دو ماهنامه علوم و تکنولوژی پلیمر
سال بیست و ششم شماره 5 (پیاپی 127، آذر و دی 1392)

POY PET fiber samples were uniaxially drawn below the glass transition temperature (Tg) at various draw ratios to obtain filaments with different transient structures. The transient structure was composed of polymeric chains with para-crystalline or mesomorphic order and played a key role on the ultimate properties of fibers. Therefore، the study of the post-treatment mesomorphic structural changes would be of great interest. Initially the samples were exposed to supercritical CO2 under tension and tension-free conditions to induce morphological changes in their structures. The evolution of micro-structural changes under exposure to supercritical CO2 was investigated by conventional methods such as DSC، FTIR، birefringence and mechanical properties. A good correlation was obtained between the results of various analytical studies. Analyzing the results of DSC and FTIR showed that the amount of extended chains and transient structure developing during cold-drawing increased with the draw ratio. The results showed that exposure to supercritical CO2 led to the absorption of CO2 molecules into the free volumes of amorphous phase of the samples and increasing the crystalline phase and lowering the transient structures in the treated fibers. Sample treatment conditions play important role on the structural changes and in transforming the oriented chains of the mesophase into the crystalline or non-crystalline domains. PET fibers exposed to supercritical CO2 under tension present higher degree of crystallinity and molecular compactness in the amorphous domains but lower values of transient structures than the non-tension exposed samples. Exposure to supercritical CO2 gave rise to such structural changes as crystallization، orientation، and mesomorphic transitions. Hence، this method is a promising approach for tailoring structural changes in PET samples. In this paper، samples of POY PET fibers were uniaxially drawn below the glass transition temperature (Tg) at various draw ratios to obtain filaments with different transient structures. The transient structure composed of polymeric chains with paracrystalline or mesomorphic order and has a key role on the ultimate properties of fibers. So، it will be interesting to learn about the post-treatment mesomorphic changes that occur in this structure. The samples were exposed to scCO2 under and without tension-conditions to induce morphological changes in them. The evolution of micro structural changes under exposure to scCO2 was investigated by conventional methods such as DSC، FTIR، birefringence and mechanical propreties. A good correlation was obtained between the results of various analyses. Analyzing the results of DSC and FTIR showed that the amount of extended chains and transient structure developing during cold-drawing increased with the draw ratio. Results showed that exposure to scCO2 led to the absorption of CO2 molecules into the free volumes of amorphous phase in the samples as well as increasing their crystallinity and decreasing the amount of transient structure in the treated fibers. Sample treatment conditions have an important role on the structural changes and in transforming the oriented chains in the mesophase into the crystalline or non-crystalline domains. PET fibers exposed to scCO2 under tension present higher values of crystallinity and molecular compactness in the amorphous domains but lower values of transient structures than the samples exposed without tension. Exposure to scCO2 gives rise to such structural changes as crystallization، orientation، and mesomorphic transitions. Hence، this method is promising for tailoring structural changes in PET samples.

Determination of fluoride in drinking water has received increasing interest، due to its beneficial and detrimental effects on health. Contamination of drinking water by fluoride can cause potential hazards to human health. In recent years، considerable attention has been given to different methods for the removal of fluoride from drinking and waste waters. The aim of this research was to investigate the effect of nano composite hydrogel based on starch/sodium acrylate/aluminum oxide in reduction of fluoride concentration in drinking water and industrial waste water. In a batch system، the dynamic and equilibrium adsorption of fluoride ions were studied with respect to changes in determining parameters such as pH، contact time، initial fluoride concentration، starch/acrylic acid weight ratio and weight percent of nano aluminum oxide. The obtained equilibrium adsorption data were fitted with Langmuir and Freundlich models، as well as the kinetic data with pseudo-first order and pseudo- second order models. The results showed that optimum pH was found to be in the range of 5 to 7. Removal efficiency of fluoride was increased with decreases in initial concentration of fluoride. Sixty percent of initial value of fluoride solution was removed by nano composite hydrogel (4 wt% of nano aluminum oxide) at 240 min (initial fluoride concentration = 5 ppm، pH 6. 8 and temperature = 25ºC). Under the same condition، the equilibrium adsorption of fluoride ions was 85% and 68% for initial solution concentration of 5 and 10 ppm، respectively. Adsorption isotherm data showed that the fluoride sorption followed the Langmuir model. Kinetics of sorption of fluoride onto nano composite hydrogel was described by pseudo-first order model.

