically modified isotactic polypropylene-graft-PLA (iPP-g-PLA) copolymers with explicit graft length, graft density, and ionic group content, and an iPP-g-PLA copolymer with a very high molecular weight and explicit graft density, were elaborately designed and synthesized. The semicrystal or rubbery copolymer backbone originated from iPP was designed to improve the toughness and maintain a relatively high strength, while the grafted PLA side chain was to ensure a high level of compatibility with the PLA matrix. To obtain further enhancement in interfacial reinforcement, the imidazolium-based ionic group was also added during graft onto reaction. All of these graft copolymers were identified with randomly distributed PLA branches, bearing a very high molecular weight ((33–398) × 104) and very high PLA content (57.3–89.3 wt %). Unprecedentedly, with a very small amount of newly designed TPE, the modified PLA blends exhibited a significantly increased elongation at break (up to about 190%) and simultaneously retained the very high stiffness and excellent transparency. The nanometer-scale phase-separated particles with good compatibility and refractive index matching to the PLA matrix were demonstrated to play a crucial role in the excellent performance. The findings suggested that the newly designed iPP-g-PLA copolymers are very economic, promising, and effective modifying agents for developing highly transparent and tough PLA-based sustainable materials.

Correlative analysis between solid-state NMR and morphology for blends of poly(lactic acid) and poly(butylene adipate-co-butylene terephthalate)

Morphological changes in polymer blending process were investigated using integrated analyses by solid-state NMR and magnetic relaxation. The study examined previous reported mechanical properties of polymer blends incorporating poly(lactic acid) (PLA) and poly(butylene adipate-co-butylene terephthalate) (PBAT) over a range of compositions, along with a crosslinking reagent. The X-ray diffraction (XRD) and the differential scanning calorimeter (DSC) results showed that the crystallinity of PLA decreased with increasing the PBAT content. According to the integrated analysis data and imaging by micro-focus X-ray computed tomography (CT), polymer tensile properties were dominated by interfacial affinity between the molecular mobilities of PLA and PBAT; depending on the blending ratio, the polymer morphology changed from a discontinuous “sea-island” form to a bicontinuous morphology. Addition of a crosslinking reagent was observed via X-ray CT to homogenize the PLA and PBAT blend at the micron length scale, even though both polymers were still heterogeneous at the nanoscale as elucidated by NMR analysis. As well as the morphological change in micro scale, the molecular mobility changes of the total polymer blend system, which could be evaluated by the integrated solid-state NMR analyses, brought about greater elongation at the break point in dynamic tensile testing.

Renewable malic acid-based plasticizers for both PVC and PLA polymers

Acetylated malic acid alkyl esters (AcMAE-Cn) with different alkyl chain lengths, as alternative plasticizers for both poly(vinyl chloride) (PVC) and poly(lactic acid) (PLA), were synthesized by the esterification of renewable malic acid with alcohols and subsequent acetylation. The molecular structure of the synthesized plasticizers was confirmed using 1H NMR and FT-IR spectroscopy. PVC or PLA blends containing 50phr of the plasticizers were evaluated by dynamic mechanical analysis (DMA), tensile testing, and migration testing to evaluate the plasticization efficiency. The plasticized PVC films presented good plasticizing performance, as demonstrated by the results of tensile and migration testing and the Tg values (as determined by DMA). Among the plasticizers, AcMAE-C6 and AcMAE-C8 presented enhanced plasticizing performance compared with that of the commercial dioctyl adipate (DOA) and di(2-ethylhexyl) phthalate (DEHP) plasticizers. Additionally, the plasticizing properties of the plasticized PLA films depend significantly on the structure of the plasticizers. It was found that plasticizers (AcMAE-C4 and AcMAE-C6) bearing short alkyl groups (n-butyl and n-hexyl, respectively) may act as excellent plasticizers. In summary, the AcMAE-C6 plasticizer showed potential as an alternative plasticizer for both PVC and PLA polymers.

Study on flexural and tensile behavior of PLA, ABS and PLA-ABS materials

In recent years, additive manufacturing process has found various applications in many industrial as well as commercial sectors. ABS and PLA are the most commonly used filaments in 3D printing. Although both of them provide high quality materials in their own ways, their resistance to stresses are not of industrial standards. 3D printed materials are always considered to be fragile and required to be given care. So, in order to present with a new filament material which can withstand higher stresses as compared to the conventional filaments, blends of PLA and ABS are produced in various compositions (20% ABS and 80% PLA; 50% ABS and 50% PLA; 80% ABS and 20% PLA) and they are tested for their resistance against tensile and flexural loads. Specimens with the above compositions are printed in accordance with ASTM geometry considering the ASTM standards. The UTS data for various combinations are established. The UTS data are then cross-indexed with the result of the flexural test. Results are compared to the properties of normal ABS and PLA and observed that the blend materials outperformed pure ABS and PLA by a marginal amount. Thus, implementation of this filament material in 3D printing applications can ensure products with higher resistance to stresses.

