Processing Trends: Micro & Nano Fibers. B. Pourdeyhimi The Nonwovens Institute North Carolina State University

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1 Processing Trends: Micro & Nano Fibers B. Pourdeyhimi The Nonwovens Institute North Carolina State University 1

2 What s the Driver? Applications Filtration Aerosol Liquid Biopharma Medical Wound care Tissue engineering Properties High surface area Small pores High porosity??? High absorbency. 2

3 Why We Need Fine Fibers For Mechanical Filtration SVF=1.7%; 10 nm< d p <150 nm 3 B Maze, HV Tafreshi, Q Wang, & B Pourdeyhimi, J. Aerosol Sci., 38, 550 (2007)

4 Nonwoven Filtration Market Today Fastest growing Growing globally Highly fragmented Higher than average profitability Razor blade business model Development partnerships are common Technical sale Source: : INDA, EDANA estimates Nonwovens Growth by Applications (Annual Average Growth Rate) Filtration Automotive Other Industrials Wipes Construction Medical Hygiene Home Apparel 0% 2% 4% 6% 8% 10% Nonwoven Filtration Market ('000 tonnes) 744 Asia NAFTA Greater Europe (48%) F 4

75% of global energy use and 60% of demand for drinking water

5 Urbanization - TREND BY 2030, 60% OF WORLD WILL LIVE IN CITIES. FASTEST GROWING CITIES ARE FOUND IN ASIA Urban areas account for 75% of global energy use and 60% of demand for drinking water Source: McKinsey & Co. report "Preparing for China's urban billion" March

6 Health-Sapping Air Pollution - TREND WTO ESTIMATES OVER 2 MILLION PEOPLE DIE EVERY YEAR FROM INDOOR AND OUTDOOE AIR POLLUTION Source: World Health Organization,

7 Implications for Filtration and Beyond Increased pollution and global need for clean air and water driving the need to filter finer particles Filter media is driven to be more efficient, more durable, higher capacity, multifunctional, Eco-designing products 7

8 Game Changers in Air Filtration Micro glass Melt blowing MERV Mechanical Filtration Excellent DHC High Pressure Drop Electret MERV 7-18, Facemasks, Mechanical & Electrostatic Filtration Acceptable DHC Low Pressure Drop Mostly PP Electro spinning MERV Mechanical & Electrostatic Filtration Low DHC Low Pressure Drop Wider Range of Polymers 8

Let s Talk Surface Area Photo courtesy of Fiber Innovation Technology Specific Surface, m 2 /g 100 10 1 0.1 Diameter (Microns) 0.1 1 10 100 1000 Normal fibers have less than 0.

9 Let s Talk Surface Area Photo courtesy of Fiber Innovation Technology Specific Surface, m 2 /g Diameter (Microns) Normal fibers have less than 0.2 m 2 /g surface area Denier Per Filament A 100 nm fiber approaches ~ 20 m 2 /g surface area. Higher surface area is possible by manipulating the surface 9

Move Towards Nanofibers Some Facts Regular filament melt spinning cannot produce submicron fibers Meltblowing can produce submicron fibers with a somewhat broad fiber diameter distribution New

10 Move Towards Nanofibers Some Facts Regular filament melt spinning cannot produce submicron fibers Meltblowing can produce submicron fibers with a somewhat broad fiber diameter distribution New polymers are changing this landscape Solution electrospinning has been the leader in the formation of nanofiber nonwovens for critical applications for many years Others are emerging: Shear spinning Force spinning Melt fracture Solution blowing 10

11 Today s Systems Kato Tech ANSTCO MECC Elmarco Fiberio XanoShear Yflow Dienes Fuence 11

12 ElectroSpinning A New Old Technology Electrospinning Co-axial Electrospinning Emulsion Spinning Melt Electrospinning Sometimes it takes a LONG time to find the value of a new technology This technology was re-discovered only recently 12

13 Some History Zeleny (in 1911) is said to be the first to start the scientific investigation of the behavior of fluid jets under the influence of electrostatic field. His first publication appeared in Physical Review 3 (2): doi /physrev Prior to his work, patents on electrostatically dispersing fluids had been granted to Cooley (1902) and Morton (1902) USP ; USP ; USP

Some More History Between 1934 and 1944 a series of patents on electrospinning of fibers from polymer solutions to make yarns were granted to A. Formhals, Norton, and Childs.

