Modification and characterization of montmorillonite fillers used in composites with vulcanized natural rubber

Parent Ca-montmorillonite (Jelšovy Potok, Slovakia, Ca-JP) and Na-montmorillonite Kunipia-F (Japan, Na-KU) were ion-exchanged with octadecyltrimethylammonium (ODTMA) cations. Characteristics of the samples were studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (IR) and thermogravimetry (TG). Surface areas were measured by sorption of N₂ and ethyleneglycol monoethyl ether. Scanning electron microscopy photographs (SEM) were used to characterize the texture of samples. The XRD patterns show that, upon intercalation, the basal spacing of montmorillonite is expanded and corresponds to the pseudotrimolecular arrangement of organic cations in the interlayers. The IR spectra of organically modified montmorillonite show C-H stretching and bending bands of both CH₃ and CH₂ groups in the 3000–2800 cm⁻¹ and 1500–1400 cm⁻¹ region, respectively. Modification of montmorillonite by organic cations decreased the hydrophilicity of their mineral surface and adsorbed water evaporated at lower temperatures. The SEM photographs reveal a tendency towards lump formation and agglomeration of the ODTMA-montmorillonite particles. The modification introducing organic moiety lead to a substantial decrease in the surface area of both montmorillonites; however, it remained remarkably high, being at the level typical for silica. Completely characterized fillers were used to prepare rubber compositions with enhanced physical properties, as described in Hrachová et al. (2008).     

Thermal degradation kinetics of polystyrene/cadmium sulfide composites

The thermal degradation kinetics of polystyrene/CdS composites were studied by thermogravimetry. The samples were heated in nitrogen, with three different heating rates: 5, 20 and 40 °C min⁻¹. We calculated kinetic parameters using KAS isoconversion method. The results showed that the maximum activation energy of thermal degradation is achieved for PS/CdS composite with about 10% of the CdS filler. Higher concentration of CdS in the composite (20%) induced acceleration of the thermal degradation, approaching the rate of degradation of the pure polystyrene matrix.     

Thermal properties of compatibilized and filled natural rubber/acrylonitrile butadiene rubber blends

The thermal behaviour of natural rubber/acrylonitrile butadiene rubber (NR/NBR) was studied using thermogravimetry (TG) and differential scanning calorimetry (DSC) in terms of blend ratio, crosslinking systems, fillers and compatibilizer (neoprene) were analyzed. The presence of NBR markedly increases the thermal stability of their blends and it lies in between NR and NBR. DSC studies revealed the thermodynamic immiscibility of the NR/NBR blends by the presence of two distinct glass transition temperatures and the immiscibility was prominent even in the presence of a compatibilizer.     

Thermal characterization of polypropylene/vermiculite composites

Vermiculite clay (VMT) was organically modified with a quaternary organic salt and added to polypropylene (PP). The compounds were prepared by melt intercalation using a twin extruder. The morphology of the composites was investigated through wide-angle X-ray diffraction (WAXD). The WAXD results suggested that exfoliation phenomena were found for the composites with modified clay. The thermal properties of the obtained composites were studied by means differential scanning calorimetry (DSC) and thermogravimetry (TG) measurements. A variation in the crystallinity of PP was found. A significant increase of the thermal stability of PP was achieved in the presence of the modified VMT.     

Thermal stability and oxygen resistance of polypropylene composites with fullerene/montmorillonite hybrid fillers

Journal of Thermal Analysis and Calorimetry - Silane coupling agent (KH-550) was used to connect fullerene (C60) with montmorillonite (MMT) to prepare C60-decorated MMT hybrid (C60-Si-MMT), and the...     

Thermal behaviour and microstructural characterization of lanthanide sulphides

Thermal decomposition processes of rare earth sesquisulfides Ln₂S₃ (Ln= Lu, Y and Er) in O₂ flow up to 1590 K, have been studied. Decomposition takes place through incomplete oxidations and overlapping decomposition reactions. Two intermediate phases such as Ln₂O₂S and Ln₂O₂SO₄ are formed before the final more stable phase Ln₂O₃ (C-type) is obtained. Microstructural studies show the poor crystallinity of the intermediate products.We wish to thank the Centro de Microscopia Electrónica, U.C.M.) for facilities. This research was supported by the CYCIT project MAT 89-0768.     

Mechanical and thermal properties of green polylactide composites with natural fillers

Green composites of PLA with micropowders derived from agricultural by-products such as oat husks, cocoa shells, and apple solids that remain after pressing have been prepared by melt mixing. The thermal and mechanical properties of the composites, including the effect of matrix crystallization and plasticization with poly(propylene glycol), have been studied. All fillers nucleated PLA crystallization and decreased the cold-crystallization temperature. They also affected the mechanical properties of the compositions, increasing the modulus of elasticity but decreasing the elongation at break and tensile impact strength although with few exceptions. Plasticization of the PLA matrix improved the ductility of the composites.     

