Designing with HMPE's Creep Property
HMPE fiber is sensitive to long-term static loads and will elongate proportionally with time. This phenomenon is known as creep, and is a process in which the long molecular chains slide along each other. Ever since the commercialization of our HMPE fiber back in the 1990s, DSM Dyneema has recognized the importance of creep in customer applications. It’s something we have focused on closely and the reason we have since run a program to determine how applications made with Dyneema® will behave when placed under long-term static loads.
HMPE offers superior performance characteristics
The high strength, low density, and good mechanical and chemical properties mean high modulus polyethylene fibers (HMPE) are used in a wide variety of applications. Ropes made with HMPE offer a number of advantages that make it a superior alternative for steel wire rope and ropes made from other synthetic materials for a wide range of applications and usages. HMPE’s advantages include:
- Lower weight (ease of handling)
- Smaller diameter (easier storage and transportation)
- Higher stiffness
- Excellent long-term properties (tension and bending fatigue, UV and chemical resistance)
Creep is not a factor in many applications
The creep of all HMPE fibers is influenced by the ambient temperature and the load applied: very high loads or a high temperature will accelerate the creep process. But most applications involving ropes made with HMPE are not subject to constant loads, or they are used at low environmental temperatures. It is rare for both temperature and load to be a factors at the same time.
In many situations, the creep property of HMPE is actually irrelevant to the application and can be safely ignored.
Advancing scientific understanding of HMPE
Over the course of a multiyear research program, we have determined which variables have a bearing on an HMPE fiber's resistance to creep. This led to the introduction of Dyneema® SK78, which offers good creep properties for most of the applications in which HMPE is used.
Going further, we have now determined the creep characteristics of all Dyneema® fibers. Knowing this we then developed a Creep Design Tool. This can predict creep rate and elongations precisely, and estimate creep lifetime accurately. With offshore industry norms now including the use of this predictive creep model, creep in HMPE is now just another design parameter. And one that is really simple to model. Learn more in this short film.
Dyneema® Max Technology: the secret to enhanced creep properties
Further research on the creep property of HMPE led to breakthrough Dyneema® Max Technology, and the introduction of Dyneema® DM20, a step change in creep performance versus SK78 and all other HMPE fiber grades. Dyneema® Max Technology extends the application areas of the world’s strongest fiber. Dyneema® Max Technology is designed for long-term permanently loaded systems, like mooring offshore production platforms.
Meet our expert in HMPE creep
Martin Vlasblom is Applied Research Manager at DSM Dyneema and holds an MSc. in Industrial Design Engineering from Delft University, the Netherlands. Martin, who has extensive experience in polymer-related industries, is responsible for building knowledge on characterizing and improving the long-term properties of Dyneema®. He is the product developer of the DM20 fiber type.