On the bases of the diffusion mechanism of small molecules in polymers

fine crosslinkable LDPE was prepared using a method of solid-liquid diffusion through which uniform blending additives with LDPE could be realized and small molecules such as antioxidants and crosslink agent could be diffused into interior section of LDPE pellets from their surface.The solid-liquid diffusion techniques were optimized through analyzing crosslinking enthalpy and specific absorption strength and examining diffusion rate of additives into LDPE under different diffusion conditions by using DSC and FTIR.The results show that time

temperature and molecular structure are the main factors affecting diffusion.It is found that crosslinking enthalpy seems to be the same for the core and shell of LDPE under the conditions of diffusion time being 14 h and temperature being 80C

or being 24 h and 60℃.These phenomena imply that dicumyl peroxide (DCP) has diffused into the interior part of the LDPE pellet; Moreover

content of dilauryl thiodipropionate (antioxidant DLTP) in core and shell of LDPE approaches equal after it diffuses at 80℃ for 24 h

while diffusion rate of n-octadecyl -(3

5-di-tert-butyl-4-hydroxyphenyl)propionate (antioxidant 1076) is remarkably lower than that of DLTP under the same conditions.Furthermore

the content of antioxidant 1076 in core of LDPE is merely half of that in the shell.It is suggested that the reason for this is due to its larger volume than that of DLTP.