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Heat explosions are sometimes observed during the synthesis of phenol formaldehyde (PF) resin. This scenario can be attributed to the high latent heat that was released and not dissipated leading to the occurrence of a runaway reaction. The synthesis temperature and time played important roles in controlling the heat release, hence preventing the resin from hardening during the synthesis process. This study aims to assess the rheological and viscoelasticity behaviors of the PF resin prepared using paraformaldehyde. The prepared PF resin was designed for laminate applications. The rheological behavior of the PF resin was assessed based on the different molar ratios of phenol to paraformaldehyde (P:F) mixed in the formulation. The molar ratios were set at 1.00:1.25, 1.00:1.50 and 1.00:1.75 of P to F, respectively. The rheological study was focused at specific synthesis temperatures, namely 40, 60, 80 and 100 &deg, C. The synthesis time was observed for 240 min, changes in physical structure and viscosity of the PF resins were noted. It was observed that the viscosity values of the PF resins prepared were directly proportional to the synthesis temperature and the formaldehyde content. The PF resin also exhibited shear thickening behavior for all samples synthesized at 60 &deg, C and above. For all PF resin samples synthesized at 60 &deg, C and above, their viscoelasticity results indicated that the storage modulus (G&prime, ), loss modulus(G&Prime, ) and tan &delta, are proportionally dependent on both the synthesis temperature and the formaldehyde content. Heat explosions were observed during the synthesis of PF resin at the synthesis temperature of 100 &deg, C. This scenario can lead to possible runaway reaction which can also compromise the safety of the operators.

Owing to the high cost of synthetic aramid fibers and the necessity for environmentally friendly alternatives, a portion of aramid was replaced by plain woven kenaf fiber, with different lay arrangements and thicknesses. The obtained hybrid composites with aramid and kenaf fibers were used to produce prototypes of army helmet shells. A hybrid composite material was produced using a hot press technique and comprises 19 layers of plain woven kenaf and aramid of various configurations and alternation. The behavior of this composite material on a quasi-static penetration test was studied and was found positive in terms of maximum load carried, energy absorbed in impact, and damage mechanisms. Consequently, a helmet armour was developed that was less costly and more readily available and that which could also be produced by reducing the potential harmful effects of petroleum products, without compromising the ballistic-resistant capability of the material.

In this experiment, thermoset cardanol resin was reinforced with short kenaf bast fibers to produce 100% green composites. Different fiber loadings based on weight ratios (0%, 30%, 40%, 50%, and 60%) were fabricated by the hand layup method followed by compression molding. The results indicated that 50UTK (untreated kenaf fibers) displays the highest mechanical properties (91.9% and 43.4% increment for tensile strength and impact strength, respectively) compared with the brittle cardanol polymer and other combinations of composite. This indicates a great load transfer mechanism by kenaf fiber reinforcement due to good fiber/matrix interface shown in scanning electron microscope (SEM) analyses. On the contrary, short kenaf fiber insertion creates a stress concentration spot at the fiber’s end causing slightly lower flexural properties. Besides, high processing temperature has caused damage to the fibers and made further reduction of flexural strength. Therefore, a better load transfer mechanism has been compensated by negative influences of kenaf fiber insertion. In conclusion, 50 wt% of kenaf fiber insertion is found to be the optimum loading for cardanol matrix.

This paper reviews the tensile properties of bamboo fiber reinforced polymer composites (BFRP). Environmentally friendly bamboo fibers have good mechanical properties, which make them suitable replacements for conventional fibers, such as glass and carbon, in composite materials. Better fiber and matrix interaction results in good interfacial adhesion between fiber/matrix and fewer voids in the composite. Several important factors improve matrix-fiber bonding and enhance the tensile properties of BFRP. Coupling agents, such as maleic anhydride polypropylene (MAPP), improve the adhesion of bamboo fibers in the polypropylene (PP) matrix. A high percentage of lignin content in bamboo fibers limits fiber separation, which leads to less matrix absorption between fibers. Steam explosion is the best extraction method for bamboo fibers, although an additional mechanically rubbing process is required for fiber separation. Generally, high fiber content results in good composite performance, but at a certain limit, the matrix does not adhere well with a saturated amount of fibers, and the composite tensile strength decreases. However, the tensile modulus of BFRP is not affected by excess fiber content. Hybridization of bamboo with conventional fibers increases the tensile strength of BFRP. The addition of micro/nano-sized bamboo fibrils into the carbon fabric composites slightly enhances composite strength.

Combat helmets have been utilized to provide protection against a variety of ballistic threats, by reducing traumatic head injuries and fatalities. Nevertheless, head protection from injury is critical to function and for survivability. Soldiers and civilians incur Traumatic Brain Injury (TBI) most commonly from exposure to homemade bombs or improvised explosive devices. Although the Personal Armor System for Ground Troops (PASGT) helmet is expensive, environmental issues are some technical advantages that encourage using natural/synthetic hybrid laminated composites. The effects of different configuration patterns of kenaf fibers on the Backface Signature and energy absorbed by a military helmet (PASGT) were investigated. The ballistic behaviors of the 19 layers of aramid composite and plain woven kenaf composite were compared to hybrid laminated composites. The ballistic impact tests were performed using a 9 mm full metal jacket bullet and fragment simulating projectiles at various impact velocities, using a powder gun on fabricated square panels and helmets. The results showed the positive effect of hybridization in terms of energy absorbed (i.e. penetration), Backface Signature and damage mechanisms for ballistic impact and NIJ (National Institute of Justice) tests. Hybridization of plain woven kenaf/Kevlar laminated composites will open new avenues to reduce the dependency on the ballistic resistance component (Kevlar) in the helmet shell.

