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Top 10 Injection Molding Materials (And Why They are the Best)

August 12, 2021 by Ashish Mittal 3 Comments

top 10 injection molding materials

Quick Navigation

  • Which are the Best Injection Molding Materials? 
  • 10 Best Injection Molding Materials – 
  • #1 Polypropylene (PP):
  • #3 Acrylic:
  • #4 Acrylonitrile Butadiene Styrene (ABS):
  • #5 High-Density Polyethylene (HDPE):
  • #6 Polyoxymethylene (POM):
  • #7 Polycarbonate (PC):
  • #8 Polyethylene(PE):
  • #9 Thermoplastic Rubber (TPR):
  • #10 Polystyrene (PS):
  • Final Thoughts – 

Which are the Best Injection Molding Materials? 

Injection Molding materials selection is one of the most crucial parts for rapid and quality production. That becomes even more significant because injection molding processing needs supremely suitable materials to perform better.  Having said that, selecting the best plastic material for the process is not rocket science.

With some research selecting the best injection molding material can become relatively easy.

But, a question might pop up in your mind. There are thousands of plastic materials out there, which one to choose?

Today, I will be sharing a list of 10 thermoplastics that can improve your injection molding productivity by many notches.

10 Best Injection Molding Materials – 

  • Polypropylene (PP)
  • Nylon 
  • Acrylic
  • Acrylonitrile Butadiene Styrene (ABS)
  • High-Density Polyethylene (HDPE)
  • Polyoxymethylene (POM)
  • Polycarbonate (PC)
  • Polyethylene (PE)
  • Thermoplastic Rubber (TPR)
  • Polystyrene (PS)

#1 Polypropylene (PP):

polypropylene

Polypropylene is an “addition polymer” produced using polymerization and with the combination of propylene monomers.

High chemical and moisture resistance, flexibility, toughness, and excellent electrical insulation make polypropylene highly suitable for injection molding.

The common applications can be found in the food packaging industry. Washing and cleaning are also easy without degradation and damage chemicals. Mixing with foods is not a scenario with packaging made of PP. That’s why it is safe for human contact, and moisture resistance keeps the inside warm and fresh for a prolonged period of time.

Below is the table sharing the typical properties of polypropylene:

Property Value
Impact Strength
2 – 6 kJ/m2 at 20 °C
Density
1.04 – 1.06 g/cm3
Melting Point 160-168°C
Elastic Modulus 1.5 – 3 GPa
Thermal Conductivity
0.41 W/(m.K) at 20 °C
Flammability UL 94 HB
Electrical Resistance
1*1013 – 1*1014 Ω.m at 20 °C
Dielectric constant 2.8 at 20 °C
Specific heat capacity
1520 J/(kg.K) at 20 °C
Max. service temperature (short) 140°C
Coefficient of thermal expansion
6*10-5 – 1*10-4 1/K at 20 °C

 Detailed Guide on Polypropylene 

#2 Nylon:

Nylon

Nylon, also known as Polyamide, is a synthetic thermoplastic switch, a special structure where components are bound in some bond.

Nylon is made by filtration of hydrocarbon fuels into lighter groups of small molecules called “Fractions.”

Good chemical and thermal resistance, high melting temperature, high toughness, and brittleness make it one of the injection molding materials suitable for applications like mechanical parts, gears, bushing, bearings utilized mostly in automobile and electrical industries.

The only drawback one might face is the expansiveness of nylon. There’s a table below with general properties of typical variations of Nylon or polyamide

Property Units ASTM Test Extruded NYLON 6/6 Cast NYLON 6
Oil-Filled Cast NYLON 6
Flexural modulus psi D790 410,000 420,000 – 500,000
375,000 – 475,000
Tensile Strength psi D638 12,400 10,000 – 13,500 9,500 – 11,000
Heat deflection temperature – 264 psi °F D648 194 200 – 400 200 – 400
Water absorption (immersion 24 hours) % D570 1.2 0.60 – 1.20 0.50 – 0.60
Maximum continuous service temperature in air °F – 210 230 230
Coefficient of linear thermal expansion in/in/°Fx10-5 D696 4.5 5 5
Izod Impact ft-lbs/in of notch D256 1.2 0.7 – 0.9 1.4 – 1.8

 Detailed Guide on Nylon

#3 Acrylic:

Acrylic

Acrylic is a naturally transparent thermoplastic homopolymer better known by the trade name “Plexiglass.” Apart from being transparent, it also has scratch and impact resistance with high tensile strength.

