Comprehensive Performance Analysis of Polyurethane Coating Films: Soft/Hard Segment Structure, Microphase Separation, Crosslinking and Curing, and Selection of Representative Chemicals

Introduction

The advantage of polyurethane (PU) coating films does not lie in achieving an extremely high value in a single property, but in their ability to achieve a well-balanced combination of hardness, flexibility, abrasion resistance, and chemical resistance through molecular structure design and curing network design. This performance balance mainly comes from the following structural factors:

Structural factor	Main function	Points to note
Soft segments	Provide flexibility, elasticity, low-temperature performance, and energy absorption capacity	If the content is too high or the segments are too soft, hardness, blocking resistance, and solvent resistance may decrease
Hard segments	Provide hardness, strength, heat resistance, and surface deformation resistance	If the content is too high or the segments are too rigid, the coating film may become brittle
Microphase separation	Allows soft segments and hard segments to perform their respective functions, achieving a balance between strength and toughness	Either insufficient or excessive microphase separation may affect overall performance
Hydrogen bonding and polar interactions	Enhance intermolecular interactions and improve strength, hardness, and abrasion resistance	Excessively strong interactions may restrict segmental mobility
Crosslinked network	Improves coating film compactness, solvent resistance, and chemical resistance	Excessive crosslinking may reduce flexibility and impact resistance
NCO/OH ratio	Affects curing completeness, hard segment structure, hydrogen bonding, and network compactness	An unreasonable ratio may lead to insufficient curing, embrittlement, or side reactions

Polyurethane is usually composed of flexible soft segments and relatively rigid hard segments. The soft segments mainly come from long-chain polyols and provide the material with flexibility, elasticity, and low-temperature performance. The hard segments mainly come from isocyanates, chain extenders, or short-chain polyols, and provide the material with strength, rigidity, and heat resistance. Together, the soft and hard segments form a certain degree of microphase-separated structure, giving polyurethane a broad range of property adjustability.

1. The Performance Balance of Polyurethane Comes from Soft and Hard Segments

Polyurethane coating films can combine hardness and flexibility because they are not fully homogeneous single-segment structures, but are composed of both flexible soft segments and rigid hard segments.

Structural unit	Main source	Main function
Soft segments	Flexible chain segments formed from long-chain polyols	Provide flexibility, elasticity, low-temperature performance, and deformation recovery
Hard segments	Rigid chain segments formed from isocyanates, chain extenders, or short-chain components	Provide hardness, strength, abrasion resistance, heat resistance, and dimensional stability

Soft segments and hard segments play different roles. Soft segments allow the coating film to undergo a certain degree of deformation during bending, impact, or thermal expansion and contraction. Hard segments, on the other hand, restrict excessive slippage of molecular chains, allowing the coating film to maintain strength, surface hardness, and wear resistance. The overall performance balance of polyurethane coating films is achieved through the proper matching of soft segments, hard segments, hydrogen bonding, and the crosslinked network.

2. Soft Segments Provide Flexibility, Elasticity, and Energy Absorption Capacity

Soft segments usually come from relatively flexible, higher-molecular-weight polyol chain segments. Their main function is to improve molecular chain mobility, making the coating film less likely to crack during bending, impact, temperature changes, or slight deformation.

Soft segment characteristic	Effect on coating film performance
Higher soft segment content	Flexibility and elasticity improve, but hardness, blocking resistance, and solvent resistance may decrease
Longer soft segment chains	Low-temperature flexibility and elongation usually improve
Stronger soft segment mobility	Impact resistance, bending adaptability, and deformation recovery improve
Excessive or overly soft soft segments	The coating film may show insufficient hardness, reduced indentation resistance, and decreased stain resistance

More soft segments are not always better. For coatings, the value of soft segments lies in providing the necessary flexibility and energy absorption capacity, rather than simply pursuing high elongation.

Flexibility is also related to the glass transition temperature (Tg). When Tg is lower, chain segments are more mobile at room temperature, and the coating film is usually more flexible. When Tg is higher, the coating film becomes harder, but flexibility and low-temperature crack resistance may decrease.

In addition, different soft segment types also affect chemical resistance and durability. For example, polyether, polyester, and polycarbonate soft segments differ in hydrolysis resistance, oil resistance, solvent resistance, oxidation resistance, and low-temperature flexibility. Therefore, soft segment content alone cannot explain all properties; the chemical structure of the soft segments also needs to be considered.