Evaluation of the Suitability of Poly(Lactide)/Poly(Butylene-Adipate-co-Terephthalate) Blown Films for Chilled and Frozen Food Packaging Applications.

The use of biopolymers can reduce the environmental impact generated by plastic materials. Among biopolymers, blends made of poly(lactide) (PLA) and poly(butylene-adipate-co-terephthalate) (PBAT) prove to have adequate performances for food packaging applications. Therefore, the present work deals with the production and the characterization of blown films based on PLA and PBAT blends in a wide range of compositions, in order to evaluate their suitability as chilled and frozen food packaging materials, thus extending their range of applications. The blends were fully characterized: they showed the typical two-phase structure, with a morphology varying from fibrillar to globular in accordance with their viscosity ratio. The increase of PBAT content in the blends led to a decrease of the barrier properties to oxygen and water vapor, and to an increase of the toughness of the films. The mechanical properties of the most ductile blends were also evaluated at 4 °C and −25 °C. The decrease in temperature caused an increase of the stiffness and a decrease of the ductility of the films to a different extent, depending upon the blend composition. The blend with 40% of PLA revealed to be a good candidate for chilled food packaging applications, while the blend with a PLA content of 20% revealed to be the best composition as frozen food packaging material.

Optimization of Biodegradable PLA/PCL Microspheres Preparation as Controlled Drug Delivery Carrier

Abstract In this paper, microspheres were prepared as controlled drug delivery carrier. Microspheres were prepared using o/w emulsification method. The core materials of microspheres were polyblend of poly(lactic acid) (PLA) and poly(ɛ-caprolactone) (PCL) with the composition of 60:40 using Span 80 as an emulsifier. PLA and PCL were dissolved into dichloromethane then emulsified and dispersed into water to form microspheres. The sizes and uniformity of microspheres can be influenced by emulsifier volume and dispersion stirring time. This study observes the appearance, texture, physical sizes, and distribution of microspheres particle sizes at various volumes of Span 80 and dispersion stirring time. The blend of PLA and PCL was only formed through physical interaction between them. The appearance and physical sizes of microspheres were observed by optical microscope, and the distribution sizes of the microsphere can be determined by PSA, the further analysis through SEM to observe the surface texture and also to know more the influence of dispersion stirring time to the size and uniformity of microsphere. It obtains that at volume 4 mL of Span 80 with dispersion stirring time of 30 minutes showing the small sizes and more uniform as well as just fewer microspheres were broken

Multifunctional PLA Blends Containing Chitosan Mediated Silver Nanoparticles: Thermal, Mechanical, Antibacterial, and Degradation Properties.

Poly(lactic acid) (PLA) is one of the most commonly employed synthetic biopolymers for facing plastic waste problems. Despite its numerous strengths, its inherent brittleness, low toughness, and thermal stability, as well as a relatively slow crystallization rate represent some limiting properties when packaging is its final intended application. In the present work, silver nanoparticles obtained from a facile and green synthesis method, mediated with chitosan as a reducing and stabilizing agent, have been introduced in the oligomeric lactic acid (OLA) plasticized PLA in order to obtain nanocomposites with enhanced properties to find potential application as antibacterial food packaging materials. In this way, the green character of the matrix and plasticizer was preserved by using an eco-friendly synthesis protocol of the nanofiller. The X-ray diffraction (XRD) and differential scanning calorimetry (DSC) results proved the modification of the crystalline structure as well as the crystallinity of the pristine matrix when chitosan mediated silver nanoparticles (AgCH-NPs) were present. The final effect over the thermal stability, mechanical properties, degradation under composting conditions, and antimicrobial behavior when AgCH-NPs were added to the neat plasticized PLA matrix was also investigated. The obtained results revealed interesting properties of the final nanocomposites to be applied as materials for the targeted application.

