briefly described difference between thermosets and thermoplastics

1. (Department of Metallurgical & Material Engineering)
University of Engineering & Technology, Lahore
Muhammad Muneeb Saeed
Reg. No. 2016-MM-4
Lab Activity No. 01
Identification of Thermosetting plastic &
Thermoplastic samples by FLAME TEST.

2. (Department of Metallurgical & Material Engineering)
University of Engineering & Technology, Lahore
Submitted To: -
Ma’am Khushnuda Nur
Submitted By:
Muhammad Muneeb Saeed
Reg. No. 2016-MM-4
Lab Activity No. 01
Identification of Thermosetting plastic &
Thermoplastic samples by FLAME TEST.

3. 1.1. Polymer:
The word polymer means ‘many parts’. A substance which has a molecular structure
chemically built up chiefly or completely from a large number of similar monomer units bonded
together to form a long chain compounds chiefly of carbon e.g. many natural and synthetic organic
materials used as plastics and resins. Other materials like Si can also make long chain compound. [1]
Fig# 01: A
Polymeric Structure [1]
1.1.1. Plastic polymer:
Plastics are mainly derived from materials found in nature, such as natural gas, oil, coal,
minerals and plants, called natural polymers. These are proteins, enzymes, starches, and cellulose. Now
day’s plastics can also be made manually in industry called synthetic polymer plastics. Many of our
useful plastics, rubbers, and fiber materials are synthetic polymers. [2]
Pure plastic polymers are made of long chain of hydrocarbons compounds. But other
element like O, N, S and Si can also be part of polymers. Some other materials also added to the plastic
to compete our requirements. These materials are strengtheners and additives (fillers, plasticizers,
coloring elements and flame retardants).
Fig# 02: Polymers Plastics
1.1.2. Additives:
Additives are added to the polymers to
 improve the thermal stability
 to make them recyclable
 processing stability when they are processed even with inorganic compounds
 strengthen the polymer

4. Examples of additives:
 Fillers (mostly organic in nature like starch)
 Plasticizers (to improve plasticity , low Molecular weight with phenols)
 Coloring elements
 Flame retardants (to prevent for flaming)
Fig# 03: Additives for plastics
1.2. Dissociationpoint of polymer:
Some polymers, like poly vinyl chloride (PVC), when they are heated, the other elements
like chlorine in this case break its bond with carbon and make HCl and fuse out in air. This entire
phenomenon happens before melting of this polymer and this temperature called dissociation point of
that specific polymer and most of the time it is lower than melting point of the polymer.
𝑛 [—CH₂ —CHCl―] 𝑛 + Heat → 𝑛 [—C̊ H—C̊ H—] 𝑛 + HCl↑
1.3. Types of polymer plastics on the mechanicalforce response at elevated
temperature: [2]
All the polymers plastics are divided into two categories on the basis of their response on
mechanical force at high temperature.
 Thermoplastics
 Thermosetting plastics
Fig#04: Thermoplastics and Thermosetting

5. 1.3.1. Thermoplastics:
Thermoplastic materials are types of plastic which become soft when they are heated
and hard when they cool down without appreciable change in properties [2]. The reason for this type of
behavior is because of their secondary bond between hydrocarbon chains. When they are heated even at
very low temperature their secondary bond, because of elevation of energy, breaks very early and result
is melting. [1]
Fig# 05: Heating effect of Thermoplastics
1.3.2. Thermosetting plastics:
The polymer plastics, which are harden permanently after one application of heat and
can’t be remolded by heating [2]. The reason behind this phenomenon is their covalent bond between the
hydrocarbon long chains (Cross Links). When they are heated, as both bonds (C-C bond & Cross Links)
are at same energy level, are not affected. But continuous elevation of heating both the bonds are
decomposes and result will be intense black fumes (not melted). [2]
Fig# 06: Heating effect of Thermosetting

6. 2. Experimental work:
2.1. Apparatus
 Different samples made of polymeric materials
 A tong / scapula / metallic wire.
 Bunsen burner.
2.2. Procedure:
 The Bunsen burner was light on with the help of match.
 The flame was kept golden to avoid the intense heating.
 Among the samples, marked 1 to 5, first sample was held in tong or placed on scapula and
brought close to the golden flame.
 The sample was allowed to be heated.
 The behavior of the sample in response to heat penetration was studied and noted down.
 The same method was repeated for the other four samples and results were recorded.
3. Observation & Results:
Table# 01: table of observation and results
Sample
Number
Observations Result(material)
1. Melted immediately and was easily flow able
1. Fastest melting
2. Rather slow melting
3. Slower melting
Pure Polymer (C&H)
[Thermoplastic]
1. Polyethylene
2. Polypropylene
3. Polystyrene
2. Gives some smoke and melted in some seconds Colored Thermoplastic
3. Melted after some time but molt was hard to flow PVC Thermoplastic
4. Gave smoke and didn’t melt but decomposed at intense heating Bakelite [Thermoset]

7. Refrences:
[1]: Introduction to Materials by William F.Smith
[2]: Materials Science and Engineering_ An Introduction-Wiley (2013) by William D. Callister, David
G. Rethwisch