Thermal bonding of polypropylene films and fibers

Abstract

The thermal bonding behavior of different grades of polypropylene was studied in this research. Initial bonding studies were done with polypropylene films of different grades of polymer with varying morphology, and the studies were extended to polypropylene fibers. Polypropylene fibers manufactured with different crosssections, deniers, polymer melt-flow rates, and different processing conditions were bonded under various conditions. The effect of film structure, properties, and bonding conditions on the bonding efficiency was studied by comparing the tensile strength of bonded films. Thermal bonding was carried for a range of temperatures covering poor, optimum, and over bonding. Changes taking place to the polymer in bond point and the original surface were analyzed using the SEM. Higher bond strength was observed in the vicinity of melting temperature and the strength reduced with a further increase in bonding temperature. The frequent failure point was observed at the bond edge crossover points where film undergoes maximum thickness transition. Lower pressure and shorter time were found to be appropriate for bonding. Films with lower orientation formed better bonds. The optimum bond strength and the optimum bonding temperature observed were different for different polymers. Fiber bond strength results were similar to the results observed in the case of films with respect to the bonding temperatures studied.

Strength of fibres in low-density thermally bonded nonwovens: An experimental investigation

“…The results reported here are in good agreement with the previous work [5, 6, 8, and 10]. The reason for the decrease in failure parameters of processed fibres is the rapid change in the orientation of their molecular chains at bond edge since the chains of polymers relax and diffuse due to high temperature and pressure during bonding process [5][6][7][8][9][10][11]. These molecular chain segments are cocrystallized to form the bond.…”

“…Many researches were conducted to investigate the effect of bonding temperature on mechanical performance of nonwovens and their fibres during thermal bonding. According to literature, most of the fibres fail at bond periphery in well-bonded and over-bonded fabrics due to a rapid change in molecular orientation of fibres at bond edge [5][6][7][8][9][10][11], leading to reduction in modulus and yield strength of fibres at the bond edge. All these studies emphasize the origin and reasons of fibre failure in thermally-bonded nonwovens in tension rather than quantifying the loss of strength in a single fibre in terms of stress and strain.…”

Nanoparticle effects on the morphology and mechanical properties of polypropylene spunbond webs

“…Die block assembly consists of feed distribution and spinneret. Feed distribution manages the uniform distribution of melt all the way through the width of the die block 22. The polymer melt is forced by spin pumps (3) through a special spinneret (4) which consists of single metal block with thousands of very precisely drilled orifice.…”

Meso-scale deformation and damage in thermally bonded nonwovens

“…The material properties of fibres, especially their failure strength in terms of stress and strain within a thermally bonded fabric, are significantly lower than those of virgin fibres due to their thermal exposure during the bonding process [4][5][6][7][8][9][10]27]. Therefore, a pragmatic approach is to use in tests individual fibres extracted from the fabric rather than unprocessed fibres in order to obtain the material properties and to develop damage criteria.…”

“…This bonding process affects the strength of fibres within the fabric resulting in a significantly lower fibre-failure stress threshold and strain at that stress [1][2][3][4]. Since fibres always fail near the bond-point's periphery region in thermally bonded nonwovens [4][5][6][7][8][9][10], therefore, it is necessary to study this region for better understanding of damage initiation and propagation in this kind of fabric. The consideration of this region in the development of damage criteria for an individual fibre within the fabric is a challenging task which is implemented by a novel experimental technique.…”