Plastic is water resistant because it is waterproof.
There are seven raw material polymers in use today: polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, polystyrene, polycarbonate and poly(methyl methacrylate) (Plexiglas). These account for 98% of all polymers and plastics present in everyday life. Each of these polymers has its own characteristic degradation modes and resistance to heat, light and chemicals. Polyethylene, polypropylene and poly(methyl methacrylate) are sensitive to oxidation and UV radiation, while PVC can discolor at high temperatures due to the loss of hydrogen chloride, thus becoming brittle. PET is sensitive to hydrolysis and attack by strong acids, while polycarbonate depolymerizes rapidly when exposed to strong alkalis. PET is also sensitive to hydrolysis and attack by strong acids, while polycarbonate depolymerizes rapidly when exposed to strong alkalis. PET is also sensitive to hydrolysis and attack by strong acids.
Increasing chain polymers such as poly(methyl methacrylate) can be degraded by thermolysis at high temperatures to give rise to monomers, oils, gases and water. Degradation takes place by:
Chemical resistance of plastics
Plastic has become an essential material in all aspects of our modern life. It has replaced many materials, such as glass, metal, paper and wood, and allows us total changes in our daily lives.
Even if there are many advantages to its use, plastic generally ages rapidly under the effects of light, oxygen and heat. This aging leads to loss of strength, stiffness or flexibility of the plastic part and may discolor, lose its luster or turn yellow.
Most commercial plastics are manufactured by processes involving chain polymerization, polyaddition or polycondensation reactions, usually controlled to produce individual polymer molecules with defined chemical composition and molecular weight.
When polymers are exposed to shear stress, heat, light, air, water, radiation or mechanical loads, chemical reactions start in the polymer. As a result, the chemical composition and molecular weight of the polymer will change. These reactions modify the physical and optical properties of the polymer.
Moisture penetrates plastic
The extreme result that can occur in service is hydrolysis, a chemical reaction with water. Hydrolysis is a slow process at room temperature but can be rapid at high service temperatures. This reaction causes a loss of molecular weight, breakage of molecular chains, loss of molecular weight and therefore loss of polymer properties, especially toughness.
This process is irreversible. Drying the plastic material will not restore the molecular weight or the initial properties. Hydrolyzed parts cannot be shredded and reused because their properties are not recoverable.water exposure of the plastic in the molten state.at melt temperature different reactions of the polymer to water or moisture can occur.plasticization of the mass causes an increase in fluidity. This will be reversible if the polymer is dried and reprocessed.
Hydrolysis occurring at melting temperatures is a rapid and severe process. It is not reversible, there is a loss of molecular weight and properties as well as a drastic reduction in the viscosity of the polymer, thus a substantial increase in flowability. This effect is not reversible. This effect at melting temperature does not require a large amount of water and is a fast process.
This is why better results are attributed to products called “marine quality” because this “label” means that their quality has been tested in marine environments, that is why there are marine paints, marine bronze and also, for half a century, marine aluminum alloys that have excellent resistance to corrosion in hostile environments such as the marine environment.
The aggressiveness of the marine environment in contact with metals is due to the abundance of chlorides “Cl” in seawater, with quantities of around 19 grams per liter, in the form of sodium chloride, salt, magnesium chloride, etc. Indeed, in the marine environment is where they are in equilibrium and is composed of:
The whole constitutes a very complex environment where the influence of each factor of chemical order (composition…) of physical order (temperature, pressure…), of biological order (fauna…) on the corrosion behavior of metals, is not really separable nor independently quantifiable.