Various Amounts Of Clay Research Articles

Fabrication of co-continuous morphology of polysulfone/nylon 6, 6 nanocomposites by varying the concentration of organically modified clay content

A unique morphology was fabricated using melt mixing of polysulfone (PSU) and nylon 6, 6, as well as organically modified clay to produce two blended nanocomposite compositions (80/20 and 60/40 w/w) of polysulfone and nylon 6, 6. The morphology of PSU/Nylon 6, 6 blend nanocomposites with various amounts of clay has been examined using scanning electron microscope (SEM), transmission electron microscope (TEM), and wide-angle X-ray diffraction (WAXD). In the case of 80/20 (w/w) PSU/Nylon 6, 6 without clay, the Nylon 6, 6 is dispersed in the PSU matrix with an average particle size of about 6.81 micrometers (μm). After adding clay (2%, 4%, and 8%), the domain size of nylon 6, 6 decreases, although the decrease rate is much slower than initially observed. However, we discovered that when the organoclay level exceeds 2%, the matrix-domain structure transforms into a co-continuous morphology for the 60/40 (w/w) blends. The TEM studies clearly demonstrate that the organoclay preferentially positions itself in the nylon 6, 6 phase, exhibiting a high degree of exfoliation, while the PSU phase of the nanocomposites remains devoid of clay, irrespective of the amount present. This study indicates that the size of clay platelets dispersed in the PSU/Nylon 6, 6 blend plays an important role in determining the morphology and stability of these blends. Moreover, the co-continuous structures were stable against further annealing at high temperatures, thus inhibiting the coalescence of the dispersed phase in addition to reducing interfacial tension.

Controlled release of paroxetine from chitosan/montmorillonite composite films

Controlled drug delivery studies popular in pharmaceutical area; polymeric composites prepared with clay has a great potential importance in drug release studies. The aim of the study is to produce biocoposite material suitable for controlled release of Paroxetine Hydrochloride.In this study, chitosan/clay/paroxetine (CS/MMT/PHH and CS/NaMMT/PHH) composite films were prepared to investigate drug release properties of paroxetine (PHH). Films containing various amounts of clay (MMT/NaMMT) (0, 0.1, 0.2, 0.4 g) and glycerol (0.25, 0.50) were prepared by solvent casting method. The structural properties of drug-containing and non-drug containing films were characterized by FT-IR and SEM analysis. The release studies of PHH were done in vitro and pH 7.4 and at 37 °C temperature. The highest percent of drug release was observed with CS/PHH film after 170 h (69%). It was observed that the drug release profiles of chitosan films containing clay (MMT or NaMMT) were better than films without clay. In order to investigate the drug release mechanism, Korsmeyer-Peppas, Higuchi, Zero and First order kinetic models were used.It was determined that release kinetics of the most of films fit the Korsmeyer-Peppas model, and according to this model, drug release occurs through two mechanisms, swelling-controlled and diffusion-controlled. It has been observed that all films containing clay have long-term drug release. Increasing in clay ratio in the composite, caused decrease in drug release rate. PHH loaded CS/MMT/PHH and CS/NaMMT/PHH films showed steady and prolonged drug delivery. Results indicated that prepared CS/MMT/PHH and CS/NaMMT/PHH films has a potential to act as suitable carrier for drugs.

Saponin Versus Rhamnolipids for Remediation of Cd Contaminated Soils

Cadmium should be effectively removed from soil because it is one of the most toxic soil pollutants. Thus, the present study compared a plant (saponin, SAP) and a microbial (rhamnolipids, RAM) biosurfactant for Cd removal from three different types of soil. Batch washing was tested under different operational conditions: Biosurfactant concentration, 0.1–10% SAP, 0.01–1% RAM; washing time, 0.1–6 h; soil dosage, 12.5–100 g L−1; biosurfactant pH, 2–9 for SAP, 5.5–12 for RAM; washing number, three with SAP, four with RAM. SAP removed Cd from the soils more effectively than RAM because it can be used at a higher concentration and a more acidic pH. Soil washing with SAP also has a shorter equilibrium time (10–90 min.) than washing with RAM (50–300 min), and higher kinetic rate constants (0.23–4.9 kg mg · h−1 for SAP, 0.12–0.25 kg mg · h−1 for RAM). With an increase in soil dosage, Cd removal from all soils decreased significantly with both SAP and RAM. Multiple soil washings improved Cd removal. The predicted optimum number of washes depended on the criteria for soil quality assessment, that is, total Cd concentration, Cd mobility or ecological risk. To meet all of these criteria, SAP needed fewer washes than RAM. SAP is more suitable than RAM for treatment of soils highly contaminated with Cd and containing various amounts of clay.

