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 GradePre-Expansion Avg (μm)Post-Expansion Avg (μm)Ts Thermal StartTm Thermal Max
H75015~2560~100120~160160~170
H85030~45155~225120~135170~185
H88020~3585~135135~160175~185
H1100-S40~55145~210145~160*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 GradePre-Expansion Avg (μm)Post-Expansion Avg (μm)Ts Thermal Start (℃)Tm Thermal Max (℃)
S234015~2570~140170~190230~245
S264015~2570~140190~215250~265

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 GradeMicrosphere GradeBase Polymer(wt%)Average Particle (μm)Ts Thermal Start (℃)Tm Thermal Max (℃)
MB-S3LCS2340LDPE*5015~25170~190230~245
MB-S6LCS2640LDPE*5015~25190~215250~265

*LDPE : Low density polyethylene


Extruding Series-S MB

Sample process

MB GradeResinC1C2-C4DieMold Temp
MB-S3LCABS130180~230190210~230
MB-S6LCTPV130150~250190220~230

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 GradeResinC1C2-C4Mold Temp
MB-S3LCPP160210~23050~80
MB-S6LCPA12200~210230~25030~50

Temperatures in (℃)

Sample Process Material Properties

MetricPPPPPPPA12PA12PA12
DosageWT%013036
Densityg/cm30.880.730.670.990.850.78
Expansion Ratio-1.01.21.31.01.21.3
Light Weight Ratio%0172301421
Flexural Strength (ASTM D790)MPa352722342725
Flexural Modulus (ASTM D790)MPa1,1821,058850885700665

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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