Certain Guidelines When Designing The Diapers Biology Essay


The research team has to adhere to certain guidelines when designing the diapers. The challenge for the design team is to come up with an innovative yet simple design for the final product as well as making sure that it can is in line with our aim of having a "2-in-1" diaper, that is having both the biodegradable part as well as a reusable part in it. Several guidelines were set when designing, and they are:

A good absorption rate of liquid for the core.

Comfortable and efficient design for the baby.

The materials used must be environmental-friendly as well as harmless to the baby.

Hence, the research team has come up with a new design.Our product consists of a diaper pants that can be used over and over again as well as an absorbent core (which will be referred to as inserts) which is biodegradable but for one-time usage only.The final design for our product is as below:

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Figure : An outside view of the diaper pants

Figure : Inner view of the diaper pants. The dashed lined centered indicates where the refillable

insert is placed.

3.2 Material of Eco-Diaper

3.2.1Material of Diaper Pants

The diaper pants consists of two fabric materials:

1. PUL

The outer part of the pants is made out of PUL fabric. PUL, or also known as polyurethane laminated fabric, is more than just a plastic backing on a fabric. Originally used in the medical field, it provides the waterproof barrier that can survive multiple institutional washings.The laminate can also be autoclaved, which is a very high heat steam sterilization process, to make it safe for reuse even after it comes into contact with blood or other bodily fluids.The polyurethane laminate can be customized by the manufacturer and comes in different thicknesses.For diapers, 1 mil or 2 mil is generally preferred. This allows for a good stretch,complete waterproofing, and is still comfortable enough to wear next to the skin.

2. Nonwoven Fabric

The material chosen for the inner layer of the pants is made out of a nonwoven fabric. The fabric is chosen as it can be engineered to provide specific functions. In this case, as with the outer layer, the fabric must be durable, washable, provides a bacterial barrier as well as soft. As the refillable insert is placed on this layer, it must also have a hydrophilic property to absorb liquid in the event that leakages happen from the absorbent core - this makes it easier for washing after use.

3.Elasticized Bands

Besides the two fabrics, the diaper pants also consists of elasticized bands at four sides (two at the legs, and the other two at the front and back of diaper) to ensure a good and comfortable fit for the baby.

4. Snaps

Snaps as fasteneners at the baby's waist and also to 'hold' the inserts. The snaps used are polyactel resin snaps as it is known to be durable. It is unaffected by urine and it can also withstand repeated laundering.

3.2.2 Materials of Refillable absorbent inserts

1. Hydrophilic and Hydrophobic Nonwoven Fabrics

The fabric used for the inserts is mainly nonwoven fabrics. However, there are two types of nonwoven fabric used - hydrophilic and hydrophobic nonwovens. The layer that touches the baby's bottom has the hydrophilic property so as to allow liquid to pass through to the absorbent middle layer, which is the core of the insert, thereby keeping the baby's bottom dry. This layer is also known as the Acquisition Distribution Layer (ADL). The bottom layer is made out of hydrophobic nonwoven so as to not allow liquid to pass through once the middle layer has reached its absorbing limit.

2. Sodium Polyacrylate and Cellulose Pulp

For the core of the inserts, it is composed of two essential elements, sodium polyacrylate (SPA) and cellulose pulp. These SPA particles act as tiny sponges that retain many times their weight in water. SPA have the ability to chemically link with different polymer molecules in a process known as cross linking. When a large number of these polymeric chains are cross linked, they form a gel network that is not water soluble but that can absorb vast amounts of water, and thus, it is also known as superabsorbents. The swelling capacity is approximately 20-40 mL of urine per gram of SPA , depending on the degree of cross linking as the strength of the gel network can be varied. This is an important property because gel strength is related to the tendency of the polymer to deform or flow under stress. If the strength is too high the polymer will not retain enough water. If it is too low the polymer will deform too easily, and the outermost particles in the pad will absorb water too quickly, forming a gel that blocks water from reaching the inner pad particles. This problem, known as gel blocking, can be overcome by dispersing wood pulp fibers, which in this case we use cellulose pulp, throughout the polymer matrix. These cellulose pulp act as thousands of tiny straws which suck up water faster and disperse it through the matrix more efficiently to avoid gel blocking.