The use of low cost, abundant, homopolymers for engineering degradable polymer blends: Compatibilization of poly(lactic acid)/styrenics using poly(methyl methacrylate)

Using known parameters for the surface and interfacial tension, the work of adhesion of PMMA with PLA and styrenic polymers has been calculated. The results indicated that PMMA, an abundant and economical homopolymer, could serve as an effective compatibilizer, rivaling complex and costly block copolymers for PLA/styrenic blends. Blends of PLA with either SAN or ABS were produced with added 1%–10% PMMA. Tensile and impact toughness data show that the blends display properties comparable to those of PP with only 4% added PMMA. Deuterated-secondary ion mass spectrometry (DSIMS) performed with deuterated PMMA indicated that this corresponded to the formation of an interfacial layer approximately 2Rg thick, as the optimal thickness for integrating two polymers, without the formation of a third brittle layer. Blends with ABS showed an increase of nearly 300% in impact toughness compared to that for polymer containing no PMMA, while blends with SAN formed ideal extruded filaments, which produced 3-D printed structures at least 58% stronger and more ductile than molded PS.

Toward Fully Bio-based and Supertough PLA Blends via in Situ Formation of Cross-Linked Biopolyamide Continuity Network

Dynamic vulcanization has been demonstrated to be a versatile and efficient way of improving impact toughness of PLA. However, the existing vulcanization routes usually suffer from complicated presynthetic procedures and use of nonrenewable modifiers as well as markedly enhanced melt-viscosity. Herein, using both biomass-derived hydrogenated dimer acid (HDA) and an excess molar amount of l-lysine ethyl ester diisocyanate (LDI) as toughening monomers, we have developed a facile yet highly effective diisocyanate method for the design of fully bio-based PLA blends with excellent impact toughness and melt-flowability. The in situ formation and self-cross-linking of flexible biopolyamide (HDAPA) toughener, as well as its reactive compatibilization with PLA, were accomplished in a single melt-blending step. When incorporating the amount of HDAPA from 15 to 20 wt % or higher, the resulting blends evolved from the network-like morphology to the bi-continuous one with the cross-linked HDAPA network. At HDAPA content higher than 10 wt %, a sharp and persistent brittle–ductile transition occurred with an equilibrium impact strength of over 1200 J/m, and elongation-at-break was over 400%. Moreover, such a tremendous toughening effect was accompanied by low melt-viscosity and enhanced PLA crystallization. The matrix yielding triggered by internal cavitation of percolated HDAPA domains, together with the pull-out of many in situ formed block copolymers located at the interfaces, was found to be the major impact-toughening mechanism. This work offers a novel and facile strategy for fabricating high-performance and fully bio-based polymeric materials.

Mechanical, rheological and anaerobic biodegradation behavior of a Poly(lactic acid) blend containing a Poly(lactic acid)-co-poly(glycolic acid) copolymer

The goal of this work is to examine the thermal, rheological, mechanical and thermophilic anaerobic biodegradation performance of PLA blends containing a highly degradable polymer. Here random copolymers consisting of Poly(l-lactic acid) (PLLA) and Poly(glycolic acid) (PGA) structural units (75:25 M ratio) were synthesized at three different molecular weights (Mw = 16, 58 and 113 kg mol−1) and melt blended with a high molecular weight PLA homopolymer. The glass transition temperature (Tg) of poly(lactic acid-co-glycolic acid) (PLGA) was lower than that of PLA and increased with copolymer molecular weight. A single Tg intermediate to that of the two blend constituents was observed suggesting miscibility. Polymer blends showed enhanced methane production at early stages of anaerobic degradation with the rate increasing with increasing PLGA content and decreasing PLGA molecular weight. Blends exhibited a decrease in modulus and tensile strength as compared to pure PLA. Likewise, a decrease in ductility for all but the lowest molecular weight copolymer containing blend was observed. The zero-shear viscosity of polymer blends scaled predictably with PLGA content and exhibited reduced sensitivity to shear-rate. It is envisioned that this strategy could be applied for those applications where recycling is prohibitive such as at universities, hospitals and stadiums where mixed waste streams containing plastics and other waste types, such as food and paper, can be anaerobically co-digested and the resulting biogas used as fuel.

