The effects of a silane coupling agent on curing characteristics and mechanical properties of bamboo fibre filled natural rubber composites

The effects of a silane coupling agent on curing characteristics and mechanical properties of bamboo fibre filled natural rubber composites were studied. Scorch time, t₂ and cure time, t₉₀ of the composites decrease with increasing filler loading and with the presence of a silane coupling agent, Si69. Mooney viscosity also increases with increasing filler loading but at a similar filler loading shows lower value with the presence of Si69. The mechanical properties of composites viz tensile strength, tear strength, hardness and tensile modulus were also improved with the addition of Si69.     

Allylic monomers as reactive plasticizers of polyphenylene oxide. Part I: Uncured systems

The effect of various diallyl (diallyl ortho phthalate, diallyl terephthalate and diethylene glycol diallyl carbonate) and triallyl monomers (triallyl cyanurate and triallyl isocyanurate) on the processability of polyphenylene oxide (PPO) was studied. The solubility parameters of the monomers indicated that diallyl orthophalate, dially terephthalate and triallyl cyanurate should be miscible with PPO suggesting their applicability as reactive plasticizers to improve the processability of PPO. Rheological studies of 60:40 wt:wt PPO:allylic blends indicate that the addition of 40 wt% of allylic monomers significantly improved processability – blends of 60PPO:40DEGDAC indicates the highest viscosity and the highest T_g. Rheological studies and dynamic mechanical analysis on various PPO/DAOP blends show that the increasing amounts of DAOP progressively decreases the viscosity and T_g of the blends. Phase separation at room temperature was observed by visual opacity, cloud point studies and DMTA in PPO:DAOP blends with less than 60 wt% PPO but at elevated temperatures the blends were miscible.     

Propargyl silicon‐cyclopentadiene oligomeric resin with high temperature resistance

Multiple propargyl substituted cyclopentadiene was synthesized by phase transfer reaction between cyclopentadiene and propargyl bromide in an aqueous solution mediated by sodium hydroxide. It was found that propargylated cyclopentadiene (PCp) could be thermally cured with a mass loss of ca 28%, while the cured material showed a high char yield of ca 76% at 900°C. In order to overcome the processing problems of PCp, a condensation reaction between PCp di‐anion and dimethyldichlorosilane was performed to make a silicon‐PCp (SiPCp) oligomeric resin. SiPCp resin has an acceptable processability, attributed to its organosolubility, low viscosity, and broad processing window. SiPCp resin can readily undergo thermal cure via addition polymerization of ethynyl groups in the temperature range of 170–270°C with an exothermic maximum at ca 240°C, and the mass loss upon cure was less than 5%. Evidenced by the results of dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) in a nitrogen atmosphere, the cured SiPCp resin exhibited stable thermo‐mechanical properties up to 320°C, and possessed an anerobic char yield of ca 77% at 900°C. The results of TGA in air atmosphere revealed the higher oxidation resistance of SiPCp resin. Copyright © 2008 John Wiley & Sons, Ltd.     

Comparison of reinforcing efficiency between Si-69 and Si-264 in a conventional vulcanization system

Silica has long been recognized as a reinforcing filler, especially for light colored products. The degree of reinforcement is noticeably increased when silica is used in combination with silane coupling agent. Therefore, various types of silane coupling agents are now commercially available. In the present study, two types of silane coupling agents, e.g., bis-(3-triethoxysilylpropyl) tetrasulfane (Si-69) and 3-thiocyanatopropyl triethoxy silane (Si-264) were selected for comparison of their reinforcing efficiency in a conventional vulcanization (CV) system. The results reveal that the addition of silane coupling agent not only improves compound processability, but also enhances the mechanical properties of the rubber vulcanizates. Compared with Si-69, Si-264 gives rubber compounds with better processability due to its greater ability to promote filler dis-agglomeration during mixing. In addition, Si-264 also imparts a greater degree of reinforcement. This might be attributed to the combined effects of better rubber–filler interaction, better filler dispersion and higher state of cure which are obtained when Si-69 is replaced with Si-264. The dynamic properties of the rubber vulcanizates are also improved with the presence of silane coupling agent. In this aspect, Si-69 performs better than Si-264 as it provides rubber vulcanizates with lower heat build-up.     