3. Hard Segments, Hydrogen Bonding, and Crosslinked Networks Jointly Contribute to Hardness and Strength

Hard segments are usually formed by the reaction of isocyanates with short-chain chain extenders or short-chain polyols. Hard segment structures are more rigid, have stronger intermolecular interactions, and tend to form locally aggregated regions. They are important sources of hardness, strength, and surface deformation resistance in polyurethane coating films. The hardness of polyurethane coating films mainly comes from three aspects:

Source of hardness	Mechanism
Rigid hard segments	Restrict molecular chain movement and improve resistance to surface indentation and scratching
Crosslinked network	Fixes molecular chains within a three-dimensional network, improving deformation resistance
Hydrogen bonding and polar interactions	Enhance intermolecular bonding strength and improve strength and hard segment aggregation

Hard segments can be understood as the “supporting structure” in the coating film. They restrict the free movement of molecular chains, making the coating film less prone to scratching, indentation, or wear. However, when the hard segment content is too high or hard segment aggregation is too strong, the coating film may become brittle. For coatings, excessively high hardness without sufficient flexibility may lead to bending cracks, impact cracks, edge chipping, or adhesion failure.

Therefore, hardness is not an isolated property. The design focus of polyurethane coating films is not simply to increase hardness, but to match hardness, toughness, and adhesion appropriately.

4. Microphase Separation Enables Polyurethane to Combine Strength and Toughness

The soft and hard segments in polyurethane are usually not completely thermodynamically compatible, and they tend to form a certain degree of microphase separation. Microphase separation means that soft segments and hard segments form relatively enriched regions at the nanoscale or microscopic scale, rather than being completely uniformly mixed. This structure is very important for polyurethane coating films.

Microphase structure	Effect on performance
Soft segment-rich regions	Provide flexibility, elasticity, and energy absorption capacity
Hard segment-rich regions	Provide hardness, strength, and deformation resistance
Soft/hard segment interfaces	Affect stress transfer, toughness, and abrasion resistance
Moderate microphase separation	Helps balance strength and toughness
Insufficient microphase separation	The supporting effect of hard segments is inadequate, and strength and abrasion resistance may decrease
Excessive microphase separation	The structure becomes uneven, and the coating film may show embrittlement or local stress concentration

For coating films, the significance of microphase separation lies in this: hard segment regions provide support, while soft segment regions absorb deformation energy. Together, they allow polyurethane to resist rapid cracking under friction, impact, or bending, unlike highly brittle coating films, while also avoiding the easy wear or indentation seen in overly soft coating films.

However, stronger microphase separation is not always better. Its effect depends on the soft/hard segment structure, hard segment content, hydrogen bonding, crosslinking density, solvent evaporation process, and curing conditions. Moderate and stable microphase separation is more beneficial for overall performance.

5. Hydrogen Bonding Is an Important Physical Reinforcement Mechanism in Polyurethane

The urethane bonds in polyurethane structures contain carbonyl groups and N—H groups, which can form hydrogen bonds. If amine chain extenders are present in the system, or if urea structures are formed after isocyanates react with water, urea bonds may also provide stronger hydrogen bonding. Hydrogen bonds are not chemical crosslinks, but they can significantly enhance interactions between molecular chains. The effects of hydrogen bonding on coating film performance mainly include:

Function	Effect on performance
Enhancing intermolecular interactions	Improves tensile strength, hardness, and surface deformation resistance
Promoting hard segment aggregation	Helps form hard segment-rich regions
Affecting microphase separation	Changes the compatibility and interfacial structure between soft and hard segments
Participating in energy dissipation	Helps improve toughness and abrasion resistance

Hydrogen bonding can be understood as a form of “reversible physical reinforcement.” Unlike chemical crosslinking, it does not permanently fix molecular chains, but it can break, reform, and dissipate energy during deformation. It therefore contributes significantly to strength, toughness, and abrasion resistance.

It should be noted that not all polyurethane systems contain large amounts of urea bonds. In polyurethane systems formed by curing ordinary hydroxyl resins with isocyanates, the main structures are urethane bonds. Urea bonds are more commonly found in systems involving water-containing reactions, amine chain extension, or polyurea/polyurethane-urea structures.

