Level Of Interfacial Adhesion Research Articles

Reutilization of polyurethane-based shoe sole scrap as a reinforcing filler in natural rubber for the development of high-performance composites

Reutilization of industrial waste is one of the emerging strategies to combat solid waste disposal for the protection of our environment. The present work describes a novel and economic approach to reutilize finely ground shoe sole scrap, a thermoset polyurethane-based waste (PUW) material generated during shoe sole production in footwear industries as an efficient reinforcing filler in natural rubber (NR). Shoe sole scrap was ground to fine powder and characterized by various analytical techniques. NR-PUW composites were prepared using 0–20 phr (parts per hundred of rubber) of PUW. The cure characteristics, mechanical, thermal, and morphological properties of prepared composites were studied. Composite with 5 phr PUW showed a remarkable improvement in tensile strength by 10% and modulus at 300% elongation increased by 9% compared to that of neat sample. A considerable increase in abrasion resistance and tear strength was also observed in 5 phr PUW loaded composites. Other mechanical properties like hardness, heat build-up and compression set showed a regular increase with further filler loading. To estimate the level of interfacial adhesion between the filler and the matrix, the experimental values of tensile strength were compared with Nicolais–Narkis (N–N), Lu, and Turcsányi–Pukànszky–Tüdõs (T–P–T) models and elastic modulus values with Einstein and Guth and Smallwood models. The tensile strength values are in agreement with T-P-T model (B = 4), up to 5 phr PUW proving the better adhesion between NR and PUW at lower filler loadings. At higher PUW loading, the experimental results are approaching Lu and N–N models indicating that this adhesion is collapsed. The incorporation of PUW as a filler in NR does not adversely impact the thermal stability of prepared composites. The results obtained are not only promising from a circular economy perspective, but also is contributive in production of high-performance, low-cost NR composites for various industrial applications.

The interconnection of efficiency and the degree of aggregation of nanofiller in polymer nanocomposites

The rule of mixtures was the first theoretical model, used for a description of the elastic modulus of multicomponent systems, including those of polymer nanocomposites. However, the use of nominal magnitudes of the characteristics of system components in such an approach led to overestimated values of their elastic modulus. Therefore, various modified versions of the rule of mixtures are currently used for this purpose, which significantly complicate its application and do not indicate the physical factors leading to overestimated theoretical results. In this study, a modified rule of mixtures was proposed, taking into account the decrease in the effective (actual) elastic modulus of the nanofiller in a polymer matrix of the nanocomposite compared to the nominal value determined only by the aggregation of the nanofiller. It is known that the aggregation process is the main negative factor reducing the final properties of nanomaterials, while other factors (for example, the interfacial adhesion level, nanofiller orientation, etc.) depend on the degree of aggregation. The physical sence of the aggregation process is a decrease in the relative proportion of nanofiller-polymer matrix interfacial regions, i.e., the effectiveness of a nanofiller as a reinforcing element of a nanocomposite is determined by its ability to generate high-modulus interfacial regions. The rule of mixtures modified in this way correctly describes the dependence of the elastic modulus of the nanocomposite on the content of the nanofiller, regardless of the type of the latter (carbon nanotubes, graphene, etc.). Therefore, the nanofiller efficiency indicator can serve as a complex parameter that is characteristic of the nanocomposite quality.

Перколяционная модель формирования высокомодульных нанокомпозитов полимер/углеродные нанотрубки

