Study Of Preparing Metallocene Polyethylene Films With Excellent Properties

With excellent mechanical properties, a majority of metallocene polyethylene was used as films. However it is difficult to manufacture metallocene polyethylene in common blown-film machines. By blending and filling, this paper investigates different systems' rheological and crystallization properties, also films' mechanical strengths are researched. The thesis consists of two parts:Chapter 3 focused on the effects of LDPE, LLDPE on the mechanical, rheological crystallization properties of bimodal metallocene PE(mPE) and smPE with higher content of co-monomer.In chapter 4, the effects of nano-CaCO₃ on the mechanical, rheological and crystallization properties of mPE/LLDPE (20/80,weight ratio) blends were investigated. Following conclusions are made.1. When added LLDPE and LDPE, tensile strength, tear strength and puncture strength of Mpe and smPE films decrease by different extents. In mPE /LLDPE(LDPE) blends when LLDPE ( LDPE )content varies from 20% to 80%(weight fraction), tear strength and puncture of remain almost constant; smPE/LLDPE film's puncture strength changes slowly too. Considering DSC analysis, it can be verified that the co-crystallization between ingredients affects tear strength and puncture strength greatly.2. Added 20%(weight fraction) mPE, LLDPE(LDPE) films' puncture strength, tear strength and tensile strength were improved by about 60%(100%),, 10%(10%) and 30%(40%), however the cost just increased slightly. The blends can be easily manufactured in commonblown-film machine, as has important meanings in industry.3. LDPE and LLDPE can improve flowing performance of smPE and mPE. Because of good similarity of molecular between mPE and LLDPE, comparing with pure mPE, their blends' apparent viscosity decrease slightly. LDPE can apparently decrease the apparent viscosity of both mPE and smPE. According to above results we testify that the long branchs of LDPE play an important role in ameliorating mPE and smPE's flowing performance.4. The sequence of compatibility of blends is given as following: LLDPE/mPE>LLDPE/smPE>LDPE/mPE>LDPE/smPE5. A mince of nano-CaCO3(below 5% , weight fraction) can strengthen and toughen the mPE/LLDPE blends. When nano-CaCO₃ content is below 15%, the cost of film declines greatly but the mechanical properties almost remain constant. There are some differences among different treatments to nano-CaCO₃, but the effects of couple agent on tear strength and tear strength are great.6. Comparing with pure LLDPE, blend of LLDPE/ mPE(80/20, weight fraction) and 15% nano-CaCO₃ improve the tear strength and puncture of films by about 10% 30%, and tensile strength just decreases slightly, meanwhile, films' cost declines by a certain extent. To those products which require higher puncture and tear strength but less tensile strength, such as geomembrane, the phenomena above has great economical meaning.7. nano-CaCO₃ influences the flowing performance of blends slightly, and the effect can always be neglected.8. nano-CaCO₃ only affects blends' degree of crystallization, but do not affect the crystallization structure.