Sodium Ionomer Research Articles

Exploring shape memory and self-healing behavior in sodium and zinc neutralized ethylene/methacrylic acid (EMAA) ionomers

Polymeric materials with self-healing and shape memory capabilities have gained increasing attention for their potential applications across various industries. In this study, zinc and sodium ionomers were systematically investigated using a multi-faceted approach, including rheological analysis, Fourier-transform infrared spectroscopy (FTIR), dynamic mechanical thermal analysis (DMTA), X-ray diffraction (XRD), and self-healing and shape memory assessments. Rheological analysis revealed distinct viscosity profiles among the ionomers, with EMAA-Zn 1706 exhibiting higher viscosity at low frequencies and a pronounced thinning behavior across the frequency range. FTIR analysis provided insights into the ionomers' molecular structures and functional groups. DMTA results illuminated the viscoelastic behavior and phase transitions of the ionomers. Peaks in the tan delta curve indicated order-disorder transitions and crystalline melting temperatures, influencing their mechanical properties. XRD patterns revealed low-angle peaks associated with clusters or localized regions within the ionomers. Additionally, characteristic peaks pointed to degrees of crystallinity and ordered packing. Self-healing assessments demonstrated varying healing efficiencies, with values ranging from 40 % to 60 % for EMAA-Zn 9945 and EMAA-Na 2000, while EMAA-Zn 1706 exhibited lower healing efficiency, not surpassing 20 %, attributed to its distinct rheological characteristics. Shape memory experiments were conducted in both torsion and fold-deploy modes, revealing remarkable shape fixations, with all ionomers exceeding 99 % in torsion and 95 % in the fold-deploy method. In aqueous environments, shape memory returns remained above 90 %, underscoring the water's influence on the shape memory effect. The exceptional shape memory performances and varying self-healing efficiencies of these ionomers highlight their versatility and significance in addressing practical challenges, paving the way for tailored materials with promising applications in numerous fields.

Melting Temperature Depression of Polymer Single Crystals: Application to the Eco-Design of Tie-Layers in Polyolefinic-Based Multilayered Films.

In this paper, we describe a method for determining polymer compatibility, which will aid in establishing the requirements of polyolefinic materials for the eco-design of multilayer films for mechanical recycling while avoiding the use of reactive tie layers. Our ultimate goal is to define the molecular characteristics of the polyolefinic structural layer that improve compatibility with the tie layer during mechanical recycling. We have investigated the melting temperature depression of single crystals of various polyethylenes embedded in commercial polymeric matrices with various functionalities (ester, acrylate, acetate and methacrylic acid sodium ionomer), which can be potentially used as tie layers. We demonstrate how the concentration and molecular architecture of the matrices affect the melting temperature of the embedded single crystals differently depending on the latter’s molecular architecture. The main finding indicates that the tie layers are more compatible with linear polyethylene than with branched polyethylenes. Indeed, our results show that the heterogeneous Ziegler–Natta linear low-density polyethylene is incompatible with all of the tie layers tested. The depression of melting temperatures observed are in excellent agreement with the results obtained by investigating the rheological behaviour and morphological features of solution-mixed blends in which segmental interactions between polymeric chains have been, in theory, maximized. Because Ziegler–Natta linear density polyethylene is one of the most commonly used polymers as a structural layer in multi-layer applications, the findings of this study are useful as they clearly show the unsuitability of this type of polyethylene for recycling from an eco-design standpoint. The specific molecular requirements for polyethylene layers (branching content less than 0.5/100 carbon atoms) can be specified for use in packaging, guiding the eco-design and valorisation of recycled multi-layered films containing this material.

Fluorescent Ionic Probe for Determination of Mechanical Properties of Healed Poly(ethylene-co-methacrylic acid) Ionomer Films.

