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biaxial orientation in lldpe films: comparison of infrared spectroscopy, x-ray pole figures, and birefringence techniques.

by:Top-In     2020-07-28
Semi-crystalline olefin films represent a large part of the plastic industry.
The most widely used two-way process of the film is the standard film blowing process (
For all kinds of polyethylene (PE)
Double bubble process (
For polypropylene and linear low
Densitypolyethylene, llannan)
Two-way orientation or leasing of cast film (
High Density Polyethylene, high density polyethylene and polypropylene).
All these processes give a certain orientation to the polymer, which improves many properties of the polymer [1-5]
Especially mechanical, shock, blocking and optics.
Two-way orientation has additional advantages that allow two-way enhancement.
Llldpe is used in both blow film and two-way film (double bubble)
Because of its wide range of applications.
The crystal structure and various phase orientation developed in the film process have an important influence on its performance.
Different techniques can be used to determine the structure and direction of the film.
The microscope gives a complete picture of the crystal form (
Flaky, spherical, etc. ), X-
The Ray pole diagram gives details of the crystal phase orientation.
Infrared spectrum (FTIR)
Allow the determination of crystal and non-crystal phases and specific orientation factors for cross-and high-order conformations and combinations [1]6]
, Provided that their transition moment angles are known.
Finally, the average total orientation is the double refraction.
For the special case of PE, FTIRallows can also determine the direction of the crystal axis [6-18].
However, the accuracy and precise significance of the different orientation factors identified from these techniques is established, although some of the past studies have partially addressed these issues and their relationship to [structure and nature]7-16].
In a recent paper19]
We solved the problem.
Density Polyethylene (HDPE)
In response, some differences were observed and discussed.
However, since higher crystal content and typical structure can be developed in high density polyethylene (
Core structure)
Linear low density polyethylene in contrast (
Structure of random plate layer)[20]
, These results cannot be transferred to llldpe.
Stan [in his fifties]7-9]
The comparison of infrared and X-infrared results is processed.
X-ray diffraction of polyethylene and theoretical double refraction and comparison with a simple hypothetical case [1]7].
At the age of 60, Read and Stein [10]
Some quantitative comparisons are made on the single axis orientation; however,the X-
No ray results were made in the same lab.
Even with this fact, significant differences have been observed between the FTIRresults results of crystal-
Axis and axis obtained from X
Low directional level ray
Some of the observed differences are attributed to potential differences in film and experimental errors. Desper [11]
On the other hand, the use of X-
Rays, double refraction, and infrared spectra.
However, in his infrared spectrum measurement, he did not use the tilt technique and therefore did not contribute from the thickness direction to correctly compare the orientation factor.
Recently, Kissin [17]
A method for determining the two-way orientation factor of high density polyethylene film with specific structure is developed (row structure)
Two FTIRspectra are used without the need to tilt the film to determine the third spectrum [6].
He compared the results of this method with the WAXD results of two-way oriented high density polyethylene film with row structure and found that based on white-
Two-way orientation factor.
However, when Hermann\'s orientation factor is used to determine the orientation factor, the IR and X-
Ray diffraction, which may be due to compensation between two independent angles involving white
Spruiell factors (
These calculations are not done in the paper). Krishnaswamy [18]
The method of Kissin was modified and extended to the LLDPE blowing film, but no systematic comparison was reported with the infrared tilting technique or the WAXD results.
To clarify the differences observed in the above literature, as well as to track our comparison of infrared spectrum and X-
As a result of Ray-on-blowing film orientation factors, we have conducted extensive and systematic research on different PE with different forms and histories.
One-way orientation, two-way orientation and blowing film of high-density polyethylene, llannan and low-density polyethylene were characterized by X-
X-ray, infrared, and double refraction.
The results of the Hermann double orientation factor obtained from different techniques are compared and discussed.
Also compared with the methods of Kissin and krishnaswamy mentioned above.
The first paper is about the case of [high density polyethylene]19]
The second paper discusses the case of llannan.
The melting index of LLDPE film resin was 1 for the film blowing experiment.
0 and density 0. 918, was used.
The films were made using the extrusion line of Brampton engineering.
Extrusion temperature distribution range is 160-200 [degrees]C.
2 pull-down ratios (DDR for 23 and 12)
The explosion ratio of the thickness is about 25 [2]micro]m were used.
The height of the frost line is about 70 cm (
The diameter of the mold is 10 cm, and the gap between the molds used is 1. 1 mm).
For the tensile sample, the initial sheet of the same llannan as above (0. 5 to 1mm thick)
The film was prepared by flow extension extrusion method.
Stretching was done on a two-way stretcher at the brürkner laboratory.
The conditions are as follows: tensile rate 10% [s. sup. -1]
Initial sample size 10x10 [simultaneous deformation modecm. sup. 2]
, Tensile temperature of 120 [degrees]C.
