Co-polymer for lost foam casting

Zhejiang Castchem New Material Co.,Ltd
No.10 lvyin Road,High-Tech Industry Zone,Quzhou,Zhejiang China Web: www.zj-castchem.com
Expandable Co-polymer STMMA and STMMA-FD
(The lost foam casting foam-pattern making raw material)
SPECIFICATIONS OF STMMA FOR LOST FOAM CASTING
Chemical Hazard Class 9/ UN2211
American Patent:US 6770 681 B2
Product
Volatile
level
Moisture
Beads size
Density*
Suitable for
castings with a
min thickness
of*
Additives*
Typical
Applications*
Name (by wt.)
distribution
peak
STMMA-1# ≥ 7.0% ≦0.6% 600-900 µm 18-20g/L 6~9mm Yes Aluminum,copper
alloy,grey
iron,nodular
iron,alloy steel,mild
steel and stainless
steel
STMMA-2# ≥ 7.0% ≦0.6% 450-600 µm 19-21g/L 4.5~6mm Yes
STMMA-3A# ≥ 7.0% ≦0.6% 400-550 µm 20-22g/L 4.5~6mm Yes
STMMA-3# ≥ 7.0% ≦0.6% 350-500 µm 21-23g/L 3.5~5mm Yes
STMMA-4# ≥ 7.0% ≦0.6% 250-350 µm 23-26g/L 2.5~3.5mm Yes
STMMA-FD
special
≥ 5.5% ≦0.6% 900-1250 µm 17-19g/L 9~12.5mm Yes
Aluminum
alloy,grey iron
STMMA-FD1# ≥ 5.5% ≦0.6% 600-900 µm 18-20g/L 6~9mm Yes
STMMA-FD2# ≥ 5.5% ≦0.6% 450-600 µm 19-21g/L 4.5~6mm Yes
STMMA-FD3# ≥ 5.5% ≦0.6% 350-450 µm 21-23g/L 3.5~5mm Yes
STMMA-FD4# ≥ 5.5% ≦0.6% 250-350 µm 23-26g/L 2.5~3.5mm Yes
* Density is a function of utilities and expander capabilities; the above values represent optimum expansion
conditions.
*The select of beads size shall be according to the min thickness of the casting wall, used to be 1/10 of it. For
example, you could choose the 700 µm szie beads if the casting's thinnest wall is 7mm. If the casting needs a high
precision, it can also choose the next small class.
*Contains an additive which quickly reduces the molecular weight of polystyrene at elevated temperatures.
Formula Solutions:
1.) STMMA series are focused on carbon rising defect in castings and with less residues, low dissolution
temperature
2.) The STMMA-FD series have great advantages in solving fold defect by aluminum casting and applications in iron
castings having excessive lustrous carbon, porosity defect solved.
*Typical Application means we have tested in this kind of metal, metals beyond that are according to be actually
used.

The importance:
For the lost foam casting process, the making of foamed mold is very important link.
To choose the suitable raw material for your foam-pattern mold making will decide the
quality of your castings.
Note:The above collector housing is made of STMMA by our customer in Europe.
The Advantage of using the STMMA instead of EPS
Pure EPS: 100% polystyrene, pentane<5.5%
STMMA:30%polystyrene+70%MMA,pentane>7%
STMMA-FD:90%polystyrene+10%MMA, pentane>7%
1.STMMA carbon content of 62%, while carbon in EPS is up to 93%. STMMA will greatly
reduce the carburization defects during casting.
2.STMMA has a low pouring temperature, gasification temp generally has 50℃ lower than
EPS( STMMA between 1400℃ to 1450℃, EPS between 1460℃ to 1500℃). This will help the
foundry to save energy consumption in $50 to $100 per ton of castings.
3.The molecular bonds are broken orderly when STMMA gasifying, accompany with liquid low
molecular residues. EPS molecules are disorderly broken, accompany with tar similar
residues.
4.The high molecular weight of STMMA will reduce the pattern's dimensional shrinkage rate.
Compare with the 220 thousands of molecular weight, EPS has only 50 to 60 thousands of
molecular weight.

The carbon content of EPS,STMMA,STMMA-FD:
92.60% Carbon cotent%
100 82%
90
80 63%
70
60
50
40
30
20
10
EPS STMMA-FD STMMA

The residues content after degradation of the foam pattern:
Item
Weight of
pattern
Weight of
residues
Percent of
Residues
Density of
panttern
EPS 3.37g 2.22g 65.90% 21g/L
STMMA-FD 3.37g 1.03g 30.60% 19g/L
STMMA 3.37g 0.15g 4.45% 20g/L
General Comparison:
EPS STMMA-FD STMMA
Composition (C8H8)n -(C8H8O2)-m
Carbon content 92% 82% 63%
Temperature of foaming 80~85 ℃ 85~95 ℃ 95~105 ℃
Temperature of decomposition 912℃ 900℃ ——
Gas evolution of 900℃ 600ml/g 700ml/g ——
Casting temperature(for gray iron) 1500~1460℃ 1480~1450℃ 1450~1400℃
Residuum after foamed mold
decomposing
65% 30% 4.5%
Shrinking percentage of foamed
molds
0.3~0.8% 0.2~0.4% 0.1~0.3%
Rate of finished casting products(for
boxes and motor housings)
80~92% ≥93% ≥98%
The molding process of STMMA:
Prefoaming
Select beads
Select type of beads based on material and quality requirement
of the casting,select the size of the beads based on the
minimum wall thickness of casting.
▼
Control density of pre-foamed
beads
In order to give mold enough strength and rigidity,the resin
beads to cast thin-wall pieces shall be controlled at density
between 24~26g/L.Thick-wall pieces shall be made with large
beads, with density between 19~22g/L
▼
Expansion of beads
Pre-heat temperature between 90~95℃,expansion temperature
between 95~105℃,expansion time between 30~60s

For inquiry: info@zj-castchem.com
WhatsApp:+86 15068719527
Web-site:www.china-castchem.com
Web-site2: www.zj-castchem.com
▼
Aging Aging of beads
The aging time depends on enviornment
temperature,humidity,moisture content and density of resin
beads.Aging is an important step for achieving a quality mould
▼
Pattern-marking
Preheating of moulds
The purpose of preheating of mold is to shorted the forming time
and reduce condensed water in cavities during molding
▼
Filling of moulds Filling with suction method,press method or both.
▼
Heating(foam shaping)
The pressure shall be controlled between 0.2-0.3Mpa for
heating steam.Pressure to be controlled between 0.11-0.15Mpa
for autoclave forming,0.10-0.12Mpa for the air chamber of the
mould
▼
Cooling
Cooling to form mould and give its strength and
rigidity.Notes:cooling uniform and enough
▼
Removing of moulds Shall preventing pattern surface from damage and deformation
▼
Drying and stabilizing moulds
Could be natural drying or drying in ventilated room with
temperature controlled at 40-60℃,it must prevent the pattern
from deformation.After drying,the moisture should be less than
1.0%

Co-polymer for lost foam casting

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Co-polymer for lost foam casting