Differences Between Water-Based Acrylic and Polyurethane: Which is More Scratch-Resistant?
In terms of scratch resistance (mar resistance), polyurethane resin (PU) comprehensively outperforms acrylic resin (AC). Here is a detailed analysis.
I. Scratch Resistance Comparison
Characteristic | Polyurethane Resin (PU) | Acrylic Resin (AC) |
Scratch/Abrasion Resistance | ⭐️⭐️⭐️⭐️⭐️ (Excellent) • Molecules contain hard segments (providing rigidity) and soft segments (absorbing impact). • Strong hydrogen-bonded cross-linked network + microphase separation structure resists deformation from external force. | ⭐️⭐️⭐️ (Moderate) • Homogeneous linear structure; high hardness but also high brittleness. • Prone to permanent deformation or cracking when scratched. |
Principle of Scratch Resistance | Analogous to a “rubber + armor” composite structure: Elastic cushioning + rigid protection. | Analogous to “glass”: Hard but brittle, lacks resilience. |
Conclusion:
● The scratch resistance of PU far exceeds that of AC, especially in scenarios involving frequent friction or sharp object contact (e.g., packaging transport, label peeling).
● AC requires additives like nano-silica or wax powders to approach PU’s scratch resistance level, often at the cost of transparency or adhesion.
II. Extended Comparison of Key Properties
1. Properties Related to Scratch Resistance
Property | PU Advantage | AC Shortcoming |
Flexibility | ✅ High elasticity absorbs scratching stress (elongation >300%). | ❌ High brittleness, prone to cracking under scratch stress. |
Abrasion Resistance | ✅ Molecular chain resists shear forces well (suitable for high-speed printing roller friction). | ❌ Prone to powdering and flaking under long-term friction. |
Surface Hardness | ⚖️ Moderate (2H-3H), balances scratch resistance and toughness. | ⚖️ High hardness (often >3H), but excessive rigidity can cause edge chipping. |
2. Adaptability in Other Scenarios
Scenario | PU Performance | AC Performance |
Flexible Substrates | ✅ Elasticity matches films (e.g., PE/PP), resists repeated flexing and scratching. | ❌ Hard and brittle, prone to ink cracking when bent. |
Rigid Substrates | ✅ Strong adhesion, not easily peeled by scratching. | ⚠️ Requires special treatment to improve adhesion. |
III. How to Choose?
Scenarios to Prioritize PU:
● High scratch resistance requirements: Food packaging films (transportation scratches), electronic product labels (peel-proof, scratch-resistant), leather printing.
● Demand for combined properties: Requiring simultaneous scratch resistance, chemical resistance (e.g., grease wiping), and flexibility (e.g., shrink films).
Scenarios Where AC is Acceptable:
● Low cost + low-intensity scratching: Book covers, carton printing (light surface friction).
● When enhanced with additives: Scratch resistance of AC can be improved by adding silicone or nano-ceramic particles (increasing cost by 30-50%).
IV. Industry Solutions
1. Pure PU System: Used in high-end water-based inks (e.g., pharmaceutical packaging, automotive labels), withstanding >500 cycles of steel wool abrasion without damage.
2. PU/AC Hybrid System: A balanced solution: 80% AC (cost control) + 20% PU (improves scratch resistance). This reduces cost by ~40% while improving scratch resistance by 3x.
3. Modified AC System: Core-shell acrylics (hard outer shell for scratch resistance, soft inner core for toughness), though overall performance still lags behind PU.
Final Recommendations:
● For ultimate scratch resistance → Choose aliphatic water-based polyurethane (good yellowing resistance + scratch resistance + eco-friendly).
● For limited budgets → Choose acrylic + nano-SiO₂/Wax composite system (meets moderate requirements).
● To balance cost and performance → Choose PU/AC hybrid resins (optimal cost-performance ratio).
If you need specific product recommendations (e.g., BASF’s PU resins or DIC’s modified AC), please let us know your application scenario (substrate + printing method), and we can provide further tailored solutions.