In recent years، waterborne polyurethanes as in coatings and adhesives formulations have attracted considerable attention because they are non-toxic، non-flammable and friendly to environment. Besides environmental management، the flexibility، low temperature property، high tensile strength، good adhesion and improved rheological property are specific properties of waterborne polyurethanes. Also low production cost of water borne polyurethanes over solvent-borne polyurethanes is also a reason for their applications. However، these materials have some defects such as weak water resistance and low adhesion in the moisture environment due to sensitivity of their hydrophilic ionic bonds، ether groups، urethane and ester groups to hydrolysis which need to be improved. Also، low heat resistance of these materials is due to a relatively low crystalline melting point or glass transition temperature of hard segments. One of the ways to solve this problem and improve its properties for different applications is the addition of inorganic fillers especially nano-sized layered silicates within polyurethane matrix. In this way water resistance، heat resistance، mechanical properties and modulus increase simultaneously. In this research، waterborne polyurethane nanocomposites with PTMG polyol، IPDI، DMPA (internal emulsifier)، TEA (neutralizer) and 1، 3 and 5weight % of Cloisite 30B as reinforcement were synthesized and characterized. Polarity of the samples was investigated by contact angle test and dispersion of nano particles in the samples was characterized by X-Ray and TEM، Thermal properties and dynamic mechanical properties were measured by TGA and DMTA، respectively. The results showed that incorporation of clay into polyurethanes did reduce water absorption and increased heat resistance، modulus، particle size and contact angle. In recent years، waterborne polyurethanes including coatings and adhesives have attracted considerable attention because they are non-toxic، non-flammable and friendly to environment. Besides environmental management، flexibility، low temperature property، high tensile strength good adhesion and improved rheological property are specific evidence of waterborne polyurethanes. Also low production cost of water borne polyurethane over solvent-borne polyurethanes is also a reason for their applications. However، these materials have some defects such as weak water resistance and low adhesion in the moisture environment due to sensitivity of their hydrophilic ioned bonds، ether groups، urethane groups and ester groups to hydrolysis which are needed to be improved. Also، low heat resistance of these materials is due to relatively low crystalline melting point or glass transition temperature of hard segments. One of the ways to solve this problem and improve its properties for different application is the addition of inorganic fillers especially nanosized layered silicates within polyurethane matrix. In this way water resistance، heat resistance، mechanical properties and modulus increase. In this research، waterborne polyurethane nanocomposites with PTMG polyol، IPDI، DMPA (internal emulsifier)، TEA (neutralizer) and 1، 3 and 5weight % of cloisite 30B as reinforcement were synthesized and characterized. Polarity of the samples was investigated by Contact angle test، dispersion of nano particles in the samples were characterized by X-Ray and TEM، Thermal properties and dynamic mechanical properties were measured by TGA and DMTA respectively. Results showed that incorporation of clay into polyurethane samples caused the reduction of water absorption، increasing of heat resistance، modulus، particle size and contact angle.

