The aim of the present work is to study the effect of the addition micro platelets and nano spherical particles of aluminum on the thermal, mechanical, morphological and electrical properties of the PET/PBT/Al composites prepared by melt compounding followed by injection molding.
The SEM results showed that the Al particles are uniformly distributed in the PET/PBT matrix. The micro Al seem to be parallel and oriented to the direction of the flow. The crystalline peaks of the blend did not appear in X- ray diffraction pattern due to skin- core structure of PET/PBT blend. FTIR analysis demonstrated that there is no chemical interaction between PET and PBT nor between Al and matrix. The TGA of the Al micro-platelet composites and the Al nano-spherical composites showed that the end of degradation in most compositions shifts to higher temperatures. Analysis of the DSC results revealed that the melt crystallization temperature of Al micro composites and Al nano composites increased by 4 to 14 degrees compared to the neat PET/PBT. The impact strength of Al micro composites increased until it reached the highest value of 53.54 J/m for 3 vol. % which is about 58% higher than that of the neat blend. The tensile strength of the Al nano-spherical composites decreased with increasing Al content. However, the micro Al particles increased the tensile strength of the Al micro composites. This is explained by the good dispersion and excellent interfacial adhesion between the flaky Al and PET/PBT matrix. There is an enhancement in the flexural strength values with increase in the volume fraction ratio of Al powders in the Al micro composites until it reaches maximum value for the sample with 15 vol. % loading. A decrease in the flexural strength was observed for Al nano composites. The flexural modulus of the Al micro composites showed a significant and remarkable results where the flexural modulus rose gradually and reached to 5.66 GPa at highest Al loading of 25 vol. %. The maximum volume fraction of 25 vol. % showed the highest thermal conductivity of 0.561 W/mK which is about 55.61 % higher compared to that of the neat blend. At 25 vol. % the volume electrical resistivity of the composites decreases significantly and a value of 107 Ωcm was obtained which makes these composites a material of choice for electrostatic and dissipative applications. Al-PET/PBT Composites bar did not show much shrinkage or distortion heating at 150C and 200C.
Preparation and Characterization of PET / PBT / Aluminum Polymer Blend Composites
1. MasterThesis Defense
Preparation and Characterization of PET / PBT /
Aluminum Polymer Blend Composites
Prepared by:
Abdullah Karama Alhamidi
438106308
1st Semester 1443 H
Chemical Engineering Department
College of Engineering
King Saud University
1
2. 2
Preparation and Characterization of PET / PBT / Aluminum
Polymer Blend Composites
بيوتيلين والبولي تيريفثاليث إيثيلين البولي من المكونة البوليمر خليط مركبات وتوصيف تحضير
تيريفثاليت
واأللومنيوم
Supervised by:
Prof. Saeed Mohammed Al-Zahrani
Dr. Arfat Anis
Examination Committee Members:
Prof. Othman Yahya Al-Othman
Dr. Abdulaziz Abdullah Al-Ghyamah
Dr. Maher Mohammed Al-Rashed
4. Abstract
• The aim of the present work is to study the effect of incorporation of micro and
nano particles of aluminum in the PET/PBT blend prepared by melt
compounding in a twin-screw extruder followed by injection molding.
• Properties studied include thermal, mechanical, morphological properties and
electrical and thermal conductivity.
4
5. Introduction
Polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) are
two of the most important members of the commercial thermoplastic
polyester family.
PET and PBT advantages:
Resistant to solvents
Highly crystalline melting points
PET is mainly used to produce
synthetic fibers and soft drink bottles.
PBT is used in the electronic products
and automobile industry.
5
6. PBT has advantages of:
Fast rate of crystallization
Superior process ability
Rapid molding
PET shows some drawbacks:
Slow rate of crystallization
PET is a relatively low-cost polymer which provide a cost incentive to
blend with other polymers.
6
Introduction
• PET and PBT are chemically similar and completely miscible blend.
7. • 40/60 PET/PBT blends are commercially used to combine advantages of
both polymers: PET gives high flow, and a good surface finish, while the
PBT crystallizes faster and nucleates the crystallization of the PET
• PET/PBT blends are used to manufacture the visible parts of devices that
require a smooth and shiny surface with high hardness and strength.
7
Introduction
8. Unfilled PET/PBT blends have some disadvantages such as:
• Sensitive to notching
• low heat deformation temperature
metal fillers can improve the properties of polymers such as mechanical,
thermal, electrical, and optical properties
8
Introduction
9. Why Aluminum?
Aluminum-polymer composites have
advantages of:
Low cost
Lightweight
High corrosion resistance
Rapid fabrication rate
The thermal and electrical conductivity of polymers can be
improved with the addition of Al fillers.
PET/PBT/Al composites can be cost effective and suitable option for
injection molding applications. 9
Introduction
10. Literature Review
• PET/PBT blend had a considerable attention for the few last decades.
