DPSSL-microscopy of polymer compositions based on polyethylene [10803-020] and gas-generating agent hydrocerol

• Compositions on the basis of polyethylene (PE) of grade 10803-020 (Russia) were investigated. The particulate chemical gas-generating agent hydrocerol (hyd) of Hydroserol BIF brand with the starting decomposition temperature of 140°C, which is the mix of endothermic foaming agents, including sodium hydrogen carbonate, was used for creating the pore structure. The gaseous products of hydrocerol degradation are water vapor and carbon dioxide in equal proportions. It is assumed that the formed gas is distributed in the polymer melt in the form of meshes; in this case the tear of walls, fusion of meshes and formation of pores may take place.

The following substances was used as the natural particulate fillers: wood flour (WF) of three fractions with the size of the particles up to 80, 14 and 200 μm; corn starch (st) of Hi Maize 1043 brand with the particle size of 100 μm. The elemental chemical composition of the wood flour is approximately the same for all wood species, namely wt %: carbon – 49 – 51%, oxygen – 43 – 44%, hydrogen – 6,0 – 6,4%, nitrogen – 0,1 – 0,03%. The main materials composing the wood are natural polymers: cellulose, lignin, hemicellulose. Wood flour is the waste of the woodworking and timber industry.

The fillers are finely dispersed. They increase the number of defects in the matrix and thereby decrease the robustness of material against physical and impacts.

The PE compositions with hydrocerol were obtained by mechanical mixing in the melt on laboratory micro-roll mills VK-6 (Russia) with the heating at 120°C. This method provides a quite uniform distribution of the filler in the polymer melt. The hydrocerol content in the test charge and compositions was 5 wt %. Mixing was performed until a uniform distribution of the hydrocerol particles in the polymer melt was attained. Introduction of the natural component was also performed on the rotating roll mills until a uniform distribution of the particles in the polymer melt was attained. The natural component content in the compositions was 15 or 30 wt %. Formulations of the compositions are given in the table below:

Table – Formulations of investigated compositions

№

Composition

1

PE (test charge)

2

PE + 5%hyd (test charge)

3

PE + 5%hyd+15%WF(0-80)

4

PE + 5%hyd + 15%WF(0-140)

5

PE + 5%hyd + 15%WF(0-200)

6

PE + 5%hyd + 15%st

7

PE + 5%hyd + 30%WF(0-80)

8

PE + 5%hyd + 30%WF(0-140)

9

PE + 5%hyd + 30%WF(0-200)

10

PE + 5%hyd + 30%st

After mixing, the viscous mass was removed from the roll mills and cooled at room temperature (20±2°C) down to hardening. Samples in the form of round plates were obtained by pressing in the form of a hardened chopped mass on a manual laboratory hydraulic press at 120°C without pressure.  At the same time foaming was performed at 160°C – the temperature of more complete decomposition of hydrocerol.