The physicochemical and thermophysical properties of sodium dodecyl sulfate: The influence of p-toluene sulfonyl chloride and temperature

In the present study, we report on the interaction between a hydrotrope, p-toluene sulfonyl chloride (p-TSC), and an anionic surfactant, sodium dodecyl sulfate (SDS) which has been performed using electrical conductivity, Fourier transform infrared (FTIR), ¹H NMR, density, dynamic viscosity, and kinematic viscosity measurements. The effect of p-TSC on the micellization of SDS in non-aqueous (ethanol) medium at various temperatures (viz., 298.15, 303.15, 308.15, 313.15, 318.15, and 323.15 K) was investigated using the electrical conductivity method. The results show that the CMC value increases as the concentration of the hydrotrope is increased. It is noteworthy that at higher concentrations of hydrotrope, the trend of micelle formation is reversed (i.e., reverse micelles are formed). The thermodynamic parameters in micellization have also been evaluated. The FTIR and ¹H NMR data reveal the physicochemical properties of the pure and mixed systems and confirm no covalent bond formation takes place. Density, dynamic viscosity, and kinematic viscosity of the pure as well as mixed systems at various temperatures were also reported.     

Liquid Nickel Salts: Synthesis,Crystal Structure Determination,and Electrochemical Synthesis of Nickel Nanoparticles

New nickel‐containing ionic liquids were synthesized, characterized and their electrochemistry was investigated. In addition, a mechanism for the electrochemical synthesis of nanoparticles from these compounds is proposed. In these so‐called liquid metal salts, the nickel(II) cation is octahedrally coordinated by six N‐alkylimidazole ligands. The different counter anions that were used are bis(trifluoromethanesulfonyl)imide (Tf₂N^?), trifluoromethanesulfonate (OTf^?) and methanesulfonate (OMs^?). Several different N‐alkylimidazoles were considered, with the alkyl sidechain ranging in length from methyl to dodecyl. The newly synthesized liquid metal salts were characterized by CHN analysis, FTIR, DSC, TGA and viscosity measurements. An odd‐even effect was observed for the melting temperatures and viscosities of the ionic liquids, with the complexes with an even number of carbon atoms in the alkyl chain of the imidazole having a higher melting temperature and a lower viscosity than the complexes with an odd number of carbons. The crystal structures of several of the nickel(II) complexes that are not liquid at room temperature were determined. The electrochemistry of the compounds with the lowest viscosities was investigated. The nickel(II) cation could be reduced but surprisingly no nickel deposits were obtained on the electrode. Instead, nickel nanoparticles were formed at 100 % selectivity, as confirmed by TEM. The magnetic properties of these nanoparticles were investigated by SQUID measurements.     

Impact of surface adaptation and Acacia nilotica biofiller on static and dynamic properties of sisal fiber composite

Nowadays, the awareness of the public along with strict legitimate forces over the use of polymers, the manufacturing and automotive industries started using the renewable materials. Since, natural fiber reinforced composites play vital role in developing lightweight structural materials, this study focuses on utilizing sisal fiber as reinforcement in polyester matrix along with natural filler. The influence of fiber length and fiber volume fraction on the mechanical properties of sisal fiber was studied initially. Test results revealed that the composite with 20?mm fiber length and 20-volume fraction composite has better mechanical properties. Furthermore, the effect of fiber surface modification has been analyzed using various chemical solutions such as NaOH, KMnO₄, stearic acid, and maleic acid. Of these, NaOH treatment enhances the mechanical properties of composite compared to all other cases. Finally, the influence of Acacia nilotica, a natural filler addition into the alkali-treated sisal fiber composite has been evaluated by mechanical and dynamic mechanical properties. It is found that the addition of natural filler and surface treatment has enhanced the properties of composites due to their synergetic effect. This effect improves the adhesion and uniform stress transfer among the reinforcements. The fiber surface morphology was evaluated using micrographs obtained from scanning electron microscope.     

Development in synthesis and electrochemical properties of thienyl derivatives of carbazole

A convenient and higher yielding synthetic route to N-alkyl-bis(thiophene)- and N-alkyl-bis(ethylenedioxythiophene) carbazole derivatives is reported and their aggregation, and electrochemical properties are characterized. The key step in the synthesis of this group of compounds has been the Stille-type coupling reaction between the N-alkyldibromocarbazole and tin derivatives of thiophene or ethylenedioxythiophene, as the best way for preparation of conjugated N-alkylcarbazole derivatives. For this group of compounds we also present an electrochemical polymerization effect.     