The applications of hybrid natural/synthetic reinforced polymer composites have been rapidly gaining market share in structural applications due to their remarkable characteristics and the fact that most of the components made of these materials are subjected to cyclic loading. Their fatigue properties have received a lot of attention because predicting their behavior is a challenge due to the effects of the synergies between the fibers. The purpose of this work is to characterize the tension, compression, and tensile-compression fatigue behavior of six layers of Kevlar hybridized with one layer of woven kenaf reinforced epoxy, at a 35% weight fraction. Fatigue tests were carried out and loaded cyclically at 60%, 70%, 80%, and 90% of their ultimate compressive stress. The results give a complete description for tensile and compression properties and could be used to predict fatigue-induced failure mechanisms.

“Green” resole phenolic resins for laminating applications were synthesized, and their properties and thermal stability were determined. The plant-based cardanol and condensed tannin were used as the partial substitutes of up to 40% of the phenol in the synthesis of the phenolic resins. The resins were synthesized with different proportions of phenol (P) to cardanol (C) and with different total molar ratio to the formaldehyde (F) in the resins (1.25 to 2.0). An increased cardanol content resulted in a proportional increase in the flexibility and fracture toughness of the cured cardanol-phenol-formaldehyde (CPF) resins. Also, a direct proportionality was found between increasing cardanol content and decreased crosslink density of the CPF resins. The best results were obtained with the formulation with a P:F molar ratio equal to 1:1.25. Tannin was incorporated into the CPF resins and the fracture toughness and flexibility values of the cured Tannin-CPF resins were found to be proportional to and increasing with the tannin content. However, glass transition temperature (Tg), flexural stress, and flexural modulus values of the CPF resins decreased with the tannin content. TGA-FTIR study of the resins was carried out and the emitted gas species during the pyrolysis of the samples were identified. The thermal stability and the temperature of degradation of the cured CPF resins decreased with increasing cardanol content.

Kenaf is one of the important plants cultivated for natural fibres globally and is regarded as an industrial crop in Malaysia for various applications. This study was conducted to determine the effects of orientation on the tensile and flexural strengths, Charpy impact test, and morphological properties of kenaf fibre-reinforced poly vinyl butyral (PVB) composites. Laminates of 40% fibre weight fraction were manufactured using the hot press manufacturing technique at 0˚/90˚ and 45˚/−45˚ orientations, and eight specimens were prepared for each test. The mechanical properties of the composites were variably affected by the fibre orientation angle. The results showed that the composites at 0o/90o had the highest tensile strength, flexural strength, and flexural modulus, while the elongation at break was almost the same. Additionally, tests were carried out on the composites to determine their impact energy and impact strength. The results revealed that impact properties were affected in markedly different ways by different orientations. The composite at 45˚/−45˚ offered better impact properties than the composites at 0˚/90˚. In addition, scanning electron microscopy for impact specimens was employed to demonstrate the different failures in the fracture surfaces.

Phenol and formaldehyde are the well-known raw materials used in synthesizing Phenol Formaldehyde (PF) resin. PF resin has been used extensively in various applications including molding and composite laminate industries. This study focused on the synthesizing PF resin using formalin and/or paraformaldehyde for laminate application and assess the physical properties, mechanical properties and fracture toughness of the resins. The density, dynamic viscosity, solid content, gel time, flexural properties, tensile properties and fracture toughness of the synthesized resins were evaluated upon varying the formalin content from 0% to 40% (w/w) in the synthesis process. The result shows that addition of 40% w/w formalin in the PF resin synthesis had increased the fracture toughness and decreased the flexural strength and modulus properties of PF by 97.14% and 97.60% respectively. The tensile stress value was also reduced by 67.80% when the 40% w/w of formalin was added. However, the PF resins that produced by adding formalin up to 20% w/w in the PF resin synthesis, still maintained their flexural and tensile properties within the acceptable range required by EN438 standard for decorative high-pressure laminate (HPL) application. This work shows that paraformaldehyde enhanced the mechanical properties of PF laminate resin compared to formalin.

This paper reviews the published and ongoing research work on kenaf/synthetic and Kevlar®/cellulosic fiber-reinforced composite materials. The combination of natural fibers with synthetic fibers in hybrid composites has become increasingly applied in several different fields of technology and engineering. As a result, a better balance between performance and cost is expected to be achieved by 2015, through appropriate material design. This review is intended to provide an outline of the essential outcomes of those hybrid composite materials currently utilized, focusing on processing and mechanical and structural properties.

Thermogravimetric analysis and differential scanning calorimetry were used to study the thermal degradation and thermal stability of bamboo powder and its composites (EP-BFC) in a nitrogen atmosphere. The thermal stability of EP-BFC decreased as the bamboo filler-loading increased. Compared with epoxy, bamboo powder had a lower thermal stability, which reduced the thermal stability for the higher filler-loading composites. The addition of glass fibre to the EP-BFC improved the thermal stability of the new hybrid composites. Both the hybrid and non-hybrid composites exhibited similar thermal-induced degradation profiles that had only one mass loss step. However, a noticeable difference between the percentage value of the degradation between both the hybrid and non-hybrid composites showed that the EP/G-BFC hybrids were more thermally stable than the non-hybrid EP-BFC. Different materials experienced different activities, which were clearly shown from the DSC analysis. Bamboo fibre and non-fully cured epoxy exhibit exothermic peaks, while fully cured epoxy exhibits an endothermic peak.

