The biocomposite materials have wide engineering applications ranging from moist to dry atmosphere, from clean to dusty environment and from low to high tempera­ture, thus it becomes important for the noise control specialist to know the effect of temperature on the various physical and chemical properties of the biocomposite. Here some of the thermal properties of the jute-based biocomposite are presented.

6.5.2.1 THERMAL CONDUCTIVITY

The thermal conductivity of jute felt measured using the heat flow meter technique at the facilities of the Indian Institute of Technology Kharagpur as per ASTM C 518 is 0.064 W/m-K in the temperature range from 50°C to 80°C10. The thermal diffu — sivity of the jute felt measured using the laser flash technique as per ASTM E1461 standard was found to be 0.259 mm2/s11.

Very small wrinkles may be observed in the corner basis of the tetrahedron as shown by Fig. 7.15.

FIGURE 7.15

The observed wrinkling defects have been observed for both reinforcement in the case of low blank holder pressures (lower than 1 bar). For higher pressure, the tension of the membrane become more important and a coupling effect72between in­plane shear and tension of the membrane already reported for carbon fabrics prob­ably acts to suppress the wrinkle. However, it is important to apply pressures lower than the appearance limit of the tow sliding.

Shear angle measurements have been carried out using the mark tracking meth­od to investigate the zones where the wrinkles may potentially appear, because it is commonly admitted that wrinkles appears when shear angles are too high. Figure 7.16 shows the shear angles measurements at different locations of Faces B (A to F) and A (G) for reinforcement 1 with orientation 0°.

The results presented in Fig. 7.16 show relative shear angle homogeneity on the whole two faces of the tetrahedron. The magnitude of these angles is not very high and is probably lower than the locking angle (evaluated in Section 3.3) above which wrinkles may appear. Figure 7.17 for the reinforcement 1 shows the measurements of shear angles at the corner basis at the bottom of Edge 1. The measured angles are much higher than the ones recorded on Faces B and A. This therefore explains why wrinkles can be observed on that location and not on the Faces.

Figure 7.18 shows the in-plane shear angles for corner 1 and 2 for orientation 0° for reinforcement 2 with a blank holder pressure of 5 bar. It shows that the shear angles have a tendency to rise as a function of the distance from the central line of the corner. The shear angles are also larger at the bottom of the corner. It is also in­teresting to note that the shear angles measured on reinforcements 1 and 2 are very close despite the fact that the fabric architectures are different. The shape therefore has a tendency to impose the shear angles in the corners.

Epoxy is a large family of resins which represent some of the high-performance resins.106 It is a thermosetting polymer formed from the reaction of an epoxide resin with polyamine hardener.107 Epoxy is one of the best matrix materials for industrial application, due to its excellent properties such as good adhesion, mechanical prop­erties, chemical and heat resistance, low moisture content, little shrinkage, and pro­cessing ease.16107 The outstanding performance of epoxy in terms of adhesive and mechanical properties, and resistance to environmental degradation lead to its wide usage in the aircraft and boat building industry.106 Over the years, there were many studies conducted on SPF-epoxy composites.108114

9.4.5.1 EFFECT OF AGING ON SUGAR PALM FIBER REINFORCED EPOXY COMPOSITE

Tensile and impact tests were conducted by Ali et al.16 on original and aged SPF/ epoxy composite to compare their mechanical properties. An accelerated aged com­posite was obtained by using the standard material age acceleration under ASTM F1980 with 10% error. The parameters used in their investigation were; (a) time of real time aging in a natural environment (70 days), (b) ambient temperature (25 °C), (c) accelerated aging temperature (70 °C), and (d) accelerated aging factor (2.0). Equation 1 and 2 were used to determine the accelerated aging rate and accelerated aging time duration.

Where AAR was accelerated aging rate, AAT was accelerated aging tempera­ture, AT was ambient temperature, Q10 was accelerated aging factor, AATD was

accelerated aging time duration and DRTA was the desires real time aging.16 When the parameters were substituted into the equations, the accelerated aging time (AAT) was 74 hrs. and 10 mins which was equivalent to 70 days of aging in a natural en­vironment.

