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. 2021 Jul 7;22(14):7304.
doi: 10.3390/ijms22147304.

Polyurethane Composites Reinforced with Walnut Shell Filler Treated with Perlite, Montmorillonite and Halloysite

Sylwia Członka  1 , Agnė Kairytė  2 , Karolina Miedzińska  1 , Anna Strąkowska  1
Affiliations

Polyurethane Composites Reinforced with Walnut Shell Filler Treated with Perlite, Montmorillonite and Halloysite

Sylwia Członka et al. Int J Mol Sci. .

Abstract

In the following study, polyurethane (PUR) composites were modified with 2 wt.% of walnut shell filler modified with selected mineral compounds-perlite, montmorillonite, and halloysite. The impact of modified walnut shell fillers on selected properties of PUR composites, such as rheological properties (dynamic viscosity, foaming behavior), mechanical properties (compressive strength, flexural strength, impact strength), dynamic-mechanical behavior (glass transition temperature, storage modulus), insulation properties (thermal conductivity), thermal characteristic (temperature of thermal decomposition stages), and flame retardant properties (e.g., ignition time, limiting oxygen index, heat peak release) was investigated. Among all modified types of PUR composites, the greatest improvement was observed for PUR composites filled with walnut shell filler functionalized with halloysite. For example, on the addition of such modified walnut shell filler, the compressive strength was enhanced by ~13%, flexural strength by ~12%, and impact strength by ~14%. Due to the functionalization of walnut shell filler with thermally stable flame retardant compounds, such modified PUR composites were characterized by higher temperatures of thermal decomposition. Most importantly, PUR composites filled with flame retardant compounds exhibited improved flame resistance characteristics-in all cases, the value of peak heat release was reduced by ~12%, while the value of total smoke release was reduced by ~23%.

Keywords: halloysite; high-energy ball milling process; montmorillonite; perlite; polyurethane composites; walnut shells.

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Conflict of interest statement

The authors reported no conflicts of interest related to this study.

Figures

Figure 1
Figure 1
The external surface of (a) unmodified walnut shell filler, and walnut shell filler modified with (b) perlite, (c) montmorillonite, and (d) halloysite.
Figure 2
Figure 2
Particle size distribution of (a) WS (b) WS/P, (c) WS/MMT, and (d) WS/HL.
Figure 3
Figure 3
The results of dynamic viscosity of PUR systems containing WS fillers.
Figure 4
Figure 4
Cellular structure of (a) PUR_0, (b) PUR_WS, (c) PUR_WS/P, (d) PUR_WS/MMT, (e) PUR_WS/HL.
Figure 5
Figure 5
Call size distribution of (a) PUR_0, (b) PUR_WS, (c) PUR_WS/P, (d) PUR_WS/MMT and (e) PUR_WS/HL.
Figure 6
Figure 6
Closed-cell content and thermal conductivity results of PUR composites containing walnut shell fillers.
Figure 7
Figure 7
The results of apparent density and cell size of PUR composites containing walnut shell fillers.
Figure 8
Figure 8
The impact of walnut fillers on the compressive strength of PUR foams.
Figure 9
Figure 9
The impact of walnut shell fillers on the flexural strength and impact strength of PUR foams.
Figure 10
Figure 10
Dynamic-mechanical performance of PUR composites containing walnut shell filler–(a) tan δ and (b) storage modulus.
Figure 11
Figure 11
The results of the cone calorimeter experiment—(a) the peak rate of heat release (pHRR), (b) the total smoke release (TSR), (c) the average yield of CO, and (d) the average yield of CO2.
Figure 12
Figure 12
Thermogravimetric (TGA) and derivative thermogravimetry (DTG) results of (a,b) walnut shell fillers and (c,d) PUR composites.
Figure 13
Figure 13
Schematic procedure of the synthesis of PUR composites reinforced with walnut shells modified with perlite/montmorillonite/halloysite.
See this image and copyright information in PMC

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