The Ultimate Guide to Cellulose, Acrylic, and Silicone Leather Polishes

Leather polish agents are chemical products used for leather surface treatment, with main functions including enhancing gloss, enhancing abrasion resistance, and imparting waterproof and stain-resistant properties. Based on different chemical properties, high-gloss leather materials can be divided into five major categories: protein types, cellulose esters, polyurethanes, polyacrylates, and silicone types. This article will systematically compare and analyze various materials from the perspectives of chemical composition and physical properties.

Detailed explanation of classification

Protein-based brighteners

Chemical composition ：

      Protein brighteners are mainly represented by casein, a natural protein extracted from milk. In addition, it includes shellac, dried protein protein, keratin modifications, and more. Modern modified products improve their properties through caprolactam modification, vinyl monomer grafting copolymerization, or crosslinking with acrylic resin.

Molecular structural characteristics ：

       The casein molecule contains abundant amide groups (-CONH-), carboxyl groups (-COOH), and hydroxyl groups (-OH). These polar groups give the material excellent affinity with leather collagen fibers, enabling strong physical adsorption and hydrogen bonding.

Physical performance characteristics ：

       Gloss characteristics : Natural luster, gorgeous, and noble, with unique “glowing” properties—after mechanical polishing, the gloss can be significantly enhanced

       Film formation performance : Poor film formation, the film is relatively hard and brittle, and is prone to cracking when used alone

       Hygiene performance : Excellent breathability, comfortable and natural feel

       Water resistance : Strong hydrophilicity, poor water resistance, sticky when wet

       Aging resistance : Easily degraded by microorganisms, with limited durability

       Environmental friendliness : Traditional products require formaldehyde for fixation, which is not environmentally friendly

      Typical applications : High-end leathers that pursue natural luster, such as goat polished leather and mirror-effect leather.

Cellulose ester brighteners

Cellulose esters mainly include two major types: nitrocellulose (NC, commonly known as nitrocellulose) and cellulose acetate butyrate (CAB).

Nitrocellulose (NC) brightener

Chemical composition ：

       Obtained from cellulose through nitrate esterification, with a nitrate group (-ONO₂) in the molecular chain. To improve flexibility, plasticizing resin is usually added.

Solvent type : Divided into solvent type (organic solvent as the dispersing medium) and water-emulsion type (water as the dispersing medium).

Physical performance characteristics ：

      Gloss characteristics : High gloss, achieving a mirror-like finish; hard yet shiny

      Film formation performance : Fast film formation with high film hardness

      Abrasion resistance : Excellent resistance to dry and wet rubbing, and good wear resistance

      Weather resistance : Prone to aging and yellowing (because nitrate groups are sensitive to light and heat)

      Cold resistance : Poor quality, becomes brittle at low temperatures

      Solvent resistance : Poor

      Security : Flammable and explosive (nitrate ester bases are explosive), requiring high standards for production and storage

      Environmental friendliness : Solvent-based products cause severe VOC pollution

Cellulose acetate butyrate (CAB) brightener

Chemical composition ：

       Cellulose is obtained by esterification by mixing acetic acid and butyric acid, with the molecular chain containing acetyl and butyl groups. It must be used in conjunction with specific plasticizing resins—these plasticizers have a wide molecular weight distribution and, compared to small-molecule plasticizers, have lower migration and better durability.

Physical performance characteristics ：

       Gloss characteristics : High gloss, good light transmission

       Light resistance : Excellent, resistant to yellowing, suitable for both white and light-colored leather

       Heat resistance : Excellent, resistant to thermal aging

      Flexibility : Good, cold resistance can reach below -20°C

      Flame resistance : Fundamentally improved over nitrocellulose and less flammable

      Solubility : Good solubility in most organic solvents

      Environmental friendliness : Still mainly solvent-based, with issues with volatile organic compounds

Performance indicators ：

      Non-volatile content: 18-30%

      Viscosity: 60-150 cps

      Specific gravity: 0.88-0.98 g/cm³

Application : High-end topcoat finishes on white and light-colored leather, as well as leather products with high requirements for light resistance.

Polyurethane (PU) brighteners

Polyurethane is currently the best-performing and fastest-growing brightener type, and can be divided into two main categories: solvent-based and water-based emulsion.

Chemical composition ：

       Polyurethane is obtained by stepwise polymerizing diisocyanates and polyols, with a molecular chain containing carbamate ester groups (-NHCOO-). According to the type of diisocyanate, it can be divided into aromatic (such as MDI, TDI) and aliphatic (such as HDI, IPDI).

