Packaging for terminally sterilized medical devicesPart 7: Adhesive coated paper for low temperature sterilization processes — Requirements and test methods BSI Standards Publication...
Apparatus
B.1.1 An ultraviolet light source and light meter with a range of wavelength of 315 nm to 380 nm
B.1.2 Flat dish, approximately 200 mm x 150 mm x 15 mm
B.1.5 Powder dispenser, with a sieve of nominal aperture size between 0,125 mm and 0,150 mm at one end and closed at the other.
Reagent
Dry indicator powder prepared as described below
Grind 20 g of sucrose using a mortar and sieve it through a mesh with an aperture size of 0.063 mm to 0.075 mm Dry the sieved sucrose in a desiccator with silica gel or in an oven at temperatures between 105 °C and 110 °C before mixing.
To prepare the dry indicator powder, mix 10 g of dry sucrose with 10 mg of sodium fluorescein, then pass the mixture through a sieve with a nominal aperture size of 0.063 mm to 0.075 mm five times Finally, transfer the resulting dry powder to the powder dispenser.
The dry indicator powder in the powder dispenser should be stored either in a desiccator or in an oven at 105 °C to 110 °C.
Procedure
To conduct the experiment, prepare 10 conditioned paper samples, each measuring 60 mm x 60 mm, and divide them into two groups of five, positioning one group with the 'wire-side' facing up and the other with the 'top-side' up Each sample should be folded twice at right angles, creating folds that are 10 mm high along two edges Fill a flat dish with purified water to a depth of 10 mm at the conditioning temperature, then activate the UV lamp, ensuring it reaches full output and adjusting its distance to achieve an irradiance of (300 ± 20) µW/cm² at the water level Lightly sprinkle indicator powder on the upper surface of a test piece and float it on the water beneath the UV light, recording the time taken for general fluorescence to appear Repeat this process for the remaining nine test pieces.
The water repellency of the paper is considerably influenced by the temperature of the water which shall be maintained within the specified limits (23 ± 1) °C.
Repeatability and reproducibility
See Annex G for repeatability and reproducibility of the test method.
Test report
The test report must contain the mean penetration time in seconds for each side of the paper, along with the product identification, test-house details, and date upon request Additionally, it should reference the normative test method used.
Method for the determination of pore size
Principle
The pressure needed to push air bubbles through the tiny openings of a liquid-wetted material, which has a liquid film on its surface, is measured This pressure, along with the liquid's known surface tension, allows for the estimation of the size of the material's interstices.
Test liquid
The ideal test liquid must fully wet the paper, possess low solvent power for proofing materials, and prevent fiber swelling Additionally, it should maintain consistent surface tension, be non-toxic, exhibit low flammability, produce minimal foaming, and be cost-effective.
NOTE Ethanol R has been found to be suitable.
Apparatus
The apparatus, illustrated in Figure C.1, consists of several key components: a testing head (1) made of a suitable material like brass, which securely clamps the specimen (a) using a clamping ring (b) and screw (c), and features a synthetic rubber gasket (d) with a 50 mm internal diameter to ensure a proper seal Additionally, it includes a pressure measuring device, a stop-valve to direct air to the testing head, and a variable flow valve to control the pressure rise rate in (1) Another stop-valve directs air to the pressure measuring device, while an air reservoir with a capacity of approximately 2.5 liters is connected to (1) to maintain a sufficient air flow rate, preventing pressure drop due to air loss when bubbling occurs Finally, the system is supplied with air.
C.3.2 Using the apparatus shown in Figure C.1 the test is conducted as follows:
To initiate the test, activate the air supply and open valve “3” to channel air to the test head through reservoir “6.” Adjust valve “4” to achieve the desired pressure rise rate, keeping stop-valve “5” open throughout the testing process Once the first bubble is observed in the test material, close valve “5” to record the pressure indicated on measuring device “2.”
