Proceedings of International Polymer Science and Technology Symposium
The “International Symposium on Polymer Science and Technology 2012 in Collaboration with Industries,Institutions and Universities” (IIUPST 2012) is held with the main objective of merging the academia and polymer industry on a common platform to exchange information and novel ideas to enhance research and development. The inauguration ceremony of the symposium was held at the Galle Face Hotel Colombo on the 2 nd of November 2012 amidst a distinguished gathering of guests. We have a strong collaborative team of eminent professionals and experienced specialists with wide-ranging areas of expertise in the field of Polymer Science and Technology. The polymer community in Sri Lanka consists of rubber/plastic based industries, rubber plantation industries and textile/apparel industries which contribute exceedingly to our national economy. We strongly believe that research and development in this community are indispensable in winning over the economic challenges of the country. Having a symposium in collaboration with the academia and industries in Sri Lanka will enhance the partnerships between the industrial sector and government research centers and thus, strengthen our nation’s fiscal framework in an effective way.
Preparation of novel polymerizable diarylethene derivatives and their photochromic polymer films
Two new easily polymerizable dithienylethenes have been synthesized, analyzed and tested in polymerization. 1,2-Bis(5-ethylenyl-2-methylthien-3-yl)cyclopentene (DT1) and 1,2-bis(5-(2-methylprop-2-enoyl)-2-methylthien-3-yl)cyclopentene (DT2) (Figure) were obtained by incorporating polymerizable functional groups (ethyleneyl and methacryloyl) at the 5 and 5’ positions of the thiophene rings in a diarylethene structure. DT1 and DT2 displayed reversible color changes. Initially colorless DT1 and DT2 isomers turned to colored isomers by irradiating, respectively, with UV and visible light and the color disappeared upon removing the radiation source. The colorless open isomer of DT1 shows a maximum absorption at 269 nm which, upon irradiation with UV light, converts to the red colored, closed isomer. The spectral shift upon photoisomerization is about 248 nm and an isosbestic point is observed at 314 nm. The open ring isomer of colorless DT2 (λmax = 273 nm) turns in to yellow with a new peak appears at 373 nm upon irradiation at 300 nm. The isosbestic point of DT2 occurs at 264 nm indicate open-to-closed isomer conversion. Thermal stability, fatigue resistance and polymerizability of each were analyzed. The synthesized dithienylethenes are thermochromic. Irradiated DT1 dithienylethene derivatives were stable for more than one month while irradiated DT2 derivative was only stable for 24 h. Organic photochromes need to be incorporated into a polymer matrix in order to make an efficient, durable optoelectronic device. Both derivatives can be easily incorporated into polymer matrixes either by photo-curing or radical polymerization. Polymeric materials incorporating DT derivatives also undergo reversible color change upon irradiation with UV and visible light, respectively. Photopolymerization yields a polymer film containing the closed dithienylethene moiety that can be converted to its open form following irradiation with visible light. Free radical polymerization, on the other hand, results in a polymer with the dithienylethene in the open isomer, which can be converted to its closed isomer upon irradiation with UV light. The photochromic films were applied in an erasable, recording photonic mode. Keywords: Dithienylethenes / Photochromic / Thermal stability / Fatigue resistance Acknowledgement: K. M. T. D. Gunasekara is thankful to the McMaster Endowment for providing a fellowship.
Preparation and characterization of α-Chitin nanofibers from crab shells of Portunus pelagicus (blue swimmer crab)
Chitin, the second most abundant biopolymer in the world after cellulose is found in a larger number of invertebrate species such as crustaceans and insects and in cell walls of fungi species. However chitin is primarily extracted from exoskeletons of crustaceans such as prawns, shrimps and crabs. Chemically, chitin is a linear amino-polysaccharide known to be made of 2-acetamido-2-deoxy-β-D- glucopyranose through a β(1→ 4) linked structure. The main functionality of chitin in most biological systems is to provide structural rigidity and strength. In crab shells however, a very complex formation of chitin nanofibers, called Bouligand structure, can be observed. This structure follows a twisted plywood like pattern providing additional stiffness and hardness to the shell. The purpose of this work is to extract chitin nanofibers from crab shells of Portunus pelagicus in its elementary scale. During the course of study the crab shell structure was examined using Scanning Electron Microscopy (SEM) imaging. This has confirmed that chitin exists in nanofiber form having diameters in the size range of 3-5 nm in the structure. These nanofibers arrange themselves into larger bundles having 60 – 70 nm in diameter. Unlike in conventional chitin extraction procedures where chitin nanofibers collapse to form a matrix where separation of nanofibers to individual level is impossible, we have used an ultrasound assisted procedure to achieve complete fibrillation of chitin nanofibers. Surface morphology of prepared nanofibers was evaluated using Atomic Force Microscopy (AFM) and SEM. Results suggested that almost all the nanofibers prepared, were completely fibrillated and well dispersed. Crystallinity of the nanofibers was evaluated using X-Ray Diffraction (XRD) and found to follow the α-chitin form and the crystalline nature has not been disturbed during the process. The degree of deacatylation was calculated using Fourier Transform Infar-Red spectroscopy (FTIR) and the thermal character of prepared nanofibers was evaluated using Thermo Gravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). The analysis confirmed that prepared nanofibers had good purity with degree of deacetylation less than 15%. Key words: Chitin / Nanofibers / Extraction / Fibrillation
Evaluation of four sacrificial anti-graffiti polymers on a highly porous stone substrate
