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MATERIALS 59
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strands exhibited a screw withdrawal strength of 35.4 ± 8.6 However, this variation of about 1.4 percent was not
N/mm, compared to 27.4 ± 6.4 N/mm for the control panels statistically significant. Therefore, the TGA and DTGA studies
and 29.46 ± 6.9 N/mm for equivalent strength in the control helped prove that recycling of the strands had no significant
panels. Despite this improvement, a single-factor ANOVA revealed influence on the thermal stability of the final panels.

that the variation was not statistically significant (p = 0.11). The increase in mass retention, however, would have a
The ESG values were also calculated for both panel types. direct influence on the fire reaction properties of the samples,
Panels made from recycled strands showed an ESG of which were observed to be significantly better in many aspects
0.48 ± 0.05, approximately 11 percent higher than the control tested. The primary reaction that helps the pMDI adhesive
panels, which had an ESG of 0.44 ± 0.04, with negligible bond the strands together to form a panel is the one between
change in the average ESG value when equivalent strength the adhesive and moisture.
of the control panels. Besides, the time to flameout was also observed to be
These values are comparable to or slightly higher than significantly higher for the panels with re-resinated strands.
those of similar strand-based structural panels; for example, The control panels had a time to flameout of 306.67 ± 17.8

OSBs typically have an ESG of around 0.4, while OSLs exhibit s, resulting in a burning time of 289 ± 17.7 s. The panels
a slightly higher ESG of approximately 0.51. from recycled strands had a flameout time of 472.33 ± 18.6
It must be noted that all the tests were conducted only s, resulting in a burning time of 430 ± 18.2 s.
in the face direction. These findings demonstrate that panels Higher burning time further proves that the char formation
made from recycled strands achieve high-quality performance was higher in the panels with re-resinated strands, which
and are potentially suitable for structural applications in the suppressed the heat for a longer time and resulted in a
built environment. comparatively more fire-safe structure.

Furthermore, the overall mechanical performance comparisons The ability to sustain an induced flame for longer times
confirm that waste strands can be effectively reused to helps produce panels that can maintain their structural integrity
manufacture panels without negatively impacting their longer, and if applied in the built environment, can be denoted
mechanical properties, where, in some cases, properties such as a safer structure where inhabitants would have more time
as internal bond strength, withdrawal strength, and ESG can to evacuate in any kind of fire scenario. Thus, a higher amount
even be improved. of pMDI helps make structures comparatively safer under fire.
The influence of thermal stability due to recycling and re- Total heat evolved (THE), which can also be called the
resinating the strands was established using the TGA study. peak total heat released, is known to directly influence the
TGA was used to generate mass loss curves, revealing surrounding temperature and conditions of the structure

that the re-resinated samples exhibited higher mass retention under fire.
(25 percent) and lower overall mass loss compared to the
control panels, which showed a mass retention of 22 percent.
This improved thermal stability can be attributed to the Fredricsons Trä
higher pMDI content present in the strands during the panel-
forming process. The DTGA study further showed that the
reference temperature or peak mass loss temperature (TR) was

354.17 deg C for the control panels compared to 349.67 deg
C for the panels made from re-resinated strands.