Printing materials

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Printing Materials

In this section we will discuss a number of materials that can be used with RepRap and the ways to use them, as well as the core information needed for their successful application. Many of these materials will fall under the Polymer class (loosely called plastics). In time we will also discuss clays, plasters, cements, gels, and any other materials we think can be of use.

Polymers

Thermoplastic

Main page: Category:Thermoplastic

The term thermoplastics applies to polymers that reversibly change phase with temperature. While keeping within a boundary of temperatures, these phase changes can be done safely and the material returns to it's original solid state after cooling, without any alteration in it's original properties.

See also WorkingWithThermoplastic.

Thermoplastics Data Sheets and where to get them

These are the various suppliers we've found. YMMV.

Polymorph (Polycaprolactone)

A useful plastic with a very low melting point that is hand-workable. You can use it to fashion your own parts without a machine, Its a tad bit expensive, but very handy. Check out the link above for suppliers.

HDPE (High Density PolyEthylene)

This is very common engineering plastic. It is used in a wide variety of consumer goods. It's strong, durable, and has a decent melting point. It's also very cheap. Unfortunately it has, compared to FDM-friendlier plastics, a very high shrinkage factor when solidifying, so there isn't much of a chance of it ending up being the main working material of choice for RepRap.

ABS (Acrylonitrile Butadiene Styrene)

ABS is a general purpose, strong, and very resistant type of plastic. It is a bit more expensive than HDPE, but it also is a bit higher quality material than HDPE.

PLA (Polylactic Acid)

Polylactic acid is a cheap, biodegradable polymer, that is produced from lactic acid, which can be obtained from the maceration of starch and sugars in biotanks.

PP (Polypropylene)

Abbeon Cal $10 / lb

Informations about plastics

http://www.ides.com/info/generics (from http://forums.reprap.org/read.php?1,70471)


Paste

Main: Paste
Category:Paste Extruders

In physics, a paste is a substance that behaves as a solid until a sufficiently large load or stress is applied, at which point it flows like a fluid.

A paste extruder, such as as Syringe Based Extruder, could be adapted to Paste Extrusion a large number of materials, including Chocolate Extrusion, Frostruder, clay Ceramic Extrusion, etc.

Duroplastics

Duroplastic polymers are plastics that once hardened cannot reversibly change phase (molten) through heat. Solvents may dilute some of them (Acrylics, Polyesters in their lower molecular weight form) and by evaporation of the solvent they will harden again. This application, very common in solvent based varnishes and paints, is nevertheless not practical for RepRap, as the volatile solvents take a long time to evaporate and in large section or layer thickness, this evaporation cannot be regulated and controlled so as to produce uniform deposition layers (bubbles, hardening imperfections).

Is "duroplastic polymer" a synonym for "thermosetting polymer" ?

The most common way to obtain Duroplastics is by polymerizing their monomer and oligomer blends, also called Resins, through chain reactions, whether initiated by catalysts and radicals that spring from reaction with moisture, pH, oxygen, radiation or heat (thermosetting) or auto-initiation with another identical monomer or a suitable copolymer. Polymerization can be initiated by a simple change in pH, by adding an acidic or basic reactant (Furan resins, phenol-formaldehide (Resol), urea-formaldehide...)

For rapid prototype deposition, Duroplastic resins have to fulfill a number of conditions:

1) They have to have a long work time, meaning that they have to remain fluid, preferably without any changes in viscosity and state for the whole time frame of the deposition session. Failing to do so would mean that the depositing tool would get clogged as well as introducing deposition artifacts and distortions due to variations in flow rates.

2) They have to have the correct viscosity and plasticity, so that after deposition they don't sag too much or change shape noticeably. Additionally, at no moment during the hardening process should the volume of the polymer change severely.

3) After deposition they have to have suitable adhesive properties so that threads glue together with the best possible bond strength.

4) Once deposited, there has to exist a mechanism by which the polymer will set and harden, if possible, on command. The curing has to occur through the whole section of the deposited material, not just on the surface of the thread or layer. This point will be discussed under the section Catalysts and Initiators

These conditions are less restrictive if you want to use these polymers as casting resins to fill molds (built by the deposition technique).


Spontaneous polymerization resin blends

This section will describe resins that need to be stored in two separated components for them to remain fluid for long periods of time. The most common blends of this class, generally called Dual Component Resins have to be mixed in a given proportion just before usage and start the polymerization chain reaction as soon as the two parts are homogeneously mixed. Spontaneously polymerizing monomers will not be addressed in their pure state, due to their uncontrollable and often dangerous polymerization properties. Additives and fillers can tame these processes so as to make them useful in some cases.

Read more on spontaneous polymerization resin blends

Triggered polymerization resin blends

In this section we will discuss resin blends that can be mixed in their final composition and still be kept unchanged for long periods of time. They will only start polymerizing after having been given the right trigger effect (see Catalysts and Initiators)

Read more on triggered polymerization resin blends

Other Additives, Monomers, Fillers

Here you will find a number of filler materials: Go to Fillers section

A good website to find all types of monomers and oligomers with their descriptions and properties can be found at this very complete site:

Oligomers at Sartomer.com

Monomers at Sartomer.com

or at

BASF Resins

For Organic products I have found some sites that provide chemical products all over the globe. Go to their web and search for the systematic name or name parts of the product. If you cave a CAS number (unique number for a given product) these sites will deliver a very accurate search result list. All of these sites require you to register to get prices and place orders:

Chemexper web, will give you a list of companies that sell the searched compound

ACROS Organics


Catalysts and Initiators

There are several chemical types of catalysts that are of use to RepRap. All of them, independently of their chemical type, fall into two categories of importance to RepRap and those will be discussed below:

Catalysts for dual-component mixes

Spontaneously catalyzed systems start the polymerization reaction as soon as the catalyst comes in contact with the monomer. They do not need any further external input to fulfill their initiator role, be it heat, moisture, radiation (UV, visible, IR...).

Catalysts for single-component mixes

Triggered catalysts need a triggering effect to start their initiator role. This is an obvious advantage as they can be blended in the monomer mix and be kept on the shelve for significant amounts of time (weeks, months...). They will not clog any tubings, pumps or dispensers. Also, they offer one more level of control, being able to decide when and where to apply the trigger effect and sometimes also when to stop the chain reaction. These triggered initiators are usually more complex as the first category, specially if what you are looking for is a rapid reaction producing fast setting times through thick sections of material. One example of these systems are the acrylic based tooth fillings the dentists use, that are triggered by UV light. Many varnishes are also UV triggered but they have a much longer setting time and require hour-long exposures to achieve definitive hardening.


Glossary of Terms and Definitions

Here you will find a short and basic explanation of terms used in all the sections above. If some term used above seems unclear to you, please post a message in the forum and I will see to add the term to this glossary.

Go to Glossary