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61.
列叙了部分强震前后短期的异常气象情况,探讨了其与强震间的机理,并结合1976年松潘7.2有地震波及汉中地区引起的破坏,讨论了异常天气带来的灾害叠加问题,对编制防震减灾规划和地震短临前兆探索,无疑是有益的。 相似文献
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Maria T. B. Pimenta Antonio J. F. Carvalho Fabiola Vilaseca Jordi Girones Joan P. López Pere Mutjé Antonio A. S. Curvelo 《Journal of Polymers and the Environment》2008,16(1):35-39
Treated sisal fibers were used as reinforcement of polypropylene (PP) composites, with maleic anhydride-grafted PP (MAPP)
as coupling agent. The composites were made by melting processing of PP with the fiber in a heated roller followed by multiple
extrusions in a single-screw extruder. Injection molded specimens were produced for the characterization of the material.
In order to improve the adhesion between fiber and matrix and to eliminate odorous substances, sisal fibers were treated with
boiling water and with NaOH solutions at 3 and 10 wt.%. The mechanical properties of the composites were assessed by tensile,
bend and impact tests. Additionally, the morphology of the composites and the adhesion at he fiber–matrix interface were analyzed
by SEM. The fiber treatment led to very light and odorless materials, with yields of 95, 74 and 62 wt.% for treatments with
hot water, 3 and 10 wt.% soda solution respectively. Fiber treatment caused an appreciable change in fiber characteristics,
yet the mechanical properties under tensile and flexural tests were not influenced by that treatment. Only the impact strength
increased in the composites with alkali-treated sisal fibers. 相似文献
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Majid Soleimani Lope Tabil Satyanarayan Panigrahi Anthony Opoku 《Journal of Polymers and the Environment》2008,16(1):74-82
Recently, investigations have been conducted on the use of natural fibers as reinforcement in low-melting point thermoplastics
to improve mechanical properties of composites. However, due to some limitations of natural fibers, composite formulation
and processing parameters must be controlled to produce a product with improved properties. This study was conducted to investigate
the influence of flax fiber loading, use of compatibilizer and pretreatment on physical and mechanical properties of compression-molded
composite. In this study, untreated and treated (sodium hydroxide-treated and mild-bleached flax fibers) fibers at 15% and
30% of the total product mass were used in formulations. To investigate the effect of compatibilizer on product properties,
maleic anhydride grafted polypropylene (MAPP) was added at 5% by mass in the formulations. After extrusion of composites formulations,
they were formed using compression molding. Results indicated that using flax fiber in composites without pretreatment and
compatibilizer could result into products with inferior physical and mechanical properties; this could be compensated by the
use of a compatibilizer. However, the use of compatibilizer had some negative effects on some other physical properties like
color and melt flow index (MFI). 相似文献
68.
Synthesized hydroxyapatite/clay (HA-C) and hydroxyapatite/pumice (HA-P) composites were used for tetracycline (TC) uptake studies from aqueous solution and their uptake capacities were compared. HA-C and HA-P composites were synthesized by precipitation method and the structures of the synthesized composites were characterized by XRD, SEM and BET analyses. Cation exchange capacities of HA-C and HA-P were found to be 84 meq/100 g and 33 meq/100 g, respectively. The TC adsorption using HA-C and HA-P was studied on batch mode. Various parameters such as contact time, solution pH, initial TC concentration, composite dosage, salinity and temperature were optimized. Langmuir, Freundlich and Dubinin–Radushkevich (D–R) isotherm models were applied to the equilibrium data. The maximum adsorption capacity onto HA-C was found to be 76.02 mg/g and about four times larger than the adsorption capacity of the HA-P (17.87 mg/g). The results indicated that the TC uptake onto HA-C and HA-P composites is mainly by a surface complexation and ion-exchange mechanism which depend on the solution pH. The calculated values of thermodynamic parameters indicated that the TC adsorption is favorable, physicochemical in nature. The sorption process follows pseudo-second-order and intraparticle diffusion kinetic models. The TC adsorption mechanism by HA-C and HA-P has been proposed. 相似文献
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The natural, bio-degradable features and chemical constituents of the sugarcane bagasse (SCB) have been attracting attention as a highly potential and versatile ingredient in composite materials. Eco-friendly and low cost considerations have set the momentum for material science researchers to identify green materials that give low pollutant indexes. Various components of SCB is shown to possess the ability of being applied as raw material for manufacturing of composite materials at multiple levels of properties and performances. Studies on the impacts, performances and applications of SCB in its original condition; transformed forms; treated with appropriate chemicals and/or processes; in combination with materials of distinct properties and manipulation of manufacturing methodologies have been duly considered. This paper attempts to summarize a review of current literature on the extensive studies that have been undertaken in an attempt to explore plausible applications and potentials of SCB for composite material. 相似文献
70.
Jonn A. Foulk Wayne Y. Chao Danny E. Akin Roy B. Dodd Patricia A. Layton 《Journal of Polymers and the Environment》2006,14(1):15-25
Manufacturing composites with polymers and natural fibers has traditionally been performed using chopped fibers or a non-woven mat for reinforcement. Fibers from flax (Linum usitatissimum L.) are stiff and strong and can be processed into a yarn and then manufactured into a fabric for composite formation. Fabric directly impacts the composite because it contains various fiber types via fiber or yarn blending, fiber length is often longer due to requirements in yarn formation, and it controls the fiber alignment via weaving. Composites created with cotton and flax-containing commercial fabrics and recycled high-density polyethylene (HDPE) were evaluated for physical and mechanical properties. Flax fiber/recycled HDPE composites were easily prepared through compression molding using a textile preform. This method takes advantage of maintaining cotton and flax fiber lengths that are formed into a yarn (a continuous package of short fibers) and oriented in a bidirectional woven fabric. Fabrics were treated with maleic anhydride, silane, enzyme, or adding maleic anhydride grafted polyethylene (MAA-PE; MDEX 102-1, Exxelor® VA 1840) to promote interactions between polymer and fibers. Straight and strong flax fibers present problems because they are not bound as tightly within yarns producing weaker and less elastic yarns that contain larger diameter variations. As the blend percentage and mass of flax fibers increases the fabric strength, and elongation generally decrease in value. Compared to recycled HDPE, mechanical properties of composite materials (containing biodegradable and renewable resources) demonstrated significant increases in tensile strength (1.4–3.2 times stronger) and modulus of elasticity (1.4–2.3 times larger). Additional research is needed to improve composite binding characteristics by allowing the stronger flax fibers in fabric to carry the composites load. 相似文献