Mechanical Properties and Thermal Degradation Behaviour of Polyurethane Composites Incorporating Waste-Glass Particles

Abstract

This study investigated the effect of hot-pressing conditions, including the curing temperature, curing time and the applied pressure, on the flexural properties of polyurethane (PU) composites incorporating 88 wt.% (Glass/PU-88/12) and 95 wt.% (Glass/PU-95/5) recycled glass particles. Hot-pressing (cure) temperatures between 100 °C and 180 °C were investigated with the objective to shorten the cure cycle, thereby increasing the production rate of the glass/PU composites to match industrial scales. The hot-pressing time varied between 1 min and 30 min, while the pressure varied between 1.1 MPa and 6.6 MPa. Further to investigating the hot-pressing conditions, the effect of post-curing on the flexural properties of glass/PU composites was also investigated. Microstructural analysis was used to identify the interactions between the glass particles and the PU matrix, explore the void content and establish the relationship between the microstructure and the mechanical properties of the resultant glass/PU composites. Glass/PU composites incorporating 5 wt.% (Glass/PU-95/5), 10 wt.% (Glass/PU-90/10) and 12 wt.% (Glass/PU-88/12) were manufactured under optimised hot-pressing conditions (temperature = 100 °C; cure time = 1 min; pressure = 6.6 MPa) and evaluated under flexural, tensile and compression loadings. Furthermore, the high-temperature stability of the composites was evaluated using thermogravimetric analysis. This study demonstrates the feasibility of upcycling glass waste into value-added materials for potential use in the construction and building industry.

Keywords: construction and building; glass/PU composites; mechanical properties; optimised manufacturing process; upcycling glass waste.

Figure 1

Schematic of the glass/PU hot-pressing manufacturing process: (I) mixing glass particles and PU, (II) transfer to mould, (III) hot pressing and (IV) demoulded composite.

Figure 2

Particle size distribution (PSD) of glass particles following acoustic grinding showing the passing (%) and volume density (%) functions.

Figure 3

The influence of hot-pressing temperatures between 100 °C and 180 °C, and the effect of 80 °C, 24 h post-curing on the flexural (a) strength and (b) modulus of PU/glass-95/5 composites manufactured under an applied pressure of 6.6 MPa over 1 min.

Figure 4

Influence of hot-pressing time on the flexural strength (pattern fill) and modulus (solid fill) of the non-post-cured Glass/PU-95/5 composite hot pressed at 160 °C under a pressure of 6.6 MPa with curing times ranging between 1 min and 30 min.

Figure 5

Effect of hot-pressing pressure on the flexural strength (pattern fill) and modulus (solid fill) of the non-post-cured Glass/PU-88/12 composite hot pressed at a temperature of 160 °C for 1 min.

Figure 6

Flexural strength (pattern fill) and modulus (solid fill) of the glass/PU composites incorporating 5 wt.% (Glass/PU-95/5), 10 wt.% (Glass/PU-9/10) and 12 wt.% (Glass/PU-88/12) polymeric binder. The glass/PU composites were hot pressed at 160 °C, under a pressure of 6.6. MPa for 1 min followed by post-curing at 80 °C over 24 h.

Figure 7

CT images of (a) Glass/PU-95/5, (b) Glass/PU-90/10 and (c) Glass/PU-88/12 composite, respectively. SEM images of (d) Glass/PU-95/5, (e) Glass/PU-90/10 and (f) Glass/PU-88/12 composites, respectively. The red speckles in the CT images indicate the voids, while porosity in SEM images is indicated by red arrows in (d–f).

Figure 8

SEM image of the Glass/PU-95/5 composite revealing debonding at the polymeric binder and glass particle interface (within red dashed lines).

Figure 9

(a) The tensile stress–strain profiles and (b) the tensile strength (pattern fill) and modulus (solid fill) of glass/PU composites with PU content varying between 5 wt.% and 12 wt.%. The glass/PU composites were hot pressed at 160 °C, under a pressure of 6.6. MPa for 1 min followed by post-curing at 80 °C over 24 h.

Figure 10

Compression strength (pattern fill) and modulus (solid fill) of the glass/PU composites incorporating a 5 wt.% (Glass/PU-95/5), 10 wt.% (Glass/PU-9/10) and 12 wt.% (Glass/PU-88/12) polymeric binder. The glass/PU composites were hot pressed at 160 °C, under a pressure of 6.6. MPa for 1 min followed by post-curing at 80 °C over 24 h.

Figure 11

(a1,a2) The mass loss (%)–temperature and (b1,b2) derivative thermogravimetric (DTG) profiles of neat PU and glass/PU composites with different weight fractions of PU (5 wt.%, 10 wt.% and 12 wt.%).