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     

Flexible and flame resistant poly(lactic acid)/organomontmorillonite nanocomposites

The PLA/OMMT nanocomposites were produced using a melt compounding technique with isopropylated triaryl phosphate ester flame retardant (FR; 10–30 parts per 100 resin). The flammability of the PLA/OMMT composites was evaluated with an Underwriter Laboratory (UL‐94) vertical burning test, and their char morphology was studied using scanning electron microscopy (SEM). The thermal properties of the PLA/OMMT were characterized with a thermogravimetric analyzer (TGA) and a differential scanning calorimeter (DSC). The thermal analyses showed that adding FR reduced the decomposition onset temperature (T_o) of PLA/OMMT. Both PLA/OMMT/FR20 and PLA/OMMT/FR30 showed excellent flame retardant abilities, earning a V‐0 rating during the UL‐94 vertical burning test. A compact, coherent and continuous protective char layer was formed in the PLA/OMMT/FR nanocomposites. Additionally, the DSC results indicated that the flexibility of the PLA/OMMT composites increased after adding FR due to the FR‐induced plasticization. The impact strength of PLA/OMMT was greatly increased by the addition of FR. Flexible PLA nanocomposites with high flame resistance were successfully produced. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41253.     

Preparation of poly(lactic acid)/poly(ethylene glycol)/organoclay nanocomposites by melt compounding

Poly(lactic acid) (PLA)/organoclay nanocomposites were prepared by melt compounding in a co‐rotating twin screw extruder. Two types of commercialized organoclay (dimethyl benzyl stearyl ammonium ion and dimethyl distearyl ammonium ion intercalated between clay platelets named as Clay A and Clay B, respectively) and two grades of poly(ethylene glycol) (PEG) with different molecular weight (M_w = 2,000 and 300,000–500,000 named as PEG2k and PEG500k, respectively) were used in this study. The Young's modulus improved by the addition of organoclay to PLA matrix. The Young's modulus decreased with the addition of PEG to PLA/organoclay nanocomposites. The tensile strength and elongation of PLA/Clay B nanocomposites increased with the addition of PEG2k. The effect of the addition of PEG on d‐spacing of PLA/organoclay nanocomposites is dependent upon the kind of organoclay. The sizes of clay agglomerations in PLA/PEG/organoclay nanocomposites are larger than those of PLA/organoclay ones in the same organoclay. Addition of PEG to PLA/organoclay nanocomposites during melt compounding will not be useful for the preparation of PLA/organoclay having fully exfoliated clay platelets. The shear thinning properties of the nanocomposites are independent of the addition of PEG. On the whole, PEG2k is good plasticizer for PLA/organoclay nanocomposites. POLYM. COMPOS. 27:256–263, 2006. © 2006 Society of Plastics Engineers     

Crystallization behavior and water vapor permeability of poly(lactic acid) nanocomposite under oscillatory shear

The crystallization behavior and water vapor permeability of a poly(lactic acid) (PLA) nanocomposite containing 5 wt % organic montmorillonite (OMMT) under oscillatory shear were investigated. Under the oscillatory shear, OMMT platelets exhibited a better intercalated structure and oriented along the flow direction, some of the OMMT platelets are exfoliated and dispersed in the form of single or few‐layer platelets. These well‐dispersed OMMT platelets acted as more effective nucleating and accelerating agent for the crystallization of PLA, as a result, the cold crystallization enthalpy was significantly decreased, the cold crystallization temperature was much closer to the melting temperature and the crystallinity is dramatically increased, which are observed for the first time. Moreover, the water vapor permeability is decreased by 36% due to the barrier effect of the well‐dispersed OMMT and the increased crystallinity of PLA, which increase the tortuous path that water molecules required to permeate. The mechanical properties are also enhanced owing to the well‐dispersed OMMT and increased crystallinity. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42321.     

