Plastic Coated Bottles
DWK Life Sciences provides media-lab bottles with a polyurethane plastic coating to provide protection from mechanical impact and to help reduce leakage of the contents should the glass break. The maximum working temperature for these bottles is 135°Cbutlongtermexposure(>30 mins) should be avoided. Avoid exposure to direct heat from a hotplate or a Bunsen flame. These media bottles are suitable for freezing at -30°C and can also be used in microwave ovens. Please note that the plastic coating does not increase the permissible pressure at which the bottles can be used and a protective screen is recommended for all pressure work.
WHEATON® safety coated containers and bottles use a plastisol coating that 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 contents - reducesriskof chemical exposure and inhalation. Allows time for proper disposal.
Contains glass - prevents flying fragments and cuts
The coating material is plastisol, which is a dispersion of a fine particle size PVC resin (polyvinyl chloride) in a plasticiser where stabilisers, fillers, modifiers, colourants 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 150°C, 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 and below. Do not use above 150°C or over direct heat or flame. The coating is not dry heat sterlisable. Coating will yellow and burn with high heat exposure but will continue to protect until black.
Labelling Adhesives for Coated Glass Containers
For on-line and pressure sensitive labelling 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 meet the requirements of the specific use.
Recommendations for Autoclaving Plastic Coated Bottles
The suggested conditions for steam sterilization are 121°C @ 15 psi for 20 minutes. Portions of the coating may absorb a small amount of water vapour 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. Autoclaving effects on the coating will vary slightly due to equipment, bottle size and configuration, procedure and frequency of procedure. It is recommended that bottles 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.