Moisture permeation

Primary interest was in the barrier properties obtained from plasma organo-silicones and from inorganic "SIN" coatings. Spectral grade HMDSO was used in the former case, while mixtures of SiH and NH were used to produce the SIN structures. The substrate in much or the work was DuPont Kapton type H polylmide film, 51 pm thick. Substrate temperatures extended to 450 C, as described earlier (6). The thickness of plasma-polymer deposits was about 0.5 pm. Moisture permeation was evaluated by the routine of ASTME-96-53 T (water vapor transmission of materials in sheet form). Additional, more precise data, were obtained with both a Dohrmann Envirotech Polymer Permeation Analyser, modified as previously described (6), and a Mocon "Permatran W" moisture permeation apparatus. 

To address protection, use of tests (see Attachment A) for light transmission, moisture permeation, microbial limits, and sterility are generally considered sufficient. Testing for properties other than those described above (e.g., gas transmission, solvent leakage container integrity) may also be necessary. 

Testing on an assembled container closure system is usually performed by the applicant (or a testing laboratory commissioned by the applicant), and the test results are provided in the application. Such tests may include vacuum-leak testing, moisture permeation, and weight loss or media fill. Testing on an individual packaging component is typically performed by the manufacturer of the component and is reported via a DMF (see Section V). 

Another critical factor in preventing blistering is the moisture permeation rate, which is the determinant of FGD rubber life. This permeation rate is directly proportional to the temperature gradient across the rubber lining, the so-called "coldwall" effect. 

When more than one plastic resin is used to fabricate bottles, it is necessary to demonstrate the equivalency of the container produced using the different resins. In addition, comparative data derived from light transmission, chemical resistance, extractables, and moisture permeation/vapor transmission tests described in the USP should be provided as applicable to the type of product. (For example, moisture permeation for an aqueous dosage form would not be necessary). Whereas the compendia discuss these tests only in the context of polyethylene, the guideline makes no distinction as to the resin used. It also should be verified that copies of letters authorizing FDA reference to appropriate DMFs from manufacturers of the resins used to fabricate bottles and from the bottle fabricator s), if available, are included. Although most resin suppliers include information on extractables data in their DMFs, it should be pointed out that fabricators may have to add release agents or other additives not covered by extractables data in the DMF of the resin supplier. 

The addition of various corrosion inhibitors to the epoxy encapsulant formulation to prevent corrosion was also evaluated (8). This procedure basically adds compounds or complexing agents to neutralize or "getter corrosion accelerating impurities or adds hydro-phobic agents to reduce the moisture permeation of the plastic. 

The measurement of the moisture permeation allows a class to be assigned. This class is denoted by a letter from A to D that corresponds to the level of moisture permeability of the container. Class A containers are good moisture barriers whereas Class D containers allow substantial water volume to pass through. 

Okhamafe AO, York P. Moisture permeation mechanism of some aqueous-based film coats. / Pharm Pharmacol 1982 34 (Suppl.) 53P. 

To investigate moisture permeation phenomenon dependent on the passivation materials, a humidity-temperature test was carried out at 65 °C and 90 % relative humidity (RH). We compared the electrical performances of the SiNx-passivated and the acryl-passivated TFTs after 3-hour humidity-temperature test. Fig. 9 shows transfer curves before and after the humidity-temperature test. We could not find any significant shift of the threshold voltage in the SiNx-passivated TFT. The SiNx passivation did not allow moisture to p>enetrate into TFT. On the other hand, threshold voltage shifted as large as 28 V for the aayl-passivated TFT. The acrylic polymer could not keep the moisture from permeating. Other researchers have reported the effect of moisture on a-Si FI TFT. 

Protection (by each component and/or the container closure system, as appropriate) light exposure, reactive gases (e.g., oxygen), moisture permeation, solvent loss or leakage, microbial contamination (sterility/contamer integrity, increased bioburden, microbial limits), filth, other... 

A novel method of improving the reliability of plastic packaged semiconductor devices has been developed. One of the major causes of failure in such devices is corrosion due to moisture permeating through the encapsulant, transporting small amounts of ionic impurity and condensing at the chip surface to form an aggressive electrolyte. 

It can be concluded that a series of overwraps will significantly extend the shelf life of, for example, a moisture-sensitive product as moisture permeation is considerably reduced and/or a low barrier primary material may give adequate protection. This counters any need for an improved pack as found under the ICH 40°C 75% RH conditions. 