Mechanical,thermal, and morphological properties of injection molded poly(lactic acid)/SEBS‐g‐MAH/organo‐montmorillonite nanocomposites

Poly(lactic acid)/organo‐montmorillonite (PLA/OMMT) nanocomposites toughened with maleated styrene‐ethylene/butylene‐styrene (SEBS‐g‐MAH) were prepared by melt‐compounding using co‐rotating twin‐screw extruder followed by injection molding. The dispersibility and intercalation/exfoliation of OMMT in PLA was characterized using X‐ray diffraction and transmission electron microscopy (TEM). The mechanical properties of the PLA nanocomposites was investigated by tensile and Izod impact tests. Thermogravimetric analyzer and differential scanning calorimeter were used to study the thermal behaviors of the nanocomposite. The homogenous dispersion of the OMMT silicate layers and SEBS‐g‐MAH encapsulated OMMT layered silicate can be observed from TEM. Impact strength and elongation at break of the PLA nanocomposites was enhanced significantly by the addition of SEBS‐g‐MAH. Thermal stability of the PLA/OMMT nanocomposites was improved in the presence of SEBS‐g‐MAH. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synergistic effects of cellulose nanocrystals-organic montmorillonite as hybrid nanofillers for enhancing mechanical,crystallization, and heat-resistant properties of three-dimensional printed poly(lactic acid) nanocomposites

Cellulose nanocrystals (CNC)-organic montmorillonite (OMMT) hybrid nanofillers were prepared, and their effects in reinforcing the performance of three-dimensional (3D) printed poly(lactic acid) (PLA) nanocomposites were studied. The results indicated that the hybrid CNC-OMMT nanofillers had a synergistic impact on enhancing the mechanical properties of PLA nanocomposites compared to either single nanofillers (CNC or OMMT). The dispersion of CNC-OMMT in the PLA matrix was not only significantly improved, but also the hybrid nanofillers did not form pore defects in the nanocomposites. In terms of the crystallization performance, the multidimensional hybrid nanofillers acted as efficient heterogeneous-nucleating agents and increased the PLA crystallization rate. Additionally, the incorporation of the hybrid nanofillers improved the heat resistance of the PLA nanocomposites when the printing platform temperature was adjusted to a temperature within the crystallization temperature range of PLA. The preparation of hybrid nanofillers based on existing nanomaterials and their incorporation into polymers creates a novel route for the development of high-performance polymer nanocomposites.     

Studies on morphologies and thermal properties of poly(lactic acid)/polycaprolactone/organic‐modified montmorillonite nanocomposites

Poly(lactic acid)/organic montmorillonite (PLA/OMMT) nanocomposites were prepared via twin‐screw extrusion. Montmorillonite (MMT) was firstly organically modified to improve the compatibility between polyester and MMT. The effects of ratio between PLA and OMMT and the addition of polycaprolactone (PCL), as a compatilizer, on the properties of PLA/OMMT nanocomposites were studied. The morphology and the properties of the nanocomposites were characterized by XRD, DSC, and TEM. Using OMMT, the intercalated structure was formed during the extrusion process and the OMMT interlayers space was enlarged. More OMMT content was apt to form thicker structure with more stacked individual silicate layers, which led to lower degree of crystallinity of PLA. It showed that 1 phr OMMT could result in the largest interlayers space and the best crystallization state. PCL can effectively increase the binding force between two phases and improve the order of the nanocomposites. In addition, the annealing after treatment can form regular structure and enhance the thermal properties of nanocomposites. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Dynamic rheology and morphology of polylactide/organic montmorillonite nanocomposites

The effects of organic montmorillonite (OMMT) on the rheological behaviors and phase morphology of polylactide (PLA) were investigated. The rheological behaviors of nanocomposites showed mainly dependence on both temperature and OMMT content. At low OMMT loading (1 wt %), the complex viscosities showed a Newtonian plateau in low frequency region at low temperatures and converted to a shear‐thinning behaviors with increasing temperature. In comparison, at high OMMT loadings (above 5 wt %), strong shear‐thinning behaviors were observed in the full range of frequencies and temperatures. The results demonstrated rheology of PLA/OMMT is highly sensitive to the nanofillers filled materials. A pseudo‐solid‐like behavior at long scale time in the hybrids with OMMT loading was higher than 5 wt %, this response was related to the formation of a network structure across the polymer matrix due to strong interactions of PLA and OMMT that confined the relaxation process of the macromolecules. X‐ray diffraction and transmission electron microscopy indicated the nanocomposites at low OMMT loading were mainly exfoliated and intercalated nanocomposites were gradually formed with increasing OMMT loading. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Hydrolytic and thermal degradation of polyethylene glycol compatibilized poly(lactic acid)-nanocrystalline cellulose bionanocomposites

