Influence of the surface chemistry on the structural and mechanical properties of silica‐polymer composites

Poly(vinyl alcohol) (PVA) composite films filled with nanometric, monodisperse, and spherical silica particles were prepared by the mixing of an aqueous PVA solution and SiO₂ colloidal suspension and the evaporation of the solvent. Adjusting the solution pH to 5 and 9 controlled the PVA‐SiO₂ interaction. Adsorption isotherms showed a higher PVA/surface affinity at a lower pH. This interaction influenced the composite structure and the particle distribution within the polymer matrix, which was investigated by small‐angle neutron scattering, electron microscopy, and swelling measurements. Most of the mechanical properties could be related to the composite structure, that is, the distribution of clusters within the polymer matrix. The progressive creation of a cluster network within the polymeric matrix as the silica volume fraction increased reduced the extensibility or swelling capacity of the composite. The effect was more acute at a higher pH, at which the surface interaction with PVA was weaker and promoted the interconnection between clusters. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3127–3138, 2003     

Compatibilization level effects on the structure and mechanical properties of rubber‐modified polyamide‐6/clay nanocomposites

Exfoliated polyamide‐6 (PA6)/organically modified montmorillonite clay (OMMT) nanocomposites (PNs) were modified with partially maleinized styrene–ethylene/butadiene–styrene triblock copolymers (SEBS) at three maleinization levels in an attempt to link in these materials high toughness with appropriate small‐strain and fracture tensile properties. OMMT stayed only in the PA6 matrix, and no preferential location in the matrix/rubber interphase was observed. The increased dispersed phase size upon the addition of OMMT was attributed to interactions between maleic anhydride (MA) functionalized SEBS and the surfactant of OMMT. The rubber particle size generally decreased when the MA content of SEBS increased, and this indicated compatibilization. The subsequent good adhesion led to tough nanocomposites across a wide range of both strain rates and fracture modes. As the critical interparticle distance (τ_c) decreased with the MA content, and the other parameters that could influence the surface‐to‐surface mean interparticle distance did not change, it is proposed that in these PNs higher adhesion leads to a smaller τ_c value. Finally, the presence in the matrix of a nanostructured clay makes the rubber content necessary for the toughness jump to increase and τ_c to decrease. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3611–3620, 2005     

Preparation of single‐walled carbon nanotubes‐induced poly(p‐oxybenzoyl) crystals

Crystallization of oligomers was applied for the preparation of single‐walled carbon nanotubes (SWNTs)/poly(p‐oxybenzoyl) (POB) crystals using SWNTs as a nucleating agent. Polymerization conditions were investigated to induce the crystallization of POB oligomers through SWNTs. SWNTs/POB plate‐like or lozenge‐shaped crystals were successfully prepared by direct polymerization of p‐hydroxybenzoic acid (HBA) in a mixed solvent of DMF/Py with TsCl in the presence of functionalized SWNTs. The size of the plate‐like crystals were ～200 nm to 3 μm. The crystals consisted of some layers, ～3 nm thick plates. Model reactions showed that esterification reactions proceed between functionalized SWNTs and HBA monomers in the polymerization system. The obtained crystals exhibited unique morphology and high crystallinity, producing a novel SWNT/POB hybrid. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1265–1277, 2008     

Effect of nanotube functionalization on the properties of single‐walled carbon nanotube/polyurethane composites

A commercially available aliphatic thermoplastic polyurethane formulated with a methylene bis(cyclohexyl) diisocyanate hard segment and a poly(tetramethylene oxide) soft segment and chain‐extended with 1,4‐butanediol was dissolved in dimethylformamide and mixed with dispersed single‐walled carbon nanotubes. The properties of composites made with unfunctionalized nanotubes were compared with the properties of composites made with nanotubes functionalized to contain hydroxyl groups. Functionalization almost eliminated the conductivity of the tubes according to the conductivity of the composites above the percolation threshold. In most cases, functionalized and unfunctionalized tubes yielded composites with statistically identical mechanical properties. However, composites made with functionalized tubes did have a slightly higher modulus in the rubbery plateau region at higher nanotube fractions. Small‐angle X‐ray scattering patterns indicated that the dispersion reached a plateau in the unfunctionalized composites that was consistent with the plateau in the rubbery plateau region. The room‐temperature modulus and tensile strength increase was proportionally higher than almost all increases seen previously in thermoplastic polyurethanes; however, the increase was still an order of magnitude below what has been reported for the best nanotube–polymer systems. Nanotube addition increased the hard‐segment glass transition temperature slightly, whereas the soft‐segment glass transition was so diffuse that no conclusions could be drawn. Unfunctionalized tubes suppressed the crystallization of the hard segment; whereas functionalized tubes had no effect. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 490–501, 2007     

