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properties of poly(ethylene terephthalate)/poly(ethylene naphthalate) blends. - characteristics of polyester

by:Cailong     2019-08-15
properties of poly(ethylene terephthalate)/poly(ethylene naphthalate) blends.  -  characteristics of polyester
By gathering (
Pet)(PET)
Aggregation and aggregation are the main ingredients (
Vinyl pen)(PEN)
When a few ingredients melt
Mix in a screw extruder with a different PET/PENcompound ratio.
The results of the tensile and bending tests reveal a good PET/PENcomposition dependence, indicating that the compatibility of blendsis is effective in the macro field.
Single transition of [in thermal test]T. sub. g]' [T. sub. m]and [T. sub. c](
Crystal temperature)
It was observed from DSC and single [respectively]T. sub. g]
Except for the mixture of 50/50, from DMA.
These results show that the compatibility problem has dropped to micron level.
In addition, the constant temperature DSC test analyzed with Avrami showed that the crystals of PET were significantly delayed when mixed with PEN.
The results of this study show that PEN is a promising additive that can improve the spinability of pet at high speeds.
Introduction to pet (PET)
It is a semi-crystalline polymer with excellent chemical resistance, thermal stability, fluidity and spinability.
Widely used in packaging, electrical, automotive, construction and other fields.
In the application of PET, the consumption of synthetic fiber is the largest.
In this field, it is highly desirable to learn more about or enhance its fibers.
Rotation behavior.
In particular, to save money, fiber producers have recently put a lot of effort into upgrading high-speed spinning processes.
However, the formation of the skin --
The core structure when rotating PETat at high speed is a serious problem, which often leads to broken filament. In a high-
During high speed rotation, the quenching time is too short to evenly transfer the quenching flow to the cross section of the entire fiber.
So the skin
Form of core structure]1-3].
A feasible way to solve this problem is to change the PET by mixing it with the second component to slow down its crystalline rate and create a thinner skin.
Perez and Zheng [4]
Add 3% nylon 6, 6 to ease the skincore effect.
However, this survey is primarily concerned with the non-compatibility of polyester/polyamide mixtures.
Since then, many works have been looking for polymers compatible with PET. Poly(
Ethylene-fei2, 6-dicarboxylate)
In this work, commonly referred to as PEN, it is used as a compatible mixing agent for PET.
Compared to PET, PEN has recently been widely regarded as a new generation of polyester fiber.
Teijin Co commercialised PEN for the first time nearly three years ago to produce resin and film.
Later, Shell Chemical and Asman chemical
Mass production started in 1993.
Since then, many studies have tried to understand the film application and crystal properties of PEN [5-9].
In addition, other investigators studied the spinning of PEN fiber [10-16].
PEN has a harder main chain compared to PET, which is thought to hinder the crystalline process.
In addition, the above-mentioned researchers speculate that ablend consisting of both polyester is more compatible than apoly!
Nylon system.
Similar to PEN, PET/PEN blend has received wide attention [1]18-21].
The related work mainly focuses on film or packaging applications and is published in the form of a patent or business report.
However, basic research on the properties of mixing is relatively lacking. Guo [22]
Recent compatibility PET/PENblends with high qualityFrequency solid-
State NMR detection.
This study confirmed that there would be no ester transfer reaction during the preparation of samples using a melt mixing.
However, in the same study, further nmr studies have shown that in the appropriate-
The pressing process without the help of the ester transfer.
This work thoroughly investigated the compatibility of PET blendedand with PEN.
The characterizing techniques covering the macro to micro fields include mechanical analysis such as tensile and bending tests, as well as thermal analysis such as DSC and DMA.
Therefore, the main purpose of this study is to investigate the feasibility of mixing pen pet to reduce the rate of PET crystal.
Two different polyester, PET, PEN, and PET/PEN melts were used for sample preparation in this study.
PET resin IV = 0.
64 provided by Far East Limited. (EASTLON, CH608).
Pen resin with IV = 0.
59 was purchased from Shell Chemical. (VITUF SXL 7).
The polymer pre-crystals and dries at 140 [before melting extrusion]degrees]
Maintain moisture levels below 100 ppm for 16 hours under vacuum conditions.
All mixing processes are carried out in a screw extruder that includes ascrew with a diameter of 4 cm, an ascrew with a L/d of 24, and a Maddock mixing head bracket at the front.
The average stay time for extrusion is about 8 minutes.
The extrusion temperature is between 285 [degrees]
Cfor pure Pet Delivery 320 【degrees]C for pure PEN.
