Plastic welding process and advantages.

1. A
SEMINAR REPORT
ON
“PLASTIC WELDING”
Submitted to: Submitted by:
Dr. HC GARG SUKHBIR SINGH
Professor (Mechanical Engg.) 180161610006
MECHANICAL ENGINEERING DEPARTMENT
GURU JHAMBESWAR UNIVERSITY OF SCIENCE &
TECHNOLOGY-HISAR
2019-2020

2. Preface
I have made this report file on the topic Plastic Welding I have tried my best to
elucidate all the relevant detail to the topic to be included in the report. While in the
beginning, I have tried to give a general view about this topic.
My efforts and whole hearted help of each and everyone has ended on a successful
note. I express my sincere gratitude to all who were assisting me throughout the
preparation of this topic. I thank them for providing me the reinforcement,
confidence and most importantly the track for the topic whenever I needed it.

3. Acknowledgement
I would like to thank respected Dr.HC Garg for giving me such a wonderful
opportunity to expand my knowledge for my own branch and giving me guidelines
to present a seminar report. It helped me a lot to realize of what we study for. I would
like to thank my parents who patiently helped me as I went through my work and
helped to modify and eliminate some of the irrelevant or un-necessary stuffs.
I would like to thank my friends who helped me to make my work more organized
and well stacked till the end. Last but clearly not the least, I would thank The
Almighty for giving me strength to complete my report on time.

4. CONTENT
1. INTRODUCTION
2. TYPES OF PLASTIC WELDING
3. DIFFERENT TYPE OF PLASTIC MATERIAL
4. RECENT DEVELOPMENT
5. APPLICATIONS
6. ADVANTAGE
7. DISADVANTAGES
8. FUTURE SCOPE
9. CONCLUSION
10. REFERENCES

5. INTRODUCTION
Now a day’s plastics are used in everyday life from manufacture of toys, to utensil
to complicated part such as heart valve etc. In many industry fields plastic part are
frequently used. Very demanding criteria must now be fulfilled by parts made of
polymeric materials and polymeric composites. Plastics have excellent strength to
weight ratio, good corrosion resistance and ability to take good finish. Plastics can
be categorized as thermosets and thermoplastics. Among these two only the
thermoplastic is weldable. In case of thermosets resin, a chemical reaction occurs
during processing and curing, that is, as a result of irreversible cross-linking reaction
in the mold. Both molded thermosets and vulcanized elastomer components cannot
be reshaped by means of heating, because of the irreversible reaction that occur. So
in this case joining can be obtained by adhesive bonding and mechanical fastening
only. On the other hand, thermoplastic can be softened and can be remolded by the
application of heat, and can fusion welded. Thermoplastics can therefore be welded
by three methods (a) Thermal, (b) Friction (c) Electromagnetic. We will mainly
focus on thermal method of plastic welding which can be further classified as (a)
Hot tool method (b) Hot air technique (c) Infrared heating (d) Laser beam heating
PVC plastics are different from other geomembrane like HDPE, LLDPE, and FPP
because it is primarily amorphous while others are semi-crystalline. When PVC is
heated it will soften, that allow a limited amount of chain entanglements to assure a
strong bond.
Plastic welding: welding for semi-finished plastic materials is described in ISO 472
as a process of uniting softened surfaces of materials, generally with the aid of heat
(except solvent welding). Welding of thermoplastics is accomplished in three
sequential stages, namely surface preparation, application of heat and pressure, and
cooling. Numerous welding methods have been developed for the joining of semi-

6. finished plastic materials. Based on the mechanism of heat generation at the welding
interface, welding methods for thermoplastics can be classified as external and
internal heating methods. Classification of welding methods for semi-finished
polymeric materials. On the other hand, production of a good quality weld cannot
only depend on the welding methods, but also weldability of base materials.
Therefore, the evaluation of weldability is of important critically before welding
operation. Joining of molded plastic parts is required when the finished assembly is
too large or complex to mold in one piece, requires disassembly and reassembly is
necessary, and often to reduce cost to produce a single large molded plastic
component. The plastic parts about to join can be of same or dissimilar materials.
Thermoplastics are generally joined by welding processes, in which the part surfaces
are melted, allowing polymer chains to inter diffuse. Few important welding
processes used for thermoplastics welding are ultrasonic welding, vibration welding,
spin welding, and induction welding.
Welding processes are often categorized and identified by the heating method that
is used. All processes can be divided into two general categories: Internal heating
and External heating, Internal heating methods are further divided into two
categories: internal mechanical heating and internal electromagnetic heating.
External heating methods rely on convection or conduction to heat the weld surface.
These processes include hot tool, hot gas, extrusion, implant induction, and implant
resistance welding. Internal mechanical heating methods rely on the conversion of
mechanical energy into heat through surface friction and intermolecular friction.
These processes include ultrasonic, vibration, and spin welding. Internal
electromagnetic heating methods rely on the absorption and conversion of
electromagnetic radiation into heat. These processes include infrared, laser, radio
frequency, and microwave welding.

