World's greatest living rubber scientist

Over the last few years, I have had the opportunity to meet with Prof. Dr Wang Meng-Jiao ("M-J") a number of times at his offices in Qingdao.

In researching this feature, I spoke with a number of his co-workers. The phrase "world's best living rubber scientist" came up often during those conversations.

Because I think M-J's profile is lower here in the West than it should be is that much of his work has been very commercially-sensitive, and also that the last decade or so – as well as the first few decades of his life – were spent in China.

He was a strong contributor to the development of Michelin's 'Green X' tire back in the 1990s, when Degussa developed silicas and silanes that delivered a frequency-dependent (temperature-dependent) hysteresis response in S_SBR.

He developed the theory of rubber-filler and filler-filler interaction that led to the invention of wet-mixing that has led to substantial improvements in the triangle of tire performance that links wet grip, rolling resistance and wear properties.

He's also been responsible for developing new test procedures for measuring silica dispersion and other measures.

Early life in China

Prof Wang Meng-Jiao (“M-J”) was born in China in 1940. After gaining his first degree at Shandong University in physical chemistry in 1964, he immediately moved to the Beijing Research Institute for the Rubber Industry, under the Chinese Ministry of the chemical industry. 

There he spent nine years researching the ageing of rubber, followed by three years looking at vulcanisation and a year on rheology. This period covered the time up to 1977. 

During that time, Cultural Revolution swept through China. China was closed to academic exchange during that period.

At each assignment, M-J found the key texts in the Western literature and – in his spare time – translated them into Chinese, partly as an exercise and partly to better understand the subject. The first book, Vulcanization and vulcanizing agents by Werner Hofmann was re-published in Chinese in China. M-J was told that it was a good translation, and he was allowed to continue. His second translation was Physics of Rubber Elasticity by L. R. G. Treloar. M-J translated further three key texts on rubber science and technology into the Chinese language. They are Rubber Chemistry by J. A. Brydson, The Stereo Rubbers edited by W. M. Saltman, and Carbon Black - Physics, Chemistry and Elastomer Reinforcement by J–B. Donnet and A. Voet”.

M-J said, “As I was translating these books, I was learning from them. This was a better education that was available for people in China at that time.” His only material reward was a handful of free copies of the translated version. Meanwhile, he was publishing prolifically in the Chinese language.

China started to open to foreigners from 1978. Students were allowed to travel overseas. M-J applied, but was refused, on the grounds that he was important to the Institute. 

Moving to the West

By 1982, a few researchers applied for overseas funding to study overseas. M-J applied to both Prof Jean-Baptiste Donnet at the CNRS in France and to Alan Gent at the University of Akron. Both accepted him, but Akron U could not take him immediately, so he went to CNRS to work with Prof. Donnet.

Over a 2-year period, he wrote a doctoral thesis presented in 1984. It was supervised by Prof. Donnet and examined by – among others – Leonard Mullins.

Doctoral thesis: Etude du renforcement des élastomères par les charges: effet exercé par l’emploi de silices modifiées par greffage de cha?nes hydrocarbonées

At the beginning of 1985, M-J went to Akron University. For eighteen months he worked with Prof. Frank Kelley, who remembers M-J as a visiting professor. At Akron U, his research topic was the effect of crosslink structures of NR and SBR on time-temperature dependences of tearing, granted by Goodyear. The results were published in Kautsch. Gummi Kunsts after they were released.

Working on silica-silane filler systems

Meanwhile, the DIK (German Rubber Research Institute) was being established in Hanover, and Prof Donnet recommended that they approached M-J. He accepted a position at the DIK and spent 18 months developing new theories of rubber reinforcement based the surface energy measurement of the materials used in rubber industry. He was a pioneer of research of polymer-filler interactions and their effects on the properties of filled vulcanisates.

Quickly, his skills came to the attention of Siegfried Wolff, senior researcher and Director of R&D for rubber chemicals at Degussa. M-J went to work with Wolff, where Degussa was developing new silica-silane combinations alongside Michelin ahead of the launch of the Green-X tire.

M-J published a series of papers on rubber-filler interactions while he was at Degussa; many co-authored with Dr Wolff. M-J said, “I was the one who wrote the fundamental research on silica and carbon black at Degussa that time.” 

Four years later, Wolff retired, in 1992, just after the Michelin patents on the Green-X tire were published.

Moving on to Cabot

M-J said the researchers at Degussa were more interested in applications development, so he was happy when Cabot approached him. After he joined Cabot Corporation, he was asked to develop new carbon black materials to compete with silica.

This involved three different approaches:

1. First we looked at modifying the filler surface and using chemicals. So we looked at modifying carbon black surfaces. This was in 1993. 