The mixed sample is then formed by an injection mold to form a variety of standard shapes for the following tests: Tensile Test (ASTM-D638); flexural test(ASTM-D790);
And DMA temperature scanning (20 X 11. 76 X 3. 3mm).
As mentioned above, the sample size and test procedures for tensile and bending strength follow the ASTM instructions.
A DSCmelting study of various PET/PEN mixtures was carried out on DuPont 2000 thermal analyzer.
Heating and cooling rates applied in thermal scanning are 10 [degrees]/min.
In addition, in order to analyze the crystalline rate of various mixtures, constant temperature scanning tests were performed on samples heated to 200 [degrees]C.
More than 270 samples [degrees]
C then quenching to 200 [degrees]
C in 5 seconds.
Then keep the constant temperature until the hotline is completely flat.
Finally, the temperature of the glass [T. sub. g]
Thermal analysis of dynamic materials (DMA)(TA 4000-DMA. 983).
Experiments were carried out in a resonant mode with a displacement amplitude of 0. 2mm.
Temperature scan range from-120[degrees]
C to soft point 5 [degrees]
C/min heating rate.
Results and Discussion Figure 1 shows the dependence of the tensile strength and elongation values on the ratio of PEN mixing.
The tensile strength is linearly proportional to the mixing ratio of PEN.
Since the variation in elongation is often contrary to the results of stretching, the inverse nature of the pen composition is expected.
Dispersion phase greater than 100 [micro]
M becomes a weakness resulting in much worse mechanical performance than the rest of the parent component [s]17].
From a macro point of view, the melting mixture of PET and PEN is at least compatible.
Figure 2 shows the bending strength and bending elongation of the pet/PEN mixture, respectively.
In the three-point bending test, the bending strength reaches the maximum load, while the bending elongation reaches the corresponding tensile ratio.
Next, the lamination phenomenon is studied by bending test and whether phase separation occurs.
The lamination is largely attributed to the deformation of the dispersed phase along the flow direction.
It is worth noting that for incompatible mixtures, especially those composed of arigid skeleton components such as liquid crystal polymers [], stratification occurs23].
In addition, the lamination produces a higher tensile strength, as these phase orientation along the direction of the stretching can provide a force effect.
However, if the bending force is applied vertically on it compared to the tensile test, thespecimen is easy to strip.
Therefore, a lower bending strength was obtained.
Figure 2 also shows that the larger the number of pens in the composition, the greater the bending strength and bending elongation.
In conclusion, the results of tensile and bending tests show that PET/PEN has good compatibility in the macro field (About 10-100 [micro]m)
Can be achieved.
It is well known that the compatibility of most polymer mixtures can be accurately detected through complex thermal analysis techniques to observe changes in transition temperatures.
In some cases, Micro
About the stage [10. sup. -2][micro]
M or less detected using DSC [17, 24-26].
Figure 3 shows the DSC heating traces of PET, PEN and their mixture.
Single melting peak [T. sub. m]
It was also observed that the composition of the mixture was different.
Hot melt peaks of PET and PEN are located at 254 [degrees]C and 265[degrees]C,respectively.
However, the position of the peak in the mixture drops to an area below the melting temperature of pure PET.
Change [T. sub. m]
Values outside the melting area of the parent element can be explained as follows.
The two polymers must be completely mixed and tightly wound together.
Especially in cases involving multiple rings, entanglement may effectively inhibit the crystalline behavior of these two components.
This result inhibits the mixture of reduced crystalline rate, reduced crystalline degree, and poor crystalline structure.
Therefore, the melting temperature will be significantly reduced.
While attempting to clarify the above explanation, Figure 4 contains the cooling traces of the DSC heat map for various PET/PENblends.
Single Crystal Peaks of various PET/PENblends were observed.
This finding also shows that crystals cannot be detected after the PEN amount is increased to 30%.
This result shows that the cooling time of the application (10[degrees]C/min)
Pet chains are too short to crystallize because they are entangled with a small part of the pen chain.
This slow effect of pen on pets is currently X-Ray diffraction
Preliminary results show that the crystal process of a pure pen is much slower than that of a pure pet when rapid quenching is applied.
Therefore, the addition of PEN as an amino group or part of the PET matrix can be considered as a crystalline inhibitor.
Detailed results on this point will be published separately. For semi-
A crystalline polymer mixture, a single melting point, or a single crystalline point indicates the presence of a new co-
Crystal structure or two unresolved peaks. Notably,co-
Crystals rarely occur in polymer mixtures, only in some polyethylene systems or poly (
Fang ether ketone)systems [28, 29].
