Failure Investigation
In investigating any matter concerning glue or adhesive failure, it is important to fully understand the chemical composition of an adhesive and the materials being glued, this is achieved through measuring their physical properties, and comparing this data with known data for the adhesive and the materials being glued.
The chemical analysis of the materials being glued and the adhesive itself, are determined using Fourier Transform Infrared Spectroscopy (FT-IR).
Our advanced chemical analysis of adhesive, and surface analysis of the bonding surfaces through digital microscopy can determine if there is any batch-to-batch variation in adhesive raw materials or the surface of the materials being glued, as our case study below will show.
Very often, the adhesive specified for a manufacturing or building application, differs from that called up by the purchasing manager or surveyor / architect.
Often, due to various reasons, the adhesive manufacturer may change the formulation by way of altering the raw material composition by varying the amounts of raw material or using a different raw material altogether. Commonly seen issues typically originate from the misuse of the adhesive or incorrect surface preparation of the materials being glued.
The Problem: A manufacturer of vehicle advertising decals was buying a two-component polyurethane adhesive which was used to bond the advertisement to the van body. It was soon evident that several business owners were unhappy with freshly applied advertising as after three weeks exposure to wind and rain, the decals were losing their colour and delaminating.
The Process: Our laboratory was contacted, and we dispatched a materials engineer to commence the investigation. This process involved inspecting the decals adhering to the van, inspecting the delaminated decals, and removing samples of the adhesive for analysis. In parallel, the adhesives manufacturer supplied our laboratory with a tin of each adhesive component.
Using Fourier Transform Infrared Spectroscopy (FT-IR) , we were able to determine the comparative composition of both adhesive batches and search the resulting spectra against reference spectra from our libraries. FT-IR works by exciting chemical bonds with infrared light, with the different chemical bonds while in this excited state, absorbing light energy at frequencies which are unique to the various bonds.
The Result: Our comparative FT-IR analysis showed that the adhesive samples supplied to our laboratory by the adhesive manufacturer, contained a sterically hindered phenolic antioxidant that protects the decals from thermo-oxidative degradation due to sunlight. The customer supplied suspect adhesive did not, obviously an adhesives manufacturing error. The adhesives manufacturer performed their own independent analysis of the adhesive and reached the same conclusions. Within two months, there was a financial settlement.
Adhesives manufacturers, Specifiers, Purchasing Managers, Sales Agents, Production Managers, Building Contractors, Surveyors and Solicitors.
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