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Thermo expandable microcapsulesKUREHA Microsphere

KUREHA Microsphere　S series

  • S series, can be foamed above 190℃ and are suitable for foam molding of engineered plastics and elastomers.
  • When molding by blending with pellets, we recommend masterbatch with excellent dispersibility.
  • As a guideline for additive amount of masterbatch, we recommend 2 to 3% for weight reduction and 2% or less for sink mark prevention.
Series Grade Average particle size before expansion
（μm）		 Average particle size after expansion
（μm）		 Expansion ratio Expansion start temperature (Tstart)
（℃）		 Maximum expansion temperature (Tmax)
（℃）
S S2340 15-25 70-140 100-170 170-190 230-245
S2640 15-25 70-140 100-170 190-215 250-265

Masterbatch grades

Masterbatch Grade Microsphere Grade Base Polymer Content
(wt%)		 Average particle size
(μm)		 Expansion Start Temperature (Tstart)
（℃）		 Maximum Expansion Temperature (Tmax)
（℃）
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

Movie : Foam molding used KUREHA Microsphere

Extrusion foam molding

  • S2340 : It's suitable for applications with molding temperatures from 190 to 230℃. Suitable for expansion of engineered plastics such as PP and ABS.
  • S2640 : The highest temperature sphere suitable for process temperatures that range from 230℃ to 260℃ or when avoiding expansion in step-1 of a 2-step molding process.

Extrusion foam molding : Example of process conditions

Masterbatch Grade Matrix Resin C1 C2 C3 C4 Die
(℃)		 Resin temperature
(℃)
MB-S3LC ABS 130 180 230 230 190 210-220
MB-S6LC TPV 130 150 250 230 190 220-230

*C1-C4：Cylinder temperature (℃)

Injection foam molding

  • Short shot method used in injection molding.
  • Method in which small amount of melt is injected with respect to volume of cavity (Fig. A), and the space is filled by foaming (Fig. B).
  • Specific gravity of the product depends on the amount of injected resin.
  • KUREHA Microsphere expands when pressure drops (after passing through the nozzle).
  • Recommend attachment of shut-off nozzle to prevent from resin dripping.

Injection foam molding : Temperature condition example

Masterbatch Grade Matrix resin C1 C2 C3 C4 Mold temperature
(℃)
MB-S3LC PP 160 210-230 50-80
MB-S6LC PA12 200-210 230-250 30-50

*C1-C4：Cylinder temperature (℃)

Physical Property

Masterbatch Grade - MB-S3LC MB-S6LC
Matrix resin - PP 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 1182 1058 850 885 700 665

Sectional images of PA12 foams (MB-S6LC : 6 wt%)

  • Size : 128 mm x 12.8 mm x 12.8 mm
  • Expansion ratio : 1.3 times
  • Particle size (Closed cell) : 50 ~ 80 μm

Improved moldability

  • The use of KUREHA Microsphere improves moldability (prevention of sink marks).
  • 2% or less of masterbatched microspheres can improve molding performance.

Photo: Molded piece

  • without KUREHA Microsphere

  • with KUREHA Microsphere

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