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CN-122011309-A - Modified phenolic resin-based material for high-temperature-resistant brake pad and preparation method thereof

CN122011309ACN 122011309 ACN122011309 ACN 122011309ACN-122011309-A

Abstract

The invention belongs to the technical field of friction materials and phenolic resin modification, and discloses a modified phenolic resin-based material for a high-temperature-resistant brake pad and a preparation method thereof, wherein the modified phenolic resin-based material comprises, by weight, 80-120 parts of a phenolic resin of novolacs, 8-30 parts of a phenolic prepolymer of low free hydroxymethyl resol type containing a rigid bisphenol structural unit, and 6-9 parts of hexamethylenetetramine, wherein the rigid bisphenol structural unit exists in the phenolic prepolymer of low free hydroxymethyl resol type in the form of a copolycondensation structural unit, and the obtained material still maintains a part of functional structural unit which is not fully reacted after primary molding. The preparation method comprises the steps of preparing low-free hydroxymethyl resol type phenolic prepolymer by prepolymerization, mixing with novolak type phenolic resin, adding hexamethylenetetramine, hot-press forming and curing in stages. The material has good high-temperature structural stability and heat fading resistance, and is suitable for resin-based bonding phases in friction materials of brake pads.

Inventors

  • WANG JINWEI
  • JIANG LIANGMIN
  • Lou Juanli

Assignees

  • 浙江意超工贸有限公司

Dates

Publication Date
20260512
Application Date
20260330

Claims (10)

  1. 1. The modified phenolic resin-based material for the high-temperature-resistant brake pad is characterized by comprising, by weight, 80-120 parts of a novolac type phenolic resin, 8-30 parts of a low free hydroxymethyl resol type phenolic prepolymer containing a rigid bisphenol structural unit and 6-9 parts of hexamethylenetetramine; wherein the rigid bisphenol structural units in the low free hydroxymethyl resol-type phenolic prepolymer containing the rigid bisphenol structural units exist in the low free hydroxymethyl resol-type phenolic prepolymer in the form of copolycondensation structural units, and the modified phenolic resin-based material still maintains the functional structural units which are partially not fully reacted after primary molding.
  2. 2. The modified phenolic resin-based material for high-temperature-resistant brake pads according to claim 1, wherein the low free hydroxymethyl resol-type phenolic prepolymer has a free hydroxymethyl content of 3.0-10.0wt%.
  3. 3. The modified phenolic resin-based material for high temperature resistant brake pads of claim 1, wherein said rigid bisphenol structural unit is 9, 9-bis (4-hydroxyphenyl) fluorene.
  4. 4. The modified phenolic resin-based material for high temperature resistant brake pads of claim 1, wherein the functional structural units that are not fully reacted comprise one or both of hydroxymethyl and benzyl ether structures.
  5. 5. The modified phenolic resin-based material for high-temperature resistant brake pads according to claim 1, wherein the low free methylol resol-type phenolic prepolymer containing rigid bisphenol structural units is prepared by prepolymerizing phenol, formaldehyde and a rigid bisphenol-type compound under the condition of base catalysis.
  6. 6. A method for preparing the modified phenolic resin-based material for the high-temperature-resistant brake pad according to any one of claims 1 to 5, which is characterized by comprising the following steps: s1, carrying out prepolymerization on phenol, formaldehyde and a rigid bisphenol compound to obtain a low free hydroxymethyl resol type phenolic prepolymer containing a rigid bisphenol structural unit; S2, mixing novolacs type phenolic resin with the low free hydroxymethyl resol type phenolic prepolymer to obtain a resin mixed system; s3, adding hexamethylenetetramine into the resin mixed system, and uniformly mixing to obtain a mixture to be molded; S4, carrying out hot press molding on the mixture to be molded, and carrying out staged curing, so that the obtained material still keeps partial functional structural units which are not fully reacted after primary molding, and the modified phenolic resin-based material for the high-temperature-resistant brake pad is obtained.
  7. 7. The method according to claim 6, wherein in the step S1 of the prepolymerization, formaldehyde is added in the form of an aqueous formaldehyde solution or paraformaldehyde, the prepolymerization temperature is 60-90 ℃, and the prepolymerization time is 1-4 hours.
  8. 8. The method according to claim 6, wherein the temperature at which the phenolic novolak resin and the low free methylol resol phenolic prepolymer are mixed is 80 to 100℃and the mixing temperature at which hexamethylenetetramine is added is 65 to 80 ℃.
  9. 9. The method of claim 6, wherein the staged curing comprises maintaining at 110-125 ℃ for 10-20 min, at 140-155 ℃ for 20-40 min, at 165-175 ℃ for 10-25 min, and then post-treating at 175-182 ℃ for 0.5-1.5 h.
  10. 10. The application of the modified phenolic resin-based material for the high-temperature-resistant brake pad in the friction material of the brake pad in any one of claims 1-5.