2 pressure measuring device b clamping ring
4 variable blow valve set d rubber gasket
Figure C.1 — Diagrammatic representation of the apparatus for the determination of the pore size
C.3.3 Apparatus for measurement of the equivalent pore size, having the following characteristics: a) Means shall be provided for clamping the specimen of material in such a manner that:
2) a circular area of the material 50 mm in diameter will be subjected to steadily increasing air pressure on the lower face;
3) no leakage of the test liquid occurs during the test period;
4) the specimen does not slip in the clamps
Clamps should be made with a resilient material that is resistant to the test liquid, and using a suitable grade of synthetic rubber can help achieve the correct clamping conditions for certain apparatus Additionally, the air pressure should increase at a rate of 2 kPa/min to 2.5 kPa/min, equivalent to 200 mm to 250 mm of water head per minute.
A pressure measuring device connected to the test head must be calibrated in kilopascals or millimeters of water head, with a suitable range to ensure accurate measurements Notably, 2.1 mm of water head is equivalent to 9.80655 Pa.
A pressure measuring device capable of measuring up to 6 kPa (600 mm head of water) is suitable for most materials For close materials such as ventile, clean room overalls, and theatre clothing and drapes, a device that measures pressures up to 10 kPa (1 m head of water) is recommended.
Preparation of test specimens
Minimize handling of the material after receipt, avoiding sharp folds, ironing, or any treatment beyond conditioning Cut test specimens into manageable shapes and select them from various locations in the material, ensuring they are free from creases to accurately represent the material's properties.
NOTE For most types of apparatus, it is convenient to cut specimens from the material in the form of
Unless otherwise stipulated, test 10 specimens from any sample of material submitted.
Procedure
C.5.1 Conduct the test in the standard atmosphere for testing specified in EN 20187
C.5.2 Determine the surface tension of the test liquid by any convenient method to the nearest
NOTE Within the range of the standard atmosphere, the surface tension of Ethanol R usually lies between
22 mN/m and 24 mN/m, with a temperature coefficient of - 0,005 mN/(m ⋅ K) The Wilhelmy stalagmometer, single and double capillary methods have all been found satisfactory for measuring surface tension
Soak the conditioned specimen in approximately 15 mm of test liquid within a glass dish for at least 3 minutes After soaking, use forceps to remove the specimen and secure it on the testing head Apply a few milliliters of the test liquid to the material's surface, ensuring it is completely covered after slight bulging occurs due to the pressure from below Finally, record the temperature of the test liquid at this point.
To effectively test very porous materials, it is beneficial to allow air pressure to build up beneath the specimen, causing it to bulge before completely covering the surface with the test liquid.
Under rising air pressure, bubbles begin to form at various locations on the upper surface of the specimen It is essential to monitor the specimen continuously as the pressure increases and to accurately note the pressure, measured to the nearest millimeter, at which the first bubble emerges on the upper surface.
C.5.5 Test further specimens until the requisite number of results is obtained.
Result
Calculation and expression of results
Calculate the equivalent pore radius r in micrometres for each specimen by means of the formula:
The surface tension (T) of the test liquid is measured in mN/m at the test temperature The acceleration due to gravity (g) is expressed in mm/s², while the density of water (ρ) at the test temperature is given in mg/mm³ Additionally, the bubble pressure (p) is represented in millimeters of water head.
Calculate the mean pore radius and express the result as pore diameter
NOTE 1 The error introduced by taking ρ = 1 mg/mm 3 for the relative density of water at the temperature of the standard atmosphere for testing is small compared with the variability of the test results
NOTE 2 Similarly, although g is known to vary about 0,5 % from place to place, the error introduced by assuming a constant value of 9 810 mm/s 2 is small compared with the variability of the test.
