Contents
Functional Hydrophobicity

DWR and Textile Water Repellency Testing: Measure Each Durable Water Repellent Finish on Fabric With Contact Angle and Roll Off Alongside the AATCC Repellency Test Method

A spray rating tells you a fabric passed; it does not tell you by how much, or why it failed after washing. Measure water contact angle and roll off on the fabric surface, fresh and after laundering and abrasion, to rank DWR finishes and catch weak batches before the spray test.

Who this is for: Textile finishers, DWR chemists, outdoor apparel and technical textile teams, and labs qualifying water repellent fabrics, including protective and military textiles.

Where it fits: Finish development, durability testing after washing and abrasion, and batch checks between AATCC or ISO spray tests.

What it does not do: It does not give an official spray rating, hydrostatic head, breathability or oil grade.

Method
Sessile drop contact angle and tilt stage sliding angle on fabric, with a fabric holder
Standard
Complements AATCC TM22 and AATCC TM193; partially compliant with ISO 19403-7, up to 60° tilt
Setup
About 2 minutes
Book a 15 minute demo Request a quote
Detail of fabric water repellent
Abhimanyu Photo
Written by
Abhimanyu Bhandankar
Holds an MBA from Schulich School of Business and a BE in IT. He joined Droplet Lab in July 2019 and now leads sales and marketing.
CEO at Droplet Lab
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Droplet-Lab logo
Technical Review by
Droplet Lab Team
Droplet Lab builds precision instruments and software for surface science measurement, specialising in contact angle analysis and surface tension characterisation. Used by researchers across materials science, pharmaceuticals, coatings, and advanced manufacturing, Droplet Lab's Dropometer has contributed to studies published in peer-reviewed journals including Advanced Functional Materials (Impact Factor 19). The team combines instrument engineering with deep domain knowledge in wettability science with a focus on practical accuracy.
Read More
Abhimanyu Photo
Written By

Abhimanyu Bhandankar

CEO at Droplet Lab

Holds an MBA from Schulich School of Business and a BE in IT. He joined Droplet Lab in July 2019 and now leads sales and marketing.

Droplet-Lab logo
Reviewed By

Droplet Lab Team

Droplet Lab builds precision instruments and software for surface science measurement, specialising in contact angle analysis and surface tension characterisation. Used by researchers across materials science, pharmaceuticals, coatings, and advanced manufacturing, Droplet Lab's Dropometer has contributed to studies published in peer-reviewed journals including Advanced Functional Materials (Impact Factor 19). The team combines instrument engineering with deep domain knowledge in wettability science with a focus on practical accuracy.

Featured Studies & Publications

Research Paper Contact angle measurement with a smartphone
Research Paper Surface tension measurement with a smartphone using a pendant drop
Why it matters

Why DWR testing needs more than a pass or fail

Above 120°

water contact angles on DWR fabrics after 10 washes, while the same fabric got grade 0 in the spray test; static contact angle alone can mislead.

Kowalski et al., Materials 15(11):3825, 2022

Above 95

spray rating given to every fabric in one study by the standard AATCC TM22 spray test, so the test could not tell similarly graded fabrics apart.

Hill et al., AATCC Journal of Research 7(6), 2020

10 October 2026

date from which the EU PFHxA restriction applies to clothing textiles for the general public, at 25 ppb for PFHxA and its salts.

Commission Regulation (EU) 2024/2462

Sources: Kowalski M. et al., Quality and quantity assessment of the water repellent properties of functional clothing materials after washing, Materials, 2022; Hill P.J. et al., Quantifying water repellency by modifying spray test method AATCC TM22, AATCC Journal of Research, 2020; Commission Regulation (EU) 2024/2462 of 19 September 2024. Figures come from these sources, not from Droplet Lab measurements.

Quick reference

What this fabric repellency check does and what it does not

A quick reference for textile and DWR teams checking fit before reading further.

Evidence Box

Problem this solves

DWR finishes that pass the spray test fresh but lose water repellency after washing, abrasion or a switch to fluorine free chemistry.

Standards

Complements AATCC TM22 spray testing and AATCC TM193 aqueous liquid repellency; supports AATCC TM79 drop absorbency timing; partially compliant with ISO 19403-7 roll off, up to 60° tilt.

