Effect of biaxial stretching on the physical and mechanical properties of the HDPE/LDPE blend

Four different types of HDPE and LDPE were prepared, and samples (H4, L2, and L3) that exhibited similar molecular weight, melt flow index, and rheological properties as BOPE (BO) were screened. The samples were each blended, and the better compatibility of HDPE/LDPE blend system (HL1) was confirmed through the Cole-Cole plot. Thermal and thermo-mechanical properties of HL1 blend compositions were analyzed to optimize the compositions for biaxial stretching application. Especially, G′ and Tan δ were confirmed as tools to evaluate the feasibility of optimized compositions for biaxial stretching application, and the proper range of stretching temperature at which the ΔTan δ value maintained minimal energy change for biaxial stretching was determined. The modulus of the biaxially stretched samples x3 was improved by more than 10% compared to the existing sheet, and the elongation at break of all blend samples was approximately twice as good as that of BO. The better optical transparency was achieved as of biaxial stretching of blend samples, and crystal change in the stretched film compared to the sheet was clearly confirmed. From this work, it was confirmed that the G′ and Tan δ have been proved to be used as a parameter to assess the processability for biaxial stretching, and this process gave the advantage of the optimized HDPE/LDPE blend ratio with higher mechanical and optical clarity, suggesting that the blend could be applied to various packaging materials.