7. TYPES OF PLASTIC WELDING
Plastics welding is the process of joining two pieces of Thermoplastics at heated
state and under a pressure as a result of cross-linking of their polymermolecules. The
work pieces are fused together with or without filler material. The joint forms when
the parts are cooled below the Glass Transition Temperature (foramorphous
polymers) or below the melting temperature (for crystalline polymers). Thermosets
(thermosetting resines) in cured condition cannot be welded, since cross-linking of
their molecules has completed.
Plastics welding processes:
 Hot Gas Welding
 Hot Plate Welding
 Ultrasonic Welding
 Spin Welding
 Vibration Welding

8. Hot Gas Welding
Hot Gas Welding is a plastics welding process, utilizing heat of hot gas stream. The
gas (usually air) is heated by electric heating elements mounted within the welding
gun. The torch (welding gun) directs the heated gas toward the work piece surfaces
and a rod of filler material. The edges of the joined parts and the filler rod material
are fused together and pressed. The polymer molecules are cross-linked when the
work pieces cool down, forming a strong joint. Hot Gas Welding is manually
operated process requiring high level of the operator skill. Some polymers (e.g. Low
Density Polyethylene (LDPE), High Density Polyethylene (HDPE)) oxidize at
incresed temperature therefore they are welded by hot Nitrogen.
Applications of Hot Gas Welding:
 Containers;
 Tanks for storage chemicals;
 Ventilation ducting;
 Tubes;
 Repair works.
Hot gas welding

9. Hot Plate Welding
Hot Plate Welding is a plastics welding process, utilizing heat of hot plate placed
between the surfaces to be joined. The work pieces, pressed to the plate, heat up and
soften. After a predetermined time the plate is removed, the parts are brought to the
contact, pressed and fused together. Their polymer molecules are cross-linked when
the work pieces cool down, forming a strong joint. Hot plates are made mainly of
Aluminum alloys. A hot plate is equipped with an electric heating elements and a
thermocouple providing temperature control of the plate surface. Applications of
Hot Plate Welding:
 Components of domestic electric devices (dishwashers, washing mashines,
vacuum cleaners);
 Pipes;
 Automotive components (lights, fuel tanks, reservoirs, batteries). Advantages of
Hot Plate Welding:
 Easily automated;
 High quality tight joints;
 Large and comples parts may be welded;
 Hot plate provides conforming the joined surfaces. Disadvantages of Hot Plate
Welding:
 Long welding cycle: up to 20 sec. for small parts and up to 30 min. for large parts;
 Relatively large amount of flash (excess material) forms.

10. Hot plate welding
Ultrasonic Welding
Ultrasonic Welding is a plastics welding process, in which two work pieces are
bonded as a result of a pressure exerted to the welded parts combined with
application of high frequency acoustic vibration (ultrasonic). Ultrasonic vibration
transmitted by a metal tool (horn, sonotrode) causes oscillating flexing of the
material and friction between the parts, which results in a closer contact between the
two surfaces with simultaneous local heating of the contact area. The plastic melts
in the contact area, the polymer molecules are cross-linked, forming a strong joint.
Ultrasonic Welding cycle takes about 1 sec. The frequency of acoustic vibrations is
in the range 20 to 70 kHz (commonly 20-40 kHz). The ampltude of the acoustic
vibrations is about 0.002” (0.05 mm). Thickness of the welded parts is limited by
the power of the ultrasonic generator. Ultrasonic Welding is used mainly for
processing amorphous polymers (Polysterene (PS), Acrylonitrile-Butadiene-Styrene
(ABS))
Applications of Ultrasonic Welding:
 Medical equipment (filters, face mask, valves, cardiometry reservoir);

11.  Automotive components (glove boxes doors, filters, valves, airflow sensors);
 Appliance (vacuum cleaner, steam iron, dishwasher components);
 Electrical equipment (switches, terminal blocks,connectors);
 Electronic and computer components;
 Toys. Advantages of Ultrasonic Welding:
 Short welding cycle;
 Easily automated and controllable;
 Small amount of flash forms;
 Low energy consumption; Disadvantages of Ultrasonic Welding:
 Only small and thin parts may be welded;
 Tool design is required.
Ultrasonic plastic welding

12. Spin Welding
Spin Welding is a plastics welding process, in which two cylindrical parts are
brought in contact by a friction pressure when one of them rotates. Friction between
the parts results in heating their ends. After a predetermined time the rotation stops
and the molten regions of the work pieces are fused together under an axial pressure
applied until the joint is cooled down. Spin Welding is similar to Friction Welding
(FRW). Spin Welding is used for manufacturing aerosol bottles, floats and other
circular parts.
Advantages of Spin Welding:
 Reproducibility;
 Large parts may be welded;
 High quality weld;
 Oxidizing polymers may be welded.
Disadvantages of Spin Welding:
 At least one of the parts to be welded should have a circular symmetry;
 Minimum rigidity required.

