Page 56 - FDMAsia MayJun 2025

54 MATERIALS MAY/JUN 2025 FDM ASIA | www.fdmasia.com

Vecteezy Flat panels with final trimmed dimensions of 1220 mm ×
2440 mm × 6.35 mm were produced in a hot-press at WSU’s
CMEC. The panels were consolidated to a target density of
640 kg/cubic metre, with strands generally oriented along the

major axis or the longer panel dimension.
Polymeric methyl diphenyl diisocyanate (pMDI), at a loading
amount of 6 wt. percent of oven dry wood weight, was used
as the binder and the panels were hot-pressed at a platen
temperature of 171 deg C.
The PressMan software, integrated with the hot press, was
used to develop the press schedule where a consolidation
The primary objectives are to: time at the final thickness of six min was used.
1. Assess the recycling effects of re-resinated strands on During the process of blending, forming, and hot-pressing

panel performance, including bond performance among the panels, there are generally left-over resinated strands that are
strands and mechanical properties. usually considered waste and disposed of as landfill.
2. Understand the influence of recycling on the dimensional For the current study, these waste resinated strands,
stability of the panels. acquired only post blending, mat-forming, and preforming
3. Compare the fire performance of the panels made from processes, were accumulated and sieved to ensure no fines
control and re-resinated strands. and dust particles were present.
The sieved strands were then conditioned in a chamber

Materials And Fabrication Process at 65 percent relative humidity and 21.4 deg C for 30+ days
Low-quality Englemann spruce and lodgepole pine (ESLP) to emulate the longest possible interval between initial use
lumber, acquired from Idaho Forest Group, with an average and re-use times.
density ranging between 0.35 and 0.38 g/cubic centimetre, A similar panel consolidation process was then followed
were used to produce the required wood strands. to hot press 6.35 mm thick flat panels, which were 2440 mm
A CAE Disc Strander available at Washington State long and 1220 mm wide; strands were again oriented with
University’s (WSU’s) Composite Materials and Engineering respect to the major axis or the long dimension of the panel.
Center (CMEC) was used for processing the strands. A 6sixpercent pMDI resin content was used to re-resinate
Due to the maximum size limitation of the lab-scale CAE the strands. A mat was formed and hot-pressed with the

strander, the lumber needed sectioning at 140 mm before same press schedule and temperature as with virgin strands.
being soaked in water for three days to reach a moisture A vein box with a spacing of 76.2 mm between the
content higher than 50 percent before stranding. adjacent veins was used for orienting the strands. It should
The strander has a rotational speed of 500 revolutions be noted that studies have shown that the ideal gap between
per minute, and the blade gap was adjusted to produce the vein box and the surface of the mat being formed should
strands that were approximately 140 mm in length, 19 to 38 be maintained at around 76.2 mm during the entire mat
mm in width, and 0.38 to 0.51 mm in thickness. The strands forming process.

were initially air-dried and then conditioned to 10–12 percent However, in this study, the vein box was maintained at a
moisture content for three to four weeks before fabrication. fixed distance, thus this gap was not constant. This directly