The effect of nanoclay (Cloisite® 15A) was studied in relation to the flow behavior، mechanical and thermal properties of polypropylene/maleic anhydride-g- (styrene-ethylene-butylene-styrene) triblock copolymer (PP/SEBS(15%) -g-MA) blend. In this regard، the composites based on the blend and various amounts of nanoclay (1،3،5 wt%) were melt compounded using an internal mixer at the temperature of 190°C، rotor speed of 75rpm for 12min. The prepared samples were compression molded in a hot-press machine under the conditions of 190°C، 31 MPa pressure for 9 min to obtain the sheets in various thicknesses. The sheets were then cooled to ambient temperature with cooling water at the rate of 1. 5°C. s-1. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to study the structure and morphology of the samples. In addition، the mechanical and thermal properties were determined by standard methods. The results of X-ray diffraction and transmission electron photographs confirmed both exfoliated and intercalated structures in the prepared samples. There were balanced strength/toughness properties in all the prepared nanocomposites by addition of both SEBS-g-MA and clay simultaneously. The measurement of rheological properties showed that as the shear rate increased، the apparent viscosity of the samples decreased (shear thinning behavior). Gradual increase in incorporation of nanoclay also decreased the melt flow index (MFI) values. In addition، increases in nanoclay content had an insignificant effect on the thermal behavior and in that respect there were slight increases in degree of crystallinity، heat deflection temperature (HDT) as well as Vicat softening point by slight increase in temperatureThe effect of nanoclay (Cloisite® 15A) was studied in relation to the flow behavior، mechanical and thermal properties of polypropylene/maleic anhydride-g- (styrene-ethylene-butylene-styrene) triblock copolymer (PP/SEBS(15%) -g-MA) blend. In this regard، the composites based on the blend and various amounts of nanoclay (1،3،5 wt%) were melt compounded using an internal mixer at the temperature of 190°C، rotor speed of 75rpm for 12min. The prepared samples were compression molded in a hot-press machine under the conditions of 190°C، 31 MPa pressure for 9 min to obtain the sheets in various thicknesses. The sheets were then cooled to ambient temperature with cooling water at the rate of 1. 5°C. s-1. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to study the structure and morphology of the samples. In addition، the mechanical and thermal properties were determined by standard methods. The results of X-ray diffraction and transmission electron photographs confirmed both exfoliated and intercalated structures in the prepared samples. There were balanced strength/toughness properties in all the prepared nanocomposites by addition of both SEBS-g-MA and clay simultaneously. The measurement of rheological properties showed that as the shear rate increased، the apparent viscosity of the samples decreased (shear thinning behavior). Gradual increase in incorporation of nanoclay also decreased the melt flow index (MFI) values. In addition، increases in nanoclay content had an insignificant effect on the thermal behavior and in that respect there were slight increases in degree of crystallinity، heat deflection temperature (HDT) as well as Vicat softening point by slight increase in temperature. The aim of this work is to study effect of nanoclay (Cloisite® 15A) on the flow behavior، mechanical and thermal properties of polypropylene/maleic anhydride grafted- (styrene-ethylene-butylene- styrene) triblock copolymer (PP/15%SEBS-g-MA) blend. In this regard، the composites based on the blend and various amounts of nanoclay (1،3،5 wt. %) were melt compounded using an internal mixer at the temperature of 190oC، rotor speed of 75rpm for 12min. The prepared samples were then compression molded in a hot-press machine under the conditions of 190°C، 31 MPa pressure، for 9 min to obtain the sheets in various thicknesses. Afterwards، the plates were cooled to ambient temperature with cooling water at the rate of 1. 5oC. s-1. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to study the structure and morphology of the samples. In addition، the mechanical and thermal properties were carried out by means of the standard methods. The results of X-ray diffraction and transmission electron photographs confirm both exfoliated and intercalated structures in the prepared samples. There is balanced strength/toughness properties in all the prepared nanocomposites via addition both SEBS-g-MA and clay simultaneously. The measurement of rheological properties show that as the shear rate increases، the apparent viscosity of the samples decreases (shear thinning behavior). Incorporation of nanoclay and increasing its content also decreases the melt flow index (MFI) values. In addition، increase in the nanoclay content have the insignificant effect on the thermal behavior so that slight increase in crystallinity temperature/degree، heat deflection temperature (HDT) as well as vicat softening point are obtained.

Nanoliposomes are one of the most important polar lipid-based nanocarriers which can be used for encapsulation of both hydrophilic and hydrophobic active compounds. In this research، nanoliposomes based on lecithin-polyethylene glycol-gamma oryzanol were prepared by using a modified thermal method. Only one melting peak in DSC curve of gamma oryzanol bearing liposomes was observed which could be attributed to co-crystallization of both compounds. The addition of gamma oryzanol، caused to reduce the melting point of 5% (w/v) lecithin-based liposome from 207°C to 163. 2°C. At high level of lecithin، increasing of liposome particle size (storage at 4°C for two months) was more obvious and particle size increased from 61 and 113 to 283 and 384 nanometers، respectively. The encapsulation efficiency of gamma oryzanol increased from 60% to 84. 3% with increasing lecithin content. The encapsulation stability of oryzanol in liposome was determined at different concentrations of lecithin 3، 5، 10، 20% (w/v) and different storage times (1، 7، 30 and 60 days). In all concentrations، the encapsulation stability slightly decreased during 30 days storage. The scanning electron microscopy (SEM) images showed relatively spherical to elliptic particles which indicated to low extent of particles coalescence. The oscillatory rheometry showed that the loss modulus of liposomes were higher than storage modulus and more liquid-like behavior than solid-like behavior. The samples storage at 25°C for one month، showed higher viscoelastic parameters than those having been stored at 4°C which were attributed to higher membrane fluidity at 25°C and their final coalescence. Nanoliposomes are one of the most important polar lipid based nanocarriers which can be used for encapsulation of both hydrophilic and hydrophobic active compounds. In this research، nanoliposomes based on lecithin-polyethylene glycol-gamma oryzanol were prepared by using modified thermal method. Only one melting peak in DSC curve of gamma oryzanol bearing liposomes was observed which could be attributed to co-crystallization of both compounds. The adding of gamma oryzanol، caused to reduce the melting point of 5% (W/V) lecithin based liposome from 207 ˚C to 163. 2 ˚C. In high level of lecithin، increasing of liposome particle size (storage at 4 ˚C for two months) was more observable and particle size increased from 61 and 113 to 283 and 384 nanometers، respectively. The encapsulation efficiency of gamma oryzanol increased from 60% to 84. 3 % with increasing lecithin content. The encapsulation stability of oryzanol in liposome was determined at different concentration of lecithin 3، 5، 10، 20% (W/V) and different storage time (1،7، 30 and 60 days). In all concentration، encapsulation stability slightly decreased during 30 days storage. The scanning electron microscopy (SEM) images showed relatively spherical to elliptic particle which indicating low extent of particles coalescence. The oscillatory rheometry showed that the loss modulus of liposome samples were higher than storage modulus and more liquid like behavior than solid like behavior. The samples storage at 25 ˚C for one month، showed higher viscoelastic parameters than those storage at 4 ˚C which attributed to higher membrane fluidity at 25 ˚C and resulting coalescence.

