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Mechanical Properties of Plastic Materials | The Definitive Guide

June 19, 2021 by Ashish Mittal 1 Comment

mechanical properties of plastics

Quick Navigation

  • What are the Mechanical Propertoes of Plastic Materials?
  • The Purpose Mechanical Properties in Plastics- 
  • Impact Strength:
  • Compressive Strength:
  • Hardness:
  • Tensile and Flexural Strength:
  • Flexural Modulus of Elasticity:
  • FAQs – 
  • Final Thoughts – 

What are the Mechanical Propertoes of Plastic Materials?

Hello people, Today, we’ll be looking at the mechanical properties of all mainstream plastic materials. Below is the easiest bifurcation of all mechanical properties possessed by plastics.

Materials Tensile Strength Tensile Elongation Compression Strength Tensile Modulus of Elasticity Flexural Strength Flexural Modulus of Elasticity Hardness Izod Impact
ASTM TEST psi D638, 73°F % D638, 73°F psi D695, 73°F psi D638, 73°F psi D790, 73°F psi D790, 73°F Scales – D785, D2240, 73°F
ft-lbs/in D256, 73°F
ABS 4100 32 – 294,000 9100 304,000 R102 7.7
Acetal 10000 75 – 450,000 14300 420,000 M89, R121, Shore D 83 1.5
Acrylic 10000 4.5 17,000 400,000 17,000 480,000 M95 0.4
CAB – cellulose acetate butyrate 5,221 33.9 – 400,000 – 230,000 – 4.4
CE – Canvas Phenolic 9,000 – 34,000 – 15,000 1,500,000 M100 1.5
Polyamide 12,400 90 – 470,000 17,000 410,000 M85, R121, Shore D 80 1.2
ECTFE – Ethylene Chlorotrifluoroethylene 8,000 300 – 250,000 – 145,000 Shore D 73 No breaking
HDPE 4,000 600 30,000 – – 200,000 Shore D 69 –
PBT 8,690 300 – 416,000 12,000 330,000 M72 1.5
PEEK 14,000 60 – 400,000 24,600 590,000 M105, R126, Shore D 85 1.6
PET 11,500 70 – 400,000 15,000 M93, R125, Shore D 87 0.7
PETG 7,700 210 – 320,000 11,200 310,000 R115 1.7
Polycarbonate 9,500 135 12,500 345,000 135,000 345,000 M70, R118, Shore D 80 12.0 – 16.0
Polypropylene 5,400 – – – – 225,000 Shore D 75 1.2
PTFE 2,500 150 – – – 72,000 Shore D 55 3.5
PVC 7,500 – – 411,000 12,800 481,000 R115, Shore D 89 1
PVDF 7,800 35 – 350,000 10,750 310,000 M75, R84, Shore D 77 3
TPE 1,740 31 – – – – – –
UNMW 3,100 350 – – – 110,000 Shore D 64 *

All the values and technical information mentioned above are for information purposes only. All the value shave been figured out after extensive research, but still consulting with your material supplier is advised for accurate figures.

Definition – The meaning of mechanical property is the physical attributes shown by a material upon application of forces.

The Purpose Mechanical Properties in Plastics- 

The Purpose Mechanical Properties in Plastics

Mechanical Properties are a crucial part of a product’s integrity. Factors like tensile strength, tensile elongation, compression strength, flexural strength, hardness, and elasticity can make or break things for a product’s quality and applications.

Let’s look at the purpose and importance of some of the above attributes.

Impact Strength:

The impact strength in thermoplastics is measured by either Charpy or Izod impact tests. The string method is simple but effective. A rectangular rod is placed in a pendulum at high speed and the energy absorbed while breaking the sample is measured.

The higher the number, the greater the impact resistance. In certain cases, plastics with high resistance values do not break, resulting in no usability. The test will be repeated serval times with a north made on the sample to obtain details under a more dreadful condition.

The plastics with high impact strength are:

  • ABS
  • Polycarbonate 
  • EVA
  • CAB
  • ETFE
  • ECTFE

Compressive Strength:

Compression strength is measured by applying a constantly increasing force on cubical or cylindrical samples placed between two plates, thereby measuring elongation and pressure.

One important thing to note is that the compression property at break is not always accurate because ductile materials sample tends to deform without clear breakage. Unrestrained deformation under load isn’t a reliable indication for success under real-life industrial applications.

Following those reasons, compressive street si not determined at the break but determined at defined deformation point (Usually 1,2, or 10%).  Another smart move would be to check the test conditions before comparing compression values from different sources.