Noil hemp fiber-reinforced polypropylene composites were fabricated using intermixer and injection molding machines. X-ray microtomography and Weibull statistical methods were employed to characterize the aspect ratio distributions of noil hemp fibers in the polypropylene matrices. The influence of fiber content (0–40 wt%) and compatibilizer addition (5 wt%) on IFSS (interfacial shear strengths) was evaluated by means of the modified Bowyer and Bader model. The evaluated IFSSs decreased from 9.7 to 7.2 MPa as the fiber content increased from 10 to 40 wt%. Also, the outcomes indicated increases to IFSSs for the maleic anhydride grafted polypropylene (MAPP)-coupled composites than uncoupled ones. They were used to predict theoretical tensile strength of the composites. A good agreement has been found between the theoretical and the experimental tensile strengths of composites indicating that the developed model has excellent capability to predict the tensile strength of noil hemp fiber reinforced polypropylene composites. Ultimately, the influences of interfacial shear strength; fiber strength and fiber aspect ratio were investigated using the developed model to predict composite tensile strengths.

Xenograft bone has been widely used as a bone grafting material because it gains advantages in biological and mechanical properties as compare with the use of an allograft bone. Heat-treatment of bone is recognized as one of the simple and practical methods to lower the human immunodeficiency virus (HIV) infection and overcome the risks of rejection and disease transfer during the bone transplantation. Therefore, understanding the change of bone’s organic matrix after heat treatment has become a significant topic. In this study, thermal gravimetric analysis (TGA) was used to investigate the condition of organic constituents of a bovine cortical bone. In order to well characterize the microstructural and mechanical property of the bone after heat treatment, nanoindention technique was also employed to measure the localized elastic modulus ( E ) and hardness ( H ) of its interstitial lamellae and osteons lamellae at the temperatures of 23 °C (RT), 37 °C, 90 °C, 120 °C and 160 °C, respectively. The TGA results demonstrated that heat-treated bones had three stages of weight loss. The first stage was the loss of water, which started from RT to 160 °C. Follow by a weight loss of organic constituents starting from 200 °C to 600 °C. Upon reaching 600 °C, the organic constituents were decomposed and mineral phase loss started taking place until 850 °C. From the nanoindentation results, it showed the values of E and H measured for the interstitial lamellae were higher than that of the osteons lamellae. This phenomenon indicates that the interstitial lamellae are stiffer and easy to be mineralized than osteons lamellae. For a specimen heat-treated at 90 °C, the values of E and H of interstitial lamellae and osteons lamellae were similar to a non-heat-treated specimen. For a specimen heat-treated at 120 °C, its interstitial lamellae had higher E and H values than osteons lamellae. When a specimen was heat-treated at 160 °C, both interstitial lamellae and osteons lamellae demonstrated a slight decrease of their E and H values. An ANOVA statistical analysis was used to analyze the difference in elastic properties and hardness in various temperature ranges.

Gomuti is a natural fibre obtained from Arenga pinnata tree. In its native countries, the fibre has been used as roof, rope, insulation and water filter. This paper presents a study into the physical, mechanical and thermal characteristics of gomuti fibre to observe its viability as natural fibre composite material. The study includes observations of fibre morphology, diameter, density, single fibre tensile testing and observation of fibre thermal stability. It was found that diameter of the studied gomuti fibre was in a range of 81–313 µm, with an average of 168 µm. Density of gomuti was ∼1.40 g/cm3. The average strength of single gomuti fibre was 173.9 MPa and the average modulus of elasticity was 3847 MPa. Alkali treatment with sodium hydroxide was conducted to evaluate modifications in the fibre’s characteristics. The treated gomuti fibres show altered diameter range, density, single fibre tensile properties and different thermogravimetric plots. Based on the results, gomuti fibre can be considered viable to be developed into natural fibre composites.

Natural fibres, unlike synthetic fibres fabricated in-house, grow naturally. Their geometrical and physical properties are highly affected by environmental issues such as climate change. For instance, inconsistent cross-sectional areas and shapes along the length of a natural fibre can result from environmental changes. These irregularities in natural fibres affect the ultimate load that can be carried by these fibres in structural engineering applications. In this study, the tensile properties of single hemp fibres were measured by taking into account, the variations in fibre diameters. Alkali, acetyl and silane treatments of fibres were carried out to obtain a better surface finish. The treatment effects on the fibres with respect to tensile properties were discussed. The relationship between tensile properties of treated fibres and the variation of their diameters was also studied. It was found that the tensile strength of chemically-treated fibres was lower than that of untreated fibres.

In this study, hemp fibres were treated with alkali, acetyl and silane chemicals. Fibre constituents such as cellulose, hemicellulose and lignin constituents were separated from treated fibres. The chemical and thermal influences of these constituents on the treated fibres were examined by using scanning electron microscope (SEM), fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Experimental results revealed that, hemicellulose was degraded faster than that of cellulose and lignin. Cellulose exhibited better thermal stability and lignin was degraded in a wide range of temperatures. The hydrophilic nature of the fibres was predominantly caused by the presence of hemicellulose and then lignin constituents. Hemicellulose and lignin were mostly removed by the alkalisation with higher concentrations of NaOH, followed by acetylation. Silane treatment could not remove the hemicellulose and lignin, rather this treatment facilitated coupling with the fibre constituents.