This study investigates the effect of nanocrystalline cellulose (NCC) and polyethylene glycol (PEG) on the hydrolytic degradation behavior of poly(lactic acid) (PLA) bio-nanocomposites compared with that of neat PLA, under specific environmental condition, namely at 37°C in a pH 7.4 phosphate buffer medium for a time period up to 60 days. The water absorption, mass loss, molecular weight, and the morphologies of nanocomposites before and after degradation were explored. Thermogravimetric analysis (TGA) was used to study the thermal decomposition of the PLA/NCC/PEG nanocomposites before and after degradation. The results showed that the presence of hydrophilic NCC and PEG significantly accelerated the hydrolytic degradation of PLA, which was related to the rapid dissolution of PEG causing easy access of water molecules to the composites and initiating fast hydrolytic chain scission of PLA. The thermal degradation temperatures of the nanocomposites slightly decreased due to the poor thermal stability of NCC in comparison with that of the neat PLA. After degradation, the thermal stability of the separated PLA from nanocomposites significantly decreased because the molecular decreased during the hydrolytic process. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46933.     

Ethylene‐methyl acrylate‐glycidyl methacrylate toughened poly(lactic acid) nanocomposites

Poly (lactic acid) (PLA) was melt blended in a twin screw extruder using an ethylene‐methyl acrylate‐glycidyl methacrylate rubber as a toughener. PLA/rubber blends were immiscible as observed by scanning electron microscopy. Impact strength and ductility of PLA were improved by the addition of the rubber at the expense of strength and stiffness. An organo‐montmorillonite (OMMT) was used at 2 wt % to counteract the negative effect of the rubber on modulus, and balanced properties were observed at 10 wt % rubber content. X‐ray diffraction and transmission electron microscopy revealed the formation of intercalated/exfoliated structure in the ternary nanocomposites. Thermal behavior analysis indicated that the degree of crystallinity is slightly affected by the clay and the rubber. Both the clay and the rubber decreased the crystallization temperature of PLA and acted as nucleating agents for PLA. The viscosity of the mixtures as measured by melt flow index was highly influenced by the rubber and the OMMT. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Structure and properties of poly(lactic acid)/poly(ε‐caprolactone) nanocomposites with kinetically induced nanoclay location

Poly(lactic acid)/poly(ε‐caprolactone)/organically modified montmorillonite (PLA/PCL/OMMT) nanocomposites were melt‐processed in a twin‐screw extruder under high shear conditions. As a result of the processing conditions employed, the OMMT layers located in the less compatible PCL phase in all the ternary nanocomposites. The morphology of the PLA/PCL blend evolved from “sea‐island” to co‐continuous upon the addition of OMMT. Both the X‐ray diffraction (XRD) and viscoelastic characterization suggested similar OMMT dispersion in the reference PLA binary and in the PLA/PCL ternary nanocomposites, regardless of its location in the PLA and PCL phase, respectively. The reinforcing effect of the organoclay was also similar. The addition of OMMT to the PLA/PCL blend fully compensated the loss in stiffness and oxygen barrier performance produced by PCL in PLA; the nanocomposite with 3% OMMT showed the same modulus and permeability values as those of pure PLA. Moreover, the ductile behavior (elongation at break > 80%) of the PLA/PCL blend remained constant even in the nanocomposite containing 5% OMMT. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43815.     

The effect of organic modifier‐12‐aminolauric acid on morphology and thermal properties of polylactide nanocomposites

A novel organically modified montmorillonite (OMMT) based on a bifunctional organic modifier‐12‐aminolauric acid (ALA) was synthesized. Polylactide (PLA) nanocomposites with this new and traditional OMMT were prepared by solution casting method. The effects of the organic modifiers on structure, morphology and thermal properties of PLA nanocomposites have been investigated using Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The results indicate that ALA has distinct effects on the dispersion of MMT platelets into the PLA matrix, where partial exfoliated as well as intercalated structures have been obtained, when compared with ordinary modifier, cetyltrimethyl ammonium bromide (CTAB). TGA data verifies that PLA nanocomposites with ALA‐MMT organoclay display enhanced thermal stability. The optimal clay loading of ALA‐MMT occurs at 3%wt, leading to the best compromise between clay dispersion and thermal properties. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Impact,thermal, and morphological properties of functionalized rubber toughened‐poly(ethylene terephthalate) nanocomposites