Nanostructural characterization of poly (vinylidene fluoride)-clay nanocomposites prepared by a one-step reactive extrusion process

Abstract Poly (vinylidene fluoride) (PVDF)-untreated clay nanocomposites were successfully prepared using an innovative one-step reactive melt extrusion process. Through specific temperature and shear conditions, the chemical reactions took place between the polymer matrix, the inorganic clay particles, and three main reactive agents: an organic peroxide, sulfur, and a specific activator led finally to the PVDF-clay nanocomposites. The materials were formulated with various amounts of clay in order to identify the best conditions, enabling to obtain the optimal particle exfoliation in the polymer matrix at the nanometric scale. The microstructure and nanostructure modifications were characterized by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), and wide- and small-angle X-ray scattering (WAXS and SAXS). The relationship between nanostructure and mechanical behavior was investigated by tensile experiments, impact tests, and microhardness measurements. The FTIR results suggest that there is a chemical interaction between the clay and the polymer. Furthermore, the WAXS study shows that no intercalation step takes place in any composition. In addition to this, the sample with 2.5 wt.% clay could present a total exfoliation of the clay particles. The PVDF matrix is found to be exclusively of the α-form in all compositions. The final microhardness slightly increases with both nanoclay content and degree of crystallinity.

Instrumentation and axial load testing of displacement piles

Despite the fact that results of many instrumented pile load tests have been reported in the literature, it is difficult to find well-documented instrumentation procedures that can be used when planning a load testing programme. A load test programme designed to investigate various aspects of the design and behaviour of driven steel piles is discussed in the present paper. Although the literature contains information on load testing of instrumented piles driven in either sand or clay, limited information is available regarding their axial load response in transitional soils (soils composed of various amounts of clay, silt and sand). Results are presented for fully instrumented axial load tests performed on an H pile and a closed-ended pipe pile driven into a multilayered soil profile consisting of transitional soils. In addition, the load testing planning, the instrumentation of the piles, the testing methods and the interpretation of the pile testing data are discussed in detail in the context of this and other load testing programmes described in the literature, in order to illustrate the various steps.

Synthesis and characterization of poly(trimethylene terephthalate)/organoclay nanocomposite via in situ polymerization

Neat poly(trimethylene terephthalate) (PTT) and PTT/modified organoclay nanocomposite with various amounts of clay were synthesized by a two-step procedure. Terephthalic acid (TPA) was reacted with 1,3-propanediol (1,3-PDO) in the esterification step. Then, polycondensation reaction resulted in the formation of PTT in the presence of tetra buthyl titanate (Ti(OC4H9)4) as a catalyst. Commercially available organoclay (Cloisite 30B) was modified using 3-aminopropyltriethoxysilane via a silylation reaction. Thermal stability of modified clay was studied by means of thermal gravimetric analysis (TGA) that showed 10% less weight loss than Cloisite 30B. PTT/organoclay nanocomposites with 0.5, 1 and 2 wt% of modified organoclay were prepared by in situ polymerization. Synthesized polyesters were characterized by Fourier-transform infrared spectroscopy and proton-nuclear magnetic resonance spectroscopy (1H-NMR). Number average molecular weights were determined by 1H-NMR and a new Mark–Houwink equation is reported for highly pure dichloroacetic acid as solvent at 25°C. Polymer’s morphology was examined with x-ray diffraction and transmission electron microscopy. It was observed that clay layers were not accumulated. Thermal properties and crystallization behavior were investigated by differential scanning calorimetry and TGA. Crystallization temperature ( Tc) of nanocomposites increased about 6°C compared to neat PTT that reflects greater overall crystallization. Modified Averami Equation was used to describe crystallization kinetics and crystal size was studied using polarized optical microscopy. It was observed that crystal size reduces with nanoclay content. PTT mostly is used as polymeric fiber. Hence, dyeability of neat PTT and nanocomposites was investigated using a spectrophotometer. About 32% increase in color uptake was determined.

