microencapsulated fragances in automobile upholstery textiles. · microencapsulated fragances in...

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MICROENCAPSULATED FRAGANCES IN AUTOMOBILE

UPHOLSTERY TEXTILES.

Víctor Oliveras Mérida(p), Ph.D.

Engineering Projects Department. ETSEIB. UPC. Barcelona

SEAT Technical Center Innovation Strategy Chief

Maria Margarita González Benítez, Ph.D.

SEAT-UPC Chair Director. ETSEIB. UPC. Barcelona

Mª José Justes Azlor

SEAT Technical Center FAKOM and Fabrics Chief

Diana Badosa

ETSEIAT. UPC. Barcelona

Abstract

The aim of this project is to enhance the passenger sensorial comfort within the vehicle. An air freshener system based on micro-capsulate fragrances releases aromas only while the vehicle is being occupied. With this system the amount of fragrance released depends on the number of passengers inside the vehicle. Therefore waste of fragrance and troubles stemmed from an over-perfumed vehicle are minimized.

In our air freshener system, micro-capsulate fragrances are added to fabrics used to manufacture seat cushions. Micro-capsulate fragrances are micrometric particles of spherical polymeric shells which hold the active principles or fragrances. In solid, liquid or gas state, the active principles generate the pursued olfactory sense.

This project shows the results of both the optimum location and the amount of micro-capsulate fragrances needed in the seat cushion so that the passengers‘ sensorial experience is improved while the visual

quality and durability of the fabrics are guaranteed.

Key words: Fragrance; Micro-encapsulate; Upholstery; Comfort; Automotive.

1. Introduction

Automobile sector outstands for its great innovating activity and the urgent need for offering a product meeting the client‘s most unsuspected expectations.

In that sense, the effect of the smell in the vehicle‘s interior and its customization has been on research

for 5 years at the SEAT Technical Center.

The smell the vehicle user feels must be pleasant, making essential it to be released only when the user is inside and in the adequate amount according to the number of occupants. Likewise, it is very important to decide which layer or layers of the seat‘s parts will receive the aromatic substance, so its perception

and duration is optimum.

After a very brief description of seats in the automotive industry and the microencapsulated fragrances‘

releasing process, the experimental exercise carried out to determine the ideal location and minimal technical requirements for its use in automobiles will be detailed.

2. Automobile seats

The design for automobile seats takes into account mainly ergonomic conditions. The seat gets to be in contact with three fourths of the user‘s body.

"Selected Proceedings from the 15th International Congress On Project Engineering" (Huesca,6-8 July 2011)

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Besides taking the occupant‘s body, the seat should hold him/her, protect him/her and not to cause

fatigue with the pass of time. To accomplish it, it should reach the difficult balance between rigidity and comfort, and allow certain easy-movement quality once seated.

The driver‘s necessities should always and especially be taken into account, since it has to allow, besides

the mentioned functions, an easy and quick use of the seat‘s adjustments.

Moreover, according to the particular requirements of the seat‘s occupants, four groups of seats have

been distinguished regarding its design in automobiles: first row; second and third row, competition and children seats.

Figure 1: Adjustments considered in an automobile seat’s design

Seats are designed to perform different functions, classified in primary and secondary functions:

1. Primary functions:

- Comfort: ergonomics and holding capacity

- Safety

- Design: style, visually attractive for clients

2. Secondary functions

- Thermal comfort (heating/cooling) and fatigue (massage function)

- Active safety (warning systems)

Automobile seats consist of four parts shown in figure 2.

Figure 2: Main parts of a seat

Relleno

Tapizado

Armazón

Mecanismo


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3. Microencapsulation

Microcapsules are micrometrically-sized particles formed by a thin spherical polymer membrane (shell) covering an active principle in its interior (core). This active principle can be in liquid, solid or gas states and it is responsible for the sought-after effect.

Figure 3: Microcapsule structure

Techniques to obtain microcapsules are varied, and chosen depending on the characteristics of the active agent to encapsulate and the type of polymer material used as membrane.

Microencapsulation is the process by which tiny portions of an active principle are packed within a second material with the aim of protecting the active principle from the environment nearby.

Figure 4: Microcapsule Obtention Diagram

In order to be able to anchor microcapsules in the seat, some links are established between microcapsules and the textile substrate.

