Droplet-matrix Morphology Research Articles

Investigating compatibilization of polyoxymethylene/styrene-butadiene-styrene immiscible blend through addition of hydroxylated graphene.

The main objective of this work was to use hydroxyl-functionalized graphene as a compatibilizer for an immiscible blend. A neat polyoxymethylene/styrene-butadiene-styrene binary blend was prepared at a constant ratio (80/20) and then was compounded with different loading amounts of hydroxyl-functionalized graphene (0.25, 0.5, 0.75, and 1 wt%). The formation of droplet-matrix morphology during blending was observed in microscopy images. A deep understanding of the compatibility was inspected through studying the mechanical, rheological, and microstructural properties. By inspecting the localization of nanoparticles, triple functions of hydroxyl-functionalized graphene as a compatibilizing/reinforcing/lubricating agent were elucidated. The mechanical properties showed that the best compatibility with the ultimate performance was related to the nanocomposite containing 0.25 wt%. Furthermore, the electrical conductivity of the prepared nanocomposites was investigated. Thermodynamic/kinetic studies showed the tendency of hydroxyl-functionalized graphene to disperse droplets, however as the loading value increases, the probability of its presence in the matrix also increases, creating conductive pathways for conductive purposes. The lowest resistance and highest volume of electrical conductivity (8.4 × 10-6 S.cm-1) were shown by 1 wt% FG.

Exploring interfacial tension role in the laminar morphology development in reactive compatibilized PP/EVOH

AbstractLaminar-like structures in PP/EVOH (80/20 wt%) blends were developed by in situ reactive compatibilization using a co-rotating intermeshing twin-screw extrusion without the imposition of post-die-forming elongation flows, i.e., draw ratio (DR) = 0. For that, a maleic anhydride-grafted homopolymer polypropylene (PP-g-MA) was added at 1, 1.5, and 3 wt% using a simple mixing protocol. The correlation between the laminar morphology observed via SEM with interfacial parameters was conducted by nonlinear regression of PP/EVOH viscoelastic response (Gʹ and Gʹʹ) applying the Monomodal Palierne Model to estimate interfacial tension. Uncompatibilized PP/EVOH formed a droplet-matrix morphology with high interfacial tension, indicating incompatibility. As PP-g-MA is added, a laminar-like structure is developed. The remaining droplets become smaller at higher content, with lower interfacial tension between the phases. This scenario hampers the stratification of the dispersed phase. At 3 wt% of PP-g-MA, the morphology returns to being a droplet-matrix, although with high adhesion between the phases. Graphical abstract

Development of microstructure-rheological and electrical properties relationship in PS/POE/HNTs blend nanocomposites using machine learning

Halloysite nanotubes (HNTs) and polypropylene-grafted maleic anhydride (PP-g-MA) were studied for their effects in blends of polystyrene (PS) and polyolefin elastomer (POE). The method used to prepare PS/POE blends (90/10 and 80/20 wt/wt) containing 1, 3, and 5 phr HNTs with or without PP-g-MA (a compatibilizer) was melt blending. Structural and morphological studies using X-ray diffraction analysis (XRD), scanning electron microscopy assisted energy dispersive X-ray spectroscopy (SEM-EDS), and transmission electron microscopy (TEM) confirmed a matrix-droplet morphology and the sample containing compatibilizer has better microstructure than the other formulations. The presence of both PP-g-MA and HNTs together has been discovered to improve the viscoelastic properties of the solid, as evidenced by increased storage modulus and complex viscosity. A notable change occurred in the rheological behavior of the PS/POE blends containing 5 phr of PP-g-MA and HNTs. The dependence of zero-shear viscosity on HNTs loading (0–5 phr) was approximated as a polynomial curve by fitting the experimental data with the Carreau-Yasuda model. Computational fluid dynamics (CFD) simulations were also used to study the effects of HNTs loading on changes in fluid flow patterns and shear rates. The calculated effective viscosities at a given shear rate (0.05 1/s) were in qualitative agreement with the experimental results. Moreover, we utilized various machine-learning techniques to predict the complex viscosity of PS/POE blends and their nanocomposites. The results showed that Extreme Gradient Boosting (XGBoost) outperformed other predictive models based on evaluation metrics. Four-point probe measurements found that the samples containing 5 phr HNT had the lowest conductivities due to the presence of aggregated structures. However, the homogeneous distribution of HNT led to a sudden rise in conductivity in the samples containing 5 phr of PP-g-MA. Computer modeling results of samples with uniform and non-uniform HNT distributions showed that the conductivity decreased with HNT loading and decreased considerably compared to the uniform distribution.

