Investigations on the preparation of composite polysaccharide films and micro / nanoparticles for novel applications

chemical Sciences and Technology Division, National Institute for Interdisciplinary Science and Technology, CSIR

Dynamic mechanical analysis of binary and ternary polymer blends based on nylon copolymer/EPDM rubber and EPM grafted maleic anhydride compatibilizer

The dynamic mechanical properties such as storage modulus, loss modulus and damping properties of blends of nylon copolymer (PA6,66) with ethylene propylene diene (EPDM) rubber was investigated with special reference to the effect of blend ratio and compatibilisation over a temperature range –100°C to 150°C at different frequencies. The effect of change in the composition of the polymer blends on tanδ was studied to understand the extent of polymer miscibility and damping characteristics. The loss tangent curve of the blends exhibited two transition peaks, corresponding to the glass transition temperature (Tg) of individual components indicating incompatibility of the blend systems. The morphology of the blends has been examined by using scanning electron microscopy. The Arrhenius relationship was used to calculate the activation energy for the glass transition of the blends. Finally, attempts have been made to compare the experimental data with theoretical models.

Compatibility Studies on Sulphur Cured EPDM/CIIR Blends

The principal objective of this study was to explore the compatibility of a blend of two synthetic elastomers viz., ethylene-propylene-diene rubber (EPDM) and chlorobutyl rubber (CIIR). Various commercial grades of EPDM were blended with a specific grade of CIIR at different proportions. The mechanical properties such as tensile strength, tear strength, ageing resistance, etc. were studied. On the basis of the observed physical properties, two particular grades of EPDM were found to be compatible with CIIR. Differential scanning calorimetry and scanning electron microscopy confirmed the results. Chlorosulphonated polyethylene was added as a compatibilizing agent to overcome the phase separation of the other two incompatible grades of EPDM in blending with CIIR. The results revealed that the addition of compatibilizer greatly improves the compatibility and thereby the properties of the blends.

Thermal Properties of Polytetrafluoroethylene/ Sr2Ce2Ti5O16 Polymer/Ceramic Composites

Polytetrafluoroethylene (PTFE) composites filled with Sr2Ce2Ti5O16 ceramic were prepared by a powder processing technique. The structures and microstructures of the composites were investigated by X-ray diffraction and scanning electron microscopy techniques. Differential scanning calorimetry showed that the ceramic filler had no effect on the melting point of the PTFE. The effect of the Sr2Ce2Ti5O16 ceramic content [0–0.6 volume fraction (vf)] on the thermal conductivity, coefficient of thermal expansion (CTE), specific heat capacity, and thermal diffusivity were investigated. As the vf of the Sr2Ce2Ti5O16 ceramic increased, the thermal conductivity of the specimen increased, and the CTE decreased. The thermal conductivity and thermal expansion of the PTFE/Sr2Ce2Ti5O16 composites were improved to 1.7 W m21 8C21 and 34 ppm/8C, respectively for 0.6 vf of the ceramics. The experimental thermal conductivity and CTE were compared with different theoretical models.

Tuning mesoporous molecular sieve SBA-15 for the immobilization of α-amylase

The present work describes the immobilization of α-amylase over well ordered mesoporous molecular sieve SBA-15 with different pore diameters synthesized by post synthesis treatment (PST) hydrothermally after reaction at 40°C. The materials were characterized by N 2 adsorption–desorption studies, small angle X-ray diffraction, scanning electron microscopy and high resolution transmission electron microscopy. Since α-amylase obtained from Bacillus subtilis has dimensions of 35 × 40 × 70 Å it is expected that the protein have access to the pore of SBA-15 (PST-120°C) with diameter 74 Å. The pore dimension is appropriate to prevent considerable leaching. The rate of adsorption of the enzyme on silica of various pore sizes revealed the influence of morphology, pore diameter, pore volume and pH.

