CALLUM HILL | University of Bath (original) (raw)
Papers by CALLUM HILL
International Journal of Adhesion and Adhesives, 2002
Journal of The Chemical Society-dalton Transactions, 1995
Three new nickel(ii) complexes of 1 -alkyl-2-phenyl asymmetrically substituted dithiolenes [Ni(SC... more Three new nickel(ii) complexes of 1 -alkyl-2-phenyl asymmetrically substituted dithiolenes [Ni(SCR1=CR2S)2] ( R1 = Ph; R2 = Bun, cyclopentylmethyl or 4-pentylcyclohexyl) have been prepared and their electrochemical properties and near-IR spectra studied. The crystal structures of the complexes in which R2 = Bun or cyclopentylmethyl have been determined. The presence of bulky substituents adjacent to the ring has no affect upon the electrochemical or near-infrared properties.
Journal of Materials Chemistry, 1992
The third-order optical non-linearity, x (~) , linear absorption coefficient, CI, and the ratio o... more The third-order optical non-linearity, x (~) , linear absorption coefficient, CI, and the ratio of the real to imaginary parts of f 3 ) have been measured at 1.06 pm for a range of nickel dithiolene complexes with absorption bands between 0.77 and 1.06 pm. From these data the non-linear refractive index, n2, and the device-based figure of merit, W ( =Ansat/aA), were calculated. W was found to exceed 2 for materials with absorption maxima below 0.8-0.85 pm. The non-linear refractive index of a poly(methy1 methacrylate) host doped with 8 x 10'' molecules cmP3 of a nickel dithiolene was also measured and found to be nearly 2 x lo-' cm2 kW-'.
Journal of Materials Science, 2007
The mechanical properties of unidirectional flax fibre reinforced unsaturated polyester resin com... more The mechanical properties of unidirectional flax fibre reinforced unsaturated polyester resin composites were studied with particular emphasis on their tensile deformation behaviour. These materials displayed characteristic non-linear behaviour when loaded parallel to the axis of the fibre, with a distinct knee preceding a drop in stiffness. Further deformation resulted in strain hardening behaviour. Load cycling and acoustic emissions analysis were used to investigate the nature of the knee and it was found that this corresponded with yielding behaviour in the composite. A well-defined yield point could be identified, which in composites of around 60% fibre volume fraction, occurred at a strain of some 0.12% and a tensile stress of 32 MPa. Varying the interfacial properties, through chemical modification of the fibre prior to lamination, was found to have a marked effect upon the onset of yielding and the yield point itself, as well as the deformation and fracture behaviour of the laminate. It is considered that this behaviour is intimately linked to the straining behaviour of the fibre as well as the fibre–matrix interaction and hypotheses to explain the observed behaviour are presented.
Composite Interfaces, 2000
Decay protection against fungal attack is afforded by the chemical modification of wood. Many stu... more Decay protection against fungal attack is afforded by the chemical modification of wood. Many studies have been performed, particularly with acetylated wood, which have established decay protection thresholds. Despite these numerous studies, there is no real understanding of the mechanism by which decay protection occurs. This paper considers the various mechanisms proposed. Based upon recent studies of wood modified with anhydrides with different chain lengths, it is concluded that the main protection mechanism is related to cell wall bulking. Such bulking arises due to the bonded adduct occupying space within the cell wall. By so doing, less volume within the cell wall is available for water. It is well known that enzymes associated with decay fungi are too large to enter the micropores of the cell wall, and that low molecular weight diffusible agents are responsible for initial attack leading to an increase in pore dimensions. It is proposed that the lack of water within the cell wall of wood prevents the ingress of these agents into the cell wall, thereby inhibiting attack thereof.