Improving the material extrusion processing of thermoplastic olefin/graphene nanoplatelet composites through control of the morphology.

The aim of this research is to develop thermoplastic olefin (TPO) composites containing polypropylene (PP), an elastomeric ethylene-octene copolymer (EOC) and graphene nanoplatelets (GNPs), suitable for material extrusion (MEX). A PP functionalized with amino-pyridine (PP-g-Py) was used as a compatibilizer. The composite blends had droplet-matrix morphology at compositions as high as 40wt% EOC. Imaging by Transmission Electron Microscopy showed that the GNPs resided at the interface between the blend components. This microstructure promoted higher thermal conductivity of the TPO/GNP composite blends, as compared to the PP/GNP composite (1.54W/m K, vs 1.3W/m K respectively). PP/GNP composites processed by MEX exhibited inadequate interfacial fusion between the deposited strands, which resulted in severe delamination during tensile and flexural testing, and consequently poor mechanical properties. In the TPO/GNP composites containing 40wt% EOC, the slower crystallization of the elongated EOC domains promoted interfacial adhesion between the strands, resulting in better part consolidation, more consistent mechanical properties and improved ductility compared to the PP/GNP composites.

4D printing of porous PLA-TPU structures: effect of applied deformation, loading mode and infill pattern on the shape memory performance

For the first time, the synergy of shape memory polymer (SMP) blending, 4D printing, and cold programming (CP) are investigated for improving the functionality of the shape memory effect (SME), increasing medical applications of porous structures, direct programming, and removing current limitations. Porous PLA-TPU structures with different printing patterns and applied deformation were CPed under constrained and non-constrained compression modes at room temperature and were recovered in the rubbery phase. The shape fixity and shape recovery ratios were calculated and the cross-section morphology was examined with scanning electron microscopy (SEM). The shape fixity values were in the range of 39.75%–71.27%, while almost complete shape recovery ratios (100%) were observed for all porous samples. Low shape fixity ratios can be justified due to the existence of two steps of spring-back and structure relaxation after unloading in cold programming, resulting from elastic and viscoelastic behavior. The glass transition temperature of the PLA-TPU blend was 69 °C and shifted to raw materials, indicating the possibility of some interaction between the two components. SEM images showed the uniform distribution of TPU particles and matrix-droplet morphology in the PLA-TPU blend. After printing, TPU droplets were stretched and the sea-island morphology was observed in some segments.

Shape memory performance assessment of FDM 3D printed PLA-TPU composites by Box-Behnken response surface methodology

In this paper, for the first time, the role of manufacturing parameters of fused deposition modeling (FDM) on the shape memory effect (SME) is investigated by design of experiments. PLA-TPU blend with a weight composition of 30:70% is processed by melt mixing and then extruded into 1.75 mm filaments for 3D printing via FDM. SEM images reveal that TPU droplets are distributed in the PLA matrix, and the immiscible matrix-droplet morphology is evident. Box-Behnken design (BBD), as an experimental design of the response surface method (RSM), is implemented to fit the model between variables and responses. The shell, infill density, and nozzle temperature are selected as variables, and their effects on loading stress, recovery stress, shape fixity, and shape recovery ratio are studied in detail. An analysis of variance (ANOVA) is applied to estimate the importance of each printing parameter on the output response and assess the fitness of the presented model. The ANOVA results reveal the high accuracy of the model and the importance of the parameters. Infill density and nozzle temperature had the greatest and least roles on shape memory properties, respectively. Also, the values of shape fixity and shape recovery were obtained in the ranges of 58–100% and 53–91%, respectively. Despite many researches on 4D printing of PLA, low ductility at room temperature and high stress relaxation rate are its weakness, which are covered by adding TPU in this research. Due to the lack of similar outcomes in the specialized literature, this paper is likely to fill the gap in the state-of-the-art problem and supply pertinent data that are instrumental for FDM 3D printing of functional shape memory polymers with less material consumption.