EPDM/CIIR Blends: Compatibility, Morphology and Physical Properties

A detailed study of the blends of ethylene-propylene-diene rubber (EPDM) and chlorobutyl rubber (CIIR) is proposed in this study. These blends may find application in the manufacture of curing diaphragms/curing envelopes for tire curing applications. EPDM possesses better physical properties such as high heat resistance, ozone resistance, cold and moisture resistance, high resistance to permanent defonnation, very good resistance to flex cracking and impact. Because of the low gas and moisture penneability, good weathering resistance and high thermal stability of CIIR, blends of EPDM with CIlR may be attractive, if sufficient mechanical strength can be developed. Although a lot of work has been done on elastomer blends, studies on the blends of EPDM and CIIR rubbers are meagre. Hence in this investigation it is proposed to make a systematic study on the characteristics of EPDM and CIIR rubber blends.The mechanical and physical properties of an elastomer blend depend mainly on the blend compatibility. So in the first part of the study, it is proposed to develop compatible blends of EPDM with CIIR. Various commercial grades of ethylenepropylene- diene rubber are proposed to be blended with a specific grade of chlorobutyl rubber at varying proportions. The extent of compatibility in these blends is proposed to be evaluated based on their mechanical properties such as tensile strength, tear strength and ageing resistance. In addition to the physical property measurements, blend compatibility is also proposed to be studied based on the glass transition behavlour of the blends in relation to the Tg's of the individual components using Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA). The phase morphology of the blends is also proposed to be investigated by Scanning Electron Microscopy (SEM) studies of the tensile fracture surfaces. In the case of incompatible blends, the effect of addition of chlorosulfonated polyethylene as a compatibiliser is also proposed to be investigated.In the second part of the study, the effect of sulphur curing and resin curing on the curing behaviour and the vulcanizate properties of EPDM/CIIR blends are planned to be evaluated. Since the properties of rubber vulcanizates are determined by their network structures, it is proposed to determine the network structure of the vulcanizates by chemical probes so as to correlate it with the mechanical properties.In the third part of the work, the effect of partial precuring of one of the components prior to blending as a possible means of improving the properties of the blend is proposed to be investigated. This procedure may also help to bring down the viscosity mismatch between the constituent e1astomers and provide covulcanization of the blend.The rheological characteristics and processability of the blends are proposed to be investigated in the last part of the study. To explore their possible applications, the air permeability of the blend samples at varying temperatures is proposed to be measured. The thermal diffusivity behaviour of EPDM/CIlR blends is also proposed to be investigated using novel laser technique. The thermal diffusivity of the blends along with the thermal degradation resistance may help to determine whether the blends are suitable for high temperature applications such as in the manufacturing of curing envelope.

Novel adhesive systems based on neoprene-phenolic blends

The aim of the investigation is to develop new high performance adhesive systems based on neoprene-phenolic blends. Initially the effect of addition of all possible ingredients like fillers, adhesion promoters, curing agents and their optimum compositions to neoprene solution is investigated. The phenolic resin used is a copolymer of phenol-cardanolformaldehyde prepared in the laboratory. The optimum ratio between phenol and cardanol that gives the maximum bond strength in metal-metal, rubber-rubber and rubber-metal specimens has been identified. Further the ratio between total phenols and formaldehyde is also optimised. The above adhesive system is further modified by the addition of epoxidized phenolic novolacs. For this purpose, phenolic novolac resins are prepared in different stoichiometric ratios and are subsequently epoxidized. The effectiveness of the adhesive for bonding different metal and rubber substrates is another part of the study. To study the ageing behaviour, different bonded specimens are exposed to high temperature, hot water and salt water and adhesive properties have been evaluated. The synthesized resins have been characterized by FTIR , HNMR spectroscopy. The molecular weights of the resins have been obtained by GPC. Thermogravimetric analysis and differential scanning calorimetry are used to study the thermal properties. The fractured surface analysis is studied by scanning electron microscopy. The study has brought to light the influence of phenol/ formaldehyde stoichiometric ratio, addition of cardanol (a renewable resource), adhesion promoters and suitability of the adhesive for different substrates and the age resistance of adhesive joints among other things.

Linear Low Density Polyethylene-Biodegradability Using Bacteria from Marine Benthic Environment and Photodegradability Using Ultraviolet Light

Various compositions of linear low density polyethylene(LLDPE) containing bio-filler(either starch or dextrin)of various particle sizes were prepared.The mechanical,thermal,FTIR,morphological(SEM),water absorption and melt flow(MFI) studies were carried out.Biodegradability of the compositions were determined using a shake culture flask containing amylase producing bacteria(vibrios),which were isolated from marine benthic environment and by soil burial test. The effect of low quantities of metal oxides and metal stearate as pro-oxidants in LLDPE and in the LLDPE-biofiller compositions was established by exposing the samples to ultraviolet light.The combination of bio-filler and a pro-oxidant improves the degradation of linear low density polyethylene.The maleation of LLDPE improves the compatibility of the c blend components and thepro-oxidants enhance the photodegradability of the compatibilised blends.The responsibility studies on the partially biodegradable LLDPE containing bio-fillers and pro-oxidants suggest that the blends could be repeatedly reprocessed without deterioration in mechanical properties.