A study of the piezoelectric and directcurrent conductive properties of thin films of conjugated ... more A study of the piezoelectric and directcurrent conductive properties of thin films of conjugated macrocyclic organic materials in the presence of industrial-pollutant gases is described. Particular attention is paid to the search for a reversible sensor for dinitrogen tetroxide that can operate in the range 1&1000ppm at or near room temperature in an industrial atmosphere. Recommendations are given for a reversible system for detecting HC1 and for a non-reversible system for the rapid detection of chlorine in the presence of electron-donor gases.
Applied Composite Materials, 2000
Hemp fibre-reinforced polyester composites were prepared using a Resin Transfer Moulding (RTM) te... more Hemp fibre-reinforced polyester composites were prepared using a Resin Transfer Moulding (RTM) technique and the flexural and impact behaviour investigated. Flexural stress at break and flexural modulus showed an increasing trend with fibre content. Impact strength was found to decrease at low fibre content, then gradually increase with further addition of fibres. A strong interfacial adhesion between hemp and polyester was obtained using chemically modified hemp. This modification consisted in introducing reactive vinylic groups at the surface of the fibres, via esterification of hemp hydroxyl groups, using methacrylic anhydride. Increased bonding between fibres and matrix did not affect the flexural stress at break of the composite but was detrimental to toughness. This behaviour was ascribed to a change in the mode of failure, from fibre pull-out to fibre fracture, resulting in a marked reduction in the energy involved in the failure of the composite, leading to a more brittle material.
Journal of Wood Chemistry and Technology, 1999
The reaction of wood with two functionalised epoxides, allyl glycidyl ether (AGE) and glycidyl me... more The reaction of wood with two functionalised epoxides, allyl glycidyl ether (AGE) and glycidyl methacrylate (GMA), has been studied. For the reaction with whole wood samples of Scots Pine (Pinus sylvestris), maximum weight percent gains (WPG's) of 20% (GMA) and 7% (AGE) were obtained using pyridine as a solvent/catalyst. However, reaction of the epoxides with thermomechanically pulped Spruce fibre yielded WPG's of 15% (GMA) and 0% (AGE) under the same reaction conditions. In addition, the use of hydroquinone as an inhibitor of polymerisation yielded variable results. The observed WPG's obtained were found to be strongly influenced by the clean-up procedure used at the end of the reaction. The results suggest that, under the conditions used in this study, no reaction with the wood hydroxyl groups is occurring but that homopolymerisation of the epoxides is responsible for the observed data.
Polymer Degradation and Stability, 2001
Pine sapwood samples were chemically modi®ed with methacrylic anhydride, and the modi®ed samples ... more Pine sapwood samples were chemically modi®ed with methacrylic anhydride, and the modi®ed samples were grafted with styrene via a free radical process. Unmodi®ed, modi®ed, and modi®ed and styrene grafted samples were exposed to UV irradiation and the samples were then analysed for colour, brightness, and chemical changes (using infra-red and X-ray photoelectron spectroscopy). Although modi®cation did impart colour stability to samples following UV exposure, there was no evidence that either modi®cation, or modi®cation plus grafting resulted in any improvement in the chemical stability of the wood. The colour stabilisation is attributed to the production of peroxy derivatives of the bonded acyl groups. #
Holzforschung, 2010
... Callum AS Hill1,*, Andrew Norton2 and Gary Newman3 1 Centre for Timber Engineering, Edinburgh... more ... Callum AS Hill1,*, Andrew Norton2 and Gary Newman3 1 Centre for Timber Engineering, Edinburgh Napier University, Edinburgh, UK 2 Renuables, Llanllechid ... this paper, no report in the literature of the appli-cation of the PEK model for studying the sorption behaviour of wood. ...
