Porous surface coating fabrication for polyurethane synthetic leather: a review

Abstract

The use of leather in human history spans thousands of years, and the mass production of leather techniques also has a longstanding history over a century. The emergence of synthetic leather arose as a response to the market’s demand for an alternative due to a shortage of natural leather supply. However, the ongoing challenge of environmental pollution during the continuous development of synthetic leather to achieve comparable features to its natural counterparts has led the leather industry to deviate from its original goal of sustainability and environmentally friendliness, focused on “waste to worth” principle. Following the replacement of polyvinyl chloride (PVC) with polyurethane (PU) as the primary material for the surface layer in synthetic leather, waterborne polyurethane (WPU) and solvent-free polyurethane (SFPU) emerged as the principal environmentally friendly raw material for synthetic leather manufacturing. The free volume (FV) theory explains the relation between mass transfer in polymer films and increasing FV in polymer coatings, highlighting its benefit to water vapor permeability (WVP). The WVP of a synthetic leather is primarily influenced by the hydrophilicity and porous structure of the polymer coating, determined by the base fabrics and the raw polymer coating material. This paper reviews various methods for preparing porous structures to increase WVP of polymer films or coatings: chemical blowing, thermally expandable microspheres, laser drilling, hollow microspheres, surfactant-stabilized foam templates and Pickering aqueous foam templates. It also provides a concise outline of present issues and prospects in improving the breathability of synthetic leather derived from these approaches.

Keywords

Synthetic leather / Clean production / Polyurethane / Porous coating / Pickering foam

References

[1] Sudha TB, Thanikaivelan P, Aaron KP, Krishnaraj K, Chandrasekaran B. Comfort, chemical, mechanical, and structural properties of natural and synthetic leathers used for apparel. J Appl Polym Sci, 2009, 114(3): 1761-1767

[2] Ding W, Liu H, Li S, Remón J, Pang X, Ding Z. Providing natural organic pigments with excellent tanning capabilities: a novel “one-pot” tanning-dyeing integration strategy for sustainable leather Manufacturing. ACS Sustain Chem Eng, 2022, 10(51): 17346-17354

[3] Muthukrishnan L. Nanotechnology for cleaner leather production: a review. Environ Chem Lett, 2021, 19(3): 2527-2549

[4] Jones M, Gandia A, John S, Bismarck A. Leather-like material biofabrication using fungi. Nat Sustain, 2020, 4(1): 9-16

[5] Gao H, Lin J, Jia X, Zhao Y, Wang S, Bai H, Ma Q. Real-time authentication of animal species origin of leather products using rapid evaporative ionization mass spectrometry and chemometric analysis. Talanta, 2021, 225: 122069

[6] Bettenhausen CA. Sustainable materials make a play for the leather market. Chem Eng News, 2021, 99(8): 23-24

[7] Kanigel R, Faux real: Genuine leather and 200 years of inspired fakes, University of Pennsylvania Press. 2011.

[8] Covington AD, Tanning chemistry: the science of leather, Royal Society of Chemistry. 2009.

[9] Covington AD, Wise WR. Current trends in leather science. J Leather Sci Eng, 2020, 2(128

[10] Neiva AM, Pereira-Filho ER. Evaluation of the chemical composition of synthetic leather using spectroscopy techniques. Appl Spectrosc, 2018, 72(6921-932

[11] Chen M, Zhou D-L, Chen Y, Zhu P-X. Analyses of structures for a synthetic leather made of polyurethane and microfiber. J Appl Polym Sci, 2007, 103(2): 903-908

[12] Panel L, Leather carbon footprint-review of the European standard. 2017.

[13] Tian Y, Wang J, Zheng S, He X, Liu X. Research on the preparation and application of synthetic leather from coffee grounds for sustainable development. Sustainability, 2022

[14] Murlasits G, Wlasitsch G. New synthetic upper material with useful foot comfort hygiene properties. J Coated Fabr, 1985, 14(3): 172-184

[15] Patankar N, Varma J, Leather goods market size, share & trends analysis report by type (genuine leather, synthetic leather, vegan leather), by product, by region, and segment forecasts, 2023–2030, Grand View Research. 2023.

[16] Bahuguna A, Jandhyala H, Synthetic leather market size, share & trends analysis report by type (PU, PVC, bio-based), by application (footwear, clothing, furnishing, automotive, wallets, bags & purses), by region, and segment forecasts, 2022–2030, Grand View Research.