Production of the high-modulus nanocomposites polymer/carbon nanotubes and polymer/graphene at present is actual task and its solution is obviously important for such innovational industry sectors as air-, automobile industry, astronautics a.a. The general theoretical criterions of production of the indicated nanomaterials studied within the frameworks of percolative models of polymer nanocomposites reinforcement. These models assumed, that reinforcement degree or relative modulus of elasticity of polymer nanocomposites is defined by nanofiller structure in polymer matrix of nanocomposites. The structure of nanofiller (more exactly, its aggregates) can be characterized by fractal dimension of these aggregates. A various variants of percolative model of polymer nanocomposites reinforcement allow to taken into account such important for this class of nanomaterials parameters as the level of interfacial adhesion, relative content of interfacial regions (which are in the case of polymer nanocomposites the same reinforcing element of their structure as and actually nanofiller), aggregation degree of nanofiller a.a. Such approach allows to obtain functional interrelation between these characteristics and define conditions, which are necessary of production of high-modulus polymer nanocomposites. It was been found that for this goal achievement is necessary performance of the following conditions: realization of negative values of percolative index. Mathematically this condition is realized in the case, when aggregation degree is smaller, than volume content of nanofiller. Further, the usage of volume content of nanofiller larger than its percolation threshold and achievement of nanoadhesion effect are two following conditions. In the case of the indicated conditions performance percolative model predicts the possibility of production of polymer nanocomposites of the considered classes, which have mechanical characteristics, compared by its value with similar parameters for steel, but essentially smaller by weight.

Dependence of the strengthening degree of nanocomposites “polymethyl methacrylate — functionalized carbon nanotubes” on the structure of the nanofiller

Using the example of nanocomposites formed from polymethyl methacrylate and carbon nanotubes, it is shown that the functionalization of a nanofiller changes the structure of carbon nanotubes and increases the radius of their annular formations. Theoretical and experimental data are presented, confirming that this significantly increases the level of interfacial adhesion in nanocomposites and the efficiency of transfer of applied mechanical stress between the polymer matrix and the nanofiller.

IMPROVING THE STRENGTH CHARACTERISTICS OF PACKERS' SEALING ELEMENTS MADE OF POLYMER NANOCOMPOSITES.

On the basis of a micromechanical model of the tensile strength of a polymer composite, it is shown that, in contrast to the case of adhesion between two polymers, when there is a linear correlation between the thickness of the interfacial region and the level of interfacial adhesion, the strength of the interface in nanocomposites of the "polymer-high modulus filler" type decreases with growth. its thickness. The dependence of the tensile strength of polymer nano-composites on the properties of the material and the level of interfacial interaction has been established. Keywords: strength model, interfacial adhesion, nanocomposite, seal material, packer.

The structure of carbon nanotubes in a polymer matrix

We carried out an analytical structural analysis of interfacial effects and differences in the reinforcing ability of carbon nanotubes for polydicyclopentadiene/carbon nanotube nanocomposites with elastomeric and glassy matrices. In general, it showed that the reinforcing (strengthening) element of the structure of polymer nanocomposites is a combination of the nanofiller and interfacial regions. In the polymer matrix of the nanocomposite, carbon nanotubes form ring-like structures. Their radius depends heavily on the volume content of the nanofiller. Therefore, the structural reinforcing element of polymer/carbon nanotube nanocomposites can be considered as ring-like formations of carbon nanotubes coated with an interfacial layer. Their structure and properties differ from the characteristics of the bulk polymer matrix.According to this definition, the effective radius of the ring-like formations increases by the thickness of the interfacial layer. In turn, the level of interfacial adhesion between the polymer matrix and the nanofiller is uniquely determined by the radius of the specified carbon nanotube formations. For the considered nanocomposites, the elastomeric matrix has a higher degree of reinforcement compared to the glassy matrix, due to the thicker interfacial layer. It was shown that the ring-like nanotube formations could be successfully modelled as a structural analogue of macromolecular coils of branched polymers. This makes it possible to assess the effective (true) level of anisotropy of this nanofiller in the polymer matrixof the nanocomposite. When the nanofiller content is constant, this level, characterised by the aspect ratio of the nanotubes, uniquely determines the degree of reinforcement of the nanocomposites

Influence of wood thermal modification on the supermolecular structure of polypropylene composites

AbstractThe thermal modification of wood can be an interesting way of improving adhesion in polymer composites, although the mechanical properties of composites with heat treated wood presented so far in many works arouse much controversy. In this work, effects of thermal modification of wood on the supermolecular structure and morphology of wood/polypropylene composites (WPC) were investigated using X‐ray diffraction, hot stage optical microscopy, and differential scanning calorimetry. A significant impact of the conditions of thermal wood modification on the formation of polymorphic varieties of the polymer matrix has been demonstrated. Furthermore, thermal treatment also affected the nucleation activity of wood, which was confirmed by determined parameters such as, crystal conversion, half crystallization time, and crystallization temperature. In addition, differences in the formation of transcrystalline structures responsible for the level of interfacial adhesion were depicted based on hot stage optical microscopy. Mechanical tests have shown that obtaining the appropriate strength properties of composite materials depends on the selection of appropriate conditions for thermal modification, which determine the supermolecular structure and nucleation activity. The obtained results, not reported so far, are extremely important when designing WPC composite materials with strictly defined physicochemical parameters.