Journal of Applied Polymer Science, 2009
The water vapor sorption behavior of a range of natural fibers (jute, flax, coir, cotton, hemp, S... more The water vapor sorption behavior of a range of natural fibers (jute, flax, coir, cotton, hemp, Sitka spruce) has been studied. The data were analyzed using the Hailwood Horrobin model for isotherm fitting and determination of monolayer moisture content. The Hailwood Horrobin model was found to provide good fits to the experimental data. The extent of hysteresis exhibited between the adsorption and desorption isotherms was dependent on fiber type studied and was larger with high lignin compared with low lignin content fibers. The area bounded by the hysteresis loop decreased as the isotherms were performed at progressively higher temperatures. This behavior is consistent with sorption interactions occurring with a glassy solid below the glass transition temperature. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Holzforschung, 2004
Page 1. Holzforschung, Vol. 58, pp. 544547, 2004 Copyright by Walter de Gruyter Berlin New... more Page 1. Holzforschung, Vol. 58, pp. 544547, 2004 Copyright by Walter de Gruyter Berlin New York Dimensional changes in Corsican pine (Pinus nigra Arnold) modified with acetic anhydride measured using a helium pycnometer ...
Holzforschung, 2006
Page 1. Holzforschung, Vol. 60, pp. 625629, 2006 Copyright by Walter de Gruyter Berlin New... more Page 1. Holzforschung, Vol. 60, pp. 625629, 2006 Copyright by Walter de Gruyter Berlin New York. DOI 10.1515/HF.2006.105 Article in press - uncorrected proof Decay resistance of anhydride-modified Corsican pine sapwood exposed to the brown rot fungus ...
Holzforschung, 2007
An Error Occurred Setting Your User Cookie. This site uses cookies to improve performance. If you... more An Error Occurred Setting Your User Cookie. This site uses cookies to improve performance. If your browser does not accept cookies, you cannot view this site. Setting Your Browser to Accept Cookies. There are many reasons why a cookie could not be set correctly. ...
Journal of Applied Polymer Science, 2010
Sorption kinetic data for the interaction of water vapor with flax (Linum usitatissimum L.) were ... more Sorption kinetic data for the interaction of water vapor with flax (Linum usitatissimum L.) were analyzed used the parallel exponential kinetics (PEK) model, with excellent fits to the data being obtained. The PEK model is the sum of two exponential kinetics processes (fast and slow), which have characteristic times and moisture contents associated with them. The slow adsorption and desorption processes exhibited important differences in their characteristic times, although hysteresis in the moisture contents was found to be predominantly associated with the fast process. The kinetics was examined over a range of relative humidity (RH) values and at different temperatures, enabling the determination of activation energies for the adsorption and desorption kinetic processes throughout the hygroscopic range (from 5–95% RH). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Wood Science and Technology, 2010
The water vapour sorption properties of Sitka spruce (Picea abies) have been investigated over a ... more The water vapour sorption properties of Sitka spruce (Picea abies) have been investigated over a range of temperatures (14.2–43.8°C) using a dynamic vapour sorption apparatus. The sorption kinetics behaviour was evaluated using the parallel exponential kinetics model which has been found to give very accurate fits to the data in studies of foodstuffs or plant fibres, but has not been previously applied to sorption studies with wood. Both the adsorption and desorption kinetics curve can be deconvoluted into a fast and slow exponential process. Under conditions of adsorption, the fast process appears to be associated with the formation of monolayer water (determined using the Hailwood Horrobin model) up to a relative humidity of 20%. Under desorption, there is no clear differentiation between fast and slow processes. The area bounded by the sorption hysteresis loop reduced as the temperature at which the isotherm was measured increased, due to movement of the desorption curve only, with the adsorption curve remaining the same at all temperatures. This behaviour is consistent with sorption processes taking place on nanoporous glassy solids below the glass transition temperature. The heat of wetting was determined from the temperature dependence of the desorption isotherms by using the Clausius–Clapeyron equation, yielding results that are consistent with literature values. However, doubts are raised in this paper as to the applicability of using the Clausius–Clapeyron equation for analyses of this type.
