Fabrication and amplification of Rhodamine B‐doped step‐index polymer optical fiber

A step‐index polymer optical fiber (SI POF) containing Rhodamine B in poly(methyl methacrylate) (PMMA) has been fabricated by a preform technique. Fluorescence of different fiber lengths were observed and discussed. A high gain (23 dB) for a SI POF with 60‐cm length, 400‐μm diameter was obtained. The Rhodamine B content of the doped SI POF is 5 ppm‐wt. The signal wavelength providing the highest gain for a 60 cm SI POF is around 630 nm, and the optimum fiber length is about 60 cm at 10 kW launched pump power. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 681–685, 2004     

Effect of carbon fiber surface functional groups on the mechanical properties of carbon-carbon composites with HTT

The present investigation describes the quantitative measurement of surface functional groups present on commercially available different PAN based carbon fibers, their effect on the development of interface with resol-type phenol formaldehyde resin matrix and its effect on the physico-mechanical properties of carbon-carbon composites at various stages of heat treatment. An ESCA study of the carbon fibers has revealed that high strength (ST-3) carbon fibers possess almost 10% reactive functional groups as compared to 5.5 and 4.5% in case of intermediate modulus (IM-500) and high modulus (HM-45) carbon fibers, respectively. As a result, ST-3 carbon fibers are in a position to make strong interactions with phenolic resin matrix and HM-45 carbon fibers make weak interactions, while IM-500 carbon fibers make intermediate interactions. This observation is also confirmed from the pyrolysis data (volume shrinkage) of the composites. Bulk density and kerosene density more or less increase in all the composites with heat treatment up to 2600 °C. It is further observed that bulk density is minimum and kerosene density is maximum upon heat treatment at 2600 °C in case of ST-3 based composites compared to HM-45 and IM-500 composites. It has been found for the first time that the deflection temperature (temperature at which the properties of the material start to decrease or increase) of flexural strength as well as interlaminar shear strength is different for the three composites (A, B and C) and is determined by the severity of interactions established at the polymer stage. Above this temperature, flexural strength and interlaminar shear strength increase in all the composites up to 2600 °C. The maximum value of flexural strength at 2600 °C is obtained for HM-45 composites and that of ILSS for ST-3 composites.     

Liquid spouting of pulp fibers in a conical vessel

Pulp fibers can be spouted in water in a conical vessel. The entities which are spouted are fiber flocs rather than individual fibers. Synthetic fibers, which do not flocculate, cannot be spouted. For comparison, rigid spherical particles were spouted with water in the same conical vessel. Liquid spouting of rigid particles was similar to gaseous spouting. For pulp spouting, the minimum spouting velocity is proportional to the mass of fibers in the bed and inversely proportional to the diameter of the inlet. For rigid particles, the minimum spouting velocity is proportional to the height of the bed and inversely proportional to the square of the diameter of the inlet. A model for the minimum spouting velocity was developed for pulp spouting.     

热处理前后丙烯腈／溴乙烯共聚纤维的热性能和阻燃性能研究

分析了热处理前后丙烯腈／溴乙烯共聚纤维的热性能与溴乙烯含量、升温速率或热处理时间的关系，并对纤维的阻燃性与溴含量或热处理时间关系进行了研究。结果表明，溴含量的增加或热处理时间的延长对热稳定性和阻燃性的提高有较大影响，而且经热处理后纤维的阻燃性与溴无关。     

UV‐radiation–induced preirradiation grafting of methyl methacrylate onto lignocellulose fiber in an aqueous medium and characterization

The preirradiation method of grafting has been established by ultraviolet radiation. Methyl methacrylate (MMA) was grafted onto jute fiber in an aqueous medium. The variation of graft weight with UV‐radiation time, monomer concentration, and reaction time was investigated. The conversion of monomer into homopolymer and graft copolymer was evaluated. The graft weight passes through a maximum value (～ 122%) with UV‐radiation time. The optimum value of the monomer concentration was evaluated for maximum degree of grafting. Graft copolymerization of MMA onto lignocellulose fiber significantly increases the elongation at break (～ 65%) compared to that of the “as‐received” sample. However, a linear decrease on breaking load was observed with the increase of graft weight. The estimation of degree of grafting was achieved using an IR technique by correlating band intensities with the degree of grafting. Considering the water‐absorption property, the grafted sample showed a maximum up to 61% decrease in hydrophilicity compared to that of the as‐received sample. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1667–1675, 2004     