6. Crosslinking Density Determines the Compactness of the Coating Film Network

Crosslinking density refers to the number of crosslinking points per unit volume of the coating film. The higher the crosslinking density, the more difficult it is for molecular chains to move freely. The coating film usually shows higher hardness, better solvent resistance, and stronger chemical resistance. However, higher crosslinking density is not always better.

Crosslinking density state	Coating film performance
Low crosslinking density	Better flexibility, but hardness, solvent resistance, and chemical resistance may be insufficient
Moderate crosslinking density	Hardness, flexibility, abrasion resistance, and chemical resistance are easier to balance
Relatively high crosslinking density	Hardness and chemical resistance improve, but the coating film may become brittle
Excessively high crosslinking density	Segmental mobility is restricted, and impact resistance, bendability, and recoatability may decrease

The effect of crosslinking density on polyurethane coating films can be summarized as follows:

Insufficient crosslinking → incomplete network → prone to swelling and softening, with inadequate chemical resistance.

Moderate crosslinking → compact network while still retaining some segmental mobility → good overall performance.

Excessive crosslinking → overly rigid network and restricted segmental mobility → reduced flexibility and impact resistance.

Crosslinking density is one of the core variables in regulating the performance of polyurethane coating films. It determines whether the coating film is more flexible, harder, more chemically resistant, or capable of achieving a balance among multiple properties.

7. The NCO/OH Ratio Affects Curing Completeness and Network Structure

The NCO/OH ratio is the equivalent ratio of isocyanate groups (NCO, —N=C=O) to hydroxyl groups (OH, —OH). It is an important formulation parameter in reactive polyurethane systems.

The NCO/OH ratio mainly affects three aspects:

1. Whether the curing reaction is sufficient;

2. Whether the crosslinked network is complete;

3. Whether coating film hardness, flexibility, and chemical resistance are balanced.

NCO/OH ratio state	Possible result
Low NCO/OH ratio	Insufficient isocyanate; crosslinking may be incomplete, and solvent resistance and chemical resistance decrease
NCO/OH ratio close to the reasonable design value	The reaction is relatively complete, and coating film properties are easier to balance
High NCO/OH ratio	Hard segment content, rigidity, or network compactness may increase
Excessively high NCO/OH ratio	Residual NCO, side reactions, bubbles, embrittlement, or reduced flexibility may occur

When the functionality of the isocyanate, the functionality of the polyol, and the curing conditions are appropriate, increasing the NCO/OH equivalent ratio usually increases hard segment structure, hydrogen bonding, or network compactness, thereby increasing coating film rigidity, Tg, and solvent resistance.

However, this rule should not be treated as absolute. The actual effect of the NCO/OH ratio depends on system composition, functionality, catalyst, humidity, curing temperature, reaction completeness, and whether side reactions occur. If the ratio is too low, the network may be incomplete. If the ratio is too high, residual NCO may appear; in the presence of moisture, catalyst, heating, or participation of urethane/urea bonds, side structures such as urea, allophanate, biuret, or isocyanurate may also be promoted, leading to embrittlement, bubbles, or storage stability issues.

Therefore, the NCO/OH ratio is not merely a calculated formulation ratio. It is also an important tool for controlling curing completeness, hard segment structure, and the crosslinked network of the coating film.

8. Abrasion Resistance Comes from Surface Deformation Resistance and Internal Energy Dissipation

The abrasion resistance of polyurethane coating films is not determined solely by hardness. Higher hardness can improve resistance to surface scratching and indentation, but if the coating film is too brittle, repeated friction, impact, or local loading may instead cause microcracks, peeling, or chalking. Abrasion resistance usually comes from the combined effect of the following factors:

Influencing factor	Effect on abrasion resistance
Hard segment structure	Improves surface deformation resistance, scratch resistance, and indentation resistance
Crosslinked network	Improves swelling resistance and structural stability
Soft segment toughness	Absorbs energy generated by friction and impact
Hydrogen bonding	Enhances intermolecular bonding and participates in energy dissipation
Stability of microphase structure	Reduces structural damage under repeated stress
Coating film compactness	Reduces medium penetration and wear propagation

Abrasion-resistant polyurethane coating films are usually not “the harder, the more wear-resistant.” Instead, hard segment support, crosslinked network constraint, soft segment energy dissipation, and hydrogen bond reinforcement need to work together.

