Papers by Keyword: Polypropylene (PP) Fiber

Abstract: In this work, an acrylic-polypropylene grafting copolymer (PP-g-AA) was prepared by 60Co γ-rays irradiation grafting with acrylic acid (AA) onto polypropylene (PP) fiber. The esterification PP-g-AA fiber (PP-g-COOR) was prepared by the esterification of PP-g-AA with C8 alcohol via SOCl2 as the intermediate. The PP-g-COOR fiber was utilized to adsorb and enrich trace dibutyl phthalate (DBP) in water. The results indicated that PP-g-COOR fiber exhibited a good adsorption property of DBP. The adsorption property of PP-g-COOR fiber was greatly enlarged 25 times than the PP-g-AA. The distribution coefficient of DBP on PP-g-COOR fiber depended on the pH values of aqueous phase and the initial concentration of DBP. In general, the PP-g-COOR fiber was better for the adsorption and enrichment of DBP.

Abstract: Tests were carried out to study mechanical properties of hybrid fiber reinforced full lightweight aggregate concrete (HFRFLAC), the hybrid fiber was composed by steel fiber and polypropylene fiber, the expanded-shale and lightweight sand were used as coarse and fine aggregates. The apparent density and strengths in cubic compressive, splitting tensile and flexural tensile states of HFRFLAC were obtained. The results show that the average dry apparent density increases with the increasing cement content, which is much more affected by fraction of steel fiber by volume than mass content of polypropylene fiber; the tensile strengths increase somewhat with the increasing mass content of polypropylene fiber; all of the strengths increase with the increasing fraction of steel fiber by volume, and obvious are the enhancement of tensile strengths; there are somewhat relevance between the effects of polypropylene fiber and steel fiber on mechanical properties of HFRFLAC.

Abstract: The composite board was made of chopped basalt and polypropylene fibers. The manufacturing process included blending, carding, web formation, laminating and compression molding. The tension and bending properties were investigated experimentally. The load - displacement curve of the tensile test revealed that the elastic modulus and maximum vertical load in the longitudinal were far greater than these in the transverse direction; and tensile strengths were far apart in the longitudinal and transverse direction as well. In comparison with the tensile tests, the effect of basalt fiber orientation on the bending modulus and strength were relatively insignificant. In addition, from the micro fibril angle, we also verify that the orientation angle of basalt fiber is an important factor of influence to the mechanical property. In the similar study, the influence hadn’t been seen sufficiently, so this paper provides reference to the actual application of the composite board.

Abstract: This paper made experimental research on the compressive strength, axis compressive strength and splitting tension strength of polypropylene fiber-reinforced concretes at a fiber content of 0.9Kg/m³ in different ages which showed that: in the experiment of compressive strength, the strengths of C20 polypropylene fiber concretes in the ages was lower; the strength of C30 polypropylene fiber concretes in the age of 7 days was lower, the strengths in the ages of 14 days and 28 days were basically equal to; the strength of C40 polypropylene fiber concretes in the age of 7 days was basically equal to and in 28 days was higher than the strengths of ordinary concretes. In the experiment of axis compressive strength, the strengths of C20 polypropylene fiber concretes in the ages were lower; the strengths of C30 polypropylene fiber concretes in the age of 7 days and 14 days were lower and in the age of 28 days was basically equal to; the strengths of C40 polypropylene fiber concretes in the ages were basically equal to the strengths of ordinary concretes. In the experiment of splitting tension strength, the strengths of C20 and C30 polypropylene fiber concretes were lower; the strength of C40 polypropylene fiber concretes in the age of 28 days was basically equal to the strengths of ordinary concretes. Conclusion: the relationships between the strength of fiber concretes and ordinary concretes are correlated to the strength grades of concretes, namely, When the strength degrade of concretes is low, the strength of polypropylene fiber concretes is lower, but the strength reaches closer to or exceeds the strength of ordinary concretes along with the increase of the strength grade of concretes.

