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Below are the answers to a selection of questions relating to Vac-Sil® Membranes.

A Comparison Chart is also available for download which we hope will help you determine the best choice for your particular requirements.

All available downloads in relation to Vac-Sil® quality membranes can be found below.


What thicknesses and tolerences are VAC-SIL® membranes made to?

VAC-SIL® Membranes are manufactured in accordance with International tolerance standards – (+/- 10%) – and these are confirmed for the most popular thicknesses as follows:-

VAC-SIL® Supreme : 1mm (+/-0.3mm)

VAC-SIL Pro® : 1.5mm (+/-0.3mm) & 3mm (+/-0.3mm)

VAC-SIL® Lamin8 Fabric Reinforced : 3.8mm (+/-0.38mm)

VAC-SIL® Endurance Plus Fabric Reinforced : 4mm (+/-0.3mm)

What standard of packaging can you expect with VAC-SIL® Membranes?

Membranes are rolled onto a cardboard tube interleaved with polythene, then packed inside a heavy duty cardboard tube, which is then packed inside polypropylene sacking.

What is the correct way to store stocks of VAC-SIL® Membranes?

After goods inward inspection of membranes upon receipt, we suggest you store inside the packaging. We then recommend you store in accordance with ISO2230, which generally suggests “storage temperature should be below 25° C and products should be stored away from direct sources of heat such as boilers, radiators and direct sunlight.”

If you need further help with this, please ask – we are here to help.

How are the physical properties of VAC-SIL® Membranes measured?

J-Flex use tangible world class rubber norms to measure the physical properties of VAC-SIL® Membranes – typically ISO or ASTM specifications.

Are the ingredients used in VAC-SIL® Membranes safe and fit for purpose?

This is a very good question and we confirm that most of our recipe ingredients are of European origin. As such we have fully traceable Material Safety Data Sheets (M.S.D.S.) and these are available upon request.

All of the raw material ingredients have been tested for compliance and guarantee that no banned substances are included in our finished product.

What is the best membrane for your application?

A VAC-SIL® Membrane of course!

This is a vital question though, and there is no one answer that is right for everyone. There are many factors that can effect the choice of membrane, for example :-

  • type of encapsulant (eva etc.)
  • make up of p.v. / solar module
  • type of laminator
  • operating cycle – time/temperature
  • budget constraints

We would be delighted to discuss your own specific requirements further.

How long should a membrane last?

This is really very subjective as operating conditions and controls can be so very different from company to company. For example we have one very large European customer who has modified the encapsulant used and strictly controls their production process – so much so they achieve over 10,000 cycles using our standard VAC-SIL PRO® Membranes.

Membrane cycle life can be variable as there are many factors outside of our control. The improved performance of the material offers the potential for significant and improvement, depending on the operating conditions.

See our White Paper: “A Guide to Solar P.V. Module Lamination Membranes – Optimising Performance” in the download links below and also our handy VAC-SIL® Membranes Range Datasheet

What can be done to extend the life of membranes?

A whole host of things can be done including – correct fitting and tensioning, regular maintenance checks, regular cleaning of EVA deposits.

In addition you could protect the membrane with a layer of PTFE / Fabric release sheet between the modules and the membrane. (We do have stock options available – just talk to us).

If you need EVA resistance our VAC-SIL® Lamin8 and Endurance Plus Membranes have great resistance to outgassing and give far better life than standard membranes. See test results on the Vac-Sil® Specification Sheet.

Is it wise to use membranes with seamed joints?

In our opinion joints are mechanically weak areas. Continuous “draw down” under vacuum conditions will search out any weaknesses in the seam and lead to early membrane failure.

In addition seams can sometimes leave unwanted impression marks on modules – NOT what you want!

For J-Flex, one piece sizing is not a problem. We can offer VAC-SIL® membranes up to 3200mm wide in one piece.

Does colour or surface finish have any impact on membrane performance?

Based on feedback from customers worldwide, we can see no advantage or disadvantage of different colours, or indeed surface finish. For this reason we offer:-

VAC-SIL® Supreme in Black*

VAC-SIL® Pro® in Blue

VAC-SIL® Lamin8 Fabric Reinforced in Green/Black

VAC-SIL® Endurance Plus Fabric Reinforced in Orange/Black

Most of our competitors offer a standard Grey or Translucent and this makes it very difficult to differentiate between suppliers. J-Flex offer these distinctive colours to distinguish materials. For better or worse J-Flex don’t hide away from our responsibilities.

It is vital that VAC-SIL® Lamin8 and Endurance Plus membranes are loaded with the black coloured Acid / E.V.A. resistant face down against the module surface.

We find the question of surface finish interesting – but in conclusion we see no evidence that one option is better than another. Common sense says that a fabric impression will provide a natural venting path to aid release especially in hot / sticky conditions. Most of our customers do prefer fabric impression 1 side and smooth 1 side.

The physical properties of the material will be exactly the same irrespective of colour or surface finish – these do not change.

*Vac-Sil® Supreme is not suitable for Solar P.V. panel production, it is purely for vacuum forming of composites and surface finishes within the Automotive, Furniture, Marine and Aerospace markets.

Related PDF Downloads - Informational & Educational

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Why buy from J-Flex?

If you are looking for a friendly and helpful industrial rubber products supplier, with great product knowledge and excellent customer service, then you’re in the right place. We supply a vast range of quality items including rubber sheet and an array of fabrications made from premium grade elastomers including silicone and Viton™ - many of which are available for next day delivery. With over 35 years operating experience, J‑Flex is the preferred supplier of industrial rubber products - providing engineered rubber components and specialist rubber sheetings you can trust. Whether you are looking for silicone sheets, rubber mouldings, gaskets, sleeves, extrusions, bellows, fabrications, rubber sealants or adhesives -including Viton™ sheets and sealants, J‑Flex can help. You'll find our Accreditations, Approvals, Certifications and Compliance​ information here.