MANUFACTURING OF HONEYCOMBMATERIALSPROCESSING ELASTOMERSREINFORCED PLASTICS
Definition of Elastomers An elastomer is a polymer with the property ofelasticity generally having high yield strain comparedwith other materials. Some of the material can be stretched to several timefrom their original position this is due to the elasticproperty of the material.
Schematic DrawingFig A is a schematic drawing of anunstressed polymer. The dots representcross-links.B is the same polymer under stress.When the stress is removed, it willreturn to the A configuration.
HistoryThe origins of Kraton Polymers and its role in thedevelopment of styrene-based thermoplasticelastomers can be traced back to the U.S. governmentsSynthetic Rubber (GR-S) program during World War II.Between 1942 and 1945 this program developed a newstyrene butadiene synthetic rubber (SBR) and builtplants to provide a critical alternative to natural rubberfor making tires for military vehicles during the war.
Shell Chemical Company, who was a butadienesupplier to the SBR plants, bought one of theplants in Torrance, California, when thegovernment decided to sell its holdings in 1955.This newly formedElastomers Division of ShellChemical evolved into whatis today Kraton Polymers.
PolymerizationThe beginning step for elastomers isthe polymerization of themonomers.Polymerization combines two or moreprocess gases (monomers) underspecific temperature and pressureconditions connects the individualmonomers into the desiredpolymer.Initiating agents, chemicals may beadded to the polymer reactor toachieve the desired chemicalproperties and polymerizationdynamics.
Isolation & CompoundingThe backbone polymers are isolated (brought out of theemulsion), cleaned and dried.Chemical agents may be added atthis step to isolate the polymer formore usable form. Once thepolymer is cleaned and dried, thepolymer is shipped to compoundersfor mixing.
ExtrusionThe sheet compound is extruded into a configurationsimilar to the desired finished.
MoldingMost of the elastomeric O-rings used in thesemiconductor industry are compression molded.A preshaped form is inserted into a multi-sectionmold and transferred to a heated press.Under heat and pressure, the elastomer flows intothe mold cavities and chemical cross-linking takesplace.After a period of time ranging from several secondsto several minutes, the parts are removed from thehot molds.
Flash RemovalAfter the parts are removed from the molds, theycontain thin "flash" as a result of the elastomerflowing in the multi-section mold.This "flash" is typically removed by processes.
Curing• Elastomer parts are exposed tohigh temperatures in carefullycontrolled environments forseveral hours to complete thecuring process.• Additionally, this post-curingstep removes excess watervapor and volatile processadditives, thereby improvingvacuum and contaminationperformance.
Finishing and InspectionAfter the parts are removed from the curing ovens, theparts are again cleaned and inspected to ensure theparts meet the material and dimensionalspecifications.
Cleaning and packagingAcceptable parts are delivered tcleaning and packaging.Acceptable parts are then counted and packaged,either individually, in a heat-sealed clean inner o theclean room forbag.
Synthetic ElastomersAcrylic Elastomers:Exhibiting the attributes of high-performancedurability, These acrylic elastomers are useful invarious industries that are mentioned belowAutomotive power train sealsGasketsEPDM(Ethylene propylene diene monomer) elastomers:It is synthetic rubber,elastomer . Useful inthe manufacturing of rubber sheets andvarious industries, have good resistance towater-based chemicals, vegetable-basedhydraulic oils and outstandingheat, ozone, and weather resistance.
Neoprene Elastomers:It has good chemical stability maintainsflexibility over a wide temperaturerange . These are used in manyindustries for the manufacturing of thefollowing:Car fan beltsGaskets and laptop sleeves.Thermoplastic elastomers:Thermoplastic elastomer eliminate andcan be processed into products by all ofthe conventional thermoplastic polymerprocess[ injection molding, extrusion,blow molding, thermoforming andothers].
Silicones:Silicones have the highest useful temperature rangeof all elastomers, up to 315 ̊̊̊̊̊̊̊̊̊C, but their otherproperties r inferior to those of other elastomers.Typically used in the production of seals, gaskets,thermal insulation, high temperature electricalswitches, etc.
AdvantagesExcellent impact resistance.Easy color ability.Tough yet flexible.Low density and light weight.Easy forming and processing.Recyclable for in-process scrap re-use.Excellent melt strength and process ability.Lower shrinkage.
DisadvantagesHigh cost of raw materials.General inability to load TPEs with low cost fillers suchas carbon.Poor chemical and heat resistance.High compression set and low thermal stability.Soften or melt at elevated temperature above whichthey lose their rubbery behavior.Show creep behavior on extended use.
ElastomersHeavy in weight.Maximum elasticity.Recyclable for in-processscrap re-use.Lower shrinkage.Excellent impactresistance .High production cost.PlasticsLight in weight.Comparatively Lowerelasticity.Recyclable for in-processscrap re-use.maximum shrinkage .Lower impact resistance.Low production cost.Comparison Between Elastomers & Plastics
Applications of Elastomers in Pakistan industryUse in the making ofpower and hand tools, andshoe midsoles in Bata &Service industry, etc.Daily routine things likedishwashers, clothes dryers& washingm/c, refrigerators seals arealso made in SuperAsia, Pel, Waves, Orient, etc.