[17] Roh EK, Oh KW, Kim SH. Classification of synthetic polyurethane leather by mechanical properties according to consumers’ preference for fashion items. Fibers Polym, 2013, 14(10): 1731-1738

[18] Chang C-T, Lin K-L. Assessment of the strategies for reducing VOCs emission from polyurea-formaldehyde resin synthetic fiber leather industry in Taiwan. Resour Conserv Recycl, 2006, 46(4): 321-334

[19] Zhao S, Song X, Pei N, Zhang J, Liu S. Recovery technology of DMF from wet type polyurethane synthetic leather waste gas. Chin J Chem Eng, 2008, 16(3): 461-464

[20] Zafar F, Ghosal A, Sharmin E, Chaturvedi R, Nishat N. A review on cleaner production of polymeric and nanocomposite coatings based on waterborne polyurethane dispersions from seed oils. Prog Org Coat, 2019, 131: 259-275

[21] Zhou X, Li Y, Fang C, Li S, Cheng Y, Lei W, Meng X. Recent advances in synthesis of waterborne polyurethane and their application in water-based ink: a review. J Mater Sci Technol, 2015, 31(7): 708-722

[22] Kerton FM, Marriott R, Alternative solvents for green chemistry, R Soc Chem. 2013.

[23] Anastas PT, Warner JC. Principles of green chemistry. Green Chem Theory Pract, 1998, 29: 14821-14842

[24] Anastas P, Eghbali N. Green chemistry: principles and practice. Chem Soc Rev, 2010, 39(1): 301-312

[25] Prisacariu C, Polyurethane elastomers: from morphology to mechanical aspects, Springer Science & Business Media. 2011.

[26] Gurera D, Bhushan B. Fabrication of bioinspired superliquiphobic synthetic leather with self-cleaning and low adhesion. Colloids Surf A Physicochem Eng Asp, 2018, 545: 130-137

[27] Meyer M, Dietrich S, Schulz H, Mondschein A. Comparison of the technical performance of leather, artificial leather, and trendy alternatives. Coatings, 2021

[28] Zhao B, Qian Y, Qian X, Fan J, Liu F, Duo Y. Preparation and properties of split microfiber synthetic leather. J Eng Fibers Fabr, 2018, 13(2): 155892501801300203

[29] Zhu X, Li Q, Wang L, Wang W, Liu S, Wang C, Xu Z, Liu L, Qian X. Current advances of polyurethane/graphene composites and its prospects in synthetic leather: a review. Eur Polym J, 2021

[30] Defonseka C, Polymeric coating systems for artificial leather: standard and latest technologies, Walter de Gruyter GmbH & Co KG. 2022.

[31] Waentig F, Plastics in art: a study from the conservation point of view. 2008.

[32] Cheng J, Cao Y, Jiang S, Gao Y, Nie J, Sun F. Synthesis and performances of UV-curable polysiloxane-polyether block polyurethane acrylates for PVC leather finishing agents. Ind Eng Chem Res, 2015, 54(215635-5642

[33] Jia P, Zhang M, Hu L, Feng G, Bo C, Zhou Y. Synthesis and application of environmental castor oil based polyol ester plasticizers for poly(vinyl chloride). ACS Sustain Chem Eng, 2015, 3(9): 2187-2193

[34] Martinez-Razo LD, Martinez-Ibarra A, Vazquez-Martinez ER, Cerbon M. The impact of di-(2-ethylhexyl) phthalate and mono(2-ethylhexyl) phthalate in placental development, function, and pathophysiology. Environ Int, 2021, 146: 106228

[35] Feng G, Hu L, Ma Y, Jia P, Hu Y, Zhang M, Liu C, Zhou Y. An efficient bio-based plasticizer for poly(vinyl chloride) from waste cooking oil and citric acid: synthesis and evaluation in PVC films. J Clean Prod, 2018, 189: 334-343

[36] Lawson WD, Lynch CA, Richards JC. Corfam: research brings chemistry to footwear. Res Manag, 2016, 8(1): 5-26

[37] Bayer O. Das di-isocyanat-polyadditionsverfahren (polyurethane). Angew Chem, 1947, 59(9): 257-272

[38] Jutrzenka Trzebiatowska P, Santamaria Echart A, Calvo Correas T, Eceiza A, Datta J. The changes of crosslink density of polyurethanes synthesised with using recycled component. Chemical structure and mechanical properties investigations. Prog Org Coat, 2018, 115: 41-48

[39] Dieterich D, Grigat E, Hahn W, Hespe H, Schmelzer H, Polyurethane handbook, Oertel, G., Ed. 1985; 34.