Composites Part A-applied Science and Manufacturing, 2010
Natural fiber reinforced polymer composites (NFPCs) provide the customers with more alternatives ... more Natural fiber reinforced polymer composites (NFPCs) provide the customers with more alternatives in the material market due to their unique advantages. Poor fiber-matrix interfacial adhesion may, however, negatively affect the physical and mechanical properties of the resulting composites due to the surface incompatibility between hydrophilic natural fibers and non-polar polymers (thermoplastics and thermosets). A variety of silanes (mostly trialkoxysilanes) have been applied as coupling agents in the NFPCs to promote interfacial adhesion and improve the properties of composites. This paper reviews the recent progress in using silane coupling agents for NFPCs, summarizes the effective silane structures from the silane family, clarifies the interaction mechanisms between natural fibers and polymer matrices, and presents the effects of silane treatments on the mechanical and outdoor performance of the resulting composites.
Journal of Materials Science, 2011
Hygroscopic behaviour is an inherent characteristic of natural fibres which can influence their a... more Hygroscopic behaviour is an inherent characteristic of natural fibres which can influence their applications as textile fabrics and composite reinforcements. In this study, the water vapour sorption kinetic properties of cotton, filter paper, flax, hemp, jute, and sisal fibres were determined using a dynamic vapour sorption apparatus and the results were analyzed by use of a parallel exponential kinetics (PEK) model. With all of the fibres tested, the magnitude of the sorption hysteresis observed varied, but it was always greatest at the higher end of the hygroscopic range. Flax and sisal fibres displayed the lowest and highest total hysteresis, respectively. The PEK model, which is comprised of fast and slow sorption components, exhibited hysteresis in terms of mass for both processes between the adsorption and desorption isotherm. The hysteresis derived from the slow sorption process was less than from the fast process for all tested fibres. The fast processes for cotton and filter paper dominated the isotherm process; however, the hemp and sisal fibres displayed a dominant slow process in the isotherm run. The characteristic time for the fast sorption process did not vary between adsorption and desorption, except at the top end of the hygroscopic range. The characteristic time for the slow process was invariably larger for the desorption process. The physical interpretation of the PEK model is discussed.
International Journal of Adhesion and Adhesives, 2002
Journal of The Chemical Society-dalton Transactions, 1995
Three new nickel(ii) complexes of 1 -alkyl-2-phenyl asymmetrically substituted dithiolenes [Ni(SC... more Three new nickel(ii) complexes of 1 -alkyl-2-phenyl asymmetrically substituted dithiolenes [Ni(SCR1=CR2S)2] ( R1 = Ph; R2 = Bun, cyclopentylmethyl or 4-pentylcyclohexyl) have been prepared and their electrochemical properties and near-IR spectra studied. The crystal structures of the complexes in which R2 = Bun or cyclopentylmethyl have been determined. The presence of bulky substituents adjacent to the ring has no affect upon the electrochemical or near-infrared properties.
Journal of Materials Chemistry, 1992
The third-order optical non-linearity, x (~) , linear absorption coefficient, CI, and the ratio o... more The third-order optical non-linearity, x (~) , linear absorption coefficient, CI, and the ratio of the real to imaginary parts of f 3 ) have been measured at 1.06 pm for a range of nickel dithiolene complexes with absorption bands between 0.77 and 1.06 pm. From these data the non-linear refractive index, n2, and the device-based figure of merit, W ( =Ansat/aA), were calculated. W was found to exceed 2 for materials with absorption maxima below 0.8-0.85 pm. The non-linear refractive index of a poly(methy1 methacrylate) host doped with 8 x 10'' molecules cmP3 of a nickel dithiolene was also measured and found to be nearly 2 x lo-' cm2 kW-'.
