Solutions

HomeSolutionsFancryl 500 Series

UV-Curable with Low Cure Shrinkage Resins for 3D-Printing

Monomers

Fancryl 500 series monomers

Expected applications

3D printing

End products

Automotive | Dental | Other consumer and industrial goods

Key benefits

Low shrinkage | No solvents | Low viscosity | High efficiency milling | Excellent dispersion

Showa Denko Materials is one of only four companies in the entire world who creates DCPD (dicyclopentadienyl) monomers. DCPD monomers have numbers of unique features derived from DCPD structure.

Resins in 3D-Printing

Additive manufacturing is widely known as 3D printing, which builds components layer by layer. It provides design flexibility, effective product development as well as on-demand manufacturing. In contrast to a subtractive production process involving milling or cutting of parts to create the correct form, 3D printing is an additive manufacturing technique.


The 3D printing sector has been growing progressively and new advances have been made. New 3D printers are now being designed to print products using materials like plastics, metals, composites etc. The raw materials used in 3D printing are as complex as the actual products. Thus, 3D printing is modular enough for formulators to specify a product's form, texture and strength.


Resin is one of 3D printing's most common materials. It is used mostly in innovations as with Stereolithography (SLA), Digital Light Processing (DLP), Multijet, and Continuous Liquid Interface Production (CLIP). The resins are suitable for numerous applications. They have low shrinkage, are highly resistant to chemical conditions, and are hard as well as delicate.


For additive manufacturing or 3D printing, the formulation of Ultraviolet (UV) curable resins covers various industries ranging from optical fibres, inks, and adhesives through to nanotechnological and biomaterial technologies.


UV curing systems include reactive oligomers and reactive monomers, photo-initiators, as well as other additives. Epoxy, polyester, polyether and urethane are the primary forms of UV oligomers. Acrylates and methacrylates are widely used as a reactive monomer for free radical photopolymerisation.


A photopolymerisation reaction is triggered when a photo-initiator embedded inside a UV curing system is introduced to Ultraviolet light; the monomers and oligomers, key ingredients of the polymer resin, spontaneously create a 3D network polymer.

The Challenge

There are a broad variety of materials to pick from when it comes to professional 3D printing. These technologies have distinct properties, benefits and drawbacks. Some of the challenges faced by 3D manufacturers are presented.

Cure Shrinkage

Precision is required in 3D printing products, as is the case with the other products. For instance, some of the components of the automobile industry have moved from injection to the 3D printing production process, meaning that the demands of dimensional accuracy are growing.


When reactive substances like acrylic monomer and oligomer are formulated with, cure shrinkage will more or less take place. The decrease in acrylates and methacrylate volume occurs during polymerisation, which is because the weak Van der Waals force is replaced by strong short covalent bonds among the carbon atoms of various monomer units.


The shrinkage during Ultraviolet curing is caused by overlapping spaces occupied by monomer units, — in other words, the sum of the monomer units free volumes is greater than the free volume of a polymer derived from such monomer units. The space variation enables shrinking, posing numerous difficulties during the curing process.


This volume reduction creates significant issues, including a substantial rise in internal stress, culminating in the development of faults and dimensional variations that contribute to reduced mechanical characteristics. There have lately been reports of non-uniform objects created by the ultraviolet additive manufacturing process.

Oxygen Inhibition

Oxygen inhibition is also a major challenge in (meth) acrylate free radical polymerisation. Air inhibits the polymerization rate since the oxygen molecules scavenge the free radical required to initialize cross-linking. During UV curing, oxygen diffusion from a highly concentrated region to a pre-polymer resin demands an extra quantity of photo-initiator and UV energy to use up the dissolved and diffused oxygen.


Thermal Resistance

Heat resistance of thermoplastics is another challenge in 3D printing. The heat resistance of polymeric materials is the ability to keep their valuable characteristics at high temperatures.


Thermal resistance establishes an upper limit for the temperature range during which a thermoplastic substance can withstand mechanical loads without changing its form. The temperature of glass transition is defined as the temperature at which 30 to 50 carbon chains begin to migrate. At the glass transition temperature, the amorphous regions move from rigid to more fluid states, which transform the temperature to a rubbery state at the boundary of the solid-state.