In simple terms, hard segments resist surface deformation, soft segments absorb frictional energy, the crosslinked network maintains structural stability, and hydrogen bonds enhance intermolecular bonding. This combination gives polyurethane good overall performance in abrasion-resistant applications.

9. Chemical Resistance Comes from a Compact Network, Complete Curing, and Low Swelling Capacity

The chemical resistance of polyurethane coating films is mainly related to crosslinking density, curing completeness, coating film compactness, chain segment polarity, and the swelling resistance of soft segments. When the coating film network is relatively complete, there are more crosslinking points, and molecular chain movement is restricted, solvents or chemical media have more difficulty entering the interior of the coating film. The coating film is therefore less likely to undergo swelling, softening, gloss loss, or adhesion reduction.

Structural state	Chemical resistance performance
Insufficient crosslinking	Easily swollen or softened by solvents
Incomplete curing	Water resistance, solvent resistance, and chemical resistance decrease
Compact network structure	Penetration of chemical media becomes more difficult
Higher crosslinking density	Solvent resistance and chemical resistance usually improve
Excessive crosslinking	Chemical resistance may improve, but toughness and impact resistance may decrease
Easily swollen soft segments	Solvent resistance may be limited

The chemical resistance of polyurethane coating films is usually associated with relatively high crosslinking density, but high crosslinking should not be pursued alone. Excessive crosslinking may embrittle the coating film and reduce impact resistance and crack resistance.

In addition, the type of soft segment also significantly affects chemical resistance. For example, different polyether, polyester, polycarbonate, or bio-based polyol structures differ in hydrolysis resistance, oil resistance, solvent resistance, oxidation resistance, and low-temperature flexibility. Therefore, chemical resistance should be evaluated by considering crosslinking density, curing completeness, soft segment structure, and coating film compactness together.

10. Adhesion and Crack Resistance Affect Actual Durability

Whether a coating film can truly deliver these properties is also related to adhesion and internal stress. Polyurethane coating films contain many polar structures, which are beneficial for forming interactions with the substrate or primer. Appropriate flexibility can also relieve stress concentration caused by curing shrinkage, temperature changes, and mechanical impact.

Influencing factor	Effect on adhesion and crack resistance
Polar groups	Help form interactions with the substrate
Flexible soft segments	Relieve substrate deformation and thermal stress
Crosslinked network	Provides overall strength and dimensional stability
Lower internal stress	Reduces the risk of cracking, edge lifting, and delamination
Excessively high hardness or excessive crosslinking	May cause stress concentration and reduce impact resistance

The actual durability of polyurethane coating films is not determined only by surface hardness. The ability to disperse stress, absorb energy, and maintain network stability is an important source of long-term performance.

11. Trade-Offs Exist Among Different Properties

Polyurethane can balance multiple properties, but this does not mean that all properties can be improved indefinitely at the same time. Trade-offs often exist among different properties.

Adjustment direction	Possible positive effect	Possible negative effect
Increasing hard segment content	Hardness, strength, abrasion resistance, and heat resistance improve	Flexibility decreases and brittleness increases
Increasing soft segment content	Flexibility, elasticity, and low-temperature performance improve	Hardness, blocking resistance, and solvent resistance decrease
Increasing crosslinking density	Chemical resistance, solvent resistance, and hardness improve	Impact resistance, bendability, and recoatability decrease
Increasing the NCO/OH ratio	Rigidity, hard segment effect, or network compactness may increase	Risks of side reactions, residual NCO, and brittleness increase
Enhancing microphase separation	Strength and toughness may improve	Excessive phase separation may cause structural nonuniformity or embrittlement
Lowering Tg	Flexibility and low-temperature performance improve	Hardness, blocking resistance, and heat resistance may decrease

The performance advantages of polyurethane come from the reasonable combination of these variables. For coating formulations, the key is not to maximize a single property, but to determine the priority among hardness, flexibility, abrasion resistance, and chemical resistance based on actual application requirements. For example:

1. Flooring coatings or abrasion-resistant topcoats place greater emphasis on hardness, abrasion resistance, chemical resistance, and stain resistance;

