Question

Which plastic types gives identical infrared spectra? Why does this make sense from their structures?

Background info: This is referring to the 6 plastic types: PETE, HDPE, LDPD. PVP, PP ad PS.

Answer 1

There are 6 plastic types, they are PETE, HDPE, LDPD. PVP, PP ad PS. In IR Spectrum ,HDPE(high-density polyethylene) and  LDPE(low-density polyethylene) gives identical infrared spectra.LDPE is softer, more flexible and melts at a lower temperature than HDPE.While, HDPE is harder, has a higher chemical resistance.

SPECTRUM ANALYSIS :-

• HDPE(high-density polyethylene) :  

2915 (a) C-H stretching vibration ; 2845 (b) C-H stretching vibration ;1472 (c) CH2 bending vibration ; 1462 (d) CH2 bending vibration ; 730 (e) CH2 rocking vibration.

• Low-density polyethylene (LDPE) or linear LDPE (LLDPE) :

2915 (a) C-H stretching vibration; 2845 (b) C-H stretching vibration ; 1467 (c) CH2 bending vibration ; 1462 (d) CH2 bending vibration ; 1377 (e) CH3 bending vibration ; 730 (f) CH2 rocking vibration ; 717 (g) CH2 rocking vibration.

Wavenumber cm 1500 4000 3000 2000 1000900 800 750 700 transmittance IR Spectrum of low density poly(ethene) 4000 3000 2000 Wavenumber cm! 1500 1000 900 800 750 700 transmittance IR Spectrum of high density poly(ethene)