The low thermal stability of polylactic acid (50 to 60 °C) should be increased via polymer modification or use of another suitable biopolymer. First of all, the reasons for the low thermal stability of polylactic acid should be identified and, with the aid of publications and information from material suppliers, qualified possibilities and additives for the modification of polylactic acid should be specified. Suitable recipes should be defined and test specimens produced, followed by an investigation considering the thermal (DSC, TGA, HDT) and mechanical parameters (Charpy impact strength, tensile testing, DMA) of each composition. The reference material was Polylactide IngeoTM Biopolymer 2003D (PLA2003D, NatureWorks LLC). 0.5, 1 and 2 wt-% of a chain-extending additive (BioAdimideTM 500 XT, Rhein Chemie Rheinau GmbH) were added to the reference material, a surface-effective additive (IncroMaxTM 100, Croda Europe Limited) was added in an amount of 0.2, 0.3, and 0.5 wt-%. Two compounds, MirelTM P4001 (Metabolix Inc.), a polyhydroxyalkanoate, and a modified polylactic acid-compound, DaniMer 42370 (DaniMer Scientific LLC), were also selected. Furthermore, blends of the two homopolymers PLLA and 1, 3 and 5 wt-% of PDLA (PLLA Synterra® 1510 and Synterra® PDLA 1010, Synbra Technology bv) were prepared. In addition, PLA2003D should be crosslinked using bridge molecules (TAIC 70, Kettlitz Chemie GmbH) and an UV-initiator (Irgacure® TPO, BASF SE). Tentatively, PLA2003D was blended with 1, 3, 5 and 10 wt-% of PDLA. As shown in DSC measurements, the reference material PLA2003D crystallizes very slowly. It does not form any crystalline fractions in the manufacturing process and as a result, it is completely amorphous at room temperature. Nevertheless, cold crystallization is noticeable in the heating mode. The result is the low heat resistance. The additives BioAdimide and IncroMax have no influence on the crystallinity and do not cause a higher thermal stability of PLA2003D. The UV-crosslinking of PLA2003D was not successful. The compounds Mirel P4001 and DaniMer 42370 are partially crystalline and classified as promising on the basis of DSC measurements and dynamic mechanical analysis. These expectations are lowered by their poor mechanical properties. The most promising recipes were the blend formulations composed of PLLA and PDLA. Their high crystallinity, the development of additional mechanical support giving stereo complexes, comparable mechanical properties as PLA2003D and the formation of a plateau of the storage modulus at about 400 MPa after the glass transition range, as the dynamic mechanical analysis showed, are good conditions for using these polymers at higher temperatures. The blends of PLA2003D and PDLA form, with increasing PDLA-amount, larger stereo complexes, but do not crystallize.