Derivation of formula for calculation of equivalent pore radius
For a cylindrical tube, the pressure p in Pascals, necessary to force liquid through, is given by the following formula:
T is the surface tension of liquid, in N/m;
Q is the contact angle at liquid-solid-air interface, in degrees; r is the radius of tube, in metres
This is the Laplace formula (see [4])
The contact angle is very difficult to measure and therefore a liquid is chosen which completely wets the material, thus cos Q = 1 and the formula becomes: p 2T
This formula is the same as the simplified formula given in C.6.1
The pressure is normally measured in millimetres head of water, because either a water manometer is used, or the pressure measuring device is calibrated in millimetres head of water
Thus p p= ⋅ ⋅ b ρ g (C.5) where p b is the head of water, in millimetres head of water; ρ is the density of water, in mg/mm 3 ; g is the acceleration due to gravity, in mm/s 2
Repeatability and reproducibility
See Annex G for repeatability and reproducibility of the test method.
Test report
The test report must provide the equivalent pore diameter in micrometres for each specimen, along with the mean pore diameter for the sample It should also detail any deviations from the specified procedure Upon request, the report must include the identification of the product being tested, the test-house, and the date of the test, as well as the normative reference for the test method.
Method for the determination of regularity of seal adhesive coatings on paper
Principle of the method
A dye solution is applied to the surface of the adhesive coating and the excess wiped off Visual examination of the coloured surface determines the regularity of the coating.
Apparatus
a) Cotton gauze swabs; b) Cotton cloth; c) Dye solution prepared by dissolving 5 g Malachite Green in 1 000 ml of 10/90 (V/V) methylated spirit/water mixture.
Procedure
Apply the dye solution to the coated paper surface using swabs, and promptly remove any excess with a clean cotton cloth This process allows for a visual inspection of the coating's uniformity, as the dye will stain any uncoated areas.
Test report
The test report must contain the results of the visual examination, identification details of the product being tested, the test house, and the date upon request, as well as the normative reference for the test method used.
Method for the determination of mass per unit area of uncoated paper and adhesive coating
Units
All results shall be reported in units of grams per square metre (g/m 2 ).
Principle of the method
Samples of known areas are cut out and weighed The adhesive coating is removed by extracting in a solvent The paper is dried, allowed to condition and then re-weighed
The difference in mass between the original and the extracted samples is determined and the appropriate factor is applied to obtain the mass of the extracted coating.
Apparatus
Recommended dimensions 100 mm x 100 mm – factor 100;
E.3.3 Cutting tool with sharp blade or alternatively a combined circular cutter
E.3.4 Continuous extraction apparatus e.g soxhlet comprising an extraction tube of approximately
100 ml volume and a reflux flask of 250 ml volume without the use of a cartridge
E.3.5 Electric thermostatically controlled flask heater sited in fume cupboard
E.3.6 Fume cupboard with extraction fan and ventilation
E.3.7 Analytical balance capable of measuring accurately to 0,1 mg
Procedure
E.4.1 Allow the test sample to condition
E.4.2 Place the material to be tested on the cutting sheet
E.4.3 Place the template on the material, position firmly and cut around the edges with the cutting tool – alternatively use the circular cutter
E.4.4 Cut out 10 samples in such a way as to get a good coverage across and along the sheet being tested
E.4.5 Identify each sample by numbering with a pencil
E.4.6 Weigh the samples individually on the analytical balance and record the mass of each alongside its number
E.4.7 Add 150 ml of the solvent to the flask, extract the samples for 1 h regulating the heating so that the solvent in the extraction tube is renewed every 5 min
E.4.8 Remove the samples with tongs
E.4.9 Dry off any solvent with a warm air current
E.4.10 Allow the samples to recondition for 24 h at (23 ± 2) °C and (50 ± 5) % relative humidity
E.4.11 Reweigh the samples against their identification as in E.4.5 and E.4.6.
Results
Calculate the mass per square metre of the adhesive coating by the following formula:
The equation \$m_3 = m_1 \times f_t - m_2 \times f_t\$ defines the relationship between the initial mass of a sample (\$m_1\$), the mass after extraction and reconditioning (\$m_2\$), and the mass of the adhesive coating removed (\$m_3\$) in grams per square meter Here, \$f_t\$ represents the template factor, with \$m_1 \times f_t\$ indicating the mass per square meter of coated paper and \$m_2 \times f_t\$ representing the mass per square meter of uncoated paper.
