Improving mechanical properties and biodegradation of polyvinyl alcohol material using poly(D,L-lactic acid-co-glycolic acid)

We have developed novel and environmentally friendly composite materials, consisting of polyvinyl alcohol (PVA) and polymethyl methacrylate (PMMA), for the first time, by dissolving PVA and PMMA in hexafluoroisopropanol (HFIP), followed by subsequent layout of PVA/PMMA/HFIP liquid films and removal of the HFIP. PMMA in the PVA/PMMA materials can remarkedly improve the mechanical properties (tensile strength and elongation at break) and the thermostabilities of the materials. Due to the hybridization of PVA with PMMA, the tensile strength and elongation at break can be improved as much as about 50% and 112%, respectively, compared with neat PVA material, whereas neat PMMA is brittle. Moreover, the materials are biodegradable and biocompatible. At the same time we have conducted systematic investigations to explore the influences of the PVA/PMMA mass ratio on the morphology, crystallinity, chemical structure, thermostability, mechanical properties, biodegradability, biocompatibility and the interactions between PVA and PMMA. The high-performance properties possessed by these materials will further broaden their practical application.

Polyvinyl alcohol /chitosan /nano-hydroxyapatite( PVA /CS /n-HA) hydrogel was prepared via the chem-physical method. Effects of PVA content and the mass fraction of glutaraldehyde( GA) on the performance of the composite material were studied by testing its moisture content,tensile strength,infrared spectroscopy and TG spectrum. The results showed that when the mass ratio of PVA and CS + n-HA is 5∶ 1, and the mass fraction of GA is 2%,the composite hydrogel material has an excellent integrated performance. The moisture content,tensile strength,and elongation breakage are 82. 0%,2. 14 MPa and 343. 26%, respectively. Simultaneous thermal analysis( STA) results show that there is only water evaporation from 25 ℃ to 140 ℃,and the material starts to decompose at 360 ℃,suggesting that the material has a good thermal stability. Infrared analysis results show that there is a cross-linking reaction between CS and GA.

With coke powder as raw materials,coke powder activated carbons(CPAC) were prepared by pretreatment via HNO3 and activated through dipping-calcined activation method by the modifier of KOH.The physical properties of the product were characterized by field emission scanning electron microscopy(SEM),X-ray diffraction(XRD).Nitrogen adsorption was used to characterize the BET surface area,pore structure and pore size distribution,and the influence on electrochemical properties under the different activated temperatures and time was investigated.The composite electrode materials of CPAC/Al-substituted Ni(OH)2 were synthesized through the method of co-precipitation,and the electrochemical performances of CPAC/Al-substituted Ni(OH)2 composite electrode materials were characterized by the constant current charge/discharge testing and cyclic voltammetry testing.The experimental results show that coke powder activated carbon electrode materials has the best electrochemical performance when the activation temperature is 800 ℃ and the activation time is 3 h.Under such conditions,the specific capacitance of the product achieves 211 F/g.CPAC-800 ℃-3 h/Al-substituted Ni(OH)2 composite electrode materials have the trend to increase initially,but start to decrease with the increase of doping amount present of aluminium.The specific capacitance of composite material can reach 1173.6 F/g when the mass ratio of CPAC to nickel is 1∶1 by maintaining the doping quantity of aluminium at 4%(mass fraction).The composite electrode material with the doping quantity of aluminium as 4% and the mass ratio of CPAC to nickel as 1∶1 has the best electrochemical performance after the constant current charge/discharge and cyclic voltammetry tests.

