# Not all plastics are "acrylic"



## Sylvanite (May 22, 2017)

Please forgive my rant, but I've noticed a growing tendency for posters here to refer to all types of man-made pen blanks as "acrylic".  A number of threads started this year are all about how the different "types of acrylic" (from Inlace Acrylester to Alumilite) turn, and the techniques and tools best suited to each.

This looseness of terminology disturbs me.  While many suppliers sell blanks made of acrylic thermoplastic, most of the plastics discussed are NOT acrylic.  Inlace Acrylester is NOT acrylic.  Neither is polymer clay (PVC), RhinoPlastic (polyester), Alumilite (clear or opaque - both urethane), WEST System (epoxy), nor TrueStone (trade secret composite).  Bakelite, Ceboplast, casein, polycarbonate, and Ebonite are other non-acrylic materials.  Only poly-methyl methacrylate (PMMA - brand name "Plexiglass", "Lucite", and "Perspex)) is acrylic.

Perhaps the distinction doesn't seem important to many, but the turning, sanding, and finishing properties of acrylic are quite different than those of other synthetic pen blanks.  Mixing up the terminology when discussing different materials only leads to confusion and error.  For example, don't take a polymer clay pen to an engraver and tell him it's acrylic.  He'll be very upset with you.  Acrylic is easy to laser-engrave, but PVC releases toxic and corrosive gas when lasered.  It can potentially damage the laser optics or injure someone.

Think of it this way.  What if a penmaker referred to all types of wood as "oak"?  If he started a thread about the different properties of various "oaks"?  If he said "black palm oak" was much more difficult to turn than "rock maple oak"; how "lignum vitae oak" tends to gum-up sandpaper; how "teak oak" dulls tools; and about wiping oily blanks like "cocobolo oak" with acetone before applying a CA finish?  Would you join in and talk about different "oaks", or would you mention that none of the above woods are oak (and that technically, palm isn't even a wood at all)?

I apologize if I'm nit-picking, but it irks me to read that "acrylic is difficult to turn" when the poster is using Inlace Acrylester, or some other plastic that isn't acrylic.  Acrylic is one of the easier plastics to turn, sand, and finish.

Regards,
Eric


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## gbpens (May 22, 2017)

Eric you are right on! We tend to lump many varieties under on umbrella thus distorting details and definitions which as you point out can lead to serious consequences. We all need to educate ourselves on the chemical makeup and technical attributes of the materials we use.


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## D.Oliver (May 22, 2017)

This is good info.  I've probably mixed up the terminology, myself.  AA stands for Acrylic Acetate, right?  I'm going to assume that Acrylic Acetate is an Acrylic Thermoplasic.  Is that correct?


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## bmachin (May 22, 2017)

Eric,

Amen! 

 I've thought about doing the same rant, but you beat me to it and did a much better job of it.

Bill


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## duncsuss (May 22, 2017)

bmachin said:


> I've thought about doing the same rant, but you beat me to it and did a much better job of it.



+1

Thanks!


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## leehljp (May 22, 2017)

There needs to be a clear chart on what is what. Without that, reading in paragraph form will only confuse many. Paragraphs work when everyone is on the same page and understand the differences clearly.

Each kind of material needs to be named on a line with an explanation out from it; 

And skipped line between each one. 

But you do have my (our?) attention.


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## Curly (May 22, 2017)

So are we going to explode when the first acrylic oak blank is shown? 

Rant justified.


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## randyrls (May 22, 2017)

Eric;   May I copy and paraphrase your classifications into the IAP Wiki?  I think your comments are appropriate to reduce confusion between the different types of synthetics.

Some of your distinctions are already listed in the Wiki under (shutter, shake, and apologies in advance) acrylics.  See this link

Would a better descriptive term be thermoplastics or synthetics or something else?

  I believe these definitions would be of benefit to everyone.


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## ed4copies (May 22, 2017)

There are very few here who are qualified to write about the differences between the resins and commercial acrylics.  Sylvanite (Eric) is one of the MOST qualified.  I would encourage him to elaborate on his statements above, creating some reference material in tabular form.  EVERYONE would benefit!!

