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Evolution In time of brake pads formulations

The following figure summarizes an approximate time table of the changes in formulations over the last 40 years in the original equipment market All of them share the same original formulation type based on asbestos. Since asbestos was banned in the 80’s, most car manufacturers requested friction material producers not to use this raw material anymore as it is known to be hazardous for human health A second step towards formulation modification is the reduction on car weight and the increased quality of the engine producing lower noise and vibrations.

Friction - Evolution In time of brake pads formulations

APPLICATION IN BRAKES PADS

Based on the original basic formula, the adding proportion of resin, reinforced fiber and filler is adjusted according to the adding amount of Gypsum fiber. The recommended proportion is 7-15% (7-15% of the overall formula weight).

“NP”Gypsum Fiber Working with Fibrous Potassium Titanate/Titanate Flakey Material

Our customers have undergone many experiments and market verification in brake pads formulation. Gypsum fiber can be combined with Fibrous potassium titanate. That is, the pads made of gypsum fiber and Fibrous potassium titanate still has excellent comprehensive performances, reducing the cost and improving brake pads market competitiveness.

Product Name: Gypsum Fiber Item no.:NP-HF02 HS CODE:68099000 Applications: The special material for formulation of Middle and high-value brake pads.

 

The following figure summarizes an approximate time table of the changes in formulations over the last 40 years in the original equipment market All of them share the same original formulation type based on asbestos. Since asbestos was banned in the 80’s, most car manufacturers requested friction material producers not to use this raw material anymore as it is known to be hazardous for human health A second step towards formulation modification is the reduction on car weight and the increased quality of the engine producing lower noise and vibrations.

Comparative test data in the NAO formula of passenger car disc

Conclusion: The wear result of brake pad: the wear loss of F3>F1>F2, wear loss of F2 formula is the lowest, the wear of F1 formula is less than F3, and Dynamometer test indicates the performance of NHV is improved effectively when braking.

In conclusion: It is suggested that the application of gypsum fiber, in the medium and high end car disc pads NAO formula and the low steel (low steel) formula of commercial car disc pads, with Holland fiber performs in excellence.

Mechanism of reinforcement and toughness

Tiny NP@ Gypsum Fiber shape act as reinforcing and wear-resistant filler. This filler will improve the poor area of coarse fibers.

  • Material A0, reference OE material containing Potassium Titanate
  • Material A1, partial substitution of Potassium Titanate with NP Fibers (8% weight)
  • Material A2, partial substitution of Potassium Titanate with NP Fibers (16% weight)
  • Material A3, partial substitution of Potassium Titanate with a combination of NP Fibers and Mineral Fibres (8% weight each material)
  • Material A4, partial substitution of Potassium Titanate with a combination of NP Fibers and Mineral Fibres (13% weight NP gypsum Fiber , 6% weight mineral fibres)

Processing:

  • Mixing in high speed in a Loedige mixer in 2 steps.
  • Hot molding (direct fill) at 165 Celsius for 5 minutes (5 degas, one every minute).
  • Curing at 220 Celsius for 13 hours with a temperature growth shown in figure 29.
  • Underlayer was used to adjust pad thickness

The below Table is showing the compressibility of the produced and tested friction materials.

  • Material A0, reference OE material containing Potassium Titanate
  • Material A1, partial substitution of Potassium Titanate with NP Fibers (8% weight)
  • Material A2, partial substitution of Potassium Titanate with NP Fibers (16% weight)
  • Material A3, partial substitution of Potassium Titanate with a combination of NP Fibers and Mineral Fibres (8% weight each material)
  • Material A4, partial substitution of Potassium Titanate with a combination of NP Fibers and Mineral Fibres (13% weight NP gypsum Fiber , 6% weight mineral fibres)

When comparing materials A1 to A4 with the OE material, there are 5 main observations to see.

  • Materials A2 and A4 show the lower wear rates, both for disc and pad. Those two materials are the formulations containing the higher amount of gypsum fiber. The results could be associated to two main physical properties: the hardness of gypsum fiber is lower than the hardness of potassium titanate and mineral fibers, and the shape of the material helps to provide with reinforcement to the surface of the friction material.
  • Following the same line of analysis, material A3 shows the higher disc and pad wear. This formulation contains the higher amount of mineral fibers. Mineral fibers have also the higher hardness among the three compared materials.
  • From a friction stability perspective, the most stable materials are A0 and A4, providing with a high fade resistance and a fast recovery.
  • The material A2 with the lower friction coefficient, too low, is the material containing the lower abrasiveness.
  • The material containing the higher amount of mineral fibers shows also the higher friction coefficient, but also the higher fade sensitivity and the worst fade recovery.

Dosage of Subsitution of Potassium Titanate:

A4 shows a good friction coefficient, comparable to the OE material (A0) with a high amount of Potassium titanate, a low disc and pad wear and due to its chemical composition. It is also the one with the lower cost as it contains gypsum fiber instead of potassium titanate. Based on this first analysis, it is possible to say that a combination of mineral fibers and gypsum fiber in a ration 1:2 can be used to substitute 60% of potassium titanate in NAO friction materials.

In Summary, Gypsum Fiber provide with:

  • Low cost: alternative to potassium titanate when combined properly with mineral fibers.
  • Stable friction coefficient
  • Low fade sensitivity
  • Fast fade recovery
  • Low disc wear
  • Low rotor wear
  • Reinforcement and toughness: Improving mechanical strength;
  • Stable Friction Coefficient: Excellent Fiber Shape can behave as anchoring points to facilitate the formation of third body layer, creating a suitable condition for stable friction coefficient.
  • Good NHV performance: Gypsum Fiber Mohs Hardness is 2-3, providing the friction material with the mechanical strength but without damaging the metallic surface of the rotor. The material will facilitate abrasives for the third body layer but it will not create a hard contact point, avoiding rotor/disc scratch and potentially creating less vibrations and noise.
  • Improve comfortability: Softening the material of the friction block.
  • Improvement in corrosion for friction materials: Thermal behavior is also interesting as the material will lose small amounts of water during the friction material production process without losing its fiber shape. The material will then be able to be rehydrated and this represents a potential improvement in corrosion for friction materials.
  • Less Dust: Raw material is safe Food-grade Gypsum block.

Below pictures is the illustration of the contact situation between the pad and disc. A transparent disc is moving from left to right. Some of the wear particles pile up against the contact plateaus and create secondary plateaus. A flow of wear particles in the gap between the pad and disc wear the lowlands of the pad through three-body abrasion .

  • Proportion of Fibrous Calcium Sulphate : 3-8% of percentage of grits or grits +fillers. 
  • Formula amending and improving advise: Calcium Sulphate can substitutes of Cryolite, Barite, Alumina and Resin powder percentage partially. It just depends on different formulations.
  • Advised methods for blending/pre-blending: Can be mixed with abrasives, fillers. Can be mixed with resins liquid, be appropriate to longer mixing time to ensure blending evenly.
  • Preservation: water-proof, moisture-proof. Use as soon as possible after opening after opening the bag.