99,212 research outputs found
Fire retardant foams developed to suppress fuel fires
Heat insulating polyurethane foam retards and suppresses fuel fires. Uniformly dispersed in the foam is a halogenated polymer capable of splitting off hydrogen halide upon heating and charring of the polyurethane
The effect of postmastectomy radiation therapy on breast implants. Material analysis on silicone and polyurethane prosthesis
The pathogenic mechanism underlying capsular contracture is still unknown. It is certainly a multifactorial process, resulting from human body reaction, biofilm activation, bacteremic seeding, or silicone exposure. The scope of the present article is to investigate the effect of hypofractionated radiotherapy protocol (2.66 Gy Ă— 16 sessions) both on silicone and polyurethane breast implants.Silicone implants and polyurethane underwent irradiation according to a hypofractionated radiotherapy protocol for the treatment of breast cancer. After irradiation implant shells underwent mechanical, chemical, and microstructural evaluation by means of tensile testing, infrared spectra in attenuated total reflectance mode, nuclear magnetic resonance, and field emission scanning electron microscopy.At superficial analysis, irradiated silicone samples show several visible secondary and tertiary blebs. Polyurethane implants showed an open cell structure, which closely resembles a sponge. Morphological observation of struts from treated polyurethane sample shows a more compact structure, with significantly shorter and thicker struts compared with untreated sample. The infrared spectra in attenuated total reflectance mode spectra of irradiated and control samples were compared either for silicon and polyurethane samples. In the case of silicone-based membranes, treated and control specimens showed similar bands, with little differences in the treated one. Nuclear magnetic resonance spectra on the fraction soluble in CDCl3 support these observations. Tensile tests on silicone samples showed a softer behavior of the treated ones. Tensile tests on Polyurethane samples showed no significant differences.Polyurethane implants seem to be more resistant to radiotherapy damage, whereas silicone prosthesis showed more structural, mechanical, and chemical modifications
Quantification and Visualization of Fungal Degradation of Polyurethane Foam in Homes
People spend 90% of their time in the indoor environment including homes. Homes contain many exposures that can cause harm to human health, and one harmful exposure potentially comes from the degradation of polyurethanes. This deterioration of the polymer causes the release of a carcinogenic compound called 2,4-diaminotoluene (2,4-DAT). Polyurethane foam is a common household material and is used to make many items such as mattresses, couches, insulation, and carpet backing. It is uncertain if growth of fungi on this foam can cause biodegradation to occur, which could potentially result in the release of 2,4-DAT. The goal of this study is to better understand under what conditions one common fungal species, Aureobasidium pullulans, degrades polyurethane foam. We tested the effects of nutrient availability, foam age, and relative humidity levels on the ability of Aureobasidium pullulans to degrade polyurethane foam. The effects of nutrient availability on fungal degradation were evaluated by incubating polyurethane foam with different agars and comparing weight loss of foam samples as a result. The effects of foam age were tested by obtaining 2 foam types; one new and one already used in a home and incubating them to compare weight loss as a result. The effects of relative humidity (RH) on fungal degradation of foam were evaluated by incubating foam at varying equilibrium relative humidity (ERH) levels and performing quantitative polymerase chain reaction (qPCR) to quantify fungal growth. Polyurethane foam incubated with Aureobasidium pullulans was observed under a scanning electron microscope (SEM) in order to visually observe the growth of fungi on polyurethane foam. The ideal conditions for fungal degradation were foam type 1 with an additional carbon source and high RH level. The peak weight loss of foam from fungal degradation was found to be 56% and fungal growth was highest at 100% ERH. Spore chains and fruiting bodies were observed via microscopy wrapped around the foam after incubation indicating Aureobasidium pullulans can grow and reproduce on polyurethane foam given appropriate conditions. This information can be used in the future to prevent fungal degradation of polyurethane foam and potentially decrease carcinogen exposure.OSU OUR&CI Undergraduate Research Apprenticeship ProgramOSU College of Engineering Research Distinction ScholarshipNo embargoAcademic Major: Environmental Engineerin
Storage-stable foamable polyurethane is activated by heat
Polyurethane foamable mixture remains inert in storage unit activated to produce a rapid foaming reaction. The storage-stable foamable composition is spread as a paste on the surface of an expandable structure and, when heated, yields a rigid open-cell polyurethane foam that is self-bondable to the substrate
Rheological and Mechanical Gradient Properties of Polyurethane Elastomers for 3D-Printing with Reactive Additives