Peer reviewed method

The Dropometer drop shape method was validated against a KRUSS DSA100E in two peer reviewed papers, in Review of Scientific Instruments and Colloids and Surfaces A.

Customer case study

An Iowa State University coatings group added a Dropometer with an automatic dropper, tilt stage and fabric holder to measure contact angle and roll off on coated fabrics with water and oils.

Published research

A University of Calgary polymer group measured electrospun polystyrene fibre mats as highly hydrophobic and explained them with the Cassie Baxter model (Macromolecular Rapid Communications, 2024).

Honest limit

Contact angle on fabric depends on weave and roughness. Use it to compare like fabrics, not to replace the spray rating.

Who this is for

What water repellency question are you trying to answer?

Pick the card closest to your role. Each one points to the part of this page that answers it.

DWR chemist

You are moving from C8 and C6 fluorocarbon finishes to fluorine free DWR. Contact angle and roll off on treated fabric rank each repellent finish in minutes, and show which ones keep their water repellency after washing.

Fluorine free finishes often match on water but lose oil repellency; test both if your end use needs it.

Textile finishing QA

You run a water repellent finish on a stenter line and release fabric by spray rating. A contact angle check on each roll catches weak add on or cure before the full spray test.

Condition fabric before testing; humidity and residual detergent change readings.

Protective and military textile buyer

You qualify coated fabrics where repellency must survive abrasion and laundering. Contact angle and roll off before and after Martindale abrasion give numbers to compare suppliers.

Use your procurement specification's tests for acceptance; contact angle supports them.
Fit check

Is this the right test for your DWR program?

It measures how water droplets meet the fabric surface. It does not replace standard spray or hydrostatic tests.

Good fit if

You compare DWR finishes or add on levels on the same fabric.
You track durability of water repellency after washing and abrasion.
You need roll off as well as contact angle.
You test water and oil repellency with several liquids.
You want a quick check between AATCC spray tests.

Less relevant if

You need an official spray rating from a spray tester for a customer specification.
You need hydrostatic head or water penetration under pressure.
You need breathability or moisture vapour transmission.
You need to prove a finish contains no PFAS; that needs chemical analysis.
Summary

How to test DWR water repellency on fabric

The answer in under a minute.

To evaluate the water repellency of a finish, condition the fabric, place water drops on the fabric surface with a holder that keeps it flat, and measure contact angle and roll off angle. Repeat after set washing and abrasion cycles. Rank DWR finishes on both numbers and their decline, then confirm the best with the AATCC spray test your customers specify.

The Dropometer contact angle kit with its tilt stage runs both checks; our contact angle measurement guide and sliding angle measurement guide explain the methods. It complements AATCC TM22 spray testing. A Canadian federal research team used it on water repellent polyester fabric, and a University of Calgary group published electrospun polystyrene fibre results measured with it. Our fabrics guide covers the wider context.

Expert Quote

Expert perspective on repellency and roll off

Repellency and mobility are not the same thing: a high contact angle says a drop is repelled, but whether it rolls off is a separate question; the two can even be mutually exclusive.

Dr. Alidad Amirfazli

Professor, Department of Mechanical Engineering, York University; Co-founder, Scientific Advisor, Droplet Lab

The problem

Why DWR finishes fail and why spray ratings miss it

A durable water repellent (DWR) finish makes water droplets bead up and roll off the fabric surface instead of soaking into the fibre and yarn. It is what keeps outdoor apparel, workwear, protective textiles and technical fabrics from wetting out, and it protects the breathability of a waterproof membrane underneath. For decades the best DWR finishes were long chain C8 fluorocarbons, linked to PFOA and PFOS, and then C6 fluorocarbon chemistry. Regulation is ending that: the EU PFHxA restriction applies to clothing textiles for the general public from 10 October 2026, and New York and California restrict intentionally added PFAS in apparel. Fluorine free finishes have higher surface energy, so they can match fluorocarbons on water but are weaker against oils and low surface tension liquids. Most teams still judge water repellency with the AATCC TM22 or ISO 4920 spray test, a visual rating against a chart. It is the right acceptance test, but it gives a pass or fail band, it can rate very different fabrics the same, and it does not show why repellency drops after washing or abrasion. Contact angle alone is not the answer either: one study found angles above 120° on fabrics that had already failed the spray test. Teams need contact angle and roll off measured together, fresh and after durability steps, next to the spray test.

