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Open AccessArticle

Excellent Fireproof Characteristics and High Thermal Stability of Rice Husk-Filled Polyurethane with Halogen-Free Flame Retardant

1
Department of Polymer and Composite Materials, Faculty of Materials Science and Technology, University of Science, Vietnam National University, HoChiMinh 700000, Vietnam
2
Department of Polymer Chemistry, Faculty of Chemistry, University of Science, Vietnam National University, HoChiMinh 700000, Vietnam
3
Department of Chemical Engineering, Pohang University of Science and Technology, Pohang 37673, Korea
4
Department of Polymer Science and Engineering, Sungkyunkwan University, Suwon, Gyeonggi 16419, Korea
*
Authors to whom correspondence should be addressed.
Huong TQ Phan and Binh T Nguyen contributed equally to this work.
Polymers 2019, 11(10), 1587; https://doi.org/10.3390/polym11101587
Received: 24 August 2019 / Revised: 17 September 2019 / Accepted: 23 September 2019 / Published: 28 September 2019
(This article belongs to the Section Polymer Applications)
The thermal stabilities, flame retardancies, and physico-mechanical properties of rice husk-reinforced polyurethane (PU–RH) foams with and without flame retardants (FRs) were evaluated. Their flammability performances were studied by UL94, LOI, and cone calorimetry tests. The obtained results combined with FTIR, TGA, SEM, and XPS characterizations were used to evaluate the fire behaviors of the PU–RH samples. The PU–RH samples with a quite low loading (7 wt%) of aluminum diethylphosphinate (OP) and 32 wt% loading of aluminum hydroxide (ATH) had high thermal stabilities, excellent flame retardancies, UL94 V-0 ratings, and LOIs of 22%–23%. PU–RH did not pass the UL94 HB standard test and completely burned to the holder clamp with a low LOI (19%). The cone calorimetry results indicated that the fireproof characteristics of the PU foam composites were considerably improved by the addition of the FRs. The proposed flame retardancy mechanism and cone calorimetry results are consistent. The comprehensive FTIR spectroscopy, TG, SEM, and XPS analyses revealed that the addition of ATH generated white solid particles, which dispersed and covered the residue surface. The pyrolysis products of OP would self-condense or react with other volatiles generated by the decomposition of PU–RH to form stable, continuous, and thick phosphorus/aluminum-rich residual chars inhibiting the transfer of heat and oxygen. The PU–RH samples with and without the FRs exhibited the normal isothermal sorption hysteresis effect at relative humidities higher than 20%. At lower values, during the desorption, this effect was not observed, probably because of the biodegradation of organic components in the RH. The findings of this study not only contribute to the improvement in combustibility of PU–RH composites and reduce the smoke or toxic fume generation, but also solve the problem of RHs, which are abundant waste resources of agriculture materials leading to the waste disposal management problems. View Full-Text
Keywords: flame retardancy; cone calorimetry; polyurethane/rice husk composite foam; thermal stability; moisture absorption flame retardancy; cone calorimetry; polyurethane/rice husk composite foam; thermal stability; moisture absorption
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MDPI and ACS Style

Phan, H.T.; Nguyen, B.T.; Pham, L.H.; Pham, C.T.; Do, T.V.V.; Hoang, C.N.; Nguyen, N.N.; Kim, J.; Hoang, D. Excellent Fireproof Characteristics and High Thermal Stability of Rice Husk-Filled Polyurethane with Halogen-Free Flame Retardant. Polymers 2019, 11, 1587.

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