Reversible thermal gelation of soft semi‐crystalline polyethylene microparticles with surface interactions in squalane

The effect of temperature on the steady‐shear viscosity of a soft semi‐crystalline crosslinked‐polyethylene microparticle suspension in squalane was studied using rotational rheometry. The results show a sharp increase in the viscosity of the system occurring at about 86°C. The magnitude of this spike is dependent on the concentration of the suspension and is reproducible over multiple heating and cooling cycles. This phenomenon has been attributed to the melting of the crystalline regions within the particles, causing them to swell by soaking up squalane. The Mooney equation was used to model the viscosity data based on swelling data obtained from separate experiments. The results showed that the model is inadequate for describing the observed phenomenon, suggesting the possibility of additional interactions existing among the particles. POLYM. ENG. SCI., 2008.