MANUFACTURING OF AIR BAGS

CONTENTS

• INTRODUCTION• RAW MATERIALS USED• WORKING PRINCIPLE• PROPERTIES REQUIRED• MANUFACTURING PROCESS• QUALITY CONTROL(PROS AND CONS)• OUR IDEA• CONCLUSION• REFERENCE

INTRODUCTION

• An air bag is an inflatable cushion designed to protect automobile occupants from serious injury in the case of a collision.

• One of the first patents for automobile air bags was awarded to industrial engineer John Hetrick on August 18, 1953.

• In 1988, Chrysler was the first United States company to install standard driver's side air bags

RAW MATERIALS USED

• Main parts of an air bag module are AIRBAG,INFLATOR, and PROPELLENT

• AIRBAG – nylon-6, nylon-6.6 woven fabric(coated and non coated)

• Inflator - stamped stainless steel or cast aluminium

• Propellant- in the form of black pellets, is primarily sodium azide combined with an oxidizer

WORKING PRINCIPLE

CHEMICAL REACTIONS

• Inside the airbag is a gas generator containing a mixture of NaNO3, KNO3, and SiO2

• REACTIONS:• 2NaN3 = 2Na + 3N2 • 10Na + 2KNO3 = K2O + 5Na2O + N2 • K2O + Na2O + SiO2 = Alkaline silicate

PROPERTIES REQUIRED

• High Tensile strength • High Tear strength • Low Air permeability • Good Heat capacity • Good Folding behaviour • Better Energy absorption • Good Coating adhesion • Reduced skin abrasion (softness) • Good heat stability

MANUFACTURING PROCESS

• Air bag production involves three different separate assemblies namely,

• PROPELLENT• INFLATOR• AIRBAG FABRIC• Some manufacturers buy already-made components,

such as air bags or initiators, and then just assemble the complete air bag module

PROPELLENT

• The propellant consists of sodium azide mixed together with an oxidizer

• Manufacturers receive sodium azide and oxidizer from outside vendors

• They are mixed together at sophisticated computerized process control

• After blending, the propellant mixture is sent to storage

INFLATOR

• Inflator consists of metal canister, the filter assembly—stainless steel wire mesh with ceramic material inside and initiator (or igniter)

• These sub components are received from outside vendors and assembled together

• The inflator sub-assembly is combined with the propellant and an initiator to form the inflator assembly

• The inflator assembly is then tested and sent to storage until needed

AIR BAG FABRIC

• Air bag fabric is most popularly made by using NYLON-6.6 fibers

• Dupont, Allied Signal, Akzo and Toray are the major fiber suppliers of airbags

• Both woven and non-woven fabrics are used • The fabrics used to make a driver and passenger’s

airbags are quite different• Driver seat air bag is coated whereas passenger’s

airbags are uncoated

AIR BAG FABRIC

• Sizing of yarns is made by one dip process which applies polyacrylic coating

• Generally, airbag fabrics are woven on rapier weaving machines or air jet looms

• When air bag material has been finished, it is cut into panels by laser and sewn with inflator assembly

FABRIC CONSTRUCTION

• Weave :- plain• No. of head used :- 4• Warp yarn :- 840 denier(twisted)• Reed space :- 50”• No. of ends :- 1400• Denting order :- Body - 1 in dent Selvedge - 2 in dent• Selvedge ends :- 2 x 20 = 40• EPI :- 30 ( 840 denier twisted) • PPI :- 36 ( 840 denier twisted)

Property Coated UncoatedAir porosity Precisely controlled Variable

Pattern cutting Easily cut More difficult

Sewing Easy to handle More difficult

Packageability Bulky Smaller package

Stiffness Variable Pliable top moderate

Burn thru Good resistance Not good

Deployment Excellent control Combing effects

Cost High Low

Recyclability Difficult Easier

QUALITY CONTROL

• Propellants, before being inserted into inflators, are first subjected to ballistic tests to predict their behavior

• Testing is done for inflator system's ability to produce an amount of gas at a given rate, ensuring proper air bag inflation

• The air bags themselves are inspected for fabric and seam imperfections and then tested for leaks

OUR IDEA

CONCLUSION

• The market for airbags has reached the maturity level in the developed nations and has also been established in the developing nations like INDIA

• We as a Textile Technologists should contribute in development of such a products to make them economical for our nation.

REFERENCES

• Mukhopadhyay S.K. and Patridge J.F., Automotive Textiles, Textile Progress, The Textile Institute, 29(172), 1997.

• Journal of COATED FABRICS, Jan 1995• S.Adanur, Wellington series "Handbook of industrial

textiles", Technomic publishing,1995Walter Fung And Mike Hardcastle ‘Textiles in automotive engineering’ Woodhead Publishing Limited