Anti-graffiti protection is becoming a common practice in many urban areas, because of increasing danger to buildings and monuments. The main aim of the present study was to evaluate the effectiveness of four commercially available polymeric materials on a very porous stone substrate against graffiti. Physical and chemical properties of the polymers were studied in order to select a class of products able to protect the surface from soiling and to reduce the impact of graffiti on the stone. Experiments were performed on specimens of a very porous bio-calcarenite (Lecce stone, LS), treated with microcrystalline wax (Bresciani, Italy), an emulsion of paraffin polymers (Art Shield-1, C.T.S., Italy), a fluoroelastomer in organic solvent (Fluoline HY, C.T.S.) and a fluoroelastomer in water emulsion (Tecnoflon TN Latex, Solvay Solexis, Italy). Surface properties of treated specimens were evaluated by performing chromatic and gloss variation measurements, optical microscope analysis, water capillary absorption and water vapour permeability tests. In order to examine the anti-graffiti behaviour, treated samples were soiled by a permanent marker and the surface properties studied again after the cleaning. Colour changes were measured by determining the L*, a*, and b* coordinates of the CIELAB space. The overall chromatic changes (expressed as ΔE*) induced by treatments correspond to colour variations that cannot be detected by naked eye (ΔE* < 5), except for microcrystalline wax, which caused a higher variation (Figure). The most considerable gloss variations were observed on specimens treated with Latex TN and Art Shield-1. Water capillary absorption data indicated that water repellent behaviour of Latex TN was higher than the other polymers. The shielding effect exhibited by the other considered polymers was efficient only in the first few hours of contact with water and then it progressively decreased with increasing time. Water vapour permeability test indicated a considerable reduction of the vapour transmission rate only in the case of Latex TN. It should be noted that a low rate of vapour diffusion represents a drawback for surface treatments of stone. The anti-graffiti effectiveness was evaluated by measuring colour changes on specimens after the staining/cleaning process. Variations of chromatic coordinates observed on the “cleaned” stones can be ascribed to traces of residual ink and directly correlated to the efficiency of anti-graffiti action. After cleaning of specimens treated with microcrystalline wax or Art-shield-1 very high ∆E* values (≥ 30) were obtained, indicating a poor protecting action of these products against graffiti. Fluorinated polymers exhibited more satisfactory anti-graffiti performance. In fact, after removing ink stains, ∆E* values determined on stone surface were 3 and 10 for Latex TN and Fluoline HY, respectively.
Studies on the kinetics of epoxidation of soybean oil using synthetic cationic exchange resin
Epoxides of all kinds of plant oils are well known commercially since they can undergo many important reactions. Epoxidation of long chain olefins, and unsaturated fatty acid derivatives such as soybean oil and other plant oils have been carried out on an industrial scale. Nowadays, one of the most important epoxidized vegetable oils is the epoxidized soybean oil (ESO). Fatty epoxides are used directly as plasticizers that are compatible with polyvinyl chloride (PVC) and as stabilizers for PVC resins to improve flexibility, elasticity, and toughness. It also imparts stability of polymer towards heat and UV radiation. As the demands of energy increase and fossil fuel reserves are limited, there has been a growing interest in the utilization of renewable resources as an alternative to petroleum based polymers. Consequently, much attention has been focused on the development of polymeric materials from vegetable oils as a sustainable resource. Therefore, there is a necessity of a comprehensive method of epoxidation, which is easy, simple and cost effective, if epoxidised vegetable oils are to be employed in industrial applications as such. In this study an attempt was made to ascertain an unfailing experimental procedure, which is economically viable for the enpoxidation of vegetable oils for industrial uses. The kinetics of epoxidation of soybean oil (SBO) by peroxyacetic acid (PAA) in the presence of synthetic cationic exchange resin (sulfonated tannin- phenol-formaldehyde resin) as catalyst were investigated at 45 oC, 50 oC, 60 oC and 70 oC by determining oxirane ring content using a titrimetric method. Epoxidation with higher conversion of unsaturated carbon and lower oxirane cleavage could be attained by the in situ technique. The rate constant for epoxidation of SBO was found to be of the order of 10-6 mol-1s-1 and activation energy of epoxidation of 33.62 kJmol-1. The enthalpy, entropy and free energy activation were 22.29 kJmol-1, -273.53 Jmol-1K-1 and -68.79 kJmol-1, respectively. The kinetic and thermodynamic parameters of epoxidation obtained from this study indicate that an increase in the process temperature would increase the rate of epoxide formation.
Thermoset plastic waste from garment button industry as a novel solid state curing agent for epoxy resin system
Garment button industry uses unsaturated polyester based on ethylene glycol and maleic acid to produce thermoset plastic sheets using styrene (31-34 w/w%) as a cross-linking agent. Buttons are produced by casting process and remaining part of the sheet becomes an inherent waste. This research study evaluated the curing behaviour of the powdered thermoset polyester waste (PTPW) of garment button industry as an alternative for amine hardener in epoxy resin systems. Particle size distribution was analysed using the standard sieve analysis method. It indicated that majority (83 w/w%) of the particles were in the range of 125 – 500 µm. Set-to-touch drying time of the epoxy resin system was significantly improved when PTPW was blended with amine hardener. The fastest drying was observed with 30-70% of powdered waste in the blend of amine hardener and PTPW. When an amine molecule reacts with an epoxy ring, it combines to one end of the epoxy resin molecule. Since PTPW particle has more than one reactive and accessible COOH and OH group, each particle can chemically combine with a number of epoxy rings to initiate the cross-linking process. However the effect on set to touch drying time was marginal with the increase of PTPW above 70% and may be due to the initiation of ring opening reactions of epoxy resin with carboxylic groups and hydroxyl groups. PTPW was kept overnight in alkali medium to break the ester links and was acidified with sulphuric acid to generate –COOH and –OH groups. Hydrolysed powder was thoroughly washed to remove sulphuric residues and dried at 105 °C. FTIR spectra of PTPW before and after the hydrolysis reaction indicated the presence of hydrogen-bonded O-H stretching after hydrolysis. Matrix of PTPW particle is hydrophobic in nature since the chains are cross-linked by styrene units. The –COOH and –OH groups which are formed in the hydrolysis tend to form hydrogen-bonds with each other within the matrix itself. Set-to-touch drying characteristics of PTPW and hydrolysed PTPW were very similar to amine hardener when used in the epoxy resin system. When hydrolysed PTPW was blended in proportion with amine hardener, no significant improvement of set to touch drying time was observed. Even though the hydrolysis generated more hydroxyl groups and carboxyl groups within the matrix of particles, number of freely accessible carboxylic and hydroxyl groups without steric hindrance to the epoxy ring structure may not be significant. Therefore the presence of excess number of functional groups per particle is not an advantage by means of drying characteristics. Keywords : Epoxy resin system / Plastic waste / Garment button industry / Hardener / Epoxy grout Acknowledgement : T and S Buttons Lanka (Pvt) Ltd provided a sample of waste in powder form.
