Influence of rubber content on mechanical,thermal, and morphological behavior of natural rubber toughened poly(lactic acid)–multiwalled carbon nanotube nanocomposites

The effects of natural rubber (NR) on the mechanical, thermal, and morphological properties of multiwalled carbon nanotube (CNT) reinforced poly(lactic acid) (PLA) nanocomposites prepared by melt blending were investigated. A PLA/NR blend and PLA/CNT nanocomposites were also produced for comparison. The tensile strength and Young's modulus of PLA/CNT nanocomposites improved significantly, whereas the impact strength decreased compared to neat PLA. The incorporation of NR into PLA/CNT significantly improved the impact strength and elongation at break of the nanocomposites, which showed approximately 200% and 850% increases at 20 wt % NR, respectively. However, the tensile strength and Young's modulus of PLA/NR/CNT nanocomposites decreased compared to PLA/CNT nanocomposites. The morphology analysis showed the homogeneous dispersion of NR particles in PLA/NR/CNT nanocomposites, while CNTs preferentially reside in the NR phase rather than the PLA matrix. In addition, the incorporation of NR into PLA/CNT lowered the thermal stability and glass‐transition temperature of the nanocomposites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44344.     

Effect of an alkalized‐modified halloysite on PLA crystallization,morphology, mechanical,and thermal properties of PLA/halloysite nanocomposites

Poly(lactic acid) (PLA)/alkalized halloysite nanotube (HNTa) nanocomposites were prepared by melt mixing. The morphology, crystallization behavior, mechanical properties, and thermal stability of the nanocomposites were investigated in comparison with those of the pristine PLA. HNTa can nucleate PLA, leading to a lower recrystallization temperature and higher crystallinity. Infrared spectra revealed that the hydroxyl groups of the PLA interacted with the external hydroxyl groups of HNTa nanofillers via hydrogen bonding. The thermal stability of the nanocomposites was improved with the addition of HNTa. The PLA/HNTa nanocomposites exhibited higher modulus and tensile strength than those of the PLA composites containing unmodified halloysite nanotubes (HNTs). The improvement in properties was probably due to a better dispersion of the HNTa in the PLA matrix compared to that of the unmodified HNTs. Therefore, the facile alkali treatment of HNTs offers a low cost nanofiller for the preparation of PLA based nanocomposites with high tensile modulus and tensile strength. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44272.     

Morphology,thermal, and dynamic mechanical properties of poly(lactic acid)/sisal whisker nanocomposites

Sisal whiskers were used as biobased nanofillers to prepare poly(lactic acid) (PLA)‐based nanocomposites. The whiskers were prepared from sisal fibers via sulfuric acid hydrolysis. Freeze drying of the aqueous whisker suspension was carried out to obtain loosely packed dry sisal whiskers. The nanocomposites were prepared by melt mixing, followed by hot melt pressing. The effect of the freeze drying of the nanofibers, the treatments of the samples with maleic anhydride (MA)/dicumyl peroxide (DCP) and with DCP, and the premixing of the powdered components on the dispersion of the whiskers in the PLA matrix and on the morphology, as well as the thermal and dynamic mechanical properties, of the resultant nanocomposites were investigated. Transmission electron microscopy micrographs show that the acid hydrolysis has led to separation of the whiskers, which had an approximate length and diameter of 195 and 15 nm, respectively. The TEM images of the nanocomposites show similar dispersion of the whiskers in the PLA matrix, whether untreated or MA/DCP or DCP treated. It was found that the crystallization behavior of the PLA matrix changed somewhat depending on whether the samples were treated or not. The thermogravimetric analysis results show a slight decrease in the thermal stabilities of the untreated and the MA/DCP‐treated nanocomposite samples compared to that of the neat PLA, whereas the DCP treatment slightly improved the thermal stability of the nanocomposites. The storage modulus of the nanocomposites increased over the investigated temperature region, and the incorporation of sisal whiskers reduced the intensity of the glass transition at 67°C. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Effects of thermoplastic polyurethane on the properties of poly(lactic acid)/organo‐montmorillonite nanocomposites based on novel vane extruder

