High Density Polyethylene

Abstract

Nanocomposite based on high density polyethylene (HDPE) and layered zirconium phosphate organically modified with octadecylamine (ZrPOct) was obtained through melt processing.

The ZrPOct was synthesized by precipitation and modified by suspension and sonication procedures. The initial and maximum degradation temperatures (Tonset and Tmax) were increased. A slight decrease of crystallinity degree was detected. Reduction of elastic modulus and elongation at break were noticed. The lamellar spacing was increased (3.3 times higher). The storage modulus decreased and low field nuclear magnetic resonance (LFNMR) revealed an increasing of molecular mobility. The presence of octadecylamine enhanced the entrance of HDPE in the ZrPOct galleries. Several characteristics of HDPE were changed indicating that intercalation was successful. All results indicated that partially intercalated and/or exfoliated nanocomposite was achieved.

Modification of the layered zirconium phosphate

The ZrP was modified by intercalation of amine according to the experimental procedure[19,20]. A certain amount of α-ZrP

and a solution of octadecylamine (2:1 alcohol/water) were mixed at an amine/α-ZrP molar ratio of 1.5. The product was centrifuged and washed successively with alcohol to remove the excess of amine. As before, the resulting solid was placed in a freezer at –80 °C for 24 hours and then submitted to lyophilization for 4 days. The final product was labeled as ZrPOct.

Preparation of nanocomposites

Nanocomposites of HDPE and layered zirconium phosphates– neat and organically modified with octadecylamine – with a fixed phosphate percentage of 2% w/w, were processed in a counter-rotating twin-screw extruder. The extruder was adjusted to operate at 100 rpm and temperature profile of 160 °C (input) and 170 °C, 180 °C and 190 °C (output), conditions recommended by the polymer manufacturer. The extrudate was cooled and granulated. In order to homogenize the

nanocomposite, the material was reprocessed under the same conditions. In order to characterize the material, thin plates was processed in Carver press at 210 °C, with load of 5000 kg for 7 minutes.

Results and Discussions

Hydrogen low field nuclear magnetic resonance

Dynamic-mechanical test

WAXD

Thermogravimetry

Differential scanning calorimetry

Mechanical measurements

Melt flow rate

Conclusions

Alpha-zirconium phosphate was synthesized and modified with octadecylamine in order to produce nanocomposite based on HDPE. According to some conventional characterization techniques of polymers (DSC, TGA, WAXD, MFR, tensile‑deformation) HDPE/ZrP behave as a microcomposite. On the contrary, presence of octadecylamine as intercalation agent of ZrP allowed the increasing of its interlamellar spacing. Also facilitate the entrance of the HDPE chain along the filler galleries. This produced changes in the HDPE behavior. Decreasing of the (d001) diffraction angle, elastic modulus, degree of crystallinity besides increasing of the interlamellar spacing and thermal stability lead to induce that a partially and/or exfoliated nanocomposite was reached.

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