Mechanical and Self- healing Properties of Latex Coatings Containing Ethyl Cellulose-based Core-Shell Microcapsules

In this work, microencapsulated compounds based on rapeseed oil (RO) core and ethyl cellulose (EC) shell materials with a ratio of RO to EC 70:30 were prepared by solvent evaporation method in two different agitation speeds of 800 and 1400 RPM. Shape and morphology of microcapsules were evaluated using optical microscopy and SEM. The size distribution of microcapsules was evaluated using a particle size analyzer. Mechanical properties of carboxylated styrene/butadiene copolymer latex films containing various levels of oil-filled microcapsules were evaluated using DMTA and tensile strength measurements. Microcapsules with a regular spherical shape 10-45 μm in diameter and 0.65 -1.55 μm in shell thickness were obtained by optimizing oil to EC ratio and agitation speed. The results revealed that the average microcapsule diameter can be controlled by varying mixing speed. DMTA and tensile strength experiments revealed increasing overall mechanical properties of latex films containing oil-filled microcapsules. The released oil materials plasticizing the surrounding latex matrix, and hence restore material properties. Appropriate combination of self-healing properties, mechanical properties and coating appearance; would be achieved with optimization of size and weight fraction of microcapsules within the coating’s formulation. Observation showed that larger particles (between 20-40 μm) had a greater ability to repair the polymer coatings when the proportion of microcapsules to latex was between 0.5 -1 wt %. However, the optimal percentage for smaller particles (under 20 μm) was between 1-2 wt %. The importance of a uniform distribution of microcapsules in the latex films was also established with respect to the mechanical properties.

Keywords:

Self healing Properties , Latex Film , Mechanical Properties , Microcapsule