Thermal characterization of rubberwood-polymer composites

The thermal properties of five types of radiation-induced wood-polymer composites based on a tropical hardwood, rubberwood (Hevea braziliensis), was studied by oxygen index measurement, differential thermal analysis (DTA) and thermogravimetry (TG). The DTA and TG curves of composites were different from those of rubberwood, which can be attributed to the presence of the incorporated polymers. Of the five composites, the one impregnated with bis(2-chloroethyl)vinyl phosphonate reduced the initial temperature of decomposition, increased the peak temperatures of exothermic reactions, and increased the char yield. Comparison with physical blends of rubberwood and the corresponding polymer provided some evidence of chemical interaction of wood and polymer in some of the composites.     

Thermal characterization of dental composites by TG/DTG and DSC

Dental composites can be improved by heat treatment, as a possible way to increase mechanical properties due to additional cure (post-cure). Direct dental composites are essentially similar to the indirect ones, supposing they have the same indication. Therefore, to establish a heat treatment protocol for direct composites, using as indirect (photoactivated by continuous and pulse-delay techniques), a characterization (TG/DTG and DSC) is necessary to determine parameters, such as mass loss by thermal decomposition, heat of reaction and glass transition temperature (T _g). By the results of this study, a heat treatment could be carried out above 160 °C (above T _g, and even higher than the endset exothermic event) and under 180 °C (temperature of significant initial mass loss).     

Polymer blends of sPS/PA6 compatibilized by sulfonated syndiotactic polystyrene

Syndiotactic polystyrene (sPS) and polyamide-6 (PA6) are immiscible and incompatible and have been recognized. In this study, sulfonated syndiotactic polystyrene (SsPS-H) is employed as compatibilizer in the blend of sPS/PA6. During melt blending, the sulfonic acid groups of the SsPS-H can interact strongly with the amine end-groups of PA6 through acid-base interaction. In addition, SsPS-H is miscible with sPS when SsPS-H content is less than 20 wt.%. Therefore, the addition of SsPS-H to sPS/PA6 blends reduces the dispersed phase size and improves the adhesion between the phases. The glass transition temperatures of the PA6 component in the compatibilized blends shift progressively towards higher temperature with the content of SsPS-H-12 increase, indicating enhanced compatibility. On the other hand, the progressive lowering of the melting point and crystallization temperatures of PA6 in the blends with increasing SsPS-H contents compared to the incompatibilized blend, provide some insight into the level of interaction between the PA6 and SsPS-H. The compatibilized blends have significantly higher impact strength than the blends without SsPS-H. The best improvement in the impact strength of the blends was achieved with the content of the SsPS-H (11.9 mol%) about 5 wt.%.     

Utilization of polymeric composites with fillers made of reproducible natural raw material

The rheological and surface properties of polymeric compositions were studied which were based on aqueous solutions of polyvinyl alcohol, carboxymethyl cellulose, or polyacrylamide with fillers made of reproducible natural raw material.     

Thermal and spectroscopic characterization of polypropylene-carbon nanotube composites

Thermogravimetric (TG) and varied temperature Raman spectroscopic measurements of melt-blended polypropylene composites (PP) with double wall (DWNT) and multi-wall carbon nanotubes (MWNT) revealed that the incorporation of carbon nanotubes into polymer matrix increased the thermal stability comparing to the virgin polypropylene. The characterization of reference nanotubes was also done by Raman microscopy and TG measurements. Varied temperature rheological analysis provided further information about the thermal decomposition of the composites indicating the formation of high strength char in case of MWNT and limited applicability of DWNT at high temperature. The residue of the decomposition of PP-MWNT nanocomposites consists of nanotubes of spectroscopically higher purity comparing to the original one indicating the thermally induced chemical changes in the solid phase.     

Thermal and mechanical properties of particulate fillers filled epoxy composites for electronic packaging application

Epoxy composites containing particulate fillers‐fused silica, glass powder, and mineral silica were investigated to be used as substrate materials in electronic packaging application. The content of fillers were varied between 0 and 40 vol%. The effects of the fillers on the thermal properties—thermal stability, thermal expansion and dynamic mechanical properties of the epoxy composites were studied, and it was found that fused silica, glass powder, and mineral silica increase the thermal stability and dynamic thermal mechanical properties and reduce the coefficient of thermal expansion (CTE). The lowest CTE value was observed at a fused silica content of 40 vol% for the epoxy composites, which was traced to the effect of its nature of low intrinsic CTE value of the fillers. The mechanical properties of the epoxy composites were determined in both flexural and single‐edge notch (SEN‐T) fracture toughness properties. Highest flexural strength, stiffness, and toughness values were observed at fillers content of 40 vol% for all the filled epoxy composites. Scanning electron microscopy (SEM) micrograph showed poor filler–matrix interaction in glass powder filled epoxy composites at 40 vol%. Copyright © 2007 John Wiley & Sons, Ltd.     