Applications of Elastomers in Pakistan industryIt is also used for the productionof construction material likeresidential glazing seals, roofsheeting in cars, bus, trucks, etcin Hino , Honda, Suzuki, Toyotaindustries.It is also used for the productionof tiers of vehicles inService, Panthers, Yokohama &Dunlop tiers industry.
Applications of Elastomers in Pakistan industryElectricity things like , low-voltage industrial wireand cable can be made by elastomers. In Pakistancables, Ittefaq cables, etc.
HONEY COMB STRUCTURE•Honeycomb structures are natural or man-madestructures that have the geometry ofto allow the minimization of thehoneycombaamount of used material to reach minimal weightand minimal material cost. The geometry ofhoneycomb structures can vary widely but thecommon feature of all such structures is an array ofhollow cells formed between thin vertical walls
Material use for honeycomb structureHoneycomb provides a unique structure made from awide variety of materials includingthermoplastic, fiberglass, carbon, aluminum andsteel
Hexagonal cellThe non angled rows of honeycomb cells are always horizontally (notvertically) aligned. Thus, each cell has two vertical walls, with "floors" and"ceilings" composed of two angled walls.
Rectangular cellRectangular cells give easier forming in the W direction
Manufacturing of honey combThere are two method for making honey combstructure1. HOBE (honey comb before expansion process)2. Corrugated process
Composite Honeycomb StructureSandwich structure is comprised of layered composite materials formed bybonding two or more thin facings or face sheets to a relatively thick corematerial.
Comparison between honeycomb material and metalInexpensiveLight in weightEasy to handleHoneycomb materialexpensiveNot light in weightNot easy to handleMetals
Advantages•From a mechanical point of view:- they are light- they don’t curve under their own weight- they are shock absorbers- they accept significant distortions without breaking•From a chemical point of view:- they are water and corrosion resistant- their behavior with respect to bacteria is excellent.They resist to most acids and bases.•From the insulation point of view:- they are heat insulators- they absorb vibrations•From the implementation point of view:- they are easy shaping- they can be easily cut with standard tools- they can be easily transported
Military ApplicationHoneycomb structure design isone of the Several improvementsmade in military defense toprotect against the ambush orexplosives. This will not only takebullets but also explosions froman improvised explosive device
Reinforced Plastics:“Fiber reinforced plastics are a category ofcomposite plastics that specifically usefibrous materials to mechanically enhancethe strength and elasticity of plastics.”
50Reinforcing fibersGlass – most common and the least expensive, high strength, low stiffness andhigh density. GFRP consists 30-60% glass fibers by volume.– highest specific strength, toughest fiber, undergoes plasticdeformation before fracture, but absorbs moisture, and is expensive.Aramids (Kevlar)– boron fibers consist of boron deposited on tungsten fibers, highstrength and stiffness in tension and compression, resistance to hightemperature, but they are heavy and expensive.Boron– more expensive than glassfibers, but lower density and higher stiffness with high strength. The compositeis called carbon-fiber reinforced plastic (CFRP).Graphite (99% carbon) or Carbon (80-95% carbon)The average diameter of fibers used is usually less than .0004 inch (.01 mm). The tensilestrength of a glass fiber could be as high as 650 ksi.
Types of Reinforce Plastic fibers•Three main types of fibers–Fiberglass–Carbon fiber or Graphite–Organic fibers, aramids (kevlar)
Fiberglass• Spin molten glass• Different types of glass can be made– E-glass (improved electrical resistance)– S-glass (high strength)– C-glass (high chemical resistance)
Carbon or Graphite Fiber• Made from PAN fibers, pitch or rayonfibers• Through heating, raw material loosesmost non-carbon atoms in the chain• Processing also aligns carbon chains• Carbon fibers have very high modulus(stiffness)
Organic Reinforcement Fibers• Aramid fibers have greatest strength andmodulus properties of organic fibers• Kevlar is the most commonly used aramidfiber• Aramids are strong and stiff but theirgreatest value is in impact applications– Front of airplane wings– Armor applications
Processes Of Making Fiber ReinforcedPlastics:F.R.P Involves Two Distinct Processes:1. The first is the process whereby the fibrous material ismanufactured and formed.2. The second is the process whereby fibrous materials are bondedwith the matrix during the molding process.
Manufacturing Methods• Roll wrapping– Limited to symmetrical mandrels
Manufacturing Methods• Pultrusion– High volume production– Comparable to extrusion but the mainprocessing force is tension– Profile is pulled from the machine
Advantages and limitations:• Glass reinforced polymers are strongest andmost resistive to deforming forces when thepolymers fibres are parallel to the force beingexerted.• Weakest when the fibres are perpendicular.
Advantages:• Weight Saving• Precision Engineering• Finite Tolarance• Simplification of parts in production andoperation.• Cheaper• Faster• Easy to manufacture.
COMPARISON:Fiber ReinforcedMaterialsSteelHigh Material Cost Low Material CostLow Installment Cost High installment CostNon Corrosive CorrosiveLight in Weight Heavy in weightLow Maintenance High Maintenance