Polyethylene naphthalate, commonly known as PEN, is a polyester polymer that is known for its durability, heat resistance anddimensional stability. It was first developed by DuPont in the late 1960s and was aimed to replace polyethylene terephthalate (PET) in applications that required higher heat resistance.

Chemical Structure of PEN

Polyethylene Naphthalate is derived from dimethyl naphthalene dicarboxylate and ethylene glycol monomers. Its chemical structure gives itproperties that are superior to PET in some aspects. While PET has a terephthalate structure, PEN contains a naphthalategroup in place of the benzene ring. This modification makes the polymer chains more rigid and heat resistant than PET.The naphthalate group has a higher melting point, which allows PEN to withstand higher temperatures than PET.

Physical and Mechanical Properties

Some key physical and mechanical properties of PEN that make it attractive for various applications include:

- High glass transition temperature (120-150°C) and melting point (260-265°C), which is 30-40°C higher than PET. This gives it superior heat resistance.

- Excellent dimensional stability. PEN exhibits very low shrinkage levels even after long periods at elevated temperatures.

- Strong mechanical properties. PEN offers good tensile strength (63-90 MPa), stiffness and impact resistance.

- Chemical resistance to acids, bases and organic solvents similar to PET. PEN is moderately permeable to gases like oxygen and carbon dioxide.

- Low moisture absorption of around 0.2% against 0.4% for PET. This makes it dimensionally stable under varying humidity conditions.

- Density of around 1.37 g/cm3, which is comparable to PET.

- Optical clarity and transparency similar to PET, covering a wide spectrum from ultraviolet to infrared regions.

 

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