Abstract: Early shrinkage of concrete includes plastic shrinkage before the final setting, drying shrinkage during hardening process and autogenous shrinkage. Concrete drying shrinkage which is caused by evaporation is a major factor for the concrete volume change. By ring constrained test and free shrinkage TONCEN test, this paper studies the impact of polypropylene fibers and SRA on the shrinkage properties of concrete at the early age. The test shows that the polypropylene fibers and SRA can significantly reduce the early shrinkage of concrete, and SRA works more evidently than polypropylene fibers.

Abstract: Adding suitable quantity of polypropylene fiber is very effective for controlling plastic crack of cement mortar. During the experience stage, adding quantity of polypropylene fiber is 1.5 kg/m3, and crack rate of mortar is only 7.7%. Theoretical analysis is made for plastic crack mechanism of cement mortar, the results indicate that adding polypropylene fiber improves critical stress of crack expansion in mortar and notably reduces crack of cement mortar.

Abstract: In this study, the fundamental and spalling properties of high-strength concrete were examined, especially when various types and varying content of polymer resin were added. Two types of polymers were used in this study: ethylene vinyl acetate copolymer (EVA-P) and polyvinyl acetate copolymer (PVA-P) as powders and polyvinyl acetate copolymer (PVA-F) and polypropylene copolymer (PP-F) as fibers. Test results showed that the addition of EVA-P and PVA-F to concrete slightly decreased flowability, whereas the addition of PP-F and PVA-P enhanced the viscosity, leading to a remarkable reduction in flowability. The air content of concrete containing EVA-P, PVA-F, and PP-F showed no significant variation. The addition of PVA-P to concrete also caused a slight reduction in compressive strength, whereas the other additives had insignificant effects. After a fire test, the control concrete and concretes with EVA-P, PVA-P, and PVA-F exhibited severe explosive spalling regardless of the dosages. This was because the polymer does not provide sufficient void networks, which is important for vapor evacuation, which enables the release of steam pressure inside the concrete. However, when more than 0.10% of PP-F was added, spalling was effectively prevented. For the residual compressive strength, higher polymer dosage in the concrete produced better results regardless of the polymer type. The powder-type polymers did not contribute to preventing spalling in concrete subjected to fire. This is due to their geometric shape and high melting point. It is concluded that a high aspect ratio and low melting point is critical during polymer selection to prevent spalling in high-strength concrete.

Abstract: Polypropylene fibers were dyed with Disperse dyes Blue 2B in Supercritical Carbon Dioxide at different temperature, pressure and time. The K/S value were determined and the effect of as temperature, pressure and dyeing time on the dyeing behaviours of disperse dyes on Polypropylene fibers were discussed. It was found that with the increase of dyeing temperature and pressure, the K/S value increased gradually, and dyeing effect was best after the fiber was dyed at 120 °C, 28 MPa for 20 min.

Abstract: In the process of pull out testing polypropylene fiber, the performance of bonding of tested and untested objects has been microscopically analyzed; both the interface of polypropylene fiber-cement-based material, the hole morphology of cement-based material after the polypropylene fiber being pulled out by force and the condition after the polypropylene fiber being pulled out of concrete-based material are observed. Attachment phase analyses of the surface of the polypropylene fiber and cement-based transverse cracks after the polypropylene fiber being pulled out have both confirmed the fact that the performance of bonding of the polypropylene fiber-cement-based material can effectively transmit the outer force borne by the polypropylene fiber and that the performance of bonding of the polypropylene fiber-cement-based material is better.

Abstract: Mixing three different fiber composites into concrete specimens respectively, compressive strength, splitting tensile strength and flexural strength for fiber-reinforced concrete was done. The results show that the strengths of fiber reinforced concrete are improved to some extent. Due to the addition of fiber, the fiber concrete bears some of the force in tension, thus the time from the initial crack to damage is more prolonged comparing with normal concrete. Fiber concrete specimens did not get the collapse and lower intensity suddenly. Compared with normal concrete, the maximum increase of the reinforced concrete with steel fiber SQB -32 (Ⅱ) is listed, which compressive, tensile and flexural strength are increased by 30%, 40% and 24%, respectively.