Novel epoxidized hemp oil-based biocomposites containing jute fibre reinforcement were produced at the Centre of Excellence in Engineered Fibre Composites (CEEFC) owing to the need to develop new types of biobased materials. Mechanical properties (tensile, flexural, Charpy impact and interlaminar shear), thermo-mechanical properties (glass transition temperature, storage modulus and crosslink density) and moisture-absorption properties (saturation moisture level and diffusion coefficient) were investigated and compared with samples containing commercially produced epoxidized soybean oil and a synthetic bisphenol A diglycidyl ether-based epoxy control, R246TX cured with a blend of triethylenetetramine and isophorone diamine. Scanning electron microscopy was also performed to investigate the fibre–matrix interface. Epoxidized hemp oil-based samples were found to have marginally superior mechanical, dynamic mechanical and similar water-absorption properties in comparison to samples made with epoxidized soybean oil bioresin; however, both sample types were limited to bioresin concentrations below 30%. Synthetic epoxy-based samples exhibited the highest mechanical, dynamic mechanical and lowest water-absorption properties of all investigated samples. This study has also determined that epoxidized hemp oil-based bioresins when applied to jute fibre-reinforced biocomposites can compete with commercially produced epoxidized soybean oil in biocomposite applications. Fil: Manthey, Nathan W.. University of Southern Queensland; Australia Fil: Cardona, Francisco. University of Southern Queensland; Australia Fil: Francucci, Gaston Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingenieria; Argentina. University of Southern Queensland; Australia Fil: Aravinthan, Thiru. University of Southern Queensland; Australia

Novel biocomposites made of an acrylated epoxidized hemp oil based bioresin reinforced with random hemp fiber mat were manufactured by the vacuum infusion technique. Mechanical properties (tensile, flexural, Charpy impact and interlaminar shear), dynamic mechanical properties (glass transition temperature, storage modulus and crosslink density) and moisture absorption properties (saturation moisture level and diffusion coefficient) were investigated and compared with samples manufactured under the same conditions but using a commercial synthetic vinylester resin as the polymeric matrix. Results showed that the 100% biocomposites mechanical performance is comparable to that of the hybrid composites made with the synthetic resin. Moisture absorption tests showed that acrylated epoxidized hemp oil based samples displayed both higher diffusion coefficient and saturation moisture content; however, fiber reinforcement was the dominant transfer mechanism. Vinyl ester based samples were found to have higher storage modulus, glass transition temperature and crosslink density than acrylated epoxidized hemp oil samples. Fil: Francucci, Gaston Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina Fil: Manthey, Nathan W. . University of Southern Queensland; Australia Fil: Cardona, Francisco. University of Southern Queensland; Australia Fil: Aravinthan, Thiru. University of Southern Queensland; Australia

Traditionally, the helmet shell has been used to provide protection against head injuries and fatalities caused by ballistic threats. In this study, because of the high cost of aramid fibres and the necessity for environmentally friendly alternatives, a portion of aramid was replaced with plain woven kenaf fibre, with different arrangements and thicknesses, without jeopardising the requirements demanded by U.S. Army helmet specifications. Furthermore, novel helmets were produced and tested to reduce the dependency on the ballistic resistance components. Their use could lead to helmets that are less costly and more easily available than conventional helmet armour. The hybrid materials subjected to ballistic tests were composed of 19 layers and were fabricated by the hot press technique using different numbers and configurations of plain woven kenaf and aramid layers. In the case of ballistic performance tests, a positive effect was found for the hybridisation of kenaf and aramid laminated composites.

Epoxidized (EHO) and acrylated (AEHO) bio-resins from hemp oil were synthesized, and their interpenetrating networks (IPNs) were investigated in reinforced bio-composites with natural jute fibres and glass fibres. The mechanical properties (tensile, flexural, Charpy impact, and inter-laminar shear) and viscoelastic properties (glass transition temperature, storage modulus, and crosslink density) of the bio-resins and their hybrid IPNs EHO/AEHO system were investigated as a function of the level of bio-resin hybridization. The hybrid bio-resins exhibited interpenetrating network (IPN) behaviour. Composites prepared with the synthetic vinyl ester (VE) and epoxy resins showed superior mechanical and viscoelastic properties compared with their bio-resins and IPNs-based counterparts. With glass fibre (GF) reinforcement, increases in the EHO content of the IPNs resulted in increased stiffness of the composites, while the strength, inter-laminar shear strength (ILSS), and impact resistance decreased. However, in the jute fibre reinforced bio-composites, increases in AEHO content generated increased tensile modulus, ILSS, and mechanical strength of the bio-materials. Crosslink density and glass transition temperature (Tg) were also higher for the synthetic resins than for the bio-resins. Increased AEHO content of the IPNs resulted in improved viscoelastic properties.

In this present work, effects of interlamina fibre orientation on the tensile properties of composites were studied and the results were discussed. The varying types of fibre oriented composites were prepared using the compression moulding technique at a pressure of 17 MPa. The different types of oriented composites investigated were 90°/0 ° /90 °, 0 ° /90 ° /0 °, 90 ° /0 ° /0 ° /90 °, 0 ° /45 ° /0 °, 0 ° /90 ° /45 ° /45 ° /90 ° /0 °, 0 ° /45 ° /90 ° /90 ° /45 ° /0 ° and these composites were subjected to tensile testing according to ASTM: D3039-08. The sisal fibres were arranged in various angles with the help of specially designed mould. It was found that the tensile strength of sisal fibre composites improved when 0 ° oriented fibres were positioned at the extreme layers of the composites compared to 90 ° oriented fibres. The highest tensile strength among the types of composites was observed for 0 ° /90 ° /0 °. The scanning electron microscopy (SEM) analysis was performed to understand the interphase adhesion mechanism.

This work addresses the results of experimental investigation carried out on mechanical and morphological properties of plain woven kenaf fiber reinforced PVB film which was prepared by hot press technique. The composites were prepared with various fiber contents: 0%, 10%, 20%, 30%, 40%, 50%, and 60% (by weight), with the processing parameters 165°C, 20 min, and at a pressure of 8 MPa applied on the material. Tensile, flexural, and Charpy impact properties were studied as well as morphological properties of impact fracture surface. With the increase in kenaf fibers content up to 40%, the PVB composites have shown lower tensile and flexural strength accompanied with reduction in the ultimate strain of the composite. The results showed that impact properties were affected in markedly different ways by using various kenaf contents and decrease with the increase in kenaf fiber content up to 40%; however, high impact strength was observed even with 40% kenaf fiber content. Furthermore, scanning electron microscopy for impact samples was utilised to demonstrate the different failures in the fracture surfaces for various kenaf fibers contents.