PLEASE Eric, take the time to do this--it will be a great reference for this community!!

Ed


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## 1080Wayne (May 23, 2017)

Only improvement I could make to your statement Eric is that MOST , not some , plastics are not acrylic . It has bothered me a few months longer than it has you , but I have focused more attention on wood identification . There should be enough of us with some exposure to various facets of the plastics industry that a decent reference could be compiled . My experience is all LDPE .


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## jttheclockman (May 23, 2017)

All this is very good info but we have so many new members getting into this and they do not have the knowledge to know the difference and this is where alot of this is coming from. How many times do you see on here what type wood is this posts???  It sometimes is impossible to tell from such a small sample.

I believe and there are so many new members here casting and making blanks and selling them. It is actually mind boggling. I believe the beginning needs to start with the sellers of blanks and labeling. Also if buyers buy a blank and it is not marked instead of asking us, ask the seller and do it right away so it does not get lost and mark with a sharpie or some label that does not come off. If you use a portion of the blank, make sure you mark the rest of it. Accountability starts with the sellers and then the buyers. 

A break down of the different materials will be nice but knowing what one is looking at goes far deeper than a photo here.


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## leehljp (May 23, 2017)

I have reference charts (laminated) on my wall and some in a binder for different uses - such as bits, screws, sizes in mm/inch/fractions, glues and types, etc. This will be a good chart to hang on the wall for constant reference, and with enough referencing, I will soon learn the differences.

If we could have a spread sheet type of layout that not only gives the kind of material, but the characteristics including if it finishes with a high luster or needs a CA or other finish for a high luster. This last part I could easily write in if needed. But again, it would be great to have a complete chart to learn the differences.


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## thawkins87 (May 23, 2017)

Thanks for the enlightenment! Most of the videos I have watched while learning to turn have either referenced some type of wood blank or an "acrylic" blank - I'll admit I assumed people were just using the term "acrylic" for all plastic blanks (kinda how we refer to all soft drinks as "Cokes" here in Texas!)


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## gtriever (May 23, 2017)

This is a great thread, and I hope someone does generate a chart of some type. I'd even be willing to pay for one if it was available. Coincidentally, I had first hand experience today  with 'Acrylic not being Acrylic'. I turned a circuit board blank, and everything was great. Then I turned another from a different vendor and it was an entirely different experience. Real stinky stuff, that second one...   whew!


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## Sylvanite (May 24, 2017)

I'm not a chemist, an expert on plastics, nor have I used all that many different types, but I'm willing to contribute what I have learned.  What are the various properties of the different materials that you think you'd like spelled out?  Just off the top of my head:
Trade name
Material composition
Can you make your own blank?
Ease of drilling/turning
Ease of finishing
Ease of threading/tapping
Imbedded objects?
Laser engravable?
Durability 
Any unique attributes
What else should be on the list?

What types of blanks would you like information on?
Acrylic
CA Glue
Stabilized wood (Cactus Juice etc.)
Polyester Resin (Silmar 41, Castin' Craft, etc.)
Inlace Acrylester
Rhinoplastic
Brooks blanks
TurnTex blanks
ElMostro blanks
Alumilite Clear
Alumilite White
Alumilite RC3 
WEST System epoxy
PVC pipe
Polymer clay
Toni's blanks
Ebonite
Bowling ball blanks
Bakelite
Cebloplast
Celluloid
Casein
TruStone
M3
Any others you'd like to add to the list?

Regards,
Eric


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## Curly (May 24, 2017)

Great list. Might as well add Celluloid.


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## ed4copies (May 24, 2017)

Some of those are redundant, Eric.  (ElMostro is alumilite.  Is there a need for each Alumilite?)  But it could be just copy-paste from one to the next.  The list looks GREAT!!


If you want help, I can assist in turning characteristics, etc---but I have no idea about chemical makeup.  Sincere thanks to you for even considering this project!!!