The final tensile ratio is as follows: the tensile ratio of one-way stretching to 4 times (
Samples that are not clamped horizontally [TD])
, Pull down to 4x1 in constant width mode (
Samples clamped with TD)
, And stretch to adraw in both directions in a 4x4 ratio.
In this way, it is expected that the degree of orientation in TD will increase from sampleto, which stretches in a one-way, provided that the initial film is stretched vertically.
In the case of a one-way tensile sample, the measuring part of the film is cut at the center of the film.
Scanning electron microscopy using field emission (FE-SEM, Hitachi S-4700)
Minimum coating with film and surface.
The global bidirectional orientation factor was determined using birefringence.
In The Machine, the absolute value of the refraction
Normal and Lateral
The normal plane is through more than an accident.
Wavelength dual-beam and diode array assembly, with in-
Software developed by House
Details of this technology can be found elsewhere in [21, 22].
The two-way directional factor used in this study is the directional factor of Hemans :[f. sub. jM], [f. sub. jT], and [f. sub. jN]
In The Machine, the horizontal and normal directions of the shaft j are
The relationship between these orientation factors and other measurable quantities can be developed, such as double refraction.
Assuming that the threshold value of polyethylene is [DELTA][degrees]= [n. sub. c]-([n. sub. a]+ [n. sub. b])/2 (about 0. 058)and [delta][degrees]= [n. sub. a]-[n. sub. b], (about -0. 003)where [n. sub. a], [n. sub. b], and [n. sub. c]
The refraction index of the crystal along the axes a, B and c can get the following equation of the [crystal phase]6]: ([DELTA][n. sub. MN])[. sub. C]= 2[DELTA][degrees]([f. sub. cM]-[f. sub. cN])/3 + [delta][degrees]([f. sub. aM]-[f. sub. aN]-[f. sub. bM]+[f. sub. bN])/3 (1)([DELTA][n. sub. TN])[. sub. C]= 2[DELTA][degrees]([f. sub. cT]-[f. sub. cN])/3 + [delta][degrees]([f. sub. aT]-[f. sub. aN]-[f. sub. bT]+[f. sub. bN])/3. (2)
The total refraction is due to the crystal and the deformed ball in addition to the formal refraction (
Negligible). If [phi]
We can write this :[DELTA][n. sub. MN]= [phi]x([DELTA][n. sub. MN])[. sub. C]+ (1 -[phi])x([DELTA][n. sub. MN])[. sub. A]+ [DELTA][n. sub. form]. (3)
The A and C indices represent amorphous and crystalline phases.
It is then possible to determine the crystal phase refractive index from the crystal axis orientation and amorphous phase refractive index by using the above method, by subtracting the crystal contribution from the total refractive index
The equation mentioned
In general, the contribution of the and B axis orientations to the polarization of the crystal is lower than that of the c axis, because of the inherent polarization difference, which is assumed to be negligible here.
This will result in the following simplified equations :([DELTA][n. sub. MN])[. sub. C]= 2[DELTA][degrees](2[f. sub. cM]+[f. sub. cT])/3. (4)
From width-the crystal axis orientation factor is determinedangle X-
Ray diffraction pole diagram ()110)and (200)
Reflection with background and absorption correction, unless otherwise stated, although (020)
Reflection is also measured. 19].
The device used is Bruker axs x-
Light angle meter with Hi-STARtwo-
Size area detector.
The generator is set at 40 kV and 40 mA copper [K. sub. [alpha]]radiation ([lambda]= 1. 542[Angstrom])
It is selected using graphite crystal monochrome meter.
The Sampleto detector is fixed at a distance of 8 cm.
In order to obtain sufficient accuracy within a reasonable period of time, the film sample is stacked to a thickness of about 3mm.
In addition to the orientation factor of the non-crystalline phase, the crystal orientation factor was determined by using the infrared spectrum of the inclined film technology to obtain the Normal Spectrum (film thickness)direction.
The measurements were made on the Nicolet 17sx infrared ata resolution of 2 [cm. sup. -1]
Scan 128 times in total.
Polarization of the beam using a selenium-zinc wire grid bias mirror from the spectrum-Tech.
Details about this approach have been reported [6, 19, 20].
Judging from the repeated measurements and samples in the above experimental methods and calculations, the accuracy estimate of the guiding factor values reported here is about 0. 05.
As a result, the number table presented here shows the typical behavior of some movies. For simplicity and clarity, all movies are not systematically displayed.
These issues are also not discussed in this section, but in the following section, after the various calculations shown in the table. Typical X-
The results of the Ray pole diagram are (110), (200), and (020)
Reflection is shown in Figure 1.
They are 1a and lb of blow film and two-way stretch film, respectively.
