3.4. Tensile tests
The dry tensile index values for the coated samples shown in Fig. 5 suggestthatthere was about 15–20% decrease in tensile index for PVA and modified DG gum coated samples from base paper at 14 g/m2.
No significant difference was observed among the tensile index values for DG gum at different coating weights.
Although high tensile index was not expected with this particular coating formulation,
the comparison allowed ascertaining that in terms of tensile index DG gum based coatings and PVA based coatings were
comparable.
Wet strength of the samples is expressed in terms of wet/dry strength ratio, which is the wet tensile strength expressed as a percentage of the dry tensile strength,
shown for the samples in Fig. 6. Paper consists of a network of cellulosic fibers,
which are bonded together by interfiber hydrogen bonds which are broken when subjected to high humidity or wet conditions.
Wet strength is imparted on to paper by introducing covalent bonds by the addition of “wet-strength additives”.
A high wet/dry ratio is preferred for applications such as packaging,
towels or bags that will be used under wet conditions.
Low wet strength with increasing coating grammage for all samples suggests that hydrogen bonding is still the predominant basis of the structure.
DG gum based samples showed consistently lower values than PVA based samples,
however modified DG gum based samples were comparable to PVA samples.
3.4. Tensile testsThe dry tensile index values for the coated samples shown in Fig. 5 suggestthatthere was about 15–20% decrease in tensile index for PVA and modified DG gum coated samples from base paper at 14 g/m2. No significant difference was observed among the tensile index values for DG gum at different coating weights. Although high tensile index was not expected with this particular coating formulation, the comparison allowed ascertaining that in terms of tensile index DG gum based coatings and PVA based coatings werecomparable.Wet strength of the samples is expressed in terms of wet/dry strength ratio, which is the wet tensile strength expressed as a percentage of the dry tensile strength, shown for the samples in Fig. 6. Paper consists of a network of cellulosic fibers, which are bonded together by interfiber hydrogen bonds which are broken when subjected to high humidity or wet conditions. Wet strength is imparted on to paper by introducing covalent bonds by the addition of “wet-strength additives”. A high wet/dry ratio is preferred for applications such as packaging, towels or bags that will be used under wet conditions. Low wet strength with increasing coating grammage for all samples suggests that hydrogen bonding is still the predominant basis of the structure. DG gum based samples showed consistently lower values than PVA based samples, however modified DG gum based samples were comparable to PVA samples.
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