Hydrodynamically and mechanically assisted wet spinning of elastomeric polyurethane filaments
Elastomeric fibers have gained huge interest from material scientists and engineers due to their many potential applications in textiles, composites, smart materials etc. Among the many polymers used in preparation of elastomeric fibers and filaments, polyurethane remains as a very popular choice because of its versatility as a polymer and relative ease of tuning the material properties according to the requirement. Elastomeric polyurethane fibers can be spun using wet, dry and melt spinning processes. However spinning of polyurethane filaments requires fairly expensive, sophisticated equipments that usually have minimum processing capacity in the scale of kilograms. These difficulties have posed problems in carrying out polyurethane fiber related work in typical research labs. In this paper we report a simple method to spin elastomeric polyurethane and polyurethane composite filaments using wet spinning method. The process starts by preparation of polyurethane in solvent or dissolving polyurethane in solvent media. Then the solvent is extruded to a rotating water bath using a hypodermic needle where simultaneous coagulation and drawing occurs. Drawing is induced by hybrid hydrodynamic shear stress and rotation induced tension of the winder. Drawing ratio of the spun fibers was primarily changed by varying the rpm of the winding roller and the rotating water bath. Draw ratios in the range of 2 – 5 could be conveniently achieved by changing the rpm from 5 to 20. To explain the formation of spun filaments, analytical model and relevant physical parameters are employed that encompasses combined hydrodynamic phenomena of polymer drawing and mechanical drawing. Morphology and the cross section of the spun filaments were evaluated by using Scanning Electron Microscopy (SEM) and filament evenness was assessed using optical microscopy. Surface morphology of the yarns was irregular with number of voids formed due to the rapid diffusion of polymer solvent to coagulating media. At higher draw ratios, periodical variations of the filament cross section occur due to instability of spun polymer. Mechanical properties of spun fibers were evaluated using tensile testing instrument and Dynamic Mechanical Analysis (DMA). Effect of drawing on molecular structure was probed by using both Differential Scanning Calorimeter (DSC) and Fourier Transform Infrared Spectrophotometer. Especially, increase of polymer crystallinity due to drawing could be confirmed by shifting of Tg to higher temperature from -14.36 °C in undrawn polymer to -6.30 °C in drawn filament. It was concluded that the processing feature enables a flexible and facile spinning method to prepare elastomeric polyurethane filaments and can expand the potential applications through research due to ease of producing spun fibers in small quantities.
Modification of shellac varnish by nanoparticles and a perfluoropolyether based polymer
Shellac has been widely used as a protective material for wooden furniture and musical instruments, due to its remarkable properties such as ease of application, high adhesion to the wood surface and protective properties along with its nonpoisonous nature. However, shellac varnishes have also some limitations such as softness of the coating, photodegradation, and sensitivity to alcoholic solvents and to pH variations. In the present study, de-waxed natural shellac (food quality shellac from Kremer-Pigmente) was selected and modified by introducing different inorganic nanoparticles as well as a fluorinated polymer. Silicates nanoparticles were added with the aim of improving the film hardness, while ZnO nanoparticles were expected to reduce photodegradation of the shellac matrix and finally, fluorinated polymer was considered with the aim of increasing chemical resistance and water repellent character of the resulting material. Four different shellac materials were prepared for these purposes by dispersing nanoparticles (silica, montmorillonite, zinc oxide) and perfluoropolyether in alcoholic solutions of shellac. Different experimental analyses were performed on both modified shellac films and maple wood specimens treated by brushing. Characteristics of modified shellac materials were investigated by performing hardness test, contact angle measurements, evaluation of chromatic variation after UV ageing, solubility and alkali resistance tests. SEM-EDS analyses were also carried out on films and treated wood specimens. Quality and thickness of the coating are important parameters when products are developed for real case applications. Both native shellac and modified shellac treatments on wood specimens provided good quality coatings whose thickness was very close to real applications (about 25 µm, see Figure 1). Hardness measurements performed by international standard test indicated that the presence of silica or montmorillonite nanoparticles in shellac improves the hardness of the resulting coating. In addition, SiO2-shellac applied on wood specimens afforded an improvement of hydrophobic properties (see Figure 2), while Montmorillonite-shellac increased the base resistance property with respect to the native shellac. ZnO-shellac treatment preserved almost unaltered the chromatic properties (L*, a* and b* coordinates of the CIELAB space) with respect to native shellac, even after UV ageing (750 h). Shellac modified by perfluoropolyether showed an improvement of hydrophobic behaviour and photo-stability after artificial ageing. Acknowledgement: The authors would like to acknowledge Dr. Claudio Canevari (Civica Scuola di Liuteria, Milan, Italy) for supplying different shellac batches, wood samples and also kind guidance for the research work.
