Clay Reinforcement Research Articles

Photo-oxidative degradation of organo-functionalized vermiculite clay-reinforced polyimide composites

Herein, accelerated photo-oxidation under UV light of polyimide (PI) films filled with functionalized vermiculite (VMT) clay (i.e., 1–7 wt %.) were examined from 0 to 600 h. Thick films (⁓ 60 µm) were fabricated and exposed to accelerated UV light (λ > 295 nm). The as-synthesized PI-reinforced clay nanocomposites were examined by Fourier transform infrared (FT-IR), scanning surface micrograph (SEM), yellowing index, and thermogravimetric analysis (TGA), respectively. The surface morphology examined by SEM exhibits well exfoliation of VMT clay in the PI matrix. The change in internal chemistry on a higher temperature and clay composition is found to be the result of the aggregation of clay. The yellowing index determined by UV–Vis spectroscopy followed a similar tendency as the carbonyl index. TGA analysis revealed good heat resistance in clay-based PI due to the lower thermal expansion of clay reinforcement. Overall, the data clearly showed a better photo-stability of the developed clay/PI composites over the pristine polymer. It is concluded that clay-based PI could be a better alternative in applications requiring harsh conditions, as clay has improved the oxidative, thermal, and insulation properties of the PI matrix.

Shear characteristics and stress-strain mathematical model of waste polyester textile reinforced clay

Clay reinforcement through appropriate applications of waste fiber or waste fiber fabric can generate huge economic and environmental benefits. In this study, clay was reinforced using waste polyester fiber filaments and waste polyester fabric blocks, respectively. Triaxial tests (σ1 > σ2 = σ3) were carried out to examine the influence of reinforcement method and the contents (0.0%, 0.5%, 1.0%, 1.5%) on the shear behavior of clay. After reinforcement, the deformation resistance and shear strength of the clay was improved. The optimal contents of fiber filament and fabric block were both 1.0%; as the fiber filament or fabric block content increased from 0.5% to 1.5%, the stiffness of the reinforced clay decreased, while the energy absorption capacity and the cohesive strength first increased and then decreased. Under the optimal content condition, the fiber filament showed better reinforcement than the fabric block. Under the train hardening condition, a hyperbolic model can be used to quantitatively describe the stress-strain relationship of the reinforced clay, and the model parameters can also reflect the strain hardening degree.

Stochastic multiscale modeling of heat conductivity of Polymeric clay nanocomposites

We propose a stochastic multi-scale method to quantify the most significant input parameters influencing the heat conductivity of polymeric nano-composites (PNCs) with clay reinforcement. Therefore, a surrogate based global sensitivity analysis is coupled with a hierarchical multi-scale method employing computational homogenization. The effect of the conductivity of the fibers and the matrix, the Kapitza resistance, volume fraction and aspect ratio on the ’macroscopic’ conductivity of the composite is systematically studied. We show that all selected surrogate models yield consistently the conclusions that the most influential input parameters are the aspect ratio followed by the volume fraction. The Kapitza Resistance has no significant effect on the thermal conductivity of the PNCs. The most accurate surrogate model in terms of the R2 value is the moving least square (MLS).

STRENGTH OF SOFT CLAY REINFORCED WITH 10 MM SINGLE CRUSHED COCONUT SHELL (CCS) COLUMN

Stone column can be used as a ground improvement technique where a portion of soft soil is replaced with granular material such as stone or sand. The benefit of using stone columns in low strength soil has been proven as an efficient method to improve the bearing capacity and reduce settlement of soft soils. This study aims to investigate the improvement in shear strength of soft clay by embedded with a single crushed coconut shell (CCS) column. The cost of soil improvement can be reduced because of CCS is a waste material. This paper was done by determining the physical and mechanical properties of kaolin and CCS as well as the effect of height penetration ratio of a single CCS column on shear strength characteristics. Unconfined Compression Test (UCT) was conducted for 4 batch kaolin samples including a control sample in order to determine the shear strength. Each batch involved four samples to find the accurate value. The research variables are the height of crushed coconut shell column which is 60 mm, 80 mm and 100 mm where the column penetration ratio is 0.60, 0.80 and 1.00 respectively. A total of 16 unconfined compression tests had been conducted on kaolin sample with dimensions of 50mm in diameter and 100 mm in height. The increment of shear strength by embedded with crushed coconut shell columns is 19.02 %, 34.76 % and 24.34 % for with 4 % area displacement ratio at column penetration ratio of 0.60, 0.80 and 1.00 respectively. From the results obtained, the relationship between shear strength increases is influenced by the height of the column. The maximum column height (full penetration) does not generate the highest strength and it proves that critical column length theory is true in this study.

