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PAM solution was prepared by dispersing 3 ww of PAM in 100 ml tap water on an oven dried pulp. The
same method is practiced to prepare the PEI solution. Meanwhile 24g of pulp was dispersed in 1600 ml of
tap water and disintegrated for 5 minutes to ensure
that all the ibres were well dispersed. The handsheet samples had been prepared in 7 conditions:
1. Handsheet using 100 pulp 2. Handsheet with mixture of pulp and laboratory
PCC 3. Handsheet with mixture of pulp and commercial
PCC 4. Handsheet with mixture of pulp, laboratory PCC
and PAM 5. Handsheet with mixture of pulp, commercial PCC
and PAM 6. Handsheet with mixture of pulp, laboratory PCC
and PEI 7. Handsheet with mixture of pulp, commercial PCC
and PEI Pulp suspensions were disintegrated in
disintegrator until complete 2000 rev which was about 20 minutes. This stage is also called as impregnation
stage whereby the PCC suspension was added into the pulp suspensions and disintegrated together.
For the samples 4 and 5 the pulp suspensions were treated with PAM solution and for the samples 6
and 7, the pulp suspensions were treated with PEI solution after impregnation process. The handsheets
prepared were then dried at room temperature and ready for mechanical and physical testing and also the
morphology test.
3. Results and Discussion 3.1 Zeta Potential
Figure 1a shows the zeta potential results for ibres, laboratory PCC using sucrose solution method
and commercial PCC. All the samples were tested at pH range of 3 to 11. The results portray that the zeta
values for ibres and laboratory PCC are negative at all pH. As for the commercial PCC, the zeta potential
gives positive reading within the range of pH 3 to 9. However the zeta value is negative at pH 11. Based on
Ono and Deng [16], the zeta potential of PCC becomes negative when pH increases which is attributed to the
decrease of Ca
2+
concentration in the solution. As stated earlier, laboratory PCC using sucrose solution
method give the negative reading for all pH. This result is differ with the laboratory PCC prepared by
using conventional method. Figure 1b shows the results of zeta potential for both types of PCC for
comparison purpose. Due to the negatively charge of laboratory PCC prepared by sucrose solution method,
cationic polyelectrolyte had been used in papermaking process.
a
b Figure 1: Zeta Potential of a Fibres, PCC using
Sucrose Solution Method and Commercial PCC, and b Comparison of Zeta Potential Values
of Laboratory PCC using Sucrose Solution and Conventional Method
3.2 Paper Properties
Figure 2 shows the percent of loading degree of papers. The percent of loading degree or PCC content
or PCC retention on paper is affected by types of PCC and retention aids. Figure 2 show that the samples 6
7 which are prepared with the aid of polyethylenimine PEI record higher loading degree as compared to the
samples 4 5 that are using polyacrylamide PAM. PEI improves PCC retention more than PAM. Figure 2
also shows the sample that used commercial PCC with the aid of PEI has the highest loading degree which is
about 48.61 and the loading degree for the sample prepared from laboratory PCC and PEI is about
43.93. Meanwhile, Figure 3 shows the effect of percent loading degree on the paper apparent density.
Figure 3 shows that the higher the percent of loading degree the lower the paper apparent density. Beating
process is one of the factors that contributes to the
apparent density. In this study, the pulp ibres had been beaten for 6000 revolution. The beating process has
made the ibres become swollen and easily collapse,
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thus produced more compact paper. The adding of PCC has decreased the paper apparent density since
additional PCC has decreased the paper compactness.
Figure 2: Percent of Loading Degree of Papers
Figure 3: The Effect of Percent Loading Degree on Paper Apparent Density
Figure 4 shows the results of tear and tensile indices of the paper. It can be seen that the values of
tearing and tensile indices decrease with the addition of iller to the sheet formation. The addition of PEI
as retention aid did not contribute to both tearing and tensile indices of the paper. The lowest value for both
testing was recorded by sample number 7 which is using commercial PCC in the presence of PEI. From
the Figure 4, it also can be concluded that the sample that used laboratory PCC 2,4 6 had better results
of tear and tensile indices as compared to the sample that used commercial PCC 3,5 7.
Meanwhile, Figure 5 shows the effect of percent loading degree on tear and tensile indices of the
paper. The tearing and tensile indices had decreased when the PCC was added and kept decreasing with
additions of PCC. The presence of PCC in the ibre has modiied the structure by decreasing the compactness,
subsequently decreases the interibre bonding. The paper that contains a higher loading degree had
decreased the tearing and tensile strength of the paper. Figure 4: Tear and Tensile Indices of The Paper
Figure 5: The Effect of Percent Loading Degree on Tear and Tensile Indices of The Paper
Figure 6: Burst Index and Folding Endurance of The Paper
Figure 6 shows the results of burst index and folding endurance of the paper. The laboratory PCC
used in the samples 2,4 6 had demostrated better results in these two properties as compared to the
samples which are using the commercial PCC. When the comparison was made based on the function of
retention aids in paper, it was observed that PAM
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had better retention ability of PCC in paper rather than PEI. The lowest value in bursting strength and
folding endurance was in sample 7. This result is consistant with the reading of loading degree where
this sample had the highest percent of loading degree. The existence of PCC in large amounts had interfered
greatly in interibre bonding. This situation can be clearly seen in Figure 7. The bursting strength and the
number of folding endurance starts decreasing when the loading degree increases. PCC had interfered the
pulp ibre surfaces and ibre web in the sheet.
Figure 7: The Effect of Percent Loading Degree on Burst Index and Folding Endurance of The Paper
Figure 8: Percent of Brightness and Opacity of The Paper
The results of brightness and opacity of the paper are portrayed in Figure 8. It can be seen that
the brightness of the paper increased from sample 1 to 5. However, it dropped signiicantly for sample 6
and then increased slightly for sample 7. This can be concluded that the addition of PEI for the sample 6 and
7 had decreased the brightness of the paper. According to De la Orden [17,18], the photoyellowing effect can
occur due to the condensation of the primary groups of PEIs which react with cellulose carbonyl groups
to form coloured imines. This condition happens due to the paper is heated in air or dried at moderate
temperature. Meanwhile the results of opacity of the paper show the different pattern. The presence of the
PEI had increased the loading degree of PCC in paper and thus increased the opacity of the paper. This can
be concluded that the PEI had improved the opacity of the paper. This condition can also be related to the
loading degree of PCC in the paper as shown in Figure 9. It can be seen that the opacity had increased when
the percent of loading degree of PCC had increased. However the brightness of the paper increased at 20 to
30 of loading degree, and dropped when the loading degree increased more than 40.
Figure 9: The Effect of Percent Loading Degree on Brightness and Opacity of The Paper
3.3 Scanning Electron Microscopy SEM Analysis
