Iranian Journal of Polymer Science and Technology 10163255 28 2 2015 06 22 Studying the Properties of Polyvinyl Alcohol/Cellulose Nanofiber/Hydroxyapatite Hybrid Nanocomposite Studying the Properties of Polyvinyl Alcohol/Cellulose Nanofiber/Hydroxyapatite Hybrid Nanocomposite 99 91 1236 10.22063/jipst.2015.1236 FA Mostafa Yahyavi Department of Wood and Paper Engineering, Gorgan University of Agricultural Sciences and Natural Resources, P.O. Box: 49189-43464, Gorgan, Iran Aboulghasem Khazaeian Department of Wood and Paper Engineering, Gorgan University of Agricultural Sciences and Natural Resources, P.O. Box: 49189-43464, Gorgan, Iran Mahdi Mashkour Department of Wood and Paper Engineering, Gorgan University of Agricultural Sciences and Natural Resources, P.O. Box: 49189-43464, Gorgan, Iran Journal Article 2014 01 23 Nanocomposite materials have recently attracted much attention because of their desirable and unique physical and mechanical properties. Today, many studies have focused on the preparation of high performance new nanocomposites made of biobased and biodegradable materials as both the matrix and reinforcement phases. Because of biocompatibility, biofunctionality, and biological safety in the body, hydroxyapatite-polyvinyl alcohol composites are vastly used in medical applications, specially in the bone tissue regeneration. The properties of a new generation of nanocomposites consisting of hydroxyapatite nanoparticles and cellulose nanofibers, dispersed in polyvinyl alcohol matrix, were investigated. The percentage by weight of each component in the final formulation and the time of ultrasonication were studied as factors affecting the physical and mechanical properties. Tensile strength, elastic modulus and resistance to water dissolution were evaluated. The results showed that by increasing the percentage by weight of PVA and cellulose nanofibers and ultrasonication time, the tensile strength and elastic modulus increased and the resistance to water dissolution and weight loss decreased. On the other hand, with increasing the amount of hydroxyapatite nanoparticles in the final formulation, the elastic modulus and resistance to water solubility increased, while the tensile strength decreased significantly. Scanning electron microscopy (SEM) micrographs were used to find exact correlations between the observed physical and mechanical properties and the structural morphology. Nanocomposite materials have recently attracted much attention because of their desirable and unique physical and mechanical properties. Today, many studies have focused on the preparation of high performance new nanocomposites made of biobased and biodegradable materials as both the matrix and reinforcement phases. Because of biocompatibility, biofunctionality, and biological safety in the body, hydroxyapatite-polyvinyl alcohol composites are vastly used in medical applications, specially in the bone tissue regeneration. The properties of a new generation of nanocomposites consisting of hydroxyapatite nanoparticles and cellulose nanofibers, dispersed in polyvinyl alcohol matrix, were investigated. The percentage by weight of each component in the final formulation and the time of ultrasonication were studied as factors affecting the physical and mechanical properties. Tensile strength, elastic modulus and resistance to water dissolution were evaluated. The results showed that by increasing the percentage by weight of PVA and cellulose nanofibers and ultrasonication time, the tensile strength and elastic modulus increased and the resistance to water dissolution and weight loss decreased. On the other hand, with increasing the amount of hydroxyapatite nanoparticles in the final formulation, the elastic modulus and resistance to water solubility increased, while the tensile strength decreased significantly. Scanning electron microscopy (SEM) micrographs were used to find exact correlations between the observed physical and mechanical properties and the structural morphology. http://jips.ippi.ac.ir/article_1236_b8df854f25207881ab687eeda76feb1b.pdf