Aged SPF/epoxy composite manifested superior tensile strength compared to those of the original composite. The tensile strength of the aged composite increased by 50.4%, which indicates that the aging process rendered the composite matrix more compact, yielding a harder and denser composite material. This may happen due to slight increase in specific volume of the epoxy polymer chains and energy was stored within the chains during the heating process. The polymer chains even­tually release the stored energy during the cooling stage (after heating the compos­ite), causing a decrease in the composite specific volume. This phenomenon causes the epoxy polymer chains to become denser and further strengthen the composite bond.108 However, lower tensile modulus of the aged composite was obtained from the tensile test as compared to the original composite. It was evident from their findings that the aged SPF/epoxy composites had very low ductility properties. The resistance towards deformation decreased for the aged composite due to the dense epoxy matrix polymer chains. The impact strength of both composites explicitly shows that SPF/epoxy composites are brittle and that aging has a minimal effect on the impact properties of the composite.108

Table 13.1 summarizes the various treatments conducted in this research project. DDGS were modified by direct treatment with acetic anhydride and maleic anhy­dride solutions. Acetic anhydride and maleic anhydride were obtained from Sigma — Aldrich Chemical Company, St. Louis, MO and used as supplied without further purification. STDDGS and STPW particles were vacuum-oven dried for 24 hr at 80°C. Four hundred grams of filler were boiled in a stirred jacketed reaction ves­sel fitted with a distillation trap at 90°C containing 6 M acetic anhydride/acetone mixture for 24 hrs. In addition, a 5 M acetic anhydride /1 M maleic anhydride/ acetone reaction mixture was also employed. Following incubation, filler materials were filtered, washed three times with acetone, and vacuum-oven dried for 48 hr at 80°C. Hereafter, STDDGS and STPW treated with acetic anhydride (A) or acetic anhydride/maleic anhydride (AM) mixtures will be designated as STDDGS/A and STDDGS/AM, respectively. Weight percentage gains were calculated for the A and AM mixtures to be ~11 and ~12%, respectively.

TABLE 13.1 Weight Percentages in Test Formulations

Composition HDPE MAPE DDGS STDDGS PINEW PW STPW Modifiers

HDPE 100 — — — — — — —

HDPE-MAPE 95 5 — — — — —

To investigate the influence of mixing different fillers to produce an improved composite, STDDGS was mixed with PINEW at various concentrations with and without presence of a 5% maleic anhydride coupling agent (MAPE) (Table 13.1).

The influence of the presence or absence maleic anhydride coupling agent on the physical properties of HDPE-fiUer blends was also investigated (Table 13.1).

Composite blends were extruded with a 27 mm corotating intermeshing twin — screw extruder, with a length/diameter ratio of 40 (Model ZSE-27 American Leis — tritz Extruder Corporation, Branchburg, NJ). The barrel had ten different zones, each 90 mm long, which were controlled at the following temperatures (oC): 100, 160, 170, 190, 200, 200, 210, 210, 205, and 205, respectively. The cord die temperature was set at 200°C. Premixed fillers and HDPE were dry blended in 1 gallon-resalable plastic bags. Materials were then transferred into a single drive feeder (Flex-Tuff Model 306, Schenck/AccuRate, Whitewater, WI) and fed into the extrusion feeder at the rate of 100 g/min. Extruder screw speed was set at 100 rpm. Extruded strands were cooled by immersion in a water bath and then pelletized with a strand pellet­izer (Model 60E, Automatick Plastics Machinery GMbH, Grossotheim, Germany).

Molding was conducted with a 30-ton molding machine (Engel ES 30, Engel Machinery Inc., York, PA) with set point temperatures (°C) for the four zone injec­tion molding barrel set at: feed = 160; compression = 166; metering = 177, and nozzle = 191. The mold temperature was 37 °C. An ASTM test specimen mold was used that included cavities for a ASTM D790 flexural tensile bar (12.7 mm W x 127 mm L x 3.2 mm thickness) and an ASTM D638 Type I tensile bar (19 mm W grip area x 12.7 mm neck x 165 mm L x 3.2 mm thickness X 50 mm gage L). Impact specimen bars were obtained by cutting the flexural specimens in half to 12.7 mm W x 64 mm L x 3.2 mm thickness and notched. The Type I bars were used for the tensile strength property tests. The flexural bars were used to evaluate flexural prop­erties and also used to make impact strength measurements. The Type I bars were used to evaluate changes due to prolonged exposure to water: weight change, color change, and changes in tensile mechanical properties of the composites.