It is often utilized as a suitable alternative for glass and even its alternative Polycarbonate for manufacturing windows, doors, transparent walls, display products lenses, fashion accessories, and even lighting equipment for the construction industry.

However, I would suggest using polycarbonate over acrylic for highly demanding applications.

Property Value
Technical name Acrylic(PMMA)
Melt Temperature 130°C (266°F)
Chemical Formula
(C5H8O2)n
Tensile Strength
65 MPa (9400 PSI) ***
Shrink Rate
0.2 – 1% (.002 – .01 in/in) ***
Flexural Strength
90 MPa (13000 PSI) ***
Specific Gravity 1.18
Typical Injection Mold Temperature
79-107°C (175-225°F) ***
Water absorption (immersion 24 hours)
0.20%
Light Transmittance
92%
Heat deflection temprature
95°C (203°F) at 0.46 MPa (66 PSI) **

#4 Acrylonitrile Butadiene Styrene (ABS):

ABS plastic

Acrylonitrile Butadiene Styrene is an opaque thermoplastic and amorphous polymer produced mainly by emulsion and mass polymerization methods; however, Emulsion is mostly preferred.

Key properties include toughness, scratch resistance, impact resistance, and good dimensional stability.

ABS is widely used in the electronics industry for manufacturing computer keyboards, power toll-housings, phone adapters, wall socket plastic guards, and even lego toys. It is one of the few injection molding materials with the strength and agility required to be utilized in electronics.

Detailed Guide on ABS Plastic

#5 High-Density Polyethylene (HDPE):

High-Density Polyethylene

High-Density Polyethylene is durable and lightweight thermoplastic with variable structures. It is made by radical polymerization of ethylene monomers with Ziegler-Natta and Metallocene acting as catalysts.

HDPE has low-temperature resistance, high tensile strength, good chemical resistance, and excellent electrical insulating properties.

It is mostly used for food packaging applications like bottles of milk and juices, crates, trays, etc., and textile applications like ropes, decorative fabrics, fishing nets, etc.

Detailed Guide on HDPE

#6 Polyoxymethylene (POM):

Polyoxymethylene is a formaldehyde-based, semi-crystalline engineering thermoplastic material containing the functional group of a carbon bonded to two -OR groups.

With excellent wear resistance, high crystallinity, and fantastic dimensional stability, good resistance to organic solvents makes POM one of the prime injection molding materials.

POM’s high-end properties make it suitable for applications in industries like automobiles, healthcare, and consumer goods.

Main products made from POM include ball bearings, knives, fasteners, pipe couplings, showerheads, automobile cushioning interior, etc.

Polyoxymethylene is inferior to hydrochloric acid and nitric acid.

Interesting Read – Injection Molding in Medical Industry | The Pros of Medical Device Injection Molding | The Importance of Plastic Injection Molding

#7 Polycarbonate (PC):

polycarbonate

Polycarbonate is one of the most suitable injection molding materials used in industries like automobile, construction, consumer goods, electronics, and healthcare.

Polycarbonate is available in multiple grades and variations depending on the purpose.

Major properties include high impact strength, good abrasion resistance, excellent chemical resistance, great steam resistance (not affected by water or temperature), withstanding prolonged steam sterilization, etc.

Major products producing PC are coffee machines, food mixers, light housings, headlamp bezels, security windows, shelters, safety goggles, lenses, food storage containers, food processors, etc.

Detailed Guide on Polycarbonate 

#8 Polyethylene(PE):

polyethylene

Polyethylene is one of the most produced plastic materisl in the world, with a variety of applications in multiple industries. Like PC, polycarbonate also boasts a variable crystalline structure.

There are three major variations within polyethylene. They are:

  • Branched variation
  • Linear variations
  • Cross-linked polyethylene

Some of the major properties are phenomenal resistance to most solvents( except hydrocarbons), great electrical insulating properties, inexpensiveness, and decent water resistance.

Products made from PE include oil and liquid food containers, housewares, ice-boxes, toys, jerry cans, drums, pharmaceutical packaging, squeeze bottles, caps, pipes, garbage containers, etc.

 Detailed guide on Polyethylene 

#9 Thermoplastic Rubber (TPR):

Thermoplastic Rubber

Thermoplastic Rubber, or TPR, is sometimes called Thermoplastic elastomer (TPE), is a blend of rubber and plastic suitable for injection molding. It shows both rubber and plastic properties, which means it melts when heated and solidifies when cooled.