An investigation and comparison of tensile strength in Fiber Sandwiched Wood Composite (FSWC) materials subjected to axial loading

Aluminum-based metal matrix composites are extensively used in applications in many industrial fields, especially in the aviation and automotive industry. The usage rate is increasing day by day. Therefore, it is very important to improve the mechanical properties of the composite structure. For this purpose, in this study, 3, 5, and 7 wt.% tungsten carbide (WC) reinforced aluminum matrix composite material was produced by stir casting method. The mechanical properties (tensile strength, hardness, wear) of the produced composite materials and their effect on machinability were investigated. The machinability process was performed in constant cutting speed, constant cutting depth, three different feed rates (0.05, 0.1, and 0.2 mm·rev−1), and dry environmental conditions. Wear tests were performed on dry sliding conditions, under 25 N load, covering different distances (150, 300, 450, and 600 m). In addition, the microstructure of the composite samples was analyzed using optical microscopy and scanning electron microscope. The phases in the composite material were determined using the X-ray diffraction technique. As a result of the experiments, with the addition of WC particles, the mechanical properties of the materials such as tensile strength, hardness, and wear resistance have increased and the machinability capability has decreased.

In the present work, photocatalytic oxidation of Rhodamine B solutions were performed using a composite material prepared by titanium dioxide films deposited onto cobalt ferrite nanoparticles. Cobalt ferrite nanoparticles were prepared by coprecipitation of Co(II) and Fe(II) ions in basic medium, followed by a controlled oxidation process carried out by nitrate ions in basic medium in inert atmosphere at 95°C. The effect of 2 alcohols (ethanol and 2-propanol) as solvents in the deposition of TiO2 films was studied as a function of CoFe2O4/TiO2 mass ratios. Cobalt ferrite nanoparticles exhibited (36 ± 20) nm diameter with spheroidal shapes as confirmed by SEM studies. TiO2 films deposited onto CoFe2O4 were thicker using ethanol as solvent according to SEM and TEM studies. Cobalt ferrite nanoparticles exhibit a weak oxidation behaviour since around 40% of Rhodamine is eliminated after 90 min of exposition. The 4 composite materials studied oxidize 100% of Rhodamine B after 60 min of reaction and kinetics results fitted a second order degradation reaction equation. As Rhodamine B solution pH was 5.83, faster reactions occur when composite materials develop low surface charge (PZC closer to 5.83) due to small surface charge repulsion. Materials prepared with CoFe2O4/TiO2 ratios between 4 to 6 present higher kinetic constants which is confirmed by a faster Rhodamine B degradation

In recent years, composite materials widely involved replacing the metals to increase the strength at minimal weight. Synthetic fiber reinforced polymer composites are widely used many application like aircraft, automobile etc. Due to increasing demand for the synthetic fiber, because of its light weight and easily biodegradable, Natural fiber are involved in achieving good strength to weight ratio. In present work sisal fiber reinforced polymer composite SFRP was used to replacing the two synthetic composite such as carbon fiber reinforced polymer composite CFRP and glass reinforced polymer composite GFRP. All laminates are fabricated by using hand layup method. The static mechanical properties of epoxy based SFRP, GFRP, CFRP and their hybrids laminates are experimentally evaluated as per ASTM standards and reported. Introduction. Investigated the mechanical properties of sisal, jute and glass fiber reinforced polyester composites observed that the addition of glass fiber into jute fiber composite resulted in maximum tensile strength and that jute and sisal mixture composites sample is capable having maximum flexural strength and maximum impact strength was obtained. [4]. The variation of tensile strength, flexural strength and compressive strength of epoxy based sisal-glass hybrid composites have observed that 2 cm fiber length hybrid composites showed maximum optimal tensile, flexural and compressive strength than 1 and 3 cm. The effect of alkali treated hybrid composites showed higher strength than untreated composites [2]. Increase in NaOH concentration worsens the tensile properties of the natural fiber and also higher concentration enhances the surface characteristics of the fiber by removing the waxy layer from the surface and the fiber matrix interfacial adhesion. So 6% NaOH is the optimum concentration which provides acceptable fiber strength and surface characteristics [8]. The application of composites in structural facilities is mostly concentrated on increasing the strength of the structure with the help of artificial fibers and does not address the issue of sustainability of these raw materials used for strengthening purposes [6].