The mechanism of reinforcement of nanocomposites polyurethane/graphene

The percolation model of reinforcement was used for the theoretical analysis of reinforcement mechanism for nanocomposites polyurethane/graphene. This model allows to elucidate influence of main factors (level of interfacial adhesion, nanofiller content, interfacial regions) on the degree of reinforcement or modulus of elasticity of the considered nanocomposites. It has been shown that for these nanocomposites actually nanofiller (graphene) serves as main reinforcing element. The sharp increasing of modulus of elasticity of nanocomposite occurs at achievement of critical content of nanofiller (∼9 % mas.). The same effect of increasing the level of interfacial adhesion is obtained by a polymer matrix-nanofiller, characterized by a transition from perfect adhesion to nanoadhesion. The structure type of nanofiller in polymer matrix (exfoliated or intercalated one) in one more factor. The proposed model is universal one for all nanocomposites polymer/2D-nanofiller.

Analysis of Physicochemical Interactions of Phases in Particulate-Filled Polymer Nanocomposites

It was shown that the physical and/or chemical interactions of the polymer matrix and the nanofiller surface are determined by two factors: the degree of polymer adsorption by the nanofiller and its surface structure. The introduction of a binding agent enhances these interactions and increases the level of interfacial adhesion. If structural factors and physical and/or chemical interactions are known, it is possible to predict the level of interfacial adhesion.

Effect of moisture content and carbon fiber surface treatments on the interfacial shear strength of a thermoplastic-modified epoxy resin composites

The effect of moisture absorption on the fiber-matrix interfacial shear strength (IFSS) between a polysulfone-modified epoxy matrix and silane surface-treated carbon fiber using a factorial experimental design was studied. Also, two conditions of relative humidity, 25%, and 95%, and likewise six combinations of interfacial adhesion level between the IM7 carbon fiber and the epoxy resin (diglycidyl ether of bisphenol A), modified with polysulfone (PSF) (8.75 wt.%), were studied. The results show that IFSS of the composites increased with both the carbon fiber surface treatments and the epoxy resin modification with PSF. Again, it was found the moisture content had a substantially detrimental effect on the IFSS. However, both the silane treatment and the (PSF) modification of the epoxy resin enhanced the composite's resistance to moisture attack. The ANOVA results showed that the three variables, matrix modification, fiber's surface treatment, and moisture content, were statistically significant. Furthermore, interactions fiber surface treatment–moisture content and fiber surface treatment–epoxy matrix were statistically significant and the interaction between fiber surface treatment and moisture content is as crucial as the polysulfone epoxy modification. It was also found that the silane-treated carbon fibers play a major role in preventing moisture attack to the composite.

Enhancement of the in-plane and pin-load bearing behavior of a quasi-isotropic carbon fiber/epoxy matrix multi-scale laminate by modifying the fiber-matrix interphase using graphene nanoplatelets

