الملخص
Polyethylene (PE) is the largest produced thermoplastic polymer and is highly used in packaging applications. There exist different types of PE polymers depending on the molecular architecture. The most common types are: Low-Density Polyethylene (LDPE); Linear Low-Density Polyethylene (LLDPE); and High-Density Polyethylene (HDPE). LDPE is produced from free-radical polymerization of ethylene, and it has broad molecular distribution and good processability but lower mechanical properties. LLDPE is produced from co-polymerization of ethylene and α-olefin (butene, hexene or octene) using metallocene catalyst, and it possesses better mechanical properties but lower processability. Usually, for a packaging application, LLDPE is favored for its mechanical properties; however, its processability is a disadvantage. An approach to over come this problem is to blend LLDPE with LDPE. The main objective of this study is to investigate the influence of branch type (butene, hexene and octene) of LLDPE on the mechanical properties of its blends with LDPE. Three blend systems: B-type (B-LLDPE/LDPE), H-type (H-LLDPE/LDPE) and O-type (O-LLDPE/LDPE) were studied for tensile and microhardness. The results show that an addition of small amount (10%) of LDPE to LLDPE polymers produced a negligible effect on modulus of elasticity, yield and tensile strengths, and ductility of the blends. Whereas, the effect of the addition of small amount of LLDPE to LDPE depends on the type of blends and varies from one mechanical property to another. The correlation of Vickers hardness numbers with yield strength values was found to follow Tabor's relationship for most of the blend systems. The mechanical properties and the microhardness results are well correlated with the amount of crystallinity in the studied samples.