Effects of compatibilizer on the mechanical, rheological, and shape memory behaviors of poly(lactic acid) and poly(MnBM) blends

ABSTRACTThe effects of compatibilizer on the morphological, mechanical, rheological, and shape memory properties of poly(lactic acid) (PLA) and poly(methyl methacrylate‐block‐n‐butyl acrylate‐block‐methyl methacrylate) (Poly(MnBM)) (80/20) blend were investigated. From the morphological results, the addition of 1 wt% SAN‐MAH as a compatibilizer showed minimum Poly(MnBM) domain size among the blends with the SAN‐MAH in the amounts from 0 to 7 wt%. Tensile and flexural strengths, and complex viscosity of the blends showed maximum when the SAN‐MAH content was 1 wt%, which suggested the increased compatibility between the PLA and Poly(MnBM) phases. From the above results, the optimum compatibilizer content of the PLA and Poly(MnBM) blend was 1 wt%. The recovery ratio of tensile energy was found to be 83 and 56% for the PLA/Poly(MnBM) blend with and without the SAN‐MAH (1 wt%), respectively. Upon blending the PLA and Poly(MnBM) (80/20) with SAN‐MAH (1 wt%), the increase of recovered tensile energy was observed, and that the brittleness of PLA was improved to be ductile which resulted an improved shape memory behavior of the blend. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48591.

Improvement of Poly(Lactic Acid) Properties by Using Acrylonitrile-Butadiene Rubber and Polyethylene-g-Maleic Anhydride

This research prepared poly(lactic acid) (PLA) and PLA/acrylonitrile-butadiene rubber (NBR) blends before and after adding polyethylene-g-maleic anhydride with 3 wt% of maleic anhydride (PE-g-MA3) 3 phr. The effects of NBR and PE-g-MA3 on morphological, mechanical and thermal properties of PLA and PLA blends were discussed. The morphological analysis observed the two-phase morphology of PLA/NBR blends, and it was observed the cavities generated due to NBR phase detachment during sample fracture, and droplets of NBR phase at higher NBR content. The PE-g-MA3 addition could improve adhesion between PLA and NBR phases due to the decrease of cavities in PLA matrix and droplet size of NBR. The mechanical properties showed the impact strength and strain at break of PLA/NBR blends dramatically increased when the amount of NBR increasing. The addition of PE-g-MA3 significantly improved the impact strength of PLA/NBR blends. The thermal properties showed the NBR addition had effect slightly on the melting temperature of PLA/NBR blends. The filling of NBR and PE-g-MA3 greatly decreased the percent crystallinity of PLA more than two times. The thermal degradation of pure PLA and NBR proceeds by one step, while the thermal degradation process of PLA/NBR and PLA/PE-g-MA3 proceeds by two steps. Which the first step showed a large mass loss of PLA degradation and the second step showed a small mass loss of PE-g-MA and NBR degradation.

Morphology, Mechanical and Thermal Properties of Poly(Lactic Acid)/Propylene-Ethylene Copolymer/Cellulose Composites

This work studied the effects of various types of cellulose fibers on the morphology, mechanical and thermal properties of poly(lactic acid) (PLA)/propylene-ethylene copolymer (PEC) (90/10 w/w) blends. The PLA/PEC blends before and after adding cellulose fibers were prepared by melt blending method in the internal mixer and molded by compression method. The morphological analysis observed that the presence of cellulose in PLA did not change the phase morphology of PLA, and PLA/cellulose composite surfaces were observed the cellulose fibers inserted in PLA matrix and fiber pull-out. The phase morphology of PLA/PEC blends was changed from brittle fracture to ductile fracture behavior and showed the phase separation between PLA and PEC phases. The presence of celluloses did not improve the compatibility between PLA and PEC phases. The tensile stress and strain curves found that the tensile stress of PLA was the highest value. The addition of all celluloses increased Young’s modulus of PLA. The PEC presence increased the tensile strain of PLA over two times when compared with neat PLA and PLA was toughened by PEC. The incorporation of cellulose fibers in PLA/PEC blends could improve Young’s modulus, tensile strength, and stress at break of the blends. The thermal stability showed that the degradation temperatures of all types of cellulose were less than the degradation temperatures of PLA. Thus, the incorporation of cellulose in PLA could not enhance the thermal stability of PLA composites and PLA/PEC composites. The degradation temperature of PEC was the highest value, but it could not improve the thermal stability of PLA. The incorporation of cellulose fibers had no effect on the melting temperature of the PLA blend and composites.

