As mentioned above, abaca fiber is considered as the strongest natural fiber and is obtained from leaves (petioles) which are composed of elongated and slim cells (Umali and Brewbaker 1956). Classified as a hard fiber like coir, sisal, and hene — quin, it is highly prized for its exceptional mechanical (tensile) strength, flexibility, underwater durability, buoyancy, and long fiber length. These properties are due to its high Runkel ratio, i. e., the ratio of two times the fiber cell wall thickness over the fiber cell lumen width. It has been found that the fiber has higher tensile strength than its synthetic counterparts like nylon and rayon and that it is rotting resistant with its specific flexural strength almost equal to glass fiber (Moreno 2001; Bledzki et al. 2008). Moreover the lustrous and colored nature of the fiber makes it a pre­ferred natural fiber. Chemically the abaca fiber is composed of cellulose, pectin, and lignin of which the lignin content is as high as 15 % in addition to significant quanti­ties of ketones, triglycerides, o’-hydroxy-fatty acids (C22-C28), monoglycerides, fatty alcohols, and esterified derivatives of p-hydroxycinnamyl acids (ferulic acid;

4- hydroxy-3-methoxycinnamic acid and p-coumaric acid; 4-hydroxycinnamic acid) containing long-chain alcohols (C20-C28). It has also been found to contain diglyc­erides, steroid hydrocarbons, R-hydroxy-fatty acids, sterol esters, and glycosides in minor quantities (del Rfo et al. 2004; del Rfo and Gutierrez 2006). The excellent tensile strength and exceptional under water durability of abaca fibers has led to their usage in the production of many useful industrial and domestic products. The abaca fiber is used for making ships’ ropes, fishing lines, and fishing nets. It also finds their usage in the production of power transmission ropes as well as in well­drilling cables besides being used for production of cordage for naval and marine vessels. The durability and flexibility of abaca ropes is evident from the fact that a 1 in. (2.5 cm) abaca rope requires at least 4 metric tons (8,800 lb) to get broken (Borneman and John 1997). Moreover, the high-quality fiber obtained from abaca provides an excellent material for paper and pulp industry where it is processed into a variety of paper products like bank notes, security papers, cigarette papers, and filter papers. In textile industry, it is used in the manufacturing of bags, table mats, carpets, furniture fillings, and sausage casings besides being used in the production of lightweight but strong fabrics (from inner fibers without spinning) for hats, gar­ments, and shoes. The finest quality of abaca is Lupis and Sinamay. It has been estimated that the global consumption of abaca fiber accounts for about 80 % in the production of speciality paper products and about 14 % in cordage products while the remaining 6 % in other usages. The applications of abaca fibers can be summa­rized under the following headings (FIDA 2009; Moreno and Protacio 2012):

1. Paper andpulp industry: Filter paper, Cigarette paper, sausage skin, base paper, currency paper, envelopes, book binders, parchment paper, special art paper, adhesive tape paper, lens, vacuum cleaner bag, electrolytic condenser paper, high grade decorative paper, time cards, optical lens wiper, X-ray negative, oil filter, etc. hand-made paper like sheets, multi-purpose cards, balls, decorative items (flowers, photo frames, table clock, and lamp shades)

2. Fabrics and fiber crafts; bags, rugs, carpets, wallets/purses, placemats, door mats, fishing nets, special fabrics like Sinamay, dagmay, and pinukpok in addi­tion to coasters, wallpapers and baskets, some non-woven fabrics like diapers, gowns, etc.

3. Furnishing and household construction items: Furniture fillings, carpets, rugs, and mats. Tiles for roofs and floor, hollow blocks, fiber boards, etc.

4. Fuel: Musafel

5. Miscellaneous applications: Insulators for wires and cables, components of automobiles (particularly in reinforced form), preparation of wigs

The modern technology involves the use of abaca-reinforced polymers to make them more applicable for various purposes. The main focus is the use of thermoset­ting or thermoplastic matrices like polyesters or polypropylene (Shibata et al. 2002, 2003; Ochi 2006; Teramoto et al. 2004; Bledzki et al. 2007; Hadi et al. 2011) which led to the use of abaca fibers (reinforced) in under floor protection or passenger cars. This application involves a combination of abaca-reinforced polypropylene thermo­plastic and the technique has been patented by Daimler Chrysler’s researchers (Bledzki et al. 2006) and the manufacturing process has been initiated by Rieter Automotive, Switzerland. The experimental analysis of abaca-reinforced polypro­pylene polymer at various fiber lengths employing different methodologies (mixer — injection molding, mixer-compression, and direct compression process) has also revealed that increase in fiber length leads to an increase in the tensile or flexural properties with the effective method of reinforcement being mixer-injection pro­cess. Not only abaca, but the fibers obtained from other related members like Musa acuminate or Musa sapientum have been used to reinforce polypropylene to yield a valuable composite fiber (Faria et al. 2006; Bledzki et al. 2008). It has been sug­gested that the increases or enhancement of the durability or tensile strength of composite fibers is due to the changes in the Melt Flow Index (MFI) which can be altered by changing the level of three important variables like abaca fiber (length and composition), maliec anhydride (concentration), and the impact modifier (Hadi et al. 2011). The use of these natural fiber-reinforced green composites offers many advantages over the synthetic counterparts like dependency on renewable raw mate­rial, low production cost, specific mechanical strength, energy-efficient manufactur­ing, eco-friendly (low CO2 emissions), and more importantly biodegradability (Cao et al. 2006; Pervaiz and Sain 2003). The abaca fiber has been used to reinforce furan resin (a condensate of furfuryl alcohol produced from agricultural residues like corn cobs or rice hulls) to produce a green composite. The furan resin, being resistant to many acids, alkalis, or solvents, on reinforcing with cellulosic abaca fiber therefore provides an excellent and eco-friendly material for various industrial applications (Tumolva et al. 2009). It has been reported that the abaca fiber-reinforced PP (poly­propylene) composite has high tensile strength, high flexural strength, and good acoustic resistance besides being resistant to moulds, rot or UV damage and cost — effective (Proemper 2004). Moreover, comparison of abaca-reinforced PP compos­ite with other natural fiber-reinforced composites likes jute-PP composite and flax-PP composite has revealed its superior flexural strength and damping properties compared to other composites despite the fact that jute-reinforced PP composite showed higher tensile strength. Furthermore, the use of coupling agent (MAH-PP; maliec anhydride) has been found to significantly improve the tensile as well as flexural strength of abaca-PP composite (Bledzki et al. 2007). Similar investigations on the improvement in tensile strength and water absorption capacity of abaca — reinforced epoxy composites have also been made where the results have confirmed the efficacy of plasma treatment over conventional sodium hydroxide treatment. Plasma treatment exposure for 2.5 min has been found to result in 92.9 % improve­ment in tensile strength and reduction in water absorption capacity of the fiber epoxy-composite and has been attributed to increase in compatibility between abaca fiber and the epoxy matrix (Paglicawan et al. 2013) . Moreover, the heat-treated abaca-reinforced starch based biodegradable resin has also been prepared whose tensile strength has been found to be comparable to glass fiber-reinforced plastics (Takagi 2011). Abaca fibers are also blended with metallic threads and polyester to put them in multiple uses (FIDA 2012).