Investigations on the recycling of hemp and sisal fibre reinforced polypropylene composites

Microscopic, mechanical, rheological and thermal tests were carried out in order to determine the recycling behaviour of PP/vegetal fibre composites. Different composites using hemp and sisal were characterized. All results were compared with PP-g-MA/hemp composites and PP/glass fibre composites.The results prove that mechanical properties are well conserved with the reprocessing of PP/vegetal fibre composites but that there is poor adhesion between the fibres and PP without any treatment. The addition of PP-g-MA shows an improvement of the bonding evidenced by MEB pictures. Vegetal fibres induce an increase in the percentage of crystallinity χ_c and in the crystallization temperature T_c which can be explained by the nucleating ability of the fibres improving crystallization of PP. The Newtonian viscosity η₀ decreases with cycles, indicating a decrease in molecular weight and chain scissions induced by reprocessing. The decrease of fibre length with reprocessing could be another reason for viscosity decrease.     

Processing and Dynamic-Mechanical Properties of Poly(butylen terephthalate) Based Nanocomposites

Effects related to the simultaneous presence of an Al-phosphinate based fire retardant and of relatively low amounts of nanosized metal oxide particles on processability and mechanical performances of a commercial polyester resin have been investigated. In more details, ternary poly(buthylene terephtalate) based compounds, obtained by melt processing and first of all validated in terms of flammability, were analysed to verify the relative extrudability and ultimate dynamic mechanical performances of compression moulded samples. Preliminary rheological tests confirmed both a minimum of matrix degradation as a result of the process while applying an appropriate protocol drying of raw materials and a marked reduction of the apparent shear viscosity of the three-phase melts with respect to the neat matrix processed under the same conditions. Regarding the evaluation of dynamic-mechanical parameters such as storage modulus, loss modulus and the ratio tan δ, besides the expected stiffening of the matrix by inclusion of a rigid inorganic phase, a slight reduction of damping behaviour without no significant variation of the glass transition temperature of the polyester matrix have been observed.     

Study on thermal cure and heat-resistant properties of N-(3-acetylenephenyl)maleimide monomer

N-(3-acetylenephenyl)maleimide (3-APMI), was synthesized by reacting 3-aminophenylacetylene (3-APA) with maleic anhydride by the usual two-step procedure that included ring-opening addition to give maleamic acid, followed by cyclodehydration to maleimide. Structure of the monomer was confirmed by Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (¹H NMR), elemental analysis (EA) and mass spectrum (MS). Thermal cure of the monomer was investigated by differential scanning calorimetry (DSC) and FTIR, then processing parameters and cure kinetics parameters were determined. The results showed that the monomer possesses excellent reactivity, whose cure peak temperature was 197.9 °C and cure reaction was almost complete after 4 h cure at 200 °C. Thermal properties of the cured monomer were determined by dynamic mechanical analysis (DMA) and the results show that glass transition temperature (represented by onset temperature of storage modulus) is high up to 460 °C. The results of thermogravimetry analysis (TGA) reveal that the cured monomer possessed excellent thermal stability, whose 10% weight loss temperature (T_10%) is 515.6 °C and char yield at 800 °C is 59.1%. All these characteristics make the 3-APMI monomer be an ideal candidate for matrix of thermo-resistant composites.     

Preparation and characterization of novel organosoluble and thermally stable poly(benzimidazole-amide)s bearing phthalimide pendent groups

Novel aromatic poly(benzimidazole-amide)s, PBAs, have been synthesized by direct polycondensation of a new dicarboxylic acid, N-[3,5-bis(5-carboxylic acid-2-benzimidazole) phenyl]phthalimide (1), containing performed benzimidazole rings and a phthalimide pendent group with various aromatic diamines. The dicarboxylic acid was synthesized by reaction of 5-(N-phthalimide)isophthalic acid with 4-methyl-1,2-phenylenediamine in polyphosphoric acid, followed by its oxidation into relative dicarboxylic acid. To study the structure-property relationships of 1,3-bis(5-carboxylic acid-2-benzimidazole)benzene (2, as a reference) this compound was also synthesized. The chemical structure of 1 and 2 were confirmed by the spectroscopic methods and elemental analyses. The characterization of the polymers was performed with inherent viscosity measurements, solubility tests, FT-IR, Ultraviolet and ¹H NMR spectroscopy and thermogravimetry. The polymers were obtained in quantitative yields with inherent viscosities between 0.53 and 0.91 dl g⁻¹. The effects of the phthalimide pendent group on the polymer properties such as solubility and thermal behavior were investigated and compared with those of the corresponding unsubstituted poly(benzimidazole-amide)s. The modified poly(benzimidazole-amide)s showed enhanced solubilities in some solvents, such as m-cresol and pyridine, in comparison to the unmodified analogues. In addition, the incorporation of the pendent phthalimide groups in the poly(benzimidazole-amide)s backbone increased remarkably the thermal stability of the polymer. The glass transition temperature and 10% weight loss temperature of the poly(benzimidazole-amide)s were in range of 291-334 °C and 466-540 °C, respectively, in nitrogen.     