Fixation is performed applying a binder with the microcapsules in the fabric going through a thermal cure. During the process, the fabric will be exposed to high temperatures (130 - 170 ºC) for certain period of time (60 - 600 s), where the binder‘s components reticulate forming a polymer network covering

microcapsules.

The summary of different types of anchoring is shown in figure 5.

Figure 5: Anchoring microcapsules to fabrics

Igloo System:

- Very resistant to washing and use.

- Harder active agent release.

- Suitable for technical fabrics. Support System:

- Endurance guaranteed.

- Direct contact with skin.

- Easier active agent release

water + polymer essential oils

emulsion

evaporation

agitation

Membrane External Phase

Active agent core Internal Phase


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The system to apply microcapsules will depend on the machinery available; it could be foulard, exhaustion, spray or covering.

It is recommended to apply them at the end of the treatment, to avoid putting them under adverse conditions which could be detrimental for them and impede control over their dispersion, anchoring and amount of microcapsules in the resulting fabric.

4. Experimental Development

Physiological or sensorial comfort is subtle to appreciate; it is a sensorial analysis of the organoleptic properties of the fabric, sensed by sight and touch, the base of the project; the perception of smell in the automobile.

It is important to highlight the existence of a close relation between aromatherapy and smell, a sense that never shuts down, since we are constantly exposed to fragrances from the environment, nature, people or things, even when we are asleep.

Microencapsulation of volatile essential oils allows profiting, at home as well as at work, from aromatherapy effects and that is why they have been studied for their possible use in the automotive industry.

4.1. Fragrance Characterization

Not all fragrances produce the same feelings and evidently, not everyone has the same taste, so it is difficult to standardize a concrete fragrance to apply it to automobile upholstery.

A questionnaire was made to relate the interviewee‘s sex, age and car model variables to their favorite

fragrance type. The questionnaire was answered by 23 SEAT workers and 17 external people.

After a deep analysis of the data resulting from the questionnaire, the conclusion was reached that there‘s

no relation among the variables and fragrance types, and that fresh and more elaborate fragrances, such as cologne, outstand.

4.2. Applying microcapsules

The microencapsulated fabric consists of woven and knitted fabrics, enveloping foam.

Figure 6: Microencapsulated Fabric

Chart 1: Characteristics of woven and knitted fabrics, both 100% polyester

Woven (Jacquard) Knitted

Width Cm 176 205

Weight g/m2 270 30

Thickness Mm 0.6 0.33

Warp Density threads 36 8

Weft Density picks 22 7

The microcapsules used have been obtained through an emulsion, with a melamine/formaldehyde membrane, that is why it should be taken into account that it could release formaldehyde. The active principle encapsulated is essential oils.

Woven fabric

Knitted fabric

Foam


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The release mechanism is controlled release by breaking the membrane through a mechanical action. In order to be able to follow continuity, it was decided to use the foulard process.

Chart 2: Product Concentration Chart

Product Units Concentration

Microencapsulated g/l 30

Binder g/l 50

Three possible ways to apply microcapsules on the fabric were seen: only impregnating the upper side, impregnating upper and lower side or only lower side.

After the fabric‘s foulard process, it was dried and polymerized, foamed and, in order to perform a quality

check on the fabric‘s upper side, it was decided to observe the visual aspect, performing a Schopper abrasion test and analyzing it under an electronic microscope.

During the entire experimental process, the standard, untreated fabric is compared to microcapsule-treated fabric.

Figure 7: Appearance of the upper side of the fabric

Figure 8: Appearance of the upper side of the fabric after Schopper abrasimeter test

Figure 9: Visual evaluation of the upper side using an electronic microscope with and without

abrasion

For the lower side, the fabric equally passed a foulard process, it was dried, polymerized, and it was decided to perform the quality control only by electronic microscope evaluation.


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Figure 10: Visual evaluation of the lower side using an electronic microscope with and without

abrasion

Figure 10 shows damaged microcapsules, possibly broken during the foaming process.

It is considered important to demonstrate the presence of microcapsules before the coating processes the fabric undergoes are finished, reason why the influence of manipulation is assessed.

In order to control this influence, it is decided to eliminate the foaming process and evaluate the resulting fabric using an electronic microscope.