Dry Sliding Behaviors of PDCPD Nanocomposite Prapared by RIM

Reaction injection molding (RIM) is a rapid processing technique for the formation of polymer parts by direct polymerization in the mold. Polydicyclopentadiene (PDCPD)/Clay nanocomposites with various amounts of clay were synthesized with a Gusmer-Decker machine by RIM, and the specific injection conditions of the nanocomposites were obtained. The results of X-ray diffraction (XRD) diagrams of the nanocomposites showed that clay were completely exfoliated. The tribological behaviors of PDCPD nanocomposites were studied using an MM-200 friction and wear tester. The experimental results showed that the wear mass loss of nanocomposites reach the minimum while the MMT content of the nanocomposites is 1wt%. The values of friction coefficient almost keep constant within the range of MMT content as added.The worn surface of PDCPD nanocomposites was examined with a scanning electron microscope (SEM) and the friction and wear mechanism was discussed.

Preparation and Properties of Chloroprene Rubber (Cr)/Clay Nanocomposites

Chloroprene rubber (CR)/organic modifier/sodium montmorillonite (NA-MMT) nanocomposites were prepared by melt intercalation. The morphology of the nanocomposites was studied using X-ray diffraction (XRD) and transmission electron microscopy (TEM). TEM results showed that the silicate layers of the clay were dispersed in the CR matrix on the nano-scale by adding the organic modifier. X-ray diffraction also indicated that the silicate layers of clay were exfoliated. The mechanical and thermal properties of the nanocomposites could be therefore improved by adding clay and organic modifier, as the silicate layer of the clay was uniformly dispersed. Dynamic mechanical analysis was further performed to investigate the thermomechanical properties of CR–clay nanocomposites containing various amounts of clay. The glass-transition temperature of CR– clay nanocomposites increased with increasing amount of clay and organic modifier.

The effect of montmorillonite and compatibilizer quantities on stiffness and toughness of polyamide nanoblends

AbstractAlthough polymer blend nanocomposites are widely studied, the balance between stiffness and toughness has not yet been investigated in detail. Some materials producers as well as some sectors in the automotive industry try to improve the toughness of materials without an important loss in stiffness. With this in mind, the aim of the study reported here was to obtain a good balance between toughness and stiffness of polymer blends with different amounts of clay and compatibilizer. In this context, the microstructure of polyamide 6/ethylene–propylene–diene metallocene terpolymer/(ethylene–propylene–diene copolymer)‐graft‐(maleic anhydride) blends with various amounts of clay (2, 3, 4 and 5 wt%) and compatibilizer (10 and 20 wt%) was studied to analyse the achieved morphology to understand the macroscopic properties. The morphology of the rubber phase and the dispersion of the montmorillonite (MMT) are the main factors that influence the mechanical properties. In this sense, the highest Young's modulus is achieved for nanoblends with 5 wt% of MMT, although this nanoblend has the lowest value of notched Izod impact strength. The results obtained suggest that there is a clear trade‐off between stiffness, toughness and temperature behaviour when the ratio of (ethylene–propylene–diene copolymer)‐graft‐(maleic anhydride) to MMT is 5:1. Copyright © 2009 Society of Chemical Industry

Assessment of the Axial Load Response of an H Pile Driven in Multilayered Soil

Most of the current design methods for driven piles were developed for closed-ended pipe piles driven in either pure clay or clean sand. These methods are sometimes used for H piles as well, even though the axial load response of H piles is different from that of pipe piles. Furthermore, in reality, soil profiles often consist of multiple layers of soils that may contain sand, clay, silt or a mixture of these three particle sizes. Therefore, accurate prediction of the ultimate bearing capacity of H piles driven in a mixed soil is very challenging. In addition, although results of well documented load tests on pipe piles are available, the literature contains limited information on the design of H piles. Most of the current design methods for driven piles do not provide specific recommendations for H piles. In order to evaluate the static load response of an H pile, fully instrumented axial load tests were performed on an H pile (HP 310 × 110) driven into a multilayered soil profile consisting of soils composed of various amounts of clay, silt and sand. The base of the H pile was embedded in a very dense nonplastic silt layer overlying a clay layer. This paper presents the results of the laboratory tests performed to characterize the soil profile and of the pile load tests. It also compares the measured pile resistances with those predicted with soil property- and in situ test-based methods.

