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Diseases caused by infections are becoming harder to treat as the antibiotics used become less effective. A combination of strategies to develop active biomaterials that enhance antibacterial effects are desirable, especially ones that cause fewer side effects and promote healing properties. The combination of nanotechnology with substances that have intrinsic antibacterial activity can result in the advance of innovative biomedical materials. In this sense, the goal of this work is to provide a summary of natural rubber latex materials obtained from the Hevea brasiliensis tree loaded with metallic and metal oxide nanoparticles. These nanoparticles have unique size-dependent chemical and physical characteristic that make them appropriate for use in pharmaceutical and medical devices, while natural rubber latex is a natural and biocompatible polymer with an intrinsic antibacterial effect. Moreover, we outline here the origin, extraction methods, and composition of natural rubber latex and different techniques for the synthesis of nanoparticles, including physical, chemical, and biological approaches. Finally, we summarize, for the first time, the state of the art in obtaining natural rubber-based materials with metallic and metallic oxide nanoparticles for biomedical applications. [ABSTRACT FROM AUTHOR]

Sandwich composites are materials that have superior properties including low weight, high impact energy absorption and high thermal insulation features, compared to conventional materials. In this study, four different sandwich samples were explored for use in cold storage chambers. The composites were created using an injection molding process with polyurethane foam as the core and different materials (glass fiber reinforced polyester, galvanized steel, aluminum sheets and crimped aluminum) as face materials. Morphological, physical and mechanical properties were evaluated. An inexpensive and nondestructive method was used to determine the thermal behavior of the sandwich panels, and the surface temperature evolution was thermally monitored during the tests. In general, results showed that polyurethane had a homogeneous distribution of size and shape with closed cells, which can improve the retention of the insulating gas. Additionally, the compressive strength of polyurethane within the composites exhibited typical values to be used in specific applications. Thus, the sandwich with galvanized steel exhibited lower flexural strength, which provides more freedom in panel design. The overall heat transfer coefficient of the panels in the form of cubes presented values below the maximum limit requested by ABNT NBR-15457. Finally, the composite galvanized steel/polyurethane/galvanized steel achieved the best performance for use as a thermal insulation material in a cold storage chamber. [ABSTRACT FROM AUTHOR]

The most widely used plasticized polymer is poly(vinyl chloride) (PVC) due to its excellent plasticizer compatibility characteristics. Traditionally, PVC plasticizers belong to the phthalate family; however, they have harmful effects on human health and the environment. In this work, we evaluated the effect of six types of plasticizers (dioctyl phthalate, dioctyl adipate, Lestarflex (a polymeric polyester plasticizer), polycaprolactone, polyester polyol, and 1,2,3-propanetriol triacetate) on the properties of PVC plastisol used in manufacturing shoes and toys. The mechanical properties (hardness, tensile strength, tear strength, and elongation at break) were evaluated before and after accelerated aging tests (in an ultraviolet oven and at 50°C). A thermal study was also carried out using differential scanning calorimetry and thermogravimetric analysis, while possible structural changes during deformation were investigated using the small-angle X-ray scattering technique. In general, the results have shown that in the plasticization and stabilization of PVC, the plasticizer dioctyl phthalate can be replaced by dioctyl adipate or Lestarflex without relevant changes in the final properties of the material, even after accelerated aging. [ABSTRACT FROM AUTHOR]

The effects of three curing systems on rheometric, morphological, physical-mechanical, thermal, and dynamic properties of ethylene–propylene–diene monomer (EPDM) composites was investigated. The influence of thermo-oxidative aging on crosslink density and physical-mechanical properties was studied. Based on a standard composition for application at high temperatures, EPDM formulations with semi-efficient vulcanization systems (ES), efficient vulcanization systems (ED), and peroxide curing systems (EP) were prepared. Experimental results indicated that EPDM compounds cured with efficient vulcanization systems exhibit the highest scorch time with an intermediate maximum torque value at 150°C. The filler dispersion in the elastomeric matrix was greater than 94%; however, the ED formulation showed a more pronounced decrease, with the increase in deformation indicating a greater filler–filler interaction. In comparison with those cured with peroxide and semi-efficient systems, EPDM formulations cured with an efficient system presented better thermal resistance and the crosslink density was sufficient to maintain the mechanical integrity, leading to an intermediate hardness value, tensile strength, modulus, and greater elongation at breaking. In summary, the results indicated that the efficient curing system was the most appropriate to be used in the envelope's manufacture, due to the better performance of the mechanical properties associated with the better resistance to thermal aging. [ABSTRACT FROM AUTHOR]