Optimization of centrifugally spun thermoplastic polyurethane nanofibers for air filtration applications

Figures & data

Figure 1. The schematic of the Nanocentrino L1.0 system.

Table 1. Design of experiment.

No. of Experiment	Orifice (Needles)	Rpm	Concentration (%)
1	16G	4000	10
2	16G	8000	15
3	16G	12000	20
4	18G	4000	15
5	18G	8000	20
6	18G	12,000	10
7	22G	4000	20
8	22G	8000	10
9	22G	12,000	15

16 gauge (G) needle has 1.2 mm inner diameter, while 18G and 22G have 0.8 and 0.4 mm, respectively.

Figure 2. SEM images and diameter distribution of the samples produced with 16G needles. (a) sample 1 (4000 rpm and 10 wt%), (b) sample 2 (8000 rpm and 15 wt%), and (c) sample 3 (12,000 rpm and 20 wt%).

Figure 3. SEM images and diameter distribution of the samples produced with 18G needles. (a) sample 4 (4000 rpm and 15 wt%), (b) sample 5 (8000 rpm and 20 wt%), and (c) sample 6 (12,000 rpm and 10 wt%).

Figure 4. SEM images and diameter distribution of the samples produced with 22G needles. (a) sample 7 (4000 rpm and 20 wt%), (b) sample 8 (8000 rpm and 10 wt %), and (c) sample 9 (12,000 rpm and 15 wt%).

Table 2. S/N ratios of design factors: smaller is better.

	Orifice	Rpm	Concentration
Level 1	−55.17	−52.57	−50.74
Level 2	−53.69	−54.46	−53.18
Level 3	−52.71	−54.55	−57.65
Delta	2.46	1.98	6.91
Rank	2	3	1

Figure 5. Average fiber diameters corresponding to the experiments. The boundaries in box plot represent the upper (75th %) and lower (25th %) quartiles. The line represents the median and the plus sign also represents the mean value of fiber diameters.

Figure 6. S/N ratio graphs for each design factors with levels.

Table 3. Analysis of variance for means.

Source	DF	SS	MS	F	Percentage contribution (%)	p-value^*
Orifice	2	47678	23839	36.43	12.41	0.027
Rpm	2	37409	18704	28.59	9.73	0.034
Concentration	2	297891	148945	227.63	77.52	0.004
Error	2	1309	654		0.34
Total	8	384286			100

* (<0.05) significant.

Figure 7. Effect of different C-spin parameters on the average fiber diameters. (a) Orifice diameter and rotational speed, (b) orifice diameter and solution concentration, and (c) rotational speed and solution concentration. The 3rd process parameters which do not appear in graphs have also an effect on diameters.

Figure 8. SEM images and fiber diameter distributions of the optimum condition (22G, 4000 rpm, 10 wt%), respectively.

Figure 9. Average fiber diameters corresponding to all the 9 experiments, sample 8, and the experiment at the optimum condition, respectively. The boundaries in box plot represent the upper (75th%) and lower (25th%) quartiles. The line and plus sign represents median and represent the mean value of fiber diameters, respectively.

Figure 10. Percentage of penetration versus resistance curves of fibrous samples challenged with 0.3 µm Emery 3004 particles.

Figure 11. Quality factor values of different triple layer samples challenged with Emery 3004 aerosols. The Knudsen number for PP spunbond without NF is 0.007, while No 3 is 0.140, No 8 is 0.416, and Opt. Cond. is 0.644.