*Article* **Outdoor Wood Mats-Based Engineering Composite: Influence of Process Parameters on Decay Resistance against Wood-Degrading Fungi** *Trametes versicolor* **and** *Gloeophyllum trabeum*

**Minzhen Bao 1,\* , Neng Li 1, Yongjie Bao 1, Jingpeng Li <sup>1</sup> , Hao Zhong <sup>1</sup> , Yuhe Chen <sup>1</sup> and Yanglun Yu 2,\***

	- **\*** Correspondence: baominzhen@caf.ac.cn (M.B.); yuyanglun@caf.ac.cn (Y.Y.)

**Citation:** Bao, M.; Li, N.; Bao, Y.; Li, J.; Zhong, H.; Chen, Y.; Yu, Y. Outdoor Wood Mats-Based Engineering Composite: Influence of Process Parameters on Decay Resistance against Wood-Degrading Fungi *Trametes versicolor* and *Gloeophyllum trabeum*. *Polymers* **2021**, *13*, 3173. https://doi.org/10.3390/ polym13183173

Academic Editor: Antonios N. Papadopoulos

Received: 30 August 2021 Accepted: 17 September 2021 Published: 18 September 2021

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**Abstract:** The process parameters significantly influence the preparation and final properties of outdoor wood mats-based engineering composite (OWMEC). During outdoor use, wood composites are susceptible to destruction by rot fungi. Herein, the role of process parameters such as density and resin content on OWMEC resistance to fungal decay was investigated. The poplar OWMEC samples were exposed to white-rot fungus *Trametes versicolor* and brown-rot fungus *Gloeophyllum trabeum* for a period of 12 weeks. The chemical composition, crystallinity, and morphology were evaluated to investigate the effect of process parameters on the chemical composition and microstructure of the decayed OWMEC. With an increase in the density and resin content, the mass loss of the decayed OWMEC decreased. The highest antifungal effect against *T. versicolor* (12.34% mass loss) and *G. trabeum* (19.43% mass loss) were observed at a density of 1.15 g/m<sup>3</sup> and resin content of 13%. As results of the chemical composition and microstructure measurements, the resistance of OWMEC against *T. versicolor* and *G. trabeum* fungi was improved remarkably by increasing the density and resin content. The results of this study will provide a technical basis to improve the decay resistance of OWMEC in outdoor environments.

**Keywords:** outdoor wood mats-based engineering composite; wood-degrading fungi; decay resistance; durability