Like many other injection molding materials on the list, TPR is recyclable, which increases its applicability and helps manufacturers control their carbon footprint. Its boasts fantastic chemical and weather resistance coupled with high-impact strength.

Major products made from thermoplastic rubber are cable jacketing, footwear, automobile components, toys, soft handles and grips, window and door weather stripping, coated fabrics, household appliances, etc.

Detailed Guide on Thermoplastic Rubber

#10 Polystyrene (PS):

polystyrene

Polystyrene is a naturally transparent thermoplastic material that is available in both solid plastic and foam material forms. Amongst the foam form, there are two major variations 1) Expanded Polystyrene (EPS) and extruded polystyrene (XPS).

Talking about solid plastics, major variations are 1) General Purpose Polystyrene (GPPS) 2) High Impact Polystyrene (HIPS).

Major polystyrene properties are high chemical and heat resistance, high UV stability, and high dimensional stability. The most common applications are  CD and DVD cases, food trays and containers, egg cartons, toys, automobile parts, gardening tools, equipment, etc.

Property Value
Tensile Strength
53 MPa (7700 PSI)
Melt Temperature
210-249 °C (410-480 °F)
Heat Deflection Temperature (HDT)
95 °C (284 °F) at 0.46 MPa (66 PSI)
Specific Gravity
1.04
Flexural Strength
83 MPa (12000 PSI)
Typical Injection Molding Temperature
38 – 66 °C (100 – 150 °F)
Molecular Weight of Repeat unit
104.15 g mol-1
Molar Cohesive Energy
J mol-1 34200 – 37100
Density
g mL-1 1.05 – 1.06
Entanglement Molecular Weight
g mol-1 13600 – 17500
Solubility Parameter
18.5 – 19.4 MPa

Detailed Guide on Polystyrene 

FAQs – 

1. What are the types of injection molding variations?

Ans. There are many variations associated with injection molding. Here are the most popular variations:

  1. Die-casting
  2. Metal injection molding
  3. Micro-injection molding
  4. Cube molding
  5. Reaction injection molding
  6. Thin-walled injection molding
  7. Gas-assisted injection molding
  8. Liquid silicon rubber injection molding

2. Which is the strongest Injection molding plastic?

Ans. Polycarbonate is the strongest plastic material in the world. It is said to be 200 times stronger than glass.

3. How do I choose an injection molding machine?

Ans. There are four factors needed to be considered before the injection molding machine selection process. Here are they:

  1. Know the plastic parts to intend to mold
  2. Select machine type: Hydraulic, electric, or hybrid
  3. Calculate clamp weight requirements
  4. Calculate injection mold size

4. What are the stages of injection Moulding?

Ans. There are four stages in the injection molding cycle – Clamping, injection, cooling, ejection

5. Why does it take so much time to design and manufacture an injection mold?

Ans. It takes somewhere around a few weeks to a couple of months to design an injection mold. There are many factors contributing to the amount of time required. It can be anything from supplier inventory backlogs, available resources, the complexity of the molded part, the complexity of the desired mold, and even the number of cavities.

Fantastic Read – Top 10 Injection Molding Defects (And How To Prevent Them)

Final Thoughts – 

Thus were my views on the top 10 injection molding materials. I have kept the piece brief and simple to understand. You can click on the detailed guide links to know more about the material.

In addition, always consult with your manufacturer regarding the properties and attributes of the polymer supposed to be used for manufacturing. Even the tiniest detail missed can have a significant effect on the production time and the quality of the produced part.

Kindly share your reviews in the comment box.

Filed Under: Injection molding

Ashish Mittal

About Ashish Mittal

The plastic industry mainly uses injection molding, blow molding, extrusion, and compression molding techniques of which Ashish holds tremendous knowledge

Comments

  1. AvatarOlivia Smart says

    May 24, 2022 at 10:22 pm

    Thank you for going over some different materials for injection molding.

    Reply
    • AvatarSagar Habib says

      May 26, 2022 at 2:15 pm

      My Pleasure

      Reply
  2. AvatarGabor Matos says

    July 1, 2022 at 1:48 am

    Wonderful site. I am trying to find a 3D printable material which is heat resistant in the 200-300C’ range , that I can use as a mold in injection or dip molding. Do you know of any such material?
    Thank you
    Gabor

    Reply

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