[dot]

For a long time I have been thinking to start a topic which will discuss how different materials and technologies find applications in various facets of car manufacturing process.

This might sound boring for many. After all, we primarily love to rip it, own it, enjoy it. But just maybe, it might be worthwhile to know some of the amazing stuff that goes inside (and outside) our vehicles.

I dont claim to be an expert in automobile engineering or manufacturing. Far from it actually. My interest is from my profession which has allowed me to be in touch with plastics and chemicals for the last so many years. Been fascinated by the clever use of so many mundane stuff in so many innovative and clever ways which help to make a modern car run and last better. Therefore I will ask and seek opinion from folks who know and understand much more. Please write, augment, supplement whatever topics we plan to discuss. That way we continue to learn.

So the plan is to describe
1. Plastics
2. Foams
3. Paint and Coatings.
4. Sealants and Elastomers
5. Composites.

specifically from automotive view point.

We will not describe fluids like engine oil as they have been discussed extensively elsewhere. Also, whatever we will try to describe will be from personal experience. Not googling.

I plan to take it slowly and build a mini-knowledge base. So to start, lets look at a general way on how cars are manufactured in a plant.



Typically things first start at the body shop where body elements come together and by the time it leaves for painting, from sheets and rods a car has been born.
Then the body travels to paint shop where a rigorous paint process is followed. Paint not only needs to look good, but it has to last well and weather the elements.
In the meantime, engine, transmission has probably been mated elsewhere in the plant. And it waits for the body to show up in the assembly line. Once the mating occurs, rest of the assembly follows very quickly. Suspension, drive assemblies, electricals are added as modular units. Windshields are bonded by sealants. Interior and exterior plastic trips are bolted and clipped on. Seats are installed. By the time the whole thing reaches the end of the line, a real car is ready to fire for the first time.

In the picture the role of auto ancillaries have been highlighted several times. They are the B2B units specializing in a key aspect which ultimately leads to a larger unit. Each of these unit is vital for the manufacturing to survive. And it is usually these units which take up the materials and form them into the parts that we see everyday. The endeavor will be to describe how parts are selected and manufactured.

Hope you find this interesting.

[Swanand Inamdar]

Great going Dot!

With the Doctor of all things chemical, this one is going to be a hell of a read. Yes, may look boring at a glance, but then, one who has even an iota of interest in cars (and what goes in it), will be immensly blessed with this read!

Go on.. spread the knowledge.

[dot]

Lets start with Plastics and have a glimpse on how they are made.

Most engineering plastics origin from Crude oil and Natural gas. These are cracked in refineries where basic molecules are formed. Chemical plants convert basic molecules into monomers. Many times these conversion takes place in several steps. Will not go into greater details but will point out that since these monomers are manufactured in millions of tons per annum, therefore prices are low and range around 1-2$/Kg.

The following picture shows the process and how crude oil is converted to car parts.



Monomers are polymerized to polymers. Each family of polymers like polyethylene, polypropylene, polycarbonates, polyesters, polyamides (Nylon) are made under different conditions. Typically back-end plants makes polymers which are shipped in powder or pellet form.

Next in the value chain are the formulators. These guys could be within the same mother plant. They mix different components like fillers, additives, colors etc and make pellets which are many times ready for molding. Bags of pellets are shipped to OEM via distributors or company's own supply chain.

OEM converts pellets to parts by molding them under temperature and pressure. Typically parts are injection molded. OEM sometimes also have the means to modify formulation as required by specs.


Next we will look into some classes of plastics and how they are used in vehicles.

[Guderian]

Originally Posted by dot

For a long time I have been thinking to start a topic which will discuss how different materials and technologies find applications in various facets of car manufacturing process.

Fabulous thread dot ! Though many of the things might be known to few of the folks folks to are deep into it, a thread like this does disseminate knowledge among folks who want to gain all these pieces of information but were too shy to ask (due to age and/or other factors...like ego...?) or didn't know whom to ask or where to look.

For some of us back to school boy and college Chemistry/Physics and sometimes Math.

Delightful indeed and will be having a good dekko at this thread in the days to come and chippin' in wherever I can.

[Guna]

Nice thread.
Also, some of Plastic parts coming out of injection molding are pigmented (like the interior trims) and some are just gray and would go through painting (like the bumper)

[selfdrive]

Rocking idea dotty sir! Immensely helpful to me definitely as a learning point. Now I will know as much as my chaddi buddies from school who had their ancillary workshops providing accessories to auto biggies. Well, you get the drift

keep it going, I am all ears. I hope you have geared yourself up for some basic questions from me! I am delighted

[SPIKE ARRESTOR]

Originally Posted by dot

Lets start with Plastics and have a glimpse on how they are made.

--------

Next we will look into some classes of plastics and how they are used in vehicles.

Good topic for discussion Dot.

Once you are over with the basics, would like to know more about the latest trends in Automotive field w.r.t. materials science. Also how ELV and light weight designs are influencing product development.

Let the discussion continue.