13. Vibration Welding
Vibration Welding is plastics welding process, in which two work pieces are
vibrated at certain frequency and ampltude. The parts rubb each other under a
pressure causing a friction between their surfaces, which generates heat. The heat
results in melting polymer in the joint region. The work pieces are fused together
and after a predetermined time the vibration stops. The polymer molecules are cross-
linked when the work pieces cool down, forming a strong joint. Vibration Welding
cycle is very short (milliseconds). The frequency of acoustic vibrations is in the
range 100 to 500 Hz (commonly 100-240 Hz). The ampltude of the vibrations is
about 0.02- 0.2” (0.5-5 mm). Most polymers (amorphous, semicrystalline and
crystalline) produced various fabrication methods (Thermoforming, Extrusion,
Injection molding, Blow molding,Compression molding, Transfer molding) may be
welded by Vibration Welding. Vibration Welding is used in automotive and
domestic appliance industries.
Advantages of Vibration Welding:
 Oxidizing polymers may be welded;
 Easily automated;
 High productivity;
 Large and complex parts may be welded.
Disadvantages of Vibration Welding:
 Relatively expensive equipment;
 Minimum rigidity required.

14. Vibration welding machine
RECENT DEVLOPMENTS
Friction Welding
Four main variations of friction welding are linear, orbital, spin and angular welding.
Or bital and linear welding are similar in that they are amenable to a wide range of
geometries, while in contrast, angular and spin welding are primarily suitable for
circular weld geometrics. All four processes rely on relative motion between the two
parts that are to be joined, which results in frictional heating. The only major
difference between these processes is the geometry of the relative motion. It is
important to note that in all cases, the angular velocity of the displacement is in
radians/s. In addition, in the case of angular welding the angle of rotation is defined
in radians. With the velocities, it is possible to estimate power dissipation based on
the fundamental assumption that power is equal to velocity multiplied by friction
force as detailed in Grewell, D at all work. Linear vibration welding allows welding
of surfaces that are able to be moved in one direction. However, with linear vibration
welding there is the risk that relatively weak welds can result with walls that are
aligned transversely to the vibration direction. This is due to that fact that without
proper support, either internally with stiffening ribs or externally with built-in

15. features in the fixtures, the walls can deflect and reduce the relative motion of the
interfaces. Orbital welding, produces a relatively constant velocity because of its
elliptical or circular motion assuming the amplitudes in both directions are equal.
This constant velocity dissipates more energy at the joint for a given weld time and
amplitude compared with linear vibration.
Friction plastic welding machine
Laser welding
While laser welding of plastics has been reported as far back at the late 60’s, it has
only become popular in the last decade, primarily due to the significant reduction in
cost for laser energy. The current market prices for lasers is less than 10 $/W,
compared to 1000 $/W just a decade ago. There are two basic modes of IR/laser
welding:
• Surface heating.
• Through Transmission Infrared (TTIr) welding.
While much less common surface heating can be used to weld sub-assemblies.
Surface heating is very similar to heated tool (plate) welding. The surfaces of the
components to be joined are heated by direct IR/laser exposure for a sufficient length
of time to produce a molten layer, usually for 2 to 10 s. Once the surface is fully

16. melted, the IR/laser tool is withdrawn from between the parts, the parts are forged
together, and the melt is allowed to solidify. The heating source must be continuous
thus either the laser/IR source must be achieved through continuous illumination or
high speed scanning. That is to say, because surface heating relies on residual heat
and melting at the faying surfaces, slow-speed scanning is not possible. For example,
high-speed scanning can be used to build up a sufficient melt layer. In this case, the
beam is can be split with a mirror to illuminate both parts simultaneously. The
rotating mirror usually dithers back and forth to direct the beam from one secondary
mirror to the other. In addition, it is possible to rotate the secondary mirrors to
increase the width of the heated area. TTIr welding is based on the concept of passing
IR/laser radiation (typically with wavelengths (k) between 800 to 1100 nm) through
one of the components to be welded while having the second component absorb the
light at the interface .This absorption results in heating and melting of the interfaces.
TTIr welding is used for such applications as automotive lamps and medical
components. It is well suited for applications that require hermetic seals with minima
marking and low flash/particulate generation. In terms of laser welding of plastic, it
is currently the most popular mode of operation, because it offers several additional
benefits compared to surface heating. For example, it is a pre-assembled method.
This means that the parts are placed into the machine in the same position and
orientation as the final assembled position. For many applications this is critical to
allow sub-components to be held in place during the welding process without
complex fixtures.

17. Laser plastic welding machine
RF welding
Radio Frequency (RF) welding, which is also often referred to as “dielectric
welding” is a process that relies on internal heat generation by dielectric hysteresis
losses in thermoplastics with polar side groups. In a rapidly changing electric field
these polar groups try to orient themselves in the field resulting in intermolecular
friction and heat generation. It is most commonly used to weld PVC bladders, such
as intravenous drip bags for the medical industry. It is also used to weld books and
binding covers. RF welding has the advantages that it is a relatively fast process with
typical cycle times ranging from less than 1s to 5s. It also does not require any special
joint designs and produces welds that are relatively appealing cosmetically.
RF welding is almost exclusively used for welding thin sheets or films. Thickness
usually ranges from 0.03 to 1.27mm (0.001 to 0.050 in), depending on the material
and application. The limitation of welding films is due to the fact that a strong
electric field must be generated and this can only be achieved when the welding
electrodes are brought together in close proximity (0.03 to 1.27mm). If the welding