Aerogels consist of low density open-cell foams with large void spaces of nanometer pore size and they are composed of sparsely semi-colloidal nanometer sized particles forming open porous structures. The high porosity and nanometer pores and particles of aerogels have interesting properties such as low thermal conductivity and low sound transmission. The main disadvantages of conventional method for preparation of aerogels are high cost of resorcinol، long preparation time and high cost of supercritical drying device. The previous research showed that sol-gel polymerization lower than temperature of normal boiling point of solvent، and a 50°C difference in temperature between the novolac resin synthesis and the temperature of curing novolac resin is the main reason for long sol-gel polymerization time. A low temperature polymerization is used for prevention of solvent evaporation and foam blowing process. The objectives of this research were to reduce time and cost in the production process of organic aerogels. To reduce the cost of raw materials، the reaction of a low cost commercial novolac resin and HMTA were used for preparation of the gel. To reduce gelation time، the polymerization was performed in an atmosphere of solvent saturated-vapor as a novel method to restrict sol-gel polymerization of curing novolac resin at appropriate temperature. The investigation showed that the polymerization carried out in solvent-saturated vapor did help to reduce polymerization time to 5 h from 5 days duration in conventional reactions without any visible shrinkage under ambient pressure and temperature. Furthermore، the compressive strength increased by one order of magnitude besides other achievements. Aerogels comprise class of low density open-cell foams with large void space، nanometer pore size and they are composed of sparsely semi-colloidal nanometer sized particles forming open porous structures. The high porosity and nanometer pores and particles of aerogels results interesting properties such as low thermal conductivity and low sound propagation speed. The main disadvantages of conventional method for preparation of aerogels are high cost of resorcinol، long preparation time and high cost of supercritical drying device. The previous research showed that sol-gel polymerization lower than temperature of standard boiling point of solvent، also 50 °C differences between appropriate temperatures for curing novolac resin and the performed temperature of curing novolac resin is the main reason for long time of sol-gel polymerization. The low temperature polymerization used for prevention of solvent evaporation and solution blowing. The objectives of this research are reducing time and cost in the production process of organic aerogels. To reduce the cost of raw material، the reaction of low cost commercial novolac resin and HMTA were used for preparation of gel. To reduce gelation time، the polymerization in saturated atmosphere of vaoer of solvent as a novel method for domination of restriction sol-gel polymerization temperature curing novolac resin in appropriate temperature is proposed. The investigation shows that the polymerization in saturated atmosphere of solvent vapor، reducing time of polymerization from 5 days to 5 hours without any observable shrinkage in ambient atmosphere. Furthermore، the compressive strength increased one order and it’s other important achievements of this research.

The effect of alkaline hydrolysis with sodium hydroxide on nano titanium dioxide (nano TiO2) adsorption was studied on polyester fabric surface as well as the influence of nano TiO2 on the alkaline hydrolysis of polyester. To do this، the polyester fabrics were treated with different concentrations of nano TiO2 and boiling sodium hydroxide solution for 1 h. The results revealed that alkaline hydrolysis reduced the weight of the fabric، which was more prominent in presence of nano TiO2. Field emission scanning electronic microscope and energy dispersive X-ray confirmed the presence of nano TiO2 on the polyester fabric surface. Increasing sodium hydroxide and nanoTiO2 concentrations led to higher loading of nano particles on the polyester fabric surface. Also، the photocatalytic activity of nano TiO2 particles on the polyester fabric was confirmed by the degradation of methylene blue as a model stain under daylight irradiation. The results indicated that increasing sodium hydroxide and nano TiO2 concentrations led to higher photocatalytic activities of the alkali-treated polyester fabrics. Further، the bending rigidity of the treated polyester fabrics decreased while the water absorption of the fabric improved. Unexpectedly، the tensile strength of the nano TiO2 treated polyester fabrics improved even with the action of alkali and surface hydrolysis that usually produce fabric with lower tensile strength. The synergism influence of nano TiO2 particles in alkali hydrolysis of polyester fabric indicated to lower weight fabrics. Overall، this treatment was considered as another useful property such as higher self-cleaning، hydrophilicity and tensile strength.