Test report
The test report must contain essential details, including the maximum, minimum, and average masses for both uncoated paper and adhesive coating Additionally, upon request, it should provide the product identification, test-house identification, and the date of the test Lastly, the report must specify the standard number utilized during the testing process.
Method for the determination of seal strength and mode of specimen failure
Principle of the method
The adhesive coating is applied to a designated sealing substrate under controlled conditions The seal strength is evaluated by cutting a strip at a 90° angle through the seal and testing its tensile strength using a machine that complies with EN ISO 11607-1:2009+A1:2014, Annex B.
Test method
F.2.1 Test method: see EN ISO 11607-1:2009+A1:2014, Annex B
F.2.2 Sealing substrate: The specification of the material used shall be documented
NOTE It is suggested to use e.g 17 g/m 2 polyester coated with 34 g/m 2 polyethylene or similar
Preparation of test-specimen
F.3.1 Set the sealer to the conditions specified by the manufacturer (see Clause 5)
NOTE In some cases specific laboratory sealing equipment and sealing substrates require adjustment of sealing conditions to achieve the required results
F.3.2 Make test seals by sealing together the adhesive coated side of the paper with the sealing side of the sealing substrate
F.3.3 Cut five strips 15 mm wide following sampling instructions of EN ISO 11607-1:2009+A1:2014,
Procedure
According to EN ISO 11607-1:2009+A1:2014 guidelines, seals should be pulled apart at a grip separation rate of 200 mm/min, and the average force must be recorded from the middle of the measured seal profile curve, excluding 10% from each end of the curve.
Results shall be reported in units N/15mm In order to produce comparable data, it is recommended to use EN ISO 11607-1:2009+A1:2014, Annex B (supported tail of the specimen)
NOTE Gripping the tail end during manual support can negatively influence the results
Visually inspect the film's seal patterns to identify the mode of failure, such as adhesive or cohesive peel, and examine the paper's surface for signs of delamination or fiber tear.
The test procedure must document essential elements such as sealing temperature, pressure, and time, along with the configuration of the sealing device and the orientation of the sample within both the sealing device and the testing machine.
Test report
The test report must include essential details such as the product identification, sealing substrate, test laboratory identification, and the date of testing It should specify the seal strength measured according to F.4.1 for each sample, reported in N/15 mm, with separate results for machine and cross direction samples Additionally, the report must indicate the mode of failure as per F.4.2, noting whether delamination or fiber tear occurred It should also clarify if the test was conducted with the tail unsupported or supported, along with any other relevant specifications Finally, the report must reference the standards utilized during the testing process.
Repeatability and reproducibility of test methods
The precision of the following test methods have been assessed by a Round Robin Test protocol in 2010 and 2011, conducting a precision experiment as described in ISO 5725-2:
Table G.1 summarizes core conditions of interlaboratory testing Table G.2 summarizes the significance of results
Laboratories Number of test runs
Replication Number of sample materials Type of materials
Pore size 7 9 10 4 Plain paper, creped paper
Water repellency 3 16 10 3 Fine creped paper, Plain paper, creped paper
Table G.2 — Precision of test methods - Significance of results
NOTE Table G.2 has been adopted from the publication (see Bibliography) accordingly Detailed information concerning the assessment, i.e objective, methods, results, analysis and discussion, conclusions and recommendations, are published (see [5])
[1] EN 1041, Information supplied by the manufacturer of medical devices
[2] EN ISO 11607-2, Packaging for terminally sterilized medical devices - Part 2: Validation requirements for forming, sealing and assembly processes (ISO 11607-2)
[3] ISO 5725-2, Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method
[4] ADAMSON A W., Physical chemistry of surfaces, New York, J Wiley, 1976
[5] BERRY C.W., HARDING L Validation of Test Methods for Characterizing and Specifying Materials Used in the Construction of Sterilization Packaging Packag Technol Sci 2012
[6] Council Directive 93/42/EEC of 14 June 1993 concerning medical devices