Iranian Journal of Polymer Science and Technology 10163255 28 2 2015 06 22 Preparation of Porous Thermoset Polyurethane with Supercritical CO2 as Non-solvent Preparation of Porous Thermoset Polyurethane with Supercritical CO2 as Non-solvent 109 101 1237 10.22063/jipst.2015.1237 FA Mohsen Izadi Polymer Engineering Group, Faculty of Engineering, Tarbiat Modares University, P.O. Box: 14115-143, Tehran, Iran Mohammad Hossein Navid Famili Polymer Engineering Group, Faculty of Engineering, Tarbiat Modares University, P.O. Box: 14115-143, Tehran, Iran Zahra Maghsoud Department of Chemical Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, Postal Code: 9177948974, Mashhad, Iran 0000-0003-0583-0137 Journal Article 2014 06 15 Most of porous polymer materials are mainly prepared by solution phase inversion method. The de-mixing process can be initiated by diffusive solvent/non-solvent exchange of binary, ternary or multicomponent mixture. Recently, supercritical CO2 (ScCO2) is used as a non-solvent to prepare porous polymers. ScCO2 possesses excellent properties, such as environmental friendliness, liquid-like density and gas-like diffusivity in comparison with conventional liquid non-solvents. Porous polyurethane was prepared from polymer/N-dimethylformamide (DMF) solution using a supercritical fluid-phase inversion process in which carbon dioxide acted as the non-solvent. The effects of time delay, casting temperature and ratio of polyol/chain extender (POL/CE) on the membrane morphology and structure (size and distribution of cells and pores, thickness of dense layer and porosity) were studied. According to the results, a minimum time delay of 120 min was determined for formation of a suitable structure. The dense layer of 77.6 μm thickness was decreased to 43.1 μm by lowering casting temperature from 55°C to 35°C. The ratio of POL/CE influenced the thermodynamic and kinetic properties. A decrease in POL/CE ratio led to formation of smaller and uniform cells and increased porosity. On decreasing the ratio of POL/CE from 2 to 0.25, the mean diameter of the cells at 6.3 μm dropped to 3 μm. Most of porous polymer materials are mainly prepared by solution phase inversion method. The de-mixing process can be initiated by diffusive solvent/non-solvent exchange of binary, ternary or multicomponent mixture. Recently, supercritical CO2 (ScCO2) is used as a non-solvent to prepare porous polymers. ScCO2 possesses excellent properties, such as environmental friendliness, liquid-like density and gas-like diffusivity in comparison with conventional liquid non-solvents. Porous polyurethane was prepared from polymer/N-dimethylformamide (DMF) solution using a supercritical fluid-phase inversion process in which carbon dioxide acted as the non-solvent. The effects of time delay, casting temperature and ratio of polyol/chain extender (POL/CE) on the membrane morphology and structure (size and distribution of cells and pores, thickness of dense layer and porosity) were studied. According to the results, a minimum time delay of 120 min was determined for formation of a suitable structure. The dense layer of 77.6 μm thickness was decreased to 43.1 μm by lowering casting temperature from 55°C to 35°C. The ratio of POL/CE influenced the thermodynamic and kinetic properties. A decrease in POL/CE ratio led to formation of smaller and uniform cells and increased porosity. On decreasing the ratio of POL/CE from 2 to 0.25, the mean diameter of the cells at 6.3 μm dropped to 3 μm. http://jips.ippi.ac.ir/article_1237_c5ccc6e5f59cb045fbc2d3c479bab0ce.pdf

Iranian Journal of Polymer Science and Technology 10163255 28 2 2015 06 22 Preparation and Characterization of a Polymer Concrete and Estimation of Compressive Strength Using a Two-Phase Micromechanical Model Preparation and Characterization of a Polymer Concrete and Estimation of Compressive Strength Using a Two-Phase Micromechanical Model 120 111 1238 10.22063/jipst.2015.1238 FA Mahmood Mehrdad Shokrieh Composites Research Laboratory, Center of Excellence in Experimental Solid Mechanics and Dynamics, School of Mechanical Engineering, Iran University of Science and Technology, P.O. Box: 16846-13114 Tehran, Iran Sina Rezvani Composites Research Laboratory, Center of Excellence in Experimental Solid Mechanics and Dynamics, School of Mechanical Engineering, Iran University of Science and Technology, P.O. Box: 16846-13114 Tehran, Iran Reza Mosalmani Composites Research Laboratory, Center of Excellence in Experimental Solid Mechanics and Dynamics, School of Mechanical Engineering, Iran University of Science and Technology, P.O. Box: 16846-13114 Tehran, Iran Journal Article 2014 06 24 In comparison with conventional concrete, the polymer concrete has considerably better mechanical properties. Meanwhile, polymer concrete is more expensive than traditional cement concretes. Considering the good mechanical properties of polymer concrete, its applications can be developed by reducing manufacturing costs. In this study, in order to improve the mechanical properties and reduce the manufacturing costs of polymer concrete, a new formulation is presented. In this formulation, the more common mixture of large and small aggregates was replaced by silica sand. In addition, in order to reduce the manufacturing costs, polyester resin was used instead of epoxy resin as the base material. The compressive and three-point bending tests