Expandable Polymer Microspheres
Kureha Microspheres
Closed-cell Lightweighting of Thermomplastics and Elastomers
What are Expandable Microspheres?
Microspheres are a closed cell foaming agent. They are also referred to as thermo expandable microcapsules. A hydrocarbon-blowing agent resides inside an acrylic shell. When exposed to heat the shell softens while the pressure inside increases, allowing for rapid expansion.
Expansion starts gradually at the Tstart (activation) and reaches its peak expansion diameter at the Tmax (Maximum expansion temperature).
Once cooled, the microsphere maintains its shape encapsulating the blowing agent.
KUREHA has a lineup of microsphere grades suitable for a wide range of thermoplastics; including advanced grades that are compatible with higher temperature polymers.
Applications include automotive composites, glass run channel, weather strip, shoe soles, thermal release tape, and ultra-lightweight filament for 3D printers.
50-170X Increase of Volume Depending on Grade
Precision Light weighting and More
Kureha microspheres are precision additives that are used to lower density, reduce cost, and provide acoustic and thermal insulation. When heated, microspheres expand to a target diameter and maintain that diameter after cooling.Kureha microsphere benefits include weight reduction, improved molding properties, and thermal and sound insulation. Microspheres are a precision foaming agent characterized by easy control of specific gravity, uniform closed cells, small sphere diameter, and uniform distribution. Microspheres provide the flexibility to foam in resin and other highly permeable materials such as fibers and paints.
Kureha H-Grade Microspheres
H series are suitable for expansion at 160C~190C. Within this temperature range, resins such as PVC, rubber and elastomers can be expanded.
MS Grade | Pre-Expansion Avg (μm) | Post-Expansion Avg (μm) | Ts Thermal Start | Tm Thermal Max |
---|---|---|---|---|
H750 | 15~25 | 60~100 | 120~160 | 160~170 |
H850 | 30~45 | 155~225 | 120~135 | 170~185 |
H880 | 20~35 | 85~135 | 135~160 | 175~185 |
H1100-S | 40~55 | 145~210 | 145~160* | 175~195 |
Temperatures in (℃)
*The Ts for H1100-S can be adjusted, please contact Kureha for additional details
Kureha Series-S
Series-S microspheres can be foamed above 190℃ and are suitable for engineered plastics and elastomers.
MS Grade | Pre-Expansion Avg (μm) | Post-Expansion Avg (μm) | Ts Thermal Start (℃) | Tm Thermal Max (℃) |
---|---|---|---|---|
S2340 | 15~25 | 70~140 | 170~190 | 230~245 |
S2640 | 15~25 | 70~140 | 190~215 | 250~265 |
Series-S Comparison
Kureha Series-S MB
Kureha Series-S Masterbatch (MB) is a 50/50 blend of Series-S microspheres with LDPE. When molding by blending with pellets, we recommend masterbatch for its excellent dispersibility. As a guideline for additive amount of masterbatch, we recommend 2%-3% for weight reduction and up to 2% to reduce sink marks.
Masterbatch Grade | Microsphere Grade | Base Polymer | (wt%) | Average Particle (μm) | Ts Thermal Start (℃) | Tm Thermal Max (℃) |
---|---|---|---|---|---|---|
MB-S3LC | S2340 | LDPE* | 50 | 15~25 | 170~190 | 230~245 |
MB-S6LC | S2640 | LDPE* | 50 | 15~25 | 190~215 | 250~265 |
*LDPE : Low density polyethylene
Extruding Series-S MB
Sample process
MB Grade | Resin | C1 | C2-C4 | Die | Mold Temp |
---|---|---|---|---|---|
MB-S3LC | ABS | 130 | 180~230 | 190 | 210~230 |
MB-S6LC | TPV | 130 | 150~250 | 190 | 220~230 |
MB-S3LC Ideal temperatures from 190℃ to 230℃ suitable for PP and ABS and other similar materials
MB-S6LC Ideal temperatures from 230℃ to 260℃ suitable for TPV and other similar materials
Sample Process Density
Injection Series-S MB
For injection molding the material we recommend attaching a shut-off nozzle to prevent from resin drip.
Sample Process
MB Grade | Resin | C1 | C2-C4 | Mold Temp |
---|---|---|---|---|
MB-S3LC | PP | 160 | 210~230 | 50~80 |
MB-S6LC | PA12 | 200~210 | 230~250 | 30~50 |
Temperatures in (℃)
Sample Process Material Properties
Metric | PP | PP | PP | PA12 | PA12 | PA12 | |
---|---|---|---|---|---|---|---|
Dosage | WT% | 0 | 1 | 3 | 0 | 3 | 6 |
Density | g/cm3 | 0.88 | 0.73 | 0.67 | 0.99 | 0.85 | 0.78 |
Expansion Ratio | - | 1.0 | 1.2 | 1.3 | 1.0 | 1.2 | 1.3 |
Light Weight Ratio | % | 0 | 17 | 23 | 0 | 14 | 21 |
Flexural Strength (ASTM D790) | MPa | 35 | 27 | 22 | 34 | 27 | 25 |
Flexural Modulus (ASTM D790) | MPa | 1,182 | 1,058 | 850 | 885 | 700 | 665 |
Precision Flexibility
The flexibility of expandable polymer microspheres makes it an excellent tool to reduce density/weight. Because of this they are often used in conjunction or to replace CBA’s (Chemical Blowing Agents) or CFA’s (Chemical Foaming Agents). That includes AZOD (Azodicarbonamide), OBSH (Oxydibenzenesulfonyl Hydrazide), and Sodium Bicarbonate among others. These agents are either endothermic or exothermic and decompose in the base material. Generally, speaking grades differ by gas pressure and the amount of gas liberated per gram.The issue with both chemical and foaming agents comes down to control. Controlling color, density, durometer, and surface finish can be challenging when you’re trying to aggressively reduce density. Additional complications that come with working with these chemical agents include molding times and mold corrosion; and in the case of organic foaming agents, the odor from outgassing.
Samples and Support
North and South America Only
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