Comparative study of the effect of untreated, silanized and grafted alumina nanoparticles on thermal and dynamic mechanical properties of the styrene-butadiene rubber

in AIP Conference Proceedings (2014, May 15), 1599

Elastomers filled with hard nanoparticles are of great technical importance for the rubber industry. In general, fillers improve mechanical properties of polymer materials, e.g. elastic moduli, tensile ... [more ▼]

Elastomers filled with hard nanoparticles are of great technical importance for the rubber industry. In general, fillers improve mechanical properties of polymer materials, e.g. elastic moduli, tensile strength etc. The smaller the size of the particles the larger is the interface where interactions between polymer molecules and fillers can generate new properties. Using Temperature Modulated Differential Scanning Calorimetry (TMDSC) and Dynamic Mechanical Analysis (DMA), we investigated the properties of the pure styrene-butadiene rubber (SBR), SBR/ alumina nanoparticles, SBR/silanized alumina and SBR/alumina grafted to polymer chains. Beside a general reinforcement effect seen in the complex elastic moduli, the studies revealed that: i) small concentrations of nanoparticles (of 1.5-2 wt%) lead to a minimum in the glass transition temperature as a function of nanoparticle content; ii) for the grafted nanocomposites increasing the nanoparticle concentration beyond 4 wt% yields an increase of Tg by 4 K; iii) DMA mastercurves showed that in case of untreated and silanized alumina mechanical behaviour of the composite systems is rather near to the one of the SBR matrix, but the grafting of elastomer molecules to the silanized fillers induces a quasi-solid like response of the system in the low frequency regime. [less ▲]

Effect of grafted alumina nanoparticles on thermal and dynamic mechanical properties of the styrene-butadiene rubber

Poster (2013, September)

Elastomers filled with hard nanoparticles are of great technical importance for the rubber industry. In general, fillers improve mechanical properties of polymer materials, e.g. elastic moduli, tensile ... [more ▼]

Elastomers filled with hard nanoparticles are of great technical importance for the rubber industry. In general, fillers improve mechanical properties of polymer materials, e.g. elastic moduli, tensile strength etc. The smaller the size of the particles the larger is the interface where interactions between polymer molecules and fillers can generate new properties. The aim of this contribution is to study the influence of the fillers’ surface treatment on the thermal and mechanical behavior of nanocomposites made of styrene-butadiene rubber (SBR). Three types of nanocomposites are investigated : (i) SBR-unmodified alumina, (ii) SBR – silanized alumina and (iii) SBR – alumina grafted to polymer chains. The surface-modified alumina nanoparticles were prepared using the method described in [1]. The grafting of the SBR chains to the alumina nanoparticles was realized by means of the procedures described in [2] and [3]. Temperature Modulated Differential Scanning Calorimetry (TMDSC) and Dynamic Mechanical Analysis (DMA) are well appropriated tools to investigate the thermal and dynamic glass transition behavior of the different nanocomposites, which is expected to be very sensitive to interfacial interactions between the nanoparticles and matrix molecules. TMDSC experiments reveal that all of the nanocomposites undergo a single glass transition. Thus, interphases induced by interfacial interactions do not manifest themselves by an additional glass transition unless it is hidden by the one of the matrix. Moreover, TMDSC measurements reveal that in general the glass transition temperature Tg depends in a complex manner on the concentration and surface treatment of the nanoparticles. The most important change of Tg is observed for the grafted nanocomposites: increasing the nanoparticle weight concentration beyond 4% yields an increase of Tg by 4 K. The corresponding slowing down of the molecular dynamics goes along with a significant decrease of the relaxator strength. More generally the presented results prove that, at the same filler concentration, the number of degrees of freedom freezing at the glass transition in case of un-grafted systems is practically independent on the chemical nature of the particles surface whereas it changes when there exist covalent bonds between the polymer molecules and the nanoparticles. DMA was used to probe the rheological behaviour of the nanocomposites under oscillatory shear. Isothermal frequency sweeps performed at different temperatures yield the real (G’) and imaginary (G”) parts of the complex shear modulus. Linear response regime conditions were strictly respected. The temperature-frequency equivalence principle was exploited to construct mastercurves for G’ and G” at the reference temperature T=273 K. As usual in polymers, three different behaviors were observed: the dynamic glass transition at high frequencies, the entanglement plateau at intermediary frequencies and viscoelastic “flowing” at very low frequencies. It generally appears that the filling of the SBR matrix with nanoparticles leads to an increase of the storage modulus that is more prominent in the rubbery region than in the glassy segment. While, in the low frequency regime, untreated and silanized alumina yield a mechanical behaviour that is rather near to the one of the neat SBR matrix, the grafting of elastomer molecules to the silanized fillers obviously induces a quasi-solid like response of the system. References: 1. Y.-Ch. Yang, S.-B. Jeong, B.-G. Kim, P.-R. Yoon, Powder Technology, 191, 117–121, 2009. 2. E. Passaglia, F. Donati, Polymer, 48, 35-42, 2007. 3. A. Bhattacharya, B. Misra, Prog. Polym. Sci. 29, 767–814, 2004. [less ▲]

Nanoscale confinement of a low molecular weight glass former

Poster (2013, July)

Polymer physics: Heterogeneties and surface dependence molecular organization

Scientific Conference (2013, May)