Journal of Materials Science, 2007
The mechanical properties of unidirectional flax fibre reinforced unsaturated polyester resin com... more The mechanical properties of unidirectional flax fibre reinforced unsaturated polyester resin composites were studied with particular emphasis on their tensile deformation behaviour. These materials displayed characteristic non-linear behaviour when loaded parallel to the axis of the fibre, with a distinct knee preceding a drop in stiffness. Further deformation resulted in strain hardening behaviour. Load cycling and acoustic emissions analysis were used to investigate the nature of the knee and it was found that this corresponded with yielding behaviour in the composite. A well-defined yield point could be identified, which in composites of around 60% fibre volume fraction, occurred at a strain of some 0.12% and a tensile stress of 32 MPa. Varying the interfacial properties, through chemical modification of the fibre prior to lamination, was found to have a marked effect upon the onset of yielding and the yield point itself, as well as the deformation and fracture behaviour of the laminate. It is considered that this behaviour is intimately linked to the straining behaviour of the fibre as well as the fibre–matrix interaction and hypotheses to explain the observed behaviour are presented.
Composite Interfaces, 2000
Decay protection against fungal attack is afforded by the chemical modification of wood. Many stu... more Decay protection against fungal attack is afforded by the chemical modification of wood. Many studies have been performed, particularly with acetylated wood, which have established decay protection thresholds. Despite these numerous studies, there is no real understanding of the mechanism by which decay protection occurs. This paper considers the various mechanisms proposed. Based upon recent studies of wood modified with anhydrides with different chain lengths, it is concluded that the main protection mechanism is related to cell wall bulking. Such bulking arises due to the bonded adduct occupying space within the cell wall. By so doing, less volume within the cell wall is available for water. It is well known that enzymes associated with decay fungi are too large to enter the micropores of the cell wall, and that low molecular weight diffusible agents are responsible for initial attack leading to an increase in pore dimensions. It is proposed that the lack of water within the cell wall of wood prevents the ingress of these agents into the cell wall, thereby inhibiting attack thereof.
A study of the piezoelectric and directcurrent conductive properties of thin films of conjugated ... more A study of the piezoelectric and directcurrent conductive properties of thin films of conjugated macrocyclic organic materials in the presence of industrial-pollutant gases is described. Particular attention is paid to the search for a reversible sensor for dinitrogen tetroxide that can operate in the range 1&1000ppm at or near room temperature in an industrial atmosphere. Recommendations are given for a reversible system for detecting HC1 and for a non-reversible system for the rapid detection of chlorine in the presence of electron-donor gases.
Applied Composite Materials, 2000
Hemp fibre-reinforced polyester composites were prepared using a Resin Transfer Moulding (RTM) te... more Hemp fibre-reinforced polyester composites were prepared using a Resin Transfer Moulding (RTM) technique and the flexural and impact behaviour investigated. Flexural stress at break and flexural modulus showed an increasing trend with fibre content. Impact strength was found to decrease at low fibre content, then gradually increase with further addition of fibres. A strong interfacial adhesion between hemp and polyester was obtained using chemically modified hemp. This modification consisted in introducing reactive vinylic groups at the surface of the fibres, via esterification of hemp hydroxyl groups, using methacrylic anhydride. Increased bonding between fibres and matrix did not affect the flexural stress at break of the composite but was detrimental to toughness. This behaviour was ascribed to a change in the mode of failure, from fibre pull-out to fibre fracture, resulting in a marked reduction in the energy involved in the failure of the composite, leading to a more brittle material.
Journal of Wood Chemistry and Technology, 1999
The reaction of wood with two functionalised epoxides, allyl glycidyl ether (AGE) and glycidyl me... more The reaction of wood with two functionalised epoxides, allyl glycidyl ether (AGE) and glycidyl methacrylate (GMA), has been studied. For the reaction with whole wood samples of Scots Pine (Pinus sylvestris), maximum weight percent gains (WPG's) of 20% (GMA) and 7% (AGE) were obtained using pyridine as a solvent/catalyst. However, reaction of the epoxides with thermomechanically pulped Spruce fibre yielded WPG's of 15% (GMA) and 0% (AGE) under the same reaction conditions. In addition, the use of hydroquinone as an inhibitor of polymerisation yielded variable results. The observed WPG's obtained were found to be strongly influenced by the clean-up procedure used at the end of the reaction. The results suggest that, under the conditions used in this study, no reaction with the wood hydroxyl groups is occurring but that homopolymerisation of the epoxides is responsible for the observed data.