showed that the polyester-based concrete had a higher compressive strength (20%) in comparison with the epoxy-based concrete, while their bending strength was approximately the same. As a result, the manufacturing cost for the polymer concrete prepared using this new formulation can be reduced without decrements in mechanical properties. Moreover, a two-phase micromechanical model was applied to estimate the compressive strength of the polymer concrete. Using the two-phase micromechanical model, the mechanical properties of the polymer concrete were predicted. The results obtained from the modeling and experiments were in good agreement with each other (6.8% error). The excellent mechanical properties of polyester-based concrete developed in the present research and its low cost in comparison with the epoxy-based concrete are key factors that can help its wider applications. In comparison with conventional concrete, the polymer concrete has considerably better mechanical properties. Meanwhile, polymer concrete is more expensive than traditional cement concretes. Considering the good mechanical properties of polymer concrete, its applications can be developed by reducing manufacturing costs. In this study, in order to improve the mechanical properties and reduce the manufacturing costs of polymer concrete, a new formulation is presented. In this formulation, the more common mixture of large and small aggregates was replaced by silica sand. In addition, in order to reduce the manufacturing costs, polyester resin was used instead of epoxy resin as the base material. The compressive and three-point bending tests showed that the polyester-based concrete had a higher compressive strength (20%) in comparison with the epoxy-based concrete, while their bending strength was approximately the same. As a result, the manufacturing cost for the polymer concrete prepared using this new formulation can be reduced without decrements in mechanical properties. Moreover, a two-phase micromechanical model was applied to estimate the compressive strength of the polymer concrete. Using the two-phase micromechanical model, the mechanical properties of the polymer concrete were predicted. The results obtained from the modeling and experiments were in good agreement with each other (6.8% error). The excellent mechanical properties of polyester-based concrete developed in the present research and its low cost in comparison with the epoxy-based concrete are key factors that can help its wider applications. http://jips.ippi.ac.ir/article_1238_98f7d92b46c8f5e2385c5e4766c43b7d.pdf

Iranian Journal of Polymer Science and Technology 10163255 28 2 2015 06 22 Characterization of Chemically Synthesized Polyaniline-Polyvinylchloride-Montmorillonite Nanocomposite Characterization of Chemically Synthesized Polyaniline-Polyvinylchloride-Montmorillonite Nanocomposite 130 121 1239 10.22063/jipst.2015.1239 FA Arefeh Tabatabaei Department of Chemistry, East Azarbayjan Science and Research Branch, Islamic Azad University, P.O. Box: 5157944533, Tabriz, Iran Maryam Farbodi Department of Chemistry, Tabriz Branch, Islamic Azad University, P.O. Box: 5157944533, Tabriz, Iran Journal Article 2014 07 01 Polyaniline-montmorillonite (PANI-MMT) nanocomposite was synthesized by chemical polymerization of aniline in the presence of montmorillonite (MMT) nanostructures. The triple hybrid of polyaniline-polyvinylchloridemontmorillonite (PANI-PVC-MMT) was prepared by mixing of the synthesized PANIMMT nanocomposite with a solution of polyvinylchloride (PVC) in tetrahydrofurane (THF). In addition, PANI-PVC composite was prepared by mixing of pure synthesized PANI and PVC solution in THF. To investigate the mechanical properties, the PANIPVC composite and PANI- PVC-MMT nanocomposite films were prepared with 5, 10 and 15 wt% of pure PANI and PANI-MMT  nanocomposite, respectively. The results showed that the PANI- PVC-MMT nanocomposite film having 10 wt% of PANIMMT nanocomposite displayed the best mechanical properties. Therefore, it was chosen as optimum film and its physico-chemical properties were characterized. The cyclic voltammetry (CV) technique confirmed that the triple hybrid of PANI-PVCMMT nanocomposite was electroactive. Also, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) techniques were used to characterize the composition and structure of the PANI-PVC-MMT triple hybrid nanocomposite. X- Ray diffraction (XRD) technique showed an intercalated structure for the PANI-PVC-MMT nanocomposite. The thermal stability improvement of the PANI-PVC-MMT nanocomposite in comparison with the pure PVC was established by thermogravimetric analysis (TGA). Polyaniline-montmorillonite (PANI-MMT) nanocomposite was synthesized by chemical polymerization