Which poly(ethylene terephthalate), PET resin is the best one?

>> Thursday, 19 March 2009

Poly(ethylene terephthalate), PET resins have several basic differences follow this notes and find the one which is the best for your application.
1. Intrinsic Viscosity, I.V. - ranging from 0.72 up to 0.85 for injection stretch blow molding.
2. Polymer Type - Homopolymer or Copolymer
3. Residual Acetaldehyde A.A Level - Normal or Reduced
4. Cosmetic Grades - Able to resist crystallization.

1. Intrinsic Viscosity, I.V.Poly(ethylene terephthalate), PET

PET material for bottles is available in I.V. levels from 0.72 up to 0.85. Lower I.V. is more suited to fine details but will give lower strength in the final container and will have more tendency to flash. High I.V. material will give a stronger bottle but it may be impossible to form fine details in the preform or bottle.
Low I.V. materials tend to be better if you need to blow an intricate shape but will result in a container having less strength and will become more difficult to control in the stretch blow process.
A higher I.V. material will give better overall strength and it will be more easy to control. However, it will be more difficult to stretch into corners meaning that logos and textures will not be so well defined. In severe cases, it may also lead to pearlescence in the finished container.
Some of these difference can be adjusted out by raising or lowering the preform processing temperature.

2. Polymer Type
Most bottles can be blown from either polymer type, differences will only tend to show up when the container design becomes a little marginal. For example, homopolymer will crystallize more easily than copolymer so it may not be suitable for thick preforms. On the other hand, if you require some crystal growth (for heat resistance) then a homopolymer may be the best choice.
Copolymers also have a lower melting temperature than homopolymers and since it is a golden rule of PET processing to keep the melt temperature as low as possible to reduce degradation, then a copolymer again looks more favorable.
As a rule, copolymers tend to be a little more expensive than homopolymers but this can be offset by their (generally) beneficial characteristics.

3. Residual Acetaldehyde A.A. Level
If you are producing a container for mineral water or certain soft drinks, then you probably should choose one of the grades having a reduced level of A.A. These often include the letter 'W' in their grade number to indicate suitability for water containers. These materials are generally a little more expensive than the standard type so if you are producing a non-food container (or a non-sensitive foodstuff container) then it is advisable to go for the cheaper option.

4. Cosmetic Grades
These grades have been specifically manufactured to be virtually non-crystallizable. As a result of the differences in manufacture and the relatively low demand, these can also be extremely expensive, as much as four times the price of "normal" PET. However, exceptional results can be achieved even with very thick preforms (6~10mm).

How do know if I have selected a good material?
Although it is possible to generalize about PET grades as shown above, the actual results on the machine can sometimes be different to those expected. Therefore it is advisable to do a practical test with a sample of the material.
Different containers react to material type in different ways. If a material works well with one container, then it does not always guarantee that it will be good with all other containers. If a company has several machines and different mold designs, then it should sample the new material on all molds before committing to a bulk supply of the sample material.

9 komentarze:

ask4plastic.com 19 May 2009 at 04:03  

Ajanta Industries offers PET Bottle Mould, PET Preform Mold from India.

Anonymous,  7 January 2010 at 07:10  

Your blog keeps getting better and better! Your older articles are not as good as newer ones you have a lot more creativity and originality now keep it up!

Anonymous,  15 February 2010 at 13:15  

interesting read. I would love to follow you on twitter.

Anonymous,  4 September 2010 at 22:48  

Thank you, that was extremely valuable and interesting...I will be back again to read more on this topic.

Pet Blow Mold 17 January 2011 at 08:22  

ACME Disys was established in the year 2002. Today it shares the trust of leading Pet preform dies manufacturing companies. Acme boasts of being the leading Pet Blow Mold and Pet molds Manufacturer from India with over 300 proven moulds installed globally including100 plus systems in 48 cavitations.

Pet Preform Injection Molds 17 February 2011 at 05:17  

Acme Disys is a leading pet bottle industries offering a wide range of pet bottle design, pet preform injection molds and pet preform bootles at market leading prices in India.

Adreana Smith 25 April 2013 at 23:04  

SINO-PK is the latest collection of various multi-cavity closure mould, cap moulds and many more. We keen on the mutual interchangeable of the cavities, cores and other components, all the parts of cap moulds.

Cap Mould

Hochiming Chiang 3 August 2016 at 23:04  

Hi,
Nice information shared on Moulding. Recently I had got an intresting topic on Importance Of Pet Cans For Beverages.It's having a nice description over Moulding.Thanks for sharing this post.

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