[40] Akindoyo JO, Beg MDH, Ghazali S, Islam MR, Jeyaratnam N, Yuvaraj AR. Polyurethane types, synthesis and applications—a review. RSC Adv, 2016, 6(115): 114453-114482

[41] Chattopadhyay DK, Raju KVSN. Structural engineering of polyurethane coatings for high performance applications. Prog Polym Sci, 2007, 32(3): 352-418

[42] Madbouly SA, Otaigbe JU. Recent advances in synthesis, characterization and rheological properties of polyurethanes and POSS/polyurethane nanocomposites dispersions and films. Prog Polym Sci, 2009, 34(12): 1283-1332

[43] Engels HW, Pirkl HG, Albers R, Albach RW, Krause J, Hoffmann A, Casselmann H, Dormish J. Polyurethanes: versatile materials and sustainable problem solvers for today's challenges. Angew Chem Int Ed Engl, 2013, 52(36): 9422-9441

[44] Sur S-H, Choi P-J, Ko J-W, Lee J-Y, Lee Y-H, Kim H-D. Preparation and properties of DMF-based polyurethanes for wet-type polyurethane artificial leather. Inter J Polym Sci, 2018, 2018: 1-9

[45] Han Y, Hu J, Xin Z. Facile preparation of high solid content waterborne polyurethane and its application in leather surface finishing. Prog Org Coat, 2019, 130: 8-16

[46] Lyu B, Cheng K, Gao D, Ma J, Zhang H, Shi L, Xu X. Enhanced hygienic property of solvent-free polyurethane film by hollow TiO₂ microspheres. J Clean Prod, 2019, 209: 608-616

[47] Feng L, Wang W, Song B, Zhu X, Wang L, Shao R, Li T, Pei X, Wang L, Qian X, Xu Z. Synthesis of P, N and Si-containing waterborne polyurethane with excellent flame retardant, alkali resistance and flexibility via one-step synthetic approach. Prog Org Coat, 2023

[48] Xu N, Tao Y, Wang X, Luo Z. Construction of a novel substrate of unfigured islands-in-sea microfiber synthetic leather based on waste collagen. ACS Omega, 2021, 6(40): 26086-26097

[49] Chen Y, Fan H, Liu R, Yuan J. Nano-SiO₂ in-situ hybrid polyurethane leather coating with enhanced breathability. Fibers Polym, 2010, 11: 241-248

[50] Kang SY, Ji Z, Tseng LF, Turner SA, Villanueva DA, Johnson R, Albano A, Langer R. Design and synthesis of waterborne polyurethanes. Adv Mater, 2018, 30(18): e1706237

[51] Xiao Y, Fu X, Zhang Y, Liu Z, Jiang L, Lei J. Preparation of waterborne polyurethanes based on the organic solvent-free process. Green Chem, 2016, 18(2412-416

[52] Water-based Polyurethane leather 2025–2033 Analysis: trends, competitor dynamics, and growth opportunities, Data Insights Market. 2025.

[53] Liu X, Hong W, Chen X. Continuous production of water-borne polyurethanes: a review. Polymers (Basel), 2020

[54] Solvent free polyurethane synthetic leather market size | global report, Global Growth Insights. 2025.

[55] Gupta B, Hemachendra K, Walsh W. Solventless fabric coating by radiation curing part III: transfer coating of fabrics with EB cure for leather-like applications. J Coated Fabr, 1978, 8(2): 183-196

[56] Durst P. Pu transfer coating of fabrics for leather-like fashion products. J Coated Fabr, 1985, 14(4): 227-241

[57] Kinge A, Landage S, Wasif A. Nonwoven for artificial leather. Int J Adv Res Eng Appl Sci, 2013, 2(18): 18-33

[58] Angelova RA, Non-woven textiles in the indoor environment, Intech, Rijeka, Croatia. 2016.

