Choosing the Right Material for Plastic Injection Molding



So many material options for plastic injecting molding, which one to choose?

This can be a crucial task and it impacts directly on the quality, durability, and functionality of your end product. While choosing the material we should keep in mind that each plastic material has unique properties that have major effects on performance during the process of manufacturing and at the final product.

Here we are going to explore the advantages and properties of various materials and how different plastics bring diverse advantages to the manufacturing process.

Factors to Consider in Material Selection for Injection Molding

To choose the right material for the plastic injection molding process we need to consider the following factors.

· Impact on part design and functionality: The right choice of material has a great impact on part design and its functionality. Every material has its own strength, flexibility, and robustness.

· Temperature resistance, chemical compatibility, and dimensional stability: Keep in mind that features such as temperature resistance, chemical compatibility, and dimensional stability are important while you are selecting material. Some materials can have more resistance against high temperatures and harsh chemicals while dimensional stability is the ability of the material to ensure the maintenance of shape and design of the part during the molding process.

· Balancing cost, performance, and processing requirements: Another factor to check is the balance in material cost, products, and performance. You don’t want to spend a lot of money on little production only as high-performance materials can be very expensive.

Cost and Durability Considerations

Cost evaluation is necessary when spending money on anything same is for the selection of materials, it is important to consider long-term cost-effectiveness before buying material for injection molding. Cost evaluation includes many factors such as initial material costs, maintenance requirements, replacement costs, and environmental impact.

Another important thing to consider is product durability and its lifespan. Only a durable material can ensure a longer lifespan of the product as it can withstand wear and tear for a long time. The benefit of these to consideration is customer satisfaction and reduce number of replacements of product

The list below is some factors that you need to consider while doing a cost evaluation of the product material.

· Maintenance: Maintenance is necessary but some materials require a proper maintenance program or special treatments to work properly. Before buying such material, consider the time and cost which will be required for maintenance. Is it worth it?

· Replacement Costs: Material for plastic injection molding can be sensitive and prone to damage in a small-time span, you may need to replace products with such material regularly. That’s why considering replacement costs always is wise.

· Environmental Impact:  Globally we are moving towards a sustainable and green environment, so it is necessary to make sure that material you are using fulfills the terms and conditions of this factor. Moreover, materials with eco-friendly nature can not only benefit your company but also reduce costs in the long term.

To understand the concept in a better way, let’s go through with some examples. Suppose you have some samples of various materials and now you need to choose, what will be your consideration here?

1. Material A is cheaper than Material B but Material B has superior durability, which will reduce long-term cost because of fewer replacements.

2. Now let’s check Material C and Material D. Type C has lower maintenance costs but has higher upfront costs on the other hand Type D is cheap but requires expensive and regular maintenance sessions. requires minimal maintenance but has a higher upfront cost than Material D. This makes D type more expensive than Material C.

3. Material E fulfills all the requirements of being a sustainable item and is environmentally friendly. It can be recyclable and produce very less waste. It is also a little costly compared to other materials but has a longer time span and is environmentally friendly.

Now you know which factors to consider while buying the right material which is affordable, durable, and according to the requirements of the plastic injection molding company to produce a product that is efficient in working long life and durability.

Amorphous vs Semi-crystalline Thermoplastics

Amorphous and semi-crystalline thermoplastics are two types of thermoplastics that have different structures and properties. Their pros and cons are different so they can work properly under different conditions for various applications. Factors like mechanical strength, transparency, and processability effects on their degree of crystallinity.

Structure and Properties

Amorphous thermoplastics

· They do not have a defined crystal structure and have a disordered molecular arrangement.

· They featured transparent or translucent properties because of their random molecular arrangement.

Semicrystalline thermoplastics

· They have amorphous regions and well-defined crystalline structures. Their molecular are arranged properly.

· Their properties include opacity, and translucence as light passes from their crystalline regions.


Amorphous Thermoplastics:

1. They are used in the application where you require translucence, such as:

· Display screens

· Optical lenses

· Packaging materials

2. As they have high impact resistance, they are proffered to be used in the following industries:

· Automotive parts

· Consumer electronics housings

· Safety equipment

Semicrystalline Thermoplastics:

1. They are used in the application where high mechanical work is needed such as:

· Structural components

· Gears and bearings

· Medical implants

2. They are mostly used at areas where chemical resistance is required such as:

· Pipes and fittings for corrosive environments

· Chemical storage containers

Crystallinity Effects

1. Mechanical Strength:

· The more the crystallinity the more stiffness and strength.

