oxygen permeability


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oxygen permeability 

The degree to which a polymer allows the passage of a gas or fluid. Symbol: Dk. Oxygen permeability (Dk) of a material is a function of the diffusivity (D) (that is the speed at which oxygen molecules traverse the material) and the solubility (k) (or the amount of oxygen molecules absorbed, per volume, in the material). Values of oxygen permeability (Dk) typically fall within the range 10-150 ✕ 10−11 (cm2 ml O2)/(s ml mmHg). A semi-logarithmic relationship has been demonstrated between hydrogel water content and oxygen permeability. Unit: Barrer.The International Organization for Standardization (ISO) has specified the permeability of contact lenses using the SI unit hectopascal (hPa) for pressure. Hence Dk = 10−11 (cm2 ml O2) /(s ml hPa). The former unit can be converted to this new SI unit by multiplying it by the constant 0.75. The ISO has established a classification of contact lens materials based on a range of values of oxygen permeability Dk. Group 1: 1-15; group 2: 16-30; group 3: 31-60; group 4: 61-100; group 5: 101-150; group 6: 151-200; group 7: 201-250; higher codes can be added in bands of 50. See Barrer; oedema; equivalent oxygen pressure; critical oxygen requirement; refractometer.
References in periodicals archive ?
In-situ neutron-diffraction experiments can establish a direct connection between the evolution of crystal structure in a material with property response, such as oxygen permeability.
Fletcher has observed that the oxygen permeability of a Saranex liner will vary because of spring tension in the capper heads.
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At the same time, oxygen permeability must be low enough to prevent oxidation.
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Martin Sommer oxygen permeability experiment used measure the rate of flow of oxygen.
As shown in table 1, oxygen permeability of linear low density polyethylene (Attane 4201) is 279 cc-mm/[m.
The influence of BA on the density, compressive strength, flexural strength, water absorption and oxygen permeability was investigated.
As a result secure packaging with minimal oxygen permeability is required for this operation so that the meat can survive long maturing times of up to 40 days under optimum storage conditions without suffering any loss of quality.
Products with better moisturising and oxygen permeability will be favoured by health-concerned consumers, with a greater number of consumers trading up from traditional lenses to weekly/monthly lenses or from weekly/monthly disposable lenses to daily disposable lenses.
The inclusion of hydrophobic silicone in materials improves oxygen permeability dramatically, but tends to make them more prone to organic deposits picked up from the tears and environment, particularly lipids which can affect lens wettability, comfort and vision.
The 8700 Oxygen Permeation Analyser is extremely versatile, capable of measuring wide ranges of oxygen permeability.