Considerations in the formulation of rubber products

 

The rubbers come from two different sources: natural rubber, which is created using latex extracted from rubber trees; and synthetic rubber, which is chemically synthesized. Regardless of origin, each rubber is characterized by its ability to withstand very large deformations and then essentially "recover" to its original state. Natural rubber, although used in many products today, has limitations of mechanical, chemical and environmental resistance that would make it unusable for many applications; very often synthetic rubbers can be formulated to address these deficiencies.

In reality, there are no standard rubber materials; For each use, there is a custom formulated product that is tailored to the precise needs of that application. Rubber is a much more complex material than other materials such as steel or plastic. While steel or plastic is usually the result of the fusion of 3 to 4 materials, a rubber formulation often consists of 10 to 20 mixed materials. Additionally, several of these components will undergo an irreversible chemical reaction when the rubber is vulcanized during the manufacturing cycle. Due to the large number of ingredients and transformative chemical reactions, there is no realistic way to reverse engineer rubber. wetpour maintenance rubber is more "art" than "science".

When formulating a rubber product, there are three types of performance challenges to consider.

Dynamic. The only factor that distinguishes rubber from other materials is the large deformations it can withstand in its applications. Rubber must maintain its properties throughout a lifetime of dynamic stress. The rubber must be strong enough to perform its function even after it has been compressed, stretched or twisted thousands or even millions of times.

Chemical. Rubber is often required to resist a variety of chemicals. For engine or generator applications, it must be resistant to gasoline and oils. Some industrial equipment will see a variety of strong fluids such as cleaning solvents, acids, or alkalis. Rubber tubes can have a lot of strong fluids pumped through them. Without proper formulation, a rubber compound could literally dissolve or crumble when faced with these corrosive elements.

Environmental. Not only does rubber have to remain flexible for thousands of cycles and possibly resist corrosive chemicals, but it may also need to function in extreme temperatures. A good example of this is a stationary car in a Minnesota winter - overnight, the sealing o-rings on your engine will be subjected to freezing temperatures. The o-rings should seal as well when the cold engine is first started as when the engine reaches its maximum temperature.

When these performance challenges are combined, it can create a tremendous (if not impossible) task for the rubber formulator.

The first step in rubber formulation is to develop detailed requirements related to the conditions that the rubber must withstand. It is quite easy to identify the mechanical / dynamic requirements; however, chemical and environmental factors are often misunderstood. In this case, a very experienced rubber formulation chemist is required. The chemist has seen a wide variety of applications and can help identify what conditions a product might experience in the field.

After thoroughly understanding all the requirements, a rubber formulation chemist can derive a recipe from dozens of components to create the compound. Rubber formulation is extremely complex and can take advantage of literally hundreds of potential variables. Due to the scale of this complexity, there are not many tools and guides to analytically determine the exact formulation that will optimize performance for a given application. Achieving optimum performance with rubber is much more of an "art" than a "science", and requires experienced and knowledgeable formulators.

It is not uncommon for several different blends to be created and tested before developing the ideal product. Temperature stress, fluid immersion, elongation tests, tensile strength, flex cycles, ozone aging, and weathering can all be performed in a laboratory, and these tests provide some indication of product performance. . However, only tests that duplicate field conditions can be relied upon to determine the acceptability of the formulation.