Ed


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## Sylvanite (May 24, 2017)

Yes, the member-made blanks will be made from one (or more) of the generic materials.  I anticipate that those entries would be just a reference to the plastic type and perhaps some notes.

I have no personal experience with most of these materials, so putting together a full list will have to be a group exercise.  I listed the three types of Alumilite that I have personally used (there are others as well such as "water clear") separately because they have different turning and finishing characteristics.

I haven't gone into how the different resins are to work with - I expect that would be a project unto itself.


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## 1080Wayne (May 24, 2017)

Probably should have filled plastics such as Corian and Trustone and their competitors as well . Micarta

Could also include other plastics which are available in rod or sheet format large enough to turn but not commonly used for one reason or another , such as nylon , low , high and ultra high density polyethylenes  , polypropylene . Likely are others used in the automotive and aerospace industries .


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## randyrls (May 25, 2017)

One characteristic would be if extruded or cast.

Many synthetics have a distinct "sidedness"  ie the top and bottom are colored or patterned differently than the sides.  When turned in the hands the blank "flashes".  My personal opinion is I don't like blanks that display this characteristic.


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## Sylvanite (May 25, 2017)

1080Wayne said:


> Probably should have filled plastics such as Corian and Trustone and their competitors as well . Micarta



Corian!  I can't believe I forgot Corian.

Would you believe that Corian is an acrylic?  Well, 1/3 acrylic (PMMA).  The other 2/3 is aluminum trihydrate (derived from bauxite - an aluminum ore).  So, if you've turned Corian, you've turned acrylic and aluminum.  Spooky eh?

I guess I should retract my previous statement that there is only one acrylic (PMMA).  I went a little overboard in trying to distinguish acrylic pen blanks from other materials.  There actually are several different polymers in the acrylic family, including hard plastics, rubbers, paints, and glues.  We are familiar with cyanoacrylate (CA) glue, which we commonly use as a finish, but can also be the basis for a pen blank.  In theory, one could purchase acrylic resin (clear or opaque) and cast pen blanks from it.  The resins are commercially available (widely used by dentists and in manufacturing bathtubs) but not as popular as PR or Alumilite.  I have yet to see a homemade acrylic (other than CA) blank.

Most other polymers (such as nylon, polyethylene, polypropylene, polycarbonate, polyolefin, aramids, and acetyl) are rarely used for pen blanks, so let's concentrate on the popular materials first.

Regards,
Eric


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## Woodchipper (May 25, 2017)

Man, am I confused!  I just might stick to wood (no pun intended).  Good information.  I would have never thought of engraving a certain material would give off toxic fumes.  There is a cabinet and countertop shop in town.  I get free sink cutouts for various shop projects.  I'm going to see if he has any scraps of Corian.


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## Sylvanite (May 25, 2017)

*Acrylic Acetate*

*Trade name:* Acrylic Acetate
*Material:* Acrylic (PMMA?)
To be honest I don't know exactly what "acrylic acetate" means.  I don't' find that term used in any chemistry context -- only in pen blank marketing descriptions.  I presume that "acrylic acetate" means polymethylmethacrylate (PMMA) but I could be wrong.  If anybody knows for sure,  I'd be happy to learn.​*Make at home:* In theory yes, but not in practice.
Typically these blanks are extruded in sheet or rod form, a manufacturing process requiring heavy machinery operating at high pressure with heat.   Acrylic resins, however, _are_ commercially available so somebody could cast their own blanks -- but I haven't seen anybody do it yet.​*Drilling:* Easy to drill.
*Turning:* Easy to turn with steel or carbide tools.
*Finishing:* Easy to sand and finish to a high gloss, either with plastic polish, or by buffing.
*Threading:* Can be tapped and threaded.
*Imbedding:* Yes and no.
Although items can be cast in acrylic, I've never seen an acrylic pen blank with imbedded objects.​*Laser engrave:* Yes
Cast acrylic lasers a frosty white color.  Extruded acrylic engraves with little contrast and will probably need color-fill.​*Durability:* Very good.
Acrylic is strong, hard, scratch-resistant, and resistant to many chemicals.​*Notes:*Acrylic Acetate blanks are inexpensive and readily available in a wide variety of colors and patterns.  Acrylic can be flame or chemical polished, making it a useful material for ink windows in fountain pens.​


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## bmachin (May 25, 2017)

Two more to add to the list:

1.  Alumilite Black
2.  Flexigran from Richard L. Greenwald.  Several threads on it here.  Not sure, but I think it may be a urethane.

