Today concrete is most generally utilized development material in the world due to its strength and sturdiness properties. To attain good strength, curing of concrete is important so we introduce the concept of self-curing concrete rather than immersion or sprinkle curing to avoid water scarcity. It was observed that water solvent polymers can be utilized as a self-curing agent, i. e. polyethylene glycol (PEG-400). In the present study, to discover the effect of admixture polyethylene glycol (PEG-400) on compression strength, split tensile strength and flexural strength, adding the diverse rate of PEG-400 to the weight of cement from zero to two percentages as the measurement of the curing agent is done. The test results were studied for M30 concrete mix. The optimum percentage of PEG-400 was found to be 1% for compressive and Split Tensile Strength. If the dosage of PEG-400 increases to more than 1%, there is a decline in compressive and split tensile strength. However, the optimum percentage of PEG-400 for flexural strength was found at 0. 5%. If we increase the dosage of PEG-400 more than 0. 5%, there is reduction in strength of flexural strength.

Current research work focuses on the synthesis of phosphorus-and silicon-containing amine curing agent (PSA) for epoxy resins. PSA was synthesized using phenyl phosphonic dichloride and ethylenediamine as raw materials and further modification with 3-glycidoxypropyltrimethoxysilane. NMR, FTIR and amine value analysis were performed for the structure confirmation of the obtained product and intermediate. PSA was taken in different molar ratios for the crosslinking with epoxy resin before which the sol–, gel technique was performed onto the product for self-crosslinking of the methoxy groups. The obtained formulations were applied onto the mild steel panels and cured in an oven. The thermal and mechanical properties of cured epoxy resins were analyzed by TGA, DSC, impact resistance, pencil hardness and flexibility. The thermal and mechanical properties were increased along with the heat resistance index temperature (THRI) toward the loading of PSA into the coating formulations. The flame retardant properties were also checked and found to be increased with respect to the increasing concentration of PSA because of the synergistic effect of P and Si atoms. The formulation with the highest amount of PSA showed the highest LOI as 29 with self-extinguishing behavior in the UL-94 test.

Concrete in today’s world has a major role in construction industry and is the most frequently used material in construction having high compressive strength and durability. Concrete needs proper curing to achieve desirable properties and insufficient curing affects the strength of concrete badly. Nowadays, Internal Curing (IC) has come into research which has many positive advantages in terms of enhancement of properties of concrete. By utilizing the water that is already in the concrete and adding certain amounts of self-curing agents, this method of curing is used that helps in the curing of the concrete internally. It is done ‘from the inside to outside’ using internal reservoirs. Also, shrinkage reducing agents like Polyethylene-glycol and Light-Weight Aggregates (LWA) are used to achieve effective curing results. In cement-based materials, Superabsorbent Polymer (SAP) is generating a lot of debate. This study offers a review for cement-based materials containing SAP for different w/c values, the conclusions on the properties including workability, mechanical characteristics, and durability of SAP-modified concrete and SAP cement-based materials. In most of the studies found on high-performance concrete, w/c is restricted to 0.3 - 0.35. Hence, properties are described on the basis of different w/c ratios as mentioned in this paper. Total 60 articles are reviewed (including 59 research paper and 1 review report) in this study.

Glass/epoxy prepregs are widely used in composite industry. Although they have significant advantages, the brittleness nature of its epoxy matrix produces some difficulties. In this paper, the toughened epoxy resin was used in the preparation of prepregs. the effect of liquid carboxyl-terminated butadiene-acrylonitrile rubber (CTBN) and a flexible diamine (Jeffamine D-400) curing agent on epoxy prepregs based on diglycidyl ether of bisphenol-A (DGEBA) resin and dicyandiamide (Dicy) reinforced with glass fiber were studied. For this purpose, after preparing the resin formulation and its impregnation with glass fiber or preparing the prepreg samples, the effect of CTBN and Jeffamine on epoxy/glass prepregs properties like resin flow, lap shear strength (LSS) and interlaminar shear strength (ILSS) were studied. Volatile content, resin content and pre-curing of prepared prepregs are characterized. Results show that in all samples the amount of resin content, volatile content and pre-curing were nearly the same and adding different amounts of CTBN or Jeffamine do not changed the resin flow. By adding 20 phr of liquid rubber, LSS does not changed but, adding the Jeffamine up to 20% increased the LSS by 8% and adding Jeffamine up to 40% does not changed this property. By adding the CTBN by 5 phr, the ILSS increased by 7. 7% and in all Jeffamine samples the ILSS varied from 4. 6 MPa for 100% Dicy to 2. 0 MPa for sample containing 60% of Jeffamine and 2. 6 MPa for 100% of Jeffamine content.

Phosphate ester compounds display good flame retardancy effect in epoxy resin systems. In this paper, several novel phosphate esters, used as curing agents for epoxy resins, were synthesized based on P2O5, phosphoric acid, and different types of alcohol. The structures of phosphate esters were characterized by 31P nuclear magnetic resonance (31P NMR). Then, a series of flame retardant epoxy composites were prepared by curing the epoxy resins (E-44) with the phosphate esters. The flame retardancy and thermal degradation behaviors of flame retardant epoxy composites were investigated by cone calorimeter test (CCT) and thermogravimetric analysis (TGA), respectively. The results of CCT indicated that phosphate esters can significantly decrease heat release rate, total heat release (THR), and smoke production rate. The sample cured by butyl phosphate ester from phosphorus pentoxide, phosphoric acid and butanol showed the best flame retardant performance among all samples. The TGA results showed that phosphate esters could enhance char residues of flame retardant epoxy composites when compared with those of a composite using T31 as a curing agent at high temperature. It may be concluded that good flame retardant properties of flame retardant epoxy composites are related to the formation of a protective phosphorus-rich char layer. These phosphate esters have a good future on flame retardant epoxy composites.

