Surface modification of ultra‐high‐molecular‐weight polyethylene. II. Effect on the physicomechanical and tribological properties of ultra‐high‐molecular‐weight polyethylene/poly(ethylene terephthalate) composites

We performed surface modification of ultra‐high‐molecular‐weight polyethylene (UHMWPE) through chromic acid etching, with the aim of improving the performance of its composites with poly(ethylene terephthalate) (PET) fibers. In this article, we report on the morphology and physicomechanical and tribological properties of modified UHMWPE/PET composites. Composites containing chemically modified UHMWPE had higher impact properties than those based on unmodified UHMWPE because of improved interfacial bonding between the polymer matrix and the fibers and better dispersion of the fibers within the modified UHMWPE matrix. Chemical modification of UHMWPE before the introduction of PET fibers resulted in composites exhibiting improved wear resistance compared to the base material and compared to unmodified UHMWPE/PET composites. On the basis of the morphological studies of worn samples, microploughing and fatigue failure associated with microcracking were identified as the principle wear mechanisms. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

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     

Relationship between oxidative stability of vitamin E and production of fatty acids in oils during microwave heating

Effects of microwave heating on the oxidative stability ofd-tocopherols were studied in relation to the production of fatty acids in oils. During microwave heating, the stability of tocopherols decreased in the orderδ>β>γ>α. This order did not depend on the types of ethyl esters of fatty acids or oils present. But, the shorter the chainlength and the lower the degree of unsaturation of the fatty acid ethyl esters, the greater was the reduction in amount of individual tocopherols. A similar tendency was observed when tocopherol-stripped vegetable oils, with equimolar mixtures of tocopherols added, were treated under the same conditions. The reduction in tocopherols became greater with increasing levels of free fatty acids.     

An analysis of transport phenomena for multi-solid particle systems at higher reynolds numbers by a standard karman—pohlhausen method—I Momentum transfer

Using the concentric spheres free surface model and a standard 4th polynomial Karman—Pohlansen method, the dimensionless tangential stress distribution, and the dimensionless pressure distribution around a solid sphere in a swarm, and the viscous, form and total drag coefficient for multi-solid particle systems were computed numerically at higher Reynolds numbers. The void function obtained from the drag coefficient for multiparticle system was comparative to the experimental data. The friction factor for multi-particle systems so computed agreed with the experimental data of packed and distended beds.     

Preparation and properties of deep dye fibers from poly(ethylene terephthalate)/SiO2 nanocomposites by in situ polymerization

In this study, poly(ethylene terephthalate) (PET)/SiO₂ nanocomposites were synthesized by in situ polymerization and melt‐spun to fibers. The superfine structure and properties of PET/SiO₂ fibers were studied in detail by means of TEM, DSC, SEM, and a universal tensile machine. According to the TEM, SiO₂ nanoparticles were well dispersed in the PET matrix at a size level of 10–20 nm. The DSC results indicated that the SiO₂ nanoparticles might act as a marked nucleating agent promoting the crystallization of the PET matrix from melt but which inhibited the crystallization from the glassy state, owing to the “crosslink” interaction between the PET and SiO₂ nanoparticles. The tensile strength of 5.73 MPa was obtained for the fiber from PET/0.1 wt % SiO₂, which was 17% higher than that of the pure PET. The fibers were treated with aqueous NaOH. SEM photographs showed that more and deeper pits were introduced onto PET fibers, which provided shortcuts for disperse dye and diffused the reflection to a great extent. According to the K/S values, the color strength of the dyeing increased with increasing SiO₂ content. It is found that the deep dyeability of PET fibers was improved greatly. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

湿式空气氧化法处理乙烯废碱液装置的技术改造

针对中国石化齐鲁石化公司烯烃厂乙烯装置废碱液处理系统在试运转过程中存在的问题,通过分析原因,提出并实施改进工艺的相关措施,得到一组适宜的工艺操作参数,保证了废碱液湿式空气氧化装置的稳定运行。