POSS‐nylon 6 nanocomposites: Influence of POSS structure on surface and bulk properties

Hybrid organic/inorganic nanocomposites based on polyhedral oligomeric silsesquioxane (POSS) nanostructured chemicals and nylon 6 were prepared via melt mixing. Two structurally and chemically different POSS molecules, a closed cage, nonpolar octaisobutyl POSS (Oib‐POSS) and an open cage, polar trisilanolphenyl POSS (Tsp‐POSS) with differing predicted solubility parameters were evaluated in the nylon matrix. Surface analysis, including quasi‐static and dynamic nanoindentation and nanotribological techniques, revealed exceptional improvements in modulus and hardness along with significant reductions in friction. Additionally, surface wetting characteristics of the nylon were reversed, with POSS incorporation yielding low surface energy, highly hydrophobic surfaces. AFM, TEM/EDAX, spectroscopic techniques and thermomechanical analysis were used to evaluate nanoscale dispersion and bulk properties of the composites. Both POSS molecules exhibit preferential surface segregation behavior in the nylon matrix. Tsp‐POSS, with its higher predicted solubility in nylon, exhibited enhanced dispersion and tribomechanical properties at both nano and bulk scale. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1088–1102, 2009     

High strength toughened epoxy nanocomposite based on poly(ether sulfone)‐grafted multi‐walled carbon nanotube

Hydroxyl terminated poly(ether sulfone) (PES) has been grafted on multi‐walled carbon nanotube (MWCNT). The grafting reaction was confirmed by different characterization techniques such as Fourier transform infrared spectroscopy, Raman spectroscopy, thermogravimetric analysis, and transmission electron microscopy. The extent of the grafting was found to be around 58 wt%. Hybrid nanocomposite of epoxy with the modified MWCNT was also prepared. Effect of grafting on the mechanical, thermal, and viscoelastic properties was studied. Dynamic mechanical studies show an increase in the storage modulus for the nanocomposite prepared using PES‐grafted MWCNT compared with neat epoxy system. PES‐grafted MWCNT–epoxy nanocomposite induces a significant increase in both tensile strength (26%) and fracture toughness (125%) of the epoxy matrix. Field emission scanning electron micrographs of fractured surfaces were examined to understand the toughening mechanism. Copyright © 2015 John Wiley & Sons, Ltd.     

Tailoring the surface chemistry of carbon fiber and E‐glass composites for improved adhesion

The main challenges in the manufacture of composite materials are low surface energy and the presence of silicon‐containing contaminants, both of which greatly reduce surface adhesive strength. In this study, carbon fiber (CF) and E‐glass epoxy resin composites were surface treated with the Accelerated Thermo‐molecular adhesion Process (ATmaP). ATmaP is a multiaction surface treatment process where tailored nitrogen and oxygen functionalities are generated on the surface of the sample through the vaporization and atomization of n‐methylpyrrolidone solution, injected via specially designed flame‐treatment equipment. The treated surfaces of the polymer composites were analyzed using XPS, time of flight secondary ion mass spectrometry (ToF‐SIMS), contact angle (CA) analysis and direct adhesion measurements. ATmaP treatment increased the surface concentration of polar functional groups while reducing surface contamination, resulting in increased adhesion strength. XPS and ToF‐SIMS showed a significant decrease in silicon‐containing species on the surface after ATmaP treatment. E‐glass composite showed higher adhesion strength than CF composite, correlating with higher surface energy, higher concentrations of nitrogen and C?O functional groups (from XPS) and higher concentrations of oxygen and nitrogen‐containing functional groups (particularly C₂H₃O⁺ and C₂H₅NO⁺ molecular ions, from ToF‐SIMS). Copyright © 2010 John Wiley & Sons, Ltd.     