Wheat gluten (WG) is a protein composite found in foods processed from wheat and related grain species, including barley and rye. WG husk is the composite of a gliadin and a glutenin (Fig. 15.4), which is conjoined with starch in the endosperm of various grass-related grains.

The prolamin and glutelin from wheat (gliadin, which is alcohol-soluble, and glutenin, which is only soluble in dilute acids or alkalis) constitute about 80% of the protein contained in wheat fruit.

The gliadin and glutenin components contribute to dough quality either in an independent manner (additive genetic effects) or in interactive manner (epistatic effects). Commercial WG has a mean composition of 72.5% protein (77.5% on dry basis), 5.7% total fat, 6.4% moisture and 0.7% ash; carbohydrates, mainly starches, are the other major

Gliadins are monomeric proteins that can be separated into four groups, alpha-, beta-, gamma — and omega-gliadins. Glutenins occur as multimeric aggregates of high molecular weight (HMW) and low-molecular-weight (LMW) subunits held together by disulfide bonds. In wheat, omega — and gamma-gliadins are encoded by genes at the Gli-1 loci located on the short arms of group 1 chromosomes, while al­pha and beta-gliadin-encoding genes are located on the short arms of group 6 chro­mosomes. LMW glutenins are encoded by genes at the Glu-3 loci that are closely linked to the Gli-1 loci. HMW glutenins are encoded by genes at the Glu-1 loci found on the long arms of group 1 chromosomes. Each Glu-1 locus consists of two tightly linked genes encoding one ‘x’-type and one ‘y’-type HMW glutenin, with polymorphism giving rise to a number of different alleles at each locus.

The gliadin and glutenin components contribute to dough quality either in an independent manner (additive genetic effects) or in interactive manner (epistatic ef­fects). It was suggested that the apparent effects of gliadins on dough quality should be attributed to the LMW glutenins due to the close linkage of the Gli-1 and Glu-3 loci.

The film forming property of hydrated wheat gluten is a direct outcome of its viscoelasticity. Whenever carbon dioxide or water vapor forms internally in a gluten mass with sufficient pressure to partially overcome the elasticity, the gluten expands to a spongy cellular structure. In such structures, pockets or voids are created which
are surrounded by a continuous protein phase to entrap and contain the gas or vapor. This new shape and structure can then be rendered dimensionally stable by applying sufficient heat to cause the protein to denature or devitalize and set up irreversibly into a fixed moist gel structure or to a crisp fragile state, depending on final moisture content.

BNCs are also known as bacterial cellulose, microbial cellulose, or biocellulose. BNCs are microfibrils concealed by aerobic bacteria, such as acetic acid bacteria of the genus Gluconacetobacter, as a pure component of their biofilms. The resulting microfibrils are microns in length, have a large aspect ratio with morphology de­pending on the specific bacteria and culturing conditions. These bacteria are wide­spread in nature where the fermentation of sugars and plant carbohydrates takes place. In contrast to other forms of cellulose, that is, MFC and NCC, materials isolated from cellulose sources, BNC is formed as a polymer and nano material by biotechnological assembly processes from low-molecular weight carbon sources, such as d-glucose. The bacteria are cultivated in common aqueous nutrient media, and the BNC is excreted as exopolysaccharide at the interface to the air. The result­ing form-stable BNC hydrogel is composed of a nanofiber network (fiber diameter: 20-100 nm) enclosing up to 99% water. This BNC is proved to be very pure cel­lulose with a high weight-average molecular weight (MW), high crystallinity, and good mechanical stability. The bio-fabrication approach opens up the exciting op­tion to produce cellulose by fermentation in the sense of white biotechnology and to control the shape of the formed cellulose bodies as well as the structure of the nanofiber network during biosynthesis. The resulting unique features of BNC lead to new properties, functionalities, and applications of cellulose materials.7078