18. electrodes are significantly further apart, the electric field density is too low to
effectively heat and melt the plastic. Another limitation of the process is that the
materials being joined must have the proper electrical properties. One such property
is a relatively high dielectric constant, typically ≥ 2. This allows more current to flow
through the material, which promotes heating at a lower electrode voltage. The other
major material restriction for RF welding is that the material must have a relatively
high dielectric loss. The basic concept relies on applying a relatively high electric
field across the films to be joined. The electric field is concentrated by using raised
electrodes adjacent the faying surfaces. The electrodes are connected to a high
voltage, high frequency power (27.12 MHz) supply that is tuned to match the
electrical impedance of the weld.
In many applications, the welding die or electrode trims or cuts the film/sheets to the
final shape in addition to sealing. However, since the electrodes, even at the cutting
edge, cannot be allowed to make contact while the electric field is applied (to prevent
machine damage), there is usually a small amount of material remaining at the toe
of the weld.
Radio Frequency plastic welding Machine

19. DIFFERENT TYPES OF PLASTIC MATERIAL
Thermoplastics like Polyethylene, Polypropylene, Polyvinyl Chloride, Polyurethane
and Acrylonitrile Butadiene Styrene (ABS) are frequently used in plastic welding.
Plastics that can be welded are called “thermoplastics”. The thermosetting plastics
are straight opposite to the thermoplastics in nature.In Plastic welding gun both
thermo plastics and thermosetting plastics can be welded. But the common fact in
this material is both parent material and welding rod material should be same to
execute the operation. It means that the defected part that to be welded and the
welding rod must be similar in material. Also they must be similar in all aspects like
properties and characteristics. Only then it is quite possible to execute the operation.
THERMOPLASTICS
Thermoplastic welding has been successfully used for over 30 years. It is a process
that most people can learn to do in a very short time. Many products today are made
with thermoplastics. Up till now there has been no simple means for repairing these
plastics. The Malcom plastic welding kit has all the tools needed to perform most
plastic welding repairs and fabrication work. In order to weld plastics, you must first
have some basic understanding of what plastics are the various types of welds
commonly used and an understanding of the differences of tack welding, pendulum
welding and speed welding. The Plastic Welding School plastic welding instruction
booklet is a basic training book that will help you understand what plastics are, the
basics of welding plastics and how to fabricate and perform plastic repairs. Only
through practice welding will confidence be achieved to begin fabrication and
perform repairs. . The necessary conditions for welding are: 1. A plastic joining
area. 2. The merging of the plastic materials. 3. A heat source. (Leister tools)

20. 4. The coordination of the process of the most important factors of heat - pressure -
time 5. Only plastics that are thermoplastics can be welded and only like
thermoplastics can be welded. Each thermoplastic has a particular melting
temperature and viscosity, therefore, it should be noted that only the same
thermoplastics could be welded to each other. Some thermoplastics, on account of
their very high molecular mass, do not achieve a sufficient ability to flow and cannot
be welded. The ideal welding temperature varies between the various types of
plastics. The Leister tools allow you to dial in the correct temperatures of the various
plastics that you may encounter.
CODE OF THERMOPLASTICS
The codes of thermoplastics are derived in detail as follows. The codes are nothing
but the abbreviations. As the names of these plastics are somewhat difficult to
pronounce and remember, the codes are derived. So it becomes simpler to pronounce
and remember. In markets we can find only the codes of the plastics, not the
expansions.
ABS : Acrylonitrile Butadiene Styrene
ABS/PC : Polymer alloy of above
PA : Polyamide (Nylon)
PBT : Polybutylen Terephtalate (POCAN)
PC : Polycarbonate PE : Polyethylene
PP : Polypropylene
PP/EPDM : Polypropylene/Ethylenediene Rubber
PUR : Polyurethane (Not all PUR is weldable)

21. PVC : Polyvinyl Chloride GRP/SMC : Glass Fiber Reinforced Plastics (Not
weldable)
ACRYLONITRILE BUTADIENE STYRENE (ABS) Acrylonitrile butadiene
styrene is a common thermoplastic. Its glass transition temperature (ABS is
amorphous and therefore has no true melting point) is approximately 105 °C (221
°F).It is a copolymer made by polymerizing styrene and acrylonitrile in the presence
of polybutadiene. The proportions can vary from 15 to 35% acrylonitrile, 5 to 30%
butadiene and 40 to 60% styrene. For the majority of applications, ABS can be used
between −20 and 80 °C (-4 and 176 °F) as its mechanical properties vary with
temperature. The properties are created by rubber toughening, where fine particles
of elastomer are distributed throughout the rigid matrix. Production of 1 kg of ABS
requires the equivalent of about 2 kg of petroleum for raw materials and energy. It
can also be recycled. ABS plastic is damaged by sunlight. This caused one of the
most widespread and expensive automobile recalls in US history.
PROPERTIES OF ABS:
ABS is derived from acrylonitrile, butadiene, and styrene. Acrylonitrile is a synthetic
monomer produced from propylene and ammonia. The advantage of ABS is that this
material combines the strength and rigidity of the acrylonitrile and styrene polymers
with the toughness of the polybutadiene rubber. The most important mechanical
properties of ABS are impact resistance and toughness. A variety of modifications
can be made to improve impact resistance, toughness, and heat resistance. The
impact resistance can be amplified by increasing the proportions of polybutadiene
in relation to styrene and also acrylonitrile, although this causes changes in other
properties. Generally ABS would have useful characteristics within a temperature
range from -20 to 80 °C (-4 to 176 °F).. Fibers (usually glass fibers) and additives

