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Chemical Treatment of Waste Abaca for Natural Fiber-Reinforced Geopolymer Composite

Published

4 years ago

August 5, 2017

Republished by Plato

. 2017 May 25;10(6):579.

doi: 10.3390/ma10060579.

Affiliations

¹ Chemical Engineering Department, De La Salle University, Manila 0922, Philippines. roy.malenab@dlsu.edu.ph.
² Chemical Engineering Department, De La Salle University, Manila 0922, Philippines. janne_ngo@dlsu.edu.ph.
³ Chemical Engineering Department, De La Salle University, Manila 0922, Philippines. michael.promentilla@dlsu.edu.ph.
⁴ National Research Council of the Philippines, Taguig, Metro Manila 1631, Philippines. michael.promentilla@dlsu.edu.ph.

Free PMC article

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Roy Alvin J Malenab et al. Materials (Basel). 2017.

Free PMC article

. 2017 May 25;10(6):579.

doi: 10.3390/ma10060579.

Affiliations

¹ Chemical Engineering Department, De La Salle University, Manila 0922, Philippines. roy.malenab@dlsu.edu.ph.
² Chemical Engineering Department, De La Salle University, Manila 0922, Philippines. janne_ngo@dlsu.edu.ph.
³ Chemical Engineering Department, De La Salle University, Manila 0922, Philippines. michael.promentilla@dlsu.edu.ph.
⁴ National Research Council of the Philippines, Taguig, Metro Manila 1631, Philippines. michael.promentilla@dlsu.edu.ph.

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Abstract

The use of natural fibers in reinforced composites to produce eco-friendly materials is gaining more attention due to their attractive features such as low cost, low density and good mechanical properties, among others. This work thus investigates the potential of waste abaca (Manila hemp) fiber as reinforcing agent in an inorganic aluminosilicate material known as geopolymer. In this study, the waste fibers were subjected to different chemical treatments to modify the surface characteristics and to improve the adhesion with the fly ash-based geopolymer matrix. Definitive screening design of experiment was used to investigate the effect of successive chemical treatment of the fiber on its tensile strength considering the following factors: (1) NaOH pretreatment; (2) soaking time in aluminum salt solution; and (3) final pH of the slurry. The results show that the abaca fiber without alkali pretreatment, soaked for 12 h in Al₂(SO₄)₃ solution and adjusted to pH 6 exhibited the highest tensile strength among the treated fibers. Test results confirmed that the chemical treatment removes the lignin, pectin and hemicellulose, as well as makes the surface rougher with the deposition of aluminum compounds. This improves the interfacial bonding between geopolymer matrix and the abaca fiber, while the geopolymer protects the treated fiber from thermal degradation.

Keywords: abaca (Manila hemp) fiber; chemical treatment; definitive screening design of experiment; fiber-reinforced composite; geopolymer; tensile strength; waste utilization.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

**Figure 1**

Waste abaca from Dumaguete, Philippines: (a) as received; and (b) segregated into 100 strands.

**Figure 2**

Chemical treatment and characterization of waste abaca fiber.

**Figure 3**

X-ray diffraction (XRD) peak deconvolution method to measure crystallinity index.

**Figure 4**

Three-point flexural strength test.

**Figure 5**

Actual vs. Predicted Plot (**– – – –** 0.05 significance curve; **– – – –**mean) for the regression model and the model coefficients.

**Figure 6**

Interaction plot matrix of the factors for chemical treatment of the abaca fibers.

**Figure 7**

Fourier Transform Infrared Spectroscopy (FTIR) spectra of: (a) untreated abaca; (b) NaOH-treated abaca; (c) NaOH + Al₂(SO₄)₃ treated abaca; and (d) precipitate or residue from the spent solution of Al₂(SO₄)₃ treatment.

**Figure 8**

XRD spectra of untreated (a) and NaOH-treated (b) abaca fibers.

**Figure 9**

Scanning electron microscopy (SEM) images at low and high magnification of raw (untreated), NaOH-treated and Al₂(SO₄)₃-treated abaca fibers: (a) raw (untreated); (b) NaOH treated; (c) without NaOH pretreatment; 12 h soaking; final pH = 6; (d) with NaOH pretreatment; 12 h; pH = 6; (e) without NaOH pretreatment; 12 h; pH = 4.5; and (f) with NaOH pretreatment; 0.5 h, pH = 6. Low and high magnification are labeled as “1” and “2”, respectively.

**Figure 10**

Sample EDS spectra of: (a) NaOH-treated; and (b) Al₂(SO₄)₃-treated abaca.

**Figure 11**

Thermograms of: (a) untreated; (b) treated solely with Al₂(SO₄)₃; (c) alkali-pretreated; and (d) alkali and Al₂(SO₄)₃ solution-treated abaca fiber samples.

**Figure 12**

Fracture surface of pristine geopolymer, reinforced with untreated abaca and reinforced with treated abaca.

**Figure 13**

SEM images of composite fractured surfaces: (a) reinforced with untreated abaca; (b) reinforced with treated abaca; (c) interface between untreated abaca fiber and geopolymer matrix and (d) interface between treated abaca fiber and geopolymer matrix.

**Figure 14**

SEM image (a) and thermogram of untreated abaca fibers and treated abaca fibers (b) from the geopolymer composite.

Cited by 1 article

Evaluation of Interfacial Fracture Toughness and Interfacial Shear Strength of Typha Spp. Fiber/Polymer Composite by Double Shear Test Method.

Ikramullah, Rizal S, Nakai Y, Shiozawa D, Khalil HPSA, Huzni S, Thalib S. Ikramullah, et al. Materials (Basel). 2019 Jul 10;12(14):2225. doi: 10.3390/ma12142225. Materials (Basel). 2019. PMID: 31295885 Free PMC article.

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