In recent years, advanced materials with properties resembling biological systems, particularly artificial muscles, have received intense scrutiny. This is because the interesting conformational shape characteristics of such materials have benefited a variety of technologies, including textiles, 3D printing, and medical devices. Although a multitude of shape memory properties have been studied and developed in recent years, self-healing of these polymers after puncture or rupture has also become a major area of study. Most techniques for detection of such processes are mechanically based and require considerable hands-on monitoring. Thus, a rapid visual detection method for self-healing is highly desirable. Herein, we describe fluorescence studies for rapid detection of self-healing properties of a partially neutralized sodium ionomer poly(ethylene-co-methacrylic acid) (PEMA). In this study, two different fluorophores, parent non-ionic 4,6-dipyrenylpyrimidine and ionic 4,6-dipyrenylpyrimidinium iodide fluorophores, were evaluated as possible sensors of self-healing. Incorporation of these probes via solution blending and compatibility into a PEMA of these fluorophores were evaluated. Thermal characterizations using differential scanning calorimetry were also performed to elucidate physical characteristics of healed sites. Ratiometric fluorescence emission variations were explored within puncture-healed ionomer films and related to Young’s modulus properties with good linearity, indicating potential utility of this approach for monitoring elastic modulus properties after healing has occurred. Further statistical analyses of mechanical processes using quadratic discriminant analysis resulted in development of several highly accurate predictive models for determining time since damage healing.

Stable ion bond for high damping, high wet resistance, and low rolling resistance high vinyl polybutadiene rubber‐based dicarboxylate ionomer

AbstractSince the implementation of European Union (EU) tire label, the focus of recent attention has been focused on high performance green tire with low rolling resistance, high wet resistance, low noise, and excellent auto‐braking properties. However, it is a significant challenge to simultaneously achieve these performances for rubber materials. In this research, we developed a novel concept on the construction of stable ion bonds for high performance high vinyl polybutadiene rubber (HVBR)‐based dicarboxylate ionomers. HVBR‐based dicarboxylate sodium ionomer (hereafter referred as Na ionomer) was fabricated through complexation reaction of some or all of carboxylic functional groups on the preprepared maleinized HVBR molecular chains with sodium hydroxide. In the case of Na ionomers, the formation of sodium carboxylate group was certified from Fourier transform infrared spectra. Physical and dynamic mechanical measurements indicated that the tensile strength, wear resistance, wet skid resistance, dry sliding resistance, low rolling resistance, and low heat buildup of the Na ionomer were significantly improved compared to that of HVBR, and Na ionomer simultaneously showed better damping properties and the effective damping temperature range was broadened from −8.8 to 30.1°C, which was closer to the room temperature. Consequently, the approach and results collectively represent a significant advance toward the development of high performance green tire rubber materials.

Influence of two‐phase behavior of ethylene ionomers on diffusion of water

ABSTRACTIn this study, diffusion of water into ethylene ionomers neutralized with sodium or zinc cations (Na‐ionomer and Zn‐ionomer, respectively) was studied by in situ Fourier transform near infrared (NIR) spectroscopy. Water ingress was measured by NIR from the edge of the laminated glass toward the center and the measured water concentration profiles were analyzed by Fick's second law or the modified Jacobs–Jones model, which describes diffusion into a two‐phase system of different density and polarity. It was found that the modified Jacobs–Jones model agrees well with the measured water concentration profiles of ionomers, while the Fickian model fits well to the poly(vinyl‐butyral) (PVB) results. The modified Jacobs–Jones model was also confirmed to apply to water vapor transmission rate (WVTR) data of another sodium ionomer (Na‐ionomer‐HTM) with a higher melting temperature than Na‐ionomer. The water diffusion coefficient for Na‐ionomer, Zn‐ionomer, and PVB are compared, and the diffusion parameters are discussed considering the higher‐ordered structures of ionomers studied by small‐angle X‐ray scattering (SAXS). Simulating conditions that PV modules encounter in field applications, model projections show that Zn‐ionomer and Na‐ionomer‐HTM give significantly lower water permeation than PVB, and due to its low diffusion coefficient, Na‐ionomer will have significantly less water ingress than PVB. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48929.