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At the inner layer, the additive TDPA (Totally Degradable Plastic Additive) is also added in small quantities to enhance the rate of degradation of plastics. Therefore, this additive is the key to helping the diaper to be environmental-friendly once it has been used. The degradation process, which involves the reaction of the plastic with oxygen in the air, is initiated by exposure to ultraviolet light (sunlight), elevated temperatures and/or mechanical stress. It is "programmed" to start degradation on disposal after the product has fulfilled the required shelf and service lives as defined by end users.

3.3 Credibility Tests

Our diaper undergoes 2 types of tests, which are the fluid handling and the biodegradibility of the absorbent core.

3.3.1The Fluid Handling Test of Diaper Core

The design of the core is mainly influenced by 3 R's:

a. Retention

Test: Retention under incremental Pressure

b. Rewet

Test: Rewet under incremental Pressure

c. Redistribution

Test: Fluid Redistribution Test

The Maximum Design Pressure(MDP) for each diaper size was first considered and it was

calculated as the maximum pressure applied by a baby at the top limit of the specified

baby weight range. Retention

The 'Retention under incremental pressure' test is used to determine three diaper

Characteristics- (i) overall retention,

(ii) released fluid percentage and

(iii) zoned retention.The diapers are soaked in saline solution for 15 minutes and then subjected to increasing levels of pressure; the fluid released is recorded at each pressure level and from this the retention of the diaper at each level is calculated.

i. Overall retention - The results of the retention test are plotted as a linear graph of the relationship between the retained fluid in the diaper and the applied pressure.The differing gradients give a clear indication of the SAP characteristics contained within tested diaper cores.Thus, it is a method of approximating the diaper SAP content (and also showing the differing relative absorptions of these different cores under increasing pressure. The test results will also be used to help in creating visually informative charts showing fluid diffusion and redistribution. The theoretical capacity of the diaper samples can be read directly from this chart for the relevant MDP's or for any other pressure that may feel appropriate.

ii. Released fluid percentage

The second characteristic calculated from the results of this test is the percentage of fluid that is released from the diaper under pressure. This is determined by the SAP characteristics. This property has a significant impact on the rewet and redistribution performance. The percentage is based on the release of fluid between 2.5kPa and the Design Pressure(DP) of the diaper and is calculated in the following way:

Released Fluid % = (Retention at 2.5kPa- Retention at DP)/(Retention at DP) x 100

This percentage gives a good understanding of the amount of free fluid that will be moving around the diaper when pressure is applied and provides a performance indicator that represents an important characteristic of the SAP within the core.

iii. Zoned Retention

The third output from the Retention test is the zoned retention bar chart at MDP. The diapers are loaded up to the MDP and then cut into 8 equal zones. The pieces are weighed and the fluid retention is calculated and recorded. The resulting chart is then drawn to show the retained fluid per zone.The chart clearly shows the amount of fluid that this diaper will contain in each zone at the MDP, which represents the minimum retention that should be expected in each zone of the diaper in real life usage (since the MDP is set at the upper limit of pressure expected for the size of diaper). Rewet

In the Rewet under incremental pressure test, the samples are prepared in the same way as a horizontal rewet test with insults of saline solution being applied without pressure.The absorption speeds of each inserts are recorded to provide a Performance Indicator for this characteristic.At fluid levels of 100, 150, 200, 250, 300mls, samples are tested to record the percentage of saturation of the diaper surface under each pressure; these surface saturation percentages are then charted against the applied pressure. Using this visually descriptive chart, we can observe the rewet values at each step in pressure and can decide if surface rewet is occurring at too low a pressure. If so, the curve can be moved by altering the SAP quality and/or quantity, the fluff/SAP ratio or perhaps by changing the acquisition distribution layer (ADL). Redistribution

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Having achieved an understanding of the pressure required to create surface rewet, it is then important to determine if this wetting of the skin will occur once or at every subsequent application of pressure. The rewet defined in (b) above will be referred to as the initial rewet. Subsequent pressure applications will occur in use as the baby moves around and it is important to determine if the skin is going to be wet again with each movement or if the diaper surface will quickly be dried by the redistribution of fluids under pressure within the core.

The most important point to be learned is that a standard rewet test gives a very 'one dimensional' picture of surface wetness. Not only does it give the result at a single rewet load (commonly 0.7psi, 4.8kPa), but it also shows only the initial rewet. The ability to redistribute fluids is an important diaper core performance property that adds significant value to the diaper, and the drier quality of a well designed core will be reflected in test panel results for daytime and night time use; reducing the incidence of wakeful babies and diaper rash, two key factors influencing consumers' diaper selection.