The authors have developed a new composite steel-concrete material for the strength members of huge offshore structures, where concrete is placed between steel plates. This paper contains the results of both experimental and theoretical investigations into the strength of the new composite material. Experiments under static and repeated loadings were carried out. Four types of test models of the composite material were subjected to shear, bending or combined shear and bending. It was found that the ultimate strength of the composite material is very high and it can absorb a great deal of energy at failure. A method for the ultimate strength analysis of the composite material is developed. The calculated results are in good agreements with experimental ones. Nonlinear analysis is carried out using the finite element method. In the analysis, the material nonlinearities of both concrete and steel are fully taken into account; the propagation of a crack in concrete caused by tension, plastification and crush of concrete by compression, and plastification of steel plate. Geometrical nonlinearity caused by gaps between concrete and steel is, also considered. The analysis accurately represented the behavior of the composite material under tests. The new composite material is found to be desirable for the construction of offshore structures because of their excellent properties; large energy absorption and strength carrying capacity. INTRODUCTION The utilization of concrete and/or composite steel-concrete material for offshore structures gives the advantages of low initial cost, low maintenance cost and good impact resistance. Many projects using concrete are in various stages of design for offshore structures of near future such as an offshore power station. A huge offshore structure, if made of steel, necessitates a great deal of dead load to offset its big bouyancy, whether it is of the floating type or the gravity type. The concrete may be employed as ballast and strength members in such an offshore structure. Drawbacks of concrete associate with low tensile strength and low ductility. It is difficult to secure watertightness, once concrete cracking develops in an offshore structure used in deep water, where the pressure is very high. And this may cause serious troubles. If ordinary composite steel-concrete material, such as reinforced concrete or prestressed concrete, are employed, crack starts on the surface of concrete by bending. Drawbacks of concrete require a design with an excessive margin as the exact estimation of the external forces acting upon an offshore structure is nearly impossible. The authors have developed a new composite steel-concrete material for offshore structures to cover up the various drawbacks of the concrete. The new composite material endures large deformation and absorb a great deal of energy at failure, because the steel plate with high strength and ductility suppresses the development of surface cracks.

Composite materials with polymers and metal oxides materials gives new properties and applications compared to its plane polymers. Synthesis of lithium nickalate dispersed poly(methyl methacrylate) nanocomposite (LiNiO 2 -PMMA) was prepared by simple solvent casting method is reported. Structural characterization of nanocomposite was carried out by X-ray diffraction (XRD) technique. This study reveals the development of crystallinity in amorphous Poly(methyl methacrylate). The scanning electron micrograph (SEM) tool was used to know the morphology of PMMA nanocomposite film. The bonding nature in the composite materials is observed by Infrared (IR) tool.

The disposal of rice husk in landfills and open fields can be problematic and could affect the environment and human health due to its low bulk density. As such, this work concentrates on the usage of rice husk ash for the development and characterization of gypsum plaster and rice husk ash mixture as composite materials. The composite materials were categorized at 10 %, 20 %, 30 %, 40 % and 50 % weight of rice husk ash (RHA) fillers and the gypsum plaster or plaster of Paris (POP) was cast neat at 0 % RHA, which served as the control. Mechanical and thermal properties: tensile strength, compressive strength, flexural strength, Young’s modulus and percentage elongation at fracture of the composites were experimentally determined using the Tokyo universal testing machine. The microstructures of the composites were studied with Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX). It was deduced from the analysis that the developed epoxy-rice husk ash composite will be suitable for engineering and building applications that could be subjected to compression and thermal effects.