Molecular structural characteristics ：

      Soft section: Made of polyether or polyester polyols, providing flexibility

      Hard segment: composed of diisocyanates and chain extenders, containing dense urethane and urea bonds, providing strength and gloss

Gloss formation mechanism ：

       Research shows that high-gloss polyurethane must meet the following structural conditions: containing high refractive index groups (aryl rings, ester bonds, carbamate ester bonds, urea groups), high hard segment content (increasing strong polar bond density), and smaller latex particle size (

Physical performance characteristics ：

      Gloss characteristics : High gloss, can reach mirror finish; Aliphatic PU has better light transmittance than aromatic PU

      Film formation performance : The film layer is flexible and elastic, resistant to folding, impact, and scratching

      Abrasion resistance : Excellent

      Chemical resistance : Excellent performance in water, acid, alkali, and solvent resistance

      Weather resistance : Aliphatic PU has light resistance up to grade 4 (ISO standard), suitable for outdoor and light-colored leather; Aromatic PU tends to yellow

      Adhesion : Strong

      Tactile feel :Adjustable—hard products feel dry and smooth, soft products feel full and comfortable

      Environmental friendliness : Water-based PU is an ideal eco-friendly product with a fully water-based finish

Typical Indicators (Water-Based High-Gloss PU) ：

      Solid content: 30±1%

      Gloss: High-gloss / mirror finish

      Softness: Medium hardness

      Yellowing resistance: Level 4

Application : Widely used for topcoat finishes of various types of leather, especially automotive seat cushions, furniture leather and leather uppers, among other fields with high physical property requirements.

Polyacrylate (PA) brightener

Chemical composition ：

      It is obtained by free radical polymerization of acrylate monomers (such as methyl methacrylate, butyl acrylate, acrylonitrile, etc.). Modern products often introduce siloxane side chains through silicone modification or improve performance through graft copolymerization.

Molecular structural characteristics ：

       The polyacrylate molecular chain has a carbon-carbon single bond as the main chain and the side chain as an ester group (-COOR). The presence of ester groups gives the material a certain polarity, but overall it is a thermoplastic material.

Physical performance characteristics ：

      Gloss characteristics : Medium gloss, not as good as polyurethane or nitrocellucon

      Film formation performance : Good film-forming properties, transparent film layer

      Adhesion : Excellent adhesion to leather, which is its greatest advantage

      Light resistance : Excellent, not prone to yellowing

      Aging resistance : Okay

      Wear resistance : Average

      Impact resistance : Relatively poor

      Tactile feel : Relatively hard, not as full as polyurethane

      Flexibility : Can be adjusted through copolymerization; after modification, it can achieve both hardness and flexibility

      Environmental friendliness : Water-based emulsion matures and is environmentally friendly

Modification direction ：

      Organosilicon-modified polyacrylate is currently a research hotspot. By introducing long silicone side chains and C14-18 long carbon chains, products can be endowed with superhydrophobic properties.

Typical parameters ：

      Appearance: White emulsion

       Solid content: ≥30%

       pH value: 7-8 (anionic type)

Application : clothing leather Leather lining, and other scenarios that require moderate gloss but high adhesion. It is also often used as a modified component in combination with other brighteners.

Silicone-based brighteners

Chemical composition ：

      Silicone brighteners mainly use polysiloxane (silicone oil) as the main component, commonly polydimethylsiloxane (PDMS) and its modified substances.

Physical performance characteristics ：

      Gloss characteristics : Natural luster, soft, and oily

      Tactile characteristics : Gives leather an excellent smoothness and silky feel

      Hydrophobicity : Excellent, can impart waterproof performance to leather

      Heat resistance : Excellent, suitable for use at higher temperatures

      Brightness retention : Good, long-lasting shine

      Weather resistance : Excellent

      Film-forming : Poor film-forming properties, usually not used alone

      Application : Often used in combination with polyacrylate or polyurethane as a hand feel modifier and hydrophobic modifier.

 Other types: Moisture Curing (MC) resin

Chemical composition ：

      Moisture-curing resin is a class of prepolymers whose terminal groups contain isocyanate groups (-NCO). After spraying, NCO groups react with moisture in the air to form urea bonds and crosslink and cure.

Physical performance characteristics ：

      Gloss characteristics : Extremely high luster, with a crystal-clear appearance

      Solidification mechanism : Cures in moisture, should be left in an environment with 80% humidity and 20-30°C for 6-8 hours

      Fold resistance : Customizable, cold-resistant and fold-resistant models can withstand over 20,000 folds at -15°C

      Resistant to yellowing : Aliphatic type can reach grade 4

      Process requirements : Requires a dust-free environment and long production cycles

      Tactile feel : Can be adjusted to various styles such as oily or waxy finishes

      Application : High gloss luggage leather , glossy surface clothing leather , shoe leather, and other products that pursue the ultimate crystalline feel.

