Material Profile: BJD (Ball-Jointed Doll) Resin for SLA / LCD 3D
Phrozen SLA / LCD Resin Technical Report Series
Compiled from Phrozen official datasheets, SDS documents, and third-party technical reviews
Abstract—Phrozen BJD Resin (Ivory) is a 405 nm UV-curable photopolymer formulated for ball-jointed-doll fabrication and articulated figurines. It balances high detail reproduction with sufficient toughness to survive repeated joint actuation; the warm ivory base color is engineered to approximate skin tones and to accept hobby-grade primers and paints.
Index Terms—additive manufacturing, SLA, LCD, photopolymer, ball-jointed doll, BJD, high resolution.
I. MATERIAL IDENTIFICATION
This section establishes the canonical names and commercial designations under which the resin is supplied.
A. Designation
Trade name: Phrozen BJD Resin (8K Series). Color: Ivory.
B. Resin Family
Acrylate / urethane-acrylate photopolymer system based on multi-functional (meth)acrylate monomers and oligomers, photoinitiated by acylphosphine oxides at 405 nm. The cured network is approximately isotropic and amorphous.
C. Aliases and Alternative Designations
|
Alias |
Origin / Usage |
|
Phrozen BJD |
Standard product designation |
|
BJD Resin Ivory |
Sole color variant |
|
8K Series BJD |
Phrozen series classification |
II. COMPOSITION AND PHOTOPOLYMER CHEMISTRY
A. General Resin Family
Generic photo-polymerisation: monomers (multi-functional acrylates / urethane-acrylates) + photoinitiator (e.g., TPO / BAPO) + 405 nm UV → crosslinked thermoset network. Exact formulation is proprietary.
Fig. 1. Photopolymer crosslinking schematic for the resin family.
Fig. 2. SLA / LCD print → wash → post-cure process flow.
B. Composition Breakdown
TABLE I COMPOSITIONAL BREAKDOWN OF BJD RESIN (TYPICAL / PER SUPPLIER DATASHEET)
|
Constituent |
Mass fraction |
Function |
|
Multi-functional acrylate / urethane-acrylate monomers |
≈ 70–85 wt% |
Form the backbone of the cured network |
|
Reactive diluents (low-viscosity acrylates) |
≈ 10–20 wt% |
Reduce viscosity; increase crosslink density |
|
Photoinitiator (acylphosphine oxide, e.g., TPO) |
≈ 1–3 wt% |
Absorbs 405 nm UV, initiates radical polymerisation |
|
Pigments, stabilisers, additives |
≈ 1–3 wt% |
Color, UV blocker for shelf life, surface flow |
|
Total |
100 wt% |
— |
III. MECHANICAL PROPERTIES
BJD resin is engineered to be slightly tougher than baseline 8K detail resins so joint sockets withstand repeated assembly without micro-cracking. Properties below reflect typical ranges for fully post-cured specimens.
TABLE II MECHANICAL PROPERTIES OF BJD RESIN (POST-CURE, ISO 527 / ASTM D638)
|
Property |
Value |
Test method / source |
|
Density |
≈ 1.13 g/cm³ |
ASTM D792 |
|
Viscosity (uncured liquid) |
≈ 280–350 cP @ 25 °C |
Brookfield viscometer |
|
Surface hardness |
≈ Shore D 82–86 |
ASTM D2240 |
|
Tensile strength, ultimate (UTS) |
≈ 45–55 MPa |
ASTM D638 / ISO 527 |
|
Tensile (Young's) modulus |
≈ 1800–2200 MPa |
ASTM D638 |
|
Elongation at break |
≈ 8–15 % |
ASTM D638 |
|
Flexural strength |
≈ 55–70 MPa |
ASTM D790 |
|
Izod impact, notched (23 °C) |
≈ 22–28 J/m |
ASTM D256 |
IV. RECOMMENDED PRINT PARAMETERS
Values below are the manufacturer-recommended starting points for compatible Phrozen LCD printers; specific machines may require ±10–20% adjustment based on LCD age and ambient temperature.