Polylactic acid (PLA)/organo‐montmorillonite (OMMT) nanocomposites toughened with thermoplastic polyurethane (TPU) were prepared by melt‐compounding on a novel vane extruder (VE), which generates global dynamic elongational flow. In this work, the mechanical properties of the PLA/TPU/OMMT nanocomposites were evaluated by tensile, flexural, and tensile tests. The wide‐angle X‐ray diffraction and transmission electron microscopy results show that PLA/TPU/OMMT nanocomposites had clear intercalation and/or exfoliation structures. Moreover, the particles morphology of nanocomposites with the addition of TPU was investigated using high‐resolution scanning electronic microscopy. The results indicate that the spherical TPU particles dispersed in the PLA matrix, and the uniformity decreased with increasing TPU content (≤30%). Interestingly, there existed abundant filaments among amount of TPU droplets in composites with 30 and 40 wt% TPU. Furthermore, the thermal properties of the nanocomposites were examined with differential scanning calorimeter and dynamic mechanical analysis. The elongation at break and impact strength of the PLA/OMMT nanocomposites were increased significantly after addition of TPU. Specially, Elongation at break increased by 30 times, and notched impact strength improved 15 times when TPU loading was 40 wt%, compared with the neat PLA. Overall, the modified PLA nanocomposites can have greater application as a biodegradable material with enhanced mechanical properties. POLYM. ENG. SCI., 54:2292–2300, 2014. © 2013 Society of Plastics Engineers     

Polylactide/graphite nanosheets/MWCNTs nanocomposites with enhanced mechanical, thermal and electrical properties

In this study, we have prepared a series of novel biodegradable polymer [polylactide (PLA)]-based nanocomposites using graphite nanosheets (GNs) and multi-walled carbon nanotubes (MWCNTs) by solution-blending technique and investigated their morphologies, structures, thermal stabilities, mechanical and dielectric properties, and electrical and thermal conductivities. Before preparation of the PLA/GNs/MWCNTs nanocomposites, the raw GNs used were endured a rapid expansion by thermal treatment. Temperature of this treatment had some obvious impacts on morphological changes of graphite nanosheets which were verified by means of scanning electron microscope (SEM) and X-ray diffraction (XRD) techniques. Resultant nanocomposites were characterized and evaluated by means of SEM, XRD, thermal conductivity measurements, tensile and impact tests, thermogravimetric analysis and dielectric measurements. Results obtained in this study indicated that thermal-expanded GNs in the presence of MWCNTs facilitate the formation of an appropriate conductive network in PLA matrix which resulted in a relatively low percolation threshold for thermal and electrical conductions of PLA/GNs/MWCNTs nanocomposites. Significant improvements in thermal and electrical conductivities, thermal stability and mechanical properties of PLA/GNs/MWCNTs nanocomposites obtained through the presence of both nanoparticles in PLA matrix were associated with their good co-dispersion and co-reinforcement effects. The macroscopic properties of nanocomposites were found to be strongly dependent on their components, concentrations, dispersion, and the resulted morphological structures.     

Mechanical and thermal properties of thermoplastic polyurethane‐toughened polylactide‐based nanocomposites

The crystallinity and mechanical and thermal properties of polylactide (PLA)‐based biodegradable‐engineered plastic nanocomposites were determined. The nanocomposites were composed of thermoplastic polyurethane (TPU)‐toughened PLA, Talcum (Talc) and organic modified clay (montmorillonite; OMC). The tensile and flexural tests showed that PLA blended with 10 wt% TPU, 4 wt% Talc powder and 2 wt% OMC had the highest modulus and strength without a loss of elongation. The heat distortion temperature (HDT) tests demonstrated that the thermally treated PLA‐based nanocomposites had an HDT of nearly double the HDT for untreated specimens. An analysis of the polymer using scanning electron microscopy demonstrated that the incorporation of inorganic fillers altered the heterogeneous morphology of the PLA/TPU blend. This study investigated the feasibility of using PLA‐based nanocomposites for practical use, including applications in the automotive and furniture industries. POLYM. COMPOS., 35:1744–1757, 2014. © 2013 Society of Plastics Engineers     