Preparation and properties of dynamically cured poly(vinylidene fluoride)/silicone rubber blends

Blends of poly(vinylidene fluoride) (PVDF) and silicone rubber (SR) were prepared through dynamic vulcanization. The effects of SR content on crystallization behavior, rheology, dynamic mechanical properties and morphology of the blends were investigated. Morphology characterization shows that the crosslinked spherical SR particles with an average diameter of 2-4 μm form a “network” in the PVDF continuous phase. The dynamic mechanical properties indicate the interface adhesion between PVDF and rubber phase is improved by the dynamic vulcanization. The rheology study shows that with the increase of rubber content the blends pseudoplastic nature is retained, while the viscosity increases, and hence the processability is less good. The incorporation of SR phase promotes the nucleation process of PVDF, leading to increased polymer crystallization rate and crystallization temperature. However, a higher content of SR seems to show a negative effect on the crystallinity of the PVDF component.     

SBR composites reinforced with <Emphasis Type="Italic">N</Emphasis>-isopropyl-<Emphasis Type="Italic">N</Emphasis>′-phenyl-<Emphasis Type="Italic">P</Emphasis>-phenylenediamine-modified clay

SBR compounds including the N-isopropyl-N’-phenyl-p-phenylenediamine-modified clay(organoclay) were prepared.Effects of modified clay and antioxidant(IPPD) contents on mechanical and rheological properties of SBR composites were studied.FTIR results confirmed that the clay was chemically modified by IPPD and changed into an organoclay.X-ray diffraction(XRD) results confirmed the increase in interlayer distance of the clay due to the insertion of IPPD.Rheological and cure characteristics of SBR compounds were determined using RPA(Rubber Process Analyzer) and rheometer.Scorch time and cure time of SBR compounds decreased with introduction of the organoclay.Mechanical properties and heat aging resistance of the SBR composites were improved significantly by incorporation of the organoclay.     

Effects of partial replacement of silicone rubber with flurorubber on properties of dynamically cured poly(vinylidene fluoride)/silicone rubber/flurorubber ternary blends

Blends of poly(vinylidene fluoride) (PVDF), silicone rubber (SR) and flurorubber (FKM) were prepared via peroxide dynamic vulcanization. The effect of FKM loading on the morphology, mechanical properties, crystallization behavior, rheology and dynamic mechanical properties of the PVDF/SR/FKM ternary blends was investigated. A “network” was observed in the PVDF/SR binary blends, which disappeared in the ternary blends, but a core-shell-like structure was formed. The mechanical properties were significantly improved. The Izod impact strength of PVDF/SR/FKM blend with 19 wt% FKM was 18.3 kJ/m², which was 3–4 times higher than the PVDF/SR binary blend. The complex viscosity and storage modulus of the PVDF/SR/FKM blends decreased with increasing FKM content, hence the processability was improved. The increase of FKM content seemed to show a favorable effect on the crystallization of the PVDF component. It promoted the nucleation process of PVDF, leading to increased polymer crystallization rate and higher crystallization temperature. The glass-rubber transition temperature of the PVDF phase moved to a lower temperature.     

Preparation and properties of poly(urethane-imide)s derived from amine-blocked-polyurethane prepolymer and pyromellitic dianhydride

Poly(urethane-imide)s were prepared using amine-blocked-polyurethane (PU) prepolymer and pyromellitic dianhydride. The PU prepolymers were prepared by the reaction of different diols (polypropyleneoxy glycol, polytetramethyleneoxy glycol, polycaprolactonediol and hydroxyl terminated polybutadiene) and different diisocyanates (2,4-tolylene diisocyanate, 1,4-phenelene diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate and 4,4^′-methylenebis(cyclohexyl)isocyanate) and end capped with N-methylaniline. The polymerization was faster with aromatic isocyanates than with aliphatic isocyanates. The effect of imide content on the thermal and mechanical properties was studied. The poly(urethane-imide)s were characterized by FTIR, GPC, TGA and for dynamic and static mechanical properties. Weight average molecular weight (M_w) of the polymers did not vary significantly with change in -NCO/-OH ratio where as number average molecular weight (M_n) increased with increasing -NCO/-OH ratio, correspondingly, the dispersity (PD) decreased. Polymers with higher hard segment content exhibited higher glass transition temperature. The thermal stability of the PU was found to increase significantly by the introduction of imide component.     