Development of Optimum Combination of MMT Clay Reinforced Composite

The Montmorillonite (MMT) clay toughened epoxy (85%) / unsaturated polyester (15%) polymer blend system is developed. Studies on Mechanical, Thermal and Damping properties are conducted to determine the effect of the variations of MMT clay on the polymer blend. The Mechanical property studies showed that 3% clay reinforced polymer blend system exhibited optimum results, while the Damping property studies showed that 4% clay reinforced polymer blend system exhibited optimum results and Thermal property studies revealed that 5% clay reinforced polymer blend system exhibited optimum results. The prime objective of this work is to validate the obtained experiment results and to identify the best-fit combination. The results are validated by using Design Expert Version 8 Software. Validation of the experimental results, indicate negligible variations with the software generated results. Since different variations of clay percentages are achieved for different properties, a decision table is constructed to determine the best-fit combination suitable for the selected applications.

An Experimental Study on Geogrid with Geotextile Effects Aimed to Improve Clayey Soil

The increase of shear strength in soil, reinforced with the geogrid (alternate reinforcer), is resulted from an increase of modulus of soil hardness, and also from the tensile strength of reinnforcer. The shear strength of contact surface in soil appears due to both the friction strength against the contact surface, and the passive strength formed in front of the elements of the geogrid system. In the clay reinforced with a geogrid, the resistance of the contact surface is low; therefore, contact surface rupture occurs before the tensile strength reaches the ultimate limit. Also, the geogrid is almost ineffective in limiting particles movement and creating passive resistance in clay, due to a big difference in the sizes of geogrid opening (a perture) comparing to clay grains. In this research, we tried to examine the effect of geotextile layers around the geogrid aimed to improve the soil-geogrid interaction in different drainage conditions by means of triaxle (UU) and (CD) trials on a large scale. Experiments were carried out, based on non-reinforced samples, geogrid-reinforced samples and geocomposite reinforced samples. The results of the experiments showed that the geotextile layers around the geogrid in the clay reinforcements not only effectively improved the interaction of contact surface, where the stresses are concentrated on the geogrid, but enhanced the shear strength parameters, the consolidation and drainage processes, as well. Radiographic results taken from fractal samples indicated that the rupture plate gets a reflection state in the reinforcing elements at the location of geocomposite configurations only, relative to the reinforcing elements. Meanwhile, the geogrid layers did not have any impact on the changes of rupture surface situation.

FORMULATION AND EVALUATION OF CHITOSAN-POLYPYRROLE NANOCOMPOSITES FOR CONTROLLED RELEASE OF ANTICANCER DRUG DOXORUBICIN

Objective: The purpose of the present study was a characterization of chitosan (CS)-polypyrrole (PPY) nanocomposites for controlled release of anticancer drug doxorubicin (DOX).
 Methods: Chitosan crosslink with PPY with montmorillonite (MMT) called as (CS-PPY/MMT) were formulated using the solvent casting method. The prepared nanocomposites were characterized by X-Ray Diffraction Analysis (XRD), tensile strength, scanning electronic microscope (SEM).
 Results: The XRD result confirmed that the CS-PPY/MMT possessed crystal structure. The nanocomposites CS-PPY/MMT-4 were showed a homogenous morphology. The Water uptake and swelling ratio of the CS-PPY and CS-PPY/MMT were found to decrease with increase in the concentration of clay. Mechanical properties of the CS-PPY and CS-PPY/MMT were assessed in terms of tensile strength and extensibility using texture analyzer. Increase in tensile strength and reduction in extensibility was reported with an increase in the nanoclay content. In vitro drug release study on CS-PPY and CS-PPY/MMT indicated pronounced sustained release of doxorubicin by the incorporation of clay particles in CS-PPY/MMT. It was observed that during the first 60 min of the dissolution study, the CS-PPY/MMT-4 film showed just 79.32±0.56% drug release as while the CS-PPY-1, CS-PPY/MMT-2 and CS-PPY/MMT-3 films showed a release of 53.79±1.23%, 63.51±1.24% and 68.15±2.38% respectively.
 Conclusion: CS-PPY/MMT nanocomposite films exhibited improved mechanical and sustained drug release properties than CS-PPY. The combination of biodegradable polymeric chains and clay reinforcement can be applied to achieve the desired combination of properties of materials used as a biosensor for diverse biomedical applications.

