Advanced Green Composites Reinforcements

chichi's version from 2018-02-28 02:40

Section 1

Question Answer
Biocompositesvegetable fibers + agricultural or petroleum based resins
Vegetable fibersnaturally occurring composites of cellulose fibrils in a lignin and hemicellulose matrix
Advantages of vegetable fibers:low density, easy availability, low cost production, good specific properties, non-abrasive nature, non-toxic, fully biodegradable
Reduces weight reduction of composites up to ____30%
Applications of Vegetable Fibers:Automotive and transport industry, packaging or engineering packaging, consumer products, building and construction industries
Challenges with Vegetable Fibers:High moisture absorption, low thermal stability, poor wetting and poor adhesion to synthetic resins like compatiliers, surface modification techniques, acetylation, graft copolymerization and other techniques

Section 2

Question Answer
Structure of vegetable fibers:fibrils, lignin, lumen
Fibrilseach fiber bundle of individual cylindrical cells
Ligininglue like substance that joins fibrils and cellulose; the bonding agent for the cellulose-hemicellulose system--a contributor to the low thermal resistance of VF. Due to its composition at low temperatures
Lumencauses the density of the fiber to be low and act as an acoustic and thermal insulator
Mechanical properties of vegetable fibers are determined by the...celllulose-content, microfibrillar angle and fibril or cell size
Fibers with high lignin content have been observed to have a small diameter and hence are more.....flexible

Section 3

Question Answer
Components of vegetable fibers:cellulose, hemicellulose, lignin, pectin, and waxes
Celluloseprovides rigidity, tensile and flexural strength; has a flattened oval cross-section
Hemicellulosealmost no contribution to stiffness and strength
Ligninprovides compressive strength and stiffness to the cell wall of the fibers; degradation at low temperatures; thermoplastic behavior (Tg=90oC, Tm=170oC)
Pectinprovide flexiblity to the fibers
Waxesprotect the integrity of the fiber

Section 4

Question Answer
Properties and compostion of the fibers depen upon:the part of the plant from which they are obtained, age of the plant, harvesting location, season
Sisal fibersLeaf fibers; plants produce 200 to 250 leaves before flowering, and each contains 700-1400 fiber bundles; structural fiber shows horse shoe shape the other one is known as arch fiber. Fiber diameter: 200 microns
Kenaf Fibersfibers are obtained from bast of the stem of the kenaf plant, which grows up to a 6 m tall and has woody base. Fiber bundle diameter: 700-800 microns
Jute fibersone of the most common VF. Fibers are obtined from the bast of the plant; fiber diameter: 14-20 microns
Ramie fibersobtained from the stem of the fiber; fiber diameter: 50 microns
Cotton lint fibers45 microns in fiber diameter, obtained from the fruit of species known as Gossypium

Section 5

Question Answer
Flax fibersobtained from the bast of linum usitatissimum; fiber diameter is unknown
Curaua fiberslike pineapples but too small for food. Fibers are extracted from leaf. Fiber diameter: 49-100 microns
Bagasse fibersresidue of sugar and alcohol from sugarcane, fiber diameter: 490 microns
Banana fibersobtained from the tropical fruit plants. Fiber diameter: 5 microns
Pineapple fiberobtained from the tropical fruit plants. Fiber diameter: 5 microns
Hemp fibersobtained from cannabis stem plant. Fiber diameter: 17 microns

Section 6

Question Answer
Advantages of Synthetic fibers:low moisture absorption, low property variability, costant cross-section, dimension (length and diameter) can be controlled
Disadvantages of Synthetic fibers:high energy requirements during productioin, not biodegradable, toxic
Polypropylene a crystalline commodity polyolefin. Can be prepared in highly crystalline forms, with high molecular weights and low densities; has high melting point
Polypropylene is converted to fibers by using a __________________________________, followed by a drawing step to orient the molecules and crystallites in the fibers. Fiber diameter: unknownmelt spinning process
Basalt fibersvolcanic rock and be found in North America and Eastern Europe. Fiber diameter: 10-15 microns
Glass fibers one of the most common reinforcements. the raw material for their production is silica sand

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