An effect of N ion bombardment on the properties of CdTe thin films

E-beam evaporated CdTe thin films were processed with N⁺ ion bombardment as in situ process. The N⁺ ion glow was generated using simple Multipurpose Al probe instead of conventional plasma sources. The prepared films were identified as nano crystalline using XRD analysis. High N⁺ ion fluence helped to grow (3 1 1) oriented CdTe thin films instead of (2 2 0) and (1 1 1). The observed results revealed the effect of N⁺ ion fluence on the structural parameters like lattice parameter, d space value, crystalline size, dislocation density, micro strain etc. The observed optical band gap values lie in between 1.47 and 1.77 eV. The effect of N⁺ ion bombardment on optical properties was also reported. Noticeable change in electrical and surface properties was also observed. The observed value shows the reproducibility as <1% and it is suggested that the N⁺ ion plasma was effectively utilized to modify the structural, optical and surface properties as in situ.     

One-dimensional and two-dimensional coordination polymers constructed from copper(II) nodes and polycarboxylato spacers: Synthesis,crystal structures and magnetic properties

Four new coordination polymers were obtained by employing polycarboxylato spacers and cationic copper(II) complexes as nodes: ^∞₂[Cu₃(trim)₂(NH₃)₆(H₂O)₃] (1); ^∞₁[Cu(tmen)(dhtp)] (2), ^∞₁[Cu(tmen)(hitp)(H₂O)] (3), ^∞₁[Cu(tmen)(nitp)] (4). (H₃trim = trimesic acid, H₂dhtp = 2,5-dihydroxy-terephthalic acid; H₂hitp = 5-hydroxy-isophthalic acid, H₂nitp = 5-nitro-isophthalic acid; tmen = N,N,N′,N′-tetramethyl-ethylenediamine). The crystal structures of the four compounds have been solved. Compound 1 consists of 2D coordination polymers with heart-shaped meshes, while compounds 2–4 contain infinite zigzag chains. The role of the hydrogen bond interactions in sustaining the supramolecular solid-state architectures in compounds 1 and 3 is discussed. The cryomagnetic investigation of compounds 1, 2, and 4 reveals antiferromagnetic interactions between the copper ions.     

Antimicrobial agents as photostabilizers for rigid poly(vinyl chloride)

Some amide derivatives of ethylene glycol‐bis(2‐aminoethylether)‐N,N,N^′,N^′‐tetraacetic acid (EGTA) have been prepared via their coupling with different aniline derivatives: amino, methyl, chloro, and hydroxy aniline. The EGTA amide derivatives were characterized, and their antimicrobial activities were evaluated. These antimicrobial agents have been investigated as photostabilizers for rigid poly(vinyl chloride) (PVC), suspension PVC, with a K value of 70. Their stabilizing efficiencies were evaluated by determining the percentage of weight loss, the intrinsic viscosities, as well as the amount of formed gel of the photodegraded PVC. The extent of discoloration and the change in the mechanical properties of the photodegraded polymer were also evaluated. The applied materials reduced the loss in weight that resulted from HCl evolution during photodegradation. Both viscosity and gel content measurements showed also a decrease in their values during the degradation process. The decrease in the percentage of gel formation upon applying the investigated photostabilizers reflects the lowering in extent of cross‐linking of the polymer, which implies preserving the mechanical properties of PVC. The extent of discoloration was also improved in the presence of the investigated compounds. The results have proved a greater stabilizing efficiencies of the antimicrobial EGTA amide derivatives than that of the phenyl salicylate ultraviolet (UV) absorber, which is commonly used as an industrial stabilizer. A radical mechanism was proposed to account for the stabilizing action of the investigated products. Copyright © 2011 John Wiley & Sons, Ltd.     

Polydisuccinimides: Polyaddition reactions of aliphatic and aromatic diamines to N,N′-bismaleimide

Polyaddition reactions of aliphatic and aromatic diamines to N,N′-bismaleimide and model compounds have been investigated in order to establish some properties of this imide. Glacial acetic acid has a catalytic effect when used as solvent in the preparation of aspartimide compounds. Aromatic diamines show a much smaller reactivity than aliphatic, the former giving polydisuccinimides and the latter polyamides under the same reaction conditions. Addition reactions of N,N′-bismaleimide proceed either by an ionic mechanism in polar solvents or by a homolytic process in solvents precluding ion formation. The thermal stability and the infrared spectra of the new polymers are discussed.