Nano titanium dioxide embedded nano fibers spun from electro spinning technology to produce stain removal and UV blocking nano fibers
Titanium dioxide nano particle possess photo catalytic, chemical resistance and has the ability of blocking UV light. Reinforcing TiO2 nano particles to nano fibers will give rise to specific properties such as UV blocking, stain removal and antibacterial properties. Electro spinning technology has the ability to produce nano fiber composites containing titanium dioxide nano particles which can be used to produce nonwoven fabrics or yarns with properties of UV blocking and stain removal. This nano scale modification to the composite will enhance the performance of the end product. Fabrics or nonwovens developed from nano fibers which contain the anti UV, self-cleaning and antibacterial properties are more durable and efficient than fabrics coated with conventional finishes. During this research study a Nano fiber/TiO2 composite was prepared by electro spinning a PAN/TiO2 polymer (PAN with an average molecular weight of 10000 and anatase form of TiO2 with an average particle size of 50-100 nm) solution in N,N’-dimethyl formamide (DMF), where all the chemicals and materials were from Sigma Aldrich, USA. Electro spinning allows forming a fiber composite with an aspect ratio in the range of 1000 and a high molecular orientation to the fiber. Scanning Electron Microscope (SEM) studies showed that the average diameter of the electro spun PAN/TiO2 nano composite fibers was in the range of 250-300 nm with a homogenous diameter and revealed the presence of nano titanium dioxide particles embedded inside the nano fiber with an average particle size of 100 nm. UV-VIS spectroscopic studies showed the prepared nano composite can absorb UV light in the range of 200-350 nm. A model experiment showed the prepared nano composite can block the UV light compared to PAN nano fibers by 76%. Stain removal properties of the polymer nano composite were analyzed using the color reduction of an organic stain (Bromothymol Blue) under the sunlight. After 3 hours of sunlight exposure the color reduction was 84% present compared to color reduction of PAN nano fibers under same conditions of only 4%.
An investigation of anionic conductivity of the composite polymer electrolyte based on PEO and Pr4N+I- salt with the filler TiO2
Polymer Electrolytes (PEs) have been studied to use in many devices such as lithium rechargeable batteries, fuel cells, electrochromic devices, etc. Most of the previous research work has been carried out to study the cation conductivity of PEs and their conductivity enhancement with the addition of various fillers. There are not many reports on studying the effect of filler on anionic conductivity in PEs. In this study, the anion conductivity was investigated using the anion conducting PE with tetrapropylammonium iodide (Pr4N+I-) as the salt, polyethylene oxide (PEO) as the polymer and titanium dioxide (TiO2) as the filler. The solvent casting method was used to prepare PE samples, (PEO)mPr4N+I- (m = 5, 10, 20, 30, 40, 50, 60, 80 and 90), where m:1 is the O:I (oxygen:iodine) ratio of the samples. The solvent casting method yielded visually homogeneous composite PE films with average thickness of 100 – 400 μm. Estimated conductivities of the filler free samples were in the order of 10-9 S cm-1 at room temperature and relatively high anionic conductivity was observed for the samples (PEO)60Pr4N+I- and (PEO)50Pr4N+I-. The filler was added as a weight percent (5%, 10%, 15%, 20% and 30%) to the 60:1 and 50:1 samples. The thermal studies were carried out to investigate the melting enthalpies of the filler free and filler added samples using the Pyris 1 differential scanning calorimeter (DSC). Unlike the cation conducting PEs, here the anionic conductivity did not increase with the addition of the filler. However according to the conductivity and DSC results it can be concluded that the amorphous nature of the samples was increased. Optical micrographs confirmed this nature showing a reduction in size of the spherulites with addition of the filler.
Enhancement of photocatalytic activity of nano TiO2 by doping with nitrogen and its stain removal properties
Nano Titanium dioxide is widely studied as a photocatalyst under UV light. But its wide band gap and recombination of electrons and holes, reduce the photocatalytic efficiency. Wide band gap limits the photocatalytic activity to ultra violet radiation. There are metal-TiO2 core shell nano structures which reduces the electron hole recombination. In order to utilize the wider range from solar radiation nano TiO2 can be doped with metal or non-metal elements. Transition metal doping of TiO2 has strongly localized states within the band gap which causes thermal instabilities and formation of carrier recombination centers. Therefore doping TiO2 with non metal elements has been proved as a better structure to enhance the photocatalytic efficiency. When introducing Nitrogen to nano TiO2, oxygen atoms are substituted with nitrogen atoms. Hybridization of N 2p states with the O 2p state derived valence band is supposed to achieve a band gap narrowing. Therefore it is possible for the N-doped TiO2 to absorb energy from visible light and act as a photocatalyst. In this paper N-doped TiO2 was synthesized by addition of ammonia water. Synthesized particles were characterized with X-ray diffraction techniques and it was observed that obtained TiO2 was in anatase form. UV-visible spectra showed nano TiO2 absorbs in the UV region between 240 nm to 350 nm range and the absorption of N- TiO2 has been shifted to the visible region (340 nm to 530 nm). Photocatalytic action of N- TiO2 was compared with anatase nano TiO2 (bought commercially from Sigma-aldrich) by analyzing the colour reduction of Methylene blue under sunlight. UV-Vis analysis of this system proved that the photocatalytic activity of N-TiO2 is greater than nano TiO2 under sunlight. Also UV-Visible analysis showed that N - TiO2 in dispersion form has higher stain removal properties than the nano TiO2 dispersion (bought commercially from Sigma-Aldrich) for stained fabrics under sunlight.
Natural rubber/clay nanocomposites: effect of organic modifier of clay on cure characteristics and mechanical properties
Over the recent past, nanomaterials have emerged as potential reinforcing and functional materials for rubber composites. Montmorillonite (MMT) clay, which belongs to the 2:1 smectites family, is the widely investigated nanomaterial for improving reinforcement of rubber composites. Improved reinforcement is achieved with a lower concentration of these clay minerals compared to that of traditional fillers such as carbon black and silica. However, hydrophilic clay needs to convert into organophilic since clay minerals are not easily intercalated when they are combined with conventional non-polar rubber such as natural rubber (NR). In general, MMT clay is organically modified with alkyl ammonium cation (known as organic modifier) to make them more compatible with non-polar polymeric materials. This research study investigated the effect of different types of alkyl ammonium modifiers on cure characteristics and mechanical properties of natural rubber/clay nanocomposites in view of developing a suitable curing system for the nanocomposite. A natural rubber (NR)-clay nanocomposite (NRCN) was prepared by melt compounding of NR with organically modified montmorillonite (OMMT) clay and other compounding chemicals using a laboratory scale internal mixer. Vulcanization kinetics of the NRCN was evaluated in comparison to NR gum compound, with a moving die rheometer (MDR). Processing safety and optimum cure time showed a marked reduction whilst indicating a significant effect on thermo-oxidative degradation as measured by reversion time when clay was modified with different modifiers, in comparison to unmodified clay, used in the rubber compound formulations. The results of cure characteristics have been interpreted with reference to the types of organic modifier and degree of exfoliation of clay. A vulcanization system with improved processing safety (delayed onset curing) and a reduced cure rate for NRCN was developed by incorporating a pre-vulcanization inhibitor. Mechanical properties of NRCN vulcanizates showed a significant reinforcement; especially stiffness and strength characteristics, when NR was melt compounded with organically modified clay compared to that of unmodified montmorillonite clay. However, the highest reinforcement was achieved with montmorillonite clay modified with quaternary aliphatic ammonium ion containing hydrogenated tallow.
