soft pvc

[bisudai]

I am designing very flexible pvc tube around 55 durometer hardness, but the tubes stick to each other while extruding. How can I change the texture of the tube so that they don't get tacky or sticky while extruding. Also, is there any additive that makes soft clear pvc opaque?

 

[patprimmer]

As you add plasticiser to PVC to make it flexible you also lower its melting point and tend to make it sticky.

The way to stop the tubes sticking together is to extrude into a water bath and to keep the tubes seperated.

The question about making it opaque sounds to stupid to be contemplated, so I will presume you do not understand the terminology of colours.

I will presume by opaque you actually mean opalescent which is certainly not opaque.

Opalescent is the translucent white colours very often used in light diffusers. It allows a significant proportion of the light to pass through, but scatters it.

It is quite difficult to get a good consistent opal colour in polymers that are a lot clearer than PVC, but if you don't mind slightly yellow tint that varies I am sure it can be done. Processing conditions will also be critical as varying shear can influence the particle size and quality of dispersion of the pigments as well as varying the yellow tint of the PVC rein.

Regards
Pat
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[bisudai]

Thanks for your reply.

Do you have any favorite books or journals in plastics?

 

[Demon3]

You can make a material diffuse light by adding particles with different refractive index to the polymer and with the right size. Examples include mineral fillers (also increase the modulus) and impact modifiers (decrease modulus and improve impact resistance).

You can even make a material that changes transparency reversibly with temperature (I've made such a material, it's called ThermoShift).

Chris DeArmitt PhD FRSC CChem

 

[tnatale]

I would consider using a coextrusion. You can make the exterior layer any color that you want and look at loading it with anti-block materials to reduce the adhesion between pieces (akin to what they do for polymer films. You can also put less plasticizer in the skin, this will reduce the tendency to stick.