Preparation and properties of styrene–ethylene–butylene–styrene block copolymer/clay nanocomposites: I. Effect of clay content and compatibilizer types

AbstractBACKGROUND: Polymer/clay (silicate) systems exhibit great promise for industrial applications due to their ability to display synergistically advanced properties with relatively small amounts of clay loads. The effects of various compatibilizers on styrene–ethylene–butylene–styrene block copolymer (SEBS)/clay nanocomposites with various amounts of clay using a melt mixing process are investigated.RESULTS: SEBS/clay nanocomposites were prepared via melt mixing. Two types of maleated compatibilizers, styrene–ethylene–butylene–styrene block copolymer grafted maleic anhydride (SEBS‐g‐MA) and polypropylene grafted maleic anhydride (PP‐g‐MA), were incorporated to improve the dispersion of various amounts of commercial organoclay (denoted as 20A). Experimental samples were analyzed using X‐ray diffraction and transmission electron microscopy. Thermal stability was enhanced through the addition of clay with or without compatibilizers. The dynamic mechanical properties and rheological properties indicated enhanced interaction for the compatibilized nanocomposites. In particular, the PP‐g‐MA compatibilized system conferred higher tensile strength or Young's modulus than the SEBS‐g‐MA compatibilized system, although SEBS‐g‐MA seemed to further expand the interlayer spacing of the clay compared with PP‐g‐MA.CONCLUSION: These unusual results suggest that the matrix properties and compatibilizer types are crucial factors in attaining the best mechanical property performance at a specific clay content. Copyright © 2007 Society of Chemical Industry

Fault gouge evolution in highly overconsolidated claystones

Processes of fault gouge evolution in hard claystones start with cataclasis that produces a soft clay gouge which fills the space between the initial fragments. This re-seals the initially highly porous and permeable damage zone, without diagenetic processes. We studied this process in shales and sandstones, deformed in normal faults after uplift to shallow crustal depths in the Ardennes and Eifel. Detailed mapping shows four different lithotypes from intact shale in the wall rock, broken wall rock fragments with various amounts of clay, to a fully reworked gouge. These lithotypes reflect different evolutionary stages. The similar mineralogy of the different lithotypes suggests that the main process involved is mechanical fragmentation with minor contribution by diagenetic changes or weathering, accompanied by large changes in microstructure, porosity and transport properties. While the wall rock has a very low porosity and permeability, initial deformation results in a much higher porosity with large pores. The reworked clay gouge also has a high porosity, but its pore size corresponds to a lower permeability and higher capillary seal capacity. In upper crustal fault zones in strong, brittle lithologies, this early re-sealing in sections consisting of claystone will lead to local barriers to along-fault fluid flow.

Novel morphologies of poly(phenylene oxide) (PPO)/polyamide 6 (PA6) blend nanocomposites

Poly(phenylene oxide) (PPO)/polyamide 6 (PA6) (50/50 w/w) blend nanocomposites were prepared by melt mixing of PPO, PA6, and organically modified clay. The morphology of PPO/PA6 nanocomposite with various amounts of clay has been investigated using scanning electron microscope (SEM), transmission electron microscope (TEM), and wide-angle X-ray diffraction (WAXD). For the PPO/PA6 blend without clay, PPO is dispersed in the PA6 matrix with an average particle diameter of about 4.2μm. The domain size of the dispersed PPO phase is significantly decreased to about 1.1μm by adding a small amount of clay (2%). However, when the amount of organoclay is more than 5%, the matrix-domain structure is found to transform into the co-continuous morphology. The TEM observation shows that all the organoclay is dispersed only in the PA6 phase with a high degree of exfoliation and there is no any clay detectable in the PPO phase for the nanocomposites regardless of the amount of clay. It is considered that the dispersed clay platelets play an important role in the control of the PPO/PA6 blend morphology. Firstly, the selective localization of clay in PA6 phase changes the viscosity ratio of the PPO and PA6 phases. Therefore, clay has significant effects on the morphology of the polymer blend. Secondly, the high aspect ratio of the clay platelets prevents the coalescence of domains during melt mixing.