The present work examines the effect of incorporating two different concentrations, 0.1% and 0.25%, of silane-functionalized graphene nanoplatelets GnP-GPTMS onto the carbon fiber surface of a quasi-isotropic laminate with the aim to enhance both, the laminate in-plane and the bearing strength, in a pin-loaded joint. Delamination damage modes associated with high-stress gradients were also suppressed in the in-plane loaded laminates, significantly increasing load-carrying capability. The bearing strength of a pin-loaded hole is correlated to the tensile, compression, and shear properties. The results showed an improvement of 13.8% in tensile strength for the 0.1% GnP-GPTMS concentration, as well as 17.3% for compressive strength, while for shear strength, the improvement was 11.89% for the laminate. On the other hand, the behavior of the material in the pin-loaded joint showed an increase of 10.83% for the bearing strength with the 0.1% GnP-GPTMS, fiber surface treatment. Distinct differences were noticed between the tensile stress-loaded area and the area of the residual impression of the pin in the failure mode between the only-resin treated carbon fiber composites and GnPs treated fibers. It was evident, that the interfacial shear strength (IFSS) played an important role on the failure mode. In the compression area in the pin-loaded region, there was a marked presence of a permanent deformation in the matrix. With a closer look at the local failure phenomena at the compression loaded area, there was no fiber kinking and the degree of matrix plasticity disappeared according to the level of interfacial adhesion.

The fractal approach and the effect of nanoadhesive in polymer nanocomposites

Currently, a thermodynamic fractal model of the formation of an interphase layer in polymer nanocomposites is becoming widespread. In accordance with this model, the surface of nanoparticles with which the polymer matrix interacts is a fractal object. This means that the number of contact points depends on the dimension of the nanoparticle surface accessible for such a contact (unshielded). The dependences of the interfacial adhesion parameter on the coefficients of thermal expansion, nanoparticle size, fractal dimension of the nanoparticle surface, etc. have been obtained. In polymer nanocomposites, the level of interfacial adhesion, in comparison with microcomposites, is an order of magnitude higher. This phenomenon is called the nanoadhesion effect and it has an absolutely dimensional character, i.e. takes place when polymers are filled with nanosized particles. Currently, to assess the level of interaction between the phases “nanoparticle-polymer” use the parameter of the level of interfacial adhesion, which is calculated by the values of three quantities: the actual coefficient of linear thermal expansion of the investigated nanocomposite, the coefficients of linear thermal expansion, calculated by the rule of mixtures and by the Turner formula. Considering a nanoparticle as a fractal object, it is possible to estimate the influence of the nanoparticle size, fractal dimension of the nanoparticle surface, and the volumetric content of the filler on the level of interfacial adhesion in the nanocomposite. The article investigates the influence of the size of nanoparticles and the fractal dimension of the surface of aluminum nanoparticles on the parameter of interfacial adhesion. It has been established that filling the polymer matrix with aluminum nanoparticles with the size rn = 35nm, fractal dimension of the nanoparticle ds = 3,3 surface will provide the effect of nanoadhesion in the new nanocomposite based on the elastomer. Experimental studies have confirmed the presence of the nanoadhesion effect in the nanocomposite based on the F-40C elastomer, which manifested itself in an increase in its deformation and strength properties. The optimal composition of the nanocomposite, which provides the highest deformation and strength properties of the material, has been determined.

RETRACTED: Construction of an excellent eco-friendly anti-corrosion system based on epoxy@Sm2O3-polydopamine biopolymer on the mild steel surface

Abstract Metals' surface treatment by chemical conversion coatings (CCs) is one of the most promising methods for improving the organic coatings adhesion strength as well as the corrosion protection properties on the metal substances. Since most of the recently used conventional CCs, i.e., chromate/phosphate-based ones, have undesired environmental problems; nowadays, several non-hazardous chemical treatment solutions based on the rare earth metals (REM), such as Sm-CC, are applied to improve the EC/steel substrate interfacial adhesion level and corrosion resistance of the organic coatings. Despite the eco-friendly nature of the REM-based CCs, they cannot provide high corrosion resistance due to some structural problems. Therefore, finding appropriate and bio-compatible approaches for improving Sm-CC properties is the new topic of research. In the present work, a green/non-toxic surface treatment approach has been used to improve the corrosion resistance of the epoxy coating (EC) on the mild steel (MS) surface. For this objective, a green anti-corrosion composite film based on samarium CC-poly-dopamine (SmPDA) was applied on the MS surface. PDA NPs were obtained by oxidation of dopamine molecules in two different ways, i.e., self-polymerization (PDA1) and oxidant-induced polymerization (PDA2). The deposited SmPDA film morphology and chemical structures were characterized by SEM/EDS and Raman spectroscopy methods. The EC corrosion protection performance evaluation was conducted by electrochemical impedance spectroscopy (EIS) and salt-spray test. Besides, the cathodic delamination (CD) rate and adhesion strength were measured. SEM/EDS analysis and Raman spectroscopy results revealed that nanostructure samarium and graphene-like PDA films were developed on the MS surface via SmPDA chemical modification. Moreover, EIS achievements demonstrated that the Rt values of the EC and scratched EC samples applied on the surface treated MS substrates are 37600 MΩ.cm2 and 90830 Ω.cm2, respectively. These values ​​are about 1375 and 19 fold more than the Rt of those applied on the un-treated MS coupons, respectively. The qualitative salt-spray test results illustrated that via SmPDA treatment, the less disbonding and blistering have occurred on the EC. The EC applied to SmPDA2 treated MS showed better corrosion protection performance than SmPDA1. In addition, by SmPDA2 surface treatment, the CD rate of the EC decreased about 92%, and its adhesion strength increased by about 118%.