Flexible and compatible polymer composite blends based on polyurethane/sodium ionomer/lignin and their properties

ABSTRACTPolyurethane, sodium ionomer (Surlyn 8150), and lignin (PSL)‐based composite films were prepared by the solution casting method with different weight percentages of lignin. The relationships among the morphology, thermal resistance, mechanical, and dynamic mechanical properties for all composites were characterized. The structural interactions, microstructure, and optical properties of the composite were studied by Fourier transform infrared, scanning electron microscopy (SEM), X‐ray diffraction, and ultraviolet (UV) spectroscopy. The mechanical and UV absorbance properties of the composite films improved significantly with the addition of lignin particles. The tensile strength increased from 42.5 to 57.2 MPa. Dynamic mechanical analysis results show that the storage modulus of the composites increased and exhibited a single Tg. PSL composite films show excellent water barrier properties, with improved surface hydrophobicity. SEM images revealed that a relatively uniform phase morphology and good interfacial compatibilization wereachieved. These results suggest that all of the composite films with PU, Na ionomers, and lignin materials exhibited good compatibility and miscibility. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48885.

Evaluation and optimization of seal behaviour through solid contamination of heat‐sealed films

A method is presented to apply solid powder/granulate contamination (ground coffee and blood powder) in between the heat conductive seals of flexible packaging materials. A response surface method is tested and validated to optimize seal strength of heat conductive sealing with and without solid contamination. In this study, a maximal seal strength is defined as optimal. Using these methods, three typical packaging films with varying seal layer composition (metallocene linear low‐density polyethylene (LLDPE), plastomer, and sodium ionomer) are maximized towards contaminated seal strength. Contamination caused a decrease in seal strength and narrowed down the process window (seal temperature and time combinations) in which at least 90% of the maximal strength is obtained. The influence of seal layer composition on the clean and solid (ground coffee and blood powder) contaminated seal performance (seal strength, process window, and leak tightness) was evaluated. The film with the plastomer‐based seal layer outperformed the other films with respect to the width of the process window. It also reached a higher seal strength and a higher amount of leak tight seals (evaluated with the dye penetration test) after optimization. The hot tack test was evaluated as predictive test for the contaminated seal strength. The results of this study do not support an indicative relationship.

Investigation of binary blends of m-aramid and sodium ionomer: Mechanical, thermal, and morphological properties

Novel hybrid blend with the composition of m-aramid and sodium ionomers with different weight ratio percentage were prepared by the solution blending technique. The prepared composite films were characterized by the Fourier-transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry, thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). The phase structure, compatibility, and morphologies of the composite film were investigated with SEM, DMA, XRD, and transmission electron microscopy (TEM) analysis. The TGA of the composite films shows improvement in the thermal stability. The temperature corresponding to 5% ( T 5%) weight losses is in the range of 101–414°C. The storage modulus (in the range of 01.55–3.0 GPa) and glass transition temperature (in the range of 244–276°C) decreased with an increase in the content of sodium ionomers. The tensile strength of the composite films is in the range of 160–185 MPa. This effective approach shows a potential application in the field of m-aramid-based composites.

Use of atmospheric plasma treatment to improve adhesion properties of sodium ionomer sheets

Polyolefins are characterized by having a low surface energy due to their non-polar nature, in the case of some ionomers, the base component is a polyolefin, thus relative poor adhesion properties are expected. As is widely known, for many industrial applications, such as coatings, paintings and formation of adhesive bonds, a high surface energy is required in order to provide good surface adhesion; for this reason the use of ionomers in these applications requires a previous surface treatment. In this paper surface treatment by atmospheric plasma has been used to provide surface activation to polyolefin-based sodium ionomers in order to improve their low intrinsic adhesion properties. This work has focused on the analysis of the influence of main process variables such as treatment rate and distance between nozzle and substrate to observe the improvement of adhesion properties at ionomer–polycarbonate adhesion joints subjected to shear and T-peel tests. After plasma treatment, T-peel force has increased six times it original value at most aggressive plasma parameters. Regarding on shear force, at same aggressive conditions of plasma treatment we achieved an increase of ten times its value of the shear sample without surface treatment, and its phenomenon can be seen in SEM pictures.