In this study, poly(ethylene terephthalate)/organo‐montmorillonite (PET/OMMT) nanocomposites were melt‐compounded using twin screw extruder followed by injection molding. Maleic anhydride grafted styrene‐ethylene/butylene‐styrene (SEBS‐g‐MAH) was used to improve the impact properties of the PET/OMMT nanocomposites. The notched and un‐notched impact strength of PET/OMMT nanocomposites increased at about 2.5 times and 5.5 times by the addition of 5 wt % of SEBS‐g‐MAH. Atomic force microscopy (AFM) scans were taken from the polished surface of both PET/OMMT and SEBS‐g‐MAH toughened PET/OMMT nanocomposites. The addition of SEBS‐g‐MAH altered the phase structure and clay dispersion in PET matrix. It was found that some of the OMMT silicate layers were encapsulated by SEBS‐g‐MAH. Further, the addition of SEBS‐g‐MAH decreased the degree of crystallinity of the PET/OMMT nanocomposites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Microwave‐assisted preparation of polylactide/organomontmorillonite nanocomposites via in situ polymerization

Microwave technology was introduced to assist the synthesis of polylactide (PLA)/organomontmorillonite (OMMT) nanocomposites in bulk by the in situ ring‐opening polymerization of D,L ‐lactide. Factors that influenced the polymerizing effects, such as the microwave power, irradiation time, and dosages of the catalyst and OMMT, were studied in terms of tensile strength. The polymerization time was decreased dramatically to 10 min under 90 W of microwave irradiation, and the mechanical and thermal properties of the PLA/OMMT nanocomposites were significantly improved. The composite with the highest mechanical properties was obtained when the dosages of the OMMT and the catalyst were 1.0 and 0.6 wt % of the lactide, respectively. The initial decomposition temperature of the PLA/OMMT(1.0 wt % OMMT) nanocomposite was heightened 11.5°C compared with that of pure PLA. The results of scanning electron microscopy confirmed an improvement in the toughness with the addition of OMMT. The transmission electron microscopy and X‐ray diffraction results indicate that an exfoliated and intercalated nanocomposite was successfully prepared. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Improved processability and performance of biomedical devices with poly(lactic acid)/poly(ethylene glycol) blends

To improve the processability of micropolymer‐based devices used for biomedical applications, poly(lactic acid) (PLA) was melt‐blended with poly(ethylene glycol)s (PEGs) of different molecular weights (MWs; weight‐average MWs = 200, 800, 2000, and 4000; these PEGS are referred to as PEG200, PEG800, PEG2000, and PEG4000, respectively, in this article). The thermal properties, mechanical properties, and rheological properties of the PLA and the PLA–PEG blends were investigated. The tensile samples’ morphologies showed that the low‐MW PEGs filled molds well. The rheological properties confirmed that the low‐MW PEGs decreased the complex viscosity, and improved the processability. With decreasing PEG MW, the PLA glass‐transition temperature decreased. The nanoindenter data show that the addition of PEG decreased the modulus and hardness of PLA. The morphologies of the tensile samples showed that with increasing PEG MW, the thicknesses of the core layers increased gradually. The elongation at break was improved by approximately 247% with the addition of PEG200. Such methods can produce easily processed biological materials for producing biomedical products. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45194.     

Synergistic effects of polyethylene glycol and organic montmorillonite on the plasticization and enhancement of poly(lactic acid)

Poly(lactic acid) (PLA)/polyethylene glycol (PEG)/organic montmorillonite (OMMT) composites were prepared by melt blending, and their mechanical, rheological behavior, crystalline behavior, and thermal stability were investigated. Results showed that the elongation-at-break and notch-impact strength of PLA/15PEG/1.5OMMT were 466.45% and 4.34 kJ m⁻², respectively, which were nearly 42 and 2 times higher than those of PLA, respectively. The elongation-at-break of PLA/15PEG/1.5OMMT was also 33 times higher than that of PLA/15PEG and 30 times that of PLA/1.5OMMT. With addition of PEG, PLA chains could insert to OMMT effectively and increase the layer space of OMMT. The characteristics of dynamic behavior and fracture morphology showed that the plasticizer PEG could soften the PLA matrix, leading to easy plastic deformation. OMMT was well distributed in the PLA matrix and able to transfer the stress of external forces, thereby contributing to the matrix yielding initiation and expansion of polymer composites. The synergistic effect of OMMT and PEG was determined by studying the mechanical properties of PLA/PEG/OMMT composite. Differential scanning calorimetry and thermogravimetry studies revealed that OMMT as a nucleating agent improved crystallization and thermal stability. Thus, the synergistic effect of OMMT and PEG balanced the stiffness and toughness of PLA. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47576.     