My opinion on The various Alumilites is that the main differences in machinability is in their hardness (durometer) differences.

Bill


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## pianomanpj (May 26, 2017)

Not sure if I saw Lucite mentioned anywhere.


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## Sylvanite (May 26, 2017)

"Lucite", like "Plexiglass", is a brand name for clear acrylic (PMMA).


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## mark james (May 26, 2017)

Sylvanite said:


> *Trade name:* Acrylic Acetate
> *Material:* Acrylic (PMMA?)
> To be honest I don't know exactly what "acrylic acetate" means.  I don't' find that term used in any chemistry context -- only in pen blank marketing descriptions.  I presume that "acrylic acetate" means polymethylmethacrylate (PMMA) but I could be wrong.  If anybody knows for sure,  I'd be happy to learn.​*Make at home:* In theory yes, but not in practice.
> Typically these blanks are extruded in sheet or rod form, a manufacturing process requiring heavy machinery operating at high pressure with heat.   Acrylic resins, however, _are_ commercially available so somebody could cast their own blanks -- but I haven't seen anybody do it yet.​*Drilling:* Easy to drill.
> ...



Hi Eric (and Folks).

My wife said she will check this issue:  (She is a PhD Polymer Chemist,  specializing in Carbopol and Urethanes).


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## Sylvanite (May 26, 2017)

*Polyester Casting Resin a.k.a "PR"*

_This entry isn't for a particular blank, but rather about the material that many commercial and home-made blanks are made of._

*Trade name: *"Clear Cast", "Easy Cast", "Silmar 41", et. al.
*Material: *Polyester
There are a wide variety of resins consisting of polyester dissolved in styrene, with additives to promote curing at different rates for different ambient temperatures (called promoters), and potential other ingredients as well.  Some even include acrylic compounds to increase clarity and add UV resistance.  If you are going to make your own blank, be sure to get a resin intended for casting, not for fiberglass layup.  Polyester resins generate heat while curing, and that heat accelerates the reaction.  Fiberglass resins contain more promoters so that they will cure in thin layers.  Thick castings retain more heat and using the wrong resin could potentially cause a fire.  

The heat produced during casting affects the result in two important ways.  First, it causes the resin to expand, and then shrink when cooling.  The more heat, the more it expands, and the more it subsequently shrinks.  This makes it easier to remove from the mold, but also means that PR may pull away from materials it is cast with.  That is why PR is not usually the resin of choice for "worthless wood" casting.  The second way heat affects PR is that it speeds up the hardening process.  If the reaction proceeds too quickly, then the crystalline structure doesn't generate as many cross-links between the polyester macromolecules and you wind up with a cast that is brittle.

Polyester Resin will gel and harden by itself over time, but the casting process is typically initiated by adding the hardener methyl-ethyl-ketone-peroxide (MEKP).  The speed of the reaction and the heat produced is dependent on the promoters mixed in with the resin, the ambient temperature, and the amount of MEKP used.  Insufficient MEKP will produce a weak cast (the peroxide is needed to form the crosslinks).  Too much MEKP will yield a brittle cast (again, from insufficient crosslinks).

MEKP is a strong oxidizer and should be treated as a hazardous chemical.  It can cause burns if it gets on your skin.  The fumes are a strong irritant.  MEKP can start fires if mixed with paper or wood shavings.  Handle it with care.

Styrene (the liquid that carries the polyester) has a strong odor that most people find unpleasant.  That's what gives fiberglass it's distinctive smell.  Cast polyester continues to cure and off-gas for some time after initial hardening, so a PR pen blank might smell bad to you.