Mechanism of electro-osmotic chemical for clay improvement: Process analysis and clay property evolution

Electro-osmotic chemical methods were applied in a series of geotechnical studies in which various solutions were injected into clay samples, increasing the undrained shear strength of the clay. Such methods resulted in a series of phenomena and in clay property evolution. In this study the current, temperature, settlement, drainage volume, and electrical potential distribution during the electro-osmotic experiments were monitored as process data, and the electrical conductivity in clay, calcium content, pH, water content, and undrained shear strength after the electro-osmotic chemical experiments were measured as clay property evolution data. Based on the process data, clay property data, and relevant theories, the mechanism of clay reinforcement with electro-osmotic chemicals was comprehensively explained. The development of an electro-osmotic permeability coefficient difference and the permeable drainage boundary condition resulted in a negative pore water pressure distribution shaped as an arch, which resulted in the water content having the same distribution and induced settlement. Because of the gathering of Ca2+ and H+ near the anode, a chemical cement reaction occurred near the cathode. The electrical potential gradient near the anode was lower than that near the cathode. Because of the chemical cement reaction between Ca2+, OH−, and SiO32−, the undrained shear strength near the cathode was much higher than that near the anode. In addition, a coupling analysis of the electro-osmotic chemical process and clay property evolution is presented at the end of the discussion.

Mechanical Properties of Palm Oil Polyol based Polyurethane Foam Reinforced Wollastonite Clay

The palm oil polyol based polyurethane (PU) foam reinforced wollastonite clay was prepared to study the effects of wollastonite clay addition towards the mechanical properties of PU foam. The palm oil polyol based PU foam with NCO: OH ratio of 1:1.22 was synthesized by mixing palm oil-based polyol, p-MDI, DMCHA, PMDETA, distilled water and incorporation of different amount of wollastonite clay powder (1, 3, 5 and 7 wt%). The FTIR analysis showed the absence of NCO peak at 2280 cm−1 suggesting the complete conversion of isocyanates into urethane during the mixing process. Based on FESEM/EDX, it was found that the wollastonite clay were fitted into the PU matrix, whereby SEM showed an open cell structure of PU foam reinforced wollastonite clay. The density of PU foam reinforced wollastonite clay is increased as the amount of clay reinforcement is increased. This is due to the high viscosity of the mixture which hinder the foam from rising and hence produced a denser foam, thus reduced the pore sizes. Hence, the compressive strength increased as the density and wollastonite weight percentage in the foam is increased.

Fracture properties prediction of clay/epoxy nanocomposites with interphase zones using a phase field model

We predict the macroscopic tensile strength and fracture toughness of fully exfoliated nano silicate clay epoxy composites accounting for the interphase behavior between the polymeric matrix and clay reinforcement. A phase field approach is employed to model fracture in the matrix and the interphase zone of the polymeric nanocomposites (PNCs) while the stiff clay platelets are considered as linear elastic material. The effect of the interphase zones, e.g. thickness and mechanical properties (Young’s modulus and strain energy release rate) on the tensile strength, and fracture parameters of the composite is studied in detail. The dissipation energy due to fracture in the PNCs is extracted for different thicknesses and properties of the interphase zones. We show through numerical experiments that the interphase thickness has the most influence on the tensile strength while the critical strain energy release rate of the interphase zones affects the dissipation energy depending on the interphase zone thickness.

Enhancing mechanical properties of clay aerogel composites: An overview

Abstract While aerogel is a new classification of materials and considered most promising candidate for the advanced thermal insulation, clay aerogel shows significant potentials as it is natural, non-toxic, biodegradable and biocompatible material. To date most aerogels are produced through a supercritical drying process and most reviewed aerogels are silica based aerogels, nevertheless, more environmentally friendly aerogels have been attempted through the use of clays through an environmentally freeze-drying process. This paper presents a comprehensive overview of developing robust clay aerogels, including enhancing clay aerogel with various natural and synthetic polymers, and the reinforcement of clay–polymer aerogel with carbon nanotubes, natural fibres, glass fibre lamination and dip coatings. The results show that many factors could contribute to the classification of clay aerogels, including processing parameters and methodologies, raw materials as well as minor additives. One of the most significant setbacks regarding clay aerogels is their mechanical properties and in the past several years significant efforts have been spent on the improvement. The most successful method demonstrated so far was the incorporation of a water-soluble polymer and reinforcing aerogel composites with fibrous materials to achieve various levels of enhancements of clay-aerogels. This review shall provide a much useful concise database for the development, production and potential utilisation of clay aerogel for various industrial sectors.

