Effects Of Shellac And Carbonyl Iron Powder/Carbon Nanotube Microcapsules On The Properties Of Waterborne Coatings On Wood Surfaces

Multi-functional appliances,high-power appliances,etc.have brought more electromagnetic radiation hazards to people’s living environment,posing an undeniable threat to human health.The shellac microcapsules and carbonyl iron powder（CIP）/carbon nanotube（CNTs）microcapsules were used to simultaneously improve the toughness of waterborne coatings,endow them with self-healing effects,enhance electromagnetic absorption performance,reduce electromagnetic wave hazards,and expand the application range of waterborne coatings on wooden furniture surfaces.The main content and results are as follows:（1）Through the orthogonal experiment of L₉（3⁴）,the effects of the content of shellac microcapsules,CIP content,CNTs content,and coating thickness on the elongation at break of the coating were investigated.The results showed that the most influential factor on the elongation at break of the paint film was the content of shellac microcapsules.A single factor experiment was designed with the content of shellac microcapsules as the variable to explore the effect of different shellac microcapsule contents on performance of waterborne coating on the surface of fiberboard.The color difference,hardness and roughness of the coating gradually increased,while the gloss and adhesion of the coating gradually decreased.The impact strength,repair rate and elongation at break of the paint film first increased and then decreased.The coating had poor cold liquid resistance to red ink solution.When the CIP content was 20.0%,the CNTs content was 2.0%,the primer coating thickness was 25μm and the content of shellac microcapsules was 4.2%,the comprehensive performance of the coating was the best.At this time,the color difference of the coating was 1.26,the glossiness at 60°incidence angle was 37.8GU,the adhesion was grade 2,the hardness was 2H,the impact resistance was 15 kg·cm and the roughness was 2.593μm.The elongation at break of the paint film was 8.2%and the repair rate was 24.1%.In this case,the mixed powder of CIP,CNTs,and shellac microcapsules had a theoretical minimum reflection loss of-7.94 d B at 11.8 GHz,and an absorption frequency band less than-5 d B was 8.2 GHz-17 GHz.（2）The CIP absorbing agent was coated with microcapsules to make it better disperse in the coating and improve the toughness of the coating.The range and variance analysis of microcapsule yield and coating rate showed that the key factor affecting the formation of microcapsules was the core-wall ratio.The CIP microcapsules with different core-wall ratios and shellac microcapsules were mixed into waterborne coatings to explore the influence on the properties of waterborne coatings on fiberboard surface.When the addition amount of shellac microcapsules was 4.2%,the core to wall ratio was 0.70:1,and the CIP microcapsule addition amount was 9.0%,the coating performance was the best.At this time,the color difference of the coating was 1.83,the glossiness at 60°incidence angle was 19.3 GU,the adhesion was grade 2,the hardness was 3H,the impact resistance was 17 kg·cm and the roughness was 3.124μm.The elongation at break of the paint film was 16.7%and the repair rate was 17.1%.In this case,the mixed powder of shellac microcapsules and CIP microcapsules with a core to wall ratio of 0.70:1achieved a theoretical minimum reflection loss of-6.53 d B at 15.8 GHz,and the absorption frequency band below-5 d B was 15.3 GHz-16.2 GHz.The minimum theoretical reflection loss slightly increased and the effective absorption frequency band narrowed.（3）In order to reduce the minimum reflection loss of absorbing materials and broaden the absorbing frequency band,the CIP/CNTs microcapsules were prepared by using CNTs modified CIP as the core material.The range and variance analysis of microcapsule coating rate showed that the key factor affecting the formation of microcapsules was the content of CNTs in the core material.By selecting CIP/CNTs microcapsules with CNTs content of 3.0%and 4.6%in the core material and mixing CIP/CNTs microcapsules with shellac microcapsules,the coating was prepared.The results showed that the comprehensive performance of the coating was optimal when the shellac microcapsule content was 4.2%,CNTs content in the core material was 3.0%,and CIP/CNTs microcapsule content was 9.0%.The color difference of the coating was 1.65,the glossiness at 60°incidence angle was 20.6 GU,the adhesion was grade 2,the hardness was 2H,the impact resistance was 16 kg·cm and the roughness was 2.373μm.The elongation at break of the paint film was 12.4%and the repair rate was 34.3%.At this time,the theoretical minimum reflection loss of the mixed microcapsule powder of CIP/CNTs microcapsules and shellac microcapsules is-13.52 d B at 16.2 GHz,and the wave-absorbing frequency band less than-5 d B is 15.3 GHz-18 GHz.（4）In order to further improve the wave-absorbing properties of the water-based coating on the surface of fiberboard without affecting its physical and chemical properties,the effects of the mixed addition methods and coating thickness of shellac microcapsules,CIP microcapsules and CIP/CNTs microcapsules on the coating properties were explored.It was found that the biggest factor affecting the tensile performance of the paint film was the content of CIP/CNTs microcapsules,followed by the content of shellac microcapsules.When the content of shellac microcapsules was 4.0%and the content of CIP/CNTs microcapsules was 7.0%,the comprehensive performance of the coating was the best.The color difference of the coating was1.98,the glossiness at 60°incidence angle was 25.4 GU,the adhesion was grade 2,the hardness was 4H,the impact resistance was 21 kg·cm and the roughness was 1.728μm.The elongation at break of the paint film was 20.1%and the repair rate was 33.9%.The mixed microcapsule powder with 33.3%shellac microcapsule content,8.4%CIP microcapsule content,and 58.3%CIP/CNTs microcapsule content achieved a theoretical minimum reflection loss of-14.28 d B at 17.6 GHz.The absorption frequency bands below-5 d B were 4.3 GHz-8.1 GHz and 13.9 GHz-17.8 GHz,respectively.Compared with adding a kind of the microcapsules,the mixed addition method further widens the electromagnetic absorption frequency band,enhanced the absorption intensity,and achieved better self-healing effect.The research results lay a technical foundation for the application of wave absorbing and self-repairing waterborne coatings on the surface of wood materials.