• Many research groups had studied PET/PBT blends and focused on different
aspects such as:
The miscibility
Crystallization
Transesterification
The thermal, mechanical, and morphological properties
To the best of our knowledge, no studies have been carried out to determine the
effect of incorporation of aluminum particles on the properties of PET/PBT
blend composites.
10
12. 12
Operating Conditions:
• Melting temperature: 260 oC
• Screw speed: 100 rpm
• Mixing time: 3 min
• The holding pressure: 6 bar
• Mold temperature: 24-26 oC
• Total injection molding cycle time: 45 s
Composites Preparation
13. 13
Standard Specimens For Characterization
PBT
40/60 PET/PBT
PET
Micro composites
Nano composites
(ASTM D 256-04)
(ASTM D638-14)
(ASTM D 790-03)
Conductivity
14. Composites Characterization
Scanning Electron Microscope (SEM)
X-ray Diffraction (XRD)
Polarizing Optical Microscopy (POM)
Fourier Transform Infrared Spectroscopy (FTIR)
Differential Scanning Calorimetry (DSC)
Thermogravimetric Analysis (TGA)
Notched Izod Impact Test
Tensile Test
Flexural Test
Thermal Conductivity
Electrical Conductivity
14
16. 16
Skin-Core-Skin Structure of Injection Molded PET/PBT Blend
RESULTS AND DISCUSSIONS
The skin thickness was
425 µm. Beyond the skin,
birefringence due to fine
spherulites.
Amorphous PBT-PET
skin, non-birefringent
Spherulitical
crystallised blend
Amorphous skin
Crystallized PBT-PET core
17. DSC of The Skin-Core-Skin Structure of PET/PBT Blend Bar
• The nature of the skin in the 60/40 PET/PBT bar was intriguing, as it was
not clear whether it was an amorphous 60/40 PBT/PET, or whether it was
a layer of PET or PBT that had segregated and become frozen near the
cold mold, into an amorphous state.
• The skin is amorphous PET/PBT.
17
18. 18
Visual Appearance of Blends
PET PBT
PET/PBT
PET/PBT
The filament at the die exit of
the extruder is transparent
which indicate the miscibility
between PET and PBT in melt
state.
19. Morphological Characterization
Although PET and PBT crystallize separately, it is difficult to see their phases.
19
PET/PBT PET/PBT
Al micro platelet particles
Al nano spherical particles
20. Fracture Surfaces of Micro-platelets
20
• The ductile behavior of the matrix is shown in the neat blend as well
as in 3 % vol. composite.
• The fracture surface has a fibrillary appearance.
• Also at 3% vol., the Al particles are in flatwise direction.
3% vol.
PET/PBT blend
21. 21
Fracture Surfaces of Micro-platelets Composites
At higher concentration of Al flakes, the microstructure of the Al micro-
platelet composites shows the brittle behavior of the composites. The Al
particles plates were not pulled out of the blend matrix.
The flakes are lying parallel with each other and oriented to the
direction of the flow.
10% vol. 25% vol.
22. Fracture Surfaces of Nano- Spherical Composites
22
Al nano-spherical composites display a fibrillary break surface at 1% loading but
this changes at 5%. it is noticed that the presence of some local aggregates
increase with increasing Al.
PET/PBT 1% vol. 5% vol.
23. X-Ray Diffraction Analysis
23
The neat blend shows a wide peak at 2θ extending from 11.5 to 31.0o
showing the amorphous phase of neat PET/PBT blend and its composites.
The absence of crystalline peaks of PBT is due the skin-core structure of
PET/PBT blend, as explained.
24. FTIR CHARACTERIZATION
• The PET and PBT and their blend show a quite similar FTIR spectrum. FTIR
spectra of the blend does not suggest any chemical reactions occurred
between PET and PBT. No peak shifts were observed in the PET/PBT blends
either.
24
C=O
C=C
25. • Peaks intensity decreased with increasing Al content.
25
FTIR CHARACTERIZATION
• We can conclude that, PET and PBT did not undergo any transesterification
reactions and also platelet and spherical aluminum powder did not affect the
chemical structure of PET/PBT matrix.
26. Thermal Analysis: TGA Characterization
• No significant weight loss up to 355 oC.
• The onset of degradation of the composites shifts toward lower temperature with
increasing Al content, which is pronounced for both platelets and spherical
composites. Yet the end of degradation in most compositions shifts to higher
temperatures.
26
29. Mechanical Characterization
• The end use of engineering polymers depends on the mechanical properties.
• Three different mechanical tests were used to characterize the composites
29
32. 32
Tensile Strength
There was an increase in the tensile strength with the increase in the volume
fraction of micro Al powders. The tensile strength of nano spherical Al
particles filled PET/PBT composites decreased gradually with increasing filler
loading.