2. Coatings for flexible substrates place greater emphasis on flexibility, adhesion, and crack resistance;

3. Outdoor coatings also need to consider weather resistance, hydrolysis resistance, and yellowing resistance;

4. Industrial protective coatings need to balance compactness, media resistance, adhesion, and impact resistance.

12. Classification and Applications of Representative Chemicals Related to Polyurethane Hardness, Flexibility, Abrasion Resistance, and Chemical Resistance （Tables 1–4）

Table 1. Isocyanate Hard-Segment Monomers and Crosslinking/Curing Components

Category	CAS No.	Aladdin Cat. No.	Name	Specification or Purity	Product Features and Applications
Aliphatic biuret-type polyisocyanate crosslinker	4035-89-6	T770979	Hexamethylene diisocyanate biuret	NCO content: 21–22.5%	A multifunctional isocyanate structure used to increase the crosslinking density of polyurethane. Suitable for curing systems in coatings, elastomers, and adhesives, and relevant to studies on surface hardness, abrasion resistance, solvent resistance, and weatherability.
Alicyclic diisocyanate hard-segment monomer	4098-71-9	I109582	Isophorone diisocyanate, mixture of isomers (IPDI)	≥99%	The alicyclic structure provides rigid hard segments while maintaining segmental mobility. Suitable for weather-resistant polyurethane coatings, waterborne polyurethane, and elastomers, and relevant to studies on hardness, flexibility retention, yellowing resistance, and resistance to chemical media.
Aromatic diisocyanate hard-segment monomer	101-68-8	M106783	4,4'-Methylenebis(phenyl isocyanate) (MDI)	≥98%	The aromatic rigid structure facilitates the formation of highly cohesive hard segments. Suitable for thermoplastic polyurethanes, cast elastomers, foams, and adhesives, and relevant to studies on hardness, tensile strength, abrasion resistance, and microphase separation.
Isocyanurate-type trifunctional isocyanate crosslinker	3779-63-3	H694586	1,3,5-Tris(6-isocyanatohexyl)-1,3,5-triazine-2,4,6-trione	≥95%	A trifunctional isocyanate structure used to construct dense crosslinked networks. Suitable for high-durability polyurethane coatings, sealants, and elastomers, and relevant to studies on resistance to chemical media, heat resistance, abrasion resistance, and surface hardness.
Hydrogenated alicyclic diisocyanate hard-segment monomer	5124-30-1	D155475	Dicyclohexylmethane-4,4'-diisocyanate, mixture of isomers (HMDI)	≥90% (GC)	A saturated alicyclic structure used to build weather-resistant polyurethane hard segments. Suitable for elastomers, clear coatings, and adhesives, and relevant to studies on flexibility retention, low yellowing, hydrolysis resistance, and resistance to chemical media.

Table 2. Soft-Segment Polyols, Hydrophilic Segments, and Bio-Based Flexible Components

Category	CAS No.	Aladdin Cat. No.	Name	Specification or Purity	Product Features and Applications
Polyoxyethylene hydrophilic modified segment	25322-68-3	P615493	Polyethylene oxide	Viscosity: 65–115 cps	A hydrophilic polyether segment used to regulate water uptake, ion transport, and segmental motion in polyurethane. Suitable for waterborne polyurethane, hydrophilic coatings, hydrogels, and biomaterial interface studies.
Polypropylene glycol-type polyether soft-segment diol	25322-69-4	P103212	Polypropylene glycol (PPG)	Average molecular weight 4000	A polyether soft segment used to provide flexibility and rebound resilience. Suitable for polyurethane foams, elastomers, sealants, and coatings, and relevant to studies on low-temperature flexibility, hydrolysis resistance, and soft/hard segment phase separation.
Polycaprolactone-type polyester soft-segment diol	36890-68-3	P478032	Polycaprolactone diol	Average Mn 10000	A crystalline polyester soft segment used to improve mechanical support and abrasion resistance in polyurethane elastomers. Suitable for thermoplastic polyurethanes, elastic fibers, biodegradable materials, and coating research.
Polytetrahydrofuran-type high-resilience polyether soft-segment diol	25190-06-1	P432410	Polytetrahydrofuran (PTHF)	Average Mn ~2900	A flexible polyether backbone used to provide elastic recovery and low-temperature flexibility. Suitable for thermoplastic polyurethanes, elastomers, and fiber materials, and relevant to studies on abrasion resistance, dynamic fatigue, and hydrolytic stability.
Castor oil-based polyhydroxy bio-based soft-segment raw material	8001-79-4	C434218	Castor oil	European Pharmacopoeia (Ph.Eur)	A naturally hydroxyl-containing oil used for bio-based polyurethane soft segments and crosslinked structure design. Suitable for foams, coatings, elastomers, and adhesives, and relevant to studies on flexibility, hydrophobicity, crosslinking density, and resistance to chemical media.

