A method for making an article of manufacture comprising: thermoforming a film comprising a reactor grade copolyester comprising: an acid residue moiety comprising: greater than 70 mole % terephthalic acid; and from 0 to 30 mole % of a modifying acid selected from the group consisting of isophthalic acid, adipic acid, azelaic acid, succinic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, and mixtures thereof, and a diol residue moiety comprising, from 75 to 95 mole % ethylene glycol; and from 5 to 25 mole % of a modifying diol selected from the group consisting of 1,4-cyclohexanedimethanol, diethylene glycol, neopentyl glycol, 2,2,4,4-tetramethylcyclobutane-1,3-diol, isosorbide and mixtures thereof, wherein the copolyester has a crystallinity defined by a minimum crystallization half time (t 1/2 min) of from at least 1.5 to 30 minutes, the measurement method of the crystallization half time being defined in the description, and wherein the sum of the mole percentages of component are based on 100 mole percent of the acid residue moiety and the sum of the mole percentages of component are based on 100 mole percent of the diol residue moiety, into a shape having first and second edges, placing said first and second edges in an overlapping position and, sealing said first and second edges together by subjecting the overlapping edges to an RF (radio frequency)-sealing energy using electromagnetic energy in a frequency range of from 0.1 to 300 MHz. thermoforming a film comprising a reactor grade copolyester comprising: an acid residue moiety comprising: greater than 70 mole % terephthalic acid; and from 0 to 30 mole % of a modifying acid selected from the group consisting of isophthalic acid, adipic acid, azelaic acid, succinic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, and mixtures thereof, and a diol residue moiety comprising, from 75 to 95 mole % ethylene glycol; and from 5 to 25 mole % of a modifying diol selected from the group consisting of 1,4-cyclohexanedimethanol, diethylene glycol, neopentyl glycol, 2,2,4,4-tetramethylcyclobutane-1,3-diol, isosorbide and mixtures thereof, an acid residue moiety comprising: greater than 70 mole % terephthalic acid; and from 0 to 30 mole % of a modifying acid selected from the group consisting of isophthalic acid, adipic acid, azelaic acid, succinic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, and mixtures thereof, and greater than 70 mole % terephthalic acid; and from 0 to 30 mole % of a modifying acid selected from the group consisting of isophthalic acid, adipic acid, azelaic acid, succinic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, and mixtures thereof, and a diol residue moiety comprising, from 75 to 95 mole % ethylene glycol; and from 5 to 25 mole % of a modifying diol selected from the group consisting of 1,4-cyclohexanedimethanol, diethylene glycol, neopentyl glycol, 2,2,4,4-tetramethylcyclobutane-1,3-diol, isosorbide and mixtures thereof, from 75 to 95 mole % ethylene glycol; and from 5 to 25 mole % of a modifying diol selected from the group consisting of 1,4-cyclohexanedimethanol, diethylene glycol, neopentyl glycol, 2,2,4,4-tetramethylcyclobutane-1,3-diol, isosorbide and mixtures thereof, wherein the copolyester has a crystallinity defined by a minimum crystallization half time (t 1/2 min) of from at least 1.5 to 30 minutes, the measurement method of the crystallization half time being defined in the description, and wherein the sum of the mole percentages of component are based on 100 mole percent of the acid residue moiety and the sum of the mole percentages of component are based on 100 mole percent of the diol residue moiety, into a shape having first and second edges, placing said first and second edges in an overlapping position and, sealing said first and second edges together by subjecting the overlapping edges to an RF (radio frequency)-sealing energy using electromagnetic energy in a frequency range of from 0.1 to 300 MHz.