Investigation of mordanting activity of the flower of Nyctanthes arbor tristis L.(Sepalika) on natural dyed fabrics
The fossil fuel era led to the development of the use of textiles based on petrochemicals. This in turn required different synthetic chemicals as dyeing and fixing agents to enhance consumer appeal of these textiles. Today this is a global industry of significance. However, from a national perspective becoming greener by using biopolymers and natural dyes may at this stage of transition prove to be quite beneficial. This study explores such an opportunity. Sepalika flowers (Nyctanthes arbor-tristis) (Harshingar, Parijat) belongs to the family Oleaceae. The flower has white petals with an orange calyx. Nyctanthes stems have been found to be a rich source of antioxidant. The aqueous extracts of the flower, calyx and petals were evaluated for cotton dyeing and found to be excellent fixing properties of dyes on fabric. This signifies that the main colour yielding part is in the orange colored calyx of the flower. In this research, attempts have been made to carry out an innovative study with the Nyctanthes flower as a part of an exploration for a cheap natural dye mordanting source. The natural dyed fabrics with Rambutan Fruit skin (Nephelium Lappacium), turmeric (Curcuma Domestica Valet), tea waste (Camelia sinensis), big onion (Alium cepa) and jak (Artocarpus heterophylus) were investigated for their fastness properties. These fastness properties showed excellent to moderate results. In this study, Sepalika (Nyctanthes arbor-tristis) flower extract was used to improve these fastness properties to an acceptable level and to obtain different colour shades. These dyed fabrics were investigated with pre-mordanting, simultaneous mordanting and post mordanting conditions at optimum dyeing parameters. The fastness properties of naturally dyed cotton fabrics under conventional conditions with sepalika as natural mordanting agents were found under three different mordanting conditions, namely pre mordanting, simultaneous mordanting and post mordanting. Fastness values in the range of 2-4 for samples without mordanting agent were improved to be 4 with the mordanting agent. The results of this research showed that the naturally dyed cotton fabrics treated under conventional conditions without mordanting showed very poor wash fastness, perspiration fastness, Rub fastness and Light fastness properties. But the treatment with aqueous extracts of fresh and old Sepalika flowers enhance the fastness properties of naturally dyed fabrics in three different mordanting conditions with the conventional optimum dyeing parameters. Thus, it can be concluded that the extract of (Nyctanthes arbor-tristis) flowers are well suited as bio mordants for naturally dyed cotton textile substrates to enhance the fastness properties of dyed fabrics. These excellent fastness properties revealed that how natural fibres or polymers (cellulose) are bound together with natural mordants (Nyctanthes arbor-tristis) to enhance fastness properties of dyed which reflect the high quality of dyed textile fabrics.
Improvement of cure characteristics and physical properties of EPDM by incorporating skim rubber
Ethylene-propylene-diene rubber (EPDM) consisting of ethylene, propylene and an unsaturated diene is one of the synthetic rubbers for which the demand is rising fast. Owing to its non-polar and saturated backbone structure, EPDM exhibits good resistance to heat, oxidation and to polar solvents. They are good insulators for electricity as well. Such properties have extended its application to rubber components used in automotive industry, building and construction industry and in wire and cable industries. It is reported that modification of polyisoprene with a small amount of petroleum-processing products containing constituents similar to those of the albuminous fragments in NR will change the curing characteristics and physical properties of synthetic polyisoprene to the level of NR. Furthermore, skim rubber is used for increasing the rate of vulcanization of SBR due to the presence of higher amounts of non-rubber ingredients in them, which are capable of acting as a co-accelerator and an activator for vulcanization. This study clearly shows that ingredients such as decomposed products of proteins and natural fatty acids present in skim rubber function as co-activators for the vulcanization of EPDM. In this experiment the two accelerator systems namely tetramethylthiurandisulfide (TMTD)/2-mercaptobenzothiozole (MBT) and TMTD/N-tert-butyl-2-benzothiazylsulfenamide (TBBS) were used to cure EPDM compounds incorporated with varying amounts of skim rubber, ranging from 5 phr to 15 phr as an additive in the formulation. The improvement of cure charateristics in the presence of skim rubber as an additive was studied using Oscillating Die Rheometer, in the presence of both accelerator systems. The significant improvement of optimum cure time was observed when the skim rubber quantity was gradually increased in the formulation. However scorch time reduced while increasing the quantity of skim rubber. Therefore, it can be concluded that the non-rubber ingredients present in skim rubber can act as co-activators for the vulcanization of EPDM. These co-activators function by a mechanism similar to the mechanism of action of stearic acid in conventional vulcanization systems containing zinc oxide. Mechanical properties such as tensile strength, 100% and 300% modulus, hardness and rebound resilience were studied for the prepared compounds. It can be concluded that the optimum amount of skim rubber needed to be incorporated for the improvement of cure characteristics and mechanical properties of EPDM is around 5 phr. Results obtained further revealed that the optimized action of these co-activators present in skim rubber is achievable with the TMTD/TBBS accelerator system than with the TMTD/MBT accelerator system.
