Laminated fabrics and causes of premature delamination

Cloth nappy covers are commonly made using laminated fabrics. One of the most popular laminated fabrics is polyurethane laminate (PUL). It is a water-resistant fabric, which makes it an excellent choice for nappies and accessories like wet bags.

Unfortunately, not all PUL are created equal. Some products delaminate prematurely and people often ask us why this happens. We have thus written this article to help you choose products that will last and to understand what does and doesn’t contribute to delamination. We also want to encourage businesses to source high-quality fabric for their products. 

Expectations for good PUL

When treated correctly during manufacturing, PUL has excellent UV resistance. It also has excellent durability against washing, wear and chemical exposure. 

Well-manufactured laminated fabrics will last for a reasonable amount of time. They will withstand standard laundry practices. 

Contrary to popular belief, delamination is not caused by:

• washing in 60ºC water (standard hot wash temperature for domestic washing machines)
• diluted chlorine bleach
• using laundry detergent in the wash cycle

Our sanitise information provides PUL-safe dilutions of chlorine bleach. Following our PUL-safe dilutions will not damage high-quality PUL.

Quality products can be consistently produced only from quality starting materials using a well-maintained processing machine which is specially designed for the particular job.

~ Walter Fung, Coated and Laminated Textiles

Defining reasonable use

Reasonable can be subjective. A product used full time for 6 months or less should not delaminate unless it has been:

• repeatedly exposed to very high (greater than 10) or very low (less than 3) pH or
• repeatedly washed in very high temperature water (90°C and above).

If the PUL has been frequently used and washed over 2 years, it may delaminate based on the prolonged use. 

The PUL bonding process

PUL is made up of a fabric layer and a plastic layer bonded together with glue. To manufacture PUL, a glue is spread over fabric and a plastic layer is added to it. The fabric is then heat set.

The plastic layer prevents liquid from seeping through, while the fabric layer generally determines the tear and tensile strength.

Glue also determines the resistance to liquids seeping through and how well the plastic layer adheres to the fabric layer. The glue can be a water-based or solvent-based fluid or a ‘hot melt’ material. A ‘hot melt’ is either a solid or a jelly that melts when heat is applied.

Durability testing

There are testing standards that manufacturers should adhere to for quality assurance purposes. For example, stretch and set, flammability and tear strength. The end product needs to comply with such durability testing.

One of the most important durability tests is assessing the strength of the bond between the base fabric and the plastic layer. This bond is mainly the result of glue choice and application. It is important to measure the initial bond strength after manufacturing.

Cloth nappy covers and other products made from PUL that are repeatedly washed have the added requirement to withstand repeated washing. This means durability tests must be carried out after simulated washing and cleaning, as well as simulated wearing.  

Causes of delamination

Delamination is when the plastic lining separates from the base fabric. Premature delamination of laminated fabrics is typically a result of poor manufacturing quality.

The most common causes of delamination are:

• insufficient glue strength
• incorrect glue choice 
• incorrect glue application
• excessive antistatic product used in the process 
• insufficient heat used in processing

Flawed application of the glue, incorrect choice of glue used or insufficient heat to set the glue can all result in delamination.

Additionally, the preparation and application of the glue can vary based on the skill level, experience and diligence of the person doing the job. If the glue is not heated high enough, the fabrics will not adhere together properly.

Using delaminated fabric

Once PUL has delaminated, there is little that can be done to reverse the damage. However, if there are no rips or holes in the plastic layer, the fabric is still water-resistant and can continue to be used. Adding extra absorbency will also help mitigate the effects of delaminated cloth nappies.

The difference between TPU and PUL

TPU is thermoplastic polyurethane, while PU is polyurethane. They are essentially the same thing and their names are often used interchangeably. The main difference between TPU and PU is that TPU has no cross-links, whereas PU can have cross-links when the polymer (plastic) is produced.

Choosing high-quality products

When looking at buying reusable nappies or accessories, contact the business and ask them if their fabric manufacturer does quality assurance and durability testing, and the type of warranty the product has. 

Remember, in Australia a product warranty is an extra promise that a business can choose to make on top of the consumer guarantees. A warranty does not usurp your consumer guarantee.