Fracture mechanism and scratch behaviour of MWNTs reinforced 70/30 (wt/wt) PC/ABS blends and their nanocomposites

In this work, multiwalled carbon nanotubes (MWNTs) are dispersed in 70/30 (wt/wt) polycarbonate (PC)/acrylonitrile butadiene styrene (ABS) (PC70ABS30) blends and their nanocomposites by the melt-processing method. The morphology observations suggest the development of matrix-droplet morphology. There exists an interaction between MWNTs and the PC phase, which is observed from Raman spectroscopic investigation. Dynamic mechanical analysis (DMA) studies show the increase in storage modulus values depicting the stiffening effect of MWNTs, tanδ value increase depicting the energy dissipation. The flexural and impact properties increase significantly. The mechanism of flexural fracture is craze formation in the skin layer with a shear band and facets formation in the bulk region as observed from the SEM investigation of a flexural fractured surface of MWNTs reinforced PC70ABS30 blends and their nanocomposites. In addition, the deformation at the edge, river-like pattern, striation associated shear bands, craze, cavitation, and facets formation are the impact fracture mechanism as observed from SEM investigation of impact fractured surface of MWNTs reinforced PC70ABS30 blends and its nanocomposites. Scratch studies reveal the improved dispersion of MNNTs at 0.5–1 wt% in PC70ABS30 blends and their nanocomposites with a slightly higher scratch coefficient of friction and scratching force.

Surface modified hollow glass microsphere reinforced 70/30 (wt/wt) P.C/A.B.S blends: influence on rheological, mechanical, and thermo-mechanical properties

ABSTRACT In this work, the surface modification of hollow glass microsphere (H.G.M) is done through hydroxylation reaction and silanization reaction for attaching hydroxyl (OH) and amine (NH2) functional groups, respectively. The H.G.M and surface-modified H.G.M are melt-mixed using a twin-screw extruder to process 70/30 (wt/wt) polycarbonate (P.C)/acrylonitrile butadiene styrene (A.B.S) blends and its composites followed by injection moulding. Plasticization of the P.C phase is observed due to H.G.M-OH interaction with P.C phase. While there is the formation of aminolysis compound due to melt-interfacial reaction between H.G.M-NH2 and P.C phase. Scanning electron microscope (S.E.M) observation shows the formation of matrix-droplet morphology for all the compositions of H.G.M and surface-modified H.G.M-filled 70/30 (wt/wt) P.C/A.B.S blend and its composites. However, the incorporation of H.G.M and surface-modified H.G.M in 70/30 (wt/wt) P.C/A.B.S blend improved the processability as observed from rheological characterization. Surface-modified H.G.M influences the glass transition temperature (Tg) of the P.C phase of 70/30 (wt/wt) P.C/A.B.S blend. Among H.G.M-OH and H.G.M-NH2-filled 70/30 (wt/wt) P.C/A.B.S blend; the H.G.M-NH2-filled 70/30 (wt/wt) P.C/A.B.S blend shows the highest improvement in flexural and impact properties. In addition, the fracture mechanism of H.G.M and surface-modified H.G.M-filled 70/30 (wt/wt) P.C/A.B.S blend and its composites under flexural and impact loading are proposed with the help of S.E.M fracture surface images.