Gomuti fibre is obtained from Arenga pinnata tree and is known with other names such as sugar-palm fibre, gomutu, ijuk, serat aren and black fibre. This article presents a review on the physical, mechanical, chemical and thermal properties of gomuti fibre in comparison with other common natural fibres. Furthermore, this article reviews the mechanical properties of gomuti fibre composites with thermoset polymer resins based on the existing published literature. It is observable that gomuti fibre has a close similarity to coir fibre in its physical and mechanical properties than the other natural fibres. It has the characteristics of lower density, strength and modulus, but higher elongation. The composites with gomuti fibre also exhibit properties similar to coir fibre composites.

This paper provides a comprehensive overview on different surface treatments applied to natural fibres for advanced composites applications. In practice, the major drawbacks of using natural fibres are their high degree of moisture absorption and poor dimensional stability. The primary objective of surface treatments on natural fibres is to maximize the bonding strength so as the stress transferability in the composites. The overall mechanical properties of natural fibre reinforced polymer composites are highly dependent on the morphology, aspect ratio, hydrophilic tendency and dimensional stability of the fibres used. The effects of different chemical treatments on cellulosic fibres that are used as reinforcements for thermoset and thermoplastics are studied. The chemical sources for the treatments include alkali, silane, acetylation, benzoylation, acrylation and acrylonitrile grafting, maleated coupling agents, permanganate, peroxide, isocyanate, stearic acid, sodium chlorite, triazine, fatty acid derivate (oleoyl chloride) and fungal. The significance of chemically-treated natural fibres is seen through the improvement of mechanical strength and dimensional stability of resultant composites as compared with a pristine sample.

The viscoelastic properties of vinyl ester (VE) composites filled with calcium carbonate (CC) (CaCO3) powder have been evaluated using the dynamic mechanical analysis (DMA) technique. It was found that irrespective of the percentage by weight of CaCO3 powder, the VE composites postcured in an oven up to 60°C have higher glass transition temperatures (Tg) and storage modulus than their counterparts cured at ambient conditions. However, the loss moduli were lower for composites postcured in an oven than their ambient cured counterparts. It was also found that the crosslinking density of the composites slightly increased with particulate (CaCO3) loading and composites postcured in an oven have higher crosslinking density than their counterparts cured at ambient conditions. These results confirmed an increase in stiffness for composites with postcuring treatment. Micrographs by SEM were obtained and confirmed a close inter phase adhesion of the CC filler with the VE resin matrix in the composites.

The cure kinetics of two epoxidized hemp oil (EHO) based bioresins were studied and compared under both dynamic and isothermal conditions using differential scanning calorimetry (DSC). Neat triethylenetetramine (TETA) for the first system and a combination of isophorone diamine (IPD) and TETA for the second system were used as the hardeners for the two EHO-based bioresins. Lower total heats of reaction and an approximate 10% decrease in activation energies were observed for the IPD/TETA system. Maximum conversions of the TETA/IPD system were consistently higher than those of the TETA system throughout the entire temperature range suggesting enhanced curing characteristics. Kissinger and Ozawa–Flynn–Wall models were used to determine activation energies from dynamic DSC data. Both bioresin systems were found to display autocatalytic behavior with the TETA/IPD system showing high nth order influence. Kamal's autocatalytic isothermal model, modified to account for diffusion postvitrification was found to satisfactorily describe the cure behavior of both bioresin systems. Overall, the addition of IPD was found to increase the curing rate of the EHO bioresin systems.

In this study, hemp fabrics were used as reinforcements with polyester resin to form composite skins while short hemp fibres with polyester as a core for making composite sandwich structures. To improve the fibre matrix adhesion properties, alkalisation, silane and acetylation treatments on the fibres surface were carried out. Examinations through fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were conducted to investigate the physical and thermal properties of the fibres. Mechanical properties such as flexural and compressive strengths of the sandwich structures made by treated and untreated hemp fibres were studied. Based on the results obtained from the experiments, it was found that the fibre treated with alkalic solution and post-soaked by 8% NaOH exhibited better mechanical strength as compared with other treated and untreated fibre composite samples. Besides, DSC and TGA analysis showed that the thermal stability of all treated fibre was enhanced as compared with untreated samples.

Epoxy resin was filled with sawdust to optimize the flexural properties of the composite for structural applications. In order to reduce costs, it will be necessary to fill as much sawdust as possible subject to maintaining sufficient strength of the composites in civil and structural applications. This project varies the percentage by weight of the sawdust in the composites. The sawdust particles were sieved into three different sizes, which were

Using a small amount of nanoclay (montmorillonite (MMT)) can significantly enhance the thermal and mechanical properties of polymer-based composites. Therefore, an in depth understanding of the bonding characteristic between the nanoclay and its surrounding matrix is essential. In this study, Fourier Transform Infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were conducted to analyze the chemical composition between epoxy matrix and nanocomposite. These experiments revealed that a chemical bonding at an interface between the matrix and nanoclay of the composites did exist. Thus, such bonding can enhance the mechanical and thermal properties of resultant polymer composites as reported in many literatures.