Table 3. Chain Extenders, Crosslinkers, and Curing-Control Components

Category	CAS No.	Aladdin Cat. No.	Name	Specification or Purity	Product Features and Applications
Butanediol-type linear diol chain extender	110-63-4	B1508458	1,4-Butanediol (BDO)	Anhydrous, ≥99%	A short-chain diol used to extend hard segments and regulate microphase separation. Suitable for thermoplastic polyurethanes and cast elastomers, and relevant to studies on hardness, tensile strength, rebound resilience, and abrasion resistance.
Glycerol-type trifunctional polyol crosslinker	56-81-5	G755728	Glycerol	Anhydrous, UltraBio™, molecular biology grade, ≥99.5% (GC)	A trihydroxy structure used to introduce branching and crosslinking points. Suitable for polyurethane foams, elastomers, and coatings, and relevant to studies on crosslinking density, dimensional stability, hardness, and solvent resistance.
Ethylene glycol-type short-chain diol chain extender	107-21-1	E119700	Ethylene glycol	Anhydrous, ≥99.8%	A small-molecule diol used to build compact hard segments or prepare polyester polyols. Suitable for regulating polyurethane hard-segment structures, and relevant to studies on modulus, hardness, segmental regularity, and processing rheology.
Ethylenediamine-type diamine chain extender	107-15-3	E431349	Ethylenediamine (regulated explosive precursor)	Suitable for synthesis	A diamine used to form urea hard segments and rapid chain-extension structures. Suitable for polyurethane-urea, elastomer, and coating systems, and relevant to studies on hydrogen-bond density, hardness, abrasion resistance, and solvent resistance.
Diethanolamine-type amino alcohol reactive modifier	111-42-2	D431475	Diethanolamine (DEA)	Suitable for analysis, premium grade	Contains both hydroxyl and amino groups and is used for polyurethane chain extension, branching, and polar modification. Suitable for waterborne polyurethane, adhesives, and coatings, and relevant to studies on adhesion, hydrophilicity, curing reactions, and resistance to chemical media.
Diethylene glycol-type ether-bond-containing flexible diol chain extender	111-46-6	D476199	Diethylene glycol	UltraBio™, ultrapure grade, ≥99% (GC)	An ether-bond-containing diol used to regulate hard-segment spacing and segmental flexibility. Suitable for polyurethane elastomers, coatings, and polyester polyol synthesis, and relevant to studies on low-temperature flexibility, processing viscosity, and mechanical balance.
Hexanediol-type long-chain aliphatic diol chain extender	629-11-8	H103708	1,6-Hexanediol	≥98%	A linear aliphatic diol used to build flexible and ordered chain-extended structures. Suitable for polyurethane elastomers, coatings, and polyester polyols, and relevant to studies on crystallinity, hydrolysis resistance, flexibility, and abrasion resistance.
Pentaerythritol-type tetrafunctional polyol crosslinker	115-77-5	P103696	Pentaerythritol (regulated explosive precursor)	AR, ≥98%	A tetrahydroxy structure used to form highly branched or crosslinked networks. Suitable for polyurethane resins, rigid foams, and durable coatings, and relevant to studies on surface hardness, heat resistance, dimensional stability, and resistance to chemical media.
Cyclohexanedimethanol-type alicyclic diol chain extender	105-08-8	C105684	1,4-Cyclohexanedimethanol (CHDM)	≥99%, mixture of cis and trans	An alicyclic structure used to introduce rigidity and weatherability. Suitable for polyurethane coatings, elastomers, and polyester polyol synthesis, and relevant to studies on hardness, flexibility retention, hydrolytic stability, and resistance to chemical media.
Isophorone diamine-type alicyclic diamine curing agent	2855-13-2	A104545	Isophorone diamine, cis/trans mixture (IPDA)	≥99%	An alicyclic diamine used to construct polyurethane-urea and polyurea structures. Suitable for elastomers, protective coatings, and sealants, and relevant to studies on rapid curing, hardness, toughness, abrasion resistance, and resistance to chemical media.
Neopentyl glycol-type sterically hindered diol chain extender	126-30-7	N103689	Neopentyl glycol (NPG)	≥99%	A sterically hindered diol used to improve hydrolytic stability around ester bonds in polyurethane. Suitable for polyurethane coatings, elastomers, and polyester polyols, and relevant to studies on flexibility, hardness, weatherability, and resistance to chemical media.
Trimethylolpropane-type trifunctional polyol crosslinker	77-99-6	T110597	Trimethylolpropane (TMP)	≥98%	A trihydroxy structure used to regulate branching and crosslinking density. Suitable for polyurethane coatings, adhesives, elastomers, and foams, and relevant to studies on abrasion resistance, solvent resistance, surface hardness, and dimensional stability.

