2 replies to this topic

[EmmaH394]

Hey, can anyone help me with this question?

Darcon, a synthetic polymer, is used in heart surgery.

Why would this polymer be formed as a fibre and not a resin?

Please help! Thanks

[Marcus]

Hmm I'm not quite sure what is expected as an answer to this, it could be as simple as heart muscle are fibres so the polymer would try and replicate what the body has, or possibly fibres are 'stretchy-er' (ie more elastic) therefore better suited to heart contractions.

[donaldc50]

Hi just remembered to look at the forum. Right. The polymer concerned is called dacron. It is a polyester. In higher chemistry we teach you that polyesters are made in two forms. One fibrous, where long linear molecules are formed, the other being resins, where cross linking between the linear strands provides stregth etc. Once the resin has cured it is very strong and hard and pretty much indestructable to all but excessive heat. Resins are used in fibreglass construction (GRP). Look in your notes. Now dacron is a linear polymer because it does not have the ability to cross-link. To do so at least one of the monomers would need to have some unsaturation (C=C) or side groups that could react to form cross links or form hydrogen bonds between molecules like kevlar. The question concerned only wants you to identify the part shown as not having the ability to cross link.
Why are the fibres used. Well they are strong and resistant to stretching in wet environments and when fixing heart problems ( sewing on valves etc you don't want the fibres stretching too much as the heart muscle moves a lot of course. Its properties include high tensile strength, high resistance to stretching, both wet and dry, and good resistance to degradation by chemical bleaches and to abrasion. The continuous filament yarn is used in curtains, dress fabrics, high-pressure fire hoses, men's shirts, and thread. Sewing up heart bits should be no probs. Hope this helped.