Modification of surface wettability of sodium ionomer sheets via atmospheric plasma treatment

AbstractIn this study, atmospheric plasma treatment has been used to modify the wetting properties of ethylene‐methacrylic acid sodium ionomer. The effects of the plasma treatment on surface properties of this ionomer have been followed by contact angle measurements, Fourier transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and atomic force microscopy (AFM). With the use of these techniques, the overall effects on activation–functionalization and surface topography changes have been determined in terms of the processing parameters of the atmospheric plasma treatment (rate and distance). The obtained results show a remarkable increase of the wetting properties and optimum balanced behavior is obtained for atmospheric plasma treatment with a rate of 100 mm/s and a distance of 6 mm; in this case, surface free energy is increased from 33 mJ/m2 (untreated ionomer) up to 62 mJ/m2, maintaining good transparency. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers

Polymer Nanocomposites from Organoclays: Structure and Properties

AbstractSummary: Polymer nanocomposites formed from organically modified montmorillonite offer the promise of greatly improved properties over those of the matrix polymer, provided the organoclay can be dispersed, or exfoliated, into the polymer matrix to generate high aspect ratio particles. The exfoliation of organoclays in two series of ethylene‐based polymers, ethylene‐vinyl acetate copolymers and sodium ionomers of ethylene‐methyacrylic acid copolymers, is described along with the properties of these nanocomposites.

Barrier and physical properties of polypropylene/highbarrier ethylene vinyl alcohol copolymer blends compatibilized with a sodium ionomer

AbstractThe aim of this work is to investigate the properties of the PP/EVOH films for their potential use in the packaging industry. Besides, the barrier properties, the mechanical parameters and the morphology of the PP/EVOH films have been studied as function of their composition and the processing technique used for their manufacture. In these applications, the package is frequently in contact with humidity environments and for this, it is necessary to know how environments with different humidity contents, affect the O2 permeability of the polymer material. For these reasons, the influence of the moisture in the values of permeability was evaluated too. The data showed that the oxygen transmission rate (O2TR) decreased with the amount of EVOH, and if the copolymer mass is maintained constant, the O2TR diminished with the quantity of the ionomer in the compositions. Besides, the films obtained by extrusion and following unidirectional stretching, presented better barrier properties to the oxygen molecules than the compression moulded films. When the ionomer is added to the compositions the permeability is reduced even for the films maintained in wet atmosphere. The micrographs obtained by SEM showed that the films have a biphasic structure, where the EVOH particles are dispersed in the PP matrix.

Rheomechanical and morphological study of compatibilized PP/EVOH blends

In order to find the relationships between processibility and properties of the polypropylene/ethylene vinyl alcohol copolymer (PP/EVOH) blends, their rheological behavior, in both shear and extensional flows, was studied and related with mechanical, morphological, and barrier properties of the materials. The nonlinear viscoelastic behavior in shear was also analyzed. The data showed that the rheological parameters (viscosity, loss modulus, storage modulus, extensional viscosity, and Trouton ratio) improved with the addition of low quantities of sodium ionomer copolymer used as compatibilizer. At the same time, the overall properties of the PP/EVOH blends improved as a result of the compatibilizer addition. The morphological analysis showed that the changes in the material properties were related with a more uniform distribution of EVOH particles in the PP matrix. The rheological data obtained allowed us to choose the optimal range for EVOH and ionomer contents, especially in terms of combining good processing characteristics with the good final properties.

Influence of EMAA compatibilizer on the structure and properties of HDPE/hydrotalcite nanocomposites prepared by melt mixing

AbstractHigh‐density polyethylene (HDPE)/hydrotalcite nanocomposites were prepared and characterized with a partially neutralized sodium ionomer of poly(ethylene‐co‐methacrylic acid) (EMAA) as a compatibilizer. Moreover, nanocomposites based on this ionomer were characterized as patterns to analyze the interactions between the hydrotalcite sheets and the methacrylic groups on the ionomer. Hydrotalcite particles were organically modified with sodium dodecyl sulfate ions. Their presence in the interlayer space was confirmed by means of Fourier transform infrared spectroscopy (FTIR) and X‐ray diffraction (XRD). Morphological analysis carried out with XRD and transmission electron microscopy (TEM) revealed the partially exfoliated/intercalated structure achieved in the nanocomposites. The mechanical properties of the HDPE nanocomposites mainly depended on the nature of the polymer matrix. Higher values of the tensile strength and Young's modulus were found in the EMAA nanocomposites. Thermogravimetric analysis (TGA) showed that hydrotalcite particles improved the thermal stability and delayed the onset decomposition temperature of both HDPE and EMAA nanocomposites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Morphology and Properties of Nanocomposites Formed from Poly(ethylene-co-methacrylic acid) Ionomers and Organoclays: Effect of Acid Neutralization

