Cellulose microfibres from banana fibre waste have been isolated and characterised. Bleached banana waste fibres were hydrolysed, under different conditions, to study the effects of temperature, ...reaction time, and acid concentration on the properties of the resultant cellulose microfibres. As the concentration of acid used in the hydrolysis was increased, more stable aqueous suspensions of the cellulose product were obtained and the dimensions of the resulting cellulose microfibres were reduced. XRD studies reveal that cellulose prepared by such hydrolysis was more crystalline than the banana fibres. The effect of initial dimension of banana fibres on the size of cellulose microfibres was also examined.
Reversible addition−fragmentation chain transfer (RAFT) polymerization was used to control the grafting of styrene from a cellulose substrate. The hydroxyl groups of the cellulose fiber were ...converted into thiocarbonyl-thio chain transfer agent, and were further used to mediate the RAFT polymerization of styrene. The graft copolymers were analyzed by gravimetry, attenuated total reflectance Fourier transform infrared spectroscopy, contact angle measurements, scanning electron microscopy, differential scanning calorimetry, and thermogravimetry. The results obtained from these analytical techniques confirm that grafting occurred from the surface of the cellulose fibers. The poly(styrene) chains were also cleaved from the cellulose backbone and analyzed by size exclusion chromatography and showed narrow polydispersity.
Reversible addition fragmentation chain transfer (RAFT) polymerization was used for the first time to produce poly(methyl methacrylate) hyperbranched polymers via the one-pot copolymerization of ...methyl methacrylate (MMA) and ethylene glycol dimethacrylate, mediated by 2-(2-cyanopropyl) dithiobenzoate. Hyperbranched structures were characterized by 1H NMR spectroscopy, size exclusion chromatography (SEC), and thermal analyses. Monomer conversions and molecular weight distributions of hyperbranched poly(methyl methacrylate) (PMMA) prepared via RAFT polymerization are much higher and much lower, respectively, than those of the analogous polymers prepared via other living polymerization systems. Furthermore, the living character of the RAFT process was used to polymerize styrene from hyperbranched PMMA precursors (macro chain-transfer agent, macroCTA) and to produce starlike structures with hyperbranched PMMA as the core and polystyrene as the arms. DSC and SEC analyses support the observations made regarding the production of these novel architectures.
This critical review is concerned with the recent advances in graft polymerisation techniques involving cellulose and its derivatives. It summarises some of the features of cellulose structure and ...cellulose reactivity. Also described are the various techniques for grafting synthetic polymers from the cellulosic substrate. In addition to the traditional grafting techniques, we highlight the recent developments in polymer synthesis that allow increased control over the grafting process and permit the production of functional celluloses that possess improved physical properties and chemical properties (189 references).
2-(Dimethylamino)ethyl methacrylate (DMAEMA) was polymerized from cellulosic filter paper via reversible addition−fragmentation chain transfer (RAFT) polymerization. The tertiary amino groups of the ...grafted PDMAEMA chains were subsequently quaternized with alkyl bromides of different chain lengths (C8−C16) to provide a large concentration of quaternary ammonium groups on the cellulose surface. The antibacterial activity of the quaternized and nonquaternized PDMAEMA-grafted cellulosic fibers was tested against Escherichia coli. The antibacterial activity was found to depend on the alkyl chain length and on the degree of quaternization, i.e., the amount of quaternary amino groups present in the cellulose graft copolymers. The PDMAEMA-grafted cellulose fiber with the highest degree of quaternization and quaternized with the shortest alkyl chains was found to exhibit particularly high activity against E. coli.