For infrared spectra, typical results obtained in the spectral regions of interest in all directions (
Machine MD, transverse TD and normal ND)
As shown in the figure.
2. The result of the decomposition program.
The typical film morphology obtained from SEM is shown in the figure
For blowing film and stretch film.
It is clear that the plate-layer nuclear arrangement structure is not obtained for the blown film.
Instead, as shown in the figure.
3a and 3b, sheet and/or spherical structures with random orientation were obtained.
Detailed quantitative results of various orientation factors were determined from the respective polar maps, infrared spectroscopy and measured refractive index of all films.
Table 1 summarizes these results
For blow film and stretch film, it will be discussed in detail below.
Let\'s first compare the crystal axis orientation determined by the infrared spectrum (
Use 730 and 719 [cm. sup. -1]
For crystal axes a and B, respectively)and X-
Ray pole diagram of two blown films using two different DDS of 12 and 23 with thickness of 50 and 25 [micro]
M is listed in Table 1.
The results were consistent in quality, but significant differences were observed in quantity.
In fact, for crystal-
Axis, the value of the orientation factor in theMD from these two technologies confirms that it faces the MD direction of the two films, and the value of the infrared spectrum is higher, especially from 730 [1 [cm. sup. -1]vibrations.
[Reading and Stan10]
This difference between 730 [has been reported]cm. sup. -1]and X-
A long time ago, the ray results of the low-level orientation of the one-way stretch film.
They attribute it to potential overlap with 720 [cm. sup. -1]
Possible uncertainty of X-
Ray results of the film.
We do agree with the first argument, as shown in the figure.
2, it is very possible to overlap with the potential of the amorphous phase band, especially if the peak is not strong, and it is also possible to saturation the thick film (
As discussed elsewhere19]
For theMD spectrum)
This may be the case of the MD spectrum of 50 [micro]m thick film.
The second argument about X
The ray results on the film are accurate, and our results are obtained on stacked films with a total thickness of about 3mm, and we believe that this error is small.
We believe that the argument about peak saturation is not very important for llannan films (
Differences in IR and X-ray orientation compared to high density polyethylene
Ray is about 0.
50 [3] or moremicro]m films)
But another argument about the potential overlap of peaks is valid for all films.
Another aspect different from the high density polyethylene film is the crystalline content, which is almost twice as high as that of llannan.
This may have an effect on peak saturation in the infrared spectrum. [
Figure 1 slightly][
Figure 2:
TD orientation factor for-
Shaft, due to thea-
The axis is weaker than MD, and the value is usually lower than from X-
Although the infrared spectrum still overestimates the direction, the light does not matter.
This is most likely due to the overlap between this peak and the non-Crystal Peak, partially with the B-Peakaxis. For the b-
Axis, representing TD-for the value obtained for the orientation factor-
The ND plane of all films has a more random distribution in the TD direction.
For the MDorientation factor, the IR spectrum is again overestimated with X-
Ray results, but than-axis.
Infrared spectrum and X-
For the thickness of the two films, the Rays are similar, indicating that it is likely that there is no saturation in the measurement.
Infrared spectrum and X-
Although the ray results are small, they may be due to deformation and/or-axis peaks.
Table 2 shows the results of various corrections or calculations on X-
X-ray results of 25 [micro]
M movie and use 1464-1471 [cm. sup. -1]
The spectral band of the B axis and the axis. For X-
Ray results, can clearly see the background correction to-
Axis results, while absorption correction affects both axis a and axis B results.
For the B axis, it goes directly from (020)
Reflection or from combination (200)and (110)
Reflection does produce different results.
Because of the weak strength (020)
Than (110)reflection (
Also shown in the case of [high density polyethylene]19])
It is considered that the calculated value of the B axis is from (200)and (110)
Reflection is more consistent and accurate [19].
For infrared spectrum results from 1464 to 1471 [cm. sup. -1]
The spectral region, interestingly, these results are related to the 719-730 [cm. sup. -1]
Region, which is certainly due to the vibration saturation of this spectral region.
In fact, the strength of these bands is about 719-730 [cm. sup. -1]
The area of most PE samples we have studied. [
Figure 3 slightly]
Table 3 gives the results of the global and amorphous phase orientation of the blown film.
The global orientation is determined by the refractive index and combined with the infrared spectrum and X-
Ray technology and crystal content, they are used to calculate the amorphous phase orientation and compare the results with those obtained from various infrared bands related to the amorphous phase [1]10, 11].
FTIRband 722 【cm. sup. -1]
Associated with the CH2 swing mode of the amorphoustrans sequence of 4 or more sequences, 1303 [cm. sup. -1]to C[H. sub. 2]
The swing of the GTG conformations, which is asymmetric relative to the center of the cross bond, is 1368 similar to 1303, but symmetrical relative to the center of the cross bond.
