The Application Of LDPE With High Melt Index In Blue Polyolefin Masterbatch

Dispersant plays an important role in the processing of the masterbatch. However, the addition of dispersant with low molecular weight will reduce the final properties of products, such as mechanical properties, aging resistance, and transparency. Although dispersant could promote the infiltration and dispersion of pigment, the addition of dispersant in the processing of the top grade masterbatch has been discarded. This makes it difficult to control the dispersion of pigment and viscosity of resin system. Therefore, the resin with high melt index was used to adjust the viscosity of resin system and dispersion of pigment.In this paper, we adjust the viscosity of masterbatch system of which the concentration was 30%,by adding different proportions of low density polyethylene (LDPE) with high melt index to gain the best dispersion of pigment without dispersant.The masterbatches with different proportion were made into plastic film and plastic sheet. Color properties of polyolefin masterbatch were measured by color measurement instrument, rheological properties were measured by melt flow speed indicator and optical microscope was used to observe the dispersion of pigment. First, we determined the the optimum ratio of polyethylene wax which was being added as dispersant into LDPE which melt index was 7, by using the characterization methods listed above. Then we blended four kinds of LDPE with high melt index (MI= 20\40\80\200) with LPDE (MI= 7) as masterbatch carrier resin, without adding polyethylene wax dispersant, and used the same methods to characterize the rheological properties, color properties of polyolefin masterbatch and the dispersion of pigment.The results showed that the best ratio for polyethylene wax adding as dispersant was 10%, when the concentration of masterbatch was 30%. Without polyethylene wax being added as dispersant, the addition of LDPE with high melt index not only regulated the viscosity of masterbatch, but also improved the dispersion of pigment in masterbatch. To achieve equal performance as of masterbatch with 10% polyethylene wax. Different amount of addition was needed when the melt index of LDPE was different. LDPE needed to be added to 70% when the MI was 20. LDPE (MI=40\80) mixed with LDPE (MI=7) as carrier resin, the amount of addition was 28%. When LDPE (MI=200) was added to 14%, the properties obtained was most close to the properties of masterbatch with polyethylene wax.