RELATIONSHIP BETWEEN THE APPLIED STRESS TRANSFER AND THE NANOFILLER AGGREGATION LEVEL FOR POLYMER/ CARBON NANOTUBES NANOCOMPOSITES

The relationship was studied between the parameter important for the formation of the properties of polymer nanocomposites, namely, the transfer efficiency of the mechanical stress applied to the sample from the polymer matrix to the nanofiller, and the structure of carbon nanotubes formed in this matrix. It has been found that the indicated efficiency, controlled by the level of interfacial adhesion of the nanofiller-polymer matrix, critically depends on the main negative process for all nanocomposites, that is, aggregation of the nanofiller, an increase in the degree which reduces the efficiency of stress transfer. For the nanocomposites under consideration, the process of carbon nanotubes aggregation takes place in the form of emergence of their annular formations that are fractal objects, which has been confirmed experimentally. This fact allows characterization of the carbon nanotubes structure in a polymer matrix using a fractal dimensionality. It has been found that an increase in the fractal dimensionality of the annular formations of carbon nanotubes, reflecting an upgrowth in the degree of their aggregation unambiguously reduces the efficiency of mechanical stress transfer as well as the nanofiller ability to generate interfacial regions.

The Size Effect of Strenthening for Dispersion-Filled Polymer Nanocomposites

In the case of dispersion-filled polymer nanocomposites, it is assumed that a decrease in the size of dispersed nanoparticles leads to a strong increase in their degree of amplification. However, it is known that reducing the size of nanofiller particles intensifies the process of their aggregation, which ultimately dramatically increases the effective size of the nanofiller in the polymer matrix. Therefore, the question arises which nanofiller is more effective from a practical point of view – one having a small size of the initial particles, but highly aggregated, or another having a relatively large size of nanoparticles, but poorly aggregated. The aim of this work is to answer the above question. We have used two dispersion-filled polymer nanocomposites having the same polymer matrix, but filled with a dispersed filler, which size of the original particles differed by about 15 times. It is shown that the level of aggregation of dispersed nanofiller particles in the polymer matrix of the nanocomposite is controlled by two main factors: the size of its initial particles and the conditions for obtaining the nanomaterial, and the influence of the first factor prevails. The process of nanofiller aggregation significantly affects the level of interfacial adhesion and, as a consequence, the final properties of nanocomposites.

Extraordinary toughness enhancement of poly(lactic acid) by incorporating very low loadings of noncovalent functionalized graphene-oxide via masterbatch-based melt blending

In this work, poly(lactic acid) (PLA)/graphene oxide nanocomposites were prepared by pre-incorporating noncovalently functionalized GO (f-GO) with didodecyldimethylammonium bromide (DDAB) into PLA via solvent-mixing and subsequently masterbatch-based melt blending. The introduction of only 0.2 wt% f-GO into PLA achieved an extraordinarily 26.6-fold increase in elongation-at-break relative to PLA without sacrificing strengths. Such an extraordinary improvement in toughness was attributed to the excellent exfoliation of GO sheets and appropriate level of interfacial adhesion between PLA and modified GO nanosheets, thus facilitating the yielding of the matrix.

