NDI Polyurethane Coated Wheels

With the rapid development of modern industry, an increasing number of enterprises have a growing demand for polyurethane covered wheels with high wear resistance, high load capacity, high heat resistance and long service life. However, traditional polyurethane materials (such as toluene diisocyanate (TDI) series and methylene diphenyl diisocyanate (MDI) series) can hardly fully meet the actual requirements of enterprises under high-demand working conditions such as high wear resistance and heavy load. Frequent wear and replacement of polyurethane covered wheels also seriously affect production efficiency and user experience.
Against this background, NDI-based polyurethane covered wheels have gradually emerged and demonstrated remarkable unique advantages, becoming the ideal choice for special high-demand working conditions with heavy load and high wear resistance requirements.
NDI polyurethane uses 1,5-naphthalene diisocyanate (NDI) as the main raw material. Compared with the double benzene ring structure of MDI and the single benzene ring structure of TDI (as shown in the molecular structure diagram), its unique naphthalene ring molecular structure endows the polyurethane material with higher rigidity. As a result, polyurethane covered wheels made of NDI polyurethane feature superior wear resistance and mechanical properties, which can effectively meet the application requirements of heavy-duty forklifts, monorail crane wheels and other equipment under high-load and high-wear-resistance environments.

 

                Mechanical Properties Comparison of TDI Polyurethane, MDI Polyurethane and NDI Polyurethane①

 

Property	Test Standard	TDI/Ether/MBoca			MDI/Ether/BD			NDI/Ether/BD
		Prepolymer NCO%	-	3.4	4.1	6.3	6.6	8.2	9.0	2.5	4.6	6.0
Shore A/Shore D Hardness	DIN 53505	85/32	89/33	93/43	83/32	89/40	94/45	84/32	92/40	95/45
100% Tensile Modulus (Mpa)	DIN 53504	4.6	5.8	9.1	5.1	6.6	10.0	4.8	9.0	11.1
300% Tensile Modulus (Mpa)	DIN 53504	8.3	11.3	28.4	11.8	12.2	20.8	7.9	13.1	15.0
Tensile Strength (Mpa)	DIN 53504	34.9	36.9	46.0	59.3	55.9	57.1	45.8	45.0	37.9
Elongation at Break (%)	DIN 53504	520	454	354	611	570	554	654	658	632
Tear Strength (KN/m)	DIN 53515	17	26	36	54	58	87	33	58	65
Rebound Resilience (%)	DIN 53512	62	53	36	44	40	46	60	59	57
Abrasion Loss (mg)	DIN 53754	55	72	115	76	82	89	35	61	75
Compression Set	ASTM D395	-
70h/23℃ (%)		-	11	14	16	11	17	23	9	12	13
24h/70℃ (%)		-	19	24	24	19	26	20	15	17	18

①Data source: Paper published by Bayer and Mobay: Comparison of the Dynamic Properties of Solid Polyurethane Elastomers, Journal of Elastomers and Plastics Vol.23-October 1991

Compared with TDI-based and MDI-based polyurethanes, NDI-based polyurethane features lower abrasion loss and lower permanent compression set (as shown in the table). In application environments with high load and high wear resistance requirements, NDI-based polyurethane demonstrates significantly more prominent advantages. This means that when users require polyurethane materials with extremely high wear resistance and excellent mechanical properties, NDI-based polyurethane will be the optimal choice for customers.
In terms of service life, NDI-based polyurethane covered wheels also have a significantly longer service life than TDI-based and MDI-based polyurethane covered wheels under identical application conditions. According to test data released by Covestro AG (a world-class enterprise based in Germany) (as shown in the figure), under the same application scenario, the continuous service life of NDI-based polyurethane covered wheels is approximately 32.4 percentage points higher than that of MDI-based polyurethane covered wheels and about 46.7 percentage points higher than that of TDI-based polyurethane covered wheels, while also exhibiting higher load-bearing capacity.

Furthermore, in the continuous obstacle-passing tests of a similar product—NDI-based and MDI-based polyurethane covered wheels—conducted by our company (as shown in the figure), the number of obstacle-passing cycles of NDI-based polyurethane covered wheels exceeded that of MDI-based ones by more than 8,000 cycles.
All these data fully demonstrate that the excellent load-bearing capacity, high mechanical properties and long service life of NDI-based polyurethane covered wheels make them undoubtedly the optimal choice for special working conditions such as high load and high wear resistance.

Test chart of obstacle crossing for NDI-based polyurethane wheels and MDI-based polyurethane wheels
Test speed: 4km/h; Load: 2.8T; Obstacle strip size: 9×100mm; Obstacle strip placement angle: 45°; Wheel size: 285×100mm