Polymer Degradation and Stability, 2001
Pine sapwood samples were chemically modi®ed with methacrylic anhydride, and the modi®ed samples ... more Pine sapwood samples were chemically modi®ed with methacrylic anhydride, and the modi®ed samples were grafted with styrene via a free radical process. Unmodi®ed, modi®ed, and modi®ed and styrene grafted samples were exposed to UV irradiation and the samples were then analysed for colour, brightness, and chemical changes (using infra-red and X-ray photoelectron spectroscopy). Although modi®cation did impart colour stability to samples following UV exposure, there was no evidence that either modi®cation, or modi®cation plus grafting resulted in any improvement in the chemical stability of the wood. The colour stabilisation is attributed to the production of peroxy derivatives of the bonded acyl groups. #
Holzforschung, 2010
... Callum AS Hill1,*, Andrew Norton2 and Gary Newman3 1 Centre for Timber Engineering, Edinburgh... more ... Callum AS Hill1,*, Andrew Norton2 and Gary Newman3 1 Centre for Timber Engineering, Edinburgh Napier University, Edinburgh, UK 2 Renuables, Llanllechid ... this paper, no report in the literature of the appli-cation of the PEK model for studying the sorption behaviour of wood. ...
Journal of Applied Polymer Science, 2009
The water vapor sorption behavior of a range of natural fibers (jute, flax, coir, cotton, hemp, S... more The water vapor sorption behavior of a range of natural fibers (jute, flax, coir, cotton, hemp, Sitka spruce) has been studied. The data were analyzed using the Hailwood Horrobin model for isotherm fitting and determination of monolayer moisture content. The Hailwood Horrobin model was found to provide good fits to the experimental data. The extent of hysteresis exhibited between the adsorption and desorption isotherms was dependent on fiber type studied and was larger with high lignin compared with low lignin content fibers. The area bounded by the hysteresis loop decreased as the isotherms were performed at progressively higher temperatures. This behavior is consistent with sorption interactions occurring with a glassy solid below the glass transition temperature. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Holzforschung, 2004
Page 1. Holzforschung, Vol. 58, pp. 544547, 2004 Copyright by Walter de Gruyter Berlin New... more Page 1. Holzforschung, Vol. 58, pp. 544547, 2004 Copyright by Walter de Gruyter Berlin New York Dimensional changes in Corsican pine (Pinus nigra Arnold) modified with acetic anhydride measured using a helium pycnometer ...
Holzforschung, 2006
Page 1. Holzforschung, Vol. 60, pp. 625629, 2006 Copyright by Walter de Gruyter Berlin New... more Page 1. Holzforschung, Vol. 60, pp. 625629, 2006 Copyright by Walter de Gruyter Berlin New York. DOI 10.1515/HF.2006.105 Article in press - uncorrected proof Decay resistance of anhydride-modified Corsican pine sapwood exposed to the brown rot fungus ...
Holzforschung, 2007
An Error Occurred Setting Your User Cookie. This site uses cookies to improve performance. If you... more An Error Occurred Setting Your User Cookie. This site uses cookies to improve performance. If your browser does not accept cookies, you cannot view this site. Setting Your Browser to Accept Cookies. There are many reasons why a cookie could not be set correctly. ...
