Relationships between the properties of fibers and thermally bonded nonwoven fabrics made of polypropylene

Abstract

SYNOPSISTypical polypropylene fibers for use in light nonwoven fabrics were produced in a fullscale compact-spinning line. Molecular weight distribution (MWD), extrusion temperature, draw-down ratio, and draw ratio were varied. The fibers were thermally bonded (welded) into nonwoven fabrics, at different bonding temperatures, using a pilot calender line. The tensile properties of the fabrics are influenced by the MWD and the processing conditions of the fibers, and the effects of these fiber parameters increase with increasing bonding temperature. The fabric strength increases with increasing MJM,, decreasing draw ratio, and increasing extrusion temperature, while in all these cases the fiber strength generally follows the opposite trend. Furthermore, the fabric strength, as well as the fiber strength, have a maximum as a function of draw-down ratio. The tensile properties of the fabrics seem to be governed by the bonding properties of the constituent fibers, not the fiber strength per se. Bond characteristics are discussed in terms of skin-core structures. Some details of the macroscopic fracture mechanisms of fabrics were revealed by scanning electron microscopy and the shape of load-elongation curves. 0 1995 John Wiley & Sons, Inc.

Strength Loss in Thermally Bonded Polypropylene Fibers

“…Of the three available process variables, temperature, pressure and roll speed, only temperature was varied in this work. Prior studies [1,2] had showed pressure was not a particularly important variable in bonding, and roll speed was set to give a commercially realistic contact time of 9 ms. A critical temperature range was identified for each item tested based on scouting experiments, and this range was studied in detail. Fibers used in this work did not seem to stick to the Kraft paper.…”

Sheath−Core Differences Caused by Rapid Thermoxidation during Melt Blowing of Fibers

“…This process can occur without damaging the structure of the core polymer. A commercial example of a sheath-core fiber is Himont's Moplefan fiber (Andreassen et al, 1995a) which has a polypropylene core and a polyethylene sheath. Jeffries (1971) mentions that sheath-core structures in a single polymer are possible.…”

“…Recently, Andreassen et al (1995a) studied the interrelationship between fiber properties and nonwoven fabric strength. They theorized that sheath-core differences in melting point could be caused by differences in molecular weight, crystal size, crystal order, and orientation.…”

Study on bonding ability of melt-spun polypropylene/polyethylene blend fibers

“…These results are in strong correlation with the birefringence data. Overall, higher elongations at break are preferred as it leads to homogenous force distribution during bonding [54]. Figure 6 demonstrates the tensile strength of the fibers before bonding and after bonding at different temperatures (145, 150, and 155 � C bonding temperatures).…”