*Article* **Chemical, Physical, and Mechanical Properties of Belangke Bamboo (***Gigantochloa pruriens***) and Its Application as a Reinforcing Material in Particleboard Manufacturing**

**Apri Heri Iswanto 1,2,\* , Elvara Windra Madyaratri 3,4, Nicko Septuari Hutabarat <sup>1</sup> , Eka Rahman Zunaedi <sup>1</sup> , Atmawi Darwis <sup>5</sup> , Wahyu Hidayat <sup>6</sup> , Arida Susilowati 2,7, Danang Sudarwoko Adi <sup>4</sup> , Muhammad Adly Rahandi Lubis 4,8 , Tito Sucipto 1,2, Widya Fatriasari <sup>4</sup> , Petar Antov 9,\* , Viktor Savov <sup>9</sup> and Lee Seng Hua <sup>10</sup>**


**Abstract:** This study aimed to analyze the basic properties (chemical composition and physical and mechanical properties) of belangke bamboo (*Gigantochloa pruriens*) and its potential as a particleboard reinforcement material, aimed at increasing the mechanical properties of the boards. The chemical composition was determined by Fourier transform near infrared (NIR) analysis and X-ray diffraction (XRD) analysis. The physical and mechanical properties of bamboo were evaluated following the Japanese standard JIS A 5908 (2003) and the ISO 22157:2004 standard, respectively. The results showed that this bamboo had average lignin, holocellulose, and alpha-cellulose content of 29.78%, 65.13%, and 41.48%, respectively, with a degree of crystallinity of 33.54%. The physical properties of bamboo, including specific gravity, inner and outer diameter shrinkage, and linear shrinkage, were 0.59%, 2.18%, 2.26%, and 0.18%, respectively. Meanwhile, bamboo's mechanical properties, including compressive strength, shear strength, and tensile strength, were 42.19 MPa, 7.63 MPa, and 163.8 MPa, respectively. Markedly, the addition of belangke bamboo strands as a reinforcing material (surface coating) in particleboards significantly improved the mechanical properties of the boards, increasing the modulus of elasticity (MOE) and bending strength (MOR) values of the fabricated composites by 16 and 3 times.

**Keywords:** *Gigantochloa pruriens*; chemical properties; physical and mechanical properties; wood-based composites; particleboard

**Citation:** Iswanto, A.H.; Madyaratri, E.W.; Hutabarat, N.S.; Zunaedi, E.R.; Darwis, A.; Hidayat, W.; Susilowati, A.; Adi, D.S.; Lubis, M.A.R.; Sucipto, T.; et al. Chemical, Physical, and Mechanical Properties of Belangke Bamboo (*Gigantochloa pruriens*) and Its Application as a Reinforcing Material in Particleboard Manufacturing. *Polymers* **2022**, *14*, 3111. https://doi.org/10.3390/ polym14153111

Academic Editors: Gianluca Tondi and Luis Alves

Received: 5 July 2022 Accepted: 29 July 2022 Published: 30 July 2022

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

#### **1. Introduction**

As a country known for its high biodiversity, Indonesia has hundreds of bamboo species. It has the third-largest bamboo population in the world after China and India. Bamboo grows in dry to wet, tropical climates [1–4]. In addition to being used as a nonpermanent material in construction and furniture making, it has various industrial applications, such as fiber reinforcement, paper, textiles, oriented strand board, particleboard, food, and bioenergy [5–10]. Furthermore, it is a fast-growing plant with a short harvest time (3–5 years old) and high productivity of 20–40 tons/ha/year, 7–30% higher than woody plants [5,11–13].

One of the most common bamboo species of the *Gigantochloa* genus, found in northern Sumatra, is the *Gigantochloa pruriens*, an endemic species spreading across the Karo and Gayo districts in Indonesia. The culms of *Gigantochloa pruriens* are regarded as valuable feedstocks widely used in construction applications for manufacturing walls, pillars, roofs, etc. Similar to wood, bamboo also has various properties. The characterization of chemical, physical, and mechanical properties of belangke bamboo raw materials is a very important factor in determining its suitability for various commercial applications, one of which is as a raw material for manufacturing particleboard. Currently, research data related to belangke bamboo is still rather limited. Based on the literature review results, only one study related to the anatomical properties of belangke bamboo was found, which was reported by Darwis et al. [14]. Several studies have shown that, in general, bamboo has good mechanical properties so that it can be used as a raw material for structural composites and as a surface layer modification material to improve the strength of particleboard [7,9,10,15–17].

