•Polyester concrete with waste cotton fibers from Blue-Jeans was elaborated.•The effects of gamma radiation on compressive and flexural properties were studied.•The highest mechanical performance is ...obtained with 1 wt% of waste cotton fibers.•Irradiation dose of 300 kGy provides the highest mechanical values.•Mechanical improvements were related with SEM, FT-IR and XRD analyzes.
Currently, the consumer tendency causes that the garments are dismissed more quickly, which generate increment of textile waste, such as Blue-Jeans. In this work, polyester concrete with waste cotton fibers was elaborated, and a novel treatment by gamma irradiation was carried out. The results show up to 40% improvement on the compressive strength, as well as 7% on the flexural strength. Additional improvements for irradiated concrete were obtained, when 300 kGy of irradiation dose was applied. Modifications on the surface, chemical structural and crystallinity of irradiated waste cotton fibers, were related with improvements on the mechanical properties of concrete.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
This paper presents the results of an experimental program to investigate the effect of temperature on the performance of epoxy and unsaturated polyester polymer mortars (PM). PM is a composite ...material in which polymeric materials are used to bond the aggregates in a fashion similar to that used in the preparation of Portland cement concrete. For this purpose, prismatic and cylindrical specimens were prepared for flexural and compressive tests, respectively, at different temperatures. Measurements of the temperature-dependent elastic modulus and the compressive and flexural strength were conducted using a thermostatic chamber attached to a universal test machine for a range of temperatures varying from room temperature to 90 ºC. The flexural and compressive strength decreases as temperature increases, especially after matrix HDT. Epoxy polymer mortars are more sensitive to temperature variation than unsaturated polyester ones.
The mechanical behavior of polymer concrete reinforced with textile trimming waste was investigated. Two series of polymer concrete formulations were studied, with different resin/sand (i.e. ...binder/fine aggregate) weight ratios. In each series, recycled textile chopped fibers at 1 and 2% of the total weight was used. Flexural and compressive tests were performed at room temperature and load vs. displacement curves were plotted up to failure. In the study, both the influence of fiber content and resin/sand weight ratio were considered relative to the behavior of polymer concrete reinforced with textile fibers. A decrease in properties was observed as function of textile fibers content. When specific properties were considered, this tendency was kept. However, higher textile fibers content lead to a smoother failure, unlike brittleness failure behavior of unreinforced polymer concrete.
•Polymer mortar with waste Tetra Pak from beverage containers was elaborated.•The effects of gamma radiation on compressive and flexural properties were studied.•The highest mechanical performance is ...obtained with 1wt% of Tetra Pak particles.•The lower gamma dose provides the highest compressive strength.
In this work, composites based on polyester resin and silica sand were elaborated. Partial substitution of silica sand by waste Tetra Pak particles from discarded beverage containers was carried out, namely 1, 2, 4 and 6% by weight. As is well known, Tetra Pak packaging have six layers: four of polyethylene, one of cellulose and one of aluminum. Modified composites were irradiated with gamma rays at doses from 100 to 500kGy in order to improve the mechanical properties of composites through a better interfacial coupling between the matrix and Tetra Pak particles caused by the irradiation process. The results shown an improvement of 15% on the compressive strength and 16% on the flexural strength, when 1% of Tetra Pak particles and irradiation dose of 100kGy were used. Higher compressive and flexural deformation was also observed (until 34% higher); therefore a ductile material was obtained, which is not common for these kinds of composites. By increasing the irradiation dose to 200kGy and concentration higher than 2% of waste Tetra Pak particles, mechanical properties of the composites decreased considerably.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The object of this study was to evaluate the flexural strength of glass fiber reinforced polyurethane composites under variable displacement rates. Flexural tests have been conducted at a range of ...displacement rates included 0.2, 2, 20, 100, 200, 1000 mm/min. Specimens with identical geometry have been used in all the tests. This particular composite has viscoelastic behavior with both elasticity modulus and ultimate flexural strength being strongly dependent of the displacement rate. Results showed that, both the flexural modulus and the ultimate flexural strength are increased with the increasing in the displacement rate.
•Polymer concrete with waste cellulose from Tetra Pak packaging was elaborated.•The effects of gamma radiation on compressive and flexural properties were studied.•The highest mechanical performance ...is obtained with 2 wt% of waste cellulose from Tetra Pak.•The lower gamma dose provides the highest compressive strength.•Improvements on the compressive and flexural strength were obtained at irradiation dosages of 100 and 200 kGy.