[59] Fan Z, Zhao C, Wu J, Cai Y, Zhou J, Zhang J, Gong X, Xuan S. Intelligent safeguarding leather with excellent energy absorption via the toughness-flexibility coupling designation. Compos Part A Appl Sci Manuf, 2022

[60] Wang X, Xu N, Guo P, Wang Q. Improving moisture absorbent and transfer abilities by modifying superfine fiber synthetic leather base with collagen-chrome tannins. Text Res J, 2016, 86(7): 765-775

[61] Heng Z, Xiaoming Q, Qi Z, Zhaohang Y. Research on structure characteristics and filtration performances of PET-PA6 hollow segmented-pie bicomponent spunbond nonwovens fibrillated by hydro entangle method. J Ind Text, 2014, 45(1): 48-65

[62] Zhang H, Zhang X, Qian X, Guo C. Dual-role mechanism of dimethyl sulfone in the preparation of surface layer membrane of superfine fiber veneer synthetic leather. Ind Eng Chem Res, 2021, 60(47): 17259-17267

[63] Xu N, Wang X, Wang L, Zheng Y, Zhang F, Guo P. Modification of PA/PU superfine non-woven fiber for “breath” property using collagen and vegetable tannins. J Ind Text, 2018, 48(10): 1593-1615

[64] Zhang Z, Tu W, Peijs T, Bastiaansen CWM. Fabrication and properties of poly(tetrafluoroethylene) nanofibres via sea-island spinning. Polymer, 2017, 109: 321-331

[65] Song B, Cao Y, Wang L, Shen Y, Qian X. Properties and structure of thermoplastic polyvinyl alcohol/polyamide sea-island fibers. Polymers, 2023

[66] Nakata K, Fujii K, Ohkoshi Y, Gotoh Y, Nagura M, Numata M, Kamiyama M. Poly(ethylene terephthalate) nanofibers made by sea-island-type conjugated melt spinning and laser-heated flow drawing. Macromol Rapid Commun, 2007, 28(6): 792-795

[67] Sureshkumar P, Thanikaivelan P, Phebe K, Krishnaraj K, Jagadeeswaran R, Chandrasekaran B. Investigations on structural, mechanical, and thermal properties of pineapple leaf fiber-based fabrics and cow softy leathers: an approach toward making amalgamated leather products. J Nat Fibers, 2012, 9(1): 37-50

[68] da Silva CJG, de Medeiros ADLM, de Amorim JDP, Nascimentodo HA, Converti A, Costa AFS, Sarubbo LA. Bacterial cellulose biotextiles for the future of sustainable fashion: a review. Environ Chem Lett, 2021, 19(4): 2967-2980

[69] Elsacker E, Vandelook S, Peeters E. Recent technological innovations in mycelium materials as leather substitutes: a patent review. Front Bioeng Biotechnol, 2023, 11: 1204861

[70] Xu N, Xing Y, Wang X, Ren L, Qiang T. Construction of waste-collagen modified superfine fiber substrates based on “click” chemistry: moisture absorption and permeability. J Appl Polym Sci, 2021

[71] Ren L, Wang N, Sun S, Qiang T, Wang X. Improvement of the sanitary property of microfiber synthetic leather base by PAMAM. J Eng Fibers Fabr, 2015, 10(2): 155892501501000205

[72] Basak S, Shakyawar DB, Samanta KK, Kumar N, Bhowmick M, Ghosh S, A review on natural fibre-based engineered flexible composite: a futuristic development as leather alternative. J Text Inst. (2024) 1–18.

[73] Lao L, Shou D, Wu YS, Fan JT. “Skin-like” fabric for personal moisture management. Sci Adv, 2020, 6(14eaaz0013

[74] Yan K, Liu C, Ma J. Dendritic fibrous nanosilica loaded chitosan for improving water vapor permeability and antibacterial properties of waterborne polyurethane acrylate membranes. J Clean Prod, 2021

[75] Wu Y, Wang AH, Zheng RR, Tang HQ, Qi XY, Ye B. Laser-drilled micro-hole arrays on polyurethane synthetic leather for improvement of water vapor permeability. Appl Surf Sci, 2014, 305: 1-8

[76] Meng QB, Lee S-I, Nah C, Lee Y-S. Preparation of waterborne polyurethanes using an amphiphilic diol for breathable waterproof textile coatings. Prog Org Coat, 2009, 66(4382-386

[77] Xu H, Ning H, Chen Y, Fan H, Shi B. Sulfanilamide-conjugated polyurethane coating with enzymatically-switchable antimicrobial capability for leather finishing. Prog Org Coat, 2013, 76(5): 924-934

[78] Lewin M, Penhasi A. Novel porous polyurethane films. Polym Adv Technol, 1998, 9(3): 210-215

[79] Chen D, Liang Z, Liu Y, Zhang Z, Li Z. Enhancement and control of water vapor permeability and thermal conductivity of polymers: a review. Polym Adv Technol, 2023, 34(5): 1451-1466

[80] Jonquieres A, Clément R, Lochon P. Permeability of block copolymers to vapors and liquids. Prog Polym Sci, 2002, 27(9): 1803-1877

[81] Lee S-T, Scholz DPK, Polymeric foams: Technology and developments in regulation, process, and products, CRC Press. 2008.

