1. Introduction
Technical/high-performance fibers are mostly used to manufacture technical products. These specialized products are used in sports, packing, agriculture, construction, hospitals, industries, automobiles, etc. [
1,
2]. Researchers have been pushed to produce technical textile items by ever-increasing human needs. The selection of materials, manufacturing techniques, and yarn and fabric characteristics are the major parameters which govern the performance of gloves against mechanical risks, as well as their hand performance. A glove that has improved cut protection ability without hindering hand movement is a desired solution for occupational health and safety applications [
3].
Cut and needle stitch injuries have a potentially fatal danger to pathologists and surgeons. Such injuries were evaluated by the German institute of pathology from 2002 to 2007 [
4]. It was concluded that the introduction of cut-resistant gloves prevented hand injuries. Cut-resistant gloves proved to be cost-effective personal protective equipment (PPE) compared to the medical and administrational costs of such injuries [
5]. The risks that are commonly faced by health care workers, butchers, and sewing professionals include needlestick and sharp cut injuries [
6]. A lot of work has been carried out on cut protection, while other aspects of mechanical risks, including puncture and tear resistance, have been almost neglected as a combined focus along with cut protection [
7].
High-strength fibers such as Poly Para-Phenylene Terephthalamide (para-aramid) and ultra-high-molecular-weight polyethylene (UHMWPE) are ideal materials for protective clothing. These high-performance materials have advantages over steel and other metals due to their higher strength-to-weight ratio. These fibers are flexible and exhibit high cut resistance properties. The materials’ inherent cut-resistant properties significantly affect their performance and application areas. Inorganic fibers provide better cut resistance than organic fibers. This is because of two different factors: First, inorganic fibers like glass have higher hardness levels compared to organic fibers like para-aramid [
8]. A blade penetrates organic fiber due to its sharpness, while it becomes dull when it comes into contact with inorganic fibers. A study reported that poly-p-phenylene benzobisoxazole (PBO) (Zylon
®) has superior cut resistance compared to para-aramid (Kevlar) and UHMWPE at different cut angles [
9]. Aramid, glass, and steel are considered materials with a high cut performance. Steel is used as a core filament for the commercial production of cut-resistant gloves [
10]. A study reported that increasing the glass core size resulted in an increase in the tensile strength and tenacity of the yarn, whereas increasing the steel core size resulted in a decrease in the tensile strength and tenacity for the same yarn count [
11]. Furthermore, composite yarns with glass cores had greater tensile strength and tenacity than composite yarns with steel cores. Changing the glass core size had an insignificant effect on the elongation at break and time to break of composite yarns. However, increasing the steel core size resulted in an increase in the yarn’s elongation at break and time to break. The intrinsic properties of materials may vary the cut resistance responses for different testing standards such as ASTM F1790, ISO 13997, and BS EN 388. It has been reported that the cut resistance of steel behaved almost similarly for ASTM, ISO, and EN standards, while in contrast, glass-reinforced structures provided different results for different standards [
12].
The cut resistance of hybrid yarns decreases with the increase in yarn count [
13]. Core sheath structures provide better cut resistance performance than single yarns [
14,
15]. It was reported that dual-core hybrid yarn provided better protection against mechanical risks. Such structures may increase the fabric thickness, thereby reducing the hand performance [
16]. The yarn twist has an indirect relation with the cut resistance of core sheath yarn structures [
15]. The knitting structure also influences the cut performance characteristics [
17]. The energy that is required to cut through the material depends on the coefficient of friction and consists of two components: the lost energy exerted by the material on the blade sides and the cutting energy at the edge of blade. These have opposite effects on the cut resistance of the material. An increase in dissipated energy increases the cut resistance. With an increase in the coefficient of friction, the cut resistance may be enhanced or reduced depending on the thickness and structure of the material [
17].
A study stated that a good puncture resistance of woven fabric was achieved by the use of a combined UHMWPE core–para-aramid sheath weft yarns compared to 100% para-aramid and para-aramid–glass combinations. The puncture resistance decreases with an increase in the ratio of the core filament. With a decrease in the core–sheath ratio, the weight and thickness of a hybrid yarn increases, which ultimately results in improved cut, abrasion, and puncture resistance properties. Para-aramid–UHMWPE yarn formed fabric achieves high cut, abrasion, and puncture resistance and is recommended for different applications like automotive, glass, steel, and metal work [
13].
From our literature review, it was observed that no study has reported the mechanical risk protection, including blade cut resistance, coupe cut resistance, tear resistance, and puncture resistance, of gloves with respect to the linear density of the sheath fibers, use of different materials as core in yarns, no. of plies in the resultant yarn, and gauge of the glove-knitting machine. The objectives of this study were to examine the influence of different materials, fiber linear densities, core yarn structures, and fabric structural parameters on the protection against different mechanical risks. This will help develop protective gloves with optimum protection properties.
3. Results and Discussion
Minitab statistical software ver. 17 was used to analyze the data. A response surface regression analysis was performed. The factors and interactions with
p-values above α-level (0.05) were considered non-significant and therefore removed from the analysis. The analysis of variance and model summary analysis are given in
Table 5 and
Table 6, respectively, for all the test methods.
As per the results shown in the ANOVA in
Table 5, it was observed that the yarn core and glove areal density (GSM) had a statistically significant effect on all the tested properties. In contrast, the number of yarn plies had significant effects on the blade cut, coupe cut, and tear resistance properties. In addition, the effect of the fiber linear density was found to be significant for the coupe cut and tear resistance properties only. The R-square values obtained for all response parameters were high, which explains why most of the variations in the test results are explained by the input factors (
Table 6).
Figure 2 shows the main effect plots of the fitted mean values for all test types. It was observed that the number of plies had indirect relationships with the blade cut, coupe cut, and tear resistance properties. The highest indirect relation effect was observed for the blade cut resistance, followed by a sharp slope down to the tear resistance and coupe cut resistance results. In contrast, the glove areal density (GSM) showed indirect relationships with all the tested properties. The highest effect was observed for tear resistance, followed by puncture resistance, coupe cut resistance, and blade cut resistance in order. Furthermore, an indirect relationship was observed between the fiber linear density and tear resistance, while a direct relationship was observed with the coupe cut resistance results. The influence of the core materials was also found to be significant and sharp for different material types. The glass core provided the best results for coupe cut resistance, while the steel core showed the best results with regard to the blade cut resistance properties. The tear and puncture resistance properties were found to be high using a UHMWPE core.
3.1. Blade Cut Resistance
The ANOVA results suggested that the core material and number of plies have significant linear inverse relationships with the blade cut resistance values, while a non-significant direct linear relationship was found for the machine gauge (GSM). The reason may lie in the fact that the material hardness and ductility are the prevailing factors governing the blade cut resistance results. The ductility and material hardness properties play vital roles in the blade cut resistance performance. The ductility helps in the formation of a loop upon the application of applied forces during cutting, which may resultantly consume applied energy to resist cuts in the structure. Organic materials have lower levels of hardness compared to inorganic materials, which means that steel cores have shown the highest blade cut resistance, followed by glass and UHMWPE core-spun yarn structures. Furthermore, it is easier to cut finer filaments than a coarser filament, which is observed in the reduction in blade cut resistance with respect to plies, where the filament diameter reduces in double-plied yarns [
19]. In addition, blade slippage is more predominant in the case of single-plied cores than double-plied core-spun yarn structures, leading to a decrease in the blade cut resistance with the increase in the number of plies in core-spun yarn.
The interaction terms of the core material with the no. of plies and machine gauge were found to be significant, with
p-values below the α-level (0.05); therefore, the machine gauge was also considered a significant factor, despite its higher
p-value as a linear interaction (
Table 6). The interaction of the core with plies was found to have a direct relationship with the blade cut resistance, which explains why with the increase in the no. of plies, different materials behave differently. In other words, the coefficient of friction changes, hence causing a loss of the energy exerted by the material on the blade sides [
20]. It was also observed that the machine gauge and core material type have direct relationships with the blade cut resistance. This effect is explained based on the core sheath ratio, which is a significant factor influencing the cut-resistant properties.
The surface plots of the material properties vs. blade cut resistance are shown in
Figure 3. The results suggested that gloves made with two-ply core-spun yarn offer low cut resistance compared to single yarn. The horizontal blade cut resistance increases with the increase in the gloves’ GSM for glass and UHMWPE cores, while it reduces for steel-core glove structures. It was also observed that the steel core provided the highest value of cut resistance, followed by glass and UHMWPE in order. A good selection of manufacturing parameters with respect to blade cut resistance would be to use a steel core, with a single-ply yarn glove knitted with a lower fabric areal density. The regression equations developed for the blade cut resistance for different cores are as follows:
3.2. Coupe Cut Resistance
The ANOVA results suggested that the sheath fiber denier, core material, number of plies, and machine gauge have significant linear relationships with the coupe cut resistance values. The interaction terms of the sheath fiber denier with the machine gauge and core material were also found to be significant, with p-values below the α-level (0.05). In addition, the interaction of the machine gauge and core material were also found significant for coupe cut-resistant properties.
The fiber denier as a linear term and its interaction terms with the machine gauge and core type were found to be in direct relationships with the coupe cut resistance results. The coupe cut resistance increases with increases in the sheath fiber denier. Meanwhile, the number of plies and machine gauge were found to be in indirect relationships with the coupe cut results. Finer sheath fibers cover the core filament better than coarser fibers and therefore impart their contribution towards cut-resistant properties. The increase in the number of plies employs finer filaments, which are easier to cut compared with coarser filaments. The dense fabric structure reduces the slippage of yarns and hence reduces the blade slippage, which thereby reduces the coupe cut resistance values.
Figure 4 shows the effects of the fiber linear densities, yarn plies, and fabric GSM on the cut resistance by coupe tests of different core materials. The effect of a glass core material was observed to be higher than those of steel and UHMWPE core materials, which is in accordance with the literature [
21]. The reason lies in the fact that glass is a hard and brittle inorganic material which resists incision forces better than the other used materials. As this test method involves cutting with a circular rotating blade, stretching of the material may not occur. In such a case, a material’s resistance against a cut is more effectively ensured by glass due to its hard structure compared with steel filament. The graphical trends clearly show that the cut resistance increases with the increase in fiber denier. As a thick fiber is more resistant to cuts, better cut resistance values are obtained for thicker sheath fibers. Gloves made with two-ply yarns have lower coupe cut resistances compared to single yarn. This is also consistent with the trend for sheath fibers. The thicker material absorbs more energy and is more resistant to cuts than thinner filaments [
14]. The coupe cut resistance decreases with the increase in the fabric’s GSM. With an increase in areal density, the yarn slippage gaps reduce, and hence, the material will easily be cut. A good coupe cut resistance property will be achieved by using a core sheath yarn with a glass core with coarser Kevlar sheath fibers in a single-ply yarn, which should be used to develop a low-areal-density glove structure. The regression equations developed for the coupe cut resistance for different cores are as follows:
3.3. Tear Resistance
The ANOVA results explain the significant linear relationships of the number of plies, machine gauge, and core material with the tear resistance of glove structures. The interaction terms of the core material with the sheath fiber denier and machine gauge were also found to be significant, with p-values below the α-level. The effect of the sheath fiber denier, number of plies, machine gauge, and core material were found to be in indirect relationships with the tear resistance of the glove structures.
Figure 5 shows the effects of the sheath fiber linear densities, yarn plies, and fabric GSM on the tear resistance. Gloves made using two-ply core-spun yarns have inferior tear resistance to single-ply core-spun yarn. The tear resistance also increases with an increase in the fiber denier for UHMWPE-core and steel-core spun yarn glove structures, while it decreases for glass-core spun yarn structures. The reason lies in the smooth and slippery surface of the glass filament, which allows the sheath fiber to slip to form a bundle formation, which thereby increases the tear strength values. As the finer fibers are more flexible and can better group together in a bundle formation, this result is opposite to what was obtained for steel- and UHMWPE-core yarns. The highest tear strength was obtained for UHMWPE core-spun yarn gloves, followed by steel cores and glass cores in order. The reason lies in the mechanical behavior of the core material, where bending and elongation properties influence the tear resistance values. Glass, being a rigid material, resists bending, which means that the destruction of its structure occurs, which thereby reduces the tear resistance values. The GSM has a visible impact on the tear resistance, which increases with the decrease in GSM. The reason lies in the fact that at a lower areal density, more space will be available for the yarn to form a bundle formation by slippage during tear force application, which thereby enhances the tear resistance values, which is in accordance with previous results [
14]. The regression equations developed for the tear resistance for different cores are as follows:
3.4. Puncture Resistance
The ANOVA results demonstrated that the core material and machine gauge have significant linear relationships with the puncture resistance values, while non-significant relationships were found for the sheath fiber denier and number of plies. The two-way interaction of the machine gauge with the core material a showed significant effect on the puncture resistance, with a p-value below the α-level. It was also observed that the machine gauge has an indirect relationship with the puncture resistance.
Figure 6 shows the interaction effect of the machine gauge and core material on the puncture resistance properties. An indirect effect of the machine gauge on puncture resistance values can be observed. The reason may lie in the modulus and elongation properties of the constituent materials. As polyethylene has the highest modulus and largest elongation percentage values, the material may become stretched upon the application of puncture forces, hence absorbing the applied stresses without failure. In contrast, glass is a brittle material and has a lower modulus, and its elongation properties are destructed upon puncture forces and allows the needle to pass through. Another reason is that glass is smooth, and its glossy surface allows it to slip more easily, which allows for the penetration needle to go through the fabric structure [
14]. The highest level of puncture resistance values was obtained for UHMWPE-core materials, followed by steel- and glass-core materials in order. On the other hand, the fabric areal density increased by increasing the loop length, which allowed the needle to pass through, hence decreasing the puncture resistance values. Better puncture resistance properties will be obtained for a protective glove developed with a UHMWPE core at a lower fabric areal density. The regression equations developed for the puncture resistance for different cores are as follows:
4. Conclusions
In this study, seamless knitted gloves were developed with different materials and processing parameters to evaluate the effects of the sheath fiber linear density, no. of plies, core material type, and fabric GSM on the cut, tear, and puncture resistance properties. The results demonstrated that the effect of the sheath fiber denier was significant for the coupe cut and tear resistance properties. An increase in sheath fiber denier increases the coupe cut resistance values, while it decreases the tear resistance properties. The results demonstrated that the number of plies of core significantly affects the blade cut, coupe cut, and tear resistance properties as an indirect relation, while no effect was observed for the puncture resistance. Gloves made with single-ply yarns have better cut and tear protection compared to gloves made with two-ply yarns. The effect of the fabric areal density (GSM) was also found to be statistically significant on the blade cut, coupe cut, tear, and puncture resistance properties. An increase in fabric GSM increases the blade cut resistance, while it reduces the coupe cut, tear, and puncture resistance properties. The steel core can be appropriately used for blade cut resistance applications, a glass core is suitable for coupe cut resistance, while a UHMWPE core provides good results for tear and puncture resistance properties.