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A number of different methods are used to evaluate a polymer's resistance to environmental stress cracking. A common method in the polymer industry is use of the Bergen jig, which subjects the sample to variable strain during a single test. The results of this test indicate the critical strain to cracking, using only one sample. [5]
HDPE is known for its high strength-to-density ratio. [4] The density of HDPE ranges from 930 to 970 kg/m 3. [5] Although the density of HDPE is only marginally higher than that of low-density polyethylene, HDPE has little branching, giving it stronger intermolecular forces and tensile strength (38 MPa versus 21 MPa) than LDPE. [6]
Polypropylene is normally tough and flexible, especially when copolymerized with ethylene. This allows polypropylene to be used as an engineering plastic, competing with materials such as acrylonitrile butadiene styrene (ABS). Polypropylene is reasonably economical. [citation needed] Polypropylene has good resistance to fatigue. [8]: 3070
Polyethylene was first synthesized by the German chemist Hans von Pechmann, who prepared it by accident in 1898 while investigating diazomethane. [12] [a] [13] [b] When his colleagues Eugen Bamberger and Friedrich Tschirner characterized the white, waxy substance that he had created, they recognized that it contained long −CH 2 − chains and termed it polymethylene.
Ultra-high-molecular-weight polyethylene (UHMWPE, UHMW) is a subset of the thermoplastic polyethylene. Also known as high-modulus polyethylene ( HMPE ), it has extremely long chains, with a molecular mass usually between 3.5 and 7.5 million amu . [ 1 ]
Polypropylene: injection molding, fibers, and film. Compared to polyethylene, polypropylene is stiffer but less prone to breaking. It is less dense but shows more chemical resistance. [11] Synthetic base oil (by far the most used one): industrial and automotive lubricants. [12]
In addition, chemical compatibility refers to the container material being acceptable to store the chemical or for a tool or object that comes in contact with a chemical to not degrade. For example, when stirring a chemical, the stirrer must be stable in the chemical that is being stirred. Many companies publish chemical resistance charts.
Due to its flexibility, extreme resistance to chemical attack and optical transparency, this material, along with PFA is routinely used for plastic labware and tubing that involves critical or highly corrosive processes. Brand GmbH, Finemech, Savillex and Nalgene are well known laboratory suppliers that makes extensive use of the two materials.
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