PEI Injection Molding
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PEI has excellent thermal stability, good flame retardant and chemical resistance, and good electrical insulation and should be used in injection molding of high-temperature-resistant product parts.
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What is PEI Plastic?
PEI (Polyetherimide), commercially known as Ultem®, is a high-performance amorphous thermoplastic renowned for its exceptional combination of thermal, mechanical, and electrical properties.
It belongs to the family of engineering plastics and is widely used in demanding applications across industries such as aerospace, medical, automotive, and electronics.
Description
Full Name
Polyetherimide
Process
Finishing options
Mold texturing，Electroplating, Bead Blasting
Applications
Medical instrument，Electrical insulation parts
Prices
$$$
Features
Appearance
Amber/Transparent
Strengths
Excellent Chemical resistance and ductility, Heat Stabilized
Tensile Strength
12000 PSI
Elongation at Break
0.5 – 0.7 %
Density
1.27 g/㎤
Material Properties of Common PEI Grades
Ultem 1000
Ultem 2200 (20% GF)
Ultem 2300 (30% GF)
RTP 2100 LF
Density (g/cm3)
1.27
1.42
1.51
1.27
Physical
Shrinkage Rate (%)
0.5–0.7
0.3–0.5
0.2–0.4
0.8
Rockwell Hardness (M)
106
114
114
Tensile Stress (MPa)
110 @ Yield
131 @ Break
175 @ Break
105 @ Yield
Mechanical
Elongation @ Break (%)
50
4
2.4
60
Flexural Modulus (GPa)
3.3
6.89
9.6
3.31
Flexural Stress (MPa)
160 @ Yield
227 @ Break
240 @ Break
145
Electrical
Dielectric Strength (in Oil) kV/mm
25 (1.6 mm)
26.3 (1.6 mm)
26 (1.6 mm)
19.7 (S/T)
Volume Resistivity (Ω. cm)
1.E+15
7.E+16
1E+15
1.E+12
Drying Temperature (°C)
150
150
150
149
Injection Molding
Drying Time (hrs)
4–6
4–6
4–6
4
Melt Temperature (°C)
350–410
350–400
350–410
354–399
Mold Temperature (°C)
135–180
135–165
135–180
135–177
Advantages of PEI Injection Molding
PEI (Polyetherimide) injection molding offers several advantages:
High Temperature Resistance
PEI has excellent high temperature resistance, operating continuously up to 170°C and withstanding shortterm exposure to much higher temps.
Recyclability
Polyetherimide is a thermoplastic, it can be repeatedly reshaped, and its recyclability is of growing environmental and economic significance.
Transparency and Aesthetics
PEI can be transparent or translucent, which is beneficial for applications such as optical devices and light diffusion components.
Electrical Insulation
It has good electrical insulation properties. The dielectric constant of PEI is relatively stable, typically around 3.15 at 1 kHz.
Dimensional Stability
PEI shows low shrinkage in injection molding and excellent dimensional stability across various temperatures and humidity.
Applications of PEI Injection Molding
PEI (Polyetherimide) injection molding has a wide range of applications due to its excellent properties:
PEI Injection Molding Material Properties
PEI Plastic Properties
Value
Tensile Strength （MPa）
1.00 - 650
Flexural Modulus（GPa）
5.17 - 10.3
Impact Resistance (Izod Impact, Notched)
0.0298 - 19.2 J/cm (0.0558 - 36.0 ft-lb/in)
Maximum Service Temperature（℃）
70.0 - 300
Chemical Formula
(C2H5N)n
Glass Transition Temperature（℃）
217
Heat Deflection Temperature（℃）
200
Drying Temperature（℃）
150
Drying Time（hr）
4-6
Mold Temperature（℃）
65～175
Melt Temperature（℃）
350～425
Injection Pressure（MPa）
70～150
Injection Speed（ mm/sec）
50-100
Cooling Time（S）
15～20
Scrap Quantity（mm）
2～8
Back Pressure（MPa）
0.300 ～ 0.700
Clamping Force（ton/in2）
2～2.5
Return Speed (rpm)
70～100
Shrinkage
0.5 - 0.7%
PEI Injection Molding Design Guide
Wall Thickness
Uniformity: Maintain consistent wall thickness (recommended 1.5–3.0mm) to prevent warping and sink marks.
Maximum Limit: Avoid exceeding 6mm to minimize residual stress and cycle time.
Thin-Wall Design: Achievable down to 0.5mm with high-pressure molding (140+ MPa).
Draft Angles
Minimum Draft: 1–2° per side for smooth surfaces.
Textured Surfaces: Increase draft to 3–5° to prevent sticking.
Radii and Fillets
Internal Corners: Use radii ≥ 0.5× wall thickness to reduce stress concentrations.
External Edges: Sharp corners acceptable if functional, but radii improve flow.
Ribs and Bosses
Rib Thickness: ≤ 60% of adjacent wall thickness to avoid sink.
Bosses: Design with 0.5–1.0mm clearance around mating parts to account for thermal expansion.
Gate Design
Gate Types: Prefer hot tip gates or submarine gates for minimal shear.
Gate Size: Diameter ≥ 75% of part thickness to prevent jetting.
FAQs
Q: How to choose PEI and PEEK?
A: PEI (40% cost reduction) is preferred in conditions below 180°C, and PEEK is recommended for ultra-high temperature environments.
Q: Can PEI plastics achieve metal insert molding?
A: Yes, preheat inserts to 200-220°C and control CTE differences <2×10^-5/°C
Q: PEI injection molding minimum molding wall thickness?
A: Conventional structure 0.5mm, special design up to 0.3mm (need to verify mold flow)
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