If the top surface of a polyester cast is tacky, that's ok.  It's actually an important property when doing multi-pour casts, or multi-layer fiberglass layups. The uncured surface allows the next layer to form a chemical bond.  There are ways to eliminate the tackiness, or you can just cut/turn it off.  

_Whew!  That's more than I intended to write, but I hope it will help explain the different characteristics of different brands of PR blanks._​*Make at home: *Yes
Polyester Casting Resin is very popular for home-cast blanks.  There are a wide variety of dyes, pigments, and other colorants (including mica powder) for PR, and you can imbed object in it easily.  PR is also commonly used for tube-on casting, but you may have mixed success if the shrinkage causes the resin to pull away from the tube.

Bubbles in PR casting can be reduced with vibration (ultrasonic or not), vacuum degassing, or pressure casting.  My personal preference is pressure but others have great success with different techniques.​*Drilling: *Varies.
Most PR blanks drill easily, but some can be brittle.  How brittle a blank is depends mainly on the casting conditions (see above).​*Turning: *Varies widely.
Some turn easily.  Some are so brittle that they require great technique to turn without chipping or shattering.​*Finishing: *PR generally tends to sand and polish to a high gloss fairly easily.
Plastic polish or buffing yields a glass-like shine.​*Threading: * Varies, but generally difficult.
PR _can be_ tapped and threaded, but the result is highly dependent on the brittleness of the cast.​*Imbedding: *Yes.
Small objects imbed well.  PR can pull away from worthless wood and some tube-on castings (due to shrinkage when cooling) as noted above.​*Laser engrave: * Yes.
Color fill is usually necessary to achieve good contrast.​*Durability: * Varies widely.
Polyester _can be_ a very durable material.  They make bowling balls out of it.  How durable a particular pen blank is depends on how it was cast.​*Notes: *
Many commercially sold blanks are made from Polyester Resin, and it's one of the easiest and least expensive materials to use to make your own.  The colorants and objects you can incorporate are seemingly endless so there's lots of room for your own creativity.  Be sure to cast outdoors, or with good ventilation, as PR has a strong odor.  I plan to write separately about some of the properties of certain brands of manufactured polyester pen blanks.​
I hope that helps,
Eric


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## mark james (May 26, 2017)

I also suspect that Bruce Robbins may be helpful with some of the chemistry.


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## Sylvanite (May 28, 2017)

*Colorfastness*

I think we should add "colorfastness" to the list of attributes.  That is, will a material hold its color over time, and with exposure to UV light?  We all know that wood changes color with oxidation and exposure, but what about that plastic pen?  Will it yellow with age?  Will the colors fade?  Toward that end:

*Acrylic colorfastness: *Generally excellent.
Clear acrylic (PMMA) is naturally UV resistant and generally does not yellow noticeably with age.  There's no guarantee that the colorants (dyes, pigments, etc.) will hold their color, but they usually seem to do pretty well.  I've never noticed an acrylic pen blank changing color with time or exposure.​
*Polyester Casting Resin colorfastness: *Good.
Polyester Resin _does_ yellow slightly over time, but unless you cast over something white, chances are you won't notice -- especially if you color it.  Opaque pigments and mica powder tend to hold their color better than transparent dyes.  Again, red dyes fade the most.​
I hope that helps,
Eric


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## Rockytime (May 28, 2017)

WHEW! I am exhausted. I love to turn pens for my own enjoyment and friends. I understand and recognize a need for the aforementioned subject. I'm gonna sit this one out and call it all just plastic. At some time when this is all figured out I would then be interested in the information. In the meantime I'll just relax and read my "Machinery Handbook."


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## Herb G (May 29, 2017)

Is this info going to be put into an article that will contain it all?
You know, something that can be downloaded like a library article?


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## mmayo (Jun 1, 2017)

This information is highly useful to me, THANKS.  Each time I consider a new "plastic" material I try to do research to find what to expect. This project might become something like the kit ap with dimensions.