TABLE III RECOMMENDED PRINT AND POST-PROCESS PARAMETERS FOR BJD RESIN
|
Parameter |
Value / range |
Notes |
|
UV wavelength |
405 nm |
Standard for Phrozen LCD printers |
|
Compatible printers |
Sonic Mini 8K / 8K S, Sonic Mighty 8K / 12K, Sonic Mega 8K |
Best paired with the indicated resolution class |
|
Layer thickness |
0.025–0.050 mm (typical 0.030 mm) |
Thinner layers improve detail at the cost of print time |
|
Normal exposure (per layer) |
≈ 2.0–3.0 s @ 8K resolution |
Test-tower validation recommended |
|
Bottom exposure |
≈ 25–35 s × 6 layers |
First-layer adhesion to build plate |
|
Lift distance / speed |
≈ 6–8 mm @ 60–100 mm/min |
Slower for fine geometries |
|
Wash medium |
Isopropyl alcohol (IPA) or 95% ethanol |
30–60 s wash; do not over-soak |
|
Post-cure |
405 nm UV box, 30–120 min depending on size |
Phrozen Cure Mega S or equivalent |
V. GLASS TRANSITION TEMPERATURE (TG)
Reported / typical Tg: ≈ 65–80 °C.
Tg depends strongly on post-cure intensity / duration. Insufficient post-curing reduces Tg by 10–20 °C and impairs mechanical properties.
VI. HEAT DEFLECTION TEMPERATURE (HDT)
HDT defines the temperature at which a 1.27 mm-thick standardied bar deflects 0.25 mm under the specified flexural load. Two test loads are reported per ASTM D648 / ISO 75.
TABLE IV HEAT DEFLECTION TEMPERATURE OF BJD RESIN
|
Test load |
HDT |
Test method / source |
|
0.45 MPa |
≈ 68–76 °C |
ASTM D648 |
|
1.82 MPa |
≈ 60–68 °C (estimate) |
ASTM D648; engineering estimate |
VII. DISTINGUISHING CHARACTERISTICS AND STANDARDS
A. Engineered for articulated joint applications
Unlike pure 8K detail resins (which prioritise sharp edges at the cost of brittleness), BJD resin is balanced for cyclic stress imposed by ball-and-socket joints. Fully post-cured parts withstand repeated joint articulation in BJD figurines without cracking.
B. Ivory skin-tone base color
The Ivory tint approximates a natural skin base, reducing the painting effort required for face-up work. Most hobby acrylic primers (Mr. Hobby, Vallejo, Tamiya) adhere well after light sanding.
C. 8K-resolution detail capability
Reproduces sub-50 µm features such as eyelashes, facial sculpting lines, and clothing folds without the smoothing typically observed in tougher hobby resins.
D. Standard 405 nm photopolymer chemistry
Compatible with all 405 nm LCD / DLP printers within the Phrozen ecosystem and most third-party 405 nm machines after exposure-time calibration.
VIII. REPRESENTATIVE APPLICATIONS
BJD Resin is typically deployed in the following applications:
1) Ball-jointed doll (BJD) figurines: Full-character articulated dolls with up to 30+ joints; head, torso, limbs printed separately and assembled.
2) Articulated action figures: Custom action figures, anime / manga character figurines with movable limbs.
3) High-detail collectible busts and statues: Bust-only sculptures where extreme face / hair detail matters more than mechanical loading.
4) Customised face-up replacements: Replacement BJD heads with custom sculpting / tattoos for collectors.
5) Educational and ergonomic mannequins: Articulated reference models for figure-drawing, pose study, prosthetic fitting.
IX. REFERENCES
[1] Phrozen Technology, “BJD Resin Product Page,” 2024. Available: https://phrozen3d.com/products/bjd-resin
[2] Phrozen Technology, “BJD Resin Safety Data Sheet (Ivory),” 2024. Available: https://cdn.shopify.com/s/files/1/0436/6965/1618/files/SDS-Phrozen-8K_Series_Resin_BJD_Resin_Ivory.pdf
[3] ASTM D638-14, “Standard Test Method for Tensile Properties of Plastics,” ASTM International.
[4] ASTM D2240-15, “Standard Test Method for Rubber Property — Durometer Hardness,” ASTM International.
[5] ASTM D648-18, “Standard Test Method for Deflection Temperature of Plastics Under Flexural Load,” ASTM International.
[6] ISO 527-2:2012, “Plastics — Determination of tensile properties — Part 2,” ISO.
(Image Source : Phrozen)