Influences of poly(lactic acid)‐grafted carbon nanotube on thermal,mechanical, and electrical properties of poly(lactic acid)

Poly(lactic acid)‐grafted multiwalled carbon nanotubes (MWNT‐g‐PLA) were prepared by the direct melt‐polycondensation of L ‐lactic acid with carboxylic acid‐functionalized MWNT (MWNT‐COOH) and then mixed with a commercially available neat PLA to prepare PLA/MWNT‐g‐PLA nanocomposites. Morphological, thermal, mechanical, and electrical characteristics of PLA/MWNT‐g‐PLA nanocomposites were investigated as a function of the MWNT content and compared with those of the neat PLA, PLA/MWNT, and PLA/MWNT‐COOH nanocomposites. It was identified from FE‐SEM images that PLA/MWNT‐g‐PLA nanocomposites exhibit good dispersion of MWNT‐g‐PLA in the PLA matrix, while PLA/MWNT and PLA/MWNT‐COOH nanocomposites display MWNT aggregates. As a result, initial moduli and tensile strengths of PLA/MWNT‐g‐PLA composites are much higher than those of neat PLA, PLA/MWNT, and PLA/MWNT‐COOH, which stems from the efficient reinforcing effect of MWNT‐g‐PLA in the PLA matrix. In addition, the crystallization rate of PLA/MWNT‐g‐PLA nanocomposites is faster than those of neat PLA, PLA/MWNT, and PLA/MWNT‐COOH, since MWNT‐g‐PLA dispersed in the PLA matrix serves efficiently as a nucleating agent. It is interesting that, unlike PLA/MWNT nanocomposites, surface resistivities of PLA/MWNT‐g‐PLA nanocomposites did not change noticeably depending on the MWNT content, demonstrating that MWNTs in PLA/MWNT‐g‐PLA are wrapped with the PLA chains of MWNT‐g‐PLA. Copyright © 2008 John Wiley & Sons, Ltd.     

Extruder‐made TPO nanocomposites. I. Effect of maleated polypropylene and organoclay ratio on the morphology and mechanical properties

PP/PP‐g‐MA/MMT/EOR blend nanocomposites were prepared in a twin‐screw extruder at fixed 30 wt % elastomer and 0 to 7 wt % MMT content. Elastomer particle size and shape in the presence of MMT were evaluated at various PP‐g‐MA/organoclay masterbatch ratios of 0, 0.5, 1.0, and 1.5. The organoclay dispersion facilitated by maleated polypropylene serves to reduce the size of the elastomer dispersed phase particles and facilitates toughening of these blend nanocomposites. The rheological data analysis using modified Carreau‐Yasuda model showed maximum yield stress in extruder‐made nanocomposites compared with nanocomposites of reactor‐made TPO. Increasing either MMT content or the PP‐g‐MA/organoclay ratio can drive the elastomer particle size below the critical particle size below which toughness is dramatically increased. The ductile‐brittle transition shift toward lower MMT content as the PP‐g‐MA/organoclay ratio is increased. The D‐B transition temperature also decreased with increased MMT content and masterbatch ratio. Elastomer particle sizes below ～1.0 μm did not lead to further decrease in the D‐B transition temperature. The tensile modulus, yield strength, and elongation at yield improved with increasing MMT content and masterbatch ratio while elongation at break was reduced. The modified Mori‐Tanaka model showed better fit to experimental modulus when the effect of MMT and elastomer are considered individually. Overall, extruder‐made nanocomposites showed balanced properties of PP/PP‐g‐MA/MMT/EOR blend nanocomposites compared with nanocomposites of reactor‐made TPO. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Effects of graphene and carbon nanotube fillers on the shear properties of epoxy

The effects of quantity of graphene and carbon nanotube‐based fillers and their pendant functional groups on the shear properties of a thermoset epoxy were investigated. Two novel functionalized graphenes, one with epoxy functionality and the other with an amine, are synthesized for this purpose. Nanocomposites are prepared at concentrations of 0.5, 1, 2, 3, 5, and 10 wt % and the effects of functionalization on the homogeneity of dispersion and the shear mechanical properties are investigated. The properties of the epoxy nanocomposites containing epoxy‐ and amine‐functionalized graphene are compared with those containing graphene oxide, Claisen‐functionalized graphene, neat multiwalled carbon nanotubes (MWNTs), three types of epoxy‐functionalized MWNT (EpCNT), and the unfilled epoxy. One of the EpCNT ( EpCNT3 ) was found to increase the plateau shear storage modulus by 136% (1.67–3.94 MPa) and the corresponding loss modulus by almost 400% at a concentration of 10 wt %. Several other fillers were also found to increase shear properties at certain concentrations. A hybrid system of EpCNT3 and graphite was also studied, which improved the storage modulus by up to 51%. SEM images reveal a correlation between thorough dispersion of the additive and enhancement of shear modulus. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 997–1006     