Modulus Anisotropy and Shear Stability of Geofiber-Stabilized Sands

A systematic laboratory approach is established to evaluate shear stability or bearing capacity improvement of sand-geofiber stabilization for rapid road and airfield construction. The approach deals with the investigation of directional dependency, anisotropy, and modulus properties and links stability to shear stress levels typically applied on specimens during testing in relation to their strength. An advanced triaxial testing machine referred to as the University of Illinois FastCell is used together with direct shear tests for determining the anisotropic resilient moduli and the strength properties of two geofiber-reinforced sands (poorly and uniformly graded sands) prepared with three 51-mm geofibers: fibrillated, monofilament, and tape. The use of different geofiber types and the various amounts of clay and silt fines present in the sand mixtures significantly affected the recorded horizontal and vertical moduli and the shear stresses at applied stress states. Monofilament-type geofiber stabilization was found to be the most effective, with the recorded highest vertical moduli and the highest shear strength and stability improvement indicated by the lowest shear stress ratios, especially when mixed with 10% to 20% clay. The tape-type geofiber reinforcement generally was not very effective. For the geofiber stabilization of sands to be a viable construction alternative, the sand-geofiber mixtures should contain an optimal amount of fines needed for geofibers to mobilize the shear strength of the mix effectively and thereby improve the shear stability and resistance to permanent deformation.

Successful Stimulation of Fordoche Field With a Retarded HF Acid

Summary A sequential hydrofluoric acid (SHF) system yielded large-scale success in the Fordoche field in south Louisiana. The SHF was successful on 19 of 22 wells treated in various reservoirs, with an average 2.5-fold production increase. Fordoche reservoir characteristics, substantial production data on the SHF and other stimulation attempts, and some mechanical considerations that required careful engineering planning are presented. Introduction A retarded clay-dissolving system was developed for stimulating oil and gas production from deep clay-damaged sandstone formations. The SHF system uses the ion-exchange properties of clay minerals to generate in-situ hydrofluoric acid (HF) on the clay mineral by pumping alternate stages of hydrochloric acid (HCl) and ammonium fluoride into the formation.Fordoche field has been on production since 1966. Cumulative oil production through Dec. 1979 is more than 25 million bbl. The production is from deep, high-pressure, low permeability, multilayered sandstone formations. Initially, production was high (12,000 BOPD), but it rapidly declined as a result of declining bottomhole pressure (BHP) and formation damage. A gas injection program was begun in 1971 to stabilize the BHP's. To counter the formation damage, several stimulation treatments were attempted, including regular HF, HCl, sand fracture, solvent, isopropyl acetate, and acetic anhydride. These treatments were either temporarily successful or unsuccessful. In addition, frequent mechanical problems required expensive well repairs. Stimulation treatments with SHF began at Fordoche in 1977, and of 22 producing wells treated, 19 were successful. Average increase in production for the 22 wells was 2.5-fold, with a payout of 11 days. Reservoir Characteristics The Fordoche field is located in Pointe Coupee Parish, LA (Fig. 1). Initial production began in Jan. 1966. The field was developed with 55 oil completions and seven gas completions in 36 wellbores drilled to an average depth of 14,200 ft. The 3,520 surface acres contain seven pay zones in the Sparta and Wilcox Eocene formations. Fig. 2 is a typical well log showing these sands. Successful SHF stimulation was performed on both the Sparta and Wilcox formations. Basic reservoir data for the Sparta B and Wilcox 8 (W-8) sands (Table 1) indicate major differences between the two reservoirs.The Wilcox sands consist of two gas-condensate reservoirs (W-4 and W-5) and three oil reservoirs (W-8, W-12, and W-15). The five intervals are similar reservoir properties. They all are of deltaic origin and vary from slightly shaly and fine grained to silty, consolidated sandstone and contain various amounts of clay. The mineralogy of core material from the W-8 sand is shown in Table 2. Laboratory core studies indicate a high solubility of the W-8 formation with HF (Table 2).The Wilcox sands exhibit high original BHP's (9,400 to 11,000 psia) and temperatures (250 to 280 degrees F). Studies indicated that these reservoirs are very sensitive to water; oil production rates have decreased drastically when wells produced more than 2 % water. The wells' tendency to plug limits production and necessitates frequent stimulation to restore wells to commercial production. JPT P. 1485^