On properties of graft copolymers of LLDPE and novel fluorine surfactants obtained via reactive extrusion

A series of nonionic fluorin surfactants containing poly(ethylene glycol) (PEG) and their acrylates were synthesized using PEGs of different molecular weight (M-w 600, 1000, 1500, 2000, 4600 g/mol), TDI, acryloyl chloride, and pentadecafluorooctanoic chloride as the main starting materials. Their chemical structures were characterized by means of FTIR and H-1 NMR. The surface tension (gamma) of the fluorine surfactants were evaluated by drop weight method. The gamma value was found to increase with the length of PEG chains. The acrylates were adopted as functionalizing monomers and grafted onto linear low-density polyethylene (LLDPE) through a melt reactive extrusion procedure. The graft degrees of LLDPE were determined by FTIR. Five graft LLDPE samples with grafting degrees of 0.79% (A-I), 0.72% (A-II), 0.68% (A-III), 0.63% (A-IV), and 0.57% (A-V) were prepared. Their surface properties were characterized by measuring contact angles with water and by X-ray Photoelectron Spectroscopy (XPS). Thermal properties of graft LLDPE samples were studied using differential scanning calorimetry. Crystallization rates of graft LLDPEs were faster than that of plain LLDPE at a given crystallization temperature because graft chains could act as nucleating agents. The isothermal crystallization behavior of grafted LLDPE was in accordance with the Avrami model only in the first stage of the process, and deviated from the model by increasing the crystallization time.