[82] Coste G, Negrell C, Caillol S. From gas release to foam synthesis, the second breath of blowing agents. Eur Polym J, 2020

[83] Chemical Blowing Agent Market, Verified Market Reports. 2025.

[84] Easley AD, Mangano A, Fors BP. Safer polyurethane foams with cyclic carbonates. Angew Chem Int Ed Engl, 2023, 62(20): e202218062

[85] Wade R. Borohydride-based blowing agent. Ind Eng Chem, 1960, 52(120-21

[86] Petlitckaia S, Poulesquen A. Design of lightweight metakaolin based geopolymer foamed with hydrogen peroxide. Ceram Int, 2019, 45(1): 1322-1330

[87] Vonzeppelin F, Hirscher M, Stanzick H, Banhart J. Desorption of hydrogen from blowing agents used for foaming metals. Compos Sci Technol, 2003, 63(16): 2293-2300

[88] Lobos J, Thirumuruganandham SP, Rodriguez-Perez MA. Density gradients, cellular structure and thermal conductivity of high-density polyethylene foams by different amounts of chemical blowing agent. Polymers, 2022

[89] Yamsaengsung W, Sombatsompop N. Effect of chemical blowing agent on cell structure and mechanical properties of EPDM foam, and peel strength and thermal conductivity of wood/NR composite-EPDM foam laminates. Compos Part B Eng, 2009, 40(7): 594-600

[90] Da Silva EF, Svendsen HF. Ab initio study of the reaction of carbamate formation from CO₂ and alkanolamines. Ind Eng Chem Res, 2004, 43(13): 3413-3418

[91] Quinn S. Chemical blowing agents: providing production, economic and physical improvements to a wide range of polymers. Plast Addit Compound, 2001, 3(5): 16-21

[92] Robledo-Ortiz JR, Zepeda C, Gomez C, Rodrigue D, González-Núñez R. Non-isothermal decomposition kinetics of azodicarbonamide in high density polyethylene using a capillary rheometer. Polym Test, 2008, 27(6): 730-735

[93] Yin N, Chen S, Li Z, Ouyang Y, Hu W, Tang L, Zhang W, Zhou B, Yang J, Xu Q, Wang H. Porous bacterial cellulose prepared by a facile surfactant-assisted foaming method in azodicarbonamide-NaOH aqueous solution. Mater Lett, 2012, 81: 131-134

[94] Gurunathan T, Arukula R. High performance polyurethane dispersion synthesized from plant oil renewable resources: a challenge in the green materials. Polym Degrad Stab, 2018, 150: 122-132

[95] Renshaw J, Cannon J. Antioxidant-associated color problems in vinyl foams. Polym Eng Sci, 1974, 14(6): 473-477

[96] Ma C, Wang S, Li Y, Yu T, Yao Y, Du H, Cai Q. Preparation of epoxy resin foam by composite foaming agent prepared from microporous silica and 4,4′-bisoxybenzenesulfonyl hydrazide. J Appl Polym Sci, 2022

[97] Long J, Gao Q, Fan H, Xiang J. Low-temperature foaming approach for solvent-free polyurethane coating based on dual carbon strategy. ACS Sustain Chem Eng, 2025, 13(17): 6235-6248

[98] Banerjee R, Ray SS. Foamability and special applications of microcellular thermoplastic polymers: a review on recent advances and future direction. Macromol Mater Eng, 2020

[99] Drozdov AD, de Claville Christiansen J. The effect of porosity on elastic moduli of polymer foams. J Appl Polym Sci, 2019

[100] Berardi U, Madzarevic J. Microstructural analysis and blowing agent concentration in aged polyurethane and polyisocyanurate foams. Appl Therm Eng, 2020

[101] Yusa A, Yamamoto S, Goto H, Uezono H, Asaoka F, Wang L, Ando M, Ishihara S, Ohshima M. A new microcellular foam injection-molding technology using non-supercritical fluid physical blowing agents. Polym Eng Sci, 2016, 57(1): 105-113