Ageing studies of pineapple leaf fiber–reinforced polyester composites

This experimental study evaluated the water absorption characteristics of pineapple leaf fiber (PALF)–polyester composites of different fiber content. The degree of water absorption was found to increase with fiber loading. The mechanism of diffusion was analyzed and the effect of fiber loading on the sorption kinetics was studied. The diffusion coefficient was calculated and found to increase with fiber content. Studies were also made to correlate water absorption with the cross‐sectional areas of the specimens. The effects of ageing on the tensile properties and dimensional stability of PALF polyester composites were studied under two different ageing conditions. Ageing studies showed a decrease in tensile strength of the composites. The composite specimens subjected to thermal ageing showed only a slight deterioration in strength. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 503–510, 2004     

Study of needle penetration speeds on frictional properties of nonwoven webs: A new approach

H1 technology needlepunching machinery is one of the recent developments in the needleloom technology. H1 technology needlepunching nonwoven machinery has been effectively utilized to develop a set of nonwoven substrates at different punching rates. The effect of needlepunching speeds on the frictional properties of H1 technology polyester nonwoven webs is reported in this article. The frictional properties of nonwoven webs have been characterized using a simple normalized friction factor. In addition, the surfaces of the nonwoven substrates were scanned using scanning electron microscopy. The results show that for the three different penetration rates studied there seems to be a marginal difference in the frictional properties. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3626–3631, 2003     

纤维增强刚玉耐火材料制备及其显微结构

采用国产硅酸铝纤维和多晶莫来石纤维，利用传统的工艺制备了纤维增强氧化铝基耐火材料。研究了纤维的种类、加入量对其性能的影响，进行了显微结构的初探。结果表明，纤维引入耐火基质中能显著地提高材料的强度，且随着纤维加入量的增加试样强度大幅度增加。试样中的纤维经1500℃烧后仍交错分散在基质中。     

UV photo‐stabilization of tetrabutyl titanate for aramid fibers via sol–gel surface modification

Tetrabutyl titanate was used as sol–gel precursor of a nanosized TiO₂ coating to improve the photo‐stability of aramid fibers. The nanosized TiO₂ coating was characterized by XRD and XPS. The influence of the TiO₂ coating on photo‐stability of aramid fibers was investigated by an accelerated photo‐ageing method. The photo‐stability of aramid fiber showed obvious improvement after coating. After 156 h of UV exposure, the coated fibers showed less deterioration in mechanical properties with the retained tensile strength and elongation at break greater than 36 and 50% of the original values, respectively, whereas the uncoated fibers degraded completely and became powdery. SEM analysis showed no significant surface morphological change on the coated fiber after the exposure, while some latitudinal crack fractures appeared on the uncoated aramid fiber. The effect of the nanosized TiO₂ coating was also well demonstrated by examining the difference of distributions of C1s in XPS deconvolution analysis on the surface of uncoated/coated fibers with increasing UV exposure time. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3113–3119, 2007     

Mechanical properties of biorenewable fiber/plastic composites

Plastic fiber composites, consisting of polypropylene (PP) or polyethylene (PE), and pinewood, big blue stem (BBS), soybean hulls, or distillers dried grain and solubles (DDGS), were prepared by extrusion. Young's modulus, tensile and flexural strengths, melt flow, shrinkage, and impact energy, with respect to the type, amount, and size of fiber on composites, were evaluated. Young's moduli under tensile load of wood, BBS, and soybean‐hull fiber composites, compared with those of pure plastic controls, were either comparable or higher. Tensile strength significantly decreased for all the PP/fiber composites when compared with that of the control. Strength of BBS fiber composites was higher than or comparable to that of wood. When natural fibers were added there was a significant decrease in the melt flow index for both plastic/fiber composites. There was no significant difference in the shrinkage of all fiber/plastic composites compared to that of controls. BBS/PE plastic composites resulted in higher notched impact strength than that of wood or soybean‐hull fiber composites. There was significant reduction in the unnotched impact strength compared to that of controls. BBS has the potential to be used as reinforcing materials for low‐cost composites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2484–2493, 2004