Fabric passes the spray test fresh but wets out after a few washes.
Water droplets sit on the fabric but do not bead up and roll off.
A fluorine free finish repels water but not oily stains.
Rolls from the same finish run give different spray ratings.
Repellency drops at seams and high wear areas after abrasion.
Troubleshooting

Why water repellency drops and what to check

Why:

  • Too little repellent finish, or a cure below the recommended temperature, leaves parts of the fibre uncovered.

How to detect:

  • Lower contact angle and higher sliding angle than the reference roll.

Corrective action:

  • Check pad pick up, bath concentration, stenter temperature and dwell time, then retest.

Why:

  • Detergent left after washing lowers the surface tension of water on the fabric and wets it.

How to detect:

  • Readings fall after washing and partly recover after thorough rinsing or heat.

Corrective action:

  • Rinse well, tumble dry or heat activate as the finish requires, and retest.

Why:

  • Rubbing removes or flattens the finish on the yarn surface.

How to detect:

  • Readings fall after Martindale or other abrasion cycles, most at high wear areas.

Corrective action:

  • Review binder or crosslinker and finish durability; compare decline curves.

Why:

Non fluorinated finishes often match water repellency but give little oil repellency. Our page on PFAS free reformulation covers the switch.

How to detect:

  • Good water contact angle, but oils or water and alcohol mixtures wet the fabric.

Corrective action:

  • Decide which liquids the end use must repel, and test those liquids.

Why:

Weave, yarn and fibre texture change the apparent contact angle through Cassie Baxter wetting. Our lotus effect glossary entry and experiment on superhydrophobic glass explain why.

How to detect:

  • The same finish reads differently on woven fabrics and knits, or on polyester and cotton fabric.

Corrective action:

  • Compare finishes on the same fabric, and keep a reference roll for each construction.

Why:

Drop volume, fabric tension and lighting change readings on soft, low contrast fabric. Our guide to reproducible contact angle measurement covers fair comparisons.

How to detect:

  • The reference fabric reads differently between days or operators.

Corrective action:

  • Use a fabric holder, fixed drop volume and lighting, and measure the reference every session.

Not sure why your DWR finish is failing?

Send a fresh and a washed fabric sample, and we will compare them on a call.

Book a 15 minute demo
Quality records

What a fabric repellency record contains

Each check produces a record you can file with the roll or finish trial. These records can sit beside your spray rating, hydrostatic and washing results in your existing quality records.

Fabric identity

Fibre, construction, dye, water-repellent finish, add on, cure and roll number.

History

Fresh, or the number of washes, detergent and drying, or abrasion cycles.

Method settings

Liquids, drop volume, tilt rate, holder and drops per sample.

Readings

Contact angle and sliding angle, median and spread.

Decision

Release, retest or hold, linked to the spray rating.

Drop images

Automatic edge and baseline detection gives the same reading from the same image, so a reviewer can recheck any result.

Measurements

What to measure for repellent finish performance and durability

Repellency

Water contact angle on the fabric

Why it matters: It shows how strongly the finish repels water droplets.

How to interpret: Compare with a reference roll of the same fabric; thresholds are set per fabric from your own correlation with spray ratings.

When it is not enough: Roughness inflates angles on textured fabric.

Roll off

Sliding angle on a tilt stage

Why it matters: It shows whether water beads up and rolls off, which is what keeps fabric dry.

How to interpret: Lower is better; drops that do not slide by 60° are recorded as 60° or more.

When it is not enough: Fabric must be held flat and tensioned.

Liquids

Contact angle with oils or water and alcohol mixtures

Why it matters: It shows wettability by oils and stains, where fluorine free finishes differ most.

How to interpret: Use the liquids your end use or AATCC TM118 and TM193 grading relate to.

When it is not enough: It does not give the official grade.

Durability

All of the above after washing and abrasion

Why it matters: Durability of water repellency is where finishes separate.

How to interpret: Compare decline curves, not single points.

When it is not enough: Lab cycles do not match field wear exactly.

Validation

Validated measurement approach for fabric repellency

How the Dropometer itself has been validated, and where textile researchers have used it.

Peer reviewed method

The Dropometer drop shape method is published in Review of Scientific Instruments and Colloids and Surfaces A. Contact angle was validated against a KRUSS DSA100E, with a published accuracy of 0.35°.