22. can be mixed in the resin pellets to make the final product strong and raise the
operating range to as high as 80 °C (176 °F). Pigments can also be added, as the raw
material original color is translucent ivory to white. The aging characteristics of the
polymers are largely influenced by the poly butadiene content.
POLYIMIDE (PA) Polyimide (sometimes abbreviated PI) is a polymer of imide
monomers. Polyimides have been in mass production since 1955. Typical monomers
include pyromellitic dianhydride. Thermosetting polyimides are known for thermal
stability, good chemical resistance, excellent mechanical properties, and
characteristic orange/yellow color
PROPERTIES OF PA Polyimides compounded with graphite or glass fiber
reinforcements have flexural strengths of up to 50,000 p.s.i. (345 MPa) and flexural
moduli of 3 million p.s.i. (20,684 MPa). Thermoset polyimides exhibit very low
creep and high tensile strength. These properties are maintained during continuous
use to temperatures of 450 °F (232 °C) and for short excursions, as high as 900 °F
(482 °C). Molded polyimide parts and laminates have very good heat resistance.
Normal operating temperatures for such parts and laminates range from cryogenic
to those exceeding 500 °F (260 °C). Polyamides’ are also inherently resistant to
flame combustion and do not usually need to be mixed with flame retardants. Most
carry a UL rating of VTM-0. Polyimide laminates have a flexural strength half life
at 480 °F (249 °C) of 400 hours.
POLYBUTYLENE TEREPHTHALATE (PBT) Polybutylene terephthalate (PBT)
is a thermoplastic engineering polymer, that is used as an insulator in the electrical
and electronics industries. It is a thermoplastic (semi) crystalline polymer, and a type
of polyester. PBT is resistant to solvents, shrinks very little during forming, is

23. mechanically strong, heat-resistant up to 150 °C (or 200 °C with glass-fiber
reinforcement) and can be treated with flame retardants to make it noncombustible.
PROPERTIES OF PBT:
PBT is closely related to other thermoplastic polyesters. Compared to PET
(polyethylene terephthalate), PBT has slightly lower strength and rigidity, slightly
better impact resistance, and a slightly lower glass transition temperature. PBT and
PET are sensitive to hot water above 60 °C (140 °F). PBT and PET need UV
protection if used outdoors, and most grades of these polyesters are flammable,
although additives can be used to improve both UV and flammability properties.
POLYCARBONATE (PC)
Polycarbonates, known by the trademarked names Lexan, Makrolon, Makroclear
and others, are a particular group of thermoplastic polymers. They are easily worked,
molded, and thermoformed. Because of these properties, polycarbonates find many
applications. Polycarbonates do not have a unique plastic identification code.
PROPERTIES OF PC:
Polycarbonate is a very durable material. Although it has high impact-resistance, it
has low scratch-resistance and so a hard coating is applied to polycarbonate eyewear
lenses and polycarbonate exterior automotive components. Polycarbonate has a
glass transition temperature of about 150 °C (302 °F), so it softens gradually above
this point and flows above about 300 °C (572 °F). Tools must be held at high
temperatures, generally above 80 °C (176 °F) to make strain- and stress-free
products. Low molecular mass grades are easier to mold than higher grades, but
their strength is lower as a result. The toughest grades have the highest molecular
mass, but are much more difficult to process.

24. POLYETHYLENE (PE)
Polyethylene or polythene (IUPAC name polyethene or poly(methylene)) is the most
widely used plastic, with an annual production of approximately 80 million metric
tons. Its primary use is within packaging (plastic bag, plastic films, geomembranes,
etc.). Polyethylene is a thermoplastic polymer consisting of long chains produced by
combining the ingredient monomer ethylene (IUPAC name ethene), the name comes
from the ingredient and not the actual chemical resulting.
The ethylene actually converts to ethane as it takes its place in a polymer and straight
sections of the polymer are the same structure as the simple chain hydrocarbons,
e.g., propane, decane and other straight single-bonded carbon chains.As with any
polymer, the structure of the resulting substance defies molecular description due to
cross branching of the chains. The scientific name polyethene is systematically
derived from the scientific name of the monomer.
PROPERTIES OF PE:
Depending on the crystallinity and molecular weight, a melting point and glass
transition may or may not be observable. The temperature at which these occur
varies strongly with the type of polyethylene. For common commercial grades of
medium- and high-density polyethylene the melting point is typically in the range
120 to 130 °C (248 to 266 °F). The melting point for average, commercial, low-
density polyethylene is typically 105 to 115 °C (221 to 239 °F). Most LDPE, MDPE
and HDPE grades have excellent chemical resistance and do not dissolve at room
temperature because of their crystallinity. Polyethylene (other than cross-linked
polyethylene) usually can be dissolved at elevated temperatures in aromatic
hydrocarbons such as toluene or xylene, or in chlorinated solvents such as