Modification of Linear Low Density Polyethylene for Improved Photo and Biodegradation

LLDPE was blended with poly (vinyl alcohol) and mechanical, thermal, spectroscopic properties and biodegradability were investigated. The biodegradability of LLDPE/PVA blends has been studied in two environments, viz. (1) a culture medium containing Vibrio sp. and (2) a soil environment over a period of 15 weeks. Nanoanatase having photo catalytic activity was synthesized by hydrothermal method using titanium-iso-propoxide. The synthesized TiO2 was characterized by X-Ray diffraction (XRD), BET studies, FTIR studies and scanning electron microscopy (SEM). The crystallite size of titania was calculated to be ≈ 6nm from the XRD results and the surface area was found to be about 310m2/g by BET method. SEM shows that nanoanatase particles prepared by this method are spherical in shape. Linear low density polyethylene films containing polyvinyl alcohol and a pro-oxidant (TiO2 or cobalt stearate with or without vegetable oil) were prepared. The films were then subjected to natural weathering and UV exposure followed by biodegradation in culture medium as well as in soil environment. The degradation was monitored by mechanical property measurements, thermal studies, rate of weight loss, FTIR and SEM studies. Higher weight loss, texture change and greater increments in carbonyl index values were observed in samples containing cobalt stearate and vegetable oil. The present study demonstrates that the combination of LLDPE/PVA blends with (I) nanoanatase/vegetable oil and (ii) cobalt stearate/vegetable oil leads to extensive photodegradation. These samples show substantial degradation when subsequent exposure to Vibrio sp. is made. Thus a combined photodegradation and biodegradation process is a promising step towards obtaining a biodegradable grade of LLDPE.

Detection of sandal spike phytoplasma using immunological and molecular techniques

Spike disease in sandal is generally diagnosed by the manifestation of external symptoms. Attempts have been made to detect the diseased plants by determining the length/breadth ratio of leaves (lyengar, 1961) and histochemical tests using Mann's stain (Parthasarathi et al., 1966), Dienes' stain (Ananthapadmanabha et a/., 1973) aniline blue and Hoechst 33258 (Ghosh et a/., 1985, Rangaswamy, 1995). But most of these techniques are insensitive, indirect detection methods leading to misinterpretation of results. Moreover, to identify disease resistant sandal trees, highly sensitive techniques are needed to detect the presence of the pathogen. In sandal forests, several host plants of sandal like Zizyphus oenop/ea (Fig. 1.3) also exhibit the yellows type disease symptoms. Immunological and molecular assays have to be developed to confirm the presence of sandal spike phytoplasma in such hosts. The major objectives of the present work includes:In situ detection of sandal spike phytoplasma by epifluorescence microscopy and scanning electron microscopy.,Purification of sandal spike phytoplasma and production of polyclonal antibodies.,Amino acid and total protein estimation of sandal spike phytoplasma.,Immunological detection of sandal spike phytoplasma., Molecular detection of sandal spike phytoplasma.,Screening for phytoplasma in host plants of spike disease affected sandal using immunological and molecular techniques.

Preparation and characterization of micro and nano fiber reinforced natural rubber composites by latex stage processing

Use of short fibers as reinforcing fillers in rubber composites is on an increasing trend. They are popular due to the possibility of obtaining anisotropic properties, ease of processing and economy. In the preparation of these composites short fibers are incorporated on two roll mixing mills or in internal mixers. This is a high energy intensive time consuming process. This calls for developing less energy intensive and less time consuming processes for incorporation and distribution of short fibers in the rubber matrix. One method for this is to incorporate fibers in the latex stage. The present study is primarily to optimize the preparation of short fiber- natural rubber composite by latex stage compounding and to evaluate the resulting composites in terms of mechanical, dynamic mechanical and thermal properties. A synthetic fiber (Nylon) and a natural fiber (Coir) are used to evaluate the advantages of the processing through latex stage. To extract the full reinforcing potential of the coir fibers the macro fibers are converted to micro fibers through chemical and mechanical means. The thesis is presented in 7 chapters

Template-Assisted Synthesis and Characterization of Passivated Nickel Nanoparticles