In situ Synthesis and mechanical,thermal properties of polyimide nanocomposite film by addition of functionalized graphene oxide

Polyimide (PI) and chemical modified graphene oxide nanocomposite films are prepared by in situ polymerization from solutions of pyromellitic dianhydride and 4,4′‐oxydianiline with various amount (0.5–2 wt%) of 3‐aminopropyltriethoxysilane (APTS) functionalized graphene oxide (GO) sheets in dimethylacetamide. The APTS functionalized GO (GO‐APTS) is a versatile platform for polymer grafting, improving excellent dispersion of GO in the PI matrix, and forming strong interaction with the PI matrix. The GO‐APTS/PI nanocomposites exhibited improvement in mechanical and thermal properties by addition of a small amount of GO‐APTS. With the addition of a small amount of GO‐APTS (1.5 wt%) to PI matrix, mechanical properties with the tensile strength and Young's modulus improved by 45% and 15%, respectively. The thermal analysis showed that the thermal stability of PI was slightly enhanced by the incorporation of GO‐APTS (1.5 wt%). This approach provides a strategy for developing high performance functionalized GO‐polymer composite materials. POLYM. COMPOS., 37:907–914, 2016. © 2014 Society of Plastics Engineers     

Mechanical,thermal, and rheological behavior of ethylene methyl acrylate‐MWNT nanocomposites

Mechanical, thermal, and rheological properties of ethylene methyl acrylate (EMA) composites reinforced with multiwalled carbon nanotubes (MWNTs) have been reported here. Morphological analyses revealed that MWNTs are more uniformly dispersed in EMA upto 3.5 wt% MWNTs loading. Uniform dispersion of MWNTs in EMA matrix leads to decreased crystallinity and increased crystallite size. These are reflected in the mechanical and thermal properties of the composites. The storage moduli of the composites significantly increase by the incorporation of MWNTs, particularly at higher temperatures. The nanocomposites register a slightly higher viscosity than that of neat EMA depending on the contents of MWNTs. Storage modulus (in dynamic shear) increases especially at higher frequency levels due to increased polymer–filler interactions. Dynamic and steady shear rheological properties register a good correlation in regard to the viscous versus elastic response of the nanocomposites. The morphology correlates well with the dynamic rheological characteristics of these nanocomposites. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Effect of surface functionalization on the properties (rheological,mechanical, and dielectric) and microtopography of PEN/CPEN‐f‐CNTs nanocomposites

Novel carboxylic poly(arylene ether nitrile)s (CPEN) functionalized carbon nanotubes (CPEN‐f‐CNTs) were successfully prepared by a simple and effective solvent–thermal route. The CPEN‐f‐CNTs were subsequently used as the novel filler for preparation of high performance poly(arylene ether nitrile)s (PEN) nanocomposites. The SEM characterization of the PEN nanocomposites revealed that the CPEN‐f‐CNTs present better dispersion and interfacial compatibility in the PEN matrix, which was confirmed by the linear rheological analysis (Cole–Cole plots) as well. Consequently, the improved thermal stability (increased initial and maximum decomposition temperature) and enhanced mechanical properties (tensile strength and modulus) were obtained from nanocomposites using CPEN‐f‐CNTs. More importantly, the PEN/CPEN‐f‐CNTs nanocomposites not only show a high dielectric constant but also have low dielectric loss. For example, a dielectric constant of 39.7 and a dielectric loss of 0.076 were observed in the PEN composite with 5 wt% CPEN‐f‐CNTs loading at 100 Hz. Therefore, the flexible PEN/CPEN‐f‐CNTs nanocomposites with outstanding mechanical, thermal and dielectric properties will find wide application in the high energy density capacitors. POLYM. COMPOS., 37:2622–2631, 2016. © 2015 Society of Plastics Engineers     

Thermomechanical and optical properties of biodegradable poly(L‐lactide)/silica nanocomposites by melt compounding

