Meltem Çelik

Grafting of acrylamide–methacrylic acid mixture onto poly(ethylene terephthalate) fibers by azobisisobutyronitrile

The chemical grafting of acrylamide methacrylic acid (AAM-MAA) mixture onto poly(ethylene terephthalate) (PET) fibers using azobisisobutyronitrile as a chemical initiator was investigated. The use of MAA as a comonomer increased the amount of AAM introduced to the PET fiber up to 33.0%, while the grafting of AAM onto fibers alone gave low graft yields. This synergistic effect was found to be at its highest when an AAM-MAA mixture having 30 wt % AAM was used. The grafting increased dyeability with both acidic and basic dyes, and increased diameter and decreased the density of the fibers. The thermogravimetric analysis results revealed that the decomposition temperature of the fibers decreased with grafting. The electron micrographs showed that grafting changed the surface morphology of the fiber and a shell-like heterogeneous structure occurred at the surface at high graft yields.

Hydrogen peroxide initiated grafting of acrylamide onto poly(ethylene terephthalate) fibers in benzyl alcohol

The grafting of acrylamide onto poly(ethylene terephthalate) fibers using hydrogen peroxide as the redox initiator was investigated. Benzyl alcohol was found to be the favorite medium for this grafting. Maximum graft yield (7.6%) was reached at 95°C; the graft yield decreased at higher temperatures, and finally grafting was inhibited at 120°C. The effect of monomer and initiator concentration on grafting was also studied.

Synthesis, characterization, and properties of conducting polypyrrole/Na-montmorillonite nanocomposites

Polypyrrole/Na-montmorillonite nanocomposites were prepared by oxidative polymerization of pyrrole in aqueous medium using ammonium peroxydisulfate as the oxidant. The synthesized nanocomposites were confirmed by a series of characterization techniques including Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and thermal analysis. X-ray diffraction and transmission electron microscopy images showed that the polypyrrole was intercalated into the clay layers. The thermogravimetric analysis and differential thermal analysis revealed the improved thermal stability of nanocomposites with respect to pure polypyrrole due to modification of the incorporated Na-montmorillonite. Furthermore; adsorptive properties, the moisture retains, and water uptake values of nanocomposites were investigated. Conductivity behaviour of nanocomposites was also studied. The nanocomposites exhibit the room temperature conductivities varied from 1.2 × 10−8 S cm−1 to 8.7 × 10−8 S cm−1 range, depending on the amount of polypyrrole.

Study on the synthesis and properties of polyacrylamide/Na-montmorillonite nanocomposites

A series polyacrylamide/Na-montmorillonite nanocomposites was prepared by in situ free radical polymerization in aqueous medium using benzoyl peroxide (Bz2O2) as a radical initiator. To characterize the resultant nanocomposites, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis techniques were used. The moisture retain, water uptake, antibacterial properties, BET specific surface area and specific nanopore volume of nanocomposites were determined. The X-ray diffraction pattern showed that the polyacrylamide was intercalated up to 60.0 mass% acrylamide concentration, and then montmorillonite layers exfoliated into the polyacrylamide matrix. The interlayer spacing (d001) of the montmorillonite increased from 1.19 to 1.90 nm by intercalation. Transmission electron microscopy views showed that the Na-montmorillonite partially exfoliated in polyacrylamide. The nanocomposites exhibited better thermal stability than the pure polyacrylamide.

Synthesis and characterization of acrylic fibers-g-polyacrylamide

Graft copolymerization of acrylamide onto commercial acrylic fibers was carried out using benzoyl peroxide as a free-radical initiator in aqueous medium within the 75–95 °C temperature range. In this study, the effects of initiator and monomer concentration, the amount of fiber, polymerization time, and temperature on the graft yield were investigated. The optimum concentration for initiator was found to be 2.0×10−3 mol/l and the optimum temperature of 85 °C. The activation energy of the reaction was calculated to as 35.81 kJ/mol at the temperature interval of 75–95 °C. The structures and morphologies characterization of grafted fibers was investigated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The thermogravimetric analysis data showed that the thermal stability of the acrylic fibers increased with graft yield. The scanning electron photographs showed that the homogeneous appearance of the fiber surface changed and a shell-like heterogeneous structure occurred at the surface with an increasing degree of grafting. The moisture content, water absorption, dyeability, and antimicrobial activity of grafted acrylic fibers were also reported. The results showed that grafting of polyAAm improved the moisture contain, water absorption, dyeability, and antimicrobial activity of fiber.