The major ampullate (MA) gland, which is named after its morphological features, represents the most extensively studied silk-producing gland in the spider silk com­munity (Fig. 1.1). From an anatomical perspective, it has been divided into three regions: the tail region, the ampulla and the spinning duct. The tail region is respon­sible for the synthesis of large quantities of silk protein, the ampulla for silk protein storage, and the spinning duct functions to facilitate the conversion of the liquid dope into a solid. Recent studies have pinpointed three different types of epithelial cells that span the tail and ampulla region; these regions are denoted zones A, B and C.2 The MA gland produces silk for the web frame and radii and serves as a lifeline for spiders to move and escape predators (Table 1.1). MA silk evolved long before its use in orb-webs, being used as far back as 350 mya.3 One primary function of dragline silk includes locomotion; however, it is becoming apparent that MA silk performs a variety of other tasks. In particular, biochemical studies have shown that cob-weavers use MA silk to form web scaffolding and gumfooted lines, two impor­tant fiber types that facilitate prey capture.4 In some instances, it has been reported to be present in prey wrapping silk.5 There are essentially three reasons that MA silk has been the most extensively studied: 1) The MA gland represents the largest and easiest structure to identify during microdissection of the different silk-producing glands; 2) MA silk represents the easiest silk type to forcibly remove or collect from a spider during a controlled descent; 3) MA silk has extraordinary mechanical prop­erties, which include its high tensile strength and toughness.

The in-vitro tests of biocompatibility and bioactivity of TiC coatings were studied on the adhesion, growth, maturation, viability, stress adaptation and potential immune activation of osteogenic cells in cultures on these materials. For the cell culture ex­periments, the samples have been sterilized with 70% ethanol, inserted into 24-well polystyrene cell culture plates (TPP, Switzerland; internal well diameter 15.6 mm). These studies were carried out on human osteoblast-like cell line MG-63 (European Collection of Cell Cultures, Salisbury, UK).

The cells have been cultured for 1, 3, and 7 days at 37 °C in a humidified air at­mosphere containing 5% CO2. For the cell culture experiments, glass slides and also the bottom of standard polystyrene cell culture dishes have been used as reference materials. The detailed description of cell seeding was described by Balazsi et al.56 57

The samples have been used for evaluation of cell number and their viability by the LIVE / DEAD viability/cytotoxicity kit for mammalian cells (Invitrogen, Mo­lecular Probes, USA) according to the manufacturer’s protocol. Briefly, nonfixed cells have been incubated for 5 to 10 min at room temperature in a mixture of two of the following probes: calcein AM, a marker of esterase activity in living cells, emitting green fluorescence (excitation/emission ~495/~515 nm), and ethidium homodimer-1, which penetrated into dead cells through their damaged membrane and produced red fluorescence (excitation/emission ~495/~635 nm).

TiC/A:C nanocomposite thin films did not lead to an increase in cell number after 1 day (Fig. 2.19a) in culture in comparison with the control microscopic glass coverslips 56. However, on days 3 and 7 after seeding, the cell numbers on TiC/A:C surface have been found to be similar to PS and significantly higher than that on the microscopic glass coverslips (Fig. 2.19). Harcuba et al. 58 investigated the biological properties of Ti-6Al-4 V alloy after surface treatment by the electric discharge machining (EDM) process using MG63 osteoblast cells. These results could be compared with our results and showed that samples modified by EDM provide a better substrate for the adhesion and growth of human bone-derived cells than the alloy plasma-sprayed withTiO258.

The cell-matrix adhesion involved cell adhesion with many integrin or other adhe­sion receptors of an appropriate type, associated with cell differentiation, and also the formation of a large number of mature cell-matrix adhesion sites.59 The microscopic investigations have been performed on cells stained by immunofluorescence staining. The pi-integrin adhesion receptors have been localized predominantly in the central region of the cells (Fig. 2.20). Vinculin, which formed dot-like structures, has been located on the whole surface of cells in the case of TiC/A:C (Fig. 2.4.7). However, on microscopic glass coverslips, vinculin has been situated mainly at the cell edges. The cells on TiC/A:C displayed larger and more numerous vinculin-containing focal adhe­sions than the cells on microscopic glass coverslips (Figs. 2.20 and 2.21).

Ti based implants are classified as bioinert. Bioinert refers to a material that retains its structure in the body after implantation and does not include any immunologic host reaction. Bioactive materials could be used for modification of the surface that occurs upon implantation. Bioactive refers to materials that direct chemical bonds with bone or even with soft tissue of a living organism. One of most used bioactive materials is a hydroxyapatite. The structure of bioinert TiC /A:C thin films covered by bioactive HAp is shown in Fig. 2.22.