Mechanical and rheological properties of polystyrene-block-polybutadiene-block-polystyrene copolymer reinforced with carbon nanotubes: effect of processing conditions

Abstract Styrene-b-butadiene-b-styrene (SBS)-based nanocomposites filled with unmodified and –COOH functionalized carbon nanotubes (CNTs) have been formulated at different processing conditions in order to provide an understanding of the influence of the processing temperature and mixing speed on the nanofillers dispersion and on the overall properties of the nanocomposites. The evaluation of the nanocomposites’ mechanical and rheological behavior reveals that the effect of the processing speed on the final properties is almost negligible. Differently, the processing temperature influences strongly the mechanical and rheological properties of SBS-based nanocomposites. Indeed, for the nanocomposites formulated at high temperatures a significant enhancement of the overall properties with respect to the neat matrix has been achieved. Moreover, morphological analyses show that the state of dispersion of both unmodified and functionalized CNTs progressively improves as the processing temperature increases. Particularly, at low processing temperatures a segregated morphology in which the nanofillers are selectively confined in the domains of the SBS matrix has been obtained, while the nanocomposites formulated at 180°C show a homogeneous and uniform CNTs dispersion throughout the matrix and a strong level of interfacial adhesion between the copolymer chains and the dispersed nanofillers.

Simulation of carbon nanotubes as macromolecular coils in nanocomposites with glassy polymer matrix

Ring-shaped carbon nanotubes have been simulated as macromolecular coils in the context of the fractal physical chemistry of polymer solutions k]The dependence of the interfacial adhesion level in polymer/carbon nanotube nanocomposites on the structure of the above composites k]characterized by its fractal dimension k]has been shown k]The validity of this interpretation has been confirmed via a description of the degree of reinforcement of nanocomposites within the reinforcement molecular model.

Mechanical, Thermal, and Morphological Properties of Nanocomposites Based on Polyvinyl Alcohol and Cellulose Nanofiber from Aloe vera Rind

This work was devoted to reinforcement of polyvinyl alcohol (PVA) using cellulose nanofibers from Aloe vera rind. Nanofibers were isolated from Aloe vera rind in the form of an aqueous suspension using chemimechanical technique. Mechanical characterizations showed that incorporation of even small amounts of nanofibers (as low as 2% by weight) had significant effects on both the modulus and strength of PVA. Tensile modulus and strength of PVA increased, 32 and 63%, respectively, after adding 2% of cellulose nanofiber from Aloe vera rind. Samples with higher concentrations of nanofibers also showed improved mechanical properties due to a high level of interfacial adhesion and also dispersion of fibers. The results showed that inclusion of nanofibers decreased deformability of PVA significantly. Dynamic mechanical analysis revealed that, at elevated temperatures, improvement of mechanical properties due to the presence of nanofibers was even more noticeable. Addition of nanofibers resulted in increased thermal stability of PVA in thermogravimetric analysis due to the reduction in mobility of matrix molecules. Morphological observations showed no signs of agglomeration of fibers even in composites with high cellulose nanofiber contents. Inclusion of nanofibers was shown to increase the density of composites.

Organoclay‐reinforced compatible blends of polypropylene with an amorphous polyamide

New nanocomposite materials based on a modified polypropylene (PP) and an amorphous polyamide (aPA)/organoclay nanocomposite were obtained in the melt state. Two aPA contents and organoclay contents in the dispersed phase that varied from 0 to 10 wt% were studied. All the fully exfoliated organoclay remained in the dispersed and minor aPA phase. While adhesive fracture occurred, the interfacial tension was rather low; this is believed to be due to the presence of PP subparticles within the dispersed aPA, creating a large contact surface area. The organoclay in the dispersed phase was seen to be just as capable of increasing the elasticity modulus as when it is dispersed in the matrix. This occurs as long as there is a minimum level of interfacial adhesion, and offers new versatility in the design of nanocomposite materials. POLYM. ENG. SCI., 54:2762–2769, 2014. © 2013 Society of Plastics Engineers