2. Transparency:

· The higher the crystallinity the less transparency will be reduced.

3. Processability:

a) More crystalline materials may require higher processing temperatures for effective molding.

b) Amorphous materials usually have better flow characteristics during injection molding.

Now you have achieved another understanding which is necessary for choosing the right material for the molding process as properties of the material highly depend on structures and amorphous and properties of  semicrystalline thermoplastics

Strength, Machinability, and Polishing Capabilities

Strength, Machinability, and polish capabilities are the factors that have a high impact on the right selection of material for plastic injection molding. If these factors meet your requirements, only then the final product can last for the long term.  

Let’s explain these factors:

· Assess strength requirements:

The material should be able to bare load-bearing capacity, have high resistance, and is durable.

· Evaluate machinability:

For a better process of injection molding, materials should have the ability to be easily cut or drilled into.

· Consider polishing capabilities:

The material consists of a surface that can be finished through polishing or texturing processes is the best for molding.

Filler and Additive Selection for Injection Molding

Choosing the right materials includes the selection of filler and additives for injection molding.  The selection of fillers and additives determines the quality and performance of the molded part in the final product.  

Exploring Different Fillers

There are many different types of filler, here we are going to discuss the most commonly used fillers in the injection molding sector.

· Glass fibers: They are used in the process when the end product requires high strength, stiffness, and durability.

· Carbon fibers: These carbon fibers have the same purpose as glass fiber but they weigh less than glass fibers.  

· Mineral fillers: if your product requires enhance dimensional stability and reduce shrinkage then it is your best option.  

Exploring Various additives

Not only fillers but additives also play an important role in choosing the right material for plastic injection molding. These additive elements can be added to plastics during the process of injection molding to acquire the required properties and characteristics in the end product.

List down some of the few types of additives which the molding industry commonly used:

· Colorants and dyes: To give a vibrant and appealing effect to the final product, you can add dyes and pigments of various colors.

· Flame retardants: Another additive that is important with respect to safety purposes is flame retardants which provide resistance to plastic against fire, and ensure safety of the user.

· UV stabilizers: UV lights from sunlight can be harmful to many products in general especially plastic as it causes the degradation of products with plastics.  UV stabilizers when added to the material while the process of molding then it give resistance against the UV lights to the product and automatically increase the life span of the product.


In conclusion, the selection of the right material for plastic injection molding is the first step toward the success of your project. This requires careful evaluation of many factors such as cost-effectiveness, durability, thermoplastic characteristics, strength attributes, machinability options, polishing capabilities, and appropriate fillers/additives. If you do have not much experience in such a field then you should follow industry advisors and guidelines, other than this you can seek consultation from professionals to ensure the optimal outcome of your final product. Anyhow, the information provided in this article and other related articles on our website is enough to let you help in making the decision of getting the right material for the injection molding project.


How to check, which material is cost-effective for me?

The cost-effectiveness of the material can be determined by evaluating the following factors: initial cost, maintenance cost, replacement cost, production efficiency, environmentally friendly features, and longer time span of the product for which the material is used.  

Is all type of thermoplastic material for injection molding the same?

No, every thermoplastic material is different from others due to its properties and structures.  Factors such as melt flow index, shrinkage rate, and thermal stability need to be considered for proper working and are different in various materials.  

How does the strength of the material in injection molding affect the process?

The material’s strength is an avital factor to consider while choosing the material as it determines the durability and structural integrity of the end product. First, be sure what are your application requirements and then select the material with matching tensile strength, impact resistance, or flexural modulus. This will help in increasing the efficacy of the product.

What is the usage of fillers and additives play in injection molding?

Fillers and additives are used to improve the properties of the plastic material, such as improving strength, reducing shrinkage, increasing flame retardancy, or adding color, which are not already present. This is the reason that the fillers and additives used in the process should be according to material, specific requirements, and compatibility with material.

I don’t know much about choosing the right material, where can I get some guidance and more information about selecting materials for injection molding?

If you want to know more about selecting the right material for injection molding projects then you can prefer talking to the industry’s experts or seeking help form experienced professionals. You can also go through different research publications.

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