In this talk, we will present some studies regarding interphases and dependences of the polymer matrix/substrate. Surfaces structuring and modification of substrates plays an important role in the studies ... [more ▼]

In this talk, we will present some studies regarding interphases and dependences of the polymer matrix/substrate. Surfaces structuring and modification of substrates plays an important role in the studies of these dependences. For these goals, different modified surfaces can be used, chemically or physically. One type of surfaces used for these structures as PTFE (poly(tetrafluoroethylene)) nanoribbons on glass/Si substrate – a polymer induced alignment. It was observed that this anti-adhesive substrate can induce a oriented structure in polymer crystal structures like ε- PLC (poly(caprolactone)). Another type of modified surface structure used in our projects is chemically modified microstructures using micro-contact printing technique. Variation of the character of the surface, hydrophilic or hydrophobic, by chemical treatment leads to different molecular interactions and thus different interphases properties. The third polymer/substrate concept for interphases studies is a 3D network confinement: well-defined network as Al templates and inhomogeneous network as porous glasses. A selective penetration of the polymer system into pores or preferential adsorption effect will be discussed. Nanocomposites made of silica nanoparticles- reactive polymers and alumina nanoparticles-SBR (styrene-butadiene rubber) give unique mechanical properties due to the combination of high elasticity with high strength. Investigation of interphases using different types of modified substrate will be point out from two ways: structure resolving, mechanical, dielectrical and calorimetrical properties. Conventional microscopic techniques, such as AFM and SEM, are specific for locally investigated structures on a nanometer scale. Using these complementary microscopic techniques, we are able to distinguish different topographic information of designed substrate. Moreover, in the view of the interphases investigation, HarmoniXTM AFM is used as a mechanical property mapping technique which is able to provide quantitative mechanical characterization of stiffness, elastic modulus, adhesion and energy dissipation of a polymer surface with high lateral resolution (> 20 nm). Mechanical properties are investigated using DMTA ( dynamic mechanical thermal analyzer) and TMA (thermo-mechanical analysis) - for determining the static elastic modules of solid or solid-like sample (polymer matrix), being able to analyze and characterize bulk-like sample at lower or higher frequencies than the dispersion o polymer regime. The temperature range is 80K-500K. Modulated differentia scanning calorimetry (MDSC) is used to examine chemical and physical aspect of the studied system. The simultaneous determination of chemical reaction heat and the specific heat capacity is used to study the curing behavior of nanocomposite network. Dielectric spectroscopy (DS) is a versatile tool to investigate local molecular dynamic for a polymeric/3D confinement network or nanocomposite network. [less ▲]

Nanoscale Characterization of Amine-Epoxy Interphase in 3D Confinement network (porous glass)

Poster (2013)

Many aspects of polymer research and application are directly connected with surface and interface phenomena occurring when polymers are brought into contact with substrates made of another kind of ... [more ▼]

Many aspects of polymer research and application are directly connected with surface and interface phenomena occurring when polymers are brought into contact with substrates made of another kind of material (e.g. metals, nanoparticles, etc.). Generally, interphases emerge between polymer matrix and substrate. These are regions with morphologies and properties differing from those of polymer and substrate. While curing a thermoset, at least two different types of monomers react to form a high molecular weight polymer network. The composition of the mixture of reactance can be altered near substrate in contact with thermoset components. In this poster, we present some preliminary results obtained for interphases which appear while curing an amine-epoxy thermoset in contact with a porous glass (pore size ~20 nm). As tools for investigating the interphases, we exploited Scanning Electron Microscopy (SEM) in addition with Energy-Dispersive X-ray Spectroscopy (EDS) and Tapping-Mode Atomic Force Microscopy (TM - AFM). [less ▲]

Smart polymer surfaces: mapping chemical landscapes on the nanometre scale

in Soft Matter (2010)

We show that Scattering Infrared Near-field Microscopy (SNIM) allows chemical mapping of polymer monolayers that can serve as designed nanostructured surfaces with specific surface chemistry properties on ... [more ▼]

We show that Scattering Infrared Near-field Microscopy (SNIM) allows chemical mapping of polymer monolayers that can serve as designed nanostructured surfaces with specific surface chemistry properties on a nm scale. Using s-SNIM a minimum volume of 100 nm × 100 nm × 15 nm is sufficient for a recording of a “chemical” IR signature which corresponds to an enhancement of at least four orders of magnitudes compared to conventional FT-IR microscopy. We could prove that even in cases where it is essentially difficult to distinguish between distinct polymer compositions based solely on topography, nanophase separated polymers can be clearly distinguished according to their characteristic near-field IR response. [less ▲]

Infrared-Nanoscopy of Surface Patterns in Mixed Polymer Brushes

in Biophysical Journal (2009), 96(3), 639

A near field microscope incorporating vibrational spectroscopy as a contrast mechanism would allow chemical mapping in the so called “fingerprint region”, with the high spatial resolution of SNOM [2-4 ... [more ▼]

A near field microscope incorporating vibrational spectroscopy as a contrast mechanism would allow chemical mapping in the so called “fingerprint region”, with the high spatial resolution of SNOM [2-4]. Using a scattering scanning near-field microscope (s-SNIM) allows us to simultaneously record topography and frequency-dependent near-field signal of organic and biological samples with sub-diffraction limited resolution of up to 90 nm. [less ▲]