47 rate of 10 to limit lathe check growth and thickness variation Lutz 1974; Feihl
1986; Marchal et al. 2009. Those veneers were used to produce 50x50 cm LVL.
4.5.2 LVL production of poplar and douglas-fir LVL 4.5.2.1 Veneer selection and panel composition of poplar cultivars
Before peeling, each log was was holed by 1 cm diameter drill bit from bark to pith, to mark the radial segment of veneers sample. Each cultivar of poplar logs
were peeled with 3 mm thickness. The logs were peeled until the core diameter of 14 cm. According to transition age resulted from fiber length trait see Chapter 2,
we divided poplar veneers into two types. First, veneers from mature wood taken from bark to 16
th
segmented rings. Second, veneers from juvenile wood taken from 15
th
segmented rings to core diameter. For each tree, logs were peeled with 3 mm and 5.25 mm thickness. Veneers were selected randomly in each category
juvenile or mature. LVLs of 7 layers of 3 mm veneer and 4 layers of 5.25 mm veneer were made, so that the target LVL thickness of 20 mm was achieved. We
made 188 LVL panels. Veneers were dried with a vacuum dryer to ensure a flat veneer surface dried until they reached 8 - 10 moisture content.
4.5.2.2 Veneer selection and panel composition of douglas-fir
The same with poplar, we utilized transition age based on fiber length trait see Chapter 2, to separate juvenile veneers from mature veneers. First, veneers
from mature wood taken from 21
st
segmented rings to bark. Second, veneers from juvenile wood taken from core diameter to 20
th
segmented rings. LVL with 20 mm in thickness were produced. Those LVL consisted of 7-plies of 3 mm
veneer and 4-plies of 5.25 mm veneers. Veneers were selected randomly in each category. Each board was cut into standardized test samples EN 789, parallel to
grain with total of 140 samples LVL of 3 mm veneer = 63 samples and LVL 5.25 mm veneer = 77 samples.
4.5.3 Gluing Process
PVAc Poly Vinyl Acetate was used as the adhesive. The vinyl adhesive that we used was marketed under the name Rakoll® _GXL 4. It is in the form
of an emulsion and ready for application. The PVAC resin had pH 3.5. Table 9 summarizes the conditions of the gluing process for poplar cultivars and douglas-
fir LVL.
Table 9 Condition of gluing process of poplar cultivars and douglas-fir
laminated veneer lumber from 3 mm and 5.25 mm veneers
Gluing parameters Poplar and douglas-fir LVL from
3 mm and 5.25 mm veneer Veneer moisture content
10 – 15
Room temperature during gluing process 18 - 20°C
Relative humidity RH 60
– 65 Average adhesive spreading rate gm
-2
260 Application instrument
Glue machine Figure 24a Open assembly time
10 minutes Cold press Figure 24b pressure
2.5 kgcm
-2
Cold press pressure time 45 minutes