Surface modification of silica with a hydrophilic polymer and its influence on reinforcement of natural rubber latex
Surface modification of silica particles by means of macromolecules is a novel technology and surface modified particles are used in diverse applications; amongst them reinforcement of polymer materials is distinguished. However, reinforcement of natural rubber latex (NRL) is still in research stage. In the present study precipitated silica (Ultrasil VN3) is modified with a hydrophilic polymer of which the hydrophilic groups interact with surface bound hydroxyl groups of silica and then the modified silica is used to reinforce NRL. The hydrophilic polymer was synthesized in the laboratory by solution polymerisation technique. Viscosity average molecular weight of the polymer was determined by using Ubbelohde viscometer. Surface modification of precipitated silica particles was carried out with the synthesised polymer separately in two mediums; aqueous and non aqueous. FTIR spectroscopy of the treated silica was performed to confirm the surface modification. Aqueous dispersions of unmodified/modified silica were prepared prior to compounding and the colloidal stability of the dispersions was observed at different pH levels. The dispersions at neutral pH were incorporated in different loadings namely 5, 10, 15 and 20 phr, to un-compounded and compounded NRL and thin latex films from them were produced by casting. The distribution of silica particles in rubber matrix was examined through microstructural studies and contribution of surface modification towards enhancement of mechanical properties was investigated by measuring tensile and tear properties of unmodified (UM) and modified filler added NRL cast films. Optimum stability of the aqueous dispersions of modified silica was conveyed at pH close to seven. Uniform distribution of modified silica particles within rubber matrix was seen in films cast from modified silica incorporated NRL whereas a settled layer of filler was seen in UM filler added films. Influence of surface modification upon the reinforcement of NRL was confirmed by comparing the values of tensile and tear strengths of UM and modified filler added vulcanized films. Tear strength of all the films first increased, passed a maximum and then decreased with the increase of filler loadings. The maximum values of both modified filler added films were nearly 50% higher than that of UM filler in the range of 5-10 phr of filler loadings. The tensile strength of modified filler added films also showed a maximum at 5 phr of filler addition whilst that of UM filler added films was slightly increased with the concentration of filler. However, the modified filler added films showed nearly 35% increase at 5 phr compared that with the highest value of UM filler added films at 20 phr. It is suggested that uniform distribution of filler particles and the improvement in mechanical properties envisage the better compatibility of modified silica particles with NRL via interfacial interactions and enhanced reinforcement.
Banana fibre filled natural rubber compounds: the effect of filler loading and the coupling agent
Banana plantation generates a huge volume of fibres as residues. The use of natural fibres as fillers in the rubber industry is a new trend. This is especially due to their availability, low cost and environmental friendliness. Of the commonly available natural fibres, banana fibre contains the highest cellulose content of 60-65%. Banana fibre has been incorporated into phenol formaldehyde and polyester resins as a reinforcing material. However, the use of banana fibre in dry rubber formulations is novel. The banana fibre can also be modified physically or chemically to enhance the properties of the rubber products. The objective of the present study is to investigate the effect of fibre loading on rheological properties and the physico-mechanical properties of a dry rubber compounds. In this study, banana fibres were extracted using a mechanical retting method, and were ground using a domestic grinder to prepare fibres in the size range 0.01 – 1.2 mm. The fibres were characterized and extracted fibres were examined under optical microscope. The ground fibres were incorporated into a natural rubber compound as a filler. Two series of filled natural rubber compounds were prepared by varying the fibre loading from 0 to 50 phr at 10 phr intervals; one with banana fibre alone and the other in the presence of a coupling agent (phenol formaldehyde and hexamethylene tetra amine), commonly used to enhance compatibility of natural rubber and biofibres. Cure characteristics, and physico-mechanical properties of the vulcanizates, were investigated according to ISO and BS standards. The properties of the banana fibre filled compounds were compared with the carbon black filled compounds. Cure time decreased gradually with banana fibre loading when banana fibre alone was incorporated into the rubber compound. However, the variation of cure time for all compounds was low and lie within the range of 4 to 5 min. Hardness increased with the banana fibre loading, while tensile properties such as tensile strength and elongation at break, and tear strength decreased. The property variations showed that the banana fibre alone behaves as a diluent filler. With incorporation of the coupling agent tensile strength elongation at break and tear strength improved for all banana fibre loadings. Tensile strength increase is limited to 25% maximum, but elongation at break increased by 200% at 50 phr banana fibre loading. This property enhancement suggested banana fibre with the coupling agent is a reinforcing filler to natural rubber.
Evaluation of the suitability of local dolomite as a replacement for calcite in solid tyre manufacture
The mineral calcite is currently used in a wide range of industries and the main use of calcite powder in Sri Lanka is as a non-reinforcing filler in the manufacture of rubber products. The mineral dolomite is more abundantly found in Sri Lanka than calcite and it consists of a mixture of calcium and magnesium carbonates. Dolomite is very similar to calcite, but harder, denser and slightly more acid resistant. The main aim of this study was to evaluate the suitability of dolomite as a replacement for calcite in solid tyre manufacture. A series of 90:10 natural rubber (NR)/polybutadiene rubber (BR) blend compounds was prepared according to a middle layer, solid tyre formulation by varying the calcite to dolomite ratio at 10 phr intervals. Total filler loading was kept constant at 70 phr. Cure characteristics and physico-mechanical properties of all eight blend compounds were evaluated and compared. The NR/BR blend compound containing 100% dolomite was comparable to the blend compound containing 100% calcite in terms of hardness, modulus at 300% elongation, tensile strength, abrasion weight loss, resilience, compression set and resistance to flex-cracking. The blend compound containing 100% dolomite exhibited a higher scorch safety and lower cure time in comparison to that containing 100% calcite, which are advantages during the moulding operation. However, maximum torque and minimum torque of the blend compound prepared with 100% dolomite were higher than those of the blend compound prepared with 100% calcite. The NR/BR blend compound with 10:60 calcite to dolomite ratio is the best among the blend compounds containing both calcite and dolomite in terms of physico-mechanical properties. Further, the cure characteristics and most of the physico-mechanical properties of the 100% calcite as well as 100% dolomite containing blend compounds were in accordance with the requirements of a middle layer, solid tyre compound. Results in overall indicated that abundantly found dolomite would be a suitable replacement for commonly used calcite in solid tyre manufacture.
