Breakage plastic

Benchtop clinical centrifuges capable of generating a relative centrifugal force (RCF) of 1300 x g to 1800 x g range in cost from 450 to 2000. The difference here results from the number and volume of samples that can be run at one time, as well as the inclusion of speed control options, timers, and so forth. Due to the potential for breakage, plastic, rather than glass centrifuge tubes are preferred. 

It is important to differentiate between brittie and plastic deformations within materials. With brittie materials, the behavior is predominantiy elastic until the yield point is reached, at which breakage occurs. When fracture occurs as a result of a time-dependent strain, the material behaves in an inelastic manner. Most materials tend to be inelastic. Figure 1 shows a typical stress—strain diagram. The section A—B is the elastic region where the material obeys Hooke s law, and the slope of the line is Young s modulus. C is the yield point, where plastic deformation begins. The difference in strain between the yield point C and the ultimate yield point D gives a measure of the brittieness of the material, ie, the less difference in strain, the more brittie the material. 

Plastics are extensively used in medicine to package drugs, ointments, and accessories. Plastics serve to protect medicines, surgical/ clinical equipment, medical materials, etc. from contamination and breakage in many ways, from single-service squeeze packs of cough syrup to carrying cases used to ship human eyes between hospital eye banks. 

In addition to protection from breakage, the brown plastic bottles in which hydrogen peroxide is commonly sold enhance the shelf-life of this product. Packaging plays an important role in limiting the light-induced chemical reactions of hydrogen peroxide. 

PVC has a high coefficient of expansion, one of the highest for all plastic materials, and substantially higher than metals and wood. Therefore, design allowances must be made to provide for movement in order to avoid buckling, breakage, etc,... 

For longer term storage, gels may be stored wet at 4°C. The wet gel should be wrapped in a piece of plastic wrap. This permits handling the gel without risk of breakage. The wrapped gel can be stored in a sealable bag for <1 year at 4°C. To preserve gels indefinitely, they may be either vacuum dried onto filter paper or air dried between sheets of cellophane. 

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