Dynamic. The one factor that distinguishes rubber from all other materials is the very large deformations that it can endure in its applications. Rubber must maintain its properties through a lifetime of dynamic stressing. Rubber has to be resistant enough to perform its function even after being compressed, stretched or twisted hundreds, or even an incredible number of times.
Chemical. Rubber is often required to withstand a number of chemicals. For applications in motors or generators, it should be resistant to gasoline and oils. Some commercial equipment will see a variety of harsh fluids such as cleaning solvents, acids or alkalis. Rubber tubes can have any number of harsh fluids pumped through them. Without correct formulation, a rubber compound could literally dissolve or crumble when faced with these rust elements.
The first step in rubber gasket formulation is to develop detailed requirements relating to conditions that the rubber will need to withstand. It is fairly straight forward to recognize the mechanical/dynamic requirements; yet , chemical and environmental factors are commonly misunderstood. Within this case a rubberized formulation chemist with a great deal of experience is necessary. The chemist has seen a large variety of applications and can help identify what conditions a product could possibly experience out in the field.
After thoroughly understanding all the requirements, a rubber formulation chemist can derive a recipe of dozens components to create the compound. Rubber ingredients is incredibly complex and can draw upon literally hundreds of potential variables. Since of the scale of the complexity, there are not many tools and guides to analytically determine the exact formulation that will optimize performance for a given application. Achieving ideal performance with rubber is far more of an “art” than the usual “science”, and requires experienced and educated formulators.
One example that demonstrates the complexity of rubber formulation involves a peristaltic tube application. This particular tube was used in an agricultural product to pump fertilizers and herbicides through it, with the pumping action occurring from alternating cycles of compression and relaxation of the rubber tube. The pump motor manufacturer purchased a rubber tube from one dealer that normally exceeded two hundred fifity, 000 cycles at newly arriving testing, but occasionally batches would fail at less than 10, 000. The particular manufacturer sought out a fresh supplier, and a new rubber formulation was developed that exceeded 3, 500, 000 cycles to disappointment. Needless to say, the customer was extremely happy.
After the product is developed and tested, it is ready for manufacturing. Manufacturing custom formulated rubber requires extremely tight process controls. Because seen from the peristaltic tube example, a very small variation can dramatically affect the performance of the rubber.
Are there are times when it is impossible to meet a set of requirements with any rubber formulation? The answer of course is “yes”; but more commonly the problem is cost, somewhat than what is possible. The rubber component is a relatively expensive product when compared with plastic or even precious metals, and sometimes the needed formulation is too costly for practical use. Nevertheless, for a lot of critical applications rubberized often performs with greater elegance and lower total cost than the options, and certainly with the highest degree of flexibility.