See the validation papers

Customer evidence on coated fabric

Dr. Shan Jiang's group in Materials Science and Engineering at Iowa State University added a Dropometer with an automatic dropper, a tilting stage and a fabric holder in 2025, to measure contact angle and roll off on coated fabric samples with water and oils. The group published its rechargeable antimicrobial coatings work in ACS Applied Materials and Interfaces in 2026.

Read the case study
QC Protocol

How to test DWR fabric with contact angle and roll off

Six steps for one fabric and one finish. Repeat for each new construction or chemistry.

1

Condition the fabric

Condition samples at standard temperature and humidity, and mark the face side.

2

Lock the method

Fix liquids, drop volume, fabric holder and tension that keep the surface of the fabric flat, tilt rate and drops per sample.

4

Set gates from spray ratings

Correlate contact angle and sliding angle with spray ratings on the same rolls, fresh and after washing.

5

Check each roll or trial

Measure the same way, then repeat after your set washing and abrasion cycles.

We completed our gage R&R study on the unit and it performed very well.

Brandon Barbee

Corporate Quality Engineer, Zeus Industries, Polymer Manufacturing

Download the textile DWR repellency SOP

A two page SOP you can adapt for your fabrics, with the method lock, conditioning, wash and abrasion steps, gates against a reference roll, a troubleshooting table and a record sheet.

Sliding angle measurement with the Dropometer

Sliding angle measurement with the Dropometer

Example output

Example DWR finish screen through washing

Example data only. Your values and gates will differ and must come from your own reference rolls and spray ratings.

How to read this screen

Example gates against the reference: contact angle within 5° and sliding angle no more than 10° higher. The fluorine free finish matches fresh but loses more after 20 washes. The low add on trial fails before washing, so it never needs a spray test. The unfinished fabric shows the baseline.

Example DWR finish screen

Finish Wash cycles Water contact angle (°) Water sliding angle (°) Result
Reference C6 fluorocarbon finish 0 142 12 Reference
Reference C6 fluorocarbon finish 20 136 20 Reference
Fluorine free DWR 0 141 14 Pass
Fluorine free DWR 20 128 34 Reformulate for durability
Fluorine free DWR, low add on 0 124 40 Hold
Unfinished fabric 0 Wets Wets Information

Example data, not customer data. Polyester woven fabric, conditioned 24 h at 65 %RH and 20 °C; 10 µL water drops on a fabric holder; washes at 40 °C with tumble drying.

Signal order

The order to check signals when repellency drops

Check these in order. Each one rules out a cause before you look at the next.

1

Conditioning and rinse

Rules out humidity and detergent residue.

2

Contact angle

Shows whether the finish is there and repels water.

4

Readings after washing and abrasion

Shows durability of water repellency.

5

Spray rating

Confirms performance with the AATCC or ISO test your customer specifies.

FAQ

Common questions about DWR and textile water repellency

Questions DWR chemists and textile QA teams ask about repellency testing.

They measure different things. AATCC TM22 rates the wetted pattern after spraying against a chart. Contact angle measures single water droplets. Kowalski and colleagues found angles above 120° on washed fabrics that scored grade 0 in the spray test, so use contact angle with roll off, and keep the spray test for acceptance.

Water repellency on a garment depends on water rolling off, not just beading. A drop can sit at a high angle and still pin to the fibres. Schellenberger and colleagues combined standard methods with a roll off angle setup to compare fluorinated and fluorine free finishes. Sliding angle shows that difference with a number.

On water, often yes. Hill and colleagues found non fluorinated finishes gave water repellency similar to C8 and C6 finishes but were clearly inferior for oil repellency. Schellenberger and colleagues found the best non fluorinated alternatives equal to short chain fluorinated polymers on water, but weaker against low surface tension liquids.

Measure the initial water repellency, then durability after washing and abrasion resistance, for example after Martindale cycles. Kowalski and colleagues found water repellency fell below an acceptable spray grade after the fifth wash for all materials tested, and the PFC free finish was the least resistant to washing. Compare the decrease in water repellency as curves, not single points.