Effect of Thermal Exposure on Tensile and Fatigue Properties of Clay Reinforced Nylon Nanocomposites

In this paper, both nylon 6 and 2 wt% clay reinforced nylon 6 matrix nanocomposite were used for thermal exposure tests at temperatures of 80 oC and 120 oC and 150 oC, respectively. Then, the tensile tests and fatigue tests of the exposed specimens were conducted at room temperature. It was shown that the tensile strength in both nylon 6 and NCH-2 decreased with an increase in thermal exposure temperature. The brittle fracture occurred in the specimens exposed at 120 oC and 150 oC. After pre-oxidation treatment at 80 °C for 100 hours, the fatigue strength decreased 14% in nylon 6, and 8% in NCH-2. From this result, it was understood that the addition of clay in nylon 6 could suppress the decrease of fatigue strengths.

Relaxation behavior in clay-reinforced polymer nanocomposites

The effect of clay reinforcement on dielectric, conductivity, and mechanical relaxation behavior of a polymer clay nanocomposite film is reported. Polymer nanocomposite is composed of three component polymers (polyacrylonitrile) as a host matrix, salt (LiPF6) as conducting species, and clay (sodium montmorillonite) as intercalant. The macroscopic parameters like polymer glass transition temperature and available free mobile charge carriers have been analyzed properly using dynamic mechanical analysis and dielectric analysis. Dielectric analysis indicated distribution of relaxation time as a function of clay concentration, whereas conductivity spectrum exhibited dispersion at lower frequency followed by saturation region at intermediate frequency. The dispersion behavior is related to the electrode polarization attributed to faster ion dynamics. The dielectric and conductivity relaxation are in excellent correlation with mechanical relaxation owing to the changes in glass transition temperature due to polymer-ion-clay interaction. The proposed mechanism is a sequel to the experimental results.

Synthesis and Characterization of New Ether Linked Tetraglycidyl Epoxy Silicate Nanocomposites

The objective of this work was to synthesize a tetraglycidyl 2,2-bis(4-(4 nitrophenoxy) phenyl)propane epoxy resin (TGBAPPP) from 2,2-bis(4-(4-aminephenoxy) phenyl) propane (BAPPP) and epichlorohydrin. The molecular structure of TGBAPPP epoxy resin was confirmed by FTIR and NMR spectroscopy and its molecular weight was determined by means of epoxy equivalent weight (EEW) titration, gel permeation chromatography (GPC) and ion trap mass spectrometry. The TGBAPPP epoxy resin was further reinforced with organically modified montmorillonite (OMMT) nano clay with varying weight percentages (1–5 wt %) and cured with di-aminodiphenylmethane (DDM). The thermo-mechanical behaviour of TGBAPPP epoxy resin and its nanocomposites was examined by means of dynamic mechanical analysis (DMA). The morphology of the epoxy nanocomposites was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies. The TGBAPPP epoxy resin having optimized nano clay reinforcement showed enhanced thermo-mechanical properties and appears to be an ideal candidate for advanced aerospace applications.

Water Absorption Behavior, Mechanical and Thermal Properties of Vinyl Ester Matrix Nanocomposites Based on Layered Silicate

The water absorption behavior, mechanical and thermal properties of vinyl ester matrix nanocomposites based on layered silicate were investigated. To characterize interlaminar structure of the nanocomposites, XRD, SEM, EDS, and TEM were performed. The mechanical and thermal properties of neat sample were improved by the incorporation of layered silicate. The improvement of the water repellence behavior was observed for the nanocomposites. The hardness and elastic moduli after water absorption was reduced due to the effect of water molecules entering into the polymer chains. However, the higher amount of clay reinforcement led to less reduction in hardness since the barrier properties.

Some Studies on Mechanical Properties of Epoxy/CTBN/Clay based Polymer Nanocomposites (PNC)

Rubber toughened blends of epoxy LY556 and carboxyl group terminated butadiene nitrile (CTBN) was selected as a system for this study. CTBN was used as toughening agent with different concentrations of CTBN with epoxy. 0, 5, 10, 15 and 20 parts per hundred parts resins (phr) are the combinations were prepared by varying CTBN content in epoxy. Jeffamine 300 was used as curing agent for epoxy/CTBN blends. Through optimization, it is found that 15 phr epoxy/CTBN shows improvement in mechanical properties, tensile properties and dynamic mechanical thermal analysis (DMTA). Furthermore, clay as nanofiller is optimized and found that 3wt % of clay with 15 phr epoxy/CTBN blends shows improvement in the mechanical properties. It may be due to good dispersion and highly exfoliation of clay in polymer nanocomposites (PNC). The clay reinforcement enhanced the glass transition temperature (Tg) of the material. And Tg was verified by using differential scanning calorimetric (DSC) and DMTA. To understand the interaction (exfoliation and dispersion) of the clay in the PNC, X-ray diffraction (XRD) and scanning electron microscopy (SEM) was carried out for few selective samples. The main aim is to optimize the system.