2.5. CONCLUSION

Biomaterials used for implant should posses some important properties in order to long-term usage in the body without rejection. The creation of nanocomposites of ceramic materials with particle size few ten nanometers can significantly improve the bioactivity of the implant and enhance the osteoblast adhesion. The most used bioma­terials are hydroxyapatite, polymer and titanium (Ti).

Hydroxyapatite (HAp) prepared from eggshells are a good candidate as bioma­terial. Nanosized HAp prepared by attritor or ball milling had significantly higher bone formation than the unfilled control at 8 weeks after the operation. The histologic measurements showed that the remaining graft material was much lower in the HAp group. HAp from eggshells could be considered as an economic bone graft material. The results from this animal study cannot be extrapolated to clinical applications; sub­sequent toxicologic assessment and clinical trials would be necessary.

Polymer-HAp composites were successfully manufactured and applied in bone tissue engineering by employing the electrospinning technique. CA-HAp nano scaf­folds were proved to promote favorable adhesion and growth of osteoblasts as well as to stimulate the cells to exhibit functional activity of bone cells. Overall, our studies suggest that both the morphology and structure of the CA-HAp composite scaffolds play important roles in facilitating cell spreading and differentiation and enhance apa­tite mineralization.

The sputtered TiC/A:C nanocomposite thin films were prepared as potential bar­rier coating for interfering of Ti ions from pure Ti or Ti alloy implants. Columnar TiC crystallites with 15-20 nm width have been embedded in 5 nm thin amorphous carbon matrix. MG63 osteoblast cells have been used for in-vitro study of nanocomposites. The 7 day lasting tests showed a higher value of cells on TiC/A:C nanocomposite surface. On the other hand, the cells on TiC/A:C film showed amore spreading ten­dency than the cells on control. The distribution of osteocalcin on microscopic glass coverslip did not reach the intensity of osteocalcin in cells on TiC/A:C films. The initial adhesion, subsequent growth and viability of human osteoblast-like MG63 cells in cultures on different substrates have been studied. From these measurements, no significant differences in the viability of MG63 cells have been found concerning all tested materials.

Based on our observations, the nanosized HAp prepared from eggshells by mill­ing, electrospun CA-HAp nano scaffolds or TiC based thin films are considered as a promising candidate for bone tissue engineering application.

The topological complexity of most acoustical materials necessitates the charac­terization of these materials based on gross properties.13 The physical parameters which affect the acoustic properties of fibrous structures include flow resistance, thickness, porosity, weight of the structure, tortuosity, surface impedance, compo­sition, the geometrical shape of the material, and the presence of air gap or cover

screen.61

Mechanical structures may vibrate during their operations. The air molecules near the structure thus receive the vibration energy and oscillate, and an air-borne sound wave is thus generated. To reduce the intensity of these sound waves, the vibration of the structure needs to be reduced. There exits three important modes of vibration control, namely the stiffness control, the mass control and the damping control. At the resonant frequency of the structure the vibration level and thus the airborne sound can be brought down by increasing the damping, and at frequencies below the resonant frequency the vibration is brought down by controlling the stiffness and at frequencies above the resonant frequency the vibration of the structure is brought down by controlling the mass16.

Damping in a material is usually quantified by few of these related terms like, damping factor, loss factor, decay rate and damping capacity4041. There exit stan­dards for measuring damping42. The damping of the materials also vary with temper­ature and using a Dynamic Mechanical Analyzer (DMA) the same can be measured.

Experimental modal analysis has been done on composite plates with polymer base and coconut fiber to determine the frequency response function between the vibration response and the excitation force. From the measured frequency response function using the half power method the damping factor of the material can be determined4344. It has been reported that polyester composites with 15% coconut coir fiber by volume have high damping ratio44. Polypropylene composites with various natural fibers like kenaf fibers, wood flour, rice hulls and newsprint fibers were developed. The variation of damping with temperature from -60°C to 120°C which were measured using a DMA has been reported. In this measurement a heat­ing rate of 2°C/minute was applied45. Experimental investigations have been made to determine the sound absorption coefficient and the damping loss factors of natu­ral fiber (flax) reinforced polyethylene honeycomb core panels. It is reported that the material constitution, fiber lengths and orientations yield to different behavior of the honeycomb cores46.