Figure 11: Appearance of the fabric’s upper and lower sides without foaming seen through

electronic microscope

UPPER side LOWER side

WITHOUT abrasion WITH abrasion

CON ABRASIÓN SIN ABRASIÓN WITHOUT abrasion WITH abrasion


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It has been proven that many microcapsules break while manipulating the fabric and applying the product in the upper side damages the fabric too much. That is why comes up the need for applying the same product over option C (lower side or cover), but less concentrated in microcapsules, to guarantee a greater durability of the coating.

Further studies could value the influence of fabric manipulation over microcapsules during the entire seat assembly process.

4.3. Chosen option development: fabric impregnated only in the lower side or lining

After observing the results in samples using the three options of impregnation, it was decided to develop the fabric impregnated only in the lower side or cover.

The concentration of the microencapsulated product was increased to 150 g/L, 5 times more than the previous option and the fabric was visually evaluated with the electronic microscope before and after the foaming process.

Figure 11: Appearance seen through electronic microscope before and after foaming

We can say that the foaming process destroys microcapsules, but not in a great extent and it was observed that using a concentration of 150 g/L, there are many more microcapsules and the difference before and after manipulation is not substantial in a visual level.

For the location of the scented fabric in the seat, measuring and simulation of the pressure users exert on the seat‘s surface were carried out, obtaining the distribution shown in figures 12 and 13.

In the biggest exerted pressure zones is where the greatest concentration of fragranced microcapsules should be guaranteed.

UPPER side LOWER side

Before After


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Figure 12: Pressure Distribution in the seat

4.4. Design of a fragrance release evaluation instrument

Since it was a highly innovating project in the R&D activity of the SEAT Technical Center, there wasn‘t

any device to help simulating the fragrance release and evaluating the amount of microparticles destroyed and the durability of the application in a seat.

That is why a seat pressure simulator was designed using two wooden blocks enveloped in fabric, which are pressed one against the other as if it was the seat stool and the user‘s trousers.

The fragrance used for this experiment was peppermint, because it is easy to recognize.

Figures 13 and 14 show the simplicity of the applied concept.

Figure 13: Fragrance release instrument scheme

Figure 14: Seat pressure instrument

Weight 7,5 kg

Wood covered in fabric

FOAM

Wood

FABRIC


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After 500 cycles, a scarcely noticeable smell is perceived.

After 2000 cycles, the peppermint fragrance gains intensity, but it is still camouflaged.

After 3500, the peppermint scent is noticed with less intensity than in the previous case, creating a pleasant atmosphere. When smelling the fabric‘s sample directly, the fragrance was clearly noticed.

The scent applied in the fabric goes through woven fabric and foam layer, being able to be felt by the user and creating a pleasant atmosphere, without turning it stuffy.

5. Conclusions

In order to guarantee the product‘s feasibility, an estimation of the price increased was carried out, based

on the estimated prices of needed products and processes, as shown in Chart 3.

Chart 3: Estimated Price

Process / Product Estimated Price

Fragrance Development 75 € / kg

Fragrance 55 € / kg

Resin 2.5 € / kg

Foulard 0.04 € / linear m

Unfinished Fabric (Set) 7.01 € / m2

The estimated price increase per seat is 0.094 €/seat, indicating that this project also has an economic

appeal to be developed.

Applying microcapsules in the lower side or cover also brings an advantage in the industrialization of this project, since it eliminates the complexity solving each woven fabric (central) per finishing process and vehicle model.

In order to be able to value the possible loss of product during the seat‘s industrial process (cutting and

making the cases, transportation and assembly), it is vital to perform an industrial test.

As a brief summary, we can conclude that:

- Encapsulated fragrances must be researched and manufactured scent. - The upper side impregnated is negatively affected after abrasion (to visual level and by product

loss). - It is recommended to develop the fabric with the lower side impregnated and place it in the seat‘s

cushion. - The fabric is recommended to be used in the so-called action models or special, short series. - The air freshener only releases fragrance when the vehicle is used and in greater or lesser

quantity depending on the number of occupants. - The results also lead to the idea of using the product on other textile components of the

automobile. - Although durability hasn‘t been certainly determined, in case someone wants to extend it, there

could be a research on the way of making some zones of the seat extractable to be reloaded. - It should be always remembered that microcapsule technology is very open, and different active

principles can be encapsulated.

Contact details (For further information, please contact)

Victor Oliveras Mérida

E-mail: [email protected]


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