DMF-Free Eco PU Solutions: Water-Based PU & Non-Solvent PPU

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Introduction & Cases

Ocean Plastics Co., Ltd.'s DMF-free eco-friendly PU consists of the following 2 foundational categories and elements like biobased / biomass, biodegradable, carbon capture, or recycled materials for more advanced sustainable developments:
(A) Water-Based Polyurethane Leather, Film / Hyperfoam, Base, and Resin. Also known as "waterborne polyurethane," "water-based PU," or "waterborne PU." We at OPC also call it "WBPU."
(B) Solvent-Free Prepolymer Polyurethane Leather, Film, and Resin (PPU, or "Prepolymer PU"), a non-solvent type PU we call "PPU."

Initiating R&D in 1998, we have strived towards greener vegan PU leather solutions with added value and succeeded in developing DMF-free water-based PU (waterborne PU) and PPU leather technologies (see PU Knowledge→DMF, Water-Based PU V.S. Solvent-Based PU). They can be customized by varying resin formulation, release paper, topcoat, printing, embossing, color, foam density, and backing. Antifungal, antibacterial, deodorant, alcohol-resistant and other enhancements can be added. We have significantly reduced energy & water consumption, VOC & carbon emission, and industrial wastewater. With this green, diverse product range, we present a holistic yet customized approach in collaborating with our customers. Our experience and technology repertoire have helped resolve their problems, such as passing CA Prop 65, OEKO-TEX Standard 100 Product Class 1, and REACH.

Example 1: Customer’s original material failed the DMF test (see PU Knowledge→DMF): they needed DMF below 500 ppm, 100 ppm, 10 ppm, or not detectable. Our products do not use DMF; they will be n.d., not detected.
Example 2: Some came for baby products. They needed hypoallergenic PU with no migratable DMF and RSL substances, meeting OEKO TEX Standard 100 Annex 4 Product Class 1. We delivered.
Example 3: Some found the water-based PU they acquired elsewhere stiff and paper-like, with obvious wrinkles when folded. We offered softer, smoother water-based PU leather.
Example 4: Some found water-based PU leather elsewhere to have subpar performance, failing flexing and adhesion tests. By formulating our water-based PU and PPU, we offered an eco-friendly vegan leather option with higher resistance to flexing (100K flexes) and high coating adhesion (up to 7~9 kg/3cm depending on adhesive & substrate). Our water-based PU could even be used on basketball, football, or baseball with impact resistance. Note: coating adhesion is referred to as peel strength, peeling strength, and bond strength by different industries.
Example 5: When customers found other eco-friendly PU or water-based PU elsewhere breaking down too fast, we provided water-based PU and PPU leather with 5, 7, or 10 years hydrolysis resistance.
Example 6: Some customers did not come for PU leather at all. They wanted something special. We gave them our hyperfoam, PU film, or PU resin compounds.

Water-Based Polyurethane (Waterborne Polyurethane, WBPU)

Water-based polyurethane (waterborne polyurethane), or water-based PU, is a PU resin consisting of polyurethane polymers dispersed in water as an emulsion (see PU Knowledge→PU Resin). Using water-based resin (waterborne resin), we’ve created water-based PU leather (waterborne PU leather), film / foil, hyperfoam, and base. In the traditional solvent-based system, a lot of DMF (see PU Knowledge→DMF) and heated water tanks are used in making PU leather (see PU Knowledge→Wet Process and PU Coagulation for Solvent-Based PU Leather, Water-Based PU V.S. Solvent-Based PU). Compared with that, our water-based PU products are DMF-free, with significantly reduced energy & water consumption, VOC & CO2 emission, and almost no industrial wastewater. We’ve also eliminated many harmful substances used in the solvent-based system. Water-based PU is eco-friendly, hypoallergenic, lightweight, and versatile, ranging from soft to hard textures.

• What’s special about Ocean Plastics Co., Ltd.’s water-based PU technology?

  1. Our water-based PU suede has good color-fastness (AATCC 8 level 3.5-4), water-repellence, and abrasion resistance v.s. buffed nubuck DMF-based wet-process PU (color fastness level 2-3).
  2. Our water-based PU film: 0.1-0.8 mm thick. DMF-solvent based only 0.3-0.7 mm.
  3. Our water-based PU hyperfoam: 0.2-1.7 mm thick foam with higher expansion ratios beyond solvent-based.
  4. PU foam layer expansion ratios and densities adjustable.
  5. PU foam product and PU film’s foam layer can have smooth surface. On the other hand, DMF solvent-based PU foam layer is imprinted with pattern from a backing due to production constraints.
  6. We offer a base (foam layer + backing) with smooth, even foam surface, without backing fiber sticking out.
  7. Hydrolysis resistance 5, 7, or 10 years. Non-yellowing grade 4-5. Soft, draping to firm, hard texture available.
  8. We synthesize our own water-based PU resin to control PU leather quality.

• Our Water-Based PU products

  1. Water-Based PU Leather (Eco Light® Leather):green vegan leather made of water-based PU resin. Raw material and production process are DMF-free (see PU Knowledge→DMF), without the toxic solvent dimethylformamide (DMF) or the large amount of industrial wastewater of traditional solvent-based PU (see PU Knowledge page→Water-Based PU V.S. Solvent-Based PU). Product is DMF-free, hypoallergenic, and lightweight. Special functions: antibacterial, antifungal, alcohol resistant, deodorant, faster heat convection properties (cooling effect), etc. available.
     
