The use of polymer mixtures comprising: A) from 15 to 50% by weight, based on components A and B, of a biodegradable, aliphatic-aromatic polyester with MFR (190°C/2.16 kg in accordance with ISO 1133) of from 40 to 150 g/10 min comprising: i) from 40 to 70 mol%, based on components i to ii, of one or more dicarboxylic acid derivatives or dicarboxylic acids selected from the group consisting of: succinic acid, adipic acid, sebacic acid, azelaic acid, and brassylic acid; ii) from 60 to 30 sol%, based on components i to ii, of a terephthalic acid derivative; iii) from 98 to 100 mol%, based on components i to ii, of a C 2 -C B -alkylenediol or C 2 -C 6 -oxyalkylenediol; iv) from 0 to 2% by weight, based on the total weight of components i to iii, of a chain extender and/or branching agent selected from the group consisting of: a di- or polyfunctional isocyanate, isocyanurate, oxazoline, epoxide, and carboxylic anhydride, and/or of an at least trihydric alcohol, or of an at least tribasic carboxylic acid; B) from 50 to 85% by weight, based on components A and B, of polylactic acid with MFR (190°C/2.16 kg in accordance with ASTM D1238) of from 5 to 50 g/10 min, C) from 0 to 40% by weight, based on the total weight of components A to D, of an organic filler selected from the group consisting of: native or plastified starch, natural fibers, and wood flour, and/or of an inorganic filler selected from the group consisting of: chalk, calcium carbonate, graphite, gypsum, conductive carbon black, iron oxide, calcium chloride, dolomite, kaolin, silicon dioxide (quartz), sodium carbonate, titanium dioxide, silicate, wollastonite, mica, montmorillonite, talc powder, glass fibers, and mineral fibers, and D) from 0 to 3% by weight, based on the total weight of components A to D, of at least one stabilizer, nucleating agent, lubricant and release agent, surfactant, wax, antistatic agent, antifogging agent, dye, pigment, UV absorber, UV stabilizer, or other plastics additive; for producing cartridges, pipettes, cuvettes or pipette holders. A) from 15 to 50% by weight, based on components A and B, of a biodegradable, aliphatic-aromatic polyester with MFR (190°C/2.16 kg in accordance with ISO 1133) of from 40 to 150 g/10 min comprising: i) from 40 to 70 mol%, based on components i to ii, of one or more dicarboxylic acid derivatives or dicarboxylic acids selected from the group consisting of: succinic acid, adipic acid, sebacic acid, azelaic acid, and brassylic acid; ii) from 60 to 30 sol%, based on components i to ii, of a terephthalic acid derivative; iii) from 98 to 100 mol%, based on components i to ii, of a C 2 -C B -alkylenediol or C 2 -C 6 -oxyalkylenediol; iv) from 0 to 2% by weight, based on the total weight of components i to iii, of a chain extender and/or branching agent selected from the group consisting of: a di- or polyfunctional isocyanate, isocyanurate, oxazoline, epoxide, and carboxylic anhydride, and/or of an at least trihydric alcohol, or of an at least tribasic carboxylic acid; i) from 40 to 70 mol%, based on components i to ii, of one or more dicarboxylic acid derivatives or dicarboxylic acids selected from the group consisting of: succinic acid, adipic acid, sebacic acid, azelaic acid, and brassylic acid; ii) from 60 to 30 sol%, based on components i to ii, of a terephthalic acid derivative; iii) from 98 to 100 mol%, based on components i to ii, of a C 2 -C B -alkylenediol or C 2 -C 6 -oxyalkylenediol; iv) from 0 to 2% by weight, based on the total weight of components i to iii, of a chain extender and/or branching agent selected from the group consisting of: a di- or polyfunctional isocyanate, isocyanurate, oxazoline, epoxide, and carboxylic anhydride, and/or of an at least trihydric alcohol, or of an at least tribasic carboxylic acid; B) from 50 to 85% by weight, based on components A and B, of polylactic acid with MFR (190°C/2.16 kg in accordance with ASTM D1238) of from 5 to 50 g/10 min, C) from 0 to 40% by weight, based on the total weight of components A to D, of an organic filler selected from the group consisting of: native or plastified starch, natural fibers, and wood flour, and/or of an inorganic filler selected from the group consisting of: chalk, calcium carbonate, graphite, gypsum, conductive carbon black, iron oxide, calcium chloride, dolomite, kaolin, silicon dioxide (quartz), sodium carbonate, titanium dioxide, silicate, wollastonite, mica, montmorillonite, talc powder, glass fibers, and mineral fibers, and native or plastified starch, natural fibers, and wood flour, and/or of an inorganic filler selected from the group consisting of: chalk, calcium carbonate, graphite, gypsum, conductive carbon black, iron oxide, calcium chloride, dolomite, kaolin, silicon dioxide (quartz), sodium carbonate, titanium dioxide, silicate, wollastonite, mica, montmorillonite, talc powder, glass fibers, and mineral fibers, and D) from 0 to 3% by weight, based on the total weight of components A to D, of at least one stabilizer, nucleating agent, lubricant and release agent, surfactant, wax, antistatic agent, antifogging agent, dye, pigment, UV absorber, UV stabilizer, or other plastics additive;