Journal of Applied Polymer Science, 2010
Sorption kinetic data for the interaction of water vapor with flax (Linum usitatissimum L.) were ... more Sorption kinetic data for the interaction of water vapor with flax (Linum usitatissimum L.) were analyzed used the parallel exponential kinetics (PEK) model, with excellent fits to the data being obtained. The PEK model is the sum of two exponential kinetics processes (fast and slow), which have characteristic times and moisture contents associated with them. The slow adsorption and desorption processes exhibited important differences in their characteristic times, although hysteresis in the moisture contents was found to be predominantly associated with the fast process. The kinetics was examined over a range of relative humidity (RH) values and at different temperatures, enabling the determination of activation energies for the adsorption and desorption kinetic processes throughout the hygroscopic range (from 5–95% RH). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Wood Science and Technology, 2010
The water vapour sorption properties of Sitka spruce (Picea abies) have been investigated over a ... more The water vapour sorption properties of Sitka spruce (Picea abies) have been investigated over a range of temperatures (14.2–43.8°C) using a dynamic vapour sorption apparatus. The sorption kinetics behaviour was evaluated using the parallel exponential kinetics model which has been found to give very accurate fits to the data in studies of foodstuffs or plant fibres, but has not been previously applied to sorption studies with wood. Both the adsorption and desorption kinetics curve can be deconvoluted into a fast and slow exponential process. Under conditions of adsorption, the fast process appears to be associated with the formation of monolayer water (determined using the Hailwood Horrobin model) up to a relative humidity of 20%. Under desorption, there is no clear differentiation between fast and slow processes. The area bounded by the sorption hysteresis loop reduced as the temperature at which the isotherm was measured increased, due to movement of the desorption curve only, with the adsorption curve remaining the same at all temperatures. This behaviour is consistent with sorption processes taking place on nanoporous glassy solids below the glass transition temperature. The heat of wetting was determined from the temperature dependence of the desorption isotherms by using the Clausius–Clapeyron equation, yielding results that are consistent with literature values. However, doubts are raised in this paper as to the applicability of using the Clausius–Clapeyron equation for analyses of this type.
Composites Part A-applied Science and Manufacturing, 2010
Natural fiber reinforced polymer composites (NFPCs) provide the customers with more alternatives ... more Natural fiber reinforced polymer composites (NFPCs) provide the customers with more alternatives in the material market due to their unique advantages. Poor fiber-matrix interfacial adhesion may, however, negatively affect the physical and mechanical properties of the resulting composites due to the surface incompatibility between hydrophilic natural fibers and non-polar polymers (thermoplastics and thermosets). A variety of silanes (mostly trialkoxysilanes) have been applied as coupling agents in the NFPCs to promote interfacial adhesion and improve the properties of composites. This paper reviews the recent progress in using silane coupling agents for NFPCs, summarizes the effective silane structures from the silane family, clarifies the interaction mechanisms between natural fibers and polymer matrices, and presents the effects of silane treatments on the mechanical and outdoor performance of the resulting composites.
Journal of Materials Science, 2011
Hygroscopic behaviour is an inherent characteristic of natural fibres which can influence their a... more Hygroscopic behaviour is an inherent characteristic of natural fibres which can influence their applications as textile fabrics and composite reinforcements. In this study, the water vapour sorption kinetic properties of cotton, filter paper, flax, hemp, jute, and sisal fibres were determined using a dynamic vapour sorption apparatus and the results were analyzed by use of a parallel exponential kinetics (PEK) model. With all of the fibres tested, the magnitude of the sorption hysteresis observed varied, but it was always greatest at the higher end of the hygroscopic range. Flax and sisal fibres displayed the lowest and highest total hysteresis, respectively. The PEK model, which is comprised of fast and slow sorption components, exhibited hysteresis in terms of mass for both processes between the adsorption and desorption isotherm. The hysteresis derived from the slow sorption process was less than from the fast process for all tested fibres. The fast processes for cotton and filter paper dominated the isotherm process; however, the hemp and sisal fibres displayed a dominant slow process in the isotherm run. The characteristic time for the fast sorption process did not vary between adsorption and desorption, except at the top end of the hygroscopic range. The characteristic time for the slow process was invariably larger for the desorption process. The physical interpretation of the PEK model is discussed.