Experimental evaluation of the mechanical and thermal properties of 3D printed PLA and its composites

In this study, the mechanical and thermal properties of 3D printed Poly (lactic-acid) (PLA) and its composites are experimentally evaluated. The specimens were prepared using the Makerbot Replicator + through Fused Deposition modelling (FDM). This study primarily focus on developing a polymer based material which is safer and cleaner for various engineering/domestic applications where reusability is usually minimum. Initially, adopting ASTM D-638 standards a comparative study was performed to assess the mechanical strengths of pure polymers such as PLA, Acrylonitrile Butadiene Styrene (ABS), Glycol modified Polyethylene teraphthalate (PET-G) and Polycarbonate (PC). Further, the study was extended to the composites of PLA like PLA + 30% nylon glass fibers, PLA + 10% carbon fibers and PLA + PET-G polymer blend, as well. Meanwhile, experimentation to assess the thermal properties like, thermal degradation temperature, glass transition temperature, melting temperature and crystallization temperature were also performed through Thermo-Gravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) tests. The results from this study reveal that in contrast to non-biodegradable ABS and PC, superior mechanical properties were displayed by PLA. Further, the polymer blend of PLA + PET-G would be an optimal choice where mechanical strength and thermal properties are of equal concern. Meanwhile, PLA + 30% glass fibers can provide excellent thermal stability and can be used where primary importance is given for thermal stability over mechanical strength. Therefore, it can be concluded that along with these advantages, the biodegradable nature of PLA justifies the cause of using these materials for the intended applications without harming human health and reducing pollution to a great extent.

Rheological, thermal and mechanical properties of biodegradable poly(lactic acid)/poly(butylene adipate-co-terephthalate)/poly(propylene carbonate) polyurethane trinary blown films

Poly(lactic acid) (PLA), poly(butylene adipate-co-terephthalate) (PBAT) and poly(propylene carbonate) polyurethane (PPCU) were blended by using a twin-screw extruder, and then, the PLA/PBAT/PPCU trinary blends were made into films via the blown film technique. The PLA/PBAT/PPCU blends were characterized by dynamic rheometer and differential scanning calorimetry (DSC). From the analysis of DSC, it indicated that the glass transition temperature (Tg) of PBAT and PPCU was increased and the glass transition temperature (Tg) of PLA was decreased with increasing PPCU content. PPCU could improve miscibility among PLA, PBAT and PPCU. The tests of mechanical showed that the elongation at break of PLA/PBAT/PPCU films decreased from 240 to 226% in the machine direction and from 413 to 353% in the transverse direction. The tensile strength was increased in the machine direction from 40.2 to 46.5 MPa in the machine direction and from 28.5 to 42.8 MPa in the transverse direction. The tear strength was from 1334.7 to 143.6 kN/m in the machine direction and from 137.3 to 147.8 kN/m in the transverse direction. PBAT was a good toughening agent for PLA, and PPCU was a compatibilizer for PBAT and PLA blends.

Atomic-scale and experimental investigation on the micro-structures and mechanical properties of PLA blending with CMC for additive manufacturing

As one of the most promising biodegradable material, poly(lactic acid) (PLA) is widely used for 3D printing bone scaffolds. However, the inflammation resulted by the intermediate product (lactic acid) of PLA degradation and poor cell affinity still pose a challenge. Blending PLA with o-carboxymethyl chitosan (CMC) is a proven method to achieve a better cell affinity and mechanical behavior material. This study applied a molecular dynamics simulation combining experimental method to investigate the micro-structures and mechanical properties of PLA/CMC composites. Composites were prepared by fused mixing process and extruded into filaments for FDM printing. Results show that the addition of CMC largely reduces the fractional free volume and the molecular chain motion capability, and results a higher density and better hydrophilic system. Interestingly, the tensile modulus increases as the concentration of CMC increases, indicating the introduction of CMC could enhance the stiffness of PLA. While, the tensile strength first increases and then decreases with the increase of CMC content, and 8PLA/2CMC owns the largest tensile strength. Finally, the root reason for these phenomena was found to be attributed to the stronger intermolecular interaction of CMC, the stronger interaction would result the aggregation behavior of CMC.

Nucleation of Poly(lactide) on the Surface of Different Fibers

The nucleation process of poly(lactide) (PLA) on a series of fibers was studied by means of in situ polarized optical microscope during crystallization. Several synthetic and natural fibers (polyethylene terephthalate, carbon, Kevlar, glass, hemp, linen, and cellulose) were employed and compared to custom-spun fiber of stereocomplex (SC) enantiomeric PLA blend. Meaningful differences in the nucleating ability toward PLA could be found for all of the considered fibers. SC PLA fibers display extremely high nucleating efficiency, with the development of a continuous transcrystalline morphology on their surface, up to high crystallization temperatures. Quantitative measurement of the nucleation rate allowed a comparison of the different fiber substrates in the light of classical heterogeneous nucleation theory, by considering the interfacial free-energy difference parameter, Δσ, directly related to the nucleation barrier. The topography of the fibers surface was investigated by atomic force microscopy and ten...