14 Some More History Between 1934 and 1944 a series of patents on electrospinning of fibers from polymer solutions to make yarns were granted to A. Formhals, Norton, and Childs. The first industrial patent, using electrospinning to form webs was German Patent 689,870 (late 1960s or early 1970s). US 2,109,333, US (1938), US 2,187,306 (1940), US 2,323,025 (1943), US 2,349,950 (1944); USP ; ; USP (1944) USP , or German Patent 2,032,072; USP

15 The Beginnings Bayer, Freudenberg, Today s Systems 15

16 Electrospinning Nozzle based Nozzle-less Free liquid surface electrospinning of Polyvinyalcohol (Courtesy of David Lukas, Technical University of Liberec) Rotating drum is dipped into a bath of liquid polymer. Thin layer of polymer is carried on the drum surface and exposed to a high voltage electric field. When the voltage exceeds the critical value E c, a number of electrospinning jets are generated. 16

20 kv 30 120 kv Taylor cone separation Polymer concentration Fiber diameters Defined mechanically by needle distances Often 8-10% of solution 80, 100, 150, 200,

17 Differences Nozzle Nanospider Production Variables Nozzle Nozzle-Less Mechanism Hydrostatic pressure Needle forces polymer downwards. Drips are common in web Production variable required to be kept level across all needles in process Polymer is held in bath, uniform distribution None Voltage 5 20 kv kv Taylor cone separation Polymer concentration Fiber diameters Defined mechanically by needle distances Often 8-10% of solution 80, 100, 150, 200, 250 and higher. Standard deviation likely to vary over fiber length Self-adjusting Uniformity Good Exellent Often 10-20% solution 50, 100, 150, 200, 250 and higher. Standard deviation of ~20% 17

18 Can We Do Melt Electrospinning? Not Ready for Prime Time Yet Proper polymer development is crucial Poly(ester-amide): Spins without any further treatment Polymer is not chemically resistant; expensive and not commercially available Polypropylene Spins only as a blend with certain ionic additives High MFI (Meltblown grade) preferred Poor mechanical stability of the NF layer 18

19 Alternative Processes to Electrospinning?? Meltblowing Reducing throughput Smaller capillary size & compensating with higher hole density Higher air attenuation Lower viscosity polymers Spunbonding Smaller capillary size Higher air attenuation Fibrillation Bicomponent Islands-in-the-sea Splittables Other emerging technologies 19

20 Meltblowing: Finer Fibers Reducing throughput Smaller capillary size & compensating with higher hole density Higher air attenuation Lower viscosity polymers Melt Fracture 20

21 Die Type Smaller Capillaries + Higher Density L/D Hole density, HPI Orifice diameter, inch Space between capillaries, inch Control [C] Die [A] Die [B] Sample Coding Throughput Die type Basis weight e.g. Sample ( 0.2 A 20) Sample is produced at 0.2 GHM using die A at 20 GSM L Setback nosepiece d 60 o Air plate Mohammad Hassan, PhD, NC State, 2012 In collaboration with Hills, Inc. 21

Fiber Diameter Distribution Frequency 25 20 15 10 Mean 1482 nm SD 872 nm Min 495

5 Frequency 0 0 300 600 900 1200 1500 1800 2100 2400 2700 3000 50 40 Fiber

1800 2100 2400 2700 3000 Fiber Diameter, nm Frequency 18 16 14 12 10 8 6 4 2 Mean

22 Fiber Diameter Distribution Frequency Mean 1482 nm SD 872 nm Min 495 nm C A-2.5 Frequency Fiber Diameter, nm Mean 332 nm SD 253 nm Min 64 nm Fiber Diameter, nm Frequency Mean 499 nm SD 368 nm Min 10 nm Fiber Diameter, nm B-0.5 Mohammad Hassan, PhD, NC State,

Fiber Diameter Distribution Group 1 Group 2 Avg Fiber Diameter, nm 1800 1600 1400 1200 1000 800 600 400 200 0.012-A-2.5 Control Sample, L/D 30 Die A samples, L/D:50 Die B samples, L/D:200 0.00 0.05 0.