Poly(L ‐lactide) (PLA)/silica (SiO₂) nanocomposites containing 1, 3, 5, 7, and 10 wt % SiO₂ nanoparticles were prepared by melt compounding in a Haake mixer. The phase morphology, thermomechanical properties, and optical transparency were investigated and compared to those of neat PLA. Scanning electron microscopy results show that the SiO₂ nanoparticles were uniformly distributed in the PLA matrix for filler contents below 5 wt %, whereas some aggregates were detected with further increasing filler concentration. Differential scanning calorimetry analysis revealed that the addition of SiO₂ nanoparticles not only remarkably accelerated the crystallization speed but also largely improved the crystallinity of PLA. An initial increase followed by a decrease with higher filler loadings for the storage modulus and glass‐transition temperature were observed according to dynamic mechanical analysis results. Hydrogen bonding interaction involving C?O of PLA with Si? OH of SiO₂ was evidenced by Fourier transform infrared analysis for the first time. From the mechanical tests, we found that the tensile strength and modulus values of the nanocomposites were greatly enhanced by the incorporation of inorganic SiO₂ nanoparticles, and the elongation at break and impact strength were slightly improved. The optical transparency of the nanocomposites was excellent, and it seemed independent of the SiO₂ concentration; this was mainly attributed to the closed refractive indices between the PLA matrix and nanofillers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of peanut shell content on mechanical,thermal, and biodegradable properties of peanut shell/polylactic acid biocomposites

Peanut shell (PNS) was combined with polylactic acid (PLA) to form biocomposites. The biocomposites, with up to 40 wt% PNS, were prepared using a twin–screw extruder. The effect of PNS content on the thermal, mechanical, thermomechanical, morphological, and biodegradable properties was studied. The results showed that the addition of PNS caused a reduction of the melting temperature and the decomposition temperature. Furthermore, the crystallinity of the biocomposites slightly increased with increasing PNS up to 30 wt%. The morphological study showed poor interfacial adhesion between the PNS and PLA matrix. Nevertheless, the mechanical properties revealed that the maximum tensile strength and Young's modulus were at a 30 wt% PNS loading and decreased as more PNS was incorporated into the PLA matrix. The impact strength decreased with an increase in PNS content. The addition of PNS showed significantly improvement of the storage modulus of PLA at high temperature (>80°C). Moreover, the presence of PNS enhanced the biodegradability of the biocomposites. POLYM. COMPOS., 38:682–690, 2017. © 2015 Society of Plastics Engineers     

Novel polylactide/vermiculite nanocomposites by in situ intercalative polymerization. I. Preparation,characterization, and properties

Polylactide (PLA)/vermiculite nanocomposites were prepared by in situ intercalative polymerization of L,L ‐lactide (LLA) in the presence of organomodified vermiculite (VMT). The d‐spacings of both the organomodified VMT and the exfoliated nanocomposites were investigated by X‐ray diffraction (XRD) analysis, and the morphology of exfoliated nanocomposites was examined by transmission electron microscopy (TEM). Thermogravimetric analysis (TGA) indicated that there is some enhancement in degradation behavior between the nanocomposites and the PLA matrix. Dynamic mechanical analysis (DMA) confirmed the constraint effect of exfoliated VMT layers on PLA chains, which is beneficial to the increased storage and loss modulus and increased glass transition temperature. The tensile strength showed that the exfoliated nanocomposites are reinforced and toughened by the addition of nanometer‐size vermiculite layers. POLYM. COMPOS., 28:545–550, 2007. © 2007 Society of Plastics Engineers     

Preparation of polylactide/graphene composites from liquid‐phase exfoliated graphite sheets

Polylactide (PLA)/graphene nanocomposites were prepared by a facile and low‐cost method of solution‐blending of PLA with liquid‐phase exfoliated graphene using chloroform as a mutual solvent. Transmission electron microscopy (TEM) was used to observe the structure and morphology of the exfoliated graphene. The dispersion of graphene in PLA matrix was examined by scanning electron microscope, X‐ray diffraction, and TEM. FTIR spectrum and the relatively low I_D/I_G ratio in Raman spectroscopy indicate that the structure of graphene sheets (GSs) is intact and can act as good reinforcement fillers in PLA matrix. Thermogravimetric analysis and dynamic mechanical analysis reveal that the addition of GSs greatly improves the thermal stability of PLA/GSs nanocomposites. Moreover, tensile strength of PLA/GSs nanocomposites is much higher than that of PLA homopolymer, increasing from 36.64 (pure PLA) up to 51.14 MPa (PLA/GSs‐1.0). POLYM. COMPOS., 35:396–403, 2014. © 2013 Society of Plastics Engineers     

