Qualitative Differences and Emission Persistence of Volatile Organic Compounds from Bio-Based Particleboards

Abstract

An attempt to reduce, replace, or even eliminate the synthetic resins from wood-based panels alongside broadening the array of raw lignocellulosics is still essential and attractive. Many pretreatments of lignocellulosics have been studied, among which steam explosion (SE) resulted in superior physical-mechanical properties of the obtained binder-less boards. However, the SE pretreatment leads to a relatively strong odor, which is even emitted from the obtained binder-less boards independent of the raw lignocellulosic, raising concern about the use of the boards. Emissions of volatile organic compounds (VOCs) were investigated in the framework of the study from binder-less boards obtained from different SE raw lignocellulosics and SE-untreated suberinic acids-bonded particleboard. VOCs were collected by headspace solid-phase microextraction (HS-SPME) and analyzed by gas chromatography-mass spectrometry (GC-MS) for 28 days with an interval of 2 weeks. The results showed that the number of detected VOCs and their chromatographic peak area varied significantly depending on the raw lignocellulosic, board density, and post-treatment (overlayering), decreasing over time. The lowest area of detected VOCs was demonstrated by the suberinic acids-bonded particleboard, while the highest area was detected from the high-density binder-less board obtained from SE hemp shives with the main compound of furfural (up to 70%) in all board types.

Keywords: binder-less particleboard; gas chromatography–mass spectrometry (GC–MS); headspace solid-phase microextraction (HS-SPME); lignocellulosics; steam explosion pretreatment; suberinic acids-bonded particleboard; volatile organic compounds (VOCs).

Figure 1

Weighed board specimens in closed vials.

Figure 2

The GC–MS chromatograms (TIC—total ion current) of the VOCs from different board samples: 1—acetic acid; 2—hexanal; 3—furfural; 4—2-furanmethanol; 5—1,3-propanediol; 6—α-pinene; 7—γ-butyrolactone; 8—5-methylfurfural; 9—sylvestrene; 10—nonanal.

Figure 3

Examples of different chemical species detected in VOCs emitted from the bio-based particleboards.

Figure 4

Semi-quantitative comparison of the total VOCs and the furfural fraction emitted from the bio-based boards after days 1, 14, and 28, depending on the raw material, density, thickness, and overlaying. Binder-less boards from (A) hemp shives, (B) wheat straw, (C) grey alder and birch wood, (D) suberinic acids-bonded and commercial particleboards.

Figure 5

Derived thermogravimetry of steam-exploded (220 °C/2 min) HS and WS samples.