23 Fiber Diameter Distribution Group 1 Group 2 Avg Fiber Diameter, nm A-2.5 Control Sample, L/D 30 Die A samples, L/D:50 Die B samples, L/D: Avg Fiber Diameter, nm Control sample - Die [C] Group 2 samples - Die [B] Polymer Throughput, GHM Belt Speed, MPM Die A produces webs with smaller fiber diameters at higher throughputs than Die B Mohammad Hassan, PhD, NC State,

24 Nano Meltblowing: It is Possible Nanofibers are possible with small orifices and at extremely low throughputs. In our set up, mechanical efficiency of nanofiber MB webs exceeds those of glass media at a throughput of 6,800 g/m/hr that results in fibers as small as 0.2 microns. Normal meltblowing can yield as much as 70 to 100 kg/m/hr/beam and produce HEPA media if charged 24

25 So, Do I Really Need Nanofibers?? Not if You Have Stable Charge Source: Reicofil 25

26 Melt Fracture Gives New Life to Meltblowing And, meltblowing technology is not staying static. There are significant developments underway that are and will be resulting in major advances in the ability to produce large quantities of micro and nanofibers. Look for example at the developments enabled by systems that rely on polymer melt fracture to yield sub-micron fibers. 26

27 Melt Fracture Annular films fractured by air streams to form fine fibers. KCC patent Leonard Torobin, and Richard Findlow in US patent 6,183,670 Reneker et al. in US patent 6,382,

28 Melt Fracture Can readily produce fibers below 500 nm at normal meltblowing throughputs The process will lead to cost-effective filtration media for many applications This will likely lead to fewer developments in melt electrospinning 28

29 The Solution Blowing Process UIC and NWI Fibers are formed from solution similar to electrospinning This process normally yields fibers below 1 micron and is similar to electrospinning but at higher throughputs Process can be controlled to deliver same product reproducible 29

30 The Solution Blowing Process PAN fibers issued from nozzle In this set up, the core nozzle is surrounded by a concentric annular nozzle. Polymer solution from the reservoir is issued through the core nozzle into the surrounding high speed nitrogen jet flow from the annular nozzle, which delivers gas from a high pressure cylinder at a pressure of bar. The nitrogen jet accelerates, stretches and bends the core jet of polymer solution. 30

31 Diameter distribution: monolithic nanofibers SEM image of solution blown PAN fiber mat obtained from single jet showing existence of roping 31

32 Composite Nanofibers 50 nm Mg x Zn 1-x O nanofibers Dark field TEM image of TiO 2 /CdSe NFs Formation of fibers from solutions is an enabler Other systems cannot easily achieve the same results Unpublished work 32

The Spunbond Process The Highest Throughput The only method for the production of continuous filaments - small and strong filaments This process normally yields fibers larger than 1 denier or fibers

33 The Spunbond Process The Highest Throughput The only method for the production of continuous filaments - small and strong filaments This process normally yields fibers larger than 1 denier or fibers greater than 15 microns, or so Hardly nano Processes for producing small fibers rely on fibrillation of homocomponents, or splitting or fibrillation of bicomponent or multicomponent fibers/filaments 33

The Nanoval Process Fibrillating Homocomponent

fibrillation of homocomponent filaments leading to

$fracturing of polymer streams is not new either$

34 The Nanoval Process Fibrillating Homocomponent Filaments The process is said to cause fibrillation of homocomponent filaments leading to split/fibrillated fiber diameters in the range of 1 to 5 microns at normal throughputs Melt fracturing of polymer streams is not new either 34

The Evolon Process Splitting Segmented Pie Fibers

and consolidate the microfilaments, creating a

Equivalent Diameter ( m) 15 Segmented Pie 11 8 5

35 The Evolon Process Splitting Segmented Pie Fibers The water jets simultaneously tightly entangle and consolidate the microfilaments, creating a fabric: Evolon. Equivalent Diameter ( m) 15 Segmented Pie Segments 35

The NWI Process Fibrillating Bicomponent Fibers The islands in the

water jets to simultaneously fibrillate and entangle and

22 0.15 7 37 Number of Islands 50/50 Sea-Island Ratio 240 600 1200

36 The NWI Process Fibrillating Bicomponent Fibers The islands in the sea or multilobal fibers are sheared and subjected to high pressure water jets to simultaneously fibrillate and entangle and consolidate the microfilaments. Diamter ( m) Number of Islands 50/50 Sea-Island Ratio US Patent 7,883,772 US Patent 7,981,336 US Patent 7,981,226 US Patent 7,438,777 36

What are the limits of Shaped Fibers? Diameter (Microns) Specific Surface, m 2 /g 0.1 1 10 100 1000 100 10 1 4DG Round 0.1 0.

