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Rubber Line mark problem

Rubber Line mark problem

Rubber Line mark problem

(OP)
How to get rid of line mark problem in NR/SBR compound?

RE: Rubber Line mark problem

Can you explain what you mean by a "line mark problem"?

RE: Rubber Line mark problem

Better still, can you upload a photograph of the problem?

forumtowers.com

RE: Rubber Line mark problem

(OP)
Line mark means, after the molding process some minor lines are appearing on the surface of the product(approx width=0.1 mm length=1 cm). These lines are spoiling the visual appearance of the product. I don't know whether line mark and flow mark are same or different. I think it is because of the viscosity of the compound. It is a high hardness compound (85 shore A).

RE: Rubber Line mark problem

Assuming this isn't a mold part line, it sounds like a flow problem: not flowing enough before cure gets underway. Lowering viscosity and/or slowing the cure rate may help this. Or, it could be due to some mold release being trapped where the rubber flows together.
As Graham pointed out, a picture would be helpful.

RE: Rubber Line mark problem

(OP)
It is not clear in the picture. And it is not because of the mold release agent. I think viscosity and cure rate are also the factors. I have given more time for mastication at @85°C but the viscosity is not going down. And is blending of NR/SBR a factor?

RE: Rubber Line mark problem

How are you moulding the part? Compression, transfer, or injection?
What is the viscosity of the compound after mixing?

forumtowers.com

RE: Rubber Line mark problem

(OP)
Transfer molding,ML is 13

RE: Rubber Line mark problem

ML on the rheometer trace is not the same as Mooney viscosity and does not bare any relationship to processing or mould flow capabilities. Are the lines you see on the cured product anywhere near the gates?

forumtowers.com

RE: Rubber Line mark problem

(OP)
I agree that ML is not directly related to mooney.....and the line marks are opposite to the transfer side

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