Novel phenolic type of thermoset resins were synthesized, and their mechanical and toughness properties were evaluated. Phenol Formaldehyde (PF) phenolic resins were modified to broaden their applications for modern composite structures. A first modification consisted of copolymerization of Phenol with Cardanol during the synthesis of resole phenolic (CPF) resins. The modified phenolic resins (CPF) were prepared at various molar ratios of total Phenol to Formaldehyde (F : P ratio) and with different weight ratios of Phenol to Cardanol. CPF resins with a maximum content of 40 wt % of Cardanol were synthesized and used. The CPF resins were applied as a plasticizer and toughening agent to the base PF resins. Both resins (CPF/PF) were mixed in different proportions, and their thermal and mechanical properties were then established. A full miscibility of the two resins was observed with the formation of a single-phase system. An increase in the content of Cardanol resulted in a propor- tional increase of the flexural strength and fracture tough- ness together with a decrease of the flexural modulus of the cured CPF/PF resins. Further increased plasticizing and toughening effect was also observed by the blending of the CPF resins with propylene glycol. The higher tough- ness and flexibility effect of the CPF resins was obtained with a F : P molar ratio equal to 1.25 and with a Cardanol content of 40% (w/w).

The mechanical properties of sawdust reinforced vinyl ester resin composites post-cured in microwaves have been measured and evaluated in earlier studies. This basic but critical and important data have caused interests in the relevant industry in Australia. This study is therefore carried out to measure and evaluate the thermal properties of the composites with a view to benefit the civil and construction industry as the materials are used in the industry. The original contributions of this paper are that samples post-cured in microwaves, irrespective of the percentage by weight and particle size of sawdust, have higher glass transition temperatures than their counterparts post-cured in an oven; these imply that the stiffness of the samples post-cured in microwaves are higher than their peers. From previous study, it was discovered that the fracture toughness increased with increasing particulate loading. These properties are vital in civil engineering applications because civil structures need composites with high rigidity and fracture toughness. It is hoped that the discussions and results in this work would not only contribute towards the development of sawdust reinforced vinyl ester composites with better material properties, but also useful for the investigations of thermal and mechanical properties in other composites.

A novel epoxidized hemp oil (EHO) based bioresin was synthesised by epoxidation in situ with peroxyacetic acid. In this research the cure kinetics of an EHO based bioresin system cured with Triethylenetetramine (TETA) was studied by Differential Scanning Calorimetry (DSC) using both isothermal and non-isothermal data. The results show that the curing behaviour can be modelled with a modified Kamal autocatalytic model that accounts for a shift to a diffusion-controlled reaction post-vitrification. The total order of the reaction was found to decrease with an increase in temperature from approximately 5.2 at 110°C to approximately 2.4 at 120°C. Dynamic activation energies were determined from the Kissinger (51.8 kJ/mole) and Ozawa-Flynn-Wall (56.3 kJ/mole) methods. Activation energies determined from the autocatalytic method were 139.5 kJ/mole and -80.5 kJ/mole. The observed negative activation energy is thought to be due to an unidentified competitive reaction that gives rise to the appearance of decreasing with increasing temperature. The agreement of fit of the model predictions with experimental values was satisfactory for all temperatures.

Phenol formaldehyde composites are modified with glycerol—tannin mixes with varying percentages by weight of phenolic resin to glycerol—tannin. The glycerol-to-tannin ratio is also varied. In this study also, different percentages by weight of SLG (a commercial ceramic microsphere) are added to the composites. The effect of glycerol—tannin mix and added SLG on the flexural properties was studied. It was found that the flexural stress decreases gradually with increasing tannin when there is no SLG. With SLG, the presence of tannin in the composites reduces the flexural stress drastically. Tannin reduces the strain at break. With SLG, this reduction of the yield strain is more apparent. Tannin increases the flexural modulus of the composite and SLG acts in the opposite direction. The use of tannin in the phenolic composites improves the ‘green’ character of the composite materials. It was also found that the presence of tannin made the mixing of phenolic resins with glycerol easier.

Novel composites resins for civil engineering structures were synthesised. Resol phenolic resins were modified by the copolymerization of Phenol with Cardanol and Formaldehyde (CPF). The CPF resins were synthesized at different proportions of Phenol to Cardanol and also of the total Phenol to Formaldehyde. The synthesis was carried out under alkaline conditions and with a maximum content of 40 wt% of Cardanol. The effect of the partial substitution of Phenol by Cardanol on the thermal and mechanical properties of the CPF resins was investigated. The fracture toughness and flexibility values of the cured CPF resins were found to be proportional to the Cardanol content in the resins. However, the flexural modulus values of the resins decreased with the amount of Cardanol. The higher toughening effect of replacing Phenol with Cardanol was obtained with the total P:F molar ratio of 1.0:1.25. Also a direct proportionality between the amount of Cardanol content and the decrease in crosslink density of the resins was observed. Simultaneous TGA-FTIR studies of the resins were carried out and the emitted gases were identified. The results confirmed that the thermal stability and the temperature of degradation of the cured CPF resins decreased as the amount of Cardanol content increased. Gas emissions during the pyrolysis of the CPF resins also increased.

The advantageous properties of sawdust and phenolic resins were combined by making sawdust reinforced phenolic composites with different percentages by weight of sawdust. The sawdust was divided into three grades in accordance with its particulate size. Garamite and propylene glycol were added individually and together to enhance the flexural properties of the composites obtained. Without any garamite and propylene glycol, it was discovered that the best flexural properties of the composites were obtained when the percentage by weight of sawdust (< 300µ m) is up to 15%. Beyond this, the flexural properties dropped significantly; in addition, the fluidity of the composite was very low and the mixture was not suitable for casting. In general, the flexural modulus of the composites decreases with an increase in sawdust content, i.e. they are more elastic but their maximum flexural strain does not improve. Garamite was therefore added to improve the maximum flexural strains of the composites and this was successful. The addition of propylene glycol makes the composite more plastic.

