How to get second material name from product description

Product description is string like

Main fabric: 50% Organic Cotton, 49% Cotton, 1% Elastane

Material names are between % and , or up to end of string for last material name Elastane.

Tried to get second material name "Cotton" using

select (regexp_matches('Main fabric: 50% Organic Cotton, 49% Cotton, 1% Elastane', '%\s(.+),?','g'))[2]

but query does not return any data.

How to get second product name? Using PostgreSql 16

Again, regexp_substr() can handle that:
_{demo at db<>fiddle}

select regexp_substr('Main fabric: 50% Organic Cotton, 49% Cotton, 1% Elastane', 
                    '% ([^,]+),?',1,2,'',1)

• You're looking for % followed by the material name
• The material name is expected to be anything after that, up until the end or nearest comma. The [^,]+ means one or more character other than the comma, so it tolerates spaces, hyphenated names etc.
• ,? mean at most one comma, so that you don't need a trailing comma at the end to get a match

The parameters after the pattern are the same as in the post in the other thread.

• 1 tells it to start at the beginning
• 2 means you want the second match
• '' is where you'd add flags, like 'i' for case insensitive matching
• 1 means the first parenthesised sub-expression within the pattern, so it'll only catch the material name, without the leading % and the optional trailing comma.