TR Compounds
As the name suggests itself TR stands for Thermo Rubber Compounds.
This compound is more closer to rubber then TPR as the "p", which stands for plastic is missing in TR compounds,that means no plastic ingredient is used to make this type of compounds and as a result the physical properties of this TR compound is just like rubber,more flexiability and good matt effect on surface.  
Similar to TPR we have four grades in TR compound also for detailed techincal Data, Click the below stated link:-
More flexible like rubber
Matt effect on surface