of aniline in the presence of montmorillonite (MMT) nanostructures. The triple hybrid of polyaniline-polyvinylchloridemontmorillonite (PANI-PVC-MMT) was prepared by mixing of the synthesized PANIMMT nanocomposite with a solution of polyvinylchloride (PVC) in tetrahydrofurane (THF). In addition, PANI-PVC composite was prepared by mixing of pure synthesized PANI and PVC solution in THF. To investigate the mechanical properties, the PANIPVC composite and PANI- PVC-MMT nanocomposite films were prepared with 5, 10 and 15 wt% of pure PANI and PANI-MMT  nanocomposite, respectively. The results showed that the PANI- PVC-MMT nanocomposite film having 10 wt% of PANIMMT nanocomposite displayed the best mechanical properties. Therefore, it was chosen as optimum film and its physico-chemical properties were characterized. The cyclic voltammetry (CV) technique confirmed that the triple hybrid of PANI-PVCMMT nanocomposite was electroactive. Also, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) techniques were used to characterize the composition and structure of the PANI-PVC-MMT triple hybrid nanocomposite. X- Ray diffraction (XRD) technique showed an intercalated structure for the PANI-PVC-MMT nanocomposite. The thermal stability improvement of the PANI-PVC-MMT nanocomposite in comparison with the pure PVC was established by thermogravimetric analysis (TGA). http://jips.ippi.ac.ir/article_1239_ac70b8e73ced837e0498cd6cb16ab32a.pdf

Iranian Journal of Polymer Science and Technology 10163255 28 2 2015 06 22 Effect of Amine-Functionalized MIL-53 Metal Organic Frameworks on the Performance of Poly(4-methyl-1-pentyne) Membrane in CO2/CH4 Separation Gas Mixture Effect of Amine-Functionalized MIL-53 Metal Organic Frameworks on the Performance of Poly(4-methyl-1-pentyne) Membrane in CO2/CH4 Separation Gas Mixture 147 131 1240 10.22063/jipst.2015.1240 FA Reza Abedini Faculty of Chemical Engineering, Babol University of Technology, P.O. Box: 484, Babol, Iran Mohammadreza Omidkhah Faculty of Chemical Engineering, Tarbiat Modares University, P.O. Box: 14115-143, Tehran, Iran Fatereh Dorosti Faculty of Chemical Engineering, Tarbiat Modares University, P.O. Box: 14115-143, Tehran, Iran Journal Article 2014 07 07 The effect of NH2-MIL 53 metal organic framework (MOF) on gas transport properties of poly(4-methyl-1-pentyne) (PMP) was investigated. Various characterization methods such as FTIR, DSC, SEM and gas adsorption test as well as a series of CO2/CH4 gas separation tests (i.e., pure and mixed gas test) were conducted in order to determine the effect of ligand functionalization (–NH2) on the properties of the prepared mixed matrix membranes and their gas transport characteristics. The results of DSC showed that glass transition temperature (Tg) increased by increasing NH2-MIL 53 loading. The SEM images also demonstrated that the NH2-MIL 53 particles were dispersed well in the PMP matrix with no noticeable agglomeration. The gas adsorption test of NH2-MIL 53 particles revealed there was a selective adsorption behavior with respect to CO₂. It was also found that, incorporation of NH2-MIL 53 into the PMP resulted in an increase in gas permeability (especially towards CO₂) and a higher CO₂/CH₄ selectivity. Adding 30 wt% NH2-MIL 53 into the polymer matrix increased CO₂ permeability and CO₂/CH₄ selectivity of the mixed gas from 83.35 to 210.21 barrer and 7.61 to 19.88, respectively. Rising the temperature from 30 to 60°C led to the permeability increment of both CO₂ and CH₄ in the mixed gas test, while the CO₂/CH₄ selectivity decreased. Moreover, the results showed that amino groups required no regeneration and their performance did not decline during 120 h of permeation test. A comparison between the permeation data and those calculated from permeation models revealed that the Bruggeman model could fit the CO₂ permeability data better than the Maxwell and Lewis models. The effect of NH2-MIL 53 metal organic framework (MOF) on gas transport properties of poly(4-methyl-1-pentyne) (PMP) was investigated. Various characterization methods such as FTIR, DSC, SEM and gas adsorption test as well as a series of CO2/CH4 gas separation tests (i.e., pure and mixed gas test) were conducted in order to determine the effect of ligand functionalization (–NH2) on the properties of the prepared mixed matrix membranes and their gas transport characteristics. The results of DSC showed that glass transition temperature (Tg) increased by increasing NH2-MIL 53 loading. The SEM images also demonstrated that the NH2-MIL 53 particles were dispersed well in the PMP matrix with no noticeable agglomeration. The gas adsorption test of NH2-MIL 53 particles revealed there was a selective adsorption behavior with respect to CO₂. It