Objective To explore mechanical property changes of methyl vinyl silicone rubber modified by ferric nanoparticles and its dispersed phase.Methods Mechanical properties such as Shore A hardness,tensile strength,elongation at break,tearing rate of permanent deformation and tearing strength of pre-prepared ironic nanoparticle enhanced silicone rubber and carbon-coated ferric particle reinforced silicone rubber were tested according to national standards.A thermal field emission scanning electron microscope (TFE-SEM) was used to investigate the morphology of both surface and fracture of the composite materials and to observe the dispersion of ferric nanoparticles in them.Results Mean values of Shore A hardness,tensile strength,elongation at break,tearing permanent deformation rate and tear strength of modified composites increased with the increasing amounts of ferric nanoparticles,however,when the quota of ironic nanoparticles in the composite formula were greater than 17 phr,carbon-coated ferric nanoparticles more than 19 phr,the mean values of tensile strength of two composites stopped increasing and presented the declining trend.When the quota of ferric nanoparticles in the formula exceeding 15 phr,the mean values of elongation at break and tear strength began to decrease in the formula ratio of silicone rubber/ferric nanoparticles up to 85:15,while the Shore A hardness of samples increased all the way.Ferric nanoparticles dispersed evenly on the surface of composites.Nanopowder aggregation in the fracture surface of both composites could be observed at the formula ratio of 85:15 of silicone rubber/iron nanoparticle and 87:13 of silicone rubber/carbon-coated iron specimen.Conclusion Effect of iron nanapareticles and carbon-coated ferric nanoparticles on the mechanical properties of the reinforced methyl vinyl silicone rubber depends on the nanoparticle size,additive amount and agglomeration. Key words: Silicone rubber; Ferric namoparticles; Mechanical property; Thermal field emission scanning electron microscope

This paper presents the results of the comparative study of as cast microstructures and mechanical properties viz yield strength, ultimate tensile strength, elastic modulus, percentage elongation, hardness, percentage porosity and fracture characteristic of 5 wt% SiC and Al2O3 particulate reinforced Al-4% Cu-2.5% Mg matrix composites. These composite materials were prepared through stir casting process. Quantitative metallographic techniques were utilized to determine the average grain size of particles. The microstructures and tensile fracture characteristic of the representative samples of the composites were examined using optical microscope (OM), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD) techniques. The experimental results demonstrate a fairly uniform distribution of 50.8 μm Al2O3 and 49.2 μm SiC spherical particles with some clustering in few areas. At the interfaces of Al2O3 and the matrix, MgO and MgAl2O4 were observed. Similarly, Al4C3 was formed at the interfaces between SiC and the matrix. The mechanical property test results revealed that, for the same weight percentage of reinforcement, Al-4% Cu-2.5% Mg/5 wt% SiC composite exhibit a 15.8%, 16.4%, 4.97% and 10.8% higher yield strength, ultimate tensile strength, elastic modulus, and hardness, respectively. On the other hand, even if some porosity was observed in the Al2O3 reinforced composite, the percentage elongation (ductility) was 31% higher than that of SiC rein-forced composite. The tensile specimen of SiC reinforced composite failed in a brittle fashion without neck formation, whereas the Al2O3 reinforced composite failed in a ductile fashion with noticeable neck formation.