Epoxy resin was mixed with phenolic resins in different percentages by weight. Composite 40/60 means the proportion by weight of epoxy resin is 40%. It was found that only composites 50/50 and 40/60 could be cured in ambient conditions. Dynamic mechanical analysis showed that only these two composites form interpenetrating polymer network. The addition of linseed oil to the two resins results also in the formation of interpenetrating network irrespective of proportion by weight of the resins; the mechanical properties will only be better when the percentage by weight of epoxy resin is higher; the aim of reducing cost and at the same time maintaining the mechanical properties cannot be fully achieved because epoxy resin is much more expensive than its counterpart.

Recently, the mankind has realized that unless environment is protected, he himself will be threatened by the over consumption of natural resource as well as substantial reduction of fresh air produced in the world. Conservation of forests and optimal utilization of agricultural and other renewable resources like solar and wind energies, and recently, tidal energy have become important topics worldwide. In such concern, the use of renewable resources such as plant and animal based fibre-reinforce polymeric composites, has been becoming an important design criterion for designing and manufacturing components for all industrial products. Research on biodegradable polymeric composites, can contribute for green and safe environment to some extent. In the biomedical and bioengineered field, the use of natural fibre mixed with biodegradable and bioresorbable polymers can produce joints and bone fixtures to alleviate pain for patients. In this paper, a comprehensive review on different kinds of natural fibre composites will be given. Their potential in future development of different kinds of engineering and domestic products will also be discussed in detail.

A commercial phenol formaldehyde-based resole thermosetting resin supplied by Borden Chemical Australia Pty., was reinforced with ceramic-based fillers (SLG) to increase its fracture toughness. This is the second study of the same series. By testing fracture toughness and viscosity at a range of filler addition levels, the optimal addition of SLG was determined in terms of workability, cost, and performance. The composites obtained were post-cured in a conventional oven as in the previous study. The original contributions of this article include lowering the cost of the composite (35wt% of SLG) by 50% but at the same time the fracture toughness was reduced only by 20% (compared to the neat resin), and increasing the fire resistance of the resins tremendously. It was also found that the values of fracture toughness of the samples in this study were higher than those obtained in the previous study when the percentage by weight of SLG varies from 0 to 35%. The shapes of the plots of fracture toughness against percentage by weight of SLG were also different. The possible reasons for the differences were explained.

Phenol formaldehyde was filled with Envirospheres SLG to increase the strength and impact toughness of the composite for structural applications by the Centre of Excellence in Engineered Fiber Composites (CEEFC), University of Southern Queensland (USQ). In order to reduce costs, the Centre wishes to fill as much SLG as possible subject to maintaining sufficient strength and impact toughness of the composites in structural applications. This project varies the percentages by weight of the SLG in the composites which are then subjected to tensile tests. The results show that composite with 10% by weight of the SLG produces the highest yield, tensile strengths and Young's modulus combined with a reasonable fluidity for casting.

Phenol formaldehyde was filled with Envirospheres slg to increase the strength of the composite for structural applications by a research Centre on composites, University of Southern Queensland (USQ). In order to reduce costs, the Centre wishes to fill as much slg as possible subject to maintaining sufficient strength of the composites in structural applications. This project varies the percentage by weight of the slg in the composites which are then subjected to flexural tests. The results show that composite with 25 % by weight of the slg produces the highest flexural strength and Young’s modulus combined with a reasonable fluidity for casting; the highest flexural strain was achieved when the percentage by weight of slg is 10 %.

The mechanical properties of ceramic microspheres (SLG) reinforced phenolic resin composites have been measured and evaluated in earlier studies. This basic but critical and important data has created interest in the relevant industry in Australia. This study is therefore carried out to measure and evaluate the dielectric and mechanical properties of the composites with a view to benefit the relevant industry. The relationship between the two properties will also be studied. The original contributions of this article are that samples post-cured in conventional ovens have higher electrical loss as well as mechanical loss than their counterparts post-cured in microwaves. The storage modulus of all samples post-cured conventionally is higher than its counterpart. This is in line with the fact that it is a softer material with lower glass transition temperature. They also have higher mechanical loss tangent as well as loss modulus. For all percentages by weight of SLG, the glass transition temperature for the microwave cured sample was higher and the composite was stiffer; the opposite was true for the conventionally cured sample.

In the earlier study about polymer network of phenolic and epoxies resins mixed with linseed oil, only Phencat 15 was used as the catalyst for the phenolic resin. In this study, Phencat 382 and UH (a urea hydrochloride solution based on a 1 : 1 mole ratio of urea : hydrochloric acid 32%) will be used as catalysts to study their effects on the polymer network of phenolic and epoxy resins mixed with epoxidized linseed oil (ELO) (58%). The effect of each one of these catalysts on the curing and the properties of the formed network were investigated. It was discovered that Phencat 382 was the best catalyst for the composites. It was also discovered that ELO can play its role as plasticiser in the blends of epoxy and phenolic resins and does improve the flexural strength and other mechanical properties of the prepared resins. The storage modulus, flexural modulus, stress at peak and glass transition temperature decreased with increasing percentage by weight of ELO added irrespective of the catalysts used, while the strain yield increased. The cross-link density decreased with the increasing amount of ELO in the resins. The best properties were obtained for the 80/20 epoxy/phenolic resin blends after post-curing for 4 hours.

Low cost composite materials are widely used in civil and structural engineering applications. This project uses EPON to plasticize a commonly used resin, epoxy resin to lower the cost of the composite and to find out the mechanical and thermal properties of the plasticized epoxy resin to see if it is suitable for the said applications. Three point bending tests were carried out to evaluate the flexural properties of the plasticized resins. Differential scanning calorimetry and dynamic mechanical thermal analysis are used to evaluate the thermal properties of the plasticized epoxy resin. The study with epoxy and EPON showed that the mechanical properties of the epoxy composite were lowered but its ability to dissipate energy increased because of its improved thermal properties. As EPON is much cheaper that epoxy resin, the composite produced is therefore cheaper and provided the service requirements were not so demanding, it can be used in the said applications.