Potential applications of nickel nanoparticles demand the synthesis of self-protected nickel nanoparticles by different synthesis techniques. A novel and simple technique for the synthesis of self-protected nickel nanoparticles is realized by the inter-matrix synthesis of nickel nanoparticles by cation exchange reduction in two types of resins. Two different polymer templates namely strongly acidic cation exchange resins and weakly acidic cation exchange resins provided with cation exchange sites which can anchor metal cations by the ion exchange process are used. The nickel ions which are held at the cation exchange sites by ion fixation can be subsequently reduced to metal nanoparticles by using sodium borohydride as the reducing agent. The composites are cycled repeating the loading reduction cycle involved in the synthesis procedure. X-Ray Diffraction, Scanning Electron Microscopy, Transmission Electron microscopy, Energy Dispersive Spectrum, and Inductively Coupled Plasma Analysis are effectively utilized to investigate the different structural characteristics of the nanocomposites. The hysteresis loop parameters namely saturation magnetization and coercivity are measured using Vibrating Sample Magnetometer. The thermomagnetization study is also conducted to evaluate the Curie temperature values of the composites. The effect of cycling on the structural and magnetic characteristics of the two composites are dealt in detail. A comparison between the different characteristics of the two nanocomposites is also provided

Enhanced UV emission from ZnO nanoflowers synthesized by the hydrothermal process

ZnO nanoflowers were synthesized by the hydrothermal process at an optimized growth temperature of 200 ◦C and a growth/reaction time of 3 h. As-prepared ZnO nanoflowers were characterized by x-ray diffraction, scanning electron microscopy, UV–visible and Raman spectroscopy. X-ray diffraction and Raman studies reveal that the as-synthesized flower-like ZnO nanostructures are highly crystalline with a hexagonal wurtzite phase preferentially oriented along the (1 0 1 1) plane. The average length (234–347 nm) and diameter (77–106 nm) of the nanorods constituting the flower-like structure are estimated using scanning electron microscopy studies. The band gap of ZnO nanoflowers is estimated as 3.23 eV, the lowering of band gap is attributed to the flower-like surface morphology and microstructure of ZnO. Room temperature photoluminescence spectrum shows a strong UV emission peak at 392 nm, with a suppressed visible emission related to the defect states, indicating the defect free formation of ZnO nanoflowers that can be potentially used for UV light-emitting devices. The suppressed Raman bands at 541 and 583 cm−1 related to defect states in ZnO confirms that the ZnO nanoflowers here obtained have a reduced presence of defects

Mn2þ-induced room-temperature ferromagnetism and spin-glass behavior in hydrothermally grown Mn-doped ZnO nanorods

The magnetic properties of Mn-doped ZnO (ZnO:Mn) nanorods grown by hydrothermal process at a temperature of 200 8C and a growth time of 3 h have been studied. The samples were characterized by using powder X-ray diffraction with Rietveld refinement, scanning electron microscopy, energy-dispersive X-ray analysis and SQUID magnetometry. Mn (3 wt%) and (5 wt%)-doped ZnO samples exhibit paramagnetic and ferromagnetic behavior, respectively, at room temperature. The spin-glass behavior is observed from the samples with respect to the decrease of temperature. At 10 K, both samples exhibit a hysteresis loop with relatively low coercivity. The room-temperature ferromagnetism in 5 wt% Mn-doped ZnO nanorods is attributed to the increase in the specific area of grain boundaries, interaction between dopant Mn2þ ions substituted at Zn2þ site and the interaction between Mn2þ ions and Zn2þ ions from the ZnO host lattice

Epoxy-modiWed, unsaturated polyester hybrid networks

Hybrid polymer networks (HPNs) based on unsaturated polyester resin (UPR) and epoxy resins were synthesized by reactive blending. The epoxy resins used were epoxidised phenolic novolac (EPN), epoxidised cresol novolac (ECN) and diglycidyl ether of bisphenol A (DGEBA). Epoxy novolacs were prepared by glycidylation of the novolacs using epichlorohydrin. The physical, mechanical, and thermal properties of the cured blends were compared with those of the control resin. Epoxy resins show good miscibility and compatibility with the UPR resin on blending and the co-cured resin showed substantial improvement in the toughness and impact resistance. Considerable enhancement of tensile strength and toughness are noticed at very low loading of EPN. Thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA) and diVerential scanning calorimetry (DSC) were employed to study the thermal properties of the toughened resin. The EPN/ UPR blends showed substantial improvement in thermal stability as evident from TGA and damping data. The fracture behaviour was corroborated by scanning electron microscopy (SEM). The performance of EPN is found to be superior to other epoxy resins