AATCC TM22 applies to any textile fabric, finished or not, and ISO 4920 is its ISO counterpart for spray testing; ISO 4920 notes it does not predict rain penetration. AATCC TM118 covers oil repellency, AATCC TM193 water and alcohol repellency, AATCC TM127 hydrostatic pressure and AATCC TM35 rain penetration. The Dropometer complements TM22 and TM193 and does not replace them.

The EU PFHxA restriction applies to clothing textiles for the general public from 10 October 2026, with other consumer textiles following in 2027. New York bans intentionally added PFAS in apparel from 2025, with severe wet conditions outdoor apparel from 2028, and California has a similar law. Check current rules for your market; we do not give regulatory advice.

No. Water repellency is about each water droplet beading and rolling off the surface. Waterproof fabrics have high water resistance under pressure, measured by hydrostatic head (AATCC TM127) or a rain test (AATCC TM35), usually thanks to a membrane or coating. A DWR finish keeps the outer face dry so a breathable membrane can keep working.

A contact angle instrument with a fabric holder to keep samples flat, a tilt stage for roll off, and image analysis that copes with low contrast fabric. The Dropometer has a fabric stage and a snap in tilt stage up to 60°. Our page on ski wax hydrophobicity covers roll off on another sports surface.

Business impact

What changes when you measure fabric repellency with numbers

Typical changes in how teams work. Benchmarks are given only where a published source exists.

Before and with fabric contact angle checks

Metric Before Dropometer With Dropometer Indicative Benchmark
Finish ranking Spray rating bands Contact angle and sliding angle as numbers Standard spray test rated every fabric above 95 (Hill et al., 2020)
Durability tracking Spray rating after washing Decline curves after washing and abrasion All materials fell below grade 3 after 5 washes (Kowalski et al., 2022)
Batch checks Full spray test on every roll Quick check on each roll, spray test on borderline rolls No published benchmark; track on your own rolls
Fluorine free transition Fluorocarbon reference Candidates ranked on water and oil EU PFHxA limits for clothing from 10 October 2026

See the test on your own fabric

Send a fresh and a washed sample of your fabric. We will show the comparison on a call.

Book a 15 minute demo

Estimate saved finish development work

Enter your own numbers. The result is an estimate, not a Droplet Lab claim.

DWR finish development estimate

Estimate saved finish development and spray test work.

Each Dropometer unit is US$5,000; the default models one unit.
Chemistry, fabric, washing and spray test cost for one finish trial.
Finishing, conditioning, contact angle and roll off checks, and analysis.
No published benchmark. Use your own estimate and start low if unsure.

Result

~0
Trials saved per month
~0
Monthly savings
~0
Payback period
~0
First year net benefit

Monthly savings = materials saved + technician time saved from reduced iterations.

Limits

What contact angle cannot tell you about fabric

Honest limits, so you know when to reach for another test.

It does not give an official AATCC or ISO spray rating.
It does not measure hydrostatic head or water penetration under pressure.
Roughness and weave inflate contact angles; compare like fabrics.
Fabric must be held flat; loose fabric gives unreliable baselines.
The tilt stage reaches 60°; drops that do not slide are recorded as 60° or more.
It does not detect PFAS in a finish.

Contact angle and sliding angle show how water droplets meet the fabric surface. Spray rating, hydrostatic head, rain tests, breathability, oil grades and PFAS content need their own tests.

Book a 15 minute demo Request a quote
Related

Standards, evidence and related repellency workflows

These pages cover the AATCC standards, the customer evidence and related water repellency tests.

Standard

AATCC TM22

Spray test for water repellency, and how contact angle complements it.

View use case

Standard

AATCC TM193

Aqueous liquid repellency with water and alcohol solutions.

View use case

Standard

AATCC TM118

Oil repellency by hydrocarbon resistance.

View use case

Case study

Iowa State University

Contact angle and roll off on coated fabrics with water and oils.

View use case

Case study

Canadian federal research team

Water repellent coatings on white polyester fabric.

View use case

Case study

University of Calgary

Electrospun fibre mats measured on a shared Dropometer.

View use case

Published paper

Electrospun polystyrene porous fibers

Solvent and voltage effects on fibre hydrophobicity.

View use case

Instrument

Dropometer

Contact angle and sliding angle in one kit.

View use case

Related use case

Functional hydrophobicity and self cleaning

All hydrophobicity use cases in one place.

View use case

Related use case

Ski wax hydrophobicity testing

Contact angle and roll off on waxed ski bases.