Nanocomposites were prepared by melt blending a series of sodium ionomers formed from poly(ethylene-co-methacrylic acid) and the M2(HT)2 organoclay. The effects of the degree of neutralization of the acid groups on the morphology and properties of the nanocomposites were evaluated using stress−strain analysis, wide-angle X-ray scattering (WAXS), and transmission electron microscopy coupled with particle analysis. The organoclay exfoliation improves progressively as the neutralization level of the sodium ionomers increases. It seems that the ionic units on polymer chains provide a more favorable interaction between the polymer matrix and organoclay than acid units. Predictions of the tensile modulus of the nanocomposites by the Halpin−Tsai equations capture some of the experimental trends, but the absolute values do not agree well with the experimental observations.

A Novel Method for Synthesis of Sulfonated SBS Ionomers by Ring-Opening Reaction of Epoxidized SBS, Their Characterization, Properties, and Blends

A novel method for synthesis of sulfonated ionomer of (styrene-butadiene-styrene) triblock copolymer (SBS) is developed. SBS is first epoxidized by performic acid formed in situ, followed by ring-opening reaction with an aqueous solution of NaHSO3. The optimum conditions for ring-opening reaction of the epoxidized SBS with aqueous solution of NaHSO3 and some properties of the ionomer are studied. It has been found that during the ring-opening reaction phase transfer catalyst, ring-opening catalyst, and a pH regulator are necessary to raise the conversion of epoxy groups to ionic groups. The product is characterized with FTIR spectrophotometry and transmission electron microscopy (TEM) to be the sulfonated ionomer with ionic domains about 5 nm in diameter. With increasing ionic groups, the water absorbency of the ionomer and the dilute solution viscosity of the ionomer increase, whereas the oil absorbency decreases. The ionomer behaves as thermoplastic elastomer in the presence of zinc stearate as ionic plasticizer. The tensile strength and ultimate elongation of the sodium ionomers are higher than those of the original SBS and both increase with zinc stearate below 10 wt% and with ionic group content up to about 1 mmol/g. When the ionomer is blended with crystalline polypropylene, a synergistic effect occurs with respect to the tensile strength. The ionomer can act as a compatibilizer for blending equal weight of SBS and oil-resistant chlorohydrin rubber. In the presence of 3% ionomer, the blend exhibits much better mechanical properties and solvent resistance than the blend without the ionomer. The blend of equal weight of SBS and CHR compatibilized by the ionomer behaves as an oil resistant thermoplastic elastomer. Scanning electron micrographs of the blends with or without the ionomer indicate the increased compatibility between the two components in the presence of the ionomer.

Morphology and properties of nanocomposites formed from ethylene/methacrylic acid copolymers and organoclays

Nanocomposites were prepared by melt mixing ethylene/methacrylic acid copolymers and organoclays, which were compared to equivalent composites prepared from low-density polyethylene (LDPE) and a sodium ionomer of poly(ethylene- co-methacrylic acid). The effects of matrix modification and organoclay structure on the morphology and properties of these nanocomposites were evaluated using stress–strain analysis, wide-angle X-ray scattering (WAXS), and transmission electron microscopy coupled with particle analysis. With all four polymers, the use of a two-tailed organoclay, M 2(HT) 2, led to the formation of more exfoliated nanocomposites than a one-tailed organoclay, M 3(HT) 1. Nanocomposites prepared from ethylene/methacrylic acid copolymers revealed better exfoliation compared to similar composites prepared from LDPE. It seems that the presence of relatively small quantities (1.3–3.1 mol%) of the polar methacrylic acid monomer aids in improving the organoclay exfoliation efficiency of these polymers. Nanocomposites prepared from the sodium ionomer of poly(ethylene- co-methacrylic acid) exhibited the highest levels of organoclay exfoliation compared to all other polymers examined in this study. However, from the observations made in this study, it was not possible to determine conclusively the relative interaction of carboxyl acid groups versus the salt form with the organoclay and, thus, their influence on exfoliation; additional studies will be needed to reach a conclusion on this important point.