Spike

[subodh]

Hey Dot, Nice Thread. I was working with a company which used to design products for auto companies. We had worked on various products like cup holders, Door handle and ash trays for various car companies. We were also pitching for design of the new XUV 500 central console but it did not work out. Most of the car is manufactured by the auto ancillaries companies and only thee parts are assembled in the main company factory. I have seen the process of injection mounding being done and how products are manufactured and there is an inbetween step where products are designed and i would like to add my 2 cents regarding the same if you dont mind.

After the materials are brought to the factory and before they are processed, there is a very interesting process of product design. This is the process where auto companies spent the maximum amount of time. The car is broken down in very small components of plastics, sheet metal fiber glass etc and each and every component is designed individually. Now the process behind designing these components is very complex as every product has to be engineered in terms of fitting in the overall puzzle as well as it has to be manufacturing friendly. Product designers spend months over designing small components like door handle or a cup holder. if it has some kind of hinge then it takes more time. Once the design has been made in 3d softwares, it is sent to make the prototypes. once the prototypes are ready, it is sent back for iterations, re engineering and again prototyping until the time the product does not become perfect (or so called)

Once the prototype is ready, molds are made for these products to be manufactured on large scale. Making these molds is also a very costly affair and there are specialist people who are involved in this process. Since the quality and finish of the products is dependent on the molds, this is a very critical step in manufacturing and once the molds are ready, the products are manufactured on large scale mostly at one of the component supplier's factory.

[dot]

Originally Posted by Swanand Inamdar

Go on.. spread the knowledge.

Originally Posted by Guderian

Delightful indeed and will be having a good dekko at this thread in the days to come and chippin' in wherever I can.

Originally Posted by selfdrive

keep it going, I am all ears. I hope you have geared yourself up for some basic questions from me! I am delighted

Thanks guys. As someone had said, knowledge is nothing if not shared and discussed. So please, let this be a two (or multi-) way dialogue.

Originally Posted by Guna

Also, some of Plastic parts coming out of injection molding are pigmented (like the interior trims) and some are just gray and would go through painting (like the bumper)

Thats right. Depending on the need fillers and colors are added. Interior parts do not normally need additional painting so the parts are molded with color. Bumpers would be painted according to car trim and color, so they need to be in some kind of neutral shade. Most bumpers are made from polypropylene/rubber blends these days. Their original color is typically opaque white. Grey/Black color comes from fillers which are needed to boost strength, increase adhesion to color and save on cost. We will talk about these aspects later.

Originally Posted by SPIKE ARRESTOR

Once you are over with the basics, would like to know more about the latest trends in Automotive field w.r.t. materials science. Also how ELV and light weight designs are influencing product development.

Wow, that would be nice. I could certainly comment on the choice of materials and process.

Originally Posted by subodh

Product designers spend months over designing small components like door handle or a cup holder.

Once the design has been made in 3d softwares, it is sent to make the prototypes.

Once the prototype is ready, molds are made for these products to be manufactured on large scale. Making these molds is also a very costly affair and there are specialist people who are involved in this process.

Thanks for sharing. Yes, designing any part is a very complex. I have also seen people working in CAD and turning, twisting and modifying a so called simple thing like a glove box cover for eons. And you also made an extremely important point of deciding which type of molding process that one should use from the cost perspective. I have a basic illustration below.

---------------------------------------------------------------

Now that we have seen how polymers are made, lets look at two classes of polymers that kind of decide their usage and fabrication process. The following diagram illustrates the two classes, thermoplastics and thermosets.



Thermoplastics can flow when heated beyond a particular temperature and can be recycled.

Thermosets, once set or cured, cannot flow; it simply softens beyond a particular temperature. They can be used only once.

These two classes have individual processing techniques according to their flow properties.

Typically thermoplastics are injection molded. Other techniques of making a part of thermoplastics are,
2. compression molding
3. thermo or vacuum forming
4. blow molding
5. rota molding.

Many times injection molding and compression molding can produce similar parts. If the parts are very complicated, like sharp corners, lots of ribs, injection molding is the preferred way. However, typically compression molding is easy to impliment, since, just as Subodh pointed out, mold making in injection molding is a very costly affair. So number of parts decides which technique to use. Following is a plot which points cost vs number of parts and which technique makes more sense at a particular regime.



Thermosets parts are made from many techniques, some popular ones being Reaction Injection Molding for PU and Vacuum bagging for epoxies. We will talk about thermoset fabrication techniques later.

Depending on material property, a material is chosen to make a desired part. Typically cycle times for thermoplastics are faster. So for parts that needs to be made in large numbers, thermoplastics are used. Looking at this point from a different angle shows that thermoplastic parts are relatively less expensive. Therefore where-ever possible thermoplastics are used.

Thermosets are chosen where their material properties dominates the decision of choice of materials. For example foams can be made from thermoplastics or thermosets, but for seats only PU is used due to a combination of superior properties like softness, compression set, longevity etc.

Next we will look at a few individual thermoplastic polymers and where they are used in cars.