25. trichloroethane or trichlorobenzene. When incinerated, polyethylene burns slowly
with a blue flame having a yellow tip and gives off an odour of paraffin. The material
continues burning on removal of the flame source and produces a drip.
POLYPROPYLENE (PP)
Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in
a wide variety of applications including packaging, textiles (e.g., ropes, thermal
underwear and carpets), stationery, plastic parts and reusable containers of various
types, laboratory equipment, loudspeakers, automotive components, and polymer
banknotes. An addition polymer made poly propylene from the monomer propylene,
it is rugged and unusually resistant to many chemical solvents, bases and acids.
PROPERTIES OF PP:
Most commercial polypropylene is isotactic and has an intermediate level of
crystallinity between that of low-density polyethylene (LDPE) and high-density
polyethylene (HDPE). Polypropylene is normally tough and flexible, especially
when copolymerized with ethylene. This allows polypropylene to be used as an
engineering plastic, competing with materials such as ABS. The melting of
polypropylene occurs as a range, so a melting point is determined by finding the
highest temperature of a differential scanning calorimetry chart. Perfectly isotactic
PP has a melting point of 171 °C (340 °F). Commercial isotactic PP has a melting
point that ranges from 160 to 166 °C (320 to 331 °F), depending on atactic material
and crystallinity. Syndiotactic PP with a crystallinity of 30% has a melting point of
130 °C (266 °F).[2] The melt flow rate (MFR) or melt flow index (MFI) is a measure
of molecular weight of polypropylene. The measure helps to determine how easily
the molten raw material will flow during processing. Polypropylene with higher

26. MFR will fill the plastic mold more easily during the injection or blow-molding
production process. As the melt flow increases, however, some physical properties,
like impact strength, will decrease.
POLYURETHANE (PUR)
A polyurethane (PUR and PU) is polymer composed of a chain of organic units
joined by carbamate (urethane) links. Polyurethane polymers are formed by
combining two bi- or higher functional monomers. One contains two or more
isocyanate functional groups and the other contains two or more hydroxyl groups.
More complicated monomers are also used. The alcohol and the isocyanate groups
combine to form a urethane linkage.
POLYVINYL CHLORIDE (PVC)
PVC production is expected to exceed 40 million tons by 2016. It can be made softer
and more flexible by the addition of plasticizers, the most widely used being
phthalates. In this form, it is used in clothing and upholstery, electrical cable
insulation, inflatable products and many applications in which it replaces rubber.
Pure polyvinyl chloride without any plasticizer is a white, brittle solid. It is insoluble
in alcohol, but slightly soluble in tetrahydrofuran.
THERMOSETTING PLASTICS
A thermosetting plastic, also known as a thermo set, is polymer material that
irreversibly cures. The cure may be done through heat (generally above 200 °C (392

27. °F)), through a chemical reaction (two-part epoxy, for example), or irradiation such
as electron beam processing.
Thermo set materials are usually liquid or malleable prior to curing and designed to
be molded into their final form, or used as adhesives. Others are solids like that of
the molding compound used in semiconductors and integrated circuits (IC). Once
hardened a thermo set resin cannot be reheated and melted back to a liquid form.
PROPERTIES OF THERMOSETTING PLASTIC:
Thermo set materials are generally stronger than thermoplastic materials due to this
three dimensional network of bonds (cross-linking), and are also better suited to
high-temperature applications up to the decomposition temperature. However, they
are more brittle. Many thermosetting polymers are difficult to recycle.
DIFFERENCES BETWEEN THERMOPLASTICS AND TERMOSETPLASTICS
The essential difference is that thermoplastics remain permanently fusible so that
they will soften and eventually melt when heat is applied, whereas cured thermoset
polymers do not soften, and will only char and break down at high temperatures.
This allows thermoplastic materials to be reclaimed and recycled. The reason for
this is that thermoplastics have relatively weak forces of attraction between the
chains, which are overcome when the material is heated, unlike thermosets, where
the cross-linking of the molecules is by strong chemical bonds. Effectively the
thermoset is one large molecule, with no crystalline structure. Compared with
thermoplastics, thermosets are generally harder, more rigid and more brittle, and
their mechanical properties are not heat sensitive. They are also less soluble in
organic solvents.

28. APPLICATIONS
Aeronautics
Interior panels
Holdings tanks
Tray
Agriculture
Gaskets
Pvc fencing
Chick Hatchery Boxes
Tanks
Water & Misting Lines
Fittings
Automotive
Grills
Radiators
Battery Cases
Wheel Well Liners
Bumpers
Instrumentation Panels
Truck Liners
R.V.s

29. Fresh, Grey & Black Water Holding Tanks
Industrial
Fan Housings, Pails, Ductwork, Flues, Plenums, Screens, Displays, Pipe, Fittings,
Tanks, Dampers, Storage Tanks, Waste Canisters, Sinks, Dippers, Pans, Stands,
Filter Housings, Etching Tanks, Beams, Slides, Gates, Hangers, Vents, Fixtures,
Hoods, Trays, Stack Caps, Blower Housings, Etching Machines, Manifolds,
Louvers, Frames, Valves, Conduit Fittings
Marine
Boats
Ballast Tanks
Fish Holding Wells
Fresh, Gray & Black
Water Holding Tanks
Plumbing
DWV Pipes
Pipes
Drains
Sinks
Faucets
Others
Toys
Any thermoplastic part.

