The Parallel Plate Flow Cell Predicts The Adsorption Performance Of The Microcapsules On A Specific Surface

Perfume-filled microcapsules have been used as h igh value additives in personal-care and house-hold products.In order to release perfume oil after laundry processes the loading and retention of perfume-filled microcapsules on fabric surfaces are critical.The loading and retention of perfume-filled microcapsules is related to the adhesion of microcapsules to the target surfaces.Therefore,it is significant to study the adhesion properties of microcapsules to specific surfaces.The parallel plate flow chamber?PPFC?is simple in design,flexible in oper ation,low in cost,and has good compatibility.It has been used to study the adhesion properties of microparticles?such as microspheres,cells?on specific surfaces.However,this technique characterized adhesion properties based on the remaining area or number of the investigated targets.There is no publication to use the parallel plate flow chamber to calculate adhesion force directly based on the flow chamber experiments.It will be significant if we can used the PPFC to predict the adhesion force bet ween microparticles and the targeted surfaces directly,which may develop a new technique to measure adhesion force in the micro and nano scale.In this work,we are trying to use the parallel plate flow chamber to predict the adhesion between microcapsule s and glass slides.At first,melamine formaldehyde?MF?microcapsules containing hexyl salicylate?HS?as a core material were prepared by in-situ polymerization;and then a self-designed parallel plate flow chamber?PPFC?was constructed and it was used to investigate the adhesion of microcapsules on glass slide by calculating the remaining area to validate its feasibility.After that,the force or the torque balance on the microcapsules which is deposited on the glass surface in the flow chamber were ca lculated based on the mechanisms through which microcapsules were removed,and the mathematical model to calculate adhesion force under each removal mechanism s were established.By using the model,the most possible removal mechanism was predicted and the influences of the related parameters such as the location of the microcapsules,the flow rate,the density of microcapsules and the friction coefficient on the minimum radius and the critical interfacial energy under each onset of removal motion were predicted.At last,experiments were designed to observe the removal of single microcapsules and the adhesion force of single microcapsule s on glass slides were calculated by using the model.The main conclusions are as follows:1.The melamine formaldehyde-hex yl salicylate microcapsules were prepared by in situ polymerization.The microcapsules were in sphere shape and the diameter of them were under 50?m and between 5¹0?m in wet and dry conditions.FTIR,UV and TG analyses indicated the hexyl salicylate were encapsulated successfully.2.The self-assembled parallel plate flow chamber was validated to study the adhesive behavior of microcapsules on glass slide s.For flow chamber experiments,the microcapsules'appropriate concentration range was from 0.30 wt.%to 0.50 wt.%;the settling time of microcapsule was 10 minutes;the flow rate was between 30 ml/h and 100 ml/h(3.70×10^-33 m/s¹.23×10^-2 m/s);and the time for water flow running was 3 minutes.3.By analyzing the forces interacting on the microcapsule including the gravity force,the buoyancy force and the adhesion force under a laminar flow in the flow chamber,a mathematical model to calculate the adhesion force under the lifting,sliding and rolling removal mechanisms was established based on the force and torque balance.4.The model predictes the prepared microcapsules in the parallel plate flow chamber is most likely to be removed by rolling from the glass slides.The minimum radius and critical interfacial adhesion energy is a function of the location of the microcapsules,the flow rate,the density of microcapsules and the friction coefficient.5.Experiments were designed to obtain the critical flow rates of single microcapsules which were removed by the water flow in the flow chamber.Integrating with their radius and location,the model calculated the adhesion forces of single microcapsules on the glass s lides.The calculated adhesion force was 1.60n N¹3.99n N,which is consistent with the value reported by using AFM to measure adhesion force of microcapsules.Therefore,the established model is reliable.It is potential to be a new technique to predict adh esion in micro or nano scales.