Polythiophene/Na-montmorillonite composites via intercalative polymerization:

Conducting polythiophene (PTP)/Na-montmorillonite (Na-MMT) composites have been prepared by intercalative polymerization. The synthesized composites are characterized by Fourier transform infrared spectroscopy, x-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy (TEM), and thermal analysis. XRD and TEM images showed that the PTP was intercalated into the clay layers. The thermogravimetric analysis and the differential thermal analysis revealed the introduction of Na-MMT results in thermal stability of composites with respect to pure PTP. Furthermore, adsorptive properties, the moisture retention, and water uptake values of composites were investigated. Conductivity behavior of composites was also studied.

Preparation and characterization of poly(2-hydroxyethyl methacrylate)/ Na-montmorillonite intercalated nanocomposites

Abstract A series of intercalated nanocomposites were prepared via in situ polymerization of 2-hydroxyethyl methacrylate (HEMA) between the interlayer spacing of hydrous Na-montmorillonite (Na-MMT) using benzoyl peroxide (Bz2O2) as a radical initiator. X-ray diffraction patterns showed the absence of any intercalation up to 61.7 mass% of HEMA, but anhydrous Na-MMT formed by the hydrophilic effect of HEMA. The interlayer spacing (d001) values of hydrous and anhydrous Na-MMT were calculated as 1.19 and 1.03 nm, respectively. At higher monomer contents, the increase in the value of d001 from 1.19 to 2.01 nm indicated intercalation of polymer in the interlayer spacing of Na-MMT. Besides, transmission electron microscopy results supported the formation of the intercalated nanocomposites. Thermogravimetric analysis showed that the thermal stability of the nanocomposites increased considerably by intercalation of pure poly-HEMA. Specific surface area and specific nanopore volume of the nanocomposites decreased with the increasing of the monomer content taken by the preparations. The decrease is due to the nonporous nature of the polymer matrix.

Preparation, characterization, and properties of polystyrene/Na-montmorillonite composites

A series of polystyrene (PS)/unmodified Na-montmorillonite (Na-MMT) composites were prepared via in situ radical polymerization. The prepared composites were characterized using various techniques. The presence of various functional groups in the unmodified Na-MMT and PS/unmodified Na-MMT composite was confirmed by Fourier transform infrared spectroscopy. Morphology and particle size of prepared composites was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). According to the XRD and TEM results, the interlayer spacing of MMT layers was expanded. SEM images showed a spongy and porous-shaped morphology of composites. TEM revealed the Na-MMT intercalated in PS matrix. The thermal stability of PS/unmodified Na-MMT composites was significantly improved as compared to PS, which is confirmed using thermogravimetric analysis (TGA). The TGA curves indicated that the decomposition temperature of composites is higher at 24–51°C depending on the composition of the mixture than that of pure PS. The differential scanning calorimetry (DSC) results showed that the glass transition temperature of composites was higher as compared to PS. The moisture retention, water uptake, Brunauer–Emmett–Teller specific surface area, and specific pore volume of composites were also investigated. Water resistance of the composites can be greatly improved.

Synthesis and Characterization of Poly(N-Hydroxymethyl Acrylamide)/Na-Montmorillonite Composites

In this study, N-hydroxymethyl acrylamide ( HMAm ) monomer was mixed with Na-Montmorillonite (Na-MT) in different ratio. The mixture was polymerized in the presence of benzoyl peroxide (Bz 2 O 2 ) with in-situ radical polymerization to prepare poly(N-hydroxymethyl acrylamide) (PHMAm)/Na-Montmorillonite (Na-MT) composites. Purified Na-MT, and also produced composites with different ratio were characterized with Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal analysis (TGA/DTA) techniques . The moisture retention, water uptake, adsorptive properties of composites was also researched. The XRD pattern demonstrated that Na-MT layers intercalated into the PHMAm matrix. The composites displayed much better thermal stability than the pure polymer.