The effect of different compatibilisers on the morphology and rheological properties of PP/PET polymer blends

ABSTRACT In the present study, the compatibilisation of polypropylene/polyethylene terephthalate (PP/PET) blends with different types of compatibilisers including maleic anhydride-grafted polypropylene (PP-g-MA), glycidyl methacrylate-grafted polypropylene (PP-g-GMA) and ethylene propylene diene monomer (EPDM) rubber in different concentrations was examined. Samples were evaluated in terms of morphology, thermal and rheological properties. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimeter (DSC) were used. According to the results, all samples had a matrix-droplet morphology. Moreover, with increasing the compatibiliser and its concentration, the droplet sizes in dispersed phase decreased. In other words, compatibilised PP/PET showed a greater dispersed phase size reduction, lower crystallinity percentage and larger storage modulus at low frequencies in comparison with non-compatibilised PP/PET blend. Among different samples, polymer blend compatibilised with PP-g-MA (5 phr) indicated the lowest particle size and significantly improved the compatibilisation of the PP/PET blend.

Migration induced localization of multiwalled carbon nanotubes in PP phase of PP/ABS blend and their hybrid composites: Influence on mechanical and thermal properties

Carbon black (CB) and multiwalled carbon nanotubes (MWNTs) reinforced 80/20 (wt/wt) polypropylene (PP)/acrylonitrile butadiene styrene (ABS) blends and its composites in presence of dual compatibilizer are processed using twin screw extruder followed by injection moulding. The two-step processing is adopted to disperse the MWNTs and CB in 80/20 (wt/wt) PP/ ABS blends in presence of dual compatibilizer. Initially, MWNTs are dispersed with ABS using melt-mixing followed by addition in PP matrix in presence of CB and dual compatibilizer using melt-mixing. A solution experiments is performed to selectively etch the PP and ABS phase respectively show the migration of MWNTs in the PP phase; and CB is localized in the PP phase. Scanning electron microscope (SEM) observation revel the formation of matrix-droplet morphology for MWNTs and CB in 80/20 (wt/wt) PP/ ABS blends and its composites in presence of dual compatibilizer. The average droplet diameter (Dd) measured using SEM images shows decrease in Dd values with the incorporation of MWNTs and CB in 80/20 (wt/wt) PP/ ABS blends and its composites in presence of dual compatibilizer along with calculated interparticle distance (ID) as compared to pure blend. Differential scanning calorimetry (DSC) studies shows the percent crystallinity (Xc) and lamellae thickness of MWNTs and CB filled 80/20 (wt/wt) PP/ ABS blends and its composites in presence of dual compatibilizer increases as compared to pure blend. The tensile properties increases significantly for MWNTs and CB filled 80/20 (wt/wt) PP/ABS blends and its hybrid composites in presence of dual compatibilizer due to the refined morphology and increase in crystallinity. In addition, the thermal stability is enhanced significantly for the selectively localized MWNTs and CB in PP phase of 80/20 (wt/wt) PP/ABS blends and its composites in the presence of dual compatibilizer as compared to pure blend established using thermogravimetric analysis (TGA). The composition of 2.5 wt% of CB filled 80/20 (wt/wt) PP/ABS blends and its composites in presence of dual compatibilizer and MWNTs is the optimized concentration to achieve the highest enhancement in tensile properties, crystallinity, morphology refinement and thermal stability.

Effects of different molecular architectures in terms of comonomer content and composition distribution on the miscibility of cyclic olefin copolymer/polyolefin (COC/POE and COC/LLDPEB) blends