[102] Brondi C, Di Caprio MR, Scherillo G, Di Maio E, Mosciatti T, Cavalca S, Parenti V, Corti M, Iannace S. Thermosetting polyurethane foams by physical blowing agents: chasing the synthesis reaction with the pressure. J Supercrit Fluids, 2019

[103] Verschoor L, Verschoor AH. Nonoccupational and occupational exposure to isocyanates. Curr Opin Pulm Med, 2014, 20(2): 199-204

[104] Gao Q, Long J, Fan W, Wei H, Wang Z, Fan H, Xiang J. In-situ construction of solvent-free polyurethane foam coating based on carbon peak strategy. Prog Org Coat, 2024

[105] Tomalino M, Bianchini G. Heat-expandable microspheres for car protection production. Prog Org Coat, 1997, 32(1–4): 17-24

[106] Pak AR, Park JH, Lee SG. Blowing properties and functionality of thermoplastic polyester film using thermally expandable microcapsules. Polymers, 2019

[107] Kawaguchi Y, Oishi T. Synthesis and properties of thermoplastic expandable microspheres: the relation between crosslinking density and expandable property. J Appl Polym Sci, 2004, 93(2): 505-512

[108] Rheem MJ, Jung H, Ha J, Baeck S-H, Shim SE. Suspension polymerization of thermally expandable microspheres using low-temperature initiators. Colloid Polym Sci, 2016, 295(1): 171-180

[109] Thermally expandable microspheres growth pathways: strategic analysis and forecasts 2025–2033, Data Insights Market. 2025.

[110] Expandable microsphere market size, share, growth, industry forecast - 2032, Consegic Business Intelligence. 2025.

[111] Zonta E, Valentini F, Dorigato A, Fambri L, Pegoretti A. Evaluation of the salt leaching method for the production of ethylene propylene diene monomer rubber foams. Polym Eng Sci, 2020, 61(1): 136-153

[112] Wei H, Luo H, Li J, Fan H, Xiang J, Chen Y, Yan J. Large size, sensitive response thermally expandable microspheres for the manufacture of suede-like leather. J Appl Polym Sci, 2022

[113] Yuan T, Zhang C, Zhou C, Tu W, Hu J, Yang Z, Fabrication of novel thermal-expandable microcapsules and their applications in intumescent flame-retardant water-based coatings. 2017.

[114] Sanderson MA, Ebbitt G, Deacon P, Wang S, Woodcock R, Performance of perforated leather seats: SEA predictions and validation, INTER-NOISE and NOISE-CON congress and conference proceedings, Institute of Noise Control Engineering. 2002; pp. 2172–2177.

[115] Doroudian M, Kolich M, Almasi G, Medoro M, Dwarampudi R, Battoei M, Salokhe S, Virtual temperature controlled seat performance test, SAE Technical Paper Series, 2018.

[116] Roh EK. Effect of punching on physical and mechanical properties of leathers: focus on car seat covers. J Eng Fibers Fabr, 2019

[117] Kannatey-Asibu Jr E, Principles of laser materials processing: developments and applications, John Wiley & Sons (2023).

[118] Hu A, Laser micro-nano-manufacturing and 3D microprinting, Springer (2020).

[119] Upadhyay N, Laser drilling market challenges, key vendors, drivers, trends and forecast by 2031, The Insight Partners (2024).

[120] Liang G, Bo R, Yewei W, Xin T, Qingmao Z, Improving water vapor permeability of polyurethane synthetic leather by drilling micro-hole arrays with 343 nm femtosecond laser, high power laser and particle beams 30(4) (2018).

[121] Wang H, Lin H, Wang C, Zheng L, Hu X. Laser drilling of structural ceramics-a review. J Eur Ceram Soc, 2017, 37(4): 1157-1173

[122] Rusu A-N, Dumitrascu D-I, Dumitrascu A-E. Monitoring, control and optimization of laser micro-perforation process for automotive synthetic leather parts. Processes, 2024

[123] Hasan M, Zhao J, Jiang Z. A review of modern advancements in micro drilling techniques. J Manuf Process, 2017, 29: 343-375

[124] Cai Y, Chen Y, Hong X, Liu Z, Yuan W. Porous microsphere and its applications. Int J Nanomed, 2013, 8: 1111-1120

[125] Prieto G, Tuysuz H, Duyckaerts N, Knossalla J, Wang GH, Schuth F. Hollow nano- and microstructures as catalysts. Chem Rev, 2016, 116(22): 14056-14119

[126] Mondal S, Hu JL, Yong Z. Free volume and water vapor permeability of dense segmented polyurethane membrane. J Membr Sci, 2006, 280(1–2): 427-432

[127] Porous silica hollow glass sphere market’s role in emerging tech: insights and projections 2025–2033, Data Insights Market, 2025.