30. ADVANTAGES
Advantages of Specific Types of Plastic Welding
Advantages of Ultrasonic Welding
 Very fast process (typically < 1 second)
 Advanced, modern equipment with sophisticated control and monitoring
features
 Economical
Advantages of Spin Welding
 Relatively low cost of equipment
 Not too many geometry restrictions outside of joint shape which must be
circular
 High-quality welding for a wide range of thermoplastics
Advantages of Vibration Welding
 Applicable to large parts
 Internal walls can be welded
 Well established process with excellent control possible
Advantages of Hot Plate Welding
 Simple and reliable
 Suitable complex part geometries, even in the joining plane
 Can be adapted for use with materials which have different melting
temperatures and melt viscosities
 Relatively high tolerance to imperfections on the mating surfaces
Advantages of Laser / IR Welding

31.  Very clean process, little to no weld flash
 Precise control / selective heating
 Works with simple joint designs (uniform contact of mating surfaces)
Advantages of Implant Induction / Resistance Welding
 Non contact heating method reduces opportunity to damage parts during
welding process
 Applicable to large parts
 Works for complex joint planes
Advantages of Radio Frequency Welding
 High energy efficiency
 Bonds film or thin sheets with complex circumference geometry.

32. DISADVANTAGES
Disadvantages of Specific Types of Plastic Welding
Disadvantages of Ultrasonic Welding
 Requires a specific joint design, usually complex and often challenging to
mold
 Many geometry limitations relating to transfer of acoustic energy
 Vibration may cause damage to sharp radiused areas or small cross-
sectional areas
Disadvantages of Spin Welding
 Only works for parts with circular joints
 Produces particulate (plastic dust)
Disadvantages of Vibration Welding
 High capital cost (equipment and fixtures)
 Very loud
 Thin walls tend to flex and deform, which impedes welding
Disadvantages of Hot Plate Welding
 Relatively slow
 Energy inefficient
 Hot polymer melt often sticks to the hot plate surface
Disadvantages of Laser / IR Welding
 Relatively new welding process so there are few experts and small base of
experience to draw from
 Optical properties of polymer are very critical

33.  Eye protection is mandatory for lasers - safety precautions can significantly
add to cost of equipment
Disadvantages of Implant Induction / Resistance Welding
 High consumable cost due to insert (ferromagnetic material)
 Uncommon welding process means few process experts
 May damage internal electrical components
Disadvantages of Radio Frequency Welding
 Shielding requirement is required to prevent operator exposure to
electromagnetic field
 Equipment can be fairly expensive
 Materials must be dipole (with a positive and negative pole) in order to be
welded with this method.

34. FUTURE SCOPE
In this work, the temperature distributions at the joint area are simulated using
viscoelastic heating and experimental validation of results using measurement of
temperature are carried out.. A thermal model based on wave propagation in
polymers can provide details of the temperature, stresses and strains in a
comprehensive manner. This will help in the design of new products. When joints
are designed for new products the knowledge of the already existing joints are to be
made use of. An expert system if developed can provide the necessary information
with a perfect blend of information technology and the engineering knowledge of
the existing products, adding value to the CAD/CAM solutions. Such a system can
be developed. The design of fixtures for ultrasonic welding of thermoplastics is
another area of interest. Though principles of location can be used as in a
conventional case, the vibration characteristics of fixtures will play an 125 important
role in their design. The whole system should vibrate at one frequency. Currently,
most welds were made with predetermined amplitude of vibration which is held
constant during the cycle. As most welding systems are pneumatically driven, the
weld force is relatively constant. Because a thermoplastic goes through several
phases during a weld cycle, each stage may benefit from different amplitudes and
forces to increase weld quality in terms of strength, consistency and cycle time. This
is called amplitude and force profiling. Latest ultrasonic welding machines are
available with profiling mechanism. Modeling of ultrasonic welding system with
force and amplitude profiling, to find out optimum values of weld parameters in each
stage, will help improve the quality of weld.