     
     
     
  2. Water-Based PU Film / Foil (Eco Light® Film):PU film or foil can be skin + foam, only skin, or only foam (see PU Knowledge→PU Leather Structure). While solvent-based PU is only 0.3-0.7 mm thick due to production constraints, ours is 0.1-0.8 mm. It can be used as a membrane, surface, or cushion. Special functions: water vapor permeable, breathable, antibacterial, antifungal, alcohol resistant, deodorant, faster heat convection properties (cooling effect), etc. available.
     
     
     
     
  3. Water-Based PU Hyperfoam:PU foam made with water-based PU resin reaching foam expansion ratios beyond the DMF solvent-based system. We can achieve a greater range of foam thickness and expansion ratio. Solvent-based foam layer is 0.3-0.6 mm. We can do 0.2-1.7 mm. With lighter density and higher foam expansion, hyperfoam is very breathable and water-vapor permeable. Other functions: antibacterial, antifungal, deodorant, alcohol resistant, faster heat convection properties (cooling effect), etc. are available.
     
     
     
     
  4. Water-Based PU Base (Eco Light® Base):the base is foam layer + backing (see PU Knowledge page→PU Leather Structure). Customers don’t make the foam+backing themselves; they just laminate a top layer. In the solvent-based system, due to production constraints, the foam surface can be a bit uneven, and in worst case scenario, with backing fiber visible. However, with our method, we can make it smoother and flatter.
     
     
     
     
  5. Water-Based Polyurethane Resin:aka water-based PU resin, waterborne PU resin, aqueous PU resin, aqueous polyurethane dispersion. DMF-free. We synthesize our polyurethane polymers with hydrophilic functional groups attached at the molecular level. This allows the polymer particles to disperse in water as a white liquid emulsion.
     
     
     
     
  6. Stereotypes of water-based PU?There are negative stereotypes about water-based PU leather: stiff and paper-like, thick wrinkles when folded, weak physical performance (failing flexing resistance, abrasion, etc.), or PU degrading into sticky surfaces or tiny pieces (hydrolysis) in a short period of time. These might be true elsewhere. However, we have a team that continuously tackle different factors and overcome technical hurdles. Our water-based PU does not fit these stereotypes. Ours has been used on basketball, football, baseball, sporting gloves, hockey skates, upholstery, computing accessories, garment, shoes, etc., ranging from soft to firm demands.

Solvent-Free Prepolymer Polyurethane (PPU)

Prepolymer polyurethane, which we call PPU, is a solvent-free (non-solvent) system different from both solvent-based and water-based PU. We synthesize PPU resin to an intermediate prepolymer stage, then coat it, heat dry it and laminate it with backing to create the PPU leather. With heat, the resin prepolymers crosslink further, forming a 3D net-like molecular structure, which becomes the PPU leather’s solid PU layer on the substrate backing. In synthesizing PPU resin, we do not use solvents or DMF (see PU Knowledge→DMF), and the molecular weight of PPU is higher than water-based PU. This results in a DMF-free, non-solvent resin that has close to 100% solid content, providing stronger physical performance in PPU leather than water-based PU, at times stronger than DMF solvent-based PU. Because of this, we call our PPU products Eco Solid®.
Like water-based PU, the PPU system is DMF-free and hypoallergenic, with significantly reduced water & energy consumption, VOC & CO2 emission, and almost no industrial wastewater. PPU leather is eco-friendly, hypoallergenic, firm, tough, rebound resilient, and durable. Its texture is close to TPU, but it is more heat resistant.

• What’s special about Ocean Plastics Co., Ltd.’s PPU technology?

  1. PPU resin: solvent-free and DMF-free PU prepolymers. Texture is close to high-solid PU (see PU Knowledge→PU Resin), but high-solid PU is dissolved in DMF, is quite viscous, and sometimes requires dilution with solvents to use in coating. On the other hand, PPU resin viscosity and pot life are manageable, eliminating the need for solvents.
  2. PPU leather: 100K flexes in flexing resistance, 7-10 kg/3cm adhesion (peel strength), 10-year hydrolysis resistance possible.
  3. Fills gap in our product spectrum: higher rebound resilience, toughness, firmness, flexing resistance, resistance to cracking at low temperature, coating adhesion (peel strength), and density than water-based PU, at times higher than solvent-based PU.
  4. Patent leather made of PPU won’t have fold marks when folded. Surface retains a high gloss.
  5. Foam layer expansion ratio and density customizable by target application and performance requirement.

• Our Solvent-Free PPU products

  1. PPU Leather (Eco Solid® Leather):an eco-friendly vegan leather made of PPU resin. PPU is solvent-free, so it is non-solvent and DMF-free. Higher rebound resilience, toughness, firmness, flexing resistance, resistance to cracking at low temperature, coating adhesion (peel strength), and density than water-based PU, at times higher than traditional solvent-based PU. Suitable for upholstery, automotive, and products needing more physical requirements.
     
     
     
     
  2. PPU Film (Eco Solid® Film):0.1-0.4 mm thick. Suited for more rebound resilient, firm, or durable applications such as upholstery.
     
     
     
     
  3. PPU Resin:polyurethane prepolymer chains without solvent, synthesized to an intermediate molecular weight that can be further polymerized. Since the polyurethane is still prepolymeric, the resin remains liquid even without solvent or DMF. Its molecular weight is higher than water-based PU, and it has close to 100% solid content, giving it higher physical performance capabilities, especially in rebound resilience, toughness, firmness, and durability. Applications range from PPU leather, PPU film, coating, and adhesion and lamination in PU and other industries. It is solvent-free, DMF-free, a cleaner, greener option than solvent-based PU.