[128] Bao Y, Yang Y, Ma J. Fabrication of monodisperse hollow silica spheres and effect on water vapor permeability of polyacrylate membrane. J Colloid Interface Sci, 2013, 407: 155-163

[129] Bao Y, Wang T, Kang Q, Shi C, Ma J. Micelle-template synthesis of hollow silica spheres for improving water vapor permeability of waterborne polyurethane membrane. Sci Rep, 2017, 7: 46638

[130] Hou X, Zhao H, Zhang W, Ma H, Li R, Han B, Zhang Y, Wang J-J. Moisture-regulating microcapsule and its enhanced water vapor permeability of leather polyurethane coating. Prog Org Coat, 2022

[131] Guo X, Lyu B, Gao D, Cheng K, Ma J, Yang N, Yu Y, Zhao S, Shi L, Kou M. Water vapor permeability and self-cleaning properties of solvent-free polyurethane improved by hollow nano-TiO₂ spheres. J Appl Polym Sci, 2020

[132] Lyu B, Guo X, Cheng K, Gao D, Ma J, Yang N, Zhao S, Liu C, Warda B, Qin J. Construction of double-shell hollow TiO₂ toward solvent-free polyurethane films. Ind Eng Chem Res, 2020, 59(34): 15271-15282

[133] Mezzenga R, Ruokolainen J, Fredrickson GH, Kramer EJ. High internal phase polymeric emulsions by self-assembly of colloidal systems. Macromolecules, 2003, 36(124466-4471

[134] Menner A, Haibach K, Powell R, Bismarck A. Tough reinforced open porous polymer foams via concentrated emulsion templating. Polymer, 2006, 47(22): 7628-7635

[135] Lau THM, Wong LLC, Lee K-Y, Bismarck A. Tailored for simplicity: creating high porosity, high performance bio-based macroporous polymers from foam templates. Green Chem, 2014, 16(4): 1931-1940

[136] Weaire D, Cox S, Brakke K, Liquid foams-precursors for solid foams, cellular ceramics: structure, manufacturing, properties and applications. (2005) 18–29.

[137] Andrieux S, Quell A, Stubenrauch C, Drenckhan W. Liquid foam templating—a route to tailor-made polymer foams. Adv Colloid Interface Sci, 2018, 256: 276-290

[138] Ikem VO, Menner A, Horozov TS, Bismarck A. Highly permeable macroporous polymers synthesized from pickering medium and high internal phase emulsion templates. Adv Mater, 2010, 22(32): 3588-3592

[139] Song W, Konstantellos G, Li D, Lee K-Y. Short carbon fibre-reinforced epoxy foams with isotropic cellular structure and anisotropic mechanical response produced from liquid foam templates. Compos Sci Technol, 2019

[140] McClements DJ. Critical review of techniques and methodologies for characterization of emulsion stability. Crit Rev Food Sci Nutr, 2007, 47(7): 611-649

[141] Kim Y-H, Koczo K, Wasan DT. Dynamic film and interfacial tensions in emulsion and foam systems. J Colloid Interface Sci, 1997, 187(1): 29-44

[142] Mouquet A, Khidas Y, Saison T, Faou JY, Pitois O. Well-controlled foam-based solid coatings. Soft Matter, 2019, 15(25): 5084-5093

[143] Chandran Suja V, Rodriguez-Hakim M, Tajuelo J, Fuller GG. Single bubble and drop techniques for characterizing foams and emulsions. Adv Colloid Interface Sci, 2020, 286: 102295

[144] van der Net A, Gryson A, Ranft M, Elias F, Stubenrauch C, Drenckhan W. Highly structured porous solids from liquid foam templates. Colloids Surf A Physicochem Eng Asp, 2009, 346(1–3): 5-10

[145] Zheng G, Lu M, Rui X, Sun Y. The effect of acrylate on structure and properties of waterborne polyurethane porous coated fabrics. J Appl Polym Sci, 2017

[146] Chen N, Li Y, Qu J, Wang JY. Polyurethane electrospun fiber biomimetics membrane for constructing the structure of grain layer with good breathability for cattle split leather. J Am Leather Chem Assoc. 2021;116(8).

