... that to participate in the balloting process for TAPPI Standards you must sign up for the Standard-Specific Interest Groups (SSIGs)?

Drafts are available for anyone to review, but to vote and comment you must be a member of the SSIG. Each Standard has its own SSIG – so you have to sign up for each Standard that you have an interest in. Links to all of the SSIGs (by subject category) can be found on the Subject Category for Standards web page.

When you click on a Subject Category, it will take you to the page where you can sign up online: https://www.tappi.org/Get-Involved/Develop-Standards-Methods/standard-specific-interest-group/