Why is FEP transparent and PTFE not?

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fluorinated ethylene propylene (FEP) is close relative of poly(tetra-fluoroethylene) (PTFE), both only contain fluorine and carbon atoms,both have very similiar properties yet FEP is relatively transparent while PTFE is opaque, why?




polymers materials optical-properties




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    fluorinated ethylene propylene (FEP) is close relative of poly(tetra-fluoroethylene) (PTFE), both only contain fluorine and carbon atoms,both have very similiar properties yet FEP is relatively transparent while PTFE is opaque, why?




    polymers materials optical-properties




    share|improve this question
























      up vote
      3
      down vote

      favorite









      up vote
      3
      down vote

      favorite











      fluorinated ethylene propylene (FEP) is close relative of poly(tetra-fluoroethylene) (PTFE), both only contain fluorine and carbon atoms,both have very similiar properties yet FEP is relatively transparent while PTFE is opaque, why?




      polymers materials optical-properties




      share|improve this question














      fluorinated ethylene propylene (FEP) is close relative of poly(tetra-fluoroethylene) (PTFE), both only contain fluorine and carbon atoms,both have very similiar properties yet FEP is relatively transparent while PTFE is opaque, why?





      polymers materials optical-properties





      share|improve this question













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      edited Aug 27 at 16:41









      A.K.

      6,14511143




      6,14511143










      asked Aug 27 at 8:52









      wav scientist

      23719




      23719




















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          Otherwise clear plastics lose their transparency from crystallization of the polymer. The crystalline phases have different refractive indices and when a sufficient number form the light becomes so scattered that the material is no longer transparent. Note this is an extensive property and if a material is thick enough it will become opaque, while a thin film of the same material could be translucent.



          FEP lacks the regularity in polymer structure that PTFE has, and thus does not crystallize as readily. Since the crystallite density is lower, the polymer is more amorphous and the medium does not scatter as much and thus appears more transparent.






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            up vote
            3
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            The transparency of a plastic does not depend on its nature but on how it is made.



            To get a transparent plastic it must be cooled very fast when it is in molten state.
            If the cooling is too slow, the polymer begins to order it self in more or less crystalline domains.



            When it is not isotropic anymore, it is also not transparent.






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            • I cant imagine what non-isotropic plastic is.What is the difference between normal isotropic and non-isotropic plastic?
              – wav scientist
              Aug 27 at 18:55










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            2 Answers
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            active

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            2 Answers
            2






            active

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            active

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            up vote
            2
            down vote



            accepted










            Otherwise clear plastics lose their transparency from crystallization of the polymer. The crystalline phases have different refractive indices and when a sufficient number form the light becomes so scattered that the material is no longer transparent. Note this is an extensive property and if a material is thick enough it will become opaque, while a thin film of the same material could be translucent.



            FEP lacks the regularity in polymer structure that PTFE has, and thus does not crystallize as readily. Since the crystallite density is lower, the polymer is more amorphous and the medium does not scatter as much and thus appears more transparent.






            share|improve this answer


























              up vote
              2
              down vote



              accepted










              Otherwise clear plastics lose their transparency from crystallization of the polymer. The crystalline phases have different refractive indices and when a sufficient number form the light becomes so scattered that the material is no longer transparent. Note this is an extensive property and if a material is thick enough it will become opaque, while a thin film of the same material could be translucent.



              FEP lacks the regularity in polymer structure that PTFE has, and thus does not crystallize as readily. Since the crystallite density is lower, the polymer is more amorphous and the medium does not scatter as much and thus appears more transparent.






              share|improve this answer
























                up vote
                2
                down vote



                accepted







                up vote
                2
                down vote



                accepted






                Otherwise clear plastics lose their transparency from crystallization of the polymer. The crystalline phases have different refractive indices and when a sufficient number form the light becomes so scattered that the material is no longer transparent. Note this is an extensive property and if a material is thick enough it will become opaque, while a thin film of the same material could be translucent.



                FEP lacks the regularity in polymer structure that PTFE has, and thus does not crystallize as readily. Since the crystallite density is lower, the polymer is more amorphous and the medium does not scatter as much and thus appears more transparent.






                share|improve this answer














                Otherwise clear plastics lose their transparency from crystallization of the polymer. The crystalline phases have different refractive indices and when a sufficient number form the light becomes so scattered that the material is no longer transparent. Note this is an extensive property and if a material is thick enough it will become opaque, while a thin film of the same material could be translucent.



                FEP lacks the regularity in polymer structure that PTFE has, and thus does not crystallize as readily. Since the crystallite density is lower, the polymer is more amorphous and the medium does not scatter as much and thus appears more transparent.







                share|improve this answer














                share|improve this answer



                share|improve this answer








                edited Aug 27 at 16:39

























                answered Aug 27 at 16:33









                A.K.

                6,14511143




                6,14511143




















                    up vote
                    3
                    down vote













                    The transparency of a plastic does not depend on its nature but on how it is made.



                    To get a transparent plastic it must be cooled very fast when it is in molten state.
                    If the cooling is too slow, the polymer begins to order it self in more or less crystalline domains.



                    When it is not isotropic anymore, it is also not transparent.






                    share|improve this answer




















                    • I cant imagine what non-isotropic plastic is.What is the difference between normal isotropic and non-isotropic plastic?
                      – wav scientist
                      Aug 27 at 18:55














                    up vote
                    3
                    down vote













                    The transparency of a plastic does not depend on its nature but on how it is made.



                    To get a transparent plastic it must be cooled very fast when it is in molten state.
                    If the cooling is too slow, the polymer begins to order it self in more or less crystalline domains.



                    When it is not isotropic anymore, it is also not transparent.






                    share|improve this answer




















                    • I cant imagine what non-isotropic plastic is.What is the difference between normal isotropic and non-isotropic plastic?
                      – wav scientist
                      Aug 27 at 18:55












                    up vote
                    3
                    down vote










                    up vote
                    3
                    down vote









                    The transparency of a plastic does not depend on its nature but on how it is made.



                    To get a transparent plastic it must be cooled very fast when it is in molten state.
                    If the cooling is too slow, the polymer begins to order it self in more or less crystalline domains.



                    When it is not isotropic anymore, it is also not transparent.






                    share|improve this answer












                    The transparency of a plastic does not depend on its nature but on how it is made.



                    To get a transparent plastic it must be cooled very fast when it is in molten state.
                    If the cooling is too slow, the polymer begins to order it self in more or less crystalline domains.



                    When it is not isotropic anymore, it is also not transparent.







                    share|improve this answer












                    share|improve this answer



                    share|improve this answer










                    answered Aug 27 at 12:13









                    Raoul Kessels

                    3,223119




                    3,223119











                    • I cant imagine what non-isotropic plastic is.What is the difference between normal isotropic and non-isotropic plastic?
                      – wav scientist
                      Aug 27 at 18:55
















                    • I cant imagine what non-isotropic plastic is.What is the difference between normal isotropic and non-isotropic plastic?
                      – wav scientist
                      Aug 27 at 18:55















                    I cant imagine what non-isotropic plastic is.What is the difference between normal isotropic and non-isotropic plastic?
                    – wav scientist
                    Aug 27 at 18:55




                    I cant imagine what non-isotropic plastic is.What is the difference between normal isotropic and non-isotropic plastic?
                    – wav scientist
                    Aug 27 at 18:55

















                     

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