37 What are the limits of Shaped Fibers? Diameter (Microns) Specific Surface, m 2 /g DG Round Denier Per Filament Photo courtesy of Fiber Innovation Technology Smallest 4DG ~ 6 dpf 37

38 The NWI Process Super Surface Area Fibers Diameter (Microns) Specific Surface, m 2 /g DG Round Denier Per Filament Winged Photos courtesy of Allasso Industries. Inc. US Patent 8,129,019 B2, March 6, 2012 US Patent 8,410,006 B2, April 2,

39 The Process for Winged Fiber Spunbond filaments are entangled by water jet and then subjected to further treatment to release the wings Up to 300kg/m/hr per beam Untreated Winged Media NaOH bath Water bath Neutralization bath Drum dryer Treated Winged Media 39

40 Spunbond Process for Nanofibers? Spunbond can yield webs with the highest degree of strength and consolidation Sub-micron fibers in spunbond are possible; the web is consolidated however. It is possible to create high surface area shaped fibers 40

41 And the Final Message? The solution is often NOT a single material. Composites offer the ability to accomplish what we need at lower weight and more cost effectively. For example, the Winged media together with meltblown webs or electrospun webs will yield a great composite 41

42 Final Word A single technology cannot and will not deliver all the structural features required in the final system. Fortunately, there is a great portfolio of processes that can be used for creating new fibers and structures NWI is investing in a wide portfolio to enable optimal product development 42

43 And Which One Do I Choose? Sub-type Meltblown Spunbond E-Spinning S-Blowing Description Throughput (Kg/m/hr) Fine fiber meltblown process through process control and melt fracture Fiber size (nm) 500 2,500 = +/- 20% Production ready? Two polymer are extruded through larger holes, then separated afterwards, often hydro-entangled Electrostatic field is used to form fibers but is formed without needles using higher voltage on rollerelectrodes Less than ,500 = +/- 10% = +/- 30% Yes Yes Yes No Fine fiber blown process from solution through process control 100 2,500 = +/- 30% 43

(a) Schematic of the electrically-assisted

44 And, Fibers Below 50 nm?? UIC & NWI Disruptive Tech. Patent Pending Supersonic electrically-assisted blowing and resulting nanofibers. (a) Schematic of the electrically-assisted solution blowing setup. (b) Two-stage stretching of polymer jet and crystal sheet alignment and packing. 44

45 Future of Our Industry is Bright Trends that drive the growth of filtration business Population growth, urbanization, increase in prosperity, scarcity of natural resources, health awareness and sustainability China, India and developing nations are the fastest growing markets for the filtration industry New technologies, new products are needed to meet market needs Filtration media of the future? 45

unscathed to the 21st century unable to deal with disruptive technologies Source:

46 Disrupt or Become Disrupted INNOVATIONS IN TECHNOLOGY CONTINUE TO HAVE MASSIVE EFFECTS ON BUSINESS AND SOCIETY 66% of top s companies failed to survive unscathed to the 21st century unable to deal with disruptive technologies Source: 46

47 Thank You! Alex Yarin UIC Hooman Tafreshi VCU Benoit Maze NWI Eunkyoung Shim NWI Saad Khan, NC State Stanislav Petrik Liberec And, many fine students Work, in part, sponsored by the Nonwovens Institute 47

Electrospun Nanofibers as Separators in Li-ion in Batteries. Dr. Cagri Tekmen Elmarco Ltd., Sekido, Tama, Sekido Bld 4F, Tokyo , Japan

Electrospun Nanofibers as Separators in Li-ion in Batteries Dr. Cagri Tekmen Elmarco Ltd., 3-4-1 Sekido, Tama, Sekido Bld 4F, Tokyo 206-0011, Japan 1. Introduction One-dimensional (1D) nanostructures -having