Perhaps some hints about opacity might be useful.  I realize that the additives mixed with the resins cause the opacity, but I wish each blank had an opacity number I could use.  Maybe seller like Exotic Blanks and Bear Tooth Woods might consider more specific hints than the usual paint the inside of the blank and the tubes.


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## mark james (Aug 7, 2017)

Sylvanite said:


> *Trade name:* Acrylic Acetate
> *Material:* Acrylic (PMMA?)
> To be honest I don't know exactly what "acrylic acetate" means.  I don't' find that term used in any chemistry context -- only in pen blank marketing descriptions.  I presume that "acrylic acetate" means polymethylmethacrylate (PMMA) but I could be wrong.  If anybody knows for sure,  I'd be happy to learn.​



"Wifey" finally gave me an opinion...

"Acrylic Acetate is a very odd name that implies it's chemistry.  

The word Acrylic suggests it is mostly PMMA which will be the base material and most likely a few added acrylic esters.

The word Acetate suggests a different monomer, probably Methacrylic Acid or Acrylic Acid, this will be a proprietary mixture, and is what determines the ease of blending, extrudeability and hardness/softness or ease in turning."

After 33 years of marriage and listening to these type of explanations (I got a B- in High School Chemistry, nothing further), I believe my wife said:

YES, Acrylic Acetate is mostly PMMA, and the added "Acetate" blends are what determines the properties we as pen turners are concerned with.


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## Dalecamino (Aug 7, 2017)

mark james said:


> Sylvanite said:
> 
> 
> > *Trade name:* Acrylic Acetate
> ...


Yes! Exactly as I thought. :biggrin:


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## Herb G (Aug 7, 2017)

Dalecamino said:


> mark james said:
> 
> 
> > Sylvanite said:
> ...



Huh?


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## Herman (Oct 29, 2020)

Hello everyone. I produce acrylic rod for my own use by the casting process. I only do it because I don't find this material available in small quantities and at the quality level for pen production on the market. The process is similar to denture production, I use glass test tube to obtain solid cylinders. The material (PMMA) is marvelous for pens, ease to turn and polish. Thermal treatment is mandatory to stabilize final products. Acrylic acetate is a “blend”, sometimes produced from recycled material, not the same performance than acrylic casting.

I can say that it really is not such a simple task for a hobby to prepare at home. It is not impossible, but it is laborious and there are many variables to control. Main problem is the bubbles and contractions of the material. The monomer is highly flammable, especially when heated, be very careful. Polymerization must take place in a slow and controlled way inside an autoclave pressurized with CO2 or N2 gas (avoid fires or explosions).

Some rods produced:








And some problems that I mentioned, bubbles ... Sometimes fails occur








Just to complete explanation, this video show a simplified acrylic production process:


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## Todd in PA (Dec 30, 2022)

I just realized this is an old thread. Did someone finish and compile this work? I looked in the library…maybe I missed it.


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## Woodchipper (Dec 30, 2022)

This thread is so old it qualifies for Social Security benefits. Why don't we just say: material is natural or synthetic?


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## PreacherJon (Dec 30, 2022)

Sylvanite said:


> Please forgive my rant, but I've noticed a growing tendency for posters here to refer to all types of man-made pen blanks as "acrylic".  A number of threads started this year are all about how the different "types of acrylic" (from Inlace Acrylester to Alumilite) turn, and the techniques and tools best suited to each.
> 
> This looseness of terminology disturbs me.  While many suppliers sell blanks made of acrylic thermoplastic, most of the plastics discussed are NOT acrylic.  Inlace Acrylester is NOT acrylic.  Neither is polymer clay (PVC), RhinoPlastic (polyester), Alumilite (clear or opaque - both urethane), WEST System (epoxy), nor TrueStone (trade secret composite).  Bakelite, Ceboplast, casein, polycarbonate, and Ebonite are other non-acrylic materials.  Only poly-methyl methacrylate (PMMA - brand name "Plexiglass", "Lucite", and "Perspex)) is acrylic.
> 
> ...


Kleenex, Xerox, Jacuzzi, are just a few examples where one brand ends up being the word used for a whole industry.   It happens to be part of how American English tends to work.


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