Lindsey Doyle wasn’t having a good day, and it was just 9 o’clock in the morning. When she got in the lab that morning, she noticed that the material in the glass jar that she had left out overnight had suddenly changed in appearance. Lindsay had pulled the lube emulsion out of a cabinet and placed it on the small oven on her lab bench before she had left for the night. Change in any emulsion formulation is almost always a bad thing. The lube emulsion was a simple formulation that she had thrown together several years earlier, and was her “go to” system for improving the lubricity or slip resistance of the coatings she had developed. The lubricant formulation, which was just water, mineral oil and a short-chain EO surfactant, Tergitol™ 15-S-7, was an opaque white liquid the day before. Now, after sitting overnight, the emulsion had separated into an ugly, water and oil, two-layer heterogeneous system. She had never had a problem with stability of this simple formulation before, but she had usually left her lube emulsion out on the bench top. For some reason her simple formulation had crashed out of solution when left on top of the small oven.
So when she took the call from the very irate customer, she was more distracted and not as helpful as usual. The customer, in a loud, stern tone, with a distinct southern Texas accent, informed her in a not so sweet southern drawl that the 40 drums of aqueous acrylic dispersion that Big Time Paint Co. had shipped only two months before, had a serious problem. The customer had opened up four of the 40 drums, and these drums had changed in appearance and consistency sometime during storage in the South Texas warehouse. The top of the drums were liquid, but when the warehouse foreman had tried to mix the drums using a small bung mixer, the mixer wouldn’t turn. When they opened the top of the drum and poked the liquid with a long wooden boat oar, it appeared that the dispersion had settled in the drum. The customer told Lindsay that they were surprised to discover that all the drums had curdled into white semi-solid that settled in the bottom third of the drum. Lindsay was told that the customer had even tried to pour the four drums into a small tank that allowed for more powerful mixing. The material would not re-disperse. If anything, the mixing with a high-shear agitator only exacerbated the problem, and produced more coagulation and separation of the dispersion components. The customer wanted answers and needed new material, pronto.