| Microencapsulated of phase change materials(MicroPCMs)is a technology not developed until the past 30 years.MicroPCMs can storage a great lot of heat due to its direct and latent heat, which made its special temperature regulating function so that it has greater application potentiality in a lot of special fields.Especially in the textile and clothing applications,they are used much more than before.In this paper,hexadecane and octadecane is the core material of the microencapsulation,and melamine with formaldehyde is as the shell material.A series of MicroPCMs have been prepared by in-situ polymerization,and performances of the Microencapsules are different.Experiments also study the effect of these factors on the performance of microencapsulation,such as emulsifier content and core/shell ratio,etc.The percentages of free formaldehyde in the microencapsulation processes have been measured,and some methods have been discussed to reduce the free formaldehyde emissions.The free formaldehyde content of fabrics with MicroPCMs was measured by AATCC Test Method 112-2006,so that we can analyze the reasonable method to minimize it under standards.The MicroPCMs were analyzed by IR spectra,and images of microcapsules were analyzed by an optical micro-scope and SEM for visual comparison.The properties of phase change, thermal resistance and thermal stability were measured by DSC and TG respectively.The fabric with MicroPCMs were finished by impregnation method,whose value of warm/cool feeling and thermal conductivity washed before and after were also measured.The result of study showed that the factors such as core/shell ratio,emulsion particle size and microencapsulation times would also effect the manufacture of MicroPCMs,except for temperature and pH value.The pre-polymerization temperature should be 65-70℃and pH value should be 9.0.Under emulsifying condition such as using emulsifier of Span60 and Tween60, HLB=10,ratio in water and oil=1:6,speed =1800r/min and time=75min,the most stable phase change material emulsion with relatively small size and lower viscosity was prepared,which in line with the requirements of micro-encapsulation.When using the same content of shell,the smaller emulsion particle size is,the smaller microcapsule particle size is.Compared with MicroPCMs with single shell,MicroPCMs with composite shell will have smoother surface and particle sizes will be more even.Washing the microcapsules with deionized water sufficiently is one of the most effective methods among the other methods reducing the content of free formaldehyde during the microencapsulation processes.The free formaldehyde content of fabric with MicroPCMs can be reduced by decreasing the appropriate adding volume of phase-change microcapsules while ensuring the effect of the phase transition and washing the fabric sufficiently.Through the analysis of DSC and TG,the MicroPCMs with both single core and composite core as well as the MicroPCMs mixed with different cores showed the good performances of phase transition,thermal resistance and thermal stability.From the warm/cool feeling value and thermal conductivity measured,we know that the fabric finished by MicroPCMs has good temperature conditioning function. |
