Effect of boron and phosphate compounds on physical, mechanical, and fire properties of wood–polypropylene composites
Highlights
► The WPCs with the zinc borate had the highest water resistance and strength values. ► Best fire performance were achieved with the phosphate treatments. ► Surface of wood fibers was coated by some crystalline deposits of fire retardants.
Introduction
Wood–plastic composites (WPCs) represent an emerging class of materials that combines favorable performance and cost attributes of both wood and thermoplastics. Lignocellulosics are increasingly applied for reinforcement in thermoplastics such as polypropylene and polyethylene due to wood’s low density, good thermal insulation and mechanical properties, reduced tool wear, unlimited availability, low price, and problem-free disposal [1]. Wood flour is the most common lignocellulosic used in WPCs. It is a commercially available material sourced from industrial residues such as planer shavings, sawdust, and wood chips and ground to a consistent mesh size. WPCs are stiffer, exhibit less creep, and are more dimensionally stable than unfilled plastic lumber.
Current growth rate of the WPC market is 22% for North America and 51% for Europe [2]. Decking for outdoor applications represent the largest market for WPCs both in North America and Europe and in both regions growth is most rapid in the decking segment [3]. WPC market share in the European decking sector is estimated to be around 6%. In Europe, total WPC production amounts to 120 thousand tons (excluding product destined for the auto industry). Around 68 thousand tons of this production is currently destined for the decking sector. The positive growth in WPC decking has led manufacturers to introduce residential construction applications include siding, roofing, windows, door frames, and outdoor furniture. Further expansion into the residential construction industry and development of applications for the furniture industry require an understanding of the fire performance of the WPCs. As organic materials, i.e. both polymers and wood, are sensitive to fire, improvement of fire retardancy of the composite materials has become important in order to comply with the safety requirements of the WPC products. Polymers employed in WPCs, burn and drip in case of fire leading to a very risky scenario. Thus, FR agents must be employed in order to improve fire behavior. The fire performance of WPCs is not well understood, and there is little information regarding the effectiveness of various FRs in the public domain.
Even though a lot of work has been reported on the fire properties of thermoplastics [4], [5], [6], [7], effect of FRs on the technological and fire properties of the wood flour reinforced thermoplastic composites only now is being more extensively investigated. The primary objective of this study was to determine effects of the boron compounds and phosphate compounds on the physical, mechanical, and fire properties of the injection molded WPCs with and without a coupling agent. The physical properties of natural fiber/polyolefin composites can be greatly enhanced by a coupling agent [8]. There is no any study related to effects of coupling agent content on the physical, mechanical, and fire properties of the WPC with FRs. The secondary objective was to investigate effect of the coupling agent content on the properties of the WPCs with FRs.
Section snippets
Materials
Wood particles were obtained from beech (Fagus orientalis Lipsky) lumbers by using laboratory type disk chipper with three knives. The moisture content of the wood particles, as determined by oven-dry weight, was found to be 40–50% prior to the treatment. The wood particles were ground in a laboratory Wiley grinder. The wood flour passing through a US 35-mesh screen was retained by a US 80-mesh. The wood flour was dried in a laboratory oven at 102 °C for 24-h to a moisture content of 0–1% based
Physical properties
The TS and WA values of the untreated and FR-treated WPC specimens without the coupling agent (MAPP) are presented in Table 2. As compared with the control specimens, the water resistance of the uncoupled specimens significantly decreased with increasing the FR content. However, the water resistance improved with the addition of the coupling agent and when the MAPP and the corresponding FR contents were increased from 2 to 4 wt.% and 4 to 8 wt.%, respectively (Table 3). The significant
Conclusions
The following general conclusions can be drawn from the study provided in the paper:
- 1.
Compared with the control WPCs, incorporation of the boron and phosphate compounds and the corresponding reduction in the wood flour content decreased the water resistance and mechanical properties of the uncoupled WPCs, except for the MOE. The WPCs with ZB had the highest water resistance and mechanical properties followed by the MAP, BX/BA, and DAP treatments.
- 2.
The use of the coupling agent (up to 4 wt.%)
Acknowledgements
This work has been supported by the Research Fund of Istanbul University, Istanbul, Turkey. Project No: 2396. Its support is gratefully acknowledged. The authors would like to thank United States Department of Agriculture, Forest Service, Forest Products Laboratory for the cone calorimetry tests.
References (19)
- et al.
Composites reinforced with cellulose based fibers
Prog Polym Sci
(1999) - Haider A, Eder A. Markets, Applications, and processes for wood polymer composites (WPCs) in Europe. In: proceedings:...
- et al.
Wood–plastic composite lumber vs. wood decking: a comparison of performance characteristics and environmental attributes
(2010) - et al.
Evaluation of various fire-retardants for use in wood flour–polyethylene composites
Polym Degrad Stabil
(2010) - et al.
Flame retardant and mechanical properties of natural fibre–PP composites with magnesium hydroxide
Polym Degrad Stabil
(2004) - et al.
Utilization of boron compounds as synergists with ammonium polyphosphate for flame retardant wood–polymer composites
Turk J Agric For
(2011) - et al.
Effects of fire-retardants on physical, mechanical, and fire properties of flat-pressed WPCs
Eur J Wood Prod
(2012) - et al.
Maleated coupling agents for natural fibre composites
Composites Part A
(2004) - ASTM International. Standard practice for conditioning plastics for testing. ASTM D618-08, West Conshohocken, PA;...
Cited by (75)
Mechanical properties of energy sustainable round bamboo - Phosphogypsum composite floor slabs
2023, Journal of Building EngineeringEvaluation of the density, mechanical, thermal and chemical properties of babassu fibers (Attalea speciosa.) for potential composite reinforcement
2023, Journal of Materials Research and TechnologySemi-dry technology mediated lignocellulosic coconut and energy reed straw reinforced cementitious insulation panels
2022, Journal of Building EngineeringCitation Excerpt :Both natural materials have excellent properties (less sensitive to moisture, good strength values, mould and fungus resistance, etc.). Their combination is promising, but also raises problems, e.g. finding the right mix ratio [9–12]. Generally, lignocellulosic biomass materials are tightly packed with cellulose, lignin, and hemicellulose matrix in their polymeric structures [13–17].
Flame retardant effect of boron compounds in polymeric materials
2021, Composites Part B: EngineeringEffect of fiber size, cyclic moisture absorption and fungal decay on the durability of natural fiber composites
2021, Construction and Building MaterialsCitation Excerpt :The ZB addition reduced the bonding efficiency of the WF and polymer matrix by preventing the materials from being well-dispersed. This issue can be overcome by introducing MA into the formulation so that the interaction between the PP and WF is not interrupted [17]. The high magnification SEM pictures of wood and plastic interfaces are provided in Fig. S1.
- 1
Tel.: +1 608 231 9265; fax: +1 608 231 9303.
- 2
Tel.: +90 344 219 1000; fax: +90 344 219 1012.
- 3
Tel.: +90 380 541 37 23; fax: +90 380 541 37 78.