Description

Modified phenolic resin-based material for high-temperature-resistant brake pad and preparation method thereof Technical Field The invention belongs to the technical field of friction materials and phenolic resin modification, and particularly relates to a modified phenolic resin-based material for a high-temperature-resistant brake pad and a preparation method thereof. Background Phenolic resin has the advantages of better heat resistance, cohesiveness, formability and cost, is used in friction materials such as brake pads for a long time, and particularly plays an important role in combining reinforcing fibers, fillers and friction adjusting components in the braking process as a resin-based binding phase. Wherein, the phenolic resin of novolacs is matched with hexamethylenetetramine to be cured to form a crosslinked network, which is one of the systems in common use at present. However, with the improvement of the requirements of automobiles, engineering machinery and high-speed equipment on braking performance, the thermal load born by the brake pad is obviously increased under the working conditions of continuous braking, heavy-load braking and high temperature, and the problems of insufficient heat resistance, obvious heat decay, easy pulverization of a surface layer structure and insufficient friction stability of the traditional phenolic resin-based material are gradually exposed. Particularly under the high-temperature friction condition, the resin bonding phase is easy to be thermally decomposed or the structure is unstable, so that the friction layer is discontinuous, the abrasion is aggravated, and the braking safety and the service life are further influenced. The prior art generally enhances the high temperature properties of phenolic resins by introducing heat resistant components, increasing the degree of crosslinking, or improving the resin matrix structure, but still suffers from some drawbacks. On one hand, the partial modification scheme can improve the initial heat resistance, but easily leads to the increase of brittleness of the material and influences the toughness and the wear resistance in practical use, and on the other hand, some multicomponent composite systems have the problems of mismatching reaction temperature areas and insufficient synergy among components, and are difficult to combine the molding processability and the high Wen Fuyi stability. In addition, in the prior art, design considerations of retaining a part of functional structural units capable of continuing to react after primary molding and further stabilizing the surface layer structure under a high-temperature working condition are insufficient, so that it is difficult to effectively improve the continuous stability under a high-temperature braking condition. Disclosure of Invention In order to solve the defects in the prior art, the invention aims to provide a modified phenolic resin-based material for a high-temperature-resistant brake pad and a preparation method thereof, wherein the material takes novolacs type phenolic resin as a main body, a low free methylol resol type phenolic prepolymer containing rigid bisphenol structural units is introduced, and is matched with hexamethylenetetramine for curing, so that the obtained material still keeps partial functional structural units which are not fully reacted after primary molding. By controlling the composition of the prepolymer, the proportion of raw materials and the staged curing process, the structural stability, the surface continuity and the heat fading resistance of the material under the high-temperature working condition are improved, and the resin-based adhesive phase is suitable for the friction material of the brake pad. The aim of the invention can be achieved by the following technical scheme: The modified phenolic resin-based material for the high-temperature-resistant brake pad comprises, by weight, 80-120 parts of a novolac type phenolic resin, 8-30 parts of a low free hydroxymethyl resol type phenolic prepolymer containing a rigid bisphenol structural unit, and 6-9 parts of hexamethylenetetramine; wherein the rigid bisphenol structural units in the low free hydroxymethyl resol-type phenolic prepolymer containing the rigid bisphenol structural units exist in the low free hydroxymethyl resol-type phenolic prepolymer in the form of copolycondensation structural units, and the modified phenolic resin-based material still maintains the functional structural units which are partially not fully reacted after primary molding. Further preferably, the low free hydroxymethyl resol type phenolic prepolymer has a free hydroxymethyl content of 3.0 to 10.0wt%. Further preferred, the rigid bisphenol building block is 9, 9-bis (4-hydroxyphenyl) fluorene. Further preferably, the functional building blocks that are not fully reacted include one or both of hydroxymethyl and benzyl ether structures. Further preferably, the low free methylol resol type phenolic