Identification of plastic sample from environment is difficult. Differential scanning calorimetry provides a better way for identification of PP and PET and others. How to differentiate between LDPE and LLDPE ? May i know the range of melting temperature for both polymers.
They have different Tc's my friend. (Tc: Crystalline Temperature)
Those of LLDPE are higher values.
LDPE has met peak ranging from 105-115 C, LLDPE 115-128C, HDPE 128-136 C. You can run FTIR as well.
Amit Dharia has offered the basic story, but you should look up references for more details. In particular the enthalpy of melting (as well as the melting curve) is a useful measure for identifying materials, especially if they are mixtures. It should also be understood that those melting points are best measured as reheats at a standard rate, after an initial thorough melting and then a controlled cooling to well below Tm (or Tc as Pedram Malaekeh has called it). You cannot use the initial melting temperature curve for identification - you must anneal out the previous cooling and stress history. This should all be done under a purified inert gas, and sample size and temperature ramp rates should be standard, if you wish to compare to references. Look for an ASTM standard DSC method (probably D3418) or equivalent in ISO.
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