Table 4. Functional Fillers, Abrasion-Resistant Modifiers, and Reference Resins

Category	CAS No.	Aladdin Cat. No.	Name	Specification or Purity	Product Features and Applications
Polyolefin reference resin for chemical resistance	9002-88-4	P434354	Polyethylene (PE)	Medium density, melt index 3.5 g/10 min (190°C/2.16 kg)	A nonpolar polyolefin material used for reference comparison and blend-compatibility studies in polyurethane systems. Suitable for comparing chemical-media resistance, flexibility, friction and wear, and processing flow behavior.
Polytetrafluoroethylene-type low-friction abrasion-resistant modifying filler	9002-84-0	P434335	Polytetrafluoroethylene (PTFE)	Powder, particle size ≤12 μm	Fine-particle PTFE powder is used to reduce surface friction in polyurethane systems and improve slip, non-stick properties, and abrasion resistance. Suitable for abrasion-resistant coatings, composite elastomers, sealants, and release-modification studies, and relevant to friction and wear, resistance to chemical media, and dispersion compatibility.
Silica-type inorganic reinforcing filler	7631-86-9	S104604	Silicon dioxide	≥99.9% metals basis	Inorganic silica is used for reinforcement of polyurethane matrices and regulation of surface scratch resistance. Suitable for composite coatings, elastomers, and adhesives, and relevant to studies on hardness, abrasion resistance, thermal stability, and barrier properties.
Alumina-type ceramic abrasion-resistant reinforcing filler	1344-28-1	A420214	Aluminum oxide	≥99% metals basis	A high-hardness ceramic filler used for abrasion-resistant and scratch-resistant modification of polyurethane composites. Suitable for protective coatings, abrasion-resistant elastomers, and thermally conductive composite systems, and relevant to studies on surface hardness, dimensional stability, and resistance to chemical media.
Fumed silica-type rheology-control and reinforcing filler	112945-52-5	S491206	Fumed silica	≥99%	High-specific-surface-area silica is used for thixotropy, thickening, anti-settling, and reinforcement in polyurethane systems. Suitable for coatings, sealants, and adhesives, and relevant to studies on rheology control, abrasion resistance, surface hardness, and storage stability.

Note: The above products are representative Aladdin products. For more product specifications, please search by “product name/CAS/catalog number” on the Aladdin official website.

References

[1] Wu, S.; Ma, S.; Zhang, Q.; Yang, C. A comprehensive review of polyurethane: Properties, applications and future perspectives. Polymer, 2025, 327, 128361.

[2] Fan, T.; Hou, G.; Zhang, Z.; Ma, J.; Dong, F.; Chen, L.; An, Y.; Zhao, X.; Zhou, H.; Chen, J. Symmetric isocyanate-driven polyurethane coatings with pronounced microphase separation: Modulating hard-segment aggregation and cavitation erosion resistance mechanisms via crosslinking density. Polymer Degradation and Stability, 2026, 243, 111739.

[3] Palle, I.; Lodin, V.; Mohd Yunus, A. A.; Lee, S. H.; Md Tahir, P.; Hori, N.; Antov, P.; Takemura, A. Effects of NCO/OH Ratios on Bio-Based Polyurethane Film Properties Made from Acacia mangium Liquefied Wood. Polymers, 2023, 15(5), 1154.

[4] 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. Progress in Organic Coatings, 2018, 115, 41–48.

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