Time of flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) have been employed to study the interfacial interaction between polymeric methylene diphenyl diisocyanate (PMDI) and aluminium produced by the deposition of a thin PMDI layer on the aluminium, in order to improve adhesion and/or abhesion performance.When the PMDI concentration increases, the intensity ratio fragments indicative of the reaction product with water (m/z = 106 u: C 7 H 8 N + ) to that of isocyanate group (m/z = 132 u:C 8 H 6 NO + ) decreases. A very thin MDI layer on oxidised aluminium samples exhibits lower 106/132 ratio than degreased samples as a result of less hydroxide/hydroxyl spices on the surface. This suggests that water reactions occur both at the surface of PMDI and at the PMDI/aluminium interface. The variation of the PMDI chemistry has also been studied by exposing PMDI treated samples to the air for various periods of time (a few hours to 14 days), in order to assess the reaction of the PMDI surface and PMDI/aluminium interface. At the interface, the yield of reaction with water is limited because of the finite amount of hydroxyl groups on the aluminium surface, and the water reaction is completed in a short period of time.However, the PMDI surface continues to react with water from the atmospheric. This methodology was also used to establish the presence of specific interactions at the PMDI/aluminium interface, and a fragment indicative of covalent bond formation between PMDI and aluminium (AlCHNO 3 -) is observed at the interface.2

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The interactions of polymeric methylene diphenyl di‐isocyanate (pMDI) and a model Fe–Cr alloy have been studied by X‐ray photoelectron spectroscopy (XPS) and time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). Films of two different thicknesses have been investigated: one with an extremely thin pMDI layer in which the interfacial chemistry can be probed directly and a thicker one in which sputter profiling using cluster ions is necessary to expose the interface chemistry for direct analysis. Multivariate analysis (MVA), using principal component analysis (PCA) and nonnegative matrix factorisation (NMF), has been used to identify specific ions associated with the interfacial region of the ToF‐SIMS sputter depth profile and chemical species from the XPS sputter depth profile. As an unsupervised method, this avoids an unconscious bias on the part of the analyst. Specific ions associated with pMDI interactions with both Fe and Cr allow the proposal of two complementary reaction mechanisms, supported by the XPS data. A range of cluster ions is used in this investigation, but the bulk of the work used argon clusters for the XPS depth profiles and Buckminster Fullerene projectiles for the ToF‐SIMS analyses. To ensure that such data were directly comparable, the ToF‐SIMS sputter profiles were repeated in a different system of the same type using argon cluster ions.

The interfacial interactions between rigid polyurethane foam (RPUF) and aluminium have been studied to understand adhesion mechanisms. Three different blowing

Summary The penetration behaviour of isocyanate-based wood resins was evaluated using x-ray microscopy. Aspen wood pieces were bonded together in a controlled manner. These were embedded in a methacrylate-based resinand thin sections were prepared, cut from the transverse face of thewoodcomposite. X-ray images of these sections were prepared at several selected x-ray energies to allow the isocyanate, cellulose, lignin and the embedding agent distributions to be mapped. The isocyanate resin was found to penetrate deeply into the wood. The resin enters large cell lumen, and wicks along the inner cell wall surfaces. The resin accesses connected cells via connecting pits, which become filled with the resin. The affinity of the isocyanate to the inner surfaces of the large cells is probably due to the hydrophobicity of these surfaces. Isocyanate resins do not penetrate into the smaller parenchyma and tracheid cells and indeed do not even wet the inner surfaces of these cells where isocyanate entry has been allowed due to damage of the cell at the macroscopic surface of the wood. If isocyanates penetrate into the wood-cell walls of the large cells, the concentration in the cell walls has been determined to be less than 2%of the bulk concentration. This lower limit is the sensitivity limit imposed by photon statistics in the data.