Structural and morphological studies on the deformation behavior of polypropylene/multi‐walled carbon nanotubes nanocomposites prepared through ultrasound‐assisted melt extrusion process

Structural and morphological behavior under stress–strain of polypropylene/multi‐walled carbon nanotubes (PP/MWCNTs) nanocomposites prepared through ultrasound‐assisted melt extrusion process was studied by means of optical microscopy, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, small angle X‐ray scattering (SAXS), and wide angle X‐ray scattering (WAXS). A high ductile behavior was observed in the PP/MWCNT nanocomposites with low concentration of MWCNTs. This was related to an energy‐dissipating mechanism, achieved by the formation of an ordered PP‐CNTs interphase zone and crystal oriented structure in the undeformed samples. Different strain‐induced‐phase transformations were observed by ex situ SAXS/WAXS, characterizing the different stages of structure development during the deformation of PP and PP/MWCNTs nanocomposites. The high concentration of CNTs reduced the strain behavior of PP due to the agglomeration of nanoparticles. A structural pathway relating the deformation‐induced phase transitions and the dissipation energy mechanism in the PP/MWCNTs nanocomposites at low concentration of nanoparticles was proposed. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 475–491     

Polypyrrole/multiwalled carbon nanotubes‐based biosensor for cholesterol estimation

The nanocomposite electrode comprising of polypyrrole (PPY) and carboxy functionalized multiwalled carbon nanotubes (MWCNT) has been electrochemically fabricated onto indium–tin–oxide (ITO) electrode using p‐toluene sulfonic acid (PTS). Cholesterol oxidase (ChOx) and cholesterol esterase (ChEt) have been immobilized onto this PPY– MWCNT/ITO nanocomposite electrode using N‐ethyl‐N‐(3‐dimethylaminopropyl) carbodiimide and N‐hydroxy succinimide chemistry for estimation of esterified cholesterol. The ChEt–ChOx/PPY–MWCNT/PTS/ITO bioelectrode has been characterized using Fourier transform infrared spectroscopy, electrochemical techniques, and scanning electron microscope. This ChEt–ChOx/PPY–MWCNT/PTS/ITO nanobioelectrode has a response time of about 9 s, linearity of 4 × 10^?4 to 6.5 × 10^?3 M/l of cholesterol oleate concentration, K_m of 0.02 mM, and thermal stability of upto 45°C. This electrode exhibits improved biosensing characteristics compared with other total cholesterol electrodes reported in literature till date and can be used to estimate cholesterol in blood serum samples. Copyright © 2011 John Wiley & Sons, Ltd.     

Improved mechanical properties of epoxy‐based composites with hyperbranched polymer grafting glass‐fiber

A glass‐fiber, grafted by hyperbranched polymer with hydroxyl group (GF‐HBPH), reinforced epoxy‐based composite was evaluated for mechanical properties and compared with the neat epoxy and silanized glass‐fiber, GF‐APS. The epoxy/GF‐HBPH composites were studied by attenuated total internal reflectance infrared spectroscopy, ¹H nuclear magnetic resonance spectroscopy, thermal gravimetric analysis, mechanical properties analysis, and field emission‐scanning electron microscopy. The results showed that the incorporation of GF‐HBPH could simultaneously enhance the mechanical properties of the epoxy composites. Field emission‐scanning electron microscopy images of the fracture surfaces of the test specimens were used to support the results and conclusions. Copyright © 2016 John Wiley & Sons, Ltd.     

