Nihan Nugay

Property optimization in nitrile rubber composites via hybrid filler systems

Nitrile rubber–PVC composites having carbon black and mica fillers in different compositions as hybrid reinforcements were studied. The effect of the silane treatment of mica, the degree of replacement, and the molecular architecture of nitrile rubbers on static-dynamic mechanical, swelling, and curing behavior of the resultant composites are discussed. The results showed that an increase in unsilanized and silanized mica total filler resulted in increased toughness values and decreased swelling in organic solvents together with increased vibrational damping capacity for all types of nitrile rubber composites, depending on the polyacrylonitrile content.

Anionic polymerization of primary acrylates as promoted by Lithium 2-(2-Methoxyethoxy) ethoxide

Some primary acrylates, such as methyl, ethyl, n-butyl, and n-nonyl acrylate (MA, EA, nBuA and nNonA, respectively) have been anionically polymerized by using diphenylmethyl lithium (DPMLi) as an initiator, in the presence of a chelating μ-σ dual ligand, i.e., a polydentate lithium alkoxide, at low temperature. It has been found that lithium 2-(2-methoxyethoxy) ethoxide (LiOEEM) is a very efficient ligand in preventing the anionic polymerization of these monomers from being disturbed by significant secondary transfer and termination reactions. Even for the difficult cases of ethyl and methylacrylate, that approach provides high polymerization yields and low polydispersity, allowing the molecular weight to be predetermined. LiOEEM/initiator molar ratio, solvent polarity, temperature and monomer concentration have proved to be key parameters in the control of the polymerization process. The efficiency of that control is however dependent on the monomer structure and improves with the length of the n-alkyl substituent, i.e., MA < EA < nBuA < nNonA.

Tuning of final performances of unsaturated polyester composites with inorganic microsphere/platelet hybrid reinforcers

Abstract Physical properties of fly ash/mica hybrid reinforced unsaturated polyester composites in both uncured and cured state have been studied with special reference to the effect of loading composition, nature of filler surfaces and surface treatment of fillers. Besides, effect of filler surfaces on curing characteristics of composites were all examined. In uncured state, viscosity measurement for composites was carried out. Tensile properties for cured fly ash/mica hybrid reinforced composites were found to increase with addition of mica in total filler. Effects of filler composition and silanization on loss factor ( tan δ ) were all discussed.

Swelling and static–dynamic mechanical behavior of mica‐reinforced linear and star‐branched polybutadiene composites

Physical properties of mica-reinforced linear (LPB) and star-branched polybutadiene (SPB) composites have been studied with special reference to the effect of silane coupling agent, degree of crosslinking, and degree of mica loading, as well as the molecular architecture of polybutadienes. Tensile properties increase and swelling decreases with addition of mica for linear polybutadiene. Star-branched polybutadiene shows a reverse behavior, especially beyond 5% of mica. The improvements in mechanical properties are more pronounced in the case of silane-treated mica compositions of both type of polybutadienes. Dynamic mechanical spectra were obtained for linear and star-branched polybutadienes. Effects of mica loading and silane treatment on dynamic moduli are discussed. Dynamic mechanical moduli (E′, E′) of composites increase with increasing mica content for linear polybutadiene but decrease for star-branched polybutadiene beyond certain mica loadings. Effective damping regions were determined in terms of frequency and temperature. The glass transition temperature (Tg) increased slightly, and the damping peak (tan δ) broadened due to the rubber—filler interaction, especially after silane treatment for both polymers.

Conductive properties of poly(4-vinylpyridine)-poly(dimethylsiloxane) block copolymers doped with tetracyanoquinodimethane

Abstract Poly(4-vinylpyridine)-poly(dimethylsiloxane) (P4VP-PDMS) block copolymers with various compositions were prepared by anionic polymerization. The 4VP block was quaternized with methyl iodide and reacted with 7,7′,8,8′-tetracyanoquinodimethane (TCNQ), which is in both anion radical (TCNQ − ) and neutral form (TCNQ 0 ). The products were then characterized by 1 H nuclear magnetic resonance and Fourier-transform infra-red spectroscopy, scanning electron microscopy and differential scanning calorimetry techniques. The electrical conductivities of processable and flexible films of these block copolymers were measured with the four-probe method and found to be as high as 10 −2 S cm −1 . The optimal TCNQ 0 doping for which the conductivities are highest were also determined.