Over the decades, there has been a significant increase in the use of fibres in concrete for improving its properties such as tensile strength and ductility. The fibre concrete is also used in retrofitting existing concrete structures. Among many different types of fibres available today, glass fibre is a recent introduction in the field of concrete technology. Glass fibre has the advantages of having higher tensile strength and fire resistant properties, thus reducing the loss of damage during fire accident of concrete structures. In this investigation glass fibres of 450 mm length are added to the concrete by volume fraction of up to 1% to determine its strength and fire resistant characteristics. Comparison of the strength and fire-resistance performance of conventional concrete and glass fibre concrete was made. The paper presents the details of the experimental investigations and the conclusions drawn there from. Generally, concrete is strong in compression and weak in tension. Concrete is brittle and will crack with the application of increasing tensile force. Once concrete cracks it can no longer carry tensile loads. In order to make concrete capable of carrying tension at strains greater than those at which cracking initiates, it is necessary to increase the tensile strength. To increase the tensile and flexural strength, fibres are added in concrete. The addition of fibres to concrete will result in a composite material that has properties different from those of un-reinforced concrete. The extent of this variation depends not only on the type of fibres, but also on the fibre dosage. The incorporation of fibres into a brittle concrete can have the effect of controlling the growth and propagation of micro cracks as the tensile strain in the concrete increases. Care is needed in using fibre as additive in concrete. The use of fibres in concrete has increased with the development of fast-track construction. In fact, nearly 65 per cent of the fibres produced worldwide is currently used in concrete. It offers increasing toughness and ductility, tighter crack control and improved load-carrying capacity. Different types of fibres are available in the market for reinforcing concrete and they are: steel, glass, acrylic, aramid, carbon, nylon, polyester, polyethylene, polypropylene, etc. Besides, natural fibres like sisal, wood cellulose, banana, jute, etc., have also been used. From the above mentioned fibres, glass fibre is more advantageous on the basis of strength and fire resistant characteristics. It has been recognized that adding small, closely spaced and uniformly dispersed fibres to concrete serves to arrest cracks and improve its properties under static and dynamic loading. Round steel fibre is the most common variety in use for improving the tensile, flexural, impact and fatigue strength of concrete. The ductility and toughness of concrete are also improved with the addition of this fibres. Steel fibre have been used in various types of structures such as earthquake resistant structures, road overlays, airfield pavements and bridge decks. Alkali resistant glass fibre reinforcement is a relatively new addition to the family of fibres that impart high tensile strength, high stiffness, high chemical resistance and considerable durability to FRC (Fibre Reinforced Concrete). Adding polyesters fibre to concrete pavements resulted in the developments of the micro shrinkage cracks induced during hydration. These fibres improve the flexural strength and energy absorption of concrete . Glass fibres are useful because of their high ratio of surface area to weight. However, the increased surface area makes them much more susceptible to chemical attack. By trapping air within them, blocks of glass fibre makes good thermal insulation, with a thermal conductivity of order of 0.05 w/(mk). The strength of the glass fibre is usually tested and reported for virgin or pristine fibres those which have just been manufactured. The freshest and thinnest fibers are more ductile. The more the surface is scratched, the less the resulting tenacity. Because glass has an amorphous structure, its properties are the same along the fiber and across the fiber. Humidity is an important factor in the tensile strength. Moisture is easily absorbed, and can worsen microscopic cracks and surface defects, and lessen tenacity. Glass fibres improve the strength of the material by increasing the force required for deformation and improve the toughness by increasing the energy required for

Technology has been developed to prepare a biodegradable and environmental friendly composite material from tamarind seed gum and banana fibre. Tamarind seed gum is prepared from the endosperm of roasted seeds of the tamarind tree. The different temperature condition maintained for roasting the seeds are 130, 160, and 180°C. Banana fibres are extracted from different varieties of banana trees, which are used for the preparation of composite material. The tensile strength of the composite material is measured and shows dependency on the variety of banana fibre used in the preparation and also the roasting temperature condition of the tamarind seed. Tamarind seed gum (the seed roasted at the temperature condition of 130°C) and Red banana fibre composite shows the highest tensile strength of 3.97 MPa and Poovan fibre composites shows the lowest tensile strength of 1.90 MPa. The composite material of other varieties shows tensile strength in between these two values. The percentage of moisture absorption of the composite material has a direct correlation to the tensile strength. In addition, investigation on fire retardant test of tamarind seed gum — banana fibre composite material revealed that untreated and varnish coated banana fibre composite material has good fire retardant characteristics. This is an important feature to promote the use of this composite material as a false roofing material instead of thermocole.

The rapid development of Aluminium composites with advanced hybrid materials is increasing due to increasing demand. This composite material is used in many applications in the aerospace and automotive industries due to its lightweight, good corrosion resistance and high thermal resistance. To meet this demand, this study focused on the development of Al-7075 alloy reinforcements containing TiB2 and graphene, using Aluminium-7075 as the base material, mixed with TiB2 and graphene to measure and improve mechanical and tribological properties by using stir casting technique, with the proposed graphene content of 1%, 2% and 3% and TiB2 content varying between 1 to 15% of its overall weight. With the addition of TiB2 and graphene properties such as hardness, tensile strength, impact strength and tribological behaviour are improved. The 12% reinforcement combination (i.e. 10% TiB2 and 2% Gr) exhibit better tensile strength, hardness and wear resistance. Microstructure and phase characterization of the composite material are analyzed using scanning electron microscopy (SEM) and x-ray diffraction (XRD) techniques. A microstructure evaluation is employed to justify the homogenous dispersal and the existence of reinforced particles. To ensure the quality and reliability of products made from these alloys, destructive tests are often conducted to evaluate their mechanical properties and behavior under different loading conditions.