Polypropylene Color Masterbatches Containing Layered Double Hydroxide Modified with Quinacridone and Phthalocyanine Pigments-Rheological, Thermal and Application Properties

Abstract

Polypropylene color masterbatches containing modified layered double hydroxides, LDHs, were created. The simple, industry-acceptable method of LDH surface modification with quinacridone and phthalocyanine pigments using the pulverization method in ball mills was applied. It was reported that the modification parameters such as time and rotational speed affected the tendency to create the aggregates for modified fillers. TGA analysis of the modified LDH showed that modification with phthalocyanine pigment shifted the temperature at which 5%, T_5%, and 10% of mass loss, T_10%, occurred compared with that for unmodified LDH. The viscoelastic properties of prepared masterbatches were investigated. The incorporation of the modified fillers instead of neat pigments led to an increase in the loss shear modulus, G″, indicating a stronger influence on the dissipation of energy by the melted masterbatch. The similar values of tan, δ, were determined for melted masterbatches containing phthalocyanine pigment and green modified LDH filler. The incorporation of both LDHs modified by phthalocyanine and quinacridone pigment fillers slightly increased the zero-shear viscosity, η₀, compared with that of the masterbatches based on the neat pigments. The Cole-Cole plots and the analysis of the Maxwell and continuous relaxation models showed that modified colored LDH fillers facilitated the relaxation of the melted masterbatch, and shorter relaxation times were observed. The phthalocyanine-modified LDH filler improved the thermal stability of the masterbatches. Additionally, the impact of pigments and modified, colored LDH on the crystallization of polypropylene was investigated.

Keywords: layered double hydroxide; phthalocyanine pigments; polypropylene masterbatches; quinacridone pigments; viscoelastic properties.

Scheme 1

Masterbatch or raw pigment?

Figure 1

The SEM pictures of the layered double hydroxide, hydrotalcite, HT, used to prepare the hybrid colored filler (SEM microscope, LEO 1530 Gemini, producent Zeiss/Leo, Oberkochen, Germany).

Figure 2

The chemical structures of used pigments: (a) pigment Green 7, phthalocyanine green, PG7; (b) pigment Red 122, 2,9-dimethylquinacridone, PR122.

Scheme 2

Preparation of modified colored filler. A—pigment Red 122, 2,9-dimethylquinacridone,((2,9-dimethyl-5,12-dihydroquinolino[2,3-b]acridine-7,14-dione), PR122; B—pure pigment Green 7, phthalocyanine green, PG7; C—modified colored filler HT-Red 50 rpm; D—modified colored filler HT—Green 50 rpm.

Scheme 3

Production of polypropylene color concentrate containing modified HT. C—modified colored filler HT-Red 50 rpm; D—modified colored filler HT—Green 50 rpm; E—masterbatch PP/HT-Red 50 rpm.; F—masterbatch PP/HT-Green 50 rpm.

Figure 3

DTGA plots of neat PG7 and PR122 pigments.

Figure 4

TGA and DTGA plots of HT-Green fillers.

Figure 5

TGA and DTGA plots of HT-Red fillers.

Figure 6

Complex viscosity, η* (Pas), at 200 °C, and at an applied oscillation strain of 0.5%.

Figure 7

The Cole–Cole plots at 200 °C; η′—dynamic viscosity (Pas), η″—out of phase component of complex viscosity η* (Pas).

Figure 8

The discrete relaxation spectra calculated using the Maxwell model.

Figure 9

Continuous relaxation spectra for the masterbatches melted at 200 °C.

Figure 10

TGA and DTGA plots of masterbatches containing PG7 pigment and modified HT-Green fillers.

Figure 11

TGA and DTGA plots of masterbatches containing PR122 pigment and modified HT-Red fillers.

Figure 12

DSC plots of the cooling step for masterbatches containing the PG7 and PR122 pigments and modified fillers HT-Green and HT-Red. A speed of cooling of 10 °C·min⁻¹ was used.

Figure 13

Color coordinates for modified PG7.

Figure 14

Color coordinates for modified PR122.