Blown films of nanocomposites prepared from low density polyethylene and a sodium ionomer of poly(ethylene-co-methacrylic acid)

A detailed study of the performance of blown films prepared from nanocomposites based on LDPE and a sodium ionomer of poly(ethylene-co-methacrylic acid) is reported. The organoclay content and film blowing conditions were varied to determine the effect of platelet concentration, exfoliation and orientation on film properties. Mechanical properties including stiffness, puncture resistance, and resistance to tear propagation were evaluated and compared to corresponding properties of unfilled polymer films. Permeability of the films to moisture and common atmospheric gases like oxygen, nitrogen, and carbon dioxide was also measured using standard testing methods.In general, films prepared from nanocomposites based on the ionomer exhibited greater improvements in mechanical and barrier properties over unfilled polymer compared to similar films prepared from nanocomposites based on LDPE. This is due to the greater degree of organoclay exfoliation achieved in the ionomer compared to LDPE. The addition of 3wt% MMT to the ionomer increased the tensile modulus of blown films by an average of 50% without sacrificing much tear strength, puncture resistance or film extensibility. Gas permeability in these films was lowered by 40% and moisture transmission rate was reduced by 60%.

Scaling Behavior of the Viscosity of Poly(dimethylsiloxane) Ionomer Solutions

We report solution viscosities of poly(dimethylsiloxane) (PDMS) sodium and zinc ionomers with tailored number of monomers between ions and number of ions per chain in good and in ϑ solvent conditions over a broad range of concentrations. We analyze our data in terms of three concentration regimes of viscosity predicted for associating polymers. The first is a sticky Rouse semidilute unentangled regime with mostly intermolecular associations and renormalized association lifetimes. The second is a sticky reptation semidilute entangled regime also with mostly intermolecular associations and renormalized association lifetimes. The third regime is observed when strands between ions are entangled. For sodium ionomers with few ions per chain the power-law exponents observed experimentally in three predicted concentration regimes match the theoretical predictions. In the case of zinc ionomers with their divalent zinc ions, the power-law exponents do not match the exponents from theory. For ionomers with greater t...

Synthesis of sulfonated rubber ionomers by the ring-opening reaction of epoxidized styrene–butadiene rubber, their characterization, and their properties

A novel method for the synthesis of the sulfonate ionomer of styrene-co-butadiene rubber (SBR) was developed. SBR was first epoxidized by performic acid formed from hydrogen peroxide and formic acid in situ in solution, and this was followed by a ring-opening reaction with an aqueous solution of NaHSO3. The optimum conditions for the epoxidation of SBR in the presence of a phase-transfer catalyst and for the ring-opening reaction of epoxidized SBR with an aqueous solution of NaHSO3 were studied. During the epoxidation of SBR, a phase-transfer catalyst, such as poly(ethylene glycol), could enhance the conversion of double bonds to epoxy groups. During the ring-opening reaction, both the phase-transfer catalyst and ring-opening catalyst were necessary to enhance the conversion of the epoxy groups to ionic groups. The addition of Na2SO3 to the reaction mixture was important to obtain 100% conversion. The products were characterized with Fourier transform infrared spectrophotometry, 1H-NMR spectroscopy, differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). DSC showed that the sodium sulfonate SBR ionomer possessed a dissociation temperature of ionic domains at 110°C, which appeared as black spots under TEM, after the sodium ions of the ionomer were substituted by lead ions. Some properties of the sodium ionomer, such as the water absorbency, oil absorbency, and dilute solution behavior, were studied. With increasing ionic groups, the water absorbency of the ionomer increased, whereas the oil absorbency decreased. The dilute solution viscosity of the ionomer increased abruptly with increasing ionic group content. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3090–3096, 2006