Innovation dynamics in car production technology: Network analysis of structural adhesives

Publication Type:

Conference Paper


Gerpisa colloquium, Detroit (2022)


network analysis, patent analysis, structural adhesives, value chain


Structural adhesives have been used in the aircraft industry for a long time, while their application to automotive manufacturing has only recently started. One of the background factors is the increasing demand for vehicle weight reduction and collision safety. For example, adhesives are combined with spot welding to reinforce steel-to-steel joining (weld bonding) or used with mechanical bonding such as riveting. In addition, structural adhesives are the primary bonding technology for joining dissimilar materials such as aluminum frames and carbon fiber reinforced plastic bodies.
While European automakers have taken the lead in structural adhesives, Japanese OEMs have been cautious about using them until recently. Chemical firms in the U.S. and Europe dominate in the global supply of structural adhesives. How have Western manufacturers established competitive advantages in the development and use of structural adhesives? This study analyzes the competition for innovation in structural adhesives.

Based on interviews and secondary sources, I will illustrate automotive structural adhesives’ recent applications and value chain. Then, the competition over R&D of structural adhesives will be analyzed for 30 years from 1990 to 2019 using patent data. When a new patent is filed, prior patents are cited (so-called “backward citation”) for the applicants or examiners to determine the novelty and usefulness of the patent in question or reject it. The patent may, in turn, be cited by subsequent patents (forward citations). This study analyzes the web of intellectual properties of structural adhesives by observing the citation networks, where patents are nodes and citations are links. The patent data is extracted from Bureau van Dijk’s Orbis Intellectual Property. I use the igraph package of the statistical analysis language R for the network analysis.

After a gradual increase in the 1990s, the number of patent applications began to increase sharply in the 2000s. Western companies such as 3M and Dow Chemical (U.S.), Henkel and Tesa SE (Germany), and Sika (Switzerland) have occupied the leading position for the entire period. Although the number of patent applications filed by Japanese adhesive manufacturers is not small, few patents have a large number of forward citations. It is also worth noting that the number of patent applications filed by Chinese companies has been increasing rapidly since the 2010s.
There are several isolated clusters in the citation networks of the structural adhesives (Figure 1), suggesting that structural adhesives are segregated according to specific technological themes. In addition, the backward and forward citations of patents are highly asymmetric. There are a small number of patents with a vast number of forward citations (many of which are inventions of Western companies). In contrast, many patents have no forward citations at all. Furthermore, there is a clear trend that the number of backward citations increases over time. This indicates that as the number of patents increases, subsequent patents may conflict with prior ones, and the scope of their claims may be limited. There is a possibility that “patent thickets” (Chavez and Lara, 2020) are occurring in the structural adhesives.
In traditional joining methods such as spot welding, friction stir welding, riveting, and clinching, automakers and parts manufacturers have the technological capability. Adhesives are treated as secondary materials and played a minor role. However, as the use of dissimilar materials increases to reduce CO2 emissions and improve crash safety, the application of structural adhesives is expected to expand in the future (Modi and Vadhavkar, 2019). As a result, the role of chemical manufacturers supplying structural adhesives will increase, which may affect the dynamics in the value chain of automobile production. One of the contributions of this study is the quantitative and visual presentation of such innovation dynamics through network analysis.
The future research agenda is as follows. First, the relationship between the structure of patent networks and innovation performance should be analyzed. In what kind of network structure do firms gain profit from their innovations? This research question concerns the value capture from innovations (Dedrick and Kraemer, 2015; Pisano and Teece, 2007). Second, there is the question of how the technological capabilities of firms possessing strong intellectual properties are generated. According to the literature on absorptive capacity, knowledge in related fields is the key to acquiring new technologies. Since structural adhesives have been used in aircraft production, the absence of the aerospace industry may be one of the reasons why Japanese firms lag behind the US and European competitors.

Chávez, A. and Lara, A. (2020) “The diversity of agents and patent thicket evolution in electric vehicles,” International Journal of Automotive Technology and Management, 20(1), 76-107.
Dedrick, J. and Kraemer, K. L. (2015) “Who captures value from science-based innovation? The distribution of benefits from GMR in the hard disk drive industry,” Research Policy, 44(8), 1615-1628.
Modi, S. and Vadhavkar, A. (2019) Technology roadmap: Materials and manufacturing, Center for Automotive Research, Ann Arbor, MI.
Pisano, G. P. and Teece, D. J. (2007) “How to capture value from innovation: Shaping intellectual property and industry architecture,” California Management Review, 50(1), 278-296.


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