Polyurethane (PU) elastomers with their broad range of strength and elasticity are ideal materials for additive manufacturing of shapes with gradients of mechanical properties. By adjusting the mixing ratio of different polyurethane reactants during 3D-printing it is possible to change the mechanical properties. However, to guarantee intra- and inter-layer adhesion, it is essential to know the reaction kinetics of the polyurethane reaction, and to be able to influence the reaction speed in a wide range. In this study, the effect of adding three different catalysts and two inhibitors to the reaction of polyurethane elastomers were studied by comparing the time of crossover points between storage and loss modulus G′ and G′′ from time sweep tests of small amplitude oscillatory shear at 30°C. The time of crossover points is reduced with the increasing amount of catalysts, but only the reaction time with one inhibitor is significantly delayed. The reaction time of 90% NCO group conversion calculated from the FTIR-spectrum also demonstrates the kinetics of samples with different catalysts. In addition, the relation between the conversion as determined from FTIR spectroscopy and the mechanical properties of the materials was established. Based on these results, it is possible to select optimized catalysts and inhibitors for polyurethane 3D-printing of materials with gradients of mechanical properties.DFG, 414044773, Open Access Publizieren 2019 - 2020 / Technische Universität Berli
Characterization of graphite polyurethanes composite from renewable based oils
This thesis aims to evaluate the characterization of graphite polyurethane composite
from renewable based oils. Virgin cooking oil (VCO) as a renewable resource is the
main substance in fabricating the renewable polyurethane (PU) and its graphite as
called polyurethane graphite (PG). The fabricating sample have two methods that is
open casting and heat press method. PU and PG with different percentage of graphite
as filler were investigated for structural, morphological, physical and mechanical
properties that going through a several testing including Optical Microscope (OM),
Scanning Electron Microscope (SEM), Ultraviolet-visible (UV-Vis), Fourier
Transform Infrared (FT-IR), Density Test, Tensile test and cross-link density. The
renewable polyurethane is namely as PU and polyurethane graphite is namely as
PG2, PG4, PG6, PG8, PG10 with subscript numbers indicate the weight loading of
graphite content was varied in the renewable polyurethane from 2, 4, 6, 8, and
10wt%. The result of SEM and OM showed that the graphite particles are randomly
distributed and homogeneously scattered well in the PU due to interconnected
interface within the matrix of polymeric composites. UV- Vis technique is used to
characterize the absorption, transmission and reflectivity of the PU and PG’s
otherwise the FT-IR is used for determine the composition and characterize the
polymer structure of PU and PG’s. As expected, the mechanical properties of
composites proven that the addition of graphite can change the matrix properties of
PU to improve modulus and consequent lowered the tan delta with respected of
increasing the temperature. The calculated cross-linked density of PU and PG
composites revealed the increment of graphite particle loading gives highest result of
cross-linking and this is due to the PG10 is the highest graphite content and the
highest value of storage modulus, highest value of tensile strength and the highest
value of young modulus. Therefore, the result shows the renewable polymer graphite
composite is suitable to be used in various composites applications
Polyurethane spray coating of aluminum wire bonds to prevent corrosion and suppress resonant oscillations
Unencapsulated aluminum wedge wire bonds are common in particle physics pixel
and strip detectors. Industry-favored bulk encapsulation is eschewed due to the
range of operating temperatures and radiation. Wire bond failures are a
persistent source of tracking-detector failure. Unencapsulated bonds are
vulnerable to condensation-induced corrosion, particularly when halides are
present. Oscillations from periodic Lorentz forces are documented as another
source of wire bond failure. Spray application of polyurethane coatings,
performance of polyurethane-coated wire bonds after climate chamber exposure,
and resonant properties of polyurethane-coated wire bonds and their resistance
to periodic Lorentz forces are under study for use in a future High Luminosity
Large Hadron Collider detector such as the ATLAS Inner Tracker upgrade
Exploratory study on the effects of novel diamine curing agents and isocyanate precursors on the properties of new epoxy and urethane adhesives
The effects of novel aromatic diamine structures on the adhesive properties of epoxy and polyurethane adhesives were studied. Aromatic diamines based on benzophenone and diphenyl-methane isomers were evaluated as curing agents for epoxy resins and benzophenone and diphenyl-methane based diamine isomers were evaluated as curing agents for polyurethane adhesives. Polyurethane adhesives were prepared based on m, m prime-diisocyanato-diphenyl-methane and m, m prime-diisocyanato-benzophenone. The m, m prime-diisocayanato-diphenyl-methane based adhesive had properties comparable to state-of-the-art adhesives. The m, m prime-diisocyanato-benzophenone based adhesive was extremely reactive
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