was also found that, incorporation of NH2-MIL 53 into the PMP resulted in an increase in gas permeability (especially towards CO₂) and a higher CO₂/CH₄ selectivity. Adding 30 wt% NH2-MIL 53 into the polymer matrix increased CO₂ permeability and CO₂/CH₄ selectivity of the mixed gas from 83.35 to 210.21 barrer and 7.61 to 19.88, respectively. Rising the temperature from 30 to 60°C led to the permeability increment of both CO₂ and CH₄ in the mixed gas test, while the CO₂/CH₄ selectivity decreased. Moreover, the results showed that amino groups required no regeneration and their performance did not decline during 120 h of permeation test. A comparison between the permeation data and those calculated from permeation models revealed that the Bruggeman model could fit the CO₂ permeability data better than the Maxwell and Lewis models. http://jips.ippi.ac.ir/article_1240_3b6d873fdbb8bc7914d669f62647eade.pdf

Iranian Journal of Polymer Science and Technology 10163255 28 2 2015 06 22 Preparation and Characterization of HDPE/EVA Flat Sheet Membranes by Thermally Induced Phase Separation Method Preparation and Characterization of HDPE/EVA Flat Sheet Membranes by Thermally Induced Phase Separation Method 159 149 1241 10.22063/jipst.2015.1241 FA Zahra Shoeyb Faculty of Chemical Engineering, Sahand University of Technology, P.O. Box: 51335-1996, Tabriz, Iran Reza Yegani Faculty of Chemical Engineering, Sahand University of Technology, P.O. Box: 51335-1996, Tabriz, Iran Elham Shokri Faculty of Chemical Engineering, Sahand University of Technology, P.O. Box: 51335-1996, Tabriz, Iran Journal Article 2014 07 23 The adjustment of material composition in fabrication of modified polymeric membrane has been considered the most efficient and easiest method. For this purpose blended membranes of high density polyethylene (HDPE)–ethylene vinyl acetate (EVA) were prepared by thermally induced phase separation method. The impact of EVA in the presence of diluent on the crystalization temperature was assessed using differential scanning calorimetry (DSC). The obtained results showed that EVA has no significant effect on the crystalization temperature of HDPE. The absorption frequencies at 1248 and 1749 cm^-1, respectively, due to C-O and C=O streching vibrations of EVA functional groups, confirmed the existence of EVA in HDPE membrane. The pure water permeability of HDPE/EVA blend was measured and compared with that of neat HDPE membrane. The results showed that an EVA content up to 2.5 wt% raised water permeability considerably and the leafy structure of the membranes contracted and the pure water permeation dropped with higher EVA content. The results of porosity measurement and scanning electronic microscopic (SEM) analysis also confirmed these findings. Contact angel measurements and atomic force microscopy (AFM) examinations and static absorption of collagen protein on the membrane surfaces revealed that EVA content up to 5 wt% lowered the hydrophobicity of the membrane. By EVA content above 10 wt%, due to the structural alteration on the membrane surface, the contact angel and the collagen absorption on the surface of membrane increased. The measurement of tensile strength showed that with increasing EVA content the mechanical properties of the membranes improved due to interactions of polar groups in EVA. The adjustment of material composition in fabrication of modified polymeric membrane has been considered the most efficient and easiest method. For this purpose blended membranes of high density polyethylene (HDPE)–ethylene vinyl acetate (EVA) were prepared by thermally induced phase separation method. The impact of EVA in the presence of diluent on the crystalization temperature was assessed using differential scanning calorimetry (DSC). The obtained results showed that EVA has no significant effect on the crystalization temperature of HDPE. The absorption frequencies at 1248 and 1749 cm^-1, respectively, due to C-O and C=O streching vibrations of EVA functional groups, confirmed the existence of EVA in HDPE membrane. The pure water permeability of HDPE/EVA blend was measured and compared with that of neat HDPE membrane. The results showed that an EVA content up to 2.5 wt% raised water permeability considerably and the leafy structure of the membranes contracted and the pure water permeation dropped with higher EVA content. The results of porosity measurement and scanning electronic microscopic (SEM) analysis also confirmed these findings. Contact angel measurements and atomic force microscopy (AFM) examinations and static absorption of collagen protein on the membrane surfaces revealed that EVA content up to 5 wt% lowered the hydrophobicity of the membrane. By EVA content above 10 wt%, due to the structural alteration on the membrane surface, the contact angel and the collagen absorption on the surface of membrane increased. The measurement of tensile strength showed that with increasing EVA content the mechanical properties of the membranes improved due to interactions of polar groups in EVA. http://jips.ippi.ac.ir/article_1241_44a0b7276e09161575f648c47af01854.pdf

