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Polyamide-6 (PA6) is an important structural thermoplastic with high strength, resistance to
solvents, and good manufacturability. However, PA6 has a relatively high crystallization rate,
which causes high shrinkage during injection molding resulting in the instability of the product's
size. In addition, PA6 is characterized by high hygroscopicity, which can cause a decrease in heat
resistance and mechanical properties of products during operation. The disadvantages of PA6 can
be eliminated by physical modification with different fillers.
Aluminosilicate-reinforced polyamide nanocomposites have been of great interest since the 1990s
due to their high mechanical properties, heat resistance, fire resistance, barrier resistance, and ionic
conductivity [1].
It is known that a significant improvement in the properties of PA6 is observed only when it is
modified with organically modified montmorillonite (MMT) or at least pre-layered MMT. The use
of pure MMT does not give significant results regardless of the obtaining method of the
nanocomposite. It was found that polyvinylpyrrolidone (PVP) intercalates montmorillonite [2, 3],
and this is the basis for the creation of thermoplastic nanocomposites.
Therefore, we came up with the idea to use MMT intercalated with PVP to modify PA6 in order
to obtain nanocomposite as a structural material, as well as to obtain blends with polypropylene
(PP). It is expected that the use of PVP-intercalated MMT in a blend with PA6 will increase the
compatibility of PP with PA6, improve the physicomechanical and thermophysical properties of
PP as a starting matrix, and reduce the hygroscopicity of the material.
This work aimed to obtain nanocomposites based on PA6 and MMT intercalated with PVP by the
two following methods – mixing components in the melt and precipitation from the formic acid
solution. Also, the work aimed to compare the structure, heat resistance, and technological
properties of obtained nanocomposites and research their blend with PP.
The following materials and reagents were used during the studies. PA6 of PA6-210/310 brand
(JSC "Grodno Azot", Belarus) with MFI230/2.16 = 19 g/10 min (test conditions: temperature –
230°С, load – 2.16 kg), melting temperature 215°С, density ρ20 = 1120 kg/m3. PA6 was dried
under vacuum (13–15 Ра) at 90°С for 2 h. MMT 69911 [Al2Si4O10(OH)2·nH2O] (Sigma-Aldrich),
untreated, with a surface area of 250 m2/g and pH = 5–8. PVP (LLC "AK Sintvita", Russia) with
a molecular weight 12600±2700 g/mol, pH = 3–8, softening temperature 140–160°С, ρ20 = 1190
kg/m3 before use was dried under vacuum (13–15 Ра) at 60–70°С for 2–3 h. PP of Moplen HF501N
brand (Lyondell Basell Industries) with MFI230/2.16 = 9.50 g/10 min, density ρ20 = 900 kg/m3, Vicat
softening point 155°С. Chemically pure solvents such as benzene, acetone, and 85% formic acid
were applied in the studies. Formic acid, 85% of Vetec brand (Sigma-Aldrich) with pH = 2,2,
relative density ρ20 = 1220 kg/m3, viscosity kinematic 1,47 mm2 s−1 at 20°С. Benzene, 99.6%
(Sigma-Aldrich) with relative density ρ25 = 874 kg/m3. Acetone, 99.5% of Sigald brand (Sigma-Aldrich) with pH = 5–6, relative density ρ25 = 789 kg/m3.
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