In this work, morphology and rheology of the blends of cyclic olefin copolymer (COC) with two types of crystalline polyolefins were investigated through a wide range of compositions. The used polyolefins had various plasticity, elasticity and viscoelastic behavior. Their molecular structures were similar but their molecular architectures were different in terms of comonomer content and composition distribution (i.e., a linear low-density polyethylene with 4 mol% of 1-butene comonomer (LLDPEB labeled as LLB) and nonuniform composition distribution and a polyolefin elastomer (POE) with 33 mol% of 1-butene comonomer and uniform composition distribution). Morphology of the COC/POE blends was droplet-matrix at low concentrations of the dispersed phase which was changed to co-continuous morphology at intermediate concentrations. Good compatibility and adhesion between phases were also observed. In COC/LLB blends, droplet-matrix morphology and good compatibility were observed between the two phases, except for compositions of 70/30 and 50/50, which exhibited continuous morphology and phase separation. The results of morphology and rheological data such as Cole–Cole plots and variations of viscosity versus composition revealed that these blends were immiscible. The interfacial interaction of the blend phases was investigated using rheological diagrams of variations of their complex viscosities, storage modulus versus frequency, relaxation time spectra and tan δ versus frequency. In addition, the interfacial tension was calculated using emulsion models. It was found that in the intermediate concentrations and COC-rich compounds, the interfacial interaction of the phases and form relaxation time of the dispersed particles of the COC/POE blends were higher than those of the COC/LLB blends, resulting in a further increase in elasticity. In blends with low COC content, the interfacial interaction of the phases and form relaxation time of the dispersed particles of the COC/LLB blends were higher than those of the COC/POE blends.

A new strategy to improve viscoelasticity, crystallization and mechanical properties of polylactide

Biodegradable polylactide/masticated natural rubber (PLA/mNR) blends were prepared by electron induced reactive processing (EIReP) without using any chemical additives. The PLA/mNR blends showed droplet-matrix morphology with decreased mNR particle size after EIReP treatment. The absolute value of complex viscosity and storage modulus increased significantly for the EIReP modified blends, suggesting the improved melt strength and elasticity. The crystallization investigation showed that the cold crystallization peak of PLA phase gradually disappeared after EIReP modification. Instead, the crystallization peak arose during melt cooling process. Consequently, the crystallinity of PLA phase increased from 6.2% to 39.0% as the mNR content increased from 0 to 20 wt%. It was found that the softening temperature of PLA examined by dynamic mechanical analysis increased effectively with the characters of higher modulus compared to the non-modified blends. The EIReP modified blends exhibited excellent mechanical properties with 7-fold increase of impact toughness compared with neat PLA, implying a superior interfacial adhesion and chain interactions between the two polymer phases. Furthermore, the thermogravimetric analysis demonstrated that the thermal stability was slightly enhanced for the EIReP modified blends.

Preparation, Characterization and Processing of PCL/PHO Blends by 3D Bioplotting

Abstract Blends of polycaprolactone (PCL) and poly(3-hydroxyoctanoate) P(3HO) were prepared by melt compounding. These immiscible blends exhibited droplet-matrix morphology at compositions up to 30...

Preparation, Characterization and Processing of PCL/PHO Blends by 3D Bioplotting

Abstract Blends of polycaprolactone (PCL) and poly(3-hydroxyoctanoate) P(3HO) were prepared by melt compounding. These immiscible blends exhibited droplet-matrix morphology at compositions up to 30 wt% P(3HO). Even though the addition of amorphous P(3HO) decreased the crystallinity of PCL, the crystallization temperature of the blends increased by 6 to 7 8C. Blends containing up to 30 wt% P(3HO) had higher crystallization rates, and lower crystallization half-times compared to neat PCL. The viscosity of PCL decreased upon addition of P(3HO), making the blends suitable for processing using a 3D bioplotter. Compositions with 10 to 30 wt% P(3HO) were ideal for processing, because of their improved crystallization kinetics, reduced stickiness and good flow properties. Estimation of the interfacial tension by fitting the Palierne model to the linear viscoelastic properties of the blends revealed good compatibility, which gave rise to synergistic effects in the thermal and mechanical properties. The fibres prepared by 3D bioplotting maintained droplet matrix morphology, with finer particle size than the original compounded material. In addition to favourable viscosity and thermal properties, the extruded fibres containing 30 wt% P(3HO) had comparable modulus to the neat PCL, while exhibiting good ductility. These blends may be suitable alternatives to PCL for biomedical applications, because they provide a range of crystallinities, crystallization rates and viscosities.