The influence of POSS type on the properties of PLA

In this study, the effects of reactive and non‐reactive poly(hedral oligomeric silsesquoxane) (POSS) type and their loading level on the mechanical, morphological and thermal properties of PLA composites were investigated for the first time in the literature. A decrease in the melt viscosity of PLA was obtained from the vertical force measurements in the presence of POSS particles except for high O‐POSS loading level. This played an important role for power consumption during micro‐compounding process. The mechanical test results showed that, the elastic‐modulus and yield strength of the PLA/POSS composites were lower than pure PLA in most cases. Moreover, a significant improvement in Izod impact strength of PLA composites was achieved by incorporation of POSS particles into PLA regardless of POSS type. Morphological analysis showed that POSS particles dispersed homogeneously in polymer matrix for all compositions. The glass transition temperature of PLA decreased with the addition of POSS particles. POSS particles also enhanced the decomposition temperature of PLA. POLYM. COMPOS., 37:1497–1506, 2016. © 2014 Society of Plastics Engineers     

Poly(lactic acid) and layered silicate nanocomposites prepared by melt mixing: Thermomechanical and morphological properties

Poly(lactic acid) (PLA) nanocomposites were prepared by melt mixing technique in a Haake batch mixer. The clay dispersion within the PLA matrix during melt mixing was well explained through the morphological characterization. Morphological characterizations were studied by X‐ray diffraction and transmission electron microscopy. The exfoliation/intercalation of the clay particles within the polymer matrix during melt mixing depends on the mixing torque generated during the preparation of nanocomposites. The significance of processing temperature and the mixing time in melt mixing were studied for PLA/C93A and PLA/C30B nanocomposites. The structure and properties of the nanocomposites were also characterized by differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis, and mechanical properties by standard tensile testing. The incorporation of nanoclays into the PLA matrix enhanced the mechanical properties and thermal stability of the PLA nanocomposites. This may be due to the reinforcing effect of nanoclays within the polymer matrix. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Effects of thermoplastic poly(ether-ester) elastomer and bentonite nanoclay on properties of poly(lactic acid)

This work presented the influence of thermoplastic poly(ether-ester) elastomer (TPEE) and bentonite (BTN) on improving the mechanical and thermal properties of poly(lactic acid) (PLA). PLA was initially melt mixed with TPEE at six different loadings (5–30 wt%) on a twin screw extruder and then injection molded. The mechanical tests revealed an increasing impact strength and elongation at break with increasing TPEE loading, but a diminishing Young's modulus and tensile strength with respect to pure PLA. The blend at 30 wt% TPEE provided the optimum improvement in toughness, exhibiting an increase in the impact strength and elongation at break by 3.21- and 10.62-fold over those of the pure PLA, respectively. Scanning electron microscopy analysis illustrated a ductile fractured surface of the blends with the small dispersed TPEE domains in PLA matrix, indicating their immiscibility. The 70/30 (wt/wt) PLA/TPEE blend was subsequently filled with three loadings of BTN (1, 3, and 5 parts by weight per hundred of blend resin [phr]), where the impact strength, Young's modulus, tensile strength and thermal stability of all the blends were improved, while the elongation at break was deteriorated. Among the three nanocomposites, that with 1 phr BTN formed exfoliated structure and so exhibited the highest impact strength, elongation at break, and tensile strength compared to the other intercalated nanocomposites. Moreover, the addition of BTN was found to increase the thermal stability of the neat PLA/TPEE blend due to the barrier properties and high thermal stability of BTN.     