Iranian Journal of Polymer Science and Technology 10163255 28 2 2015 06 22 Thermal and Mechanical Properties of Novolac-Silica Hybrid Aerogels Prepared by Sol-Gel Polymerization in Solvent-Saturated Vapor Atmosphere Thermal and Mechanical Properties of Novolac-Silica Hybrid Aerogels Prepared by Sol-Gel Polymerization in Solvent-Saturated Vapor Atmosphere 168 161 1248 10.22063/jipst.2015.1248 FA Mohamad Mehdi Seraji1, Seraji ACECR, Production Research Institute, P.O. Box:???, Ahwaz, Iran Azadeh Seifi Department of Polymer Engineering, Faculty of Chemical Engineering, Tarbiat Modares University, P.O. Box: 14115-114, Tehran, Iran Ahmad Reza Bahramian Department of Polymer Engineering, Faculty of Chemical Engineering, Tarbiat Modares University, P.O. Box: 14115-114, Tehran, Iran Journal Article 2015 07 02 Nowadays organic–inorganic hybrid aerogel materials have attracted increasing interests due to improved thermal and mechanical properties. In the present research, initially, novolac type phenolic resin-silica hybrid gels with different solid concentrations were synthesized using sol-gel polymerization in solvent-saturated<br />vapor atmosphere. The hybrid gels were dried at air atmosphere through ambient drying process. This method removed the need for costly and risky supercritical drying process. The yields of the obtained hybrid aerogels increased with less shrinkage in comparison with conventional sol-gel process. The precursor of silica phase in this study was tetraethoxysilane and inexpensive novolac resin was used as a reinforcing phase. The results of FTIR analysis confirmed the simultaneous formation of silica and novolac gels in the hybrid systems. The resultant hybrid aerogels showed a nanostructure hybrid network with high porosity (above 80%) and low density (below 0.25 g/cm3). Nonetheless, higher content of silica resulted in more shrinkage in the hybrid aerogel structure due to the tendency of the silica network to shrink more during gelation and drying process. The SEM images of samples exhibited a continuous network of interconnected colloidal particles formed during sol-gel polymerization with mean particle size of less than 100 nanometers. Si mapping analysis showed good distribution of silica phase throughout the hybrid structure. The results demonstrated improvements in insulation properties and thermal stability of novolac-silica aerogel with increasing the silica content. The results of compressive strength showed that the mechanical properties of samples declined with increasing the silica content. Nowadays organic–inorganic hybrid aerogel materials have attracted increasing interests due to improved thermal and mechanical properties. In the present research, initially, novolac type phenolic resin-silica hybrid gels with different solid concentrations were synthesized using sol-gel polymerization in solvent-saturated<br />vapor atmosphere. The hybrid gels were dried at air atmosphere through ambient drying process. This method removed the need for costly and risky supercritical drying process. The yields of the obtained hybrid aerogels increased with less shrinkage in comparison with conventional sol-gel process. The precursor of silica phase in this study was tetraethoxysilane and inexpensive novolac resin was used as a reinforcing phase. The results of FTIR analysis confirmed the simultaneous formation of silica and novolac gels in the hybrid systems. The resultant hybrid aerogels showed a nanostructure hybrid network with high porosity (above 80%) and low density (below 0.25 g/cm3). Nonetheless, higher content of silica resulted in more shrinkage in the hybrid aerogel structure due to the tendency of the silica network to shrink more during gelation and drying process. The SEM images of samples exhibited a continuous network of interconnected colloidal particles formed during sol-gel polymerization with mean particle size of less than 100 nanometers. Si mapping analysis showed good distribution of silica phase throughout the hybrid structure. The results demonstrated improvements in insulation properties and thermal stability of novolac-silica aerogel with increasing the silica content. The results of compressive strength showed that the mechanical properties of samples declined with increasing the silica content. http://jips.ippi.ac.ir/article_1248_3f3bfaafdd2873ea474f81a23a90a804.pdf