The effect of a semi‐industrial masterbatch process on the carbon nanotube agglomerates and its influence in the properties of thermoplastic carbon nanotube composites

This study details an industrial process to prepare polypropylene (PP) composites reinforced with different loadings (0.5–10wt.%) of carbon nanotubes (CNTs) from a direct dilution of a masterbatch produced by an optimized extrusion compounding process. The work demonstrates how the anisotropy in the distribution of CNTs can have a positive effect on the electrical conductivity and fracture toughness of the resulting composites. The composite with the highest loading of CNTs had an electrical conductivity of 10^?2 S/m comparable with those reported in the available literature. The composites showed anisotropy in their properties that seems to be caused by the non‐homogeneous distribution of the agglomerates produced by the orientation of the flow direction during the injection process. The composites produced in this work exhibited a fracture toughness up to 55% higher than neat PP and failed by polymer ductile tearing. It was found that the CNT agglomerates distributed throughout the matrix increased the toughness of PP by promoting plastic deformation of the matrix during the fracture process and by a slight load transfer between the polymer matrix and the CNTs of the agglomerates. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55 , 189–197     

Role of matrix crystallinity in carbon nanotube dispersion and electrical conductivity of iPP‐based nanocomposites

A homopolymer iPP and a series of propylene‐ethylene random copolymers with a content of ethylene from 7 to 21 mol % were used as matrices to prepare single‐walled carbon nanotube (SWCNT) nanocomposites in a range of SWCNT concentration from 0.15 to 1 wt %. The solution blending and melt‐ compression molding procedures were kept identical for all nanocomposites. The poly(propylenes) have crystallinities ranging from 70 to 10%, and serve to test the role of SWCNTs acting as nucleants to preserve in the nanocomposites the uniform dispersion of SWCNTs after sonication. The major role of polymer crystallinity is to mediate toward a more open and more connected SWCNT network structure. Fast nucleation and growth of high crystalline matrices on multiple sites along the surface of the nanotubes prevents SWCNT clustering, and entraps the SWCNT network between the semicrystalline structure reducing the driving force of nanotubes to curl and twist. Depletion of crystallites in the less crystalline matrices (<35% crystallinity) leads to curled and poorly connected nanotubes. A consequence of the gradual loss of SWCNT connectivity is a decreased electrical conductivity; however, the change with crystallinity is not linear. Conductivity decreases sharply with decreasing crystallinity for SWCNT contents near the percolation region, while for contents approaching the plateau region the electrical conductivity is less sensitive to matrix crystallinity. The percolation threshold decreases rapidly for polymers with <～30% crystallinity and slowly levels off at crystallinities >～40%. At SWCNT concentrations of 0.15 wt %, SEM images of nanocomposites with the highest crystallinity matrix indicate debundled and interconnected nanotubes, whereas more disconnected and curled SWCNTs remain in the lowest crystallinity nanocomposites. Electrical conductivity in the former is relatively high, whereas the latter are insulators. Also discussed is the nucleating effect of nanotubes and restrictions of the filler to polymer chain diffusion in the crystallization of the polymers. SEM images and Raman spectra in the radial breathing modes region (100–400 cm^?1) are complementary tools to extract the quality and details of the SWCNT dispersion in the nanocomposites. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 2084–2096, 2010     

Enhanced electrical and mechanical properties of multiwall carbon nanotube rubber composites

Multiwall carbon nanotube‐filled elastomers are prepared by solution blending using a sonication process. It is shown that the processing conditions have a strong effect on the composite properties especially on electrical properties, which are very sensitive to nanotube dispersion within the elastomeric matrix. The percolation threshold is seen to be shifted to a lower nanotube content than that previously reported. With regard to the unfilled elastomer, large increases in the elastic and tensile moduli are obtained with the nanotube loading, thus highlighting the potential of this type of particles as reinforcing fillers for elastomeric matrices. Raman spectroscopy under strain has been used to evaluate the strength of the polymer–filler interface. Weak interfacial interactions are deduced, but the debundling of the nanotubes and the orientational effects of the polymeric chains are observed when the composite is submitted to a uniaxial deformation. Copyright © 2012 John Wiley & Sons, Ltd.     

Grafting of polyaniline onto the surface of 4‐aminobenzoyl‐functionalized multiwalled carbon nanotube and its electrochemical properties