Assessment of miscibility,crystallization behaviors,and toughening mechanism of polylactide/acrylate copolymer blends

In this study, acrylate (ACR) copolymer was used to toughen polylactide (PLA). Dynamic mechanical analysis and differential scanning calorimetry results showed that PLA was partially miscible with ACR. Isothermal crystalline behavior indicated that the incorporation of ACR significantly prevented the crystallization of PLA. The transmission electron micrograph showed that ACR was uniformly dispersed in PLA matrix. The mechanical properties of PLA could be improved by the addition of ACR. The analysis of yield stress indicated mild interfacial adhesion between PLA and ACR. Scanning electron micrograph of PLA/ACR blends revealed that the major toughening mechanism was matrix shear yield and plastic flow. Complex viscosity values of PLA/ACR blends were remarkably improved with the incorporation of ACR. Moreover, the van Gurp–Palmen plot, the rheological percolation threshold for the blends was lower than 15 wt%. The incorporation of ACR decreased the absorption coefficient (α), which was caused decreasing transmittance of PLA. POLYM. ENG. SCI., 55:386–396, 2015. © 2014 Society of Plastics Engineers     

Poly(lactic acid) biocomposites reinforced with ultrafine bamboo‐char: Morphology,mechanical, thermal,and water absorption properties

In this study, ultrafine bamboo‐char (BC) was introduced into poly(lactic acid) (PLA) matrix to improve mechanical and thermal properties of PLA based biodegradable composites. PLA/BC biocomposites were fabricated with different BC contents by weight. Uniform dispersion of BC in the PLA matrix and good interaction via physical and chemical interfacial interlocks were achieved. The maximum tensile strength and tensile modulus values of 14.03 MPa and 557.74 MPa were obtained when 30% BC was used. Impact strength of the biocomposite with 30% BC was increased by 160%, compared to that of pure PLA. DSC analysis illustrated that PLA/BC biocomposites had a better thermal property. Crystallization temperature decreased and maximal crystallinity of 30.30% was observed with 30% BC load. We did not notice significant thermal degradation differences between biocomposites with different BC loadings from TGA. Better water resistance was obtained with the addition of BC. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43425.     

Synthesis and characterization of bionanocomposites of poly(lactic acid) and TiO2 nanowires by in situ polymerization

Bionanocomposites from biopolymers and inorganic nanoparticles are of great interest for packaging materials due to their enhanced physical, thermal, mechanical, and processing characteristics. In this study, poly(lactic acid) (PLA) nanocomposites with covalent bonding between TiO₂ nanowire surface and PLA chains were synthesized through in situ melt polycondensation. Molecular weight, structure, morphology, and thermal properties were characterized. Fourier transform infrared spectroscopy confirmed that PLA chains were covalently grafted onto TiO₂ nanowire surface. Transmission electron microscopy images also revealed clearly a third phase presence on the nanowires after the grafting process. Those grafted PLA chains exhibited significantly increased glass transition temperature and thermal stability, compared with pure PLA. The weight-average molecular weight of PLA/2% TiO₂ nanowire bulk nanocomposites increased by 66% compared with that of pure PLA. The electron microscopy results showed that strong interfacial interaction and homogeneous distribution were achieved between inorganic nanowires and organic PLA matrix in the bulk nanocomposites. The PLA matrix in bulk nanocomposites exhibited elevated glass transition temperature and decreased crystallization ability as the TiO₂ nanowire concentrations were increased from 0 to 2%.     

Influence of the processing methods on the properties of poly(lactic acid)/halloysite nanocomposites

The influence of processing methods on the thermo‐mechanical properties of poly (lactic acid) (PLA) nanocomposites were investigated by preparing nanocomposites reinforced by halloysite nanotubes (HNTs) (from 0 to 10 [w/w%]) using solution casting (SC) and melt compounding (MC) methods. Statistical analysis revealed that the processing methods have a significant influence on the tensile properties, where nanocomposites prepared by MC have higher tensile properties compared to those by SC. Experimental results illustrated higher tensile strength and a drop in ductility under the higher strain rate as compared to the low strain rate for PLA/HNTs nanocomposites. At lower concentrations micrographs revealed that, HNTs dispersion was better for SC films as compared to MC, but more prominent HNTs aggregation at higher loadings. MC nanocomposites exhibited a high crystallinity as compared to SC, due to the recrystallization and nucleation effects. The thermal stability and activation energy increased with addition of HNTs, regardless of the processing methods. POLYM. COMPOS., 37:861–869, 2016. © 2014 Society of Plastics Engineers