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Polyurethane Adhesives
Published in A. Pizzi, K. L. Mittal, Handbook of Adhesive Technology, 2017
Dennis G. Lay, Paul Cranley, Antonio Pizzi
Methylene diphenyl diisocyanate (MDI) is used where high tensile strength, toughness, and heat resistance are required. MDI is less volatile than TDI, making it less of an inhalation hazard. The acidity levels in MDI are very low, typically in the order of 0–10 ppm, so the trace base levels in the polyols are much more critical in prepolymer production than with TDI. The structure of MDI is shown in Figure 11.18. There are several commercial suppliers of MDI that typically supply grades with 98% or better 4,4′ isomer. MDI is a solid at room temperature (melting point 38°C, 100°F), requiring handling procedures different from those for TDI. MDI should be stored as a liquid at 46°C or frozen as a solid at −28°C to minimize dimer growth rate. MDI reacts faster than TDI, and because the NCO groups in MDI are equivalent, they have the same reactivity, in contrast to TDI. MDI is used in packaging adhesives, structural adhesives, shoe sole adhesives, and construction adhesives.
Effect of solvent used for isocyanate primer on interphase formation
Published in The Journal of Adhesion, 2021
Meanwhile, 4,4-methylene diphenyl diisocyanate (MDI) was used for the isocyanate compound solution. MDI is a component that is often included in commercial primers and is believed to contribute to improving adhesive strength.[12] The chemical structure of MDI is depicted in Figure 4. Four solvents – 2-butanone, acetone, chloroform, and toluene – were used for preparing the isocyanate solution. Four kinds of solutions were prepared by diluting MDI to 0.5 wt.% with each solvent. Then, each solution was applied to the epoxy coating using a spin coater. The conditions of the spin coater were 3000 rpm for 30 s. If the epoxy matrix contained moisture, the moisture in the matrix would have reacted with the isocyanate in the MDI. To avoid this problem, the epoxy matrix had to be dried in a desiccator for at least 72 h at 23°C and 1% relative humidity (RH) or less before applying the MDI solution. Figure 5 illustrates the preparing process of sample which was considered actual direct glazing process as Figure 2. Table 1 outlines an MDI solution option. After applied each MDI solution, Interphase formations were evaluated.
Heating behavior and adhesion performance of induction-heated multilayered thermoplastic polyurethane adhesive film
Published in The Journal of Adhesion, 2020
Taegyu Lm, Yongsung Kwon, Seungyong Choi, Minyoung Shon, Hokyoon Jeon, Sangtaek Oh, Guni Kim
The Methylene diphenyl diisocyanate (MDI) and polyester polyol(Mw; 2000 g/mol) based TPU adhesive was supplied by Juwon Tech, South Korea (JW-6) and methyl ethyl ketone (MEK) was purchased from Aldrich, USA as the solvent. Ni particles 70 nm in size were purchased from Green Resource (South Korea). A TPU adhesive solution with 20 wt.% MEK was prepared. To prepare TPU adhesive films, known contents of Ni particles were added to the TPU adhesive solution, followed by mixing with a planetary centrifugal mixer. After mixing, in order to determine the effects of Ni particle content on the heating behavior, 200 μm-thick TPU adhesive films were prepared using a solution casting method by adding nickel particles of 10, 15, 20, 30, 40, 50, and 60 phr, respectively. Additionally, to confirm the effects of the multilayered TPU adhesive films with different nickel particle core contents, TPU adhesive films were fabricated with thicknesses of 200, 100, 65, and 50 μm by adding nickel particles of 20, 40, 60, and 80 phr, respectively. Then, 100, 65, and 50 μm-thick TPU films were placed in the center between TPU films without nickel particles, and combined using a heating roller, resulting in a 200 μm-thick TPU film, as shown in Figure 1 and Table 1. The nickel particle content in the prepared TPU films was maintained at 20 phr considering the total adhesive film thickness of 200 μm.
Glove permeation of chemicals: The state of the art of current practice—Part 2. Research emphases on high boiling point compounds and simulating the donned glove environment
Published in Journal of Occupational and Environmental Hygiene, 2020
Diisocyanates (isocyanates), including methylene diphenyl diisocyanate (MDI), are the primary reactive components of spray polyurethane foam (SPF) insulation. Five common disposable garment materials (disposable latex gloves [0.07 mm thickness], nitrile gloves [0.07 mm], vinyl gloves [0.07 mm], polypropylene coveralls [0.13 mm], and Tyvek coveralls [0.13 mm]) were tested by Mellette et al. (2018). These materials were cut into small pieces and assembled into a permeation test cell system and coated with a two-part slow-rise SPF insulation. Glass fiber filters (GFF) pretreated with 1-(9-anthracenylmethyl)piperazine) were used underneath the garment to collect permeating isocyanates. GFF filters were collected at specific time intervals between 0.75 and 20.00 min and subsequently analyzed using liquid chromatography-mass spectrometry (LC-MS). The cumulative permeated concentration of total isocyanate, including phenyl isocyanate and three MDI isomers, was measured over the test time. The estimated BT, average permeation rate, and standardized breakthrough time (SBT) at the estimated 0.1 µg/cm2/min permeation rate were also determined. Typical isocyanate loadings were in the range of 0.900–15 µg MDI/cm2. Each type of glove material had an observed average permeation rate well below the ASTM F739 SBT. Disposable latex gloves displayed the greatest total isocyanate permeation rate (4.11 ng/cm2/min), followed by the vinyl and nitrile gloves, respectively. Nitrile gloves also showed the lowest cumulative permeation.