The thermal stability determines the upper thermal limit where a polymer's suitability is decided by chemical resistance, i.e., reaction resistance that typically contributes to polymers being degraded in an inert or oxidizing medium.

The Solution

These problems expect to be overcome by the use of dicyclopentadiene (DCPD) monomers. Showa Denko Materials is one of the four firms that produce DCPD (dicyclopentadiene) monomers worldwide. These monomers have certain special properties found in the chemical structure itself.


Polydicyclopentadiene (DCPD), a Diels-Alder addition reaction product between two cyclopentadiene molecules forming two stereo-isomers: an Endo-DCPD and the Exo-DCPD, is a strongly reactive thermoplastic resin.


DCPD co-polymerizes efficiently with a significant number of vinyl monomers and resins such as unsaturated esters, epoxies, alkyds and phenols. It acts as a diluting, cross-linking and curing agent.


The processing of unsaturated polyester resins in substantial amounts is one of the most significant uses of polydicyclopentadiene (DCPD). Unsaturated polyesters are usually prepolymers that have low molecular weight.


The Fancryl 500 Series is a single-function (meth) acrylate with voluminous DCPD structure. Our DCPD monomers are our particularly unique hydrophobic, well-reducible and highly adhesive materials.

Low Cure Shrinkage

We believe that Fancryl 500 Series monomers will help to minimize cure shrinkage owing to its voluminous DCPD structure and eventually improve the moulding stability of 3D printing products, even with the same acrylic materials.

Less Sensitivity to Oxygen

In contrast with other monofunctional aliphatic monomers, Fancryl 500 series is not impaired by oxygen inhibition. These products lower the scrap rate induced by inadequate cure and enhance 3D printing products' yield rate. As seen below, in comparison to many other monofunctional cycloaliphatic monomers, the Fancryl 500 series is less sensitive to oxygen.

Monomer

UV irradiance level until tack-free (mJ/cm2)

In the absence of O2
(under N2)
In the presence of O2
(under air)

FA-511AS

120

120

FA-512AS

180

240

FA-513AS

120

180

Isobornyl-A

240

>600

Cyclohexyl-A

240

>900

[Test methods]
Test bar: PET film
UV lamp: High-pressure Hg Vapor lamp 80 W/cm2
Irradiation distance: 18 cm
Conveyor speed: 20 m/min
Composition: monomer 97 wt%, photoinitiator 3 wt%


Transesterification Method

Transesterification is a generic term used to define the essential group of chemical reactions in which an ester is converted into another via an alkoxy moiety exchange. When reacting with alcohol, the process of transesterification is called alcoholysis.

Transesterification (Showa Denko process)


The transesterification process used demonstrates very good stability as sulfur and other impurities are not present when compared to dehydration esterification. The transesterification products have minimal ionic impurities, outstanding chemical stability and lower skin irritancy.

Dehydration Esterification


As shown below, the colour and acid-value stability of Fancryl 500 DCPD series acrylates are seen over six months using our transesterification process. In comparison to our process of trans-esterification, dehydration esterification demonstrates the volatility of colour and acid over the six months.


Moreover, the sulphur content of Acrylates from the Fancryl 500 Series is less than 1 ppm, which makes the concentration of sulphur negligible.


Stability Test and PII

High Glass Transition Temperature, Tg

The DCPD polymethacrylates exhibit high glass transition temperatures, Tg. FA-513 M polymerizes, for instance, to create a 3D network polymer with a glass transition temperature of 175 °C and carbon number 10. Similarly, the FA-512MT polymers have a glass transition temperature of 45 °C and carbon number 12. The DCPD polymethacrylates thus preserve their beneficial properties at elevated temperatures.


When a fully polymerised system has a glass transition temperature, Tg substantially greater than the polymerisation temperature, Tcure then the reaction normally comes to an end before reaching completion.

Heat resistance of polymethacrylates

Outstanding UV Curing Characteristics

In contrast with other aliphatic monomers, DCPD (meth)acrylates show excellent UV curing characteristics. The comparison data is shown below. DCPD acrylics have fast curing rates, strong adhesive properties and high water resistance, as seen below.

UV Curing Characters of DCPD (meth)acrylates