[noopster]

Dotty, great idea for a thread and it's nice that others are also chipping in since this will result in this becoming the default thread for automotive materials discussions. I loved the tone of your "lectures" and the easy-to-follow visuals. For a moment took me back to my Industrial Organic Chem classes in Engineering days but those were nowhere half as interesting!
Am sure you will get to it eventually but what determines hardness/touch and feel of the plastic and how do carmakers test this? I often think Indian carmakers don't invest wnough in softening up the dashboard and other interior plastics even in the premium
segment.

[amitwlele]

Wonderful thread dotty.

I would only be a student and just go through it for all the new learnings. Your efforts in putting up the illustrations is greatly appreciated.

So you have a detailed flow in mind or would like to thread evolve as it goes along with contributions from others?

[dot]

Now that we have looked at some classification of plastics, we will focus on thermoplastic materials and how many of the well known ones find usage in vehicles. It is not a wonder that every large or small plastics company worth its salt has an automotive division for the very precise reason.

In olden days polyethylenes (PE) and polypropylene (PP) were thought to be inferior to so called engineering thermoplastics like polycarbonate (PC), ABS (acrylonitrile-butadiene-styrene terpolymer), polyamide (Nylon), etc. It was due to the superior mechanical strength and high heat resistances of engineering thermoplastics than many car parts were made from these guys only.

But recent advances in polyolefin technology have seen many applications turning towards PP or PE. Moreover cost competitiveness of PP is also a factor.

Still when it comes to surface finish combined with strength, PC, PC-ABS or ABS still rules. When it comes to parts which needs to tolerate high heat, like under the hood applications, polyamide family are chosen. Interior parts are decided by cost vs aesthetics. Typically PP is used in low end cars while ABS or ABS-PC is used in high end vehicles. For parts which need exceptional dimension stability Polyphenyleneoxide (PPO) or Polyoxymethylene (POM) are used. The soft touch dashboard we see in may high end cars these days is PVC (polyvinylchloride) overmolded over foamed PU.



Typically fillers are added in most parts. Glass, talc, mica, calcium carbonate are widely used as fillers. Fillers give rise to additional strength, many times increase heat resistance as well as save on cost.

Parts has to meet OEM specs and few vendors qualify. Those companies who are in first many times set the specs, making it difficult for others to penetrate the market. Most parts are injection molded.

I am not including global volumes of PP, PE, PC etc. If someone has a specific question, do post that. My next post will be a quick and small one liner type on how these polymers are made.

[dot]

As promised before, let me briefly mention how some key engineering plastics are manufactured.

Polyolefins like polyethylenes and polypropylene family are mostly made by catalytic polymerization of ethylene and propylene molecules respectively.

Catalysis is still an active field of research, trying to find more precise control over polymer structure is important to make newer materials with enhanced properties. For example, bumper parts are made from PP with rubber (EPDM) particles or dispersed phases to enhance toughness. However through research better polyethylene family copolymers are available these days which gives enhanced toughness in PP bumper parts. Such materials were not available in the past.

Polystyrene, ABS, SAN (Styrene acrylonitrile), acrylics are made from a different technique called free radical polymerization. These free radicals are similar to free radicals which causes skin and cell related issues, so widely covered by the popular media. But here they are harnessed to make useful products.

PC, Polyamides, Polyesters (PET), Polysulfones are made from a technique called condensation polymerization where two monomers first form a dimer. Two dimer forms a tetramer. Two tetramers form a octamer. And so on. PC is made from Bis-phenol A or BPA which is also a building block of epoxy. It is interesting to know that in BPA plants, best grades are used for PC as they have to optically clear which is key in most PC applications. Lower grades of BPA goes for making epoxy where optical clarity is not required.

This leads me to another small list. Of optically transparent and clear materials.

PC
Polystyrene
SAN
PET
PMMA (Plexiglass or acrylic)
Some grades of PP and PE.

Of these PC has been known and probably continue to be the "god" of polymers. It has fantastic range of properties like strength, toughness, optical clarity, good heat resistance. It can be made fire retardant too. It is the material used in CDs. No wonder that PC continues to be the choice for headlamp covers. Here are some pictures of other applications where PC is used.







When it comes to high heat resistant polymers, polyamides, blends of polyphenyleneoxide and polyamides, and polysulfones are materials of choice. Of these, filled polyamides find larger usage in under the hood applications, possibly from price-performance point of view. Take a look at a picture of the radiator duct on a Safari.



It says PA66 GF30, which means it is made from 30% Glass filled polyamide66, a grade of polyamides.

With this we will move on to foams.

[Guna]

Originally Posted by dot

This leads me to another small list. Of optically transparent and clear materials.
PC
Polystyrene
SAN
PET
Some grades of PP and PE.

Are acrylics not used?

[dot]

Originally Posted by Guna

Are acrylics not used?

Thanks for pointing that. It was a typo. I will ask a mod to modify the list. Moreover, I will not be surprised to know that tail-lights of some vehicles are made from plexiglass.