Effect of blend composition on physicochemical properties of natural rubber/linear low density polyethylene blend
Blending of polymers can create new materials with a broad spectrum of physicochemical properties and therefore can be used for a wide range of applications. The aim of this study was to investigate the effect of blend composition on physicochemical properties of blends, prepared from natural rubber (NR) and linear low density polyethylene (LLDPE). In this study, a series of blends was formulated varying NR to LLDPE weight ratio, from 100:0 to 20:80, at intervals of 10 w/w% of each. The blends were prepared with and without diallyl malateas as the compatibilizing agent. The blends were prepared using a Brabender Plasticorder by melt mixing at a temperature of 160 ˚C, and at a rotor speed of 60 rpm. Dicumyl peroxide was used as the vulcanizing agent, and vulcanizates were prepared using a hydraulic press operated at a temperature of 150 ˚C. The morphology of the blends was studied by means of a reflected light microscope. Swelling properties of the blends were studied by equilibrium swelling method for 7 days at room temperature using toluene and xylene as solvents. Physical and chemical properties were determined according to ASTM standards. Tear strength and modulus at 300% elongation of NR/LLDPE blends at every composition were greater than those of NR containing compound prepared without LLDPE. When tensile properties of the blends are concerned, they decreased with increase in LLDPE loading. However, the blends with LLDPE loading from 10 w/w% up to 40 w/w% showed higher tensile properties than those of NR compound. Hardness of the blends increased with increase in LLDPE loading. The reactive blends prepared with the compatibilizer showed improved physical properties compared to simple blends, prepared without the compatibilizer. Solvent resistance increased with increase in LLDPE loading, and further, the resistance was greater for the compatibilized blends at each composition. The lowest solvent resistance showed with NR. The microscopic image of a simple NR/LLDPE blend, at a specific blend composition, illustrated relatively large agglomerants of LLDPE phase and void at the interface. Reactive NR/LLDPE blend at the same composition illustrated small LLDPE agglomerants uniformly distributed with NR phase. Blends with different properties required for different applications could be obtained by varying the blend composition. The enhanced properties of the reactive blends prepared with diallyl malateas suggest its activity as a good compatibilizer for NR/LLDPE blends.
Microbial activity in natural rubber latex with currently existing preservative systems
Natural rubber latex is sterile within the tree and destabilizes within a few hours after tapping due to heavy microbial contamination. The main sources of contamination are the tree laces, tapping panel barks and cup which receives the latex. The work described is a systematic study on the behavior of microflora in Hevea latex with different preservative systems in order to investigate the reasons for latex quality deterioration even after the preservation with currently used preservative systems. Observations were made on microbes present in natural rubber (NR) latex without adding any preservatives, latex preserved with LATZ (low ammonia, TMTD/ZnO and latex preserved with high ammonia (0.7%) (w/w). These samples were cultured in modified Klingers Iron Agar (KIA) at room temperature for 36 hours. The morphology of colonies was observed visually. Gram staining was done after preparation of heat fixed smear. Above colonies were further purified by streak plate technique and subjected to biochemical tests like acid fast, catalase and glucose fermentative activity. According to Bergey’s manual of determinative bacteriology and results obtained from biochemical tests, the main types of bacterial species identified are Bacillus polymixa, Bacillus subtilis, Bacillus coagulans, Lactobacillus casei, Lactobacillus fermenti and Cocci species. The media used to culture the bacteria consist of Bromocresol purple which turns yellow with acid producing bacteria and turn pink with non-acid producing bacteria. Observing the colour around the colonies revealed that only some bacteria produce acids even with high concentration of ammonia (i.e. 0.7% (w/w)), but they do not produce acids when the latex is preserved with LATZ. These results showed that ammonia resistant bacteria can be controlled using secondary preservatives. The results permit to understand the microbial activity in sterile and preserved natural rubber latex and can be used to select effective preservative system instead of currently used systems.
Improvement of surface properties of natural rubber latex films with a novel plasticizer
Softeners and plasticisers are used in latex compounding to reduce toughness and increase flexibility of articles such as gloves, balloons, etc. Petroleum based mineral oils and vegetable oils are the conventional plasticisers used in the industry. The main aim of this research was to improve surface properties of natural rubber latex films by replacement of paraffinic oil also known as white oil with an environmentally friendly plasticiser. Linseed oil obtained from the flax plant is a drying oil commonly used in oil paints to make paints more fluid, transparent and glossy. Commercially available linseed oil was selected as the novel plasticiser for this study. Linseed oil contains 52-55% of triply unsaturated α-linolenic acid and the ratio of unsaturated to saturated fatty acids in linseed oil is greater than that of vegetable oils and paraffinic oil. A series of natural rubber (NR) latex based compounds was prepared with 4, 6, 8 and 10 phr using a 50% emulsion of the linseed oil together with the other compounding ingredients. Two control NR latex compounds were also prepared; one with 6 phr using a 50% emulsion of white oil and the other without any plasticiser. Subsequently, cast films were prepared after curing at 100oC. Surface properties and physico-mechanical properties of these films were evaluated and compared with those of the two controls.Cast films prepared with linseed oil exhibited a smooth, glossy surface in comparison to those of the two controls indicating easy removal of articles from moulds and formers. Physico-mechanical property results showed that the tensile strength of the cast film prepared with 6 phr linseed oil is 39% and 77% higher than that of the films prepared with 6 phr white oil and without any plasticiser, respectively. Film prepared with 4 phr linseed oil showed the highest tensile strength. Increasing the oil loading upto 10 phr at 2 phr intervals resulted in a decrease in tensile strength. The tear strength of the cast film prepared with linseed oil was three times that of the film prepared with white oil. Improvement of properties of the film prepared with linseed oil over those of the film prepared with white oil could be attributed to increased interaction between unsaturated NR chains and highly unsaturated linseed oil. Results in overall indicated that petroleum based white oil could be replaced by plant based, and hence environmentally friendly, linseed oil in latex products manufacture with improvements in surface and strength properties.
