ASTM International

Standard Specification for Amorphous Poly(lactide) and Poly(lactide-co-glycolide) Resins for Surgical Implants
 N F2579

Annotation

This specification covers virgin amorphous poly(lactide) homopolymer and poly(lactide-co-glycolide) copolymer resins intended for use in surgical implants. The poly(DL-lactide) homopolymers covered by this specification are considered to be amorphous (that is, void of crystallinity) and are polymerized either from meso-lactide or from equimolar (racemic) combinations of D-lactide and L-lactide. The poly(DL-lactideco- glycolide) copolymers covered by this specification are also considered to be amorphous and are co-polymerized from a combination of glycolide and either meso-lactide or racemic quantities of D-lactide and L-lactide, and typically possess nominal mole fractions that equal or exceed 50 % lactide.

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 DLlactide- based polymers and copolymers as well as the isotactic D-PLA and L-PLA moieties, each of which carries potential for crystallization. Therefore, specific reference to DL-PLA is essential to appropriately differentiate the amorphous atactic/ syndiotactic DL-lactide-based polymers and copolymers covered by this specification. Thus, 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(DLlactide) as PDLLA for poly(DL-lactic acid).

This specification covers virgin amorphous 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-based polymers or copolymers that possess isotactic polymeric segments sufficient in size to carry potential for lactide-based crystallization, which are covered by Specification F1925 and typically possess nominal mole fractions that equal or exceed 50 % L-lactide. This specification is not applicable to lactide-co-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. This specification is specifically 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 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).