Study On Barrier And Active Packaging Properties Of Nylon 12/Polyvinyl Alcohol Mixture

Excellent oxygen barrier properties of polyamide 12?PA12?/poly?vinyl alcohol??PVA?(PA12_xPVA_y^BFz)blends were prepared by melt-blending PA12 with varying amounts of PVA resins with varying degrees of polymerization(i.e.PVA^BF05,PVA^BF08and PVA^BF14).The oxygen permeation rates and average volumes of free-volume-cavities?V_f?of PA12_xPVA_y,^BF05PA12_xPVA_y ^BF08and/or PA12_xPVA_y^BF14series blown films reduced to a minimal value,when their PVA contents reached a corresponding optimal value at 37.5,33.3 and 23.1wt%,respectively.Moreover,the minimal oxygen permeation rate and V_f value obtained for the best prepared PA12_xPVA_y ^BFzblown films reduced considerably with the further decrease in degrees of polymerization of PVA resins.The oxygen permeation rate and V_f value of the best prepared PA12_62.5PVA^BF05_37.5 blown film specimen was only 77 cm³/m².day.atm and 1.82×10^-3nm³,respectively,which were roughly 7 times and 12%lower than those of the PA12 blown film,respectively.Similarly,the melt flow rates?MFR?improved gradually,as PVA^BFzcontents of PA12_xPVA_y,^BF05PA12_xPVA_y^BF08and PA12_xPVA_y ^BF14series specimens reached the corresponding critical value at 37.5,33.3 and 23.1wt%,respectively.At PVA contents higher than the equivalent critical PVA contents,MFR values of PA12_xPVA_y,^BF05PA12_xPVA_y ^BF08and PA12_xPVA_y^BF14series specimens reduced abruptly with the further increase in their PVA contents,respectively.As evidenced by DSC?differential scanning calorimetry?and dynamic mechanical analyses?DMA?,PVA molecules were nearly completely miscible with PA12 molecules when small amounts of PVA resins were melt-blended with PA12resins.However,as revealed by DSC and DMA analyses,clear phase separation of PA12 and PVA molecules did occur during melt-blending processes of PA12_xPVA_y,^BF05PA12_x PVA_y^BF08and/or PA12_xPVA_y^BF14resins,when their equivalent PVA^BFz contents were more than the critical value,respectively.The significantly improved oxygen barrier,V_f and MFR properties found for PA12_xPVA_y ^BFzseries specimens,are apparently due to the efficient miscibility of PVA^BFz molecules with PA12 molecules during their melt-blending processes as their PVA^BFz contents reached the corresponding critical value,respectively.