In particleboard manufacturing, mixing particles of two different species is not a common practice. Wood particles with stronger mechanical strength could be used to compensate for the inferiority of the other weaker wood particles in the particleboard [18,19]. Lee et al. [18,19] used rubberwood (*Hevea brasiliensis*) particles as a surface layer and oil palm trunk particles as a core layer to produce three-layer particleboard. The mechanical properties of the particleboard were found to increase along with the increased proportion of rubberwood particles in the surface layer. The studies demonstrated that the employment of stronger wood species as surface layer could result in improved mechanical strength of the composites. Bamboo was found to be a good reinforcing material for particleboard. De Almeida et al. [20] reported that the incorporation of 25% and 50% of *Dendrocalamus asper* bamboo into particleboard made of *Eucalyptus urophylla* × *grandis* wood had improved the bending strength of the particleboard produced. Mixing a more compressible wood with other noncompressible wood could enhance the compression and consolidation of the particleboard [21]. A study by Zaia et al. [22] reported the application of bamboo laminas of *Dendrocalamus giganteus* as a reinforcement for particleboard. The board produced showed a great potential to be used as construction materials. However, relevant studies are scarce, particularly those involving bamboo strands. Therefore, the goal of this research work was to investigate the basic properties (chemical composition, physical, and mechanical properties) of belangke bamboo (*Gigantochloa pruriens*) and evaluate its potential as a particleboard reinforcing material, aimed at improving the boards' mechanical properties.

#### **2. Materials and Methods**

#### *2.1. Materials*

The *Gigantochloa pruriens* bamboo (Figure 1) was obtained from the Binjai region, North Sumatra (3◦3505500 N, 98◦2804900 E). The length and diameter of belangke bamboo used in this work were approximately 14 m and 6 cm, respectively.

Furthermore, the samples used for chemical and crystallinity composition observation were divided into three parts, namely bottom (B), middle (M), and top (T) as presented in Figure 2.

**Figure 1.** Bamboo clumps and bamboo middle culm cross-sections.

**Figure 2.** Bamboo culm parts (bottom, middle, and top) for analysis of chemical components and physical–mechanical properties of bamboo.

## *2.2. Methods*

2.2.1. Chemical Component Analysis

Material Preparation

Sample preparation was performed according to the standards of the Technical Association of the Pulp and Paper Industry (TAPPI) T 257 cm-02 [23] and T 264 cm-97 [24]. Furthermore, samples were mashed using a ring flaker/hammer mill/disk mill until all filtered through a sieve, number 40 mesh.

Determination of Chemical Components

a. Acid Insoluble Lignin Contents

This test was performed based on National Renewable Energy Laboratory (NREL) Laboratory Analytical Procedure (LAP) 003 standard [25]. Empty filter funnel 1G3 was dried in an oven at 105 ◦C for at least 4 h before testing, cooled in a desiccator for 30 min, and weighed in the dry weight of the oven. Furthermore, a total of 0.3 g of the extractive free sample was weighed and put in a small vial with a wide mouth of ±20 mL, and the water content was measured based on TAPPI T 264 cm-97. In addition, it was added to 3 mL of 72% sulfuric acid (Merck, Darmstadt, Germany), stirred using a magnetic stirrer for 2 h with 320 rpm at room temperature (conditioned using a Petri dish filled with water), transferred to a 100 mL Duran bottle, and diluted using 84 mL of distilled water to a final concentration of 4% sulfuric acid (Merck). The sample was tightly closed and heated by autoclaving at 121 ◦C for 1 h. Furthermore, a total of ±10 mL was filtered using an IG3 glass filter with the help of a vacuum and stored for measurement of ASL. The samples in the IG3 filter funnel were washed with a minimum of 50 mL of hot water and dried in an oven at 105 ◦C for 24 h. Consequently, the sample was removed from the oven and cooled in a desiccator for 30 min, and weighed.
