The coated multifilament yarns have higher maximum elongation compared to uncoated samples. This could be explained by their higher specific surface area. It may also be attributed to a better orientation of the atoms of the polymer. This would lead to less break stress, or undermining. It also facilitates better adhesion between individual filament strands.
The maximum elongation of the filaments was measured and compared with the standard spool weight of 5.5 kg. The spool weights were then averaged to calculate the mechanical properties of the different samples. Resulting values were divided by the number of filaments to calculate the tear strength of the different samples. The results showed that both samples exceeded 300% of their maximum elongation before fracture.
Monofilament fibres are very strong and are capable of functioning on their own. However, it is often difficult to predict the atomic structure of polymeric fibres. The fibres are typically coated in a thin layer to prevent capillary forces between filaments. This coating can be seen as a stitched texture on the outer surface of the yarn. It is this coating that increases the wettability of the polymer and explains the measurement of elongation in the coated multifilament yarns. The thinner the coating is, the lower the elongation.
The r-PVB coating agent can be used to coat polyester and polyamide yarns. The coating is applied at a high temperature, 160 degC, which activates the crosslinking reaction. During this process, the r-PVB polymer is bonded to the single strands of the filaments, producing a uniform coating. The amount of crosslinking agent that is used in the coating dispersion is determined by the coating weight. The higher the coating weight, the more crosslinking agent that is used in the dispersion. The higher the crosslinking agent, the more uniform the coating is.
The ultimate tensile strength of the multifilament fibres was higher than the monofilament fibres. The increase in ultimate tensile strength can be attributed to the increased crystallinity. The drawing process can also increase the percentage crystallinity of the filaments. The crystallinity is an undermining factor. It can result from the improved molecular orientation or the drawn process.
The results showed that all the fibers extended more than 300% before fracturing. Several factors were responsible for this. The maximum elongation of the coated monofilament yarns was approximately 60% greater than the uncoated fibres. This was due to the thickness of the coating and the coating weight.
