EPDM Microcellular Elastic Pad for China’s High-speed Railways Has Bright Prospects

By Tanyu, Zhuzhou Times New Material Technology Co., Ltd

In recent years, China’s high-speed railways have been highly acclaimed by passengers due to the advantages of large cabin space per passenger, high speed, good safety, reduced affects of bad weather, high punctuality, comfort, convenience, low energy consumption, minimal environmental impact and good value for the ticket price. By the end of the 12th Five-Year Plan period (2011-2015), China’s railway operating mileage will increase from 91 000 kilometers in 2010 to around 120 000 kilometers. By 2020, considering new railways and speed increases on existing track, China’s railway express passenger transportation network will reach more than 50 000 kilometers, connecting all provincial capitals and all cities with a population of over 500 000, and reaching the hometowns of more than 90% of the population.   
With the increased speed, the requirements for safety and comfort are also higher, so the application of rubber damping products has also increased, and more rubber varieties are used, commonly including NR (natural rubber), CR (chloroprene rubber), BR (cis-1,4-polybutadiene rubber), SBR (styrene-butadiene rubber), EPDM (ethylene propylene diene monomer) and PU (polyurethane), etc. A large number of research results for microcellular rubber foam pad materials have been achieved both at home and abroad. In foreign countries, elastic supporting blocks are very useful as the medium-vibration damping measure for tracks and are widely used all over the world. Here in China, Guangzhou’s No.1 subway and the Shanghai subway have used vibration-damping track fasteners, which have declining damping performance and have a shorter service life. Elastic supporting block integrated track bed is not used much in engineering in China. However, due to their porous structure, rubber foam materials allow larger compressed deformation, absorb large amounts of energy during the deformation period, have excellent damping characteristics, and can be used as damping and buffer materials. In addition, the foam materials can save raw materials and cost. At present, players here and abroad have used foaming processes to develop damping products like EPDM microcellular elastic pad. EPDM microcellular elastic pad has a closed honeycomb structure. The vertical elastic deformation of conventional rubber pad is replaced by lateral deformation. During compression, deformation of a microcellular rubber pad is achieved mainly through deformation of the honeycomb structure, and the rubber is not prone to fatigue. EPDM features excellent aging resistance, ozone resistance and heat resistance, its stiffness can be tailored to requirements, and it is not only suitable for ballastless track (long sleepers buried, elastic supporting blocks, and slab tracks), but also suitable for a ballasted track’s ballast mat.
Mainland China mainly uses PU foam pad. PU pad can be produced fast and efficiently. EPDM is highly weather resistant and has the most stable performance during a long service life. It occupies nearly 50% of the markets in North America and Europe, and has great application potential.
The technology of EPDM microcellular elastic pad is dominated by foreign companies. Based on a type of track pad, Zhuzhou Times New Material Technology Co., Ltd has spent two years to fully research the influences of foaming system, vulcanization system, reinforcing system, functional materials, and the preforming process and vulcanization process of sizing materials on the foaming effect and stability of foam rubbers, explore the influences of the vulcanization system and vulcanization process on the static stiffness, dynamic stiffness and fatigue properties of microcellular forming pad, thus obtaining foam rubber materials with excellent tensile properties, breaking elongation, aging properties, permanent compression deformation performance as well as suitable static stiffness and dynamic stiffness/static stiffness ratio.
With the development of high-speed railways, applications of microcellular foam pad materials will be more numerous and sales volumes will grow. At the same time, as freight volume increases in heavy-duty railways, the existing railways should be renovated to withstand the truck axle load and increase the bearable volume. Therefore, microcellular rubber foam pad materials have broad development prospects here as well.

Green mobility saves energy and reduces emissions

According to a study made by China Automotive Technology & Research Center, four types of innovation – green tires, lightweight materials, aerodynamic techniques and new-energy vehicles – can save energy saving and reduce emissions; however the green tires and lightweight materials are the most effective.
Green tires with lower rolling resistance could save 4% - 6% of fuel consumption without compromising safety. This makes them an extremely attractive option for any motor vehicle owner to increase fuel efficiency and cut costs – especially the operators of taxis and bus systems.
The study discovered that lightweight materials could make a remarkable contribution to saving energy and reducing emissions. If the weight of half the cars in Shanghai were reduced by 10% by 2020, around 159 000 tons of fuel could be saved, and 524 000 tons of CO2 emissions could be avoided.
At present, plastics and plastic-metal hybrids are finding increasing use in China’s automobile industry, with applications from under the hood and in functional parts such as fastening elements, guides, contact surfaces, engine bearings, door structures, front ends, seat cross-members, etc. High-tech plastics boast many advantages, including lower processing costs, exceptional strength and stable properties. They also bring entirely new construction and design possibilities.