Melt Grafting of 10-Undecenoic Acid onto a Linear Low Density Polyethylene

A. CIOLINO; E. M. VALLÉS; M.D. FAILLA

JOURNAL OF APPLIED POLYMER SCIENCE

Wiley Priodicals Inc

Año: 2004 vol. 92 p. 2303 - 2311

0021-8995

The melt grafting of 10-undecenoic acid (UA) onto a linear low-density polyethylene (LLDPE) was studied. The grafting reaction was performed using a Brabender PlastographÔ mixer and 2,5-dimhetyl-2,5-di(tertbutylperoxy) hexane as initiator. The concentration of UA and peroxide ranged from 1 to 4% (w/w) and 0.025 to 0.1% (w/w), respectively. The evidence of the grafting of UA as well as its extent was determined by FTIR. The experimental results show that the amount of UA grafted increases with both the AU and initiator concentrations. However, the largest efficiency of grafting was found at the lowest concentration of UA explored. The grafting efficiency ranged from 40 to 8%. The dynamic linear viscoelastic properties of the original and grafted material were evaluated at different frequencies at 160°C using a rotational rheometer. The modification process affects slightly both the melt elasticity and viscosity of the LLDPE. Both the viscosity and elastic modulus increase with respect to the original material when the polymer was modified with only peroxide. The grafted polymers displayed values of elastic moduli and viscosity lower than the polymer modified with peroxide. Moreover, the values of those properties were even lower than those corresponding to the LLDPE when a concentration of 4% of UA was used.  These results combined with GPC results suggest that scission reaction may be favored.   The thermal properties such as melting temperature (Tf) and fusion enthalpy (DHf) measured using Differential Scanning Calorimetry were slightly reduced respect to the quantities corresponding to the original polymer.