Manipulating the morphology of PA6/POE blends using graphene to achieve balanced electrical and mechanical properties

We investigate the effect of graphene localization on the morphology and properties of Polyamide 6 (PA6)/Polyolefin elastomer (POE) blends. Two systems with different compositions were studied: (i) 60/40 (a composition near phase inversion) and (ii) 80/20 (a highly asymmetric composition). In this study, we demonstrate that the migration behavior of graphene is strongly dependent on its dispersion state, which is determined by mixing order. We show that the neat 60/40 (PA6/POE) blend has an unstable co-continuous morphology which breaks up over time during annealing to a droplet-matrix morphology with POE being the continuous phase. The addition of 3 wt% graphene leads to co-continuous morphologies independent of mixing order. In the case of 80/20 systems, preparation of nanocomposites with a POE master batch resulted in elongated POE dispersed domains which becomes a co-continuous morphology at higher level of graphene content (1.5 wt%). However, we observed a decrease in the continuity of the POE phase in the nanocomposite containing 3%wt of graphene due to a reduction of coalescence. Our rheological and electrical measurements revealed that the graphene formed a stronger percolated structure in 80/20 blend containing 3 wt% of graphene in comparison to 60/40/3 nanocomposites, which resulted in lower electrical resistivity. The electrical percolation threshold in this system is 0.66 wt% which demonstrates that using graphene to induce co-continuity in a highly asymmetric composition is a promising approach to design electrically conductive blends with a very low percolation threshold.

Organic modifier induced interfacial transformation, morphology and physico-mechanical properties of PP/NR based blend nanocomposites

The influence of incorporating organic modified nanoclay (Cloisite 10A) (C 10A) on the morphology, interfacial characteristics, and physico-mechanical properties of polypropylene (PP) melt blended with natural rubber (NR) is investigated here. Melt-mixing technique was employed to prepare nanocomposites with varying amounts of C 10A (1, 3, 5, 7 phr). Nanoclay, depending on its concentration, ‘instigated dramatic transformation of phase morphology from a co-continuous type to a non-uniform sea-island type leading to well-defined matrix-droplet morphology. Besides, addition of nanoclay refined the phase morphology and effectuated synergistic improvement in physico-mechanical properties, where 3 wt% nanoclay modified system exhibited optimal properties for end use application in automotive industry thereby establishing the morphology-property correlation.

Influence of dual compatibilizer and carbon black on mechanical and thermal properties of PP/ABS blends and their composites

ABSTRACT In this work, the systematic investigation of the influence of two compatibilizers added individually or together in 80/20 (wt/wt) polypropylene (PP)/acrylonitrile butadiene styrene (ABS) blends in the presence of carbon black (CB) are investigated. The compatibilizers used are PP-grafted maleic anhydride (PP-g-MA) and styrene-ethylene, butylene-styrene–grafted maleic anhydride (SEBS-g-MA). All the composition shows the formation of matrix-droplet morphology. The addition of both PP-g-MA and SEBS-g-MA in 80/20 (wt/wt) PP/ABS blends refines the morphology significantly as compared to 80/20 (wt/wt) PP/ABS blend in presence and absence of PP-g-MA and SEBS-g-MA individually. The average droplet diameter and interparticle distance of all the compositions were measured and correlated with crystallinity and mechanical properties of CB-filled and PP-g-MA/SEBS-g-MA-compatibilized 80/20 (wt/wt) PP/ABS blends. In addition, crystalline behaviour is correlated with the mechanical properties of CB-filled and PP-g-MA/SEBS-g-MA-compatibilized 80/20 (wt/wt) PP/ABS blends. The addition of CB up to 5 wt.% in both PP-g-MA and SEBS-g-MA in 80/20 (wt/wt) PP/ABS blends refines the morphology significantly as compared to 80/20 (wt/wt) PP/ABS blend in presence and absence of PP-g-MA and SEBS-g-MA individually. Solution experiments, interfacial tension and free wetting enthalpy calculations were done to understand the localization of CB in one phase of PP/ABS blends. Further, the addition of CB in 80/20 (wt/wt) PP/ABS blends in the presence of PP-g-MA and SEBS-g-MA added individually or together shows improved thermal stability as compared to neat blends.

