What might be relevant is IntAct. It is curated protein-protein interaction resource where the curators looked at 11 different protein-protein interaction resources (including STRING), combined and filtered out interactions that they thought weren't real. Apart from a useful resource by itself you might also want to read up on how the curators did that and what tools they used which might lead you to the tools you asked for. But maybe by itself it will already solve your problem.

https://www.ebi.ac.uk/intact/

What do you mean by "functional protein association network"? are you looking for predicting substrate specificity? catalytic mechanism? protein-protein interaction? or trying to generally assign function to a query protein? If your question does not relate to protein-protein interaction, I'd suggest sequence similarity networks, as demonstrated here: http://www.ncbi.nlm.nih.gov/pubmed/25210038 

Thank you Dr. Evelo.

@ Dr. Akiva, Actually I am looking for the interacting partners and to predict the functional traits from the structural features.

Hi, for finding the interaction partners of certain protein you can search for the protein in protein-protein interaction databases such as BioGrid and IntAct. If you want to represent a protein-protein interaction network use Cytoscape and in the Cytoscape App Store find a network representation plugin such as BisoGeNet or other.