The influence of styrene content and thickness of the samples on the UV curing of vinyl ester/styrene resins (VERs) is investigated by DSC and the combination of TGA and FTIR (TGA—FTIR). The glass transition temperatures (Tg) of the network polymers after curing are found to be lower for the VERs with higher styrene content. The released heat during UV curing further increases the Tg, with this increase being proportional to the volume of the resins. Within the range of thickness investigated (up to 30 mm) the relative amount of emissions of styrene, VE, and CO2 are found to be similar at the top and at the bottom of the samples. Similar results are obtained from the TGA analysis, indicating that the VERs are fully or almost fully cured all along the cross section. A good correlation is found between the analysis of the thermal properties by DSC and the results obtained by the TGA—FTIR system.

A commercial phenol formaldehyde based resole thermosetting resin (Hexion “J2027L”) was filled with ceramic-based fillers (Envirospheres “slg”) to increase its strength and fracture toughness. By testing viscosity, strength, and fracture toughness at a range of filler addition levels, the optimal addition level of SLG was able to be determined in terms of workability, cost, and performance. It was found that the fracture toughness of this resin could be significantly increased through the addition of the slg filler. The results show that composite with 20% by weight of the slg produces the best balance between ease of casting and impact performance.

Sugarcane fiber (i.e. bagasse) lignin has a larger fraction of aromatics unsubstitution in the ortho position than hardwood or softwood lignin and hence has the greater ability to be derivatized. Furthermore, organosolv lignin has a higher purity than sulfonated and kraft lignins. This work examines the purification of organosolv lignin derived from bagasse and the physico-chemical properties of the lignin and lignin-phenol formaldehyde (PF) resin coatings, and composites. The wetability tests have shown that lignin and lignin-PF resin films are effective water barrier coatings, though the contact angles of lignin-PF resin films were considerably less than the wax films. The overall mechanical properties (i.e. peak stress, peak strain and modulus) of the bagasse fiber composites were lower than the values obtained with the composites without the inclusion of bagasse fiber.

A commercial phenol formaldehyde based resole thermosetting resin supplied by Borden Chemical Australia Pty. was filled with ceramic-based fillers (Envirospheres “SLG”) to increase its fracture toughness. By testing fracture toughness at a range of filler addition levels, the optimal addition level of SLG was able to be determined in terms of workability, cost and performance. The composites obtained were post-cured in conventional oven and in microwaves respectively. It was found that the fracture toughness of the microwave cured composites were up to 37 % higher than those cured in conventional oven when the percentage by weight of SLG varies from 0 to 35%. The time required for post-curing was also reduced from 10 hours (in conventional oven) to 40 minutes (in microwaves).

The influence of styrene content on styrene added vinylester resin (VER) is investigated. The network structure and its thermal properties is investigated by differential scanning calorimetry (DSC) and the combination of thermal gravimetric analysis (TGA) and Fourier transform infrared spectrometry (FTIR) (TGA-FTIR). The glass transition temperatures ( Tgs) of the resins are found to decrease systematically with increasing styrene content, which decreases the crosslink density of the cured materials. The Tg of VER samples cured 97-98% is significantly lower, by as much as 25°C, than the Tg of a fully cured (100%) sample. This is due to the plasticizing effect of unreacted styrene in the network. The combination of TGA and FTIR confirm the evolution of gaseous styrene moieties at the degradation temperature of vinylester groups, the relative amount of styrene emitted being higher with increasing styrene content. A good correlation is found between the thermal properties by DSC and the results obtained from the TGA-FTIR system.

The effects of copolymer composition and microstructure on the radiation chemistry of styrene/alkane and alpha-methylstyrene/alkane copolymers have been studied. The primary radical species formed on radiolysis of the copolymers at 77 K, and identified by ESR spectroscopy, are the same as those formed during radiolysis of the homopolymers. The yields of radicals for the copolymer are as predicted assuming that the cross-section is proportional to the electron density of each component; however, there is some evidence of radical migration to aromatic groups at 77 K. Changes in molecular structure on irradiation were detected by using C-13 NMR spectroscopy. Evidence of the consumption of terminal double bonds, and chain scission in alpha-methylstyrene/alkane copolymers was found. Measurements of viscosity supported the mechanism of cross-linking predominating in styrene/alkane copolymers, while in alpha-methylstyrene/alkane copolymers chain scission was the major result of irradiation. (C) 2003 Society of Chemical Industry.

The radiolysis of nitrile rubbers with different acrylonitrile/butadiene composition and the homopolymers, poly(butadiene) (PBD) and poly(acrylonitrile) (PAN) has been investigated and compared with the photolysis of the same polymers. A significantly different mechanism of degradation was found for the two types of radiation. The results obtained by ESR, FTIR and measurements of soluble fractions of irradiated samples, indicated that the acrylonitrile units of the nitrile rubbers are more sensitive units to gamma-radiation, with the effects of irradiation increasing with the acrylonitrile content. The reactions observed were consumption of double bonds, crosslinking, and cyclization with the formation of conjugated double bonds. No chain-scission reactions were detected. In contrast to gamma-irradiation, the effects of photolysis were centred at the butadiene units, and increases in the acrylonitrile content resulted in a proportional decrease in the sensitivity of the copolymers. Crosslinking and chain scission were identified as the main effects of photolysis of NBR rubbers. (C) 1999 Society of Chemical Industry.