WHEATON Technical Data - page 13

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Technical Data, Glass
Autoclave Sterilization
Recommendations for Autoclavable Coated Containers
The suggested conditions for steam sterilization are 121°C (250°F) @ 15 psi for 20
minutes. Portions of the coating may absorb a small amount of water vapor and appear
cloudy after autoclaving, however, the cloudiness will disappear as the coating dries.
To speed clearing, glassware can be dried in an oven at 49 – 66°C (120 – 150°F).
Autoclaving effects on the coating will vary slightly due to equipment, container size and
configuration, procedure and frequency of procedure. It is recommended that containers
not be autoclaved touching each other to avoid possible sticking problems. Also, it is
recommended that the autoclave pressure be allowed to return to zero before removing
glassware. A sudden release of pressure may cause the coating to separate from the
glass and produce air pockets under the coating.
Evaluation of a sample is the best way to determine if the safety coating will work for
your application.
Recycling Safety Coated Containers
For after-use disposal, PVC safety coated containers create a unique situation in that
they are a composite package of glass and plastic. Depending on the application, there
are four ways to handle the disposal of coated containers:
In the laboratory or industrial setting, coated containers can be washed, dried and
reused, perhaps for the collection of hazardous waste in the laboratory.
For consumer pharmaceutical and cosmetic applications, coated glass containers should
be able to go into residential glass recycling collection. Coated glass makes up such a
small percentage of total glass collected that it should not present any recycling problems
(variations in state and county recycling programs make it difficult to generalize).
For large quantity industrial or laboratory applications, recycling coated glass containers,
as a whole, can create two problems: the grinding of the coated glass into cullet could
be difficult, and the PVC in the glass furnace might create organic chlorides in the glass
mixture that would affect the final pH of the glass. Also, if a hazardous material was
packaged in the containers, many recyclers do not want to accept the glass.
The plastic coating can be cut and peeled from the container and the glass and the
plastic jacket recycled, but for safety reasons this is not recommended. Both glass and
PVC are recyclable materials. Stripped coatings are recycled into garden hoses and
floor mats.
Safety Coated Containers
A plastisol coating was developed to contain glass fragments and allow for a controlled
release of the contents in the event of container breakage. The coating:
Adds impact, thermal shock and slip resistance
Contains glass - prevents flying fragments and cuts
Contains contents - reduces risk of chemical exposure and inhalation. Allows time
for proper disposal.
The coating material is plastisol, which is a dispersion of a fine particle size PVC resin
(polyvinyl chloride) in a plasticizer where stabilizers, fillers, modifiers, colorants and other
compounding ingredients may be added. When the plastisol is heated, the suspended
PVC particles begin to swell and absorb the surrounding liquid plasticizer. When the
temperature is increased to over 300°F, fusion of the particles occurs and the particles
coalesce into a homogeneous mass. The coating process is a heat-and-time related
process that determines coating weight and thickness and is controlled by machine line
speeds and oven temperatures. The more heat, the heavier the coating, and the slower
the line, the heavier the coating.
Non-autoclavable coated containers can be used successfully at 121°C (250°F) and
below. Do not use above 300°F or over direct heat or flame. The coating is not dry heat
sterlizable. Coating will yellow and burn with high heat exposure but will continue to
protect until black.
Labeling Adhesives for Coated Glass Containers
Labeling of plastisol coated glass containers has always been somewhat of a problem. It
is important to select a face stock and adhesive combination with the proper performance
characteristics for the intended product and application. It is recommended that prior
to the selection of any adhesive, the customer contact the adhesive manufacturer or
supplier and discuss the application requirements.
For on-line and pressure sensitive labeling of plastisol coated glassware, an acrylic based
adhesive with low rubber and vinyl content is recommended. Other label adhesives will
usually extract the plasticizer from the coating, become soft, bleed through the label and
eventually lose adhesion. Acrylics block the plasticizer extraction and allow the initial
adhesion to remain undisturbed. There are, however, many variations of acrylic based
adhesives and some are more effective than others. Adhesives are usually formulations
of several chemicals that are combined in a variety of ratios and available in many forms.
It is for these reasons, that accelerated age testing is advisable.
When selecting an adhesive for a specific application, consideration should be given to
the necessary bond strength and duration, moisture, UV, heat and solvent resistance.
There is no substitute for proper testing of the proposed materials under actual usage
conditions. The final decision should be made by the customer to choose the label /
adhesive combination that meets the requirements of the specific use.
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