33. 33
Tensile Modulus
Incorporation of the al into the PET/PBT matrix leads to a gradual increase in
the stiffness of the composites. The tensile modulus of the al nano-spherical
composites increases with the addition of aluminum content. Al particles lead to
hindered molecular mobility of the PET/PBT chain segments.
35. 35
The analytical models predicted the same values and correlations that were in
logical agreement with the observed experimental conditions of the Al nano
composites. However, the theoretical models predicted the opposite
correlation with the experimental results of the Al micro composites.
Analytical Models for Prediction Tensile Strength
36. 36
Flexural Strength
An enhancement in the flexural strength values with increase in the volume
fraction ratio of platelet Al powders.
A decrease in the flexural strength was observed for Al nano-spherical
composites.
37. 37
Flexural Modulus
The flexural modulus of the flaky composites was noticeably higher than
that of the spherical composites. This is may be due the excellent adhesion
of the flaky particles with the polymer matrix as well as due to the
orientation of the flakes in the composites. Thus, increase the rigidity of the
polymer matrix.
38. 38
Strain at Maximum Stress
The strain at maximum stress values decrease with increasing volume
fraction of Al in the composites. Aluminum particles hinder the polymer
chain mobility and thereby reduce the ductility of the blend.
39. Thermal Conductivity
39
Thermally conductive composites are in
demand for heat dissipation and heat
management in electronic packaging and in
LED lighting assemblies.
The maximum volume fraction of 25 vol. %
showed the highest thermal conductivity of
0.561 W/mK which is about 56 % higher
compared to that of the neat blend.
40. Electrical Resistivity
40
The conductive polymer composites are interested because of the
composite combine the electrical characteristics of the metals and the
process and the mechanical properties of the polymer.
electrostatic and dissipative.
The percolation was reached
The volume resistivity for composites
does not record any considerable
changes at composition below 25% vol.
which are located in the insulating
region at value of 10^13 Ωcm which is
similar to that of the neat blend.
41. Conclusion
• The effect of incorporation of micro platelets and nano spherical particles of
aluminum in the PET/PBT blend prepared by melt compounding followed by
injection molding were studied.
• Single Tg for the blend indicates good miscibility between PET and PBT in the
amorphous phase. The transparent filament at the die exit of the extruder
indicate the miscibility between PET and PBT in melt state at the melt
temperature.
• PET/PBT blend has a skin-core-skin morphology where the skin consists of an
amorphous layer of the PET/PBT blend. The X- ray diffraction pattern of the
PET/PBT blend did not show any crystalline peaks due the amorphous skin of
the skin- core structure. 41
42. • Aluminum fillers particles are uniformly distributed in the PET/PBT matrix. The
Al micro-platelets seem to be parallel and oriented to the direction of the flow.
• There is no chemical interaction between PET and PBT nor between Al and
polymer matrix.
• The onset of degradation temperature of the composites shifts toward lower
temperature with increasing Al content. However, the Al particles extends the
degradation endpoint to higher temperatures.
• Al particles play a role of nucleating agents that increase the heterogeneous
crystalline sites in the amorphous region of the Al /PET/PBT composites.
42
Conclusion cont…
43. • The impact strength of Al micro-platelet PET/PBT composites increased
until it reached the highest value of 53.54 J/m which is about 58% higher
than that of the neat blend.
• The tensile strength of the Al nano-spherical composites decreased with
increasing Al content. This may be attributed to the weak interfacial
adhesion between nano-spherical Al and the PET/PBT matrix and also
the formation of aggregates. However, the platelet Al particles (flaky
shape) increased the tensile strength of the Al micro composites by about
22.5% compared to the neat blend.
• The flexural modulus of the Al micro-platelet composites showed a
significant and remarkable increase. The flexural modulus rose gradually
and reached to 5.66 GPa at highest Al loading of 25 vol. %.
43
Conclusion cont…
44. • The thermal conductivity results showed a gradual increase with the
increase in the volume fraction of the aluminum particles. An
enhancement of electrical conductivity by several orders
(corresponding to electrostatic charge dissipation) was obtained at
25 vol. % of the Al platelets.
• A thermally and electrically conductive plastic was obtained without
any deterioration of tensile strength and impact, using a relatively
cheap metal filler (Al) that doesn’t require any surface treatments to
ensure good adhesion.
44
Conclusion cont…
45. Recommendations
• Further investigations are needed to study crystallization process of both
PET and PBT as it occurs in their blend composition. This blend has a
skin-core-skin morphology and the process by which an entangled,
amorphous composition of two different chain species crystallize in
separate lattices is intriguing.
• Study the effect of the different shapes of Al particles e.g. fiber, dendrites,
etc. on the blend mechanical properties and their possible role in lowering
the filler threshold content to lower volume fractions to achieve good
thermal and electrical conductivity
45