熔融插层法制备聚乳酸/有机蒙脱土纳米复合材料及其性能研究

以新疆地产蒙脱土和聚乳酸为原料,通过熔融插层的方法制备了聚乳酸(PLA)/有机蒙脱土（OMMT）纳米复合材料。分别采用X射线衍射仪、扫描电子显微镜、透射电子显微镜、热重分析仪等对复合材料的微观结构、形貌及热稳定性进行了表征和分析。研究表明,PLA大分子链已经插入OMMT片层间,层间距明显增大,形成PLA/OMMT纳米复合材料,体系的相容性良好。PLA/OMMT纳米复合材料的热失重曲线移向高温端,其热分解温度提高。PLA/OMMT纳米复合材料的熔点、维卡软化点、冲击强度、拉伸强度、热稳定性均比PLA基体有明显的提高。PLA/OMMT纳米复合材料的降解性初步研究表明其是一种良好的生物可降解环保塑料。     

Morphology,mechanical properties,and thermal stability of rigid PVC/clay nanocomposites

PVC/Poly(ε‐caprolactone) (PCL)/organophilic‐montmorillonite (OMMT) and PVC/Polylactide (PLA)/OMMT nanocomposites were prepared by a two‐step process. PCL/OMMT and PLA/OMMT master batches were prepared by melt blending using a two‐roller mill first, and then they were blended with PVC via extrusion. PVC/OMMT nanocomposites were also prepared using a two‐roller mill. Morphology, mechanical properties, and thermal stability were investigated. The formation of exfoliated or intercalated nanocomposites was confirmed by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Only the PVC/PCL/OMMT nanocomposite showed both higher tensile strength and stiffness than unfilled PVC. Atomic force microscopy (AFM) indicated dependency of this behavior not only on the clay dispersion, but also on the adhesion between the OMMT and the polymer matrix. Furthermore, scanning electron microscopy (SEM) showed that the large plastic deformation of the PVC/PCL matrix also contributed to the strength increase of the PVC nanocomposites. The effect of PCL/OMMT on the improvement of the thermal stability of PVC was remarkable while the effect of PLA/OMMT was moderate. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers.     

Physical,mechanical, and thermal properties of micronized organo‐montmorillonite suspension modified wood flour/poly(lactic acid) composites

In this study, micronized organo‐montmorillonite (OMMT) suspension was prepared with sodium‐montmorillonite (Na‐MMT), didecyl dimethyl ammonium chloride, and dispersant polyethylene glycol 1000 by a ball‐milling process. Then, wood flours (WFs) were impregnated with prepared OMMT suspension at a concentration of 0.5, 1.0, 2.0, or 4.0%. WFs were characterized by X‐ray diffraction and scanning electron microscopy. The hygroscopicity of WF was investigated by a vapor adsorption method. WFs were, respectively, blended with poly (lactic acid) (PLA) to produce WF/PLA composites. Thereafter, physical, mechanical, and thermal properties of the composites were tested. The results showed that a great amount of OMMT attached on the surface of WF, partly penetrating into the microstructure of WF. Owing to the hydrophobicity of OMMT, the vapor adsorption of OMMT‐modified WF decreased. The composite which was produced by WF treated with 0.5% OMMT suspension, showing an increment in the physical, mechanical, and thermal properties. However, OMMT should not be overloaded. Otherwise, the accumulation of OMMT might cause poor interfacial adhesion between WF and PLA matrix. POLYM. COMPOS., 36:731–738, 2015. © 2014 Society of Plastics Engineers     

Properties of linear poly(lactic acid)/polyethylene glycol blends

Poly(lactic acid) (PLA) has great potentials to be processed into films for packaging applications. However, film production is difficult to carry out due to the brittleness and low melt strength of PLA. In this investigation, linear PLA (L‐PLA) was plasticized with poly(ethylene glycol) (PEG) having MW of 1000 g mol^?1 in various PEG concentrations (0, 5, 10, 15, and 20 wt%). In relation to plasticizer content, the impact resistance and crystallinity of L‐PLA was increased, whereas a decrease in glass transition temperature and lower stiffness was observed. Nevertheless, the phase separation has been found in samples which contained PEG greater than 10 wt%. The dynamic and shear rheological studies showed that the plasticized PLA possessed lower viscosity and more pronounced elastic properties than that of pure PLA. Both storage and loss moduli decreased with PEG loading at all frequencies while storage modulus exhibited weak frequency dependence with increasing PEG content. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers