Thermal properties of aluminized and non-aluminized basalt fabrics

Abstract

The aim of this study was to characterize modified basalt fabrics as semi-finished articles for application in personal protective equipment (PPE), i.e. protective gloves. Resistance to the thermal properties for three fabrics made of basalt fibers differed in the aspect of mass per square meter and thickness as well as for the aluminized modifications presented. The modifications were obtained by gluing aluminum foil to the fabric with two kinds of glue. The results of the measurements are presented in the form of tables and figures. The study focused on the elaboration of the optimal textile modification designed for use in protective gloves against thermal and mechanical risks. According to the specifications of related European standards, only one way of proposed modification meets the requirements and can be successfully used for manufacturing the final product.

Keywords

basalt fiber aluminization thermal factor protective gloves

Perspectives of the application of basalt fibers related to their physicochemical properties arouse the interest of industry as well as research centers. Basalt fibers are called man-made mineral fibers (MMMF) and are produced by melting basalt aggregate derived from previously studied basalt deposits, in terms of chemical composition, at temperatures above 1400℃. The chemical content of basalt rock applied for manufacturing of the fiber include approximately: SiO₂ (52.8 %), Al₂O₃ (17.5 %), Fe₂O₃ (10.3 %), CaO (8.59 %), MgO (4.63 %), Na₂O (3.34 %), K₂O (1.46 %), TiO₂ (1.38 %), P₂O₅ (0.28 %), MnO (0.16 %) and Cr₂O₃ (0.06 %).

Basalt fibers show low moisture absorption, low thermal conductivity and low elongation at break with a limiting oxygen index (LOI) > 70 but high tensile strength and modulus, very good chemical resistance and more extended operating temperature range than regular E glass fibers, approaching that of carbon fiber and high-strength glass, but beating them price wise.^1–7 Because of their specific properties, they can be used as a substitute for special glass fiber threads for heat-resistant elastic structures for technical purposes. A comparison of properties of basalt fiber with other fibers used in high temperatures is given in Table 1.⁸

Table 1.

Comparison of physical and thermal properties of different fibers

Parameter	Type of fiber
Parameter	Basalt	Glass type E	Glass type S	Aramid	Carbon
Color	Dark green	White- transparent	White- blue (transparent)	Yellow, black or red	Black
Fiber diameter µm	7–22	5–20	5–20	10–15	6–9
Density g/cm³	2.65	2.60	2.49	1.44	1.80
Tensile strength (MPa)	4150–4800	3450	4830	3620	5100
Tensile modulus (GPa)	100–110	76	97	41.4	241
Tensile strain [%]	3.30	4.76	5.15	3.60–4.00	2.11
Work temperature (℃)	from −260 to +700	from −60 to +380	from −60 to +450	from −196 to +177	from −240 to +750
Short time work temperature (℃)	+750	+550	+600	+250	+1650
Temperature of melting (℃)	+1050 to +1460	+730 to +1000	+850 to +1000	+427 to +482	+3500
Thermo-insulation (W/m²K)	0.031–0.038	0.034–0.040	0.034–0.040	0.040	0.20

Incombustible properties allow basalt fabrics to resist fire for a significantly long time period in comparison with other fabrics. Moreover, basalt fabrics are characterized by their resistance to extremely high temperature. After exposure to high temperatures, they reveal flexibility and retain resistance to mechanical and chemical factors. They are also clean and nontoxic, which is their next useful advantage. Basalt fibers do not pollute the water and air; therefore, their storage and processing is safe. Taking into account the influence of basalt fibers on the human body, no negative effect has been recognized thus far. It should be pointed out that basalt does not cause a cancer risk in contrast to the asbestos responsible for malignant mesothelioma.⁹ Basalt fabrics are classified as safe for human health in agreement with US and EU standards.

Today, basalt fiber research, production and marketing efforts are based in European and North American countries. There are several companies using basalt as a main component for manufacturing numerous products. The Eastern Europe Composite group, including small and medium sized enterprises (SMEs) and companies from Great Britain, Poland, Russia and Ukraine, produces the basalt rovings combined with epoxy resin matrices designed for technical purposes, i.e. for transportation (boats, yachts), for protection (helmets) and for construction of bridges and buildings.^10,11 Other important companies involved in the production of basalt fibers are Kamenny Vek (Dubna, Russia), Technobasalt (Kiev, Ukraine), Basaltex, a division of Masureel Holding (Wevelgem, Belgium) and Sudaglass Fiber Technology Inc. (Houston, Texas).

Currently basalt fibers are commonly used in heavy industry as structural elements. This type of fiber has found wide application in construction, aviation, transportation and many other fields. Its properties make basalt fabrics appropriate for use as protective elements for individual parts of the human body, mostly arms and hands, e.g. gloves.

In this manuscript the results of laboratory tests for selected basalt fabrics are presented and discussed regarding their application in the construction of gloves that protect against thermal risks, in particular heat and fire. The thermal properties of basalt fabrics as well as aluminized variants were examined in accordance with the test methods used for assessing protective gloves classified as PPE. On the basis of the test results, the best variant of basalt fabric was indicated, taking into account not only the protective properties of the fabric and the final product but also other useful properties important for the glove end user. The appropriate mechanical properties of basalt fabrics have already been confirmed and published in previous studies.^12,13

Materials and methods

The basalt fabrics manufactured in the Czech Republic by Basaltex a.s. Company and their aluminized variants elaborated by a Polish manufacturer of protective heat-resistant textiles and clothing (Termoizol) were selected and tested for this study. All basalt fabrics used in the study were manufactured using the shuttleless rapier loom. To facilitate a description of results basalt fabrics and their aluminized modifications, they were designated in the way presented in Tables 2 and 3.

Table 2.

Technical parameters of basalt fabrics

Symbol of fabric	Linear density (tex)		Construction (per 10 cm)		Drape by Cusick’s method (%)	Weave
Symbol of fabric	warp	weft	warp	weft	Drape by Cusick’s method (%)	Weave
I	80 ± 3	40 ± 2	51 ± 1	86 ± 1	76.2 ± 3.2	plain
II	130 ± 5	120 ± 4	105 ± 1	140 ± 1	82.5 ± 2.6	twill (2/1)
III	300 ± 11	300 ± 9	59 ± 1	92 ± 1	88.2 ± 3.3	twill (2/1)

Table 3.

Symbols of basalt fabrics, their aluminized variants and the mean values of measured basic fabric parameters

Symbol of fabric	Fabric description with nominal values of mass per square meter	Mass per square meter (g/m²)	Thickness (mm)
I	Basalt fabric, 170 g/m²	172.1 ± 1.5	0.24 ± 0.01
II	Basalt fabric, 420 g/m²	417.0 ± 3.7	0.46 ± 0.01
III	Basalt fabric, 730 g/m²	730.0 ± 10.1	0.90 ± 0.08
1	Basalt fabric, 170 g/m² aluminized with Butacoll A+ glue	228.5 ± 6.4	0.37 ± 0.06
2	Basalt fabric, 420 g/m² aluminized with Butacoll A+ glue	484.0 ± 3.1	0.52 ± 0,01
3	Basalt fabric, 730 g/m² aluminized with Butacoll A+ glue	801.4 ± 4.6	0.80 ± 0,04
4	Basalt fabric, 170 g/m² aluminized with Bonatex PU85 glue	228.2 ± 8.3	0.29 ± 0.02
5	Basalt fabric, 420 g/m² aluminized with Bonatex PU85 glue	470.0 ± 0.7	0.61 ± 0,02
6	Basalt fabric, 730 g/m² aluminized with Bonatex PU85 glue	840.7 ± 4.4	1.07 ± 0,13

Non-aluminized basalt fabrics

Particular basalt fabric variants were differentiated by mass per square meter; their nominal values were as follows: 170, 420 and 730 g/m². Fabrics of higher mass per square meter were characterized by the twill weave, which ensures better fabric drape and flexibility, whereas the fabric of the lowest mass per square meter has a plain weave. The wave of fabrics characterized by low mass per square meter has no significant influence on flexibility after the aluminization process. The real values of mass per square meter for non-aluminized basalt fabrics were slightly different from those declared by the manufacturer (Table 3).

Aluminization technique

Two aluminization techniques were examined: glue 1, Butacoll A+,¹⁴ and glue 2, Bonatex PU85.¹⁵ The Butacoll A+ is a water-insoluble multicomponent glue based on epoxy resin containing acetone, toluene and 4-ter-butylphenol (dry matter content is 25%). Bonatex PU85 is a dispersion adhesive based on acrylic acid-ester polymers modified with dispersions of resins and other modifying agents that do not include any solvents. It is intended for self-adhesive manufacturing (dry matter content is 42%). The use of two glues applied for finishing of the basalt fabrics was related to an optimization of the aluminization techniques. The best combination of the fabrics covered by double-sided aluminized foil including durability, homogeneity as well as repeatability of the structures was achieved by adjusting the thickness of the glue layer, speed of rolling and temperature of drying. The main parameters of both aluminization techniques are presented in Figure 1.

Figure 1.

Parameters of aluminization techniques for selected glues.

Aluminized basalt fabrics

During the aluminization process the increase of mass per square meter value was observed (on average about 69 g/m²). The highest mass increase was observed for the basalt fabric designated by the symbol 6, i.e. from the value 730.0 g/m² before the aluminization to 840.7 g/m² after combining with the aluminum foil. The lowest increase of mass per square meter on the level 56.1 g/m² was for the fabric of symbol 4. With the exception of fabric 5, the increase of mass per square meter was proportional to its initial value.

Analyzing the thickness change after aluminization with the Bonatex PU85 glue, there were observed increases of about 0.05, 0.15 and 0.17 mm, successively, for fabrics of nominal mass per square meter: 170, 420 and 730 g/m². For the variants using the Butacoll A+ glue, the following thickness changes were noted: an increase of 0.13 mm for fabric 4 from the initial nominal mass per square meter 170 g/m², an increase of 0.06 mm for fabric 5 from the initial nominal mass per square meter 420 g/m² and a decrease of 0.10 mm from the initial nominal mass per square meter 730 mg/m² after the aluminization process.

The thickness of all aluminized fabrics produced and assessed within the study included values from 0.37 mm to 0.80 mm for the Butacoll A+ glue and from 0.29 mm up to 1.07 mm for Bonatex PU85. The thickness of the material is a crucial parameter characterizing the flexibility of the gloves and dexterity related to their use. Values of thickness for aluminized basalt textiles correspond to other aluminized textiles applied to the protective gloves. For example, the thickness of aluminized Nomex fabric characterized by the weight 302 g/m² is about 0.4 mm, whereas the thickness of aluminized Kevlar fabric at 346 g/m² is about 0.5 mm.¹⁶

Measurement methods

In the range of assessment of fabric resistance to thermal risks (heat and flame), the following tests were done: flammability, resistance to contact, convective and radiant heat, resistance to small splashes of molten metal, as well as heat resistance in terms of assessment of size changes after exposure to hot air at 180℃.

The basic standard that determines the requirements and test methods for gloves protecting against thermal risks including flammability, contact heat, convective heat, radiant heat, small splashes and large quantities of molten metal, is European standard (EN) 407:2004.¹⁷ The technical parameters of protective gloves classified as PPE are tested and assessed, taking into account their application and scope of activity for end users. That means that all testing methods relevant to the risks existing in workplaces where the gloves are used for hand protection shall be carried out for a complete assessment of the product. For the purpose of this study, it was stated that the gloves made of basalt fabrics will protect the users’ hands against flame, contact, convective and radiant heat as well as small splashes of molten metal. Additionally, the produced fabric variants underwent testing on heat resistance according to International Organization for Standardization (ISO) 17493:2000,¹⁸ which was not required by EN 407:2004. It is the requirement for gloves intended for firefighters according to EN 659:2003+A1:2008+AC:2009.¹⁹ It was decided that this test would be conducted to better characterize the examined fabric variants and to widen the field of glove application.

Flammability properties of all fabrics were measured by the edge-burning method according to EN ISO 15025:2002²⁰ related to protective clothing. The samples were exposed to a small flame coming from a gas blowpipe for 10 seconds, then the time of further burning and further glowing was determined as a highest value registered for samples cut in warp and weft directions. The performance level was assessed according to EN 407:2004 (Table 4).

Table 4.

Flame resistance performance levels according to EN 407:2004

Performance level	Time of further burning (s)	Time of further glowing (s)
1	≤20	Requirements are not defined
2	≤10	≤120
3	≤3	≤25
4	≤2	≤5

: seconds.

The contact heat resistance of basalt fabrics was assessed according to EN 702:1994.²¹ The time registered from the first contact with the heating cylinder to the moment when the temperature increased about 10℃ was determined. The test result for each fabric was carried out as the mean value of three measurements. Both 100℃ and 250℃ temperatures were chosen according to predicted usage of protective gloves. With regard to EN 407:2004, four performance levels are defined for contact heat resistance (Table 5).

Table 5.

Contact heat resistance performance levels according to EN 407:2004

Performance level	Contact temperature T_C (℃)	Threshold time t_t (s)
1	100	≥15
2	250	≥15
3	350	≥15
4	500	≥15

: seconds.

The resistance of the convection heat was measured according to EN 367:1992.²² The samples were placed horizontally above the gas blowpipe and underwent heat flux (of density 80 kW/m²) arising from the flame. The transmitted heat was measured using a copper (Cu) calorimeter in direct contact with the sample. The registered heat transmission index (HTI₂₄) is the time of colorimeter temperature increase of 24℃. The result for each fabric was calculated as a mean value of three specimens. The level of performance for the property is given in Table 6 according to EN 407:2004.

Table 6.

Performance levels related to convection heat resistance according to EN 407:2004

Performance level	Heat transmission index (HTI)₂₄ (s)
1	≥4
2	≥7
3	≥10
4	≥18

The radiation heat resistance was determined according to EN ISO 6942:2002.²³ Within the tests, the time of temperature increase of about 24℃ was registered after exposing the fabric sample to the heat radiation of the flux density equal to 20 kW/m². It is expressed as a radiation heat transmission index (RHTI₂₄). The performance levels for the radiation heat resistance are defined in EN 407:2004 and presented in Table 7.

Table 7.

Performance levels related to the radiation heat resistance according to EN 407:2004

Performance level	Radiation heat transmission index (RHTI₂₄) (s)
1	≥7
2	≥20
3	≥50
4	≥95

: seconds.

The resistance to small molten metal splashes was determined according to EN 348:1992,²⁴ taking into account requirements defined in EN 407:2004 (Table 8). The test relies on the reaction of molten metal droplets on the vertically placed fabric samples. As a result of measurement, the number of droplets acting on the sample was registered. The mean values from the samples cut in the warp and weft directions were calculated and then the lower value was taken into account as a final result.

Table 8.

Performance levels related to resistance to small molten metal splashes according to EN 407:2004

Performance level	Number of droplets
1	≥10
2	≥15
3	≥25
4	≥35

Additionally, heat resistance was determined according to EN 659:2003+A1:2008 and ISO 17493:2000. The test relies on examining the fabric samples and ready gloves at an air temperature of 180℃ for 5 minutes, and next checking the sample size and appearance changes after such an exposure. The requirement of heat resistance is written in the standard for the firefighters’ gloves, EN 659:2003+A1:2008. According to this standard, after the exposure in the above-described conditions the fabric should not be melted, dropped or burned, and the shrinkage of gloves should not be higher than 5%. The measurements were carried out for six specimens cut in the warp and weft direction, respectively.

Two mechanical properties of basalt fabric variants were assessed, i.e. abrasion resistance according to EN 388:2003²⁵ and fatigue bending resistance according to EN ISO 7854:1997.²⁶ Because the methodologies of those measurements are commonly known, a detailed description of the procedures is not included here.

Results and discussion

Thermal properties of non-aluminized and aluminized basalt fabrics

The results of thermal measurements of basalt fabric variants are presented in Table 9. The measurement procedures are described in the appropriate standards mentioned above.

Table 9.

Results of thermal properties of basalt fabrics

Fabric symbol	Flammability: time of further burning (s)/time of further glowing (s)	Contact heat resistance at 100℃ (s)	Contact heat resistance at 250℃ (s)	Convective heat resistance HTI₂₄ (s)	Radiant heat resistance RHTI₂₄ (s)
I	0/0 (4)	13 (0)	6 (0)	4 (1)	12 (1)
II	0/0 (4)	17 (1)	7 (0)	6 (1)	14 (1)
III	0/0 (4)	21 (1)	8 (0)	7 (2)	21 (2)
1	0/0 (4)	19 (1)	7 (0)	5 (1)	388 (4)
2	0/0 (4)	19 (1)	9 (0)	6 (1)	560 (4)
3	0/0 (4)	21 (1)	9 (0)	8 (2)	229 (4)
4	>30/—(0)	14 (0)	5 (0)	4 (1)	245 (4)
5	>30/—(0)	16 (1)	6 (0)	6 (1)	203 (4)
6	1/0 (4)	18 (1)	7 (0)	7 (2)	305 (4)

Values in parentheses describe the performance levels related to the protective properties of the fabrics; s: seconds.

Flammability assessment

The analysis of the flammability of particular basalt fabric variants confirms that only two fabrics did not fulfill the requirements in the range of this parameter, i.e. variant 4 – basalt fabric of nominal mass per square meter 170 g/m², aluminized with the use of Bonatex PU85 glue, and variant 5 – basalt fabric of mass per square meter 420 g/m², aluminized in the same way. In the rest of the aluminized and non-aluminized variants, the after-flame and after-glove time corresponded to the highest value, meaning the fourth performance level according to EN 407:2004.

Assessment of the resistance to contact and convective heat

Contact heat resistance was examined first for all the fabrics by measurement with a contact temperature equal to 250℃. Results showed that none of the fabricsachieved the required threshold time equal to 15 seconds. For this reason, further measurements were carried out at a contact temperature equal to 100℃. In this case only one variant of aluminized fabric designated by the symbol 4 did not fulfill the requirement.

The non-aluminized thin fabric I also did not fulfill the requirement. In both cases the expected time was shorter by about 1 second for fabric 4 and 2 seconds for fabric I. It should be emphasized that the application of Butacoll A+ glue for covering the fabric with the aluminum foil is responsible for achieving the first performance level regarding contact heat resistance. The first performance level in that case is not so high, but is enough to fulfill the basic requirement of the standard. Threshold times for fabrics, which were combined with the aluminum foil using the Bonatex PU85, is lower than for non-aluminized fabrics and indicate a negative influence of the glue on the protective properties in contact with the hot item.

Analysis of results concerning the convective heat resistance confirmed fulfilling the EN 407:2004 standard requirements in each case. For fabrics of symbols III, 3 and 6, i.e. variants of the highest mass per square meter equal to or higher than 730 g/m², the second performance level was obtained. For other variants the first performance level of the convective heat was confirmed.

On the basis of the results of measurement of resistance to convective heat, it can be concluded that the mass per square meter and covering the fabric with the aluminum foil layer influence this property. The higher the fabric mass per square meter, the higher the value of HTI₂₄ – the parameter characterizing the convective heat. The graphical form of the results concerning the resistance to the contact and convective heat is presented in Figure 2.

Figure 2.

Results of the resistance to the contact and convective heat for particular basalt fabric variants.

Assessment of the resistance to radiant heat

Concerning the resistance to radiation heat, all the examined basalt fabric variants fulfilled the requirements of the EN 407:2004 standard. Non-aluminized basalt fabrics achieved no more than the second performance level, whereas aluminized variants achieved the highest – the fourth performance level. Such a result was expected because the aluminization of the fabrics is recognized as one of the most effective modifications enhancing their ability to reflect heat.

The highest value of the heat transmission coefficient RHTI₂₄ equal to 560 seconds was registered for the variant designated by the symbol 2, i.e. basalt fabric (420 g/m²) combined with the aluminum foil with the Butacoll A+ glue. The heat transmission coefficient for the rest of the aluminized fabrics over-crossed the value of 200 seconds and is significantly higher than the value described in the standard, i.e. 95 seconds. The graphical representation of the results concerning the radiant heat resistance for the particular basalt fabric variants is shown in Figure 3.

Figure 3.

The set of result of the resistance to radiant heat for the basalt fabrics and their aluminized variants.

Assessment of the resistance to small splashes of molten metal and size change after exposure to hot air

Two successive parameters, i.e. the resistance to small splashes of molten metal and the size change after exposure to hot air were examined for all the basalt fabric variants. Both parameters were assessed, taking into account a possible application of basalt gloves by welders as well as other activities concerning the metallurgy industry. The results as well as confirmation of the fulfillment (or not) of the standard requirements are presented in Table 10.

Table 10.

The results of resistance to small splashes of molten metal and of heat resistance for the particular variants of basalt fabrics

Fabric symbol	Resistance to small splashes of molten metal (number of drops)	Size change after exposure to hot air (%) warp direction X/weft direction Y
I	3 (—)	—
II	5 (—)	—
III	5 (—)	—
1	34 (3)	−0.7/−0.7
2	>37 (4)	−0.2/0.0
3	>37 (4)	−0.2/0.0
4	30 (—)	−1.4/−0.2
5	23 (—)	−2.6/0
6	26 (—)	−2.6/−0.9

Values in parentheses describe the performance levels related to protective properties; dash means fabric variant does not fulfil requirement of the standard.

The resistance to small molten metal splashes in the case of non-aluminized fabrics did not fulfill the requirements of the EN 407:2004 standard. The number of drops for all the aluminized fabric variants seems to confirm the standard requirements. However, even with an acceptable number of drops allowed to pass the test in the case of fabrics of symbol 4, 5 and 6, the final test result for them is negative because of the changes that occurred in the tested samples. Therefore, these fabric variants cannot be used to ensure hand protection against small molten metal splashes.

The graphic form of the results including resistance to small molten metal splashes is shown in Figure 4.

Figure 4.

The results of the resistance to the small molten metal splashes for the basalt fabrics and their aluminized variants.

In the case of this parameter, as in the previous cases, a better performance level was obtained for the aluminized fabrics with the Butacoll A+ glue, i.e. the fabrics of symbols 1, 2 and 3. The changes in the fabric appearance after the treatment of the samples by small molten metal splashes are presented in Figures 5 –7.

Figure 5.

Effect of treatment by small molten metal splashes of non-aluminized basalt fabrics: A − 170 g/m², B − 420 g/m², C − 730 g/m².

Figure 6.

Effect of treatment by small molten metal splashes of basalt fabrics aluminized with Butacoll A+ glue: A − 170 g/m², B − 420 g/m², C − 730 g/m².

Figure 7.

Effect of treatment by small molten metal splashes of basalt fabrics aluminized with Bonatex PU85 glue: A − 170 g/m², B − 420 g/m², C − 730 g/m².

The measurement of the small molten metal splashes activity showed that for all non-aluminized basalt fabric variants aluminized with the use of the Bonatex PU85 glue, metal drops caused holes in the fabrics (Figures 5 and 7). A significantly better effect and higher performance level was obtained for the fabrics aluminized with the Butacoll A+ glue (Figure 6).

The heat resistance measurements were carried out only for aluminized fabrics, because in the case of non-aluminized fabrics the fabric thread displacement disabled the measurement. All the aluminized basalt fabrics fulfilled the EN 659:2003+A1:2008+AC:2009 standard requirements at an air temperature of 180℃. This standard concerns the gloves for firefighters. The size changes in the X and Y directions are presented in Figure 8.

Figure 8.

The results of assessment of fabric size changes after exposure to hot air for the aluminized basalt fabrics.

Mechanical properties of non-aluminized and aluminized basalt fabrics

Assessment of the abrasion resistance

From the point of abrasion, the best were two variants of aluminized fabrics of symbols 3 and 6 made of the same basalt fabric characterized by the highest mass per square meter (Figure 9). In both cases the second performance level was achieved. For the rest of the aluminized fabrics as well as for non-aluminized variant III, the first performance level was achieved. It should be pointed out that the raw basalt fabrics of symbols I and II do not fulfill the requirements of the standard in the range of abrasion. It confirms that in this case the aluminization modification of the fabrics improves the protective properties.

Figure 9.

Results of abrasion resistance for aluminized and non-aluminized basalt fabrics.

Assessment of the fatigue bending resistance

In the range of fabric strength properties of aluminized basalt fabrics, the fatigue bending resistance according to the EN ISO 7854:1997 standard was tested. This parameter was also applied for checking the bonding durability of aluminum foil with basalt fabric as an aluminization process quality assessment. The appearance of aluminized basalt fabrics after fatigue bending is presented in Figure 10.

Figure 10.

Aluminized fabrics after testing of the fatigue bending resistance. Symbols of fabrics correspond to the description in Table 3.

The results of fatigue bending resistance according to EN ISO 7854:1997 was assessed with the use of a four-grade scale describing the worsening of appearance (from 0 up to 3). All the examined aluminized basalt fabric variants showed changes of surface appearance due to the fatigue bending cycles. The registered failures included small wrinkles, cracks and fabric surface wrinkling. The observed worsening of appearance of measured fabric variants in comparison to nonbent fabric was equal to one in the case of each variant. Registered changes do not affect the protective properties of fabrics.

Summing up the experiments

According to the parameters defined in the standards concerning protective gloves designed for use in thermal risks, only basalt fabrics aluminized with Butacoll A+ glue fulfill all requirements, i.e. flammability, resistance to contact, convective and radiant heat as well as resistance to small splashes of molten metal and size change after exposure to hot air.

Flammability tests confirmed that only two variants of basalt fabrics did not fulfill the requirements, i.e. 170 and 420 g/m² aluminized with the use of Bonatex PU85 glue. In the case of other variants, the after-flame and after-glove times reached the highest performance level according to EN 407:2004.

Tests on the resistance to contact heat failed at a temperature of 250℃; therefore, 100℃ was used in the next step. The lower range of the contact heat confirmed that only the aluminized basalt fabric of symbol 4 and non-aluminized fabric of symbol I are not enough to meet the requirements.

The use of three different values of mass per square meter basalt fabrics within the study was related to the flexibility of the fabrics and their modified variants designed for final products. The higher mass per square meter can affect manual functionality and dexterity of the gloves. However, aluminized with Butacoll A+ glue, fabrics meet the requirements in terms of all tested parameters. The second performance level concerning convective heat resistance was observed for variants III, 3 and 6, characterized by the mass per square meter higher than 730 g/m². Lower values registered within the study for other variants are related to the first performance level for this parameter.

Taking into account the radiant heat resistance of the fabrics, the aluminization finishing was responsible for a significant increase in protective performance level, achieving the highest level for all aluminized variants.

Distinguishing between both aluminization techniques is important with relation to protecting fabrics against small molten metal splashes. A significant advantage again was revealed for Butacoll A+ glue. Because fabrics of symbols 4 and 5 did not pass the flammability tests, they cannot be applied for use in gloves protecting against small molten metal splashes designed for metallurgic purpose, e.g. welders.

The study of aluminized variants of basalt fabrics has shown that the use of the Bonatex PU85 glue gives insufficient results concerning heat resistance and resistance to thermal radiation. Additionally, these modifications reduce the resistance of the fabric in protecting against small molten metal splashes. Another disadvantage of this modification is the flammability of textiles.

Conclusions

Up till now basalt fabrics were not recognized as a material for PPE application; they were used mostly for technical purposes. Results of a number of preliminary tests carried out in the Central Institute for Labour Protection – National Research Institute on different types of basalt fabrics indicate that these types of fabrics can be used in protective glove construction. Taking into account the possible methods of glove manufacturing and intended use, the most appropriate seem to be basalt fabrics finished with aluminum foil, although they passed the contact heat test only at a contact temperature of 100℃. The aluminization technique with Butacoll A+ glue is suggested because the second technique with Bonatex gave insufficient results.

Concluding, it can be stated that:

The best protective and utility properties are fulfilled by the basalt fabrics aluminized with the use of Butacoll A+ glue.

Using the indicated basalt fabrics in protective gloves will be checked in the further part of the project. It is justified by the fact that in the protective glove design the aluminized basalt fabrics will be used in a multilayer structure with other components that, according to the experiments, will cause improvement of the protective properties, which were insufficient when the aluminized basalt fabrics are applied by themselves.

The performed experiments indicate that the application of aluminized basalt fabrics in PPE, e.g. protective gloves or clothing, can give promising results. Taking into account the economical aspect, the manufacturing cost reduction is feasible because of the lower price of basalt fibers compared with aramid or glass ones.

Footnotes

Funding

This research was partially supported by the Ministry of Science and Higher Education, Poland (project EUREKA No E! 4505).

Conflict of interest statement

None declared.

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