Method of making preform and container with crystallized neck finish

A method of making a preform by molding, the molding steps comprising:

• introducing at least one first thermoplastic material into a first mold to form during a first molding step while under first molding conditions a substantially crystallized and opaque first portion of a preform, the first portion being substantially a neck finish of the preform, the first molding conditions including a first melt temperature and a first mold temperature, the first melt temperature being selected to achieve crystallization of the first thermoplastic material in the first mold, and the first mold temperature being selected to achieve the substantially crystallized and opaque first portion;
• transferring the first portion of the preform to a second mold;
• and
• introducing at least one second thermoplastic material into the second mold to form by a second molding step while under second molding conditions different from the first molding conditions a substantially amorphous and transparent second portion of the preform, the second portion being substantially a body-forming portion of the preform, the second material having a relatively low crystallization rate compared to the first material, and the second molding conditions including a second melt temperature and a second mold temperature selected to achieve the substantially amorphous and transparent second portion, the second molding conditions further allowing maintenance of compressive forces to bond the first and second portions;
• and
• wherein during the first molding step a first molding core is positioned in the first mold for forming the first preform portion on the first core, and during the second molding step the first core and first preform portion are transferred to the second mold for forming the second preform portion over the first core.