Comprehensive Comparative Analysis

Table 1: Comprehensive comparison of high-gloss leather material performance

Performance indicators	Protein-based products	Nitrocellulent (NC)	Acebutyl Cellulose (CAB)	Polyurethane (PU)	Polyacrylate (PA)	Organosilicones
Luster degree	★★★★☆	★★★★★	★★★★☆	★★★★★	★★★☆☆	★★★☆☆
Glossy type	Natural elegance	High hardness and gloss	High transparency and bright light	Adjustable	Average	Oily and lustrous
Film hardness	Slightly firm or brittle	Hard	Moderate	Adjustable	Rather hard	and does not form a film
Flexibility	★★☆☆☆	★★☆☆☆	★★★★☆	★★★★★	★★★☆☆	—
Abrasion resistance	★★★★☆	★★★★★	★★★★☆	★★★★★	★★★☆☆	★★★☆☆
Water resistance	★★☆☆☆	★★★☆☆	★★★★☆	★★★★★	★★★★☆	★★★★★
Solvent resistance	★★★☆☆	★★☆☆☆	★★★★☆	★★★★★	★★★★☆	★★★★☆
Lightfast/anti-yellowing	★★★☆☆	★☆☆☆☆	★★★★★	★★★★☆*	★★★★★	★★★★★
Weather resistance	★★☆☆☆	★☆☆☆☆	★★★★☆	★★★★★	★★★★☆	★★★★★
Adhesion	★★★★★	★★★☆☆	★★★★☆	★★★★★	★★★★★	★★☆☆☆
Tactile feel	Natural comfort	Dry and smooth	Full and comfortable	Adjustable	Rather hard	Silky smooth and oily
Environmental friendliness	★★★☆☆	★★☆☆☆	★★★☆☆	★★★★★**	★★★★★	★★★★★
Overall cost	Average	Low-mid	High	High	Low-mid	Medium to high

*Note: Aliphatic PU has excellent light resistance (Grade 4), while aromatic PU is prone to yellowing

**Note: Water-based PU is highly environmentally friendly, while solvent-based PU still has VOC issues

Table 2: Core Advantages and Limitations of Each Type

Type	Core advantages	Core limitations	Applicable scenarios
Protein-based products	It has a natural luster, feels comfortable to the touch, and is highly breathable	Poor water resistance, easy degradation, and requires formaldehyde fixation	Polished leather, mirror-finish leather
Nitro cotton	High gloss, good wear resistance, and low cost	Prone to yellowing, flammable and explosive, and poor cold resistance	Ordinary bags and shoe uppers
acebutyl cellulose	Excellent light resistance, no yellowing, and good flexibility	High cost, mainly solvent-based	White leather, light-colored leather
Polyurethane	The most balanced overall performance and strong plasticity	Some products turn yellow and have higher costs	Premium leather, car seat cushions, furniture leather
Polyacrylate	Strong adhesion, good light resistance, and low cost	Low gloss and a firm feel	clothing leather and base coating
Organosilicones	Good water repellency and silky feel	Does not form a film and cannot be used alone	Tactile modification, hydrophobic coating

Table 3: Key structural factors affecting gloss

According to the structure-performance relationship study of polyurethane, the core factors affecting coating gloss can be summarized as follows:

Influencing factors	High gloss conditions	Mechanism explanation
Refractive index of the group	High (aryl rings, ester bonds, urethane bonds, urea groups)	High refractive index→ strong reflected light→ and high gloss
Hard segment content	High	Increasing the density of strongly polar bonds → improving the refractive index
Latex particle size	Small (	Small particle size→ smooth coating surface→ high gloss
Crystallinity	Low (amorphous form)	Crystallized scattered light → reduce light transmittance and gloss
Cross-linking degree	Moderate	Cross-linking improves flatness without affecting light transmission

Selection Recommendations

Pursuing ultimate gloss and no requirements for yellowing resistance : Choose nitrocellulose brighteners, which have the highest gloss but tend to yellow easily, suitable for dark-colored leather.

Highlights for white leather and light-colored leather : Acebutyl cellulose (CAB) or aliphatic waterborne polyurethane are the preferred choices, with excellent light resistance.

High comprehensive performance requirements (bend resistance, wear resistance, weather resistance) : Water-based polyurethane is chosen, offering the best overall performance and good environmental friendliness, with a fully water-based coating.

Adhesion comes first, gloss secondary : Polyacrylic is chosen for the strongest bonding to leather, suitable for base or middle layer finishing.

Pursuing a natural, luxurious sheen : Selected modified casein types, offering unique lighting performance.

Ultimate crystal transparency : Moisture-curing (MC) resin is chosen for optimal light transmission, but process conditions must be carefully considered.

Feel comes first : Choose silicone blended products for a silky, oily feel.