35. CONCLUSION
This seminar provides more examples of plastic applications, types of welding
technologies involved in the plastic materials.And the characteristics of
thermoplastic and thermosetting plastics have given clearly. It helps to know how to
achieve the arriving at a proper and effective design of electrically driven plastic gun
for much efficient employment, fabrication of the electric plastic gun based on the
design developed, testing and proving the efficiency of the developed plastic gun
than the existing hot air gun. Moreover an effective comparison is made with the
conventional welding model to enlist the advantages of this electric welding gun.
The cost effectiveness of this new welding gun will also be assessed in the light of
the present market value. This project provides more examples of plastic
applications, types of welding technologies involved in the plastic materials .And
the characteristics of thermoplastic and thermosetting plastics have given clearly.
And this project work has provided me an excellent opportunity and experience, to
use my limited knowledge. I feel that the project work will be a good solution to the
drawbacks of existing hot air plastic welding gun .In plastic welding joining is
adhesive and weld bead is weaker than parent material that’s why plastic welding
is not very popular. In the field of plastic welding by hot air technique immediate
work is needed as study of effect of current and voltage, optimization of the process
etc. In the present paper the different techniques of welding of plastics is reviewed
with the help of available relevant literature. As this is the period of plastic age,
joining of plastics is a challenge to young researchers and scholars working in the
area of welding technology. Although there are several methods that are reported to
join two plastic pieces but hot air gun technique is most reliable and techno
commercially beneficial from research as well as production point of view and more
work is required in this area in order to understand effect of different process

36. parameters on the main response parameters. So, after this review there is a need to
take initiative for the experiments for making the results more favorable. Further
response parameters such as tensile test, hardness test and grain size can be analyzed.

37. REFRENCES
[1] Vijai Kumar, M.I. Khan Development of Welding Procedure for Rigid P.V.C.
Plastic by Hot air Technique
[2] M. Rojek a, J. Stabik, G. Muzia. Thermography in Plastics Welding Processes
assessment Volume 41 Issues 1-2 July- August 2010
[3] Thomas H. North and Geeth a Ramarathnam, University of Toranto Welding of
Plastics
[4] O. Balkan a,*, H. Demirer b, H. Yildirim c Morphological and Mechanical
Properties of Hot Gas Welded PE, PP and PVC sheets Volume 31 Issues 1 November
2008
[5] W. S. Alley/ P. N. Baker Chapter-2 Joining and Assembly of Plastics, Volume-
2 Identification, Testing and Recycling of Plastics, Handbook of plastic technology
[6] Thermally Bonded PVC seams Phase 1 “State- Of- The- Art & Preliminary
Welding windows Tri/Environmental, INC, A Texas research international company
[7] D. Grewell. A. Benatar Agricultural and Biosystems Engineering. Iowa State
University, Ames, IA, USA Welding of plastic: Fundamentals and New
developments
[8] James D. Van de Ven, Arthur G Erdman, Mechanical Engineering Department,
University of Minnesota, Minnesota 55455 Hot Psin Welding of Thin Poly (vinyl
Chloride) sheet
[9] Stanley Grave line Welding of Thermoplastic Roofing Membranes Subjected to
Different Conditioning procedures Journal of ASTM International, Vol.4, No.8
Paper ID JAI101018

38. [10] American Plastic Welding Technologies, Hot Air Welding Guide For Plastic
Repairs www.bak-ag.com.
[11] Mahmood Alam, (Dr.) M. I. Khan, Integral University, Lucknow, state-of-the-
art in rigid p. v. c. Plastic welding by hot air Technique, International Journal of
Technical Research and Applications e-ISSN: 23208163,www.ijtra.com Volume 1,
Issue 2 (May-June 2013), PP. 20-23
[12] Schaible, S., Cakmak, M.: Dynamics and Structure Development in Spin
Welding of Polyvinylidene Fluoride Cylindrical Rods, Int. Polym. Process. 10, p.
270 (1995)
[13] Grewell, D., Benatar, A.: A Process Comparison of Orbital and Linear
Vibration Welding of Thermoplastics, Annual Technical Conference for the Society
of Plastic Engineers Proceedings, Society of Plastics Engineers, Brookfield, CT
(1999).
[14] Md Shakibul Haque, Manoj Kumar and Adnan Khan: Hot Gas Welding of
Plastic: Fundamentals & Importance, Invertis Journal of Science and Technology,
Vol. 8, No. 4, 2015 ; pp. 216-219 (Printed: ISSN 0973-8940 Online: ISSN 2454-
762X)
[15] Md Shakibul Haque, Inayat Hussain, Gaurav Agarwal, Khwaja Moeed, Mohd
Anees Siddiqui: Experimental Analysis of Mechanical Behaviour of Poly Vinyl
Chloride (PVC) Plastic Welded through the Fabricated Experimental Set-up for Hot
Air Welding, International Journal for Scientific Research & Development, Vol. 3,
Issue 11, 2016, ISSN (online): 23210613
[16] Md Shakibul Haque, Inayat Hussain, Proff. (Dr.) Athar Hussain, Mohd Anees
Siddiqui, Proff. (Dr.) Mohd. Ibrahim Khan: Study and Experimental Modelling of

39. Welding Parameters on Hardness of Hot Air Welded Poly Vinyl Chloride (PVC)
Plastic, International Journal for Scientific Research & Development, Vol. 3, Issue
10, 2015, ISSN (online): 2321-0613
17 N.s. Taylor, The Feasibility of Socketfusion Welding Thermoplastic Composite
Materials, construction and building materials ,volume 3, issue 4, December 1989,
pages 213–219. journal is presented at ,institute of polymer engineering at Germany.
18. Michael J. Troughton, "Handbook of Plastics Joining, A Practical Guide", 2nd
ed., 2008,
19 Michael J. Troughton, "Handbook of Plastics Joining, A Practical Guide", 2nd
ed., 2