THE PHOTOMICROGRAPHY OF A JACK PINE SULPHATE PULP
PROCESSED IN ROD MILLS AND JORDANS
By
F. A.
A Wisconsin paper company employs a combination of
rod :iills and jordans as a means of processing pulp for the
In order to determine if this processing was
paper machine.
modifying the fiber size and surface characteristics in a
way most likely to result in a paper of maximum strength
properties, a microscopic study of the stock was made.
Seven samples were selected at significant steps
to paper
during the conversion of a jack pine sulphate
of
photo—
for recording the visual characteristics by means
micrographs.
Procedure and
Data
each sample was prepared and stained
The seven slides
of saf±'ranine dye.
in the order of increasing severity of process-
One slide from
with
were
a dilute solution
treatment until the progressive change in the visual characteristics of the stock effected by this processing was recognized. A representative field from each slide was then selected
and photographed by the apparatus shown in Plate I at a :eagnification of 105 diameters. In Plate II are found the photo—
micrographs obtained, numbered in order of degree of process—
ing
lug.
In Table 1 are recorded data obtained by the paper
company concerning the effect of processing by means of a
laboratory
size Valley Iron Works beater on the strength—
producing properties of the pulp before rod milling, after
treatment in one rod mill, and after treatment in three rod
mills.
lAssistant Chemist, U.S. Forest Products Laboratory, Madison,
Wi S.
R933
—52—
c
Plate 1.—Apparatus used to make photomicrogi'aphs.
developed
Table 1.
Processed by
Unprocessed
Beating:
time
:Bursting: Tearing
:
one rod mill
Processed by
:
three rod mills
:
:
:Bursting: Tearing :Bursting:Teariflg
strength: strength: strength: strength: strength
factor factor factor factor : factor factor
strength:
Minutes:
0
15
30
45
0.41
:
:
:
60
75
Points
:
:
.97
1.29
1.57
1.55
per
pound per
2.33
0)68
1.32
1.53
1.50
:
1.33
1.41
:
:
.
:
:
:
:
:
:
:
:
1.54
1.60
1.55
:
:
:
:
x 36 —
2.29
1.38
1.33
1.28
1.41
0.77
1.52
:
:
1.50
:
1.62
;
1.64
....: .....,..:
:
:
1.78
:
2,18
:
1.44
:
1.32,
1.30
1.27
1.16
:
:
:
A partial analysis of a sample of the paper made
from the pulp processed by three rod mills and four jordans
yielded the data recorded in Table 2.
Table 2.——Certain properties of a lack pine
Basis weight (24 x 36 — 500)...........Pounds
Points
Thickness
Bursting strength....Points per pound per ream
24 x 36 — soo
.Number
Double folds
Tearing strength.....Points per pound per ream
24 x 36 — 500
Meters
Tensile strength
Size number
Kind of size
.
.
.
66.0
5.6
0.89
1731
2.30
5975
2.2
Rosin
Interpretation of the Data
The photomicrographs indicate that the processing
of increasing severity has affected the surface characterisThe principal effect
their size.
tics of the fibers more
appears to have been a loosening up and working out of the
first two or three outer layers of fibrils of the cell walls.
instances the fibers have been split lengthwise, thus
In
Naturally, some reduction of fiber
opened up as ribbons,
R933
—53—
'55 ML F
1.
Through one rod mill
Unprocessed
3.
Throuvh two rod muss
MiltieF
4.
Through ttrss rod milss
5.
Through taxis rod malls
ltd four Jordsms
of
/4>
44
Jack Pine Sulphate Puly,
Processed by Rod Mune
$fld Jordans
Plate
7.
t:
'li-
4 after
length occurred, but the fact that the further treatment of
the rod—milled puips in the laboratory size beater produced
strengths than
a stuff of higher bursting and lower
the paper made from the stuff processed by three rod mills
and four jordans suggest that the processing was one of
mainly fibrillation.
It is possible that a higher bursting strength
could have been secured had the stock been cut more in the
This would. have resulted. in a lower tear, but one
jordans.
probably not below the limits of the re0uirements for use.
P.933
—54—