ASTM F1925-22

1.1''This specification covers virgin semi-crystalline poly(l-lactide) or poly(d-lactide) homopolymer resins intended for use in surgical implants. This specification also covers semi-crystalline resins of l-lactide copolymerized with other bioabsorbable monomers including, but not limited to, glycolide, d-lactide, and dl-lactide. The poly(l-lactide) or poly(d-lactide) based homopolymers and copolymers covered by this specification possess lactide segments of sufficient length to allow potential for their crystallization upon annealing.

1.2''Since poly(glycolide) is commonly abbreviated as PGA for poly(glycolic acid) and poly(lactide) is commonly abbreviated as PLA for poly(lactic acid), these polymers are commonly referred to as PGA, PLA, and PLA:PGA resins for the hydrolytic byproducts to which they respectively degrade. PLA is a term that carries no stereoisomeric specificity and therefore encompasses both the amorphous atactic/syndiotactic dl-lactide based polymers and copolymers as well as the isotactic d-PLA and l-PLA moieties, each of which carries potential for crystallization. Inclusion of stereoisomeric specificity within the lactic acid based acronyms results in the following: poly(l-lactide) as PlLA for poly(l-lactic acid), poly(d-lactide) as PdLA for poly(d-lactic acid), and poly(dl-lactide) as PdlLA for poly(dl-lactic acid).

1.3''This specification is applicable to lactide-based polymers or copolymers that possess isotactic polymeric segments sufficient in size to carry potential for lactide-based crystallization. Such polymers typically possess nominal mole fractions that equal or exceed 50'''% l-lactide. This specification is particularly applicable to isotactic-lactide based block copolymers or to polymers or copolymers synthesized from combinations of d-lactide and l-lactide that differ by more than 1.5 total mole percent (1.5'''% of total moles). This specification is not applicable to lactide-co-glycolide copolymers with glycolide mole fractions greater than or equal to 70'''% (65.3'''% in mass fraction), which are covered by Specification F2313. This specification is not applicable to amorphous polymers or copolymers synthesized from combinations of d-lactide and l-lactide that differ by less than 1.5 total mole percent (1.5'''% of total moles) as covered by Specification F2579.

1.4''This specification covers virgin semi-crystalline poly(lactide)-based resins able to be fully solvated at 30'''''C by either methylene chloride (dichloromethane) or chloroform (trichloromethane). This specification is not applicable to lactide:glycolide copolymers that possess glycolide segments sufficient in size to deliver potential for glycolide-based crystallization, thereby requiring fluorinated solvents for complete dissolution under room temperature conditions (see Specification F2313).

1.5''Within this specification, semi-crystallinity within the resin is defined by the presence of a DSC (differential scanning calorimetry) crystalline endotherm after annealing above the glass transition temperature. While other copolymeric segments may also crystallize upon annealing (for example, glycolide), specific characterization of crystalline structures other than those formed by lactide are outside the scope of this specification.