Daoyun Song

An instrumented mixer setup for making tackifier dispersions used to make pressure-sensitive adhesives

Water-based pressure-sensitive adhesives (PSAs) are made by combining a tackifier dispersion and a polymer latex. During the process of making the tackifier dispersion, the system initially forms a water-in-oil emulsion, and then inverts to an oil-in-water one as more water is continuously added with constant agitation. To better understand the process, an instrumented mixer setup was constructed to simulate the manufacturing process, and agitation was provided by an inner impeller and an outer impeller. Several variables were monitored in situ. They are the electrical resistance of the emulsion, torque exerted on the inner impeller, agitation speeds of both impellers, power consumption of both impellers and the flow rate of feeding water. Our measurements showed that torque reached a maximum at phase inversion, and this was verified by direct measurements of viscosity during the process. Simultaneously electrical resistance measurements monitored the chemical changes as well as phase inversion. Experiments showed that under a certain low water feeding flow rate, there appeared to be an intermediate agitation speed at which the phase inversion occurred the earliest. This, from the industrial standpoint, is really favorable due to both time and energy efficiency. Furthermore, this intermediate agitation speed also corresponded to a better quality product. All this information may be used for optimizing this process in the future.

The use of thermosets in the building and construction industry

Abstract Thermosets, or cross-linked plastics, and their fiber-reinforced composites have been progressively replacing, either entirely or partially, traditional construction materials. Among the major reasons for this gradual shift away from traditional material usage are property advantages such as low density; low maintenance and life-cycle cost; excellent thermal, sound, and electric insulation; and reduced degradation and oxidation, as well as potentially long service life. The main applications of thermosets and thermoset matrix composites in building and construction include adhesives and sealants, thermal insulation, roofing, flooring, piping, bridge structures, cementing, and repair and rehabilitation of civil structures, and these are addressed in detail in this chapter.

Relating Viscosity Changes to Phase Inversion during the Synthesis of Tackifier Emulsions

An instrumented mixer, with multi‐stage inner and outer impellers which rotate in opposite directions, was built. Tackifier emulsions were synthesized under conditions of different water feeding rates and jacket temperatures, but all at a constant impeller speed. In each case, the point of phase inversion was identified with the help of torque and electrical resistance measurements. The recorded torque data were also used to calculate the emulsion viscosity by comparison with similar data for a Newtonian fluid at the same agitation speed and the same total volume. These computations formed an input to models available in the literature for predicting the onset of phase‐inversion. It was found that the experimental results could be explained by an equation proposed by Utracki.