2. We developed another carbon black. And this was able to compete with silica in tire compounds, but had better wear resistance. That was what we called a carbon/silica dual phase filler.

3. Developed the theory behind wet mixing of carbon black with NR latex.

At the same time, he established a theory about the dynamic properties of filled vulcanisates. According to this theory, among others, the key factor controlling the dynamic modulus and hysteresis is the filler agglomeration. When the filler agglomeration is depressed the hysteresis of the vulcanisate reduces at higher temperature which gives lower rolling resistance of tire, and the hysteresis at lower temperature increases which leads to higher wet grip. He also proposed the thermodynamic and kinetic of filler agglomeration from which the approaches for reduction of filler agglomerates were given. All the concepts were written in the paper:

M.-J. Wang, Effect of Polymer-Filler and Filler-Filler interactions on Dynamic Properties of Filled Vulcanizates” Rubber Chemistry and Technology, 71, 520~589 (1998). 

This paper has been cited in 981 related studies.

However, one aspect of the science confused him. He spent the five years between 1994 and 1999 understanding why the wet-skid resistance of the first generation of dual-phase filler did not meet the predictions from the classical theory and why the correlation between wet grip of tire and hysteresis at low temperature was poor. 

He said, “I was talking about this totally new concept. How to improve the wet grip.”

He added that, “most of the researchers omitted the fact that there is a layer of water when we discussed wet grip.” He concluded, “While I was at Cabot, we developed the whole concept.” Later, the results of his efforts were published in the following papers:

M. -J. Wang and Y. Kutsovsky, Effect of fillers on wet skid resistance of tires. Part I. Water lubrication vs. filler-elastomer interactions, Rubber Chemistry and Technology, 81, 552~575 (2008). 

M. -J. Wang and Y. Kutsovsky, Effect of fillers on wet skid resistance of tires. Part II. Experimental observations on effect of filler-elastomer interactions on water lubrication, Rubber Chem. Technol., 81, 576~599 (2008). 

The concept explained that the micro-elasto-hydrodynamic lubrication of water plays a dominant role in wet grip which is affected by the surface composition of the vulcanisates. 

Based on the new theory, they developed a new generation of dual-phase fillers that compete with silica in rolling resistance and wet grip of tire, and more importantly, the wear resistance is significantly improved. 

Another important aspect of M-J’s research in Cabot was abrasion which is related to tire wear. He found that besides the surface area and structure of the fillers, the polymer-filler interaction plays a very important role in rubber abrasion which was described in the paper: 

M. –J. Wang, Effect of filler-elastomer interaction on tire tread performance, Part III. Effect on Abrasion, Kautsch. Gummi Kunsts., 61, 159 (2008).

This concept allowed Cabot to develop a new mixing process – a continuous liquid phase mixing to produce NR/carbon black masterbatches (also known as Cabot Elastomer Composite, CEC for short). In the CEC process, the carbon black slurry is injected into the mixer at very high speed and mixes continuously with NR latex stream. Under highly energetic and turbulent conditions, according to the mechanism proposed by M-J, the mixing and coagulation of polymer with filler is completed mechanically at room temperature in less than 50 millisecond, without the aid of chemicals. The key feature of the CEC process is the fast mixing and coagulation, and a short drying time at high temperature. This achieves excellent performance for the material as polymer-filler interaction can be better preserved and polymer degradation can be well eliminated which are discussed in detail in the following paper.

M. –J. Wang, T. Wang, J. Shell and K. Mahmud, NR/carbon black masterbatch produced with continuous liquid phase mixing. Kautsch. Gummi Kunsts., 55, 388 (2002).

The CEC technology was sold to Michelin, who commercialise it as the ‘Carbion’ material 

Setting up EVERI in Qingdao

M-J ‘retired’ from Cabot in late 2009, aged 69. He quickly set up a lab in Qingdao, in the Rubber Valley Park called EVERI (EVE Rubber Institute) to further his work. In addition to conducting basic and application researches, such as vulcanization, aging, reinforcement, rheology and adhesion of rubber with textile and steel cord, this Institute has developed a continuous liquid phase mixing process further to include solution-rubber and silica. The masterbatches produced with this process are called Eco-Visco-Elastic Composite (EVEC) that are characterized by perfect dispersion of silica in the polymer matrix, higher polymer-filler interaction and lower filler-filler interaction which expands the triangle of wet grip, wear resistance and fuel economy by a huge margin. 

Nine years later, the Institute has fully developed the theory and the technology and has built factories to commercialise the new mixing process to make EVEC for tire manufacture.