[147] Zhao B, Qian Y, Qian X, Fan J, Feng Y. Fabrication and characterization of waterborne polyurethane/silver nanocomposite foams. Polym Compos, 2018, 40(41492-1498

[148] Pugh RJ. Foaming, foam films, antifoaming and defoaming. Adv Colloid Interface Sci, 1996, 64: 67-142

[149] Bureiko A, Trybala A, Kovalchuk N, Starov V. Current applications of foams formed from mixed surfactant-polymer solutions. Adv Colloid Interface Sci, 2015, 222: 670-677

[150] Binks BP, Horozov TS. Colloidal particles at liquid interfaces, Cambridge University Press. 2006.

[151] Briceno-Ahumada Z, Langevin D. On the influence of surfactant on the coarsening of aqueous foams. Adv Colloid Interface Sci, 2017, 244: 124-131

[152] He Y, Yazhgur P, Salonen A, Langevin D. Adsorption-desorption kinetics of surfactants at liquid surfaces. Adv Colloid Interface Sci, 2015, 222: 377-384

[153] Amani P, Miller R, Javadi A, Firouzi M. Pickering foams and parameters influencing their characteristics. Adv Colloid Interface Sci, 2022

[154] Pickering SU. Cxcvi. emulsions. J Chem Soc Trans, 1907, 91: 2001-2021

[155] Ramsden W. Separation of solids in the surface-layers of solutions and ‘suspensions’ (observations on surface-membranes, bubbles, emulsions, and mechanical coagulation)—preliminary account. Proceed R Soc London, 1904, 72(477–486): 156-164

[156] Wu J, Zhou J, Shi Z, Wang C, Ngai T, Lin W. Pickering aqueous foam templating: a promising strategy to fabricate porous waterborne polyurethane coatings. Coll Leather, 2023, 5(1): 10

[157] Tan H, Tu S, Zhao Y, Wang H, Du Q. A simple and environment-friendly approach for synthesizing macroporous polymers from aqueous foams. J Colloid Interface Sci, 2018, 509: 209-218

[158] Gadgeel A, Mhaske ST. Synthesis of microporous interconnected polymeric foam of poly(glycidyl methacrylate-co-divinyl benzene-co-butyl acrylate) by using aqueous foam as a template. Colloids Surf A Physicochem Eng Asp, 2019, 563: 193-205

[159] Yu H, Zhu Y, Xu J, Wang A. Fabrication porous adsorbents templated from modified sepiolite-stabilized aqueous foams for high-efficient removal of cationic dyes. Chemosphere, 2020, 259: 126949

[160] Zhang Z, Tan H, Zhao Y, Wang Q, Wang H. Facile synthesis of macroporous zwitterionic hydrogels templated from graphene oxide-stabilized aqueous foams. J Colloid Interface Sci, 2019, 553: 40-49

[161] Huang Y, Yang J, Chen L, Zhang L. Chitin nanofibrils to stabilize long-life Pickering foams and their application for lightweight porous materials. ACS Sustain Chem Eng, 2018, 6(810552-10561

[162] Palmer M, Hatley H. The role of surfactants in wastewater treatment: impact, removal and future techniques: a critical review. Water Res, 2018, 147: 60-72

[163] Abidnejad R, Beaumont M, Tardy BL, Mattos BD, Rojas OJ. Superstable wet foams and lightweight solid composites from nanocellulose and hydrophobic particles. ACS Nano, 2021

[164] Yu H, Zhu Y, Duan F, Wang A. Porous materials prepared from eco-friendly attapulgite and gallnut stabilized aqueous foam templates for high-efficient removal of organic pollutants. Mater Today Sustain, 2023

[165] Yu H, Zhu Y, Hui A, Yang F, Wang A. Removal of antibiotics from aqueous solution by using porous adsorbent templated from eco-friendly Pickering aqueous foams. J Environ Sci (China), 2021, 102: 352-362

[166] Shi Z, Sheng Y, Wu J, Cui J, Lin W, Ngai T. Porous waterborne polyurethane films templated from Pickering foams for fabrication of synthetic leather. Langmuir, 2024, 40(9): 4751-4761

[167] Chen D, Liu Y, Zhang Z, Li S, Yang K, Li Z. Ingeniously incorporating hollow mesoporous silica into waterborne polyurethane film to improve water vapor permeability. Mater Lett, 2022

Funding

University Grants Committee(Research Matching Grant Scheme 8601309)

RIGHTS & PERMISSIONS

The Author(s)