A study on blends of low and high density polyethylenes: Effect of mixing time on mechanical, thermal properties and oxidative degradation

Abstract In this study, polyethylenes of high melt flow index LDPE and a medium melt flow index HDPE were melt blended. The mechanical, thermal properties and the thermal oxidative degradation were studied as a function of four different mixing times. The results were evaluated according to the blend composition and time of mixing. The tensile strength was found to be affected mostly by mixing time as compared with the elongation at break while the modulus remained unchanged with time of mixing. The thermal oxidative degradation of the blends were found to be less than the corresponding pure components.

Renewable Polymeric Nanocomposite Synthesis Using Renewable Functionalized Soybean-Oil-Based Intercalant and Matrix

Completely bio-based and renewable polymeric nanocomposites have been prepared using an in situ polymerization technique in the presence of organically-modified montmorillonite (MMT) clays in different loading degrees. Acrylated epoxidized soybean oil (AESO) and styrene have been used as matrices, whereas modification of MMT has been done by using a new renewable soybean-oil-based intercalant, quarternized functionalized acrylated epoxidized soybean oil, which is the first renewable intercalant described in the literature. It was found that the above-mentioned intercalant could be successfully intercalated between the interlayer galleries of montmorillonite which is confirmed by X-ray diffraction (XRD) data and atomic force microscopy (AFM). The nanocomposite formation studies examined by both XRD and AFM showed that the desired exfoliated nanocomposite structures can be achieved with all nanofiller loadings. The resultant exfoliated nanocomposites were found to have significantly improved thermal stability and dynamic mechanical performance at very low loadings. The nanocomposites from both renewable intercalant and matrix offer a significant potential for new high-volume, low-cost applications.

Ligated anionic block copolymerization of methyl methacrylate with n-butyl acrylate and n-nonyl acrylate as promoted by lithium 2-(2-methoxyethoxy) ethoxide/diphenylmethyllithium

Poly(methyl methacrylate-b-n-butyl acrylate) (PMMA-b-Pn-BuA) and poly(methyl methacrylate-b-n-nonyl acrylate) (PMMA-b-Pn-NonA) diblock copolymers have been successfully synthesized by the sequential anionic polymerization of methyl methacrylate (MMA) and the n-alkyl acrylate (n-BuA or n-NonA), in a 90/10 toluene/ tetrahydrofuran (THF) mixture at -78°C. When diphenylmethyllithium (DPMLi) ligated with lithium 2-(2-methoxyethoxy) ethoxide (LiOEEM) is used as the initiator, the polymerization of each block appears to be living. Molecular weight and composition of block copolymers can be predicted from the monomer over initiator molar ratio and the molecular weight distribution is narrow. Size exclusion chromatography (SEC) supports that no homo-PMMA contaminates the final copolymer. Although the reverse polymerization sequence Pn-NonA-b-PMMA always results in some contamination by homo-Pn-NonA, it has no really significant effect on the final product characteristics.

Conducting properties of iodine-doped poly(4-vinylpyridine)-poly(dimethylsiloxane) block copolymers

Abstract Block copolymers of various compositions, consisting of poly(4-vinylpyridine)(P4VP) and poly(dimethylsiloxane) (PDMS) blocks, were prepared by anionic polymerization. These samples were modified by the addition of various amounts of iodine in solution. The electrical conductivities of the doped materials were measured by the four-probe method and were found to be as high as 10 −5 S cm −1 . The optimum ratio of iodine to pyridine which gave the highest conductivity was determined.

Inter polymer complexes of poly(methyl methacrylate)-block-poly(4-vinylpyridine) with polyacrylic acid and polyacrylic acid-block-poly(methyl methacrylate)

Abstract Inter polymer complex formations between poly(methyl methacrylate)-block-poly(4-vinylpyridine) diblock copolymer and polyacrylic acid as well as poly(acrylic acid)-block-poly(methyl methacrylate) diblock copolymers have been studied. The structures of the complex were identified with 1H-NMR, FTIR and differential scanning calorimetry techniques. The thermal stability of the complexes was investigated by thermogravimetric analysis. Optical clarity of the block copolymer complexes were determined.