Comparison study of three tractor tyre tread compounds
This project was carried out to develop a low cost rubber compound for retreading tractor wheels, while maintaining standard physical properties or perhaps with improved physical properties of the retread. The first formulate tried out was with the rubber content in the standard formula reduced by 10 phr and by increasing the filler load with the help of a tackyfying agent to obtain the expected volume. DPG 2phr was used as the booster accelerator to impart the vulcanization of the compound. The reason for adding tackyfing agent in the formula was to enhance the tackiness of the compound to facilitate more filler loading. When tackyfying agent is added, the dosage of ball clay and buffing dust and reclaim rubber addition up to 5 phr to the compound can be done conveniently. Physical properties of the vulcanizates of each of these compounds tried out were determined using ISO test methods. A marked increase in the specific gravity and the hardness of the compounds was observed with the substitution of fillers replacing rubber in the formule. Hence, the second lab scale trial (TR TEST-2) was carried out with the intention of reducing the specific gravity of the vulcanizate while improving physical properties. Reducing ball clay load by 5 phr and introducing the semi EV vulcanizing system it was possible to achieve physical properties comparable to the control. However, from this exercise it was not possible to significantly reduce the cost of the compound. In order to reduce the cost of the compound third lab scale trial (TR TEST-3) was conducted; in which the level of scrap crepe, aromatic oil and antioxidant were reduced by 10, 1 and 3 phr respectively. Physical properties of vulcanizates of TR TEST-3 trial were within the acceptable limit for tyre retreads. Further, the cost of the resulting compound was below the cost of the earlier compound used for the purpose by 7.95% thereby making it more economical to be used as the compound for retreading tractor tyres. In TR TEST 1 SG and hardness is higher due to addition of excess ball clay. In TR TEST2 and TR TEST3 the elongation value reached 300% due to excess reclaim rubber in their formulation. TR TEST 4 did not reach 300% elongation, because of the very high shear action on rubber exert on Banbury mill mixing.
Performance of a multifunctional additive as a coupling agent for silica filled natural rubber compounds
Suitability of a multifunctional additive (MFA), a widely available cheap natural polymer belonging to the group polysaccharides, as a coupling agent for silica filled natural rubber (NR) compounds was investigated using a solid tyre compound. The test compounds were prepared by replacing currently used silane coupling agent, Si-69, with the MFA in different proportions ranging from 10 – 50% by weight. A compound containing only Si-69 as the coupling agent was also prepared to use as the control. Rheological properties of test compounds were assessed by using a Oscillating Disc Rheometer (ODR 100) at 1500C. The effectiveness of the MFA as a coupling agent for silica in NR compounds was evaluated through investigation of mechanical properties such as tensile and tear strength of silica filled NR vulcanisates containing MFA. Rheological properties of the above compounds indicate that there is a marked influence of MFA on the cure time,t90, cure rate index(CRI), scorch time (ts2) and maximum torque (MH) of the rubber compounds. The compound became quite scorchy as the 50% of Si-69 was replaced by MFA and its cure time decreased by about 6 minutes. MH was increased by about 4 units resulting in an increase in CRI. Evaluation of technical properties of the vulcanisates of tread compounds reveals that, about 10-20% of Si-69 can be replaced with the MFA without adversely affecting mechanical properties such as tensile strength, tear strength and modulus. Aging properties vucanisates having 10% of Si-69 replaced with MFA were within acceptable regions though that tends to decline with increasing the MFA content. It appears that the added MFA is capable of functioning as a coupling agent for silica filled compounds but this coupling action gets masked with increasing its concentration in the rubber compound. This may be a consequence of cure acceleration effect imposed on the rubber compounds by the MFA as revealed by rheological properties.
Zingibain-Pectin-LDPE as a biodegradable composite material
Polymers have become common materials of our everyday lives due to their superior properties. However, polymer applications also contribute to the growing amounts of solid waste generated, as polymer products are often used only once before disposal. The disposal problem is not simply technical, but it also has social and economic aspects. Biodegradable polymers are materials with the ability to function for a temporary period and subsequently degrade to save the environment. Nowadays, fruit waste which are highly perishable and seasonal, is a problem to the processing industries and pollution monitoring agencies. Suitable methods have to be adopted to utilize them for the conversion into value-added products. The objective of this research was to produce biodegradable composite material with the help of Low Density Polyethylene (LDPE), pectin and natural enzymes. Pectin was extracted from the passion fruit waste (passion fruit rind) using hot acid extraction method. The biodegradability imparted by pectin can be further improved by introducing chemical enzymes. Enzymes are complex molecules and biological catalysts have the ability to increase rate of chemical reaction. Zingibain was used as a natural enzyme to enhance the biodegradability of the LDPE – pectin polymer blends. Zingibain was extracted from the ginger roots by using dry powder method with a yield of 20 wt%. The extracted pectin and zingibain were analyzed and characterized using Fourier Transform Infrared Spectroscopy (FTIR). All characteristic peaks related to pectin and zingibain were available in the extracted FTIR spectra. Laboratory scale internal mixture was used to prepare the LDPE – Pectin – Zingibain polymer mixture by using 3 wt% pectin and varying 1 wt% to 5 wt% Zingibain. Biodegradable polymer composite was prepared by using a hydraulic press. Time dependent weight loss, water absorption and tensile properties were measured to evaluate the degree of degradability. Pure LDPE samples retained high level of tensile strength and constant weight for the entire soil burial test period. On the other hand, LDPE- pectin - zingibain blend showed a significant decrease in the tensile strength and elongation. Soil burial test results showed that biodegradability of the LDPE – Pectin composite further accelerated by adding zingibain. This composite material can be used for different applications to control the environmental pollution.