Research Subject: Regarding new researches on chemorheology of highly-filled composites, it is determined that HTPB slurry should have convenient viscosity for ease of casting. In the other words, available time for appropriate casting of highly-filled composite after curing agent addition called pot-life. Long pot-life of HTPB binder system is necessary for good processability and non-defect production of highly-filled composite grains. In addition to long pot-life, the physicalmechanical properties of HTPB-based highly-filled composite are also important. Research Approach: In this research, effect of curing agent type (molecular structure), casting temperature and the amount of DBTDL as a curing catalyst on chemorheological behavior of HTPB binder system and physical-mechanical properties of highly-filled composite were investigated. Toluene diisocyanate (TDI), isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI) were selected in order to investigate the role of molecular structure of curing agent on chemorheology of binder system and its slurry and also on physical-mechanical properties of highly-filled composite. Moreover, temperatures of 50, 40, and 60 ˚ C, were selected to study the effect of casting temperature on chemorheology. Main Results: By every 10 ˚ C decreasing of casting temperature, potlife of binder system (based on IPDI and TDI) was increased about 10 min. Pot-life of binder system and highly-filled composite slurry based on IPDI in the presence of %0. 005 DBTDL (the optimum content) showed the longest pot-life at similar temperatures. The elastomer and highly-filled composite based on IPDI showed the highest crosslinking density (CLD) and modulus in comparison to other curing agents, retaining tensile strength and adequate elongation.

Introduction: Shear bond strength is one of the most important mechanical characteristics involved in clinical durability of tooth-colored restorations, which is directly related to polymerization shrinkage. This study evaluated the efficacy of two light-curing units (LED2 & QTH) and two types of dentin bonding agents (Excite & Clearfil SE bond) on composite resin shear bond strength to dentin.Materials and Methods: Forty caries-free sound human premolars were randomly divided into 4 groups of 10 after being disinfected with sodium hypochlorite. The occlusal surface of dentin in each specimen was exposed and flattened by a fissure bur, composite resin was bonded with Excite or Clearfil SE bonding agents and polymerized with QTH or LED2. Shear bond strength values of the specimens were tested in a Dartec universal testing machine. Data were analyzed by one-way ANOVA, two-way ANOVA and Dunkan test (a=0.05).Results: Maximum shear bond strength values were recorded in composite restorations bonded with Clearfil SE bonding agent and polymerized by LED2, minimum values were recorded in composites restorations bonded with Excite and polymerized by QTH. Statistical analysis showed statistically significant differences between the experimental groups (p value=0.03).Conclusion: Under the limitations of this study, it can be concluded that two curing systems of LED2 & QTH are equally effective on shear bond strength of different bonding agents, whereas Clearfil SE bonding agent produces higher shear bond strength than Excite total-etch regardless of the type of light-curing unit.

A detailed study on the curing of Bisphenol A-based liquid epoxy resin such as Lapox B-13 (Viscosity 12000-16000 mpos) and Lapox B-11 (Viscosity 9000-12000mpos) with various amines like EDA (Ethylenediamine),DETA (Diethylenetriamine), TETA (Triethylenetetramine), AEP (Aminoethylpiperazine) and IPDA (Isophoronediamine) as curing agents have been carried out. The curing rates and the exotherm have been determined. The effect of various accelerators or modifiers on the curing rate is also worked out using salicylic acid, phenol and nonylphenol. The results obtained reveal that the curing rates are faster in the case of tertiary amines compared to secondary and primary amines. The high exotherm and the least curing time in the case of AEP can be attributed to the tertiary nitrogen group present and which can act as a catalyst for the curing process. It is also observed that a cyclic amine like Isophoronediamine which has only primary amine group takes a longer time for curing with a low isotherm. The data obtained with accelerators on the curing studies clearly indicate that they enhance the curing rate and the exotherm in all the cases. In majority of the cases the cured samples obtained were hard and polymeric transparent materials. The effect of mass of the sample on the curing rate and isotherm has also been observed. All the cured samples show good resistance to moisture absorption and show high chemical resistance.    

Organic-inorganic hybrid coatings prepared by sol-gel process due to having organic-inorganic networks in their structure have a set of mechanical and chemical properties and as a result they attract a lot of interest. These coatings were prepared by a two-step process: hydrolysis and condensation reaction of silane compounds, that is, 3-glycidoxy propyl trimethoxy silane (GPTMS) and tetramethoxysilane (TMOS) in the presence of acid catalyst and as a bisphenol A (BPA) and an aromatic diol. Surface investigation of films and the bonds between the epoxy functional group of silane compound and the curing agent and also cross-linking between them and the curing agent and oxide layer were carried out by optical microscopy images and ATR-IR spectroscopy. Corrosion resistance of these coatings was studied by electrochemical and accelerated corrosion (salt spray) experiments. Both optical microscopy and ATR-IR spectroscopy observations revealed that the surface of these coatings have not any crack and reduction of absorption peaks in the region of 750 and 906cm-1 and the presence of a peak at 936cm-1 were attributed to cross-linking between BPA and epoxy function of silane compound and oxide layer of metal support surface, respectively. Electrochemical and accelerated corrosion experiment results showed that these compounds have good corrosion resistance. Study of the effect of H2O and silane content on the degree of corrosion resistance by electrochemical experiments indicated that the completion of hydrolysis reaction and reduction of silane content (%TMOS) make improvement on corrosion resistance of organic-inorganic hybrid coatings.