View use case

Related use case

Windshield rain repellent performance

Water repellency and roll off on glass.

View use case

How this page was created

Editorial and technical transparency notes for this page.

Transparency Details 4 checklist items
01

Drafting assistance

Drafted with Claude Opus 5.5 (Anthropic) using web search for sources, then edited by the Droplet Lab team.

02

Technical review

Reviewed and edited for technical accuracy by the Droplet Lab Team.

03

Verification steps

Standard identifiers, units, thresholds and key procedural claims are checked against cited sources before publication.

04

Updates

Reviewed every 12 months or when the underlying method changes.

Report a correction

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Correction Request

We work hard to keep this page accurate and up to date. If you spot an error (wrong revision/year, missing requirement, incorrect interpretation, or broken link), tell us and we'll review it.

Contact us to report a correction
Sources

References

1.
Kowalski, M., Salerno-Kochan, R., Kamińska, I., Cieślak, M. Quality and quantity assessment of the water repellent properties of functional clothing materials after washing. Materials 15(11):3825, 2022. https://doi.org/10.3390/ma15113825
2.
Hill, P.J., Kirton, D., Taylor, M., Blackburn, R.S. Quantifying water repellency by modifying spray test method AATCC TM22 to extend test duration allowing discrimination between similarly graded fabrics. AATCC Journal of Research 7(6), 2020. https://doi.org/10.14504/ajr.7.6.2
3.
Schellenberger, S. et al. Highly fluorinated chemicals in functional textiles can be replaced by re-evaluating liquid repellency and end-user requirements. Journal of Cleaner Production 217:134 to 143, 2019. https://doi.org/10.1016/j.jclepro.2019.01.160
4.
Hill, P.J., Taylor, M., Goswami, P., Blackburn, R.S. Substitution of PFAS chemistry in outdoor apparel and the impact on repellency performance. Chemosphere 181:500 to 507, 2017. https://doi.org/10.1016/j.chemosphere.2017.04.122
5.
Holmquist, H. et al. Properties, performance and associated hazards of state of the art durable water repellent (DWR) chemistry for textile finishing. Environment International 91:251 to 264, 2016. https://doi.org/10.1016/j.envint.2016.02.035
6.
ISO 4920:2012. Textile fabrics: determination of resistance to surface wetting (spray test). https://www.iso.org/standard/50706.html
7.
Commission Regulation (EU) 2024/2462 of 19 September 2024 amending Annex XVII to REACH as regards undecafluorohexanoic acid (PFHxA). https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=OJ:L_202402462
8.
New York Environmental Conservation Law, section 37-0121. https://www.nysenate.gov/legislation/laws/ENV/37-0121
9.
AATCC TM22. Test method for water repellency: spray test. See our AATCC TM22 page. https://dropletlab.com/industry-standards/aatcc-tm22/
10.
Melo, G.H.F., Sundararaj, U. Influence of mixed solvent in the morphology and hydrophobicity of electrospun polystyrene porous fibers. Macromolecular Rapid Communications 45:2400403, 2024. See our analysis of this paper. https://dropletlab.com/validation/citations/analysis/influence-of-mixed-solvent-in-the-morphology-and-hydrophobicity-of-electrospun-polystyrene-porous-fibers/
11.
Szlek, D., Fan, Frey, M. Multifunctional, flexible, electrospun lignin and PLA micro and nanofiber mats. Fibers 13:129, 2025. See our analysis of this paper. https://dropletlab.com/validation/citations/analysis/multifunctional-flexible-electrospun-lignin-pla-micro-nanofiber-mats-from-softwood-kraft-hardwood-alcell-and-switchgrass-celf-lignin-2/
12.
Chen, X. et al. Contact angle measurement with a smartphone. Review of Scientific Instruments 89(3):035117, 2018. https://pubs.aip.org/aip/rsi/article-abstract/89/3/035117/368179/Contact-angle-measurement-with-a-smartphone
13.
Surface tension measurement with a smartphone using a pendant drop. Colloids and Surfaces A: Physicochemical and Engineering Aspects. https://www.sciencedirect.com/science/article/abs/pii/S0927775717307744
14.
Droplet Lab validation papers
15.
Customer publications that cite the Dropometer
16.
Iowa State University case study
17.
Lignin and PLA fibre mats analysis