A reliable method to improve or enhance the compression strength of any thermoplastic polymer is to add carbon fiber or glass fiber reinforcements. However, apparent effects on the load performance are noticeable in the long term rather than short-term (That means patience is the key) due to enhancements in creep properties.

The thermoplastics with impressive compressive strength are:

  • ABS
  • Acrylic 
  • Acetal 
  • Polycarbonate 
  • HDPE 
  • Polyethylene  

Engaging Read – Physical Properties of Plastic Materials | The Complete Guide

Hardness:

While there are several methods to measure hardness in a thermoplastic, the most common method used is known as “ball indentation hardness.” A sphere-shaped metallic ball of standard dimensions is pressed into material with a certain force; for a certain amount of time, the residual mark will define the hardness value.

There is another method named “Rockwell Hardness testing,” which is also popular for determining hardness.

Carbon fiber and glass fiber-filled materials show the highest surface hardness.

The materials exhibiting excellent hardness are:

  • Polypropylene 
  • Polycarbonate 
  • HDPE

Tensile and Flexural Strength:

Flexural strength for any thermoplastics is yielded thorough flexure test. In that test, a sample with rectangular or circular is bent until a fracture occurs. The flexural strength represents the highest stress experienced by material in its moment of yield.

Talking about tensile strength, it is the maximum stress a plastic material can resist while being stretched before breaking. Tensile strength is more important in brittle materials than ductile materials.

Materials showing phenomenon tensile strength are:

  • PAI
  • PEEK
  • Nylon
  • PEI

Flexural Modulus of Elasticity:

Flexural modulus of elasticity means the equation of stress applied to the material along the axis of the sample tested and deformation, determined on the same axis. It is also called young’s modulus and elastic modulus. The flexural modulus of elasticity is determined using Hooke’s law.

In Hooke’s law, force is applied to an object which extends it and puts on a behavior pattern using a stress-strain curve in the elastic deformation region. The dimensions such as length and thickness also play a major role in determining the extension of the force.

Flexural modulus is an important mechanical property for selecting the material, product design, and performance analysis.

  1. To decrease the material costs, looking for batch quality and long-term consistency in manufacturing.
  2. To assist the design process.
  3. Handy in selecting materials for various purposes by testing them in different circumstances under different types of forces.

FAQs – 

1. What are the general properties of polymers?

Ans. The general properties of any polymer are decided by its applications. Toughness, reliance, high strength, modulus to weight ratios, corrosion resistance, electrical conductivity, and transparency are general properties of plastics.

2. What are the most important mechanical properties of plastics used in construction?

Ans. Tensile and flexural strength is the most important mechanical properties.

3. Which plastic material has the highest Young’s modulus?

Ans. EVOH – Ethylene Vinyl Alcohol – has the highest young’s modulus.

4. What makes mechanical properties so important for any material?

Ans. If determined correctly, mechanical properties can help in the product’s design process and decrease material costs with more valuable and quality manufacturing.

5. Which is the strongest plastic?

Ans. Polycarbonate is the strongest plastics in the market. It is 200 times stronger than plastics and crack-free.

Suggested Read – 

  • Thermal Properties of Plastics | The Ultimate Guide
  • Polystyrene Repeat Unit | Polystyrene Properties
  • PVC Melting Point, Properties, Applications, Advantages & Disadvantages
  • What is Ultrasonic Welding? | Ultrasonic Welding for Injection Molded Parts | Common Welding Problems and Solutions | Ultrasonic Welding Advantages
  • What is Rotational Molding | Rotational Molding Process | Advantages & Disadvantages | Best Material for Rotational Molding
  • 6 Best Plastic Molding Techniques | A Complete Analysis
  • Extrusion Molding Process ; A Detailed Guide 
  • Plastic Thermoforming Mold: Information about Male Vs. Female Molds
Final Thoughts – 

That was all I had t say about mechanical properties in plastic materials. I believe determining the right mechanical properties is a must for any plastic manufacturer to curing out the supreme quality of products.

Kindly comment your reviews ad thoughts in the comment box

Have a wonderful day.

Filed Under: General Properties

Comments

  1. Brian says

    September 1, 2021 at 12:19 am

    I’m trying to fix a mechanical oven push button that has snapped. It is behind the temperature screen that controls an in increase in temperature. I have Gorrilla Glue which is not recommended for polypropelene , polyethelene, bitumen. How do I determine what it is made of? Believe it or not I melted a piece of tube I cut from a cheap giveaway ballpoint pen. I suspect it is made from one of these plastics not recommended by Gorrila Glue.

    Reply

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