Liquid Binder Resins for Rail Brakes
Cardolite offers a wide variety of solvent and solvent-free thermosetting liquid binder resins for train blocks that reduce dust in the process, improve flexibility, provide high friction coefficient and hardness as well as good heat resistance. Black particles are also an option to withstand higher temperatures while still providing all the usual cashew friction particle advantages.
FRICTION PARTICLES PRODUCT OVERVIEW
|Mesh Size||Brown Particle||Black Particle|
|100 or finer||NX-5207||NX-5208|
BINDER RESINS PRODUCT OVERVIEW
|High Viscosity (80%-90% Solids)||Low viscosity (80% Solids)||Solvent-free||Elastomer Modifies (80% Solids)|
CNSL BASED FRICTION MATERIALS
Cardolite offers a wide range of cashew nutshell liquid (CNSL) based friction material designed especially for heavy-duty brake performance such as required in rail applications. Tough and demanding conditions required in rail brakes can be met by the addition of black friction particles and/or the use of CNSL binder resins. Black particles can withstand higher temperatures while still providing all the usual cashew friction particle advantages such as noise dampening, wear retardation, and friction stabilization. CNSL binder resins provide excellent flexibility, impact, thermal shock and processing viscosity and they can be used in combination with other phenolic resins and rubber.
Brake manufacturers can choose the most appropriate black friction particle or binder resin for its rail application from a broad range of products. Selection will depend on particle size of friction dust or viscosity of liquid resin, heat resistance and hardness requirements, desired flexibility, and type of manufacturing process used (dry or wet) amongst other criteria and special needs. The table on the left is a summary of various friction materials properties and end use applications to aid in product selection.
FRICTION PARTICLES TYPICAL PROPERTIES
|Properties||Brown Particles||Black Particles|
|Heat Resistance (10% decomposition)||320 – 350°C||360 – 390°C|
|Heat Resistance (50% decomposition)||410 – 440°C||520 – 560°C|
|Recovery||1.4 – 1.9 mm||1 – 1.5 mm|
|pH Value||4 – 10||2 – 7|
BINDER RESINS TYPICAL PROPERTIES
|Properties||Solids (>97%)||Lower Solids (80%)|
|Viscosity @ 25°C (cPs)||25,000 – 130,000||1,500 – 35,000|
|Gel Time @ 82°C (min)||20 – 55||8 – 35|
|Visual gel particles/g||< 20||< 20|
HIGH PERFORMANCE WITH DUST REDUCTION
Black particles help dissipate heat across the surface to avoid hot spotting that lead into fade. They also contribute to wear reduction and help to control the overall surface hardness.
Solvent free CNSL liquid binder resins are mainly used in asbestos and non-asbestos rolled linings, heavy duty and railway blocks. Hexamine addition of 8-9 wt% of the resin is recommended for cure. Solvent free resins are a great choice in situations where organic solvents are restricted. Mild heating to 50°C will reduce viscosity somewhat and aid resin wetting of formulation ingredients.
CNSL liquid binder resins containing solvent makes the resin easy to use, but the solvent must be removed after the mixing/rolling process. Hexamine is used to cure these resins and 7-9 wt% of the resin solids content is recommended.
CNSL elastomer modified liquid binder resins are primarily used in flexible asbestos free rolled segments. A single solvent or solvent blend is used to reduce the viscosity for easier mixing. Because of the rubber modification these resins are also highly useful in applications where some softening or reduced rigidity is desired. To cure these types of resins, hexamine should be added at 6-7 wt% of the resin solids content. The elastomer part may be cured with 1.5 wt% sulfur and 2.1 wt% zinc oxide on a resin solids basis.
Cardolite intermediates are C15 alkyl phenols, a mixture of C15 alkyl phenols, or dimer/trimer of C15 alkyl phenols. The primary use of these chemicals is as a substitute for phenol streams to improve flexibility and water sensitivity.