Addressing the environmental problems caused by waste generated by Tetra Pak packaging, in this work, polyester based composites with 80% of polyester resin and 20% of silica sand were elaborated; where the silica sand was partially replaced by recycled cellulose from waste Tetra Pak containers at concentrations of 1, 2, 4 and 6% by weight. Both recycled cellulose and composite specimens were subjected to ionizing radiation process by using gamma rays. The results show improvements on the mechanical properties (compressive and flexural strength as well as modulus of elasticity) of the composites when they are irradiated at 100 and 200 kGy. Such improvements can be related with the structural modifications caused by gamma irradiation on the cellulose fibers, including changes in the morphology and the crystallinity; which were analyzed through to SEM, IR and XRD techniques.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The research of natural fiber composites is growing due to the fact that the green materials combine low weight with good mechanical properties. Curaua fiber arises as a competitive natural fiber due ...to its abundance, low cost and a variety of applications. In this work, different weight fractions of Curaua fiber were used in order to obtain this natural composite material. Specimens of Curaua/Epoxy composites were tested in tensile and in flexion to observe the quasi-static mechanical properties and its physical properties due to temperature variation were evaluated by Dynamic Mechanical Analyses (DMA) analyses. An increase in fiber quantity showed an increase in both the modulus and the strength, leading to a stiff and less ductile material. The results also showed an increase in the viscoelastic stiffness of the epoxy matrix by the incorporation of Curaua fibers. The interaction between Curaua fibers and epoxy matrix affects segmental mobility of the epoxy chains.
Mechanical properties of castor oil polymer mortars Reis, João Marciano Laredo dos; Motta, Eduardo Pereira
Materials research (São Carlos, São Paulo, Brazil),
09/2014, Volume:
17, Issue:
5
Journal Article
Peer reviewed
Open access
In the last years, ecological concerns have resulted in the interest to substitute petroleum-based materials by renewable resources-based ones. Natural oils constitute an excellent alternative for ...the development of natural composites. The aim of this work is to evaluate the use of natural polymer, manufactured from castor oil, as substitute to synthetic, epoxy and polyester, in polymer mortars matrices, with particular regards to compressive, flexural and fracture properties. Mechanical properties of castor oil polymer mortars are similar to epoxy based ones and significantly higher than polyester polymer mortars with improved flexural properties and less brittle failure.
The thermomechanial properties of polymeric nanocomposites are related to the quality of the adhesion between matrix and nanoparticle. Since the adhesion is related to the nature of the materials and ...the surface available for chemical, electrostatic and mechanical interactions among these materials, weak bonding forces between alumina (inorganic) and polymer matrices (organic) were expected. Furthermore, using nanoparticles with greater diameters means that the specific surface area reduction will have an adverse impact on the adhesive process. For epoxy matrices reinforced with alumina nanoparticles, different volume fractions and sizes were observed by differential scanning calorimetry (DSC): a relation between the glass transition temperature (Tg) and the nanoparticle size. This observation was tested by dynamic mechanical analysis (DMA) and the cross-link density was calculated. In addition, the thermal stability enhanced by alumina addition to organic resins and the quality of the adhesion was observed by thermogravimetric analysis (TGA).
In patients with myelodysplastic syndrome (MDS), bone marrow cells have an increased predisposition to apoptosis, yet MDS cells outcompete normal bone marrow (BM)-- suggesting that factors regulating ...growth potential may be important in MDS. We previously identified v-Erb A related-2 (EAR-2, NR2F6) as a gene involved in control of growth ability.
Bone marrow obtained from C57BL/6 mice was transfected with a retrovirus containing EAR-2-IRES-GFP. Ex vivo transduced cells were flow sorted. In some experiments cells were cultured in vitro, in other experiments cells were injected into lethally irradiated recipients, along with non-transduced bone marrow cells. Short-hairpin RNA silencing EAR-2 was also introduced into bone marrow cells cultured ex vivo.
Here, we show that EAR-2 inhibits maturation of normal BM in vitro and in vivo and that EAR-2 transplant chimeras demonstrate key features of MDS. Competitive repopulation of lethally irradiated murine hosts with EAR-2-transduced BM cells resulted in increased engraftment and increased colony formation in serial replating experiments. Recipients of EAR-2-transduced grafts had hypercellular BM, erythroid dysplasia, abnormal localization of immature precursors and increased blasts; secondary transplantation resulted in acute leukemia. Animals were cytopenic, having reduced numbers of erythrocytes, monocytes and granulocytes. Suspension culture confirmed that EAR-2 inhibits granulocytic and monocytic differentiation, while knockdown induced granulocytic differentiation. We observed a reduction in the number of BFU-E and CFU-GM colonies and the size of erythroid and myeloid colonies. Serial replating of transduced hematopoietic colonies revealed extended replating potential in EAR-2-overexpressing BM, while knockdown reduced re-plating ability. EAR-2 functions by recruitment of histone deacetylases, and inhibition of differentiation in 32D cells is dependent on the DNA binding domain.
This data suggest that NR2F6 inhibits maturation of normal BM in vitro and in vivo and that the NR2F6 transplant chimera system demonstrates key features of MDS, and could provide a mouse model for MDS.
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