Testing Resin Systems

A test rig setup is being used to compare and evaluate different resin mixes.
The test rig is kept as simple as possible, within the parameters of a DLP projector design.

Some of the specifications to be implemented are:

1. Simulate the resin vat of the "bottom-up" build method
2. Keep at least 3mm of resin depth in the simulated vat to replicate protection from surface oxygen scavenging
3. Achieve a realistic Lumen figure shining at the sample
4. Have a light spectrum in accordance to the DLP UHP bulb
5. Avoid heat transfer as much as possible

Using a mini-vat

Use a chronometer to time the experiments.

Flushing and releasing the slab

After illumination, flush any uncured resin with water. A slab of cured resin remains, neatly taking the form of the rectangle drawn with the black marker on the back side of the slide.

I use an exacto knife to remove the slab from the microscope slide. It is pretty easy to lift as it doesn't stick much. Resins cured with H-Nu470 are more gel like than those cured with BAPO and would need a stronger light source to achieve similar results or a second hardening stage in the sun or UV oven.

Take measures

Use a calliper or thickness gauge and measure the slab's thickness at several spots.

I use 4 measures and average the results, calculate the standard deviation and divide it by the average. These figures give me an idea of the quality of the experiment and the cure speed of the resin system.

Experiments

Comparison of Sartomer Monomers / Oligomers

To see properties of the different Sartomer Monomers / Oligomers mentioned below, click here

50w covered GU10 at 26ºC 1ml volume
Exposure Time [sec]	60
Monomer / Oligomer		Cured layer thickness measures				AVG	STDEV / AVG	Time [sec]/0.1mm	Comments
Polyester Acrylate Oligomer(16)	P16	0.690	0.640	0.620	0.690	0.660	0.054	9.091	Tough
Polyester Acrylate Oligomer(4)	P4	0.430	0.460	0.530	0.500	0.480	0.092	12.500	Tough
Ethoxylated(3) Bisphenol-A Diacrylate	ED3	0.590	0.520	0.620	0.610	0.585	0.077	10.256	0
Ethoxylated(4) Bisphenol-A Diacrylate	ED4	0.690	0.620	0.520	0.630	0.615	0.115	9.756	0
Ethoxylated(10) Bisphenol-A Diacrylate	ED10	1.430	1.410	1.220	1.320	1.345	0.071	4.461	0
Ethoxylated(6) Bisphenol-A Triacrylate	ET6	1.960	1.770	1.720	2.030	1.870	0.079	3.209	Tough, Hard
Dipropylene Glycol Diacrylate	2PGD	0.570	0.480	0.500	0.520	0.518	0.075	11.594	Slow cure, Tough, Hard
Epoxidized(2) Soybean Oil Acrylate	X2SBA	0.000	0.000	0.000	0.000	0.000	NA	NA	No cure

Comparison of BAPO vs H-Nu470 Photoinitiators

50W covered GU10, 80mm from sample, at 26ºC
60s exposure, 2mm resin height in vat
System	M 1	M 2	M 3	M 4	Avg	STDEV/Avg	mm/min	Time[s] / 0.1mm
R I / H-Nu470	0.6	0.55	0.5	0.55	0.550	0.074	0.550	10.909
R I / BAPO	0.85	0.8	0.85	0.75	0.813	0.059	0.813	7.385
R II / H-Nu470	0.65	0.6	0.65	0.55	0.613	0.078	0.613	9.796
R II / BAPO	0.9	0.95	0.9	0.75	0.875	0.099	0.875	6.857

Effect of resin height on cure speed due to Oxygen inhibition

Testing resin height in vat, 60s exposure
50W covered GU10, 80mm from sample, at 26ºC
System	M 1	M 2	M 3	M 4	Avg	STDEV/Avg	mm/min	Time[s] / 0.1mm
R II / BAPO 1mm	0.4	0.35	0.4	0.4	0.388	0.065	3.871	15.484
R II / BAPO 2mm	0.85	0.8	0.8	0.8	0.813	0.031	1.846	7.385
R II / BAPO 3mm	1	1	0.95	1	0.988	0.025	1.519	6.076

Effect of Titanium Oxide filler on the penetrance of light and cure thickness

Testing TiO2 filler effect at 15wt% on cure thickness, 3mm, 60s exposure
50W covered GU10, 80mm from sample, at 28ºC
System	M 1	M 2	M 3	M 4	Avg	STDEV/Avg	mm/10 sec	Time[s] / 0.1mm
R I / BAPO	0.72	0.71	0.77	0.75	0.738	0.037	0.123	8.136
R I + TiO2 / BAPO	0.07	0.06	0.06	0.08	0.068	0.142	0.011	88.889