ISO 15814 pdf download.Implants for surgery — Copolymers and blends based on polylactide — In vitro degradation testing
1 Scope
This International Standard is applicable to copolymers and/or blends based on polylactide, in bulk or processed forms, used for the manufacture of surgical implants. This International Standard describes methods for the determination of chemical and mechanical changes in the properties of these copolymers and/or blends under in vitro degradation testing conditions. The test methods specified in this International Standard are intended to determine the degradation rate and the changes in material properties of polylactide-based copolymers and/or blends with various comonomers (for example glycolid, trimethylene carbonate, ε-caprolactone) in vitro . These in vitro methods cannot be used to predict definitely the behaviour of these materials under in vivo conditions. The purpose of this International Standard is to compare and/or evaluate materials or processing conditions.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards. ISO 1 78:1 993, Plastics — Determination of flexural properties. ISO 1 80:1 993, Plastics — Determination of Izod impact strength. ISO 527-1 :1 993, Plastics — Determination of tensile properties — Part 1 : General principles. ISO 527-2:1 993, Plastics — Determination of tensile properties — Part 2: Test conditions for moulding and extrusion plastics. ISO 537:1 989, Plastics — Testing with the torsion pendulum. ISO 604:1 993, Plastics — Determination of compressive properties.
3 Terms and definitions
For the purposes of this International Standard, the terms and definitions given in ISO 1 3781 , ISO/TR 1 0993-9 and the following apply. 3.1 copolymer polymeric material which consists of different monomer units 3.2 blend polymeric material which consists of different polymers mixed intensively together 3.3 resorption loss of morphology and loss of mass
4 Degradation methods
4.1 General The initial values for the following tests shall be determined directly before starting the degradation test (time zero). The tests shall be carried out on the degraded samples at each test period. 4.2 Reagents and apparatus 4.2.1 Soaking solution (phosphate buffer solution; Sörensen buffer) For the in vitro degradation study, the test sample shall be immersed in a ”Sörensen” buffer solution (pH 7,4) consisting of potassium dihydrogenphosphate and disodium hydrogenphosphate in analytical water Grade 2 in accordance with ISO 3696.Salts used for the preparation of the buffer solution shall be of analytical grade and dried to constant mass. The minimum volume of the buffered solution used shall be 1 0 ml. The ratio of the volume, in millilitres, of buffer solution to the test sample mass, in grams, shall be greater than 30:1 . The buffer capacity shall be equal or greater than the maximum calculated acid concentration. The test sample shall be completely immersed in the soaking solution. 4.2.2 Inert plastic or glass container (e.g. bottle, jar, vial, etc.) capable of holding the test sample for each material and time period and the required volume of soaking solution. Each container shall be sealed against loss of solution by evaporation and to prevent microbial contamination. 4.2.3 Constant-temperature bath or oven capable of maintaining the sample containers at degradation temperature (37 ± 1 ) °C at any place for the specified test duration (for example circulating-air dryer). 4.2.4 pH-Meter, for controlling the pH value. 4.2.5 Analytical balance with an accuracy of 0,1 mg. 4.3 Control of the buffer solution 4.3.1 Changes in pH value The pH value shall be measured in two different containers at each test period. In extended test periods, the pH value shall be measured additionally in at least two containers every four weeks. If in one container the pH value has shifted beyond the limits, measure the value in all containers and adjust to pH 7,4 ± 0,3 using 0,1 mol/l NaOH solution.