3.3.2 Biodegradibility Test of Diaper Core

This test is greatly influenced by the presence of TDPA in the absorbent core. By applying the TDPA test for the insert, it gives us the estimated number of days for the whole absorbent pad to degrade.

First thing we did was to expose the treated absorbent pad samples to a weatherometer (ASTM-5208). Then we measure the percentage elongation and tensile properties (ASTM-1682-64). Gel Permeation Chromatography (GPC) tests proved an important reduction in the average molecular weight of the samples. At simulated outside weather conditions the samples not only degraded, they degraded too fast. Future trials helped us fine-tune the TDPATM active ingredient to our current needs, to avoid insufficient shelf life. Our current product degrades in actual outside weather conditions in average 40 days.

We also carried out tests using forced convection ovens (ASTM-D5510-94) at different temperatures (without any light). We were able to correlate the effect of the temperature in relation to the degradation process. Using the "Arrhenius equation" as a mathematical representation of our data, we were able to forecast shelf life at different temperatures and fine tune the dilution rate for TDPA. Gel Permeation Chromatography tests were made to the heat aged samples, proving again an important reduction in molecular weight, similar to the QUV aged samples. These experiments demonstrate that the product degrades with ultra-violet-light, and also with heat with no light, they have also helped us in forecasting the time required for degradation at different temperatures.

Figure : Artistic representation of the degradation process

3.4 Eco Label

3.4.1 Certification and Endorsement of Our Product

EcoBaby Malaysia has been successful in manufacturing one of the first Eco-Diaper available locally in Malaysia. We assure our consumers that our Eco-Diaper will live up to our environmental friendly promise and will degrade in 40 days after disposal.This important feature of our product help to lessen the number of undegradable diapers in our landfill.

SIRIM is a government-owned national organization of standardization and quality, and the prime mover in industrial research and development. SIRIM QAS International Sdn. Bhd., a subsidiary of SIRIM, is the leading certification and testing body in Malaysia and has achieved wide recognition nationally and internationally.

Therefore,with great confidence and belief in our product, we applied for Eco-labelling under SIRIM and we have succesfully obtained our endorsement. Eco-labelling is a scheme that endorses product that claims to be eco friendly. This information provides consumers and business the associated environmental benefit and enables purchaser to make decision based on environmental attributes. In order to obtain Eco-labelling, the product has to be tested independently according to the preset product's criteria. With this eco labelling in hand, it is our hope that our Eco-Diaper could further instil confidence in general Malaysian consumers regarding our product's excellence.

This has allowed us to gain a competitive edge over other diapers and helps us to brand ourselves as the pioneer of green diapers in Malaysia.


Identify relevant

Product for Claims

Organization identifies the product and review against

the Eco-label product criteria.

Send Product for

Testing at

Accredited Lab

Feasibility study on

Product against

Product Standard

Organization conducts feasibility study and testing

against the SIRIM Eco-labelling Criteria.

Submit Application to


Request, sign and return Application Form and pay the

application fee.

Processing of

Application by SIRIM

QAS Intl

- SIRIM QAS Intl to determine the feasibility of the


- Applicant and SIRIM QAS Intl sign agreement.



SIRIM QAS International verifies the manufacturer's

application by:

- Reviewing testing result from Accredited Laboratory.

- On-site inspection to verify the information

Preparation of


Prepare product evaluation report

Submission &


Recommendation for Approval


On-going monitoring to maintain compliance to the scheme

4.0 The Lifecyle Analysis

A Life Cycle Analysis(LCA) is the investigation and evaluation of the environmental impacts of a given product or service caused or necessitated by its existence.

Here are the important points to consider when assessing the environmental impact of a diaper system:

How are they made and what is the impact?

How are they used and what is the impact?

How are they disposed and what is the impact?

Our product has been identified as a 'cradle-to-grave' product. Cradle-to-grave is the full Life Cycle Analysis from manufacture ('cradle') to use phase and disposal phase ('grave').. All inputs and outputs are considered for all the phases of the life cycle. Below are schematic LCA diagrams for both the diaper pants as well as the refillable insert:

Figure : LCA chart for diaper pants

Figure : LCA chart for refillable inserts