Evolution of phase dimensions and interfacial morphology of polypropylene/polystyrene compatibilized blends during mixing

The morphology development of polypropylene/polystyrene (PP/PS) blends was studied by means of effective mathematics methods. Time resolved fracture morphology measurements on PP/PS (20/80) blends compatibilized with styrene-butadiene-styrene block copolymer (SBS) suggested that PP/SBS domains acted as a warehouse supplying compatibilizer (SBS) to the phase boundary in the initial stage of mixing and promoted the formation and development of the transition layer. The development of the transition layer leaded to a more complicated morphology of fracture surface and strengthened the adhesion between phases, which was quantitatively investigated using Brown fractal dimension D_Brown. In the early stage of the mixing (<2.0 min), the mean chord length Λ_m used to describe the domain size decreased; simultaneously, the distribution of Λ trended to uniform as the mixing proceeded. After 2.0 min, Λ_m fluctuated in a definite range. Further, a normalized distribution of dimensionless domain sizes Λ/Λ_m was independent of mixing time, indicating that the late stage of phase dispersion can be scaled with a time-depended single length parameter Λ_m. In other words, the morphology development shows a possible dynamic scaling behavior.     

Investigation of natural rubber composites with addition of montmorillonite fillers using thermal analysis

This paper is devoted to the investigation of the properties of the natural rubber composites prepared using the cation exchanged-montmorillonite fillers. The characteristics of the montmorillonite fillers were studied by Fourier transform infrared spectroscopy (FTIR) and thermogravimetry (TG). These characterized fillers were used to preparation of the natural rubber composites, which were submitted to measurements of dynamic-mechanical thermal analysis (DMTA) and vulcanizing characteristics (M _H, M _L, t _s, t _c(90), R _v) as well as physico-mechanical properties (tensile strength, modulus at 300 elongation—M ₃₀₀, tensibility).     

Dynamic mechanical properties of sulfonated polystyrene/alumina composites

Amino units were grafted onto the surface of small particle size alumina by reaction with 3-aminopropyltriethoxysilane. Atactic polystyrene (PS) was sulfonated (1-14 mol% sulfonation) and mixed with both modified and unmodified alumina at filler loadings varying from 30 to 80 wt %. The resulting composites were characterized by differential scanning calorimetry, Fourier transform infra-red spectroscopy, and dynamic mechanical spectroscopy in the glass transition region at a frequency of 1 Hz. Whereas mixtures of unsulfonated PS with either filler showed essentially no change in T_g with filler content, sulfonated PS saw its T_g increase as a function of filler loading at a rate which was greater following modification of the alumina. At a fixed filler loading of 30 wt%, the composite rubbery plateau modulus was found to increase with copolymer sulfonic acid content, while the loss tangent maximum corresponding to the glass transition broadened and decreased. These observations were interpreted as a manifestation of the decrease in polymer mobility brought upon by the formation of noncovalent crosslinks resulting from the proton transfer from the sulfonic acid units on the polymer to hydroxyl and/or amino units at the surface of the filler. © 1994 John Wiley & Sons, Inc.     

Thermal properties and microhardness of HDPE/clay nanocomposites compatibilized by different functionalized polyethylenes

The calorimetric characteristics, the flammability, the thermal stability and the microhardness of polyethylene high density/clay nanocomposites (HDPE/clay) have been studied by differential scanning calorimetry, thermogravimetry, determination of limiting oxygen index and microhardness tests. The nanocomposites have been compatibilized by ethylene–acrylic acid copolymer (EAA), acrylic acid grafted HDPE (HDAA) and maleic anhydride grafted HDPE (HDMA). The clay was montmorillonite Cloisite 15A. The influence of the presence and the type of the compatibilizers on the properties of the nanocomposites has been evaluated. The results have shown that the thermal stability, the reduction of the flammability and the microhardness of HDPE/clay nanocomposites, compatibilized by HDAA and HDMA are higher than those for nanocomposite compatibilized by EAA. Moreover, the presence and the type of compatibilizer have negligible effect on the characteristics of the HDPE phase transitions. These results have been interpreted by the better clay dispersion and higher level of clay exfoliation in the presence of compatibilizers HDAA and HDMA, than those in the presence of EAA compatibilizer.     

Thermal analysis and microstructural characterization of ceramic green tapes prepared by aqueous tape casting

In this study, aqueous lead magnesium niobate (PMN) slurry formulations were developed for tape casting using a poly(acrylic acid) - poly(ethylene) oxide comb polymer as the dispersant, nonionic acrylic latex as the binder phase and hydroxypropyl methylcellulose as the wetting agent. Concentrated suspensions were cast onto a silicone-coated mylar film, and the effect of acrylic latex on deposition was investigated. Thermal analyses were performed to investigate the mass loss of the green tapes as a function of calcination temperature. Differential scanning calorimetric analyses were made under air and nitrogen atmospheres to investigate the binder distribution through the green tapes. Results showed that it is possible to prepare flexible, crack free PMN thick films using a proper slurry composition in the presence of acrylic latex binder, without using any plasticizer. Additionally, decomposing mechanisms of the acrylic based binder were essentially different in the two atmospheres.