Many surveys, by contrast, confirm that most
Crystal polymer mixtures including polyester systems such as PET/tb mixtures [27]
It's a separate Crystal.
Future studies, including X-ray, infrared and light scattering checks, should attempt to thoroughly explain the crystal structure of the PET/PEN system.
Occasionally ,[T. sub. g]
Called a secondary transition may not appear clearly in the DSC thermal diagram, whereas it can be double checked by a more sensitive DMA test in figure 15.
Change of tan ([sigma])
The temperature of the PET/PEN mixture is also included in the figure.
Peak list [T. sub. g]
Indicates full compatibility in both amorphous domains except for the 50/50 mixture.
Depending on the thermal results, it is possible to predict a compatible domain of sub-micron or smaller.
A constant temperature test was also performed to further understand the crystalline behavior of PET in the mixture.
These results are shown in figure 6.
Pure PEN resin contains two discharge peaks, compared to a single discharge peak of pet.
Besides, PEN's twins
The peak makes all the mixture behave similarly.
Although it is not clear, this behavior shows that
The crystal of the mixture must have only one single peak, which is impossible.
It is worth noting that 50/50 of the mixture has a very long Crystal time.
This finding again shows that in 50/50 mixtures, it takes more time for the polymer chains of these two components to separate from each other to form their own crystals.
This is also recognized as the lowest [T. sub. m]
It is more expensive to observe in a mixture of 50/50.
In order to further analyze the rate of crystal formation, a macro analysis was performed based on the empirical avrami equation, as shown below. X = 1 -exp (-k x [t. sup. n])(1)
Where's the time-
Depends on the crystal of the volume fraction.
K is the rate constant of Avrami and n is the shape parameter.
To obtain a more convenient form, record twice and rearrange the display Ln (-Ln (l -X))
= Ln k n x Ln (t)(2)
According to the picture.
Figure 6 and Eq 27 plots Ln (-Ln (1 -X))versusLn (t). In Fig.
7, Ln k is intercept, n is the slope of the mixture.
Table 1 lists the values of k and n.
Avrami analysis is a very effective method for determining the crystal rate.
The rate constants and shape factors obtained here can be considered as the overall value of the mixture where PETis is the main component.
That is, the results of this work help to evaluate the effect of adding PEN on the delay of thermal crystals of pet.
The data listed in Table 1 clearly indicate that by increasing the content of the additive PEN, the re-Crystal rate k of pet can be postponed to 1 or 2 orders of magnitude.
With respect to the shape factor n, minor changes indicate that the crystal shape changes of the mixture are negligible.
Before we can verify that PEN is a sufficient additive to enhance the textile properties of pets, another problem must be solved.
In addition to the "hot-shaped nucleus", the crystalline mechanism also includes the "stress-induced nucleus ". " In high-
With high speed rotation, the molecular chain is easily stretched by high winding tension.
Therefore, the "stress-induced" factor is more prominent than the "heat" factor.
Although these two mechanisms are interrelated, the DSC measurements applied in this work can only detect thermal crystals.
"Stress-induced crystals" can only be thoroughly understood by implementing a rotating process for various winding speeds.
This allows us to observe the "stress" effect.
This work is currently going on in our lab.
Conclusion The mechanical properties and thermal properties of PET/PEN mixture were studied.
Based on these results, we can draw the following conclusions. 1.
Tensile and bending tests show a good combination dependence on various mechanical properties.
This finding shows the effective compatibility of the macro domain (10 to 100[micro]m)Can be achieved. 2.
DSC and DMA tests show a good composition dependence on [T. sub. g]
Except for the mixture of 50/50. A single [T. sub. m]and a single[T. sub. c]
Also observed.
These results show that the compatibility of the mixture of both amorphous and crystalline phases is effective at the sub-micron level.
Our results further show that the addition of PEN as a secondary component can significantly reduce the degree of epet and [T. sub. m]. 3.
The constant temperature DSC test, as well as Avrami analysis, showed that the crystalline rate could be significantly slowed down if pet was mixed with a small amount of PEN.
In general, our results confirm that PEN is a promising additive that can improve the performance of PET at high speed rotation.
Future work should look more closely at the spinability of the mixture.
Thanks to the author for the financial support provided by the National Scientific Commission of China for this studyNSC 86-2216-027-002 references (1. )H. R. E.
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