The objective of this study is to determine if men would follow the “red effect” when choosing colors for women to wear on a date, and also to determine if the colors that men would wear when going ...on a date would be the same as the colors that females (their date) would wish them to wear. A set of psychophysical data was generated from this experiment, where participants were asked to rank a set of 10 colored samples based on preference for each question asked. There were three different sets of colored samples. The set of colored samples given to the participant depended on the question. A total of five questions were asked. Scaling analysis was done on the data to organize a set of items according to preferences providing values, an interval scale (Z values), that correspond to the relative perceptual differences among the stimuli. The Z values were graphed to show the general preference of colors for women to wear, and the preference of colors for men to wear. A Spearman's rank‐order correlation coefficient (SRCC) was calculated comparing each individual's rank order with the mean rank order for that specific question. An average Spearman's rank order was calculated for each question and each gender in order to determine the variability in answers. Scaling results indicate that men follow the “red effect,” but women preferred to wear other colors such as turquoise, blue, or yellow depending on the outfit. Males and females agreed that no matter the colored bottoms (denim or black), blue was the preferred color top for men to wear. SRCC results showed a lot of variability between individual answers and the mean answer indicating that participants' rankings did not necessarily agree with general color preferences presented in the scaling analysis. While scaling analysis might suggest certain color preferences such as men following the “red effect” and women preferring to wear blue, the poor correlation found using SRCC between the individual answers and the mean rank orders suggests that color preferences for each individual are inherently unique.
► Banana plant fibre waste as the source of cellulose whiskers. ► Preparation and characterization of poly(ethylene-co-vinyl acetate) EVA/cellulose whisker composites. ► Development of EVA/cellulose ...whisker composites – without using any compatibilizer. ► Superior thermal and mechanical properties. ► Comparison of the results of mechanical testing with theoretical modelling.
The reinforcing effect of cellulose whiskers, produced from banana waste fibres, has been investigated using poly(ethylene-co-vinyl acetate) EVA/cellulose whisker composites. Cellulose whiskers, approximately 300nm long and 30nm wide, were obtained via a sulphuric acid hydrolysis method. The effects of the cellulose whisker loading on the thermal properties, mechanical properties and on the morphological features of the composites have been investigated. EVA copolymer with a vinyl acetate segment content of 40% has been used for composite fabrication. The developed composites showed superior thermal and mechanical properties relative to that of the EVA copolymer alone. Three theoretical models, namely the Halpin–Tsai model, the Kerner model and the Nicolais–Narkis model have been employed to provide a basis for the comparison of the results with the observations from the tensile investigations.
Liquefaction of Central-European softwoods meal was performed using a mixture of diethylene glycol and glycerol and a minor addition of p-toluenesulfonic acid as a catalyst. The liquefied wood was ...used as a replacement of a certain amount of the polyhydroxy alcohol in the polyester synthesis, enabled by the large number of hydroxyl groups that were available in the liquefied wood. Three different polyesters were synthesized by using adipic acid and phthalic acid anhydride as reagents. The products were characterized using FTIR, GPC/SEC, and viscosity measurements. The polyesters have hydroxyl values that were reduced due to esterification, from 1043 mg KOH/g of the liquefied wood to 400-800 mg KOH/g. Polyhydroxyl alcohols (22-23%) in the polyester formulations were replaced by wood derivatives. Such saturated polyesters are suitable for further use in polyurethane foam production.
•Poly(butylene terephthalate) was analysed by inverse gas chromatography.•The enthalpy of adsorption of polar molecules on PBT was found to be endothermic.•The crystallisation activation energy of ...PBT is dominated by the Lewis basic sites.•Weaker Lewis acid/base intra(inter)molecular forces lead to lower extent of crystallization in PBT.•The analysis of Ka and Kb is useful in the interpretation of the crystallinity of PBT.
Two grades of poly(butylene terephthalate) were analysed by means of inverse gas chromatography (IGC) and the results correlated with the respective crystallisation properties. The following parameters were determined by IGC: the dispersive component of the surface tension, the enthalpy and the entropy of adsorption of selected polar and apolar probes, and the Lewis acidity and basicity constants, Ka and Kb respectively. The interpretation of the values determined for Ka and Kb is in agreement with the FTIR spectra relating to the carboxyl end-group and the hydroxyl end-group concentrations in these polymers. The differences in the molecular weight values and in the end-group type and concentration, between the two grades of PBT, do not cause differences in the crystallisation activation energy. This observation suggests that there is a leading contribution of the Lewis basic sites to the crystallisation activation energy of the grades of PBT that were analysed. However, the lower value of Ka and the greater molar mass of one of the PBT grades lead to a corresponding lower crystallisation degree.
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