Interfacial Properties of Phosphate Glass Fiber/Poly(caprolactone) System Measured Using the Single Fiber Fragmentation Test

Phosphate glass fiber of the composition 20Na₂O–24MgO–16CaO–40P₂O₅ was produced using an in-house fiber drawing rig. The interfacial properties of the phosphate glass fiber/poly(caprolactone) (PCL) system were measured using the single fiber fragmentation test (SFFT). The system was calibrated using E-glass fibers and polypropylene system. This gave an interfacial shear strength (IFSS) of 4.1 MPa, which agrees well with other published data. The IFSS for the unsized (as drawn) phosphate glass fiber/PCL system was found to be 1.75 MPa. Fibers treated with 3-aminopropyl-triethoxy silane (APS) showed an IFSS of 3.82 MPa. X-ray photoelectron spectroscopic (XPS) analysis of unsized and silane sized fibers established the presence of silane on the fiber surface. Degradation tests of the silane treated fiber/PCL samples were carried out in deionised water at 37°C and it was found that the IFSS values decreased over time. Four others silanes were also investigated but APS gave the highest IFSS values.     

Injection Molding of Wood–Fiber/Plastic Composite Foams

This paper investigates the feasibility of injection-molded wood–fiber/high-density polyethylene (HDPE) composite foams that can replace injection-molded HDPE solids in industrial applications. The study applies injection foam molding technology using a physical blowing agent to a wood–fiber/HDPE composite, and examines the effects of the processing parameters on the dimensional and mechanical properties and cell density of the composite foams. In addition, the physical properties and cost of wood–fiber/HDPE composite foams are compared with those of solid HDPE. The experimental results show that wood–fiber/HDPE composite foams that have a 20% weight reduction have superior physical properties, such as density, dimensional properties (68% decrease of shrinkage and 91% decrease of warpage) and mechanical properties (28% increase of Young's modulus). Furthermore, the cost analysis confirms that wood–fiber/HDPE composite foams are much less expensive (by 40%) than HDPE. Therefore, it is concluded that wood–fiber/HDPE composite foams are strong candidates for replacing current injection-molded HDPE products.     

Thermal behavior of chemically treated and untreated sisal fiber reinforced composites fabricated by resin transfer molding

Using thermogravimetric analysis (TGA), the thermal behavior of sisal fibers and sisal/polyester composites, fabricated by resin transfer molding (RTM), has been followed. Chemical treatments have been found to increase the thermal stability, which has been attributed to the resultant physical and chemical changes. Scanning electron microscopy (SEM) and infrared (FT-IR) studies were also performed to study the structural changes and morphology in the sisal fiber during the treatment. The kinetic studies of thermal degradation of untreated and treated sisal fibers have been performed using Broido method. In the composites, as the fiber content increases, the thermal stability of the matrix decreases. The treated fiber reinforced composites have been found to be thermally more stable than the untreated derivatives. The increased thermal stability and reduced moisture behavior of treated composites have been correlated with fiber/matrix adhesion.     

Improvement of resin impregnation into glass cloth by silane treatment in resin transfer molding

An evaluation method was proposed for resin impregnation using resin transfer molding of unsaturated polyester matrix composites with silane-treated glass cloth. The determination of whitening of the composite was carried out as a parameter of incompleteness of resin impregnation. The change of whitening with silane concentration was compared with the bending modulus as a parameter of chemical reinforcement. The materials used were unsaturated polyester resin as a matrix and methacryloxypropyltrimethoxysilane as a silane coupling agent for glass cloth. Resin transfer molding was used to produce four plies of glass cloth laminates by impregnating the resin. The silane-treated glass cloth repressed whitening above 0.026 w/w% of silane in aqueous solution, while the chemical reinforcement due to silane gave no appearance below 0.2 w/w% based on the bending test of the laminates. The large difference between the concentrations suggested that silane has a couple of functions, that is, chemical reinforcement and physico-chemical resin wettability.     

Amino Functionalization of MWNTs and Their Effect on ILSS of Hybrid Nanocomposites

Multi-walled carbon nanotubes (MWNT) were oxidized by treatment with a mixture of sulfuric and nitric acids to introduce carboxyl groups on their surfaces. Triethylene tetraamine (TETA) was then grafted onto the oxidized MWNTs via a thionyl chloride route to obtain the amino-functionalized MWNTs (f-MWNT). The presence of amino functional groups on the MWNTs was confirmed using FT-IR, and scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to compare the morphology of pristine MWNT (p-MWNT) and f-MWNT. Both the p-MWNT and f-MWNT were dispersed in epoxy resin using ultrasonic agitation and the suspensions were injected into E-glass fiber woven fabric using a specialized vacuum assisted resin transfer molding (VARTM) process in which a flow flooding chamber (FFC) was used to re-direct the suspension flow. Control samples were fabricated using the same E-glass fiber mat and unmodified epoxy resin following the same procedure. Compression shear testing (CST) was performed on all the manufactured samples to determine their Inter laminar shear strength (ILSS). Results show 41% increase in ILSS for hybrid composites containing p-MWNTs and a 61% increase for samples containing f-MWNTs relative to the control samples without MWCNT.     

Effect of chemical treatment on dynamic mechanical properties of sisal fiber-reinforced polyester composites fabricated by resin transfer molding

The dynamic mechanical properties of treated sisal fiber-reinforced polyester composites fabricated by resin transfer molding (RTM) have been studied with reference to fiber surface modifications, frequency and temperature. The sisal fibers have been subjected to various chemical and physical treatments like mercerization, heating at 100°C, permanganate, benzoylation and vinyl tris(2-ethoxymethoxy) silane to improve the interfacial bonding with isophthalic polyester resin. Results indicated that treatment changed the storage modulus (E′), loss modulus (E″) and damping factor (tan δ) drastically at a wide range of temperature. The E′ value increased for every treatment, and is maximum for the composites fabricated by benzoylated-treated fibers. The T _g value obtained from the E″value showed an increase as compared to untreated fiber-reinforced composites. The alkali-treated fiber-reinforced composites showed lower tan δ value. Using Arrhenius' equation the activation energy was calculated and found maximum for the composites fabricated by alkali-treated fiber, which shows good fiber/matrix interactions.