What type of material is the seal on the gland open to the outside to keep foreign material from?

The seals normally consist of rubber O-rings on the outer edge of the gland and a combination of synthetic materials and rubber o-rings on the interior sleeve which slides on the piston rod. This could vary, depending on the type of cylinder gland used on your particular hydraulic cylinder. The plastic or nylon seals often harden and crack over a period of time like those you mentioned in your question.

I hope this is the answer you are looking for.

Thank you, very helpful, Randy I had an idea it was different than rubber .

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.