Polyaniline (PANi)‐grafted multiwalled carbon nanotube (MWNT) composite is prepared by a two‐step reaction sequence. MWNT is first functionalized with 4‐aminobenzoic acid in polyphosphoric acid/phosphorous pentoxide as a “direct” Friedel‐Crafts acylation reaction medium. The resultant 4‐aminobenzoyl‐functionalized MWNT is then treated with aniline using ammonium persulfate/aqueous hydrochloric acid to promote a chemical oxidative polymerization, leading to PANi‐grafted MWNT composite. The resultant composite is characterized by elemental analysis, Fourier‐transform infrared spectroscopy, wide‐angle X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, UV–vis absorption spectroscopy, fluorescence spectroscopy, cyclic voltammetry, and electrical conductivity measurement. The thermooxidative stability and electrical conductivity of PANi‐grafted MWNT composite are improved compared to those of PANi. Specifically, the electrical conductivity of PANi‐grafted MWNT is improved 10–900 times depending upon the level of doping. The capacitance of the composite is also greatly enhanced. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3103–3112, 2010     

Effect of different matrices and nanofillers on the rheological behavior of polymer‐clay nanocomposites

In this work, a comprehensive study of the rheological behavior under shear and isothermal and nonisothermal elongational flow of low density polyethylene (LDPE) and ethylene‐vinyl acetate copolymer (EVA) based nanocomposites was reported to evaluate their “filmability”, that is, the ability of these material to be processed for film forming applications. The influence of two different kinds of organoclay – namely Cloisite 15A and Cloisite 30B – and their concentration was evaluated. The presence of filler clearly affects the rheological behavior in oscillatory state of polyolefin‐based nanocomposites but the increase of complex viscosity and the shear thinning are not dramatic. A larger strain‐hardening effect in isothermal elongational flow is shown by the nanocomposites compared to that of the pure matrix, particularly for EVA based nanocomposites. The melt strength measured under nonisothermal elongational flow increases in the presence of the nanofiller, while the drawability is only slightly lower than that measured for the neat matrix. Moreover, the rheological behavior under nonisothermal elongational flow of EVA‐based nanocomposites is similar for both nanoclays used. Differently, LDPE‐based nanocomposites show a strong dependence on the type of organoclay. Finally, the mechanical properties of the materials were measured by tensile tests. They revealed that the presence of the filler provokes, in all the cases, an increase of the rigidity. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 344–355, 2010     

Effect of solvent–matrix interactions on structures and mechanical properties of micelle‐crosslinked gels

Previous studies on hydrogels crosslinked by acrylated PEO₉₉–PPO₆₅–PEO₉₉ triblock copolymer (F127DA) micelles demonstrate outstanding strength and toughness, which is attributed to the efficient energy dissipation through the hydrophobic association in the micelles. The current study further focuses on how the solvent property affects the structures and the mechanical properties of F127DA micelle crosslinked polyacrylamide gels. Binary solvents comprised of dimethyl sulfoxide (DMSO) and water are used to adjust the polymer/solvent interactions, which consequently tune the conformations of the polymer chains in the network. The presence of DMSO significantly decreases the strength but increased the stretchability of the gels, whereas the overall tensile toughness remained unchanged. In situ small‐angle X‐ray scattering measurements reveal the deformation of micelles along with the stretching direction. A structure evolution mechanism upon solvent change is proposed, according to the experimental observations, to explain influence of solvent quality on the mechanical properties of the micelle‐crosslinked gels. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 473–483     

Effect of the microstructure on the dye diffusion and mechanical properties of polyamide‐6 fibers

The morphology, mechanical properties, and dye diffusion of drawn and heat‐set polyamide‐6 (PA6) yarns were examined. Correlations between the microstructure of PA6 yarns and the dye diffusion coefficients and mechanical properties were established. The crystallinity of PA6 yarns was estimated with density and Fourier transform infrared spectroscopy measurements. A decrease in the γ crystallinity and an increase in the γ‐crystallite size with the draw ratio were observed and attributed to the disappearance of small crystallites and an increase in the average γ‐crystallite size population during the deformation process. The scouring treatment increased the total crystallinity, almost entirely as a result of an increase in the α fraction. Thermally induced crystallization involved increases in both crystalline phases (α and γ) and did not involve crystal‐to‐crystal transformation, whereas drawing PA6 yarns involved both crystallization of the amorphous phase in the α form and γ→α transformation. A sharp decrease in the diffusion coefficient with an increasing draw ratio of PA6 yarns was correlated with an increasing amorphous orientation. The influence of thermally induced crystallinity on the diffusion coefficient seemed exceptionally strong. The mechanical properties of PA6 yarns were examined and correlated with structural changes. It was demonstrated that the crystallinity had a direct correlation with the terminal modulus and extension at break, whereas there was no correlation with the initial modulus. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 349–357, 2007