Mechanical, thermal and flame-retardant properties of epoxy–nylon fabric–clay hybrid laminates

Epoxy–nylon fabric laminate composites containing 0.1–0.7 phr clay reinforcements were prepared using a hand layup technique. The fabricated laminates were tested for thermal stability, impact resistance, mechanical properties and flame retardancy. The results indicated an increase in impact resistance, tensile strength, flexural strength and Young’s modulus to an extent and then a decrease as the clay content is increased. Overall results show that a 0.2-phr clay reinforcement into the epoxy–nylon fabric laminate has shown better impact resistance (33.9% more than the neat epoxy–nylon fabric laminate), tensile strength (nearly two times the neat sample), flexural strength (nearly five times the neat sample) and Young’s modulus (39.4% more than the neat sample). Thermal stability is found to decrease slightly upon addition of clay. UL-94 tests conducted on the composite laminate samples have shown a reduction in the burning rate. Also, the tests performed in the present study indicate that the materials under investigation have promising applications in construction, agriculture and decorative purposes.

The Influence Analysis of Groundwater Environment on the Strength of Cement-Stabilized Soil

To measure the applicability of the cement mixing method in the reinforcement of soft clay in Jiaozhou Bay, laboratory test of cement-stabilized soil with different mixture ratio are conducted. We take fly ash as additive and have studied the influences of the cement types, cement content, additive content, soaking time and other factors on the cement-stabilized soil strength under the groundwater soaking condition. This paper demonstrated a link between the above factors and cement-stabilized strength.

Clay Reinforced Hyperbranched Polyurethane Nanocomposites Based on Palm Oil Polyol as Shape Memory Materials

Reactive nanoclay reinforced hyperbranched polyurethane (HPU) nanocomposites have been synthesized with the introduction of palm oil polyol as part of the precursor. The HPU were prepared in a two-step process using polycaprolactonediol, 4,4’-diphenylmethane diisocyanate and 1,4-butanediol as chain extender. Nanoclay was added with the purpose of improving the properties of the pristine polyurethane. The introduction of palm oil polyol is believed to enhance the mixing process between polymer matrix and filler. Thermal, mechanical and shape memory properties of produced HPU were investigated. The results showed that the crystallinity of HPU nanocomposites decreased with introduction of clay particles and that the mechanical and shape memory properties were enhanced with the addition of small amount of reactive nanoclay (up to 3 wt%).

Analysis of nano‐reinforced layered plates via classical and refined two‐dimensional theories

PurposeThe purpose of this paper is to consider the static analysis of nanocomposite plates. Nanocomposites consist of a small amount of nanoscale reinforcements which can have an observable effect on the macroscale properties of the composites.Design/methodology/approachIn the present study the reinforcements considered are non‐spherical, high aspect ratio fillers, in particular nanometer‐thin platelets (clays) and nanometer‐diameter cylinders (carbon nanotubes, CNTs). These plates are considered simply supported with a bi‐sinusoidal pressure applied at the top. These conditions allow the solving of the governing equations in a closed form. Four cases are investigated: a single layered plate with CNT reinforcements in elastomeric or thermoplastic polymers, a single layered plate with CNT reinforcements in a polymeric matrix embedding carbon fibers, a sandwich plate with external skins in aluminium alloy and an internal core in silicon foam filled with CNTs and a single layered plate with clay reinforcements in a polymeric matrix. A short review of the most important results in the literature is given to determine the elastic properties of the suggested nanocomposites which will be used in the proposed static analysis. The static response of the plates is obtained by using classical two‐dimensional models such as classical lamination theory (CLT) and first order shear deformation theory (FSDT), and an advanced mixed model based on the Carrera Unified Formulation (CUF) which makes use of a layer‐wise description for both displacement and transverse stress components.FindingsThe paper has two aims: to demonstrate that the use of classical theories, originally developed for traditional plates, is inappropriate to investigate the static response of nanocomposite plates and to quantify the beneficial effect of the nanoreinforcements in terms of static response (displacements and stresses).Originality/valueIn the literature these effects are usually given only in terms of elastic properties such as Young moduli, shear moduli and Poisson ratios, and not in terms of displacements and stresses.