For solid products the risk of migration is low and therefore interaction studies are not required over and above the normal stability test results. For semi-solid products it is necessary to look particularly at the migration of additives, vapour permeation and the effects of the product on the physical parameters of the pack. For liquid products the migration potential for the specific formulation is required, and the determination of active ingredient content under simulated use, along with extractives data is required for parenteral and ophthalmic products. Moisture permeation is important, particularly for solid products packaged in blister packs. 

The material therefore readily absorbs moisture and must be effectively dried prior to moulding, otherwise a hazy or milky appearance may result. Polyacrylonitriles have a relatively low heat distortion temperature (around 75°C), hence they have limitations for products requiring a hot fill. The material is suitable for thermoforming operations but its relatively high moisture permeation is likely to restrict ultimate usage. The presence of acrylonitrile residues also placed the material under a cloud with the FDA, but use is now accepted provided acrylonitrile monomer does not exceed 0.1 ppm. Nitrile copolymers are usually copolymerised with methyl acrylate together with small quantities of butadiene/acrylonitrile rubbers. 

Plasticised PVC may sometimes seem a misnomer, as the plasticiser content can occasionally be greater than the PVC. Plasticisation also reduces chemical resistance and increases gas and moisture permeation. Typical plasticisers used include adipates, citrates, sebacates, phosphates and phthalates, e.g. di-iso-octyl adipate, acetyl-tri-n butylcitrate, di-octyl phthalate (DOP). Polymeric plasticisers and urethanes are also used. Plasticised PVCs are soft and very flexible (see IV bag usage). 

Fillers, pigments, opacifiers, etc. may increase or decrease diffusion and permeation. This is also true of solvent residues which may increase permeation to similar organictype solvents. Titanium dioxide usually reduces permeation white talc and chalk as used in polypropylene will usually increase moisture permeation. 

This is the newest coating process to emerge and has been applied to PET and PP films. The coating shows high hardness, transparency and impermeability, reducing moisture permeation by 40-60x and oxygen by up to lOOx. In the process of manufacture acetylene is ionised in a vacuum chamber, releasing carbon onto a film. 

Since many IV packs are overwrapped (some prior to autoclaving), usually to reduce gaseous or moisture permeation factors, this may also add to the overall pack integrity and needs evaluation before and after autoclaving. 

Physical Properties. Some properties of specific interest in the coating field are adhesion weatherability moisture permeation and absorption inertness to chemical environments color and service temperature range. Bitumens exhibit good adherence to almost any surface. Coatings with excellent weathering properties can be obtained by proper selection of the bitumen and formulation with other materials. 

The moisture permeation rate of a sugar coating composed of sucrose, talc, and other minor components was reported to conform to Fick s equation.729 The permeation rate appeared to be rate-controlling for moisture adsorption by sugar-coated tablets. 

Moisture adsorption of dosage forms inrelation to the moisture permeation ofpackaging will be described in Section4.3.1. 

The sealants cure from the outside in as the moisture in the air contacts the sealant and promotes crosslinking. A "skin" will form on the sealant surface, and this skin will proceed to become tack-free with soft, pliable, uncured sealant below it. The cure rate will then slow, since it is dependent on moisture permeation through the exterior skin. The skin will increase in thickness until the entire sealant bead has cured. 

Clay nanocomposites are also being developed as barrier coatings for film and for containers. The nanocomposite is deposited on the film from a solution of PVOH/ EVOH copolymer in a mix of water and isopropyl alcohol which has been used in a supersonic dispersion system to nano-disperse 7 nm diameter silica and titanium dioxide particles. The ratio of polymer to silica depends on the barrier properties required. Typical microgravure equipment can be used to coat the solution onto a plastic substrate. The result reportedly is a transparent barrier coating which is superior to silica- and alumina-coated films, and is comparable to aluminum-coated materials. Oxygen permeability at a coating thickness of 2 pm is less than 1 cc/m d atm, and moisture permeation less than f g/m d. Costs are reported to be competitive with ceramic coatings [4]. 

The intermediate coats are used mainly for increasing the final thickness, and consequently hinder the moisture permeation... 

Figure 5.30 Moisture permeation through epoxy-sealed ceramic package. ...

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