Thermoplastic elastomer blend based on EMA and NBR; optimization of process parameters

ABSTRACTEMA–NBR has been explored to be a potential thermoplastic elastomer blend having good thermal stability as well as oil resistance property. The present investigation reports the optimization of process parameters for the novel polymer blends based on poly(ethylene‐co‐methyl acrylate) (EMA) and poly(acrylonitrile‐co‐butadiene) rubber (NBR) with criteria based on the statistical design of experiment (Taguchi L9 orthogonal array). In this case, the polymer blends were prepared by changing the polymer blending conditions such as mixing temperature, mixing time and rotor speed as per Taguchi's L9 orthogonal array. Optimization of the process parameters was carried out based on the physicomechanical properties such as tensile strength, elongation at break, hardness, and tensile impact strength of the resulting EMA/NBR blend. Each processing parameter has been optimized from the experimental data, which are converted into signal‐to‐noise ratio. The standard statistical technique of analysis of variance result was used to evaluate the proportional role of the different control variables. It has been found that the mixing temperature play very significant role trailed by rotor speed and mixing time in controlling droplet matrix morphology of the EMA/NBR blends. Predominantly, these factors affect the size of the NBR domain and its distribution in the EMA matrix, which in turn have a notable contribution to the physicomechanical properties of the blends. By the optimization of processing conditions, the NBR matrix domain size greatly decreases, leading to significant improvement in physicomechanical properties of the EMA/NBR blends. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48900.

Development of in situ nanofibrillar poly (lactic acid)/poly (butylene terephthalate) composites: Non-isothermal crystallization and crystal morphology

Tuned one-step melt spinning of poly (lactic acid) (PLA)/poly (butylene terephthalate) (PBT) blends containing 1–10 wt% of PBT, was carried out successfully to induce in situ nanofibrils of PBT with average diameter of 23–51.4 nm. Scanning electron microscopy (SEM) images showed the morphology of PBT nanofibrils (NFs) in the PLA matrix and it was found that the aspect ratio of PBT NFs was more than 400. The crystal morphology of the PLA melt spun fibers in the presence and absence of PBT NFs was analyzed using polarized optical microscopy. Dramatic changes in the crystal morphology of PLA were observed in the presence of PBT NFs. Scattered spherulites in the PLA fibers changed to very small crystals oriented in the PBT NFs direction in the PLA/PBT fibers. Non-isothermal crystallization studies of PLA in the in situ nanofibrillar composites (NFCs) prepared by compression molding demonstrated a significant improvement of crystallinity (27.5%) as well as crystallization rate. Enhanced crystallization rate provided comparative conditions to study the crystal forms of PLA and their relative populations nucleated during the cold and melt crystallizations. Moreover, the crystallization behavior of PLA/PBT blend with droplet-matrix morphology was compared with that of the NFC sample at the same PBT content to emphasize the tremendous effect of the morphological tailoring of blends.

Polyamide 11/Poly(butylene succinate) Bio-Based Polymer Blends

The manuscript details the preparation and characterization of binary blends of polyamide 11 (PA 11) and poly(butylene succinate) (PBS), with PA 11 as the major component. The blends are fully bio-based, since both components are produced from renewable resources. In addition, PBS is also biodegradable and compostable, contrarily to PA 11. In the analyzed composition range (up to 40 m% PBS), the two polymers are not miscible, and the blends display two separate glass transitions. The PA 11/PBS blends exhibit a droplet-matrix morphology, with uniform dispersion within the matrix, and some interfacial adhesion between the matrix and the dispersed droplets. Infrared spectroscopy indicates the possible interaction between the hydrogens of the amide groups of PA 11 chains and the carbonyl groups of PBS, which provides the compatibilization of the components. The analyzed blends show mechanical properties that are comparable to neat PA 11, with the benefit of reduced material costs attained by addition of biodegradable PBS.