Thermoplastic polyolefins as formaldehyde free binders in highly filled lignocellulosic panel boards: using glycerine as a processing aid in kenaf fiber polypropylene boards

Abstract

A new technique was developed to make highly loaded (up to 95%) formaldehyde free natural fiber boards. The purpose of the paper is to report a broad study on 85% kenaf boards using linear thermoplastic polymers as the binder in preparing the boards to determine if these materials have potential in commercial applications by comparing them to other commercial materials. In these materials, linear thermoplastic polymer chains act as an adhesive and the product resembles a typical wood based panel (e.g., phenol formaldehyde fiber board). The process involved the use of small amount of glycerine in the fiber to enhance processibility in a thermo-kinetic mixer followed by hot pressing. In this paper, we report the properties of 85% by weight kenaf fiber boards using polypropylene as the adhesive. A maleated polypropylene was used to improve the adhesion and stress transfer between the adhesive and kenaf fiber. The addition of 2% by weight of glycerine based on the dry weight of kenaf fiber resulted in the best properties of the boards. Differential scanning calorimetric studies suggested that the glycerine had a little effect on the percent crystallinity of the matrix. Dynamic mechanical tests of the 85% boards showed some differences compared to conventional 60% by weight kenaf-PP composites. The 85% kenaf boards had a flexural strength of 75 MPa and a flexural modulus of 6.8 GPa with a specific gravity of 1.24. These properties are comparable to standard formaldehyde free high density hardboards with flexural strengths of 48.3 MPa and flexural modulus of 5.5 GPa, and a specific gravity of 1.28. This paper gives a broad overview of an initial study of these new materials.

Sugarcane bagasse fibers at high contents in thermoplastic composites: A novel approach using agro‐industrial residue via thermokinetic mixing

“…PP acts as an adhesive in this case, and not as a continuous, stress transfer phase, maintaining to some degree the stiffness of the fibers, which overlap in space. [9,24] F I G U R E 6 Effect of fiber content on flexural strength and flexural modulus of the composites. Mean values that do not share the same letter differ significantly by Tukey's test with α = 0.05 F I G U R E 7 Effect of fiber content on the Izod impact strength of the composites.…”

“…The fibers had an initial decomposition temperature of 258 C. The materials were mixed in a torque rheometer mixer at 180 C and hot-pressed at 10 MPa and 190 C. The composites achieved flexural strength and flexural modulus of 37 MPa and 1.3 GPa, respectively, and impact strength (IS) of 26 J/m. Sanadi et al [24] studied the incorporation of 85% wt kenaf fibers with PP-g-MA (maleated PP) and PP using a high-intensity thermokinetic mixer to mix at 5000 rpm and compression molding to prepare the composites. In general, the best results regarding flexural strength and flexural modulus were obtained using homopolymer PP, compression at 5.5 MPa, and addition of 2% wt glycerol.…”

Recent developments in biomass pelletization – A review

“…The bonding mechanisms have been the subject of only a few studies so far (Kaliyan and Morey 2010b;Lam et al 2011;Stelte et al 2011d). Nevertheless, a lot of knowledge can be transferred from related fields, such as pharmaceutical tableting (Hiestand 1997;Leuenberger and Rohera 1986), powder and agglomeration technology (Pietsch 2002), fiber board manufacturing (Bouajila et al 2006), wood-thermoplastic panel boards (Sanadi and Caulfield, 2008), wood welding (Delmotte et al 2008;Delmotte et al 2009;Mansouri et al 2010;Pizzi et al 2006), and materials science in general.…”

Effect of Fiber Treatment Condition and Coupling Agent on the Mechanical and Thermal Properties in Highly Filled Composites of Sugarcane Bagasse Fiber/PP

“…In general, the amount of fibers or fillers being used is generally limited to about 60% and below by weight of fibers in the thermoplastics 9 , such as wood plastic composites (WPC). WPC are used extensively throughout the world in both the furniture industries and building such as decking and siding 10 .…”