We first note that all the determined values of the amorphous phase orientation of the blown film are small (
Generally less than 0. 1).
Infrared spectrum results of 25 [micro]
The m of the three bands (
722, 1303 and 1368)
It is shown that the results of amorphous are roughly the same, as reported by Readand Stein [10].
These results are also comparable (
The experimental error is within 0. 05)
With those by refractive index and infrared or X-
The light determines the crystal orientation factor.
They all show the same trend of slight orientation on the machine --
The horizontal plane of the amorphous segment is similar to the overall orientation of the llannan chain.
For films with one-way and two-way orientation, the results of different crystal orientation factors are given in Table 4.
Under normal circumstances ,(020)
As shown in the figure, the reflection strength is very weak. 1b. The X-
Use these two procedures to determine the ray results of these stretched films :(1)a-axis from (200), b-axis from (020), andc-
From two axes; or (2)a-axis from (200), b-
Wheelbase combination (110), and (200)and c-
From two axes.
Some differences can be observed in the table between the two results, but less than the above blown film and high density polyethylene film [19].
In addition to the above observation on the better accuracy of the results of the baxis, from (200)and (110)
Reflection, if a person looks at the Polar Picture of the picture1b of the (020)
Reflection, it can be observed that it is mainly located in the TD direction, and there is some non-negligible presence in the theND direction (
Small gray line in the center)
, In the calculated B-axis, from (200)and (110)
Instead of directly from (020).
In the rest of this article, only from (200)and (110)are used.
In terms of crystal axis orientation, Crystal-
Axisorientation is basically in TD-
ND plane of one-way and two-way oriented film. The b-
Axis in TD-
There are ND planes in both cases.
For the c-axis, both techniques indicate that it is located in the MDdirection of a one-way directional film, which is expected.
For bidirectional orientation, the c-axis is oriented mainly in MD, in TD, and in ND.
For samples of this isoaxial stretch, one would expect c-
Axis in MD and TD.
This difference can be attributed to the initial non-isosexual tensile-free film, which will also be discussed in conjunction with the results of the refraction. Comparing X-
The ray determined the orientation function with those from the infrared spectrum, and again observed that the-axis orientation in MD from FTIRis was overestimated, but was observed more than that of the blowllldpe film and HDPE film. 19].
It should also be noted that the infrared spectrum underestimated the B-axis orientation, for example, calculating the positive MD and negative ND orientation from the infrared spectrum, which is wrong, from X-
Lightning Rod chart
For a one-way oriented film, the infrared transmission spectrum is saturated due to its large thickness, so the infrared data cannot be collected.
Amorphous orientation, total refractive index and corresponding global orientation and calculated amorphous orientation results measured by infrared spectroscopy (
Starting from X-, combining crystal axis orientation with crystal axis orientationray or FTIR)
As shown in Table 5.
The preliminary observations from the double refraction show that the initial film is not of the same sex.
In fact, the stretch film shows a two-way Box (non-zero [DELTA][n. sub. MT]
Samples for two-way stretching)
Different values from [DELTA][n. sub. MN]and [DELTA][n. sub. MT]
For one-way stretching.
Results obtained from infrared spectrum 722 [for non-crystalline phase]cm. sup. -1]
The vibration is comparable to the combination of double refraction and X-
Some differences were observed for TD directions, Ray results, especially MDorientation.
The results of the calculation of the crystal axis orientation determined by the refraction and infrared spectra are completely different from the two. In addition, it is confirmed that the infrared spectra overestimate the crystal axis orientation, especially the axis.
Finally, as mentioned in the introduction, a simplified FTIRprocedure for polyethylene film with row structure [s] has been proposed in the literature without the use of tilt technology17, 18]
Suitable for linear low density polyethylene (llldpe )[18].
Details of the program can be found in the references. 17 and 18.
We showed it in our previous research. 19]
This method is effective for continuous HDPE film
Nuclear form.
Our purpose here is to evaluate the effectiveness of this method for llonomia films.
As we all know, LLDPEfilms show the random plate layer structure as shown in the figure in most cases
3a and 3b and other studies12, 18, 20].
The simplified procedure is compared to the complete infrared method using tilt technology.
Both the area under the peak and the amplitude of vibration are used for infrared spectrum calculation and are related to X-
X-ray diffraction results of crystal axis orientation.
Table 6 shows the results of a blown film with a DDR of 12.
Infrared spectrum results are very different from X-
As already discussed above, the ray diffraction and overestimation of the orientation factor.
For infrared results, it can be clearly seen that the twoFTIR program gives significantly different results, and the simplified method gives unreasonable values, especially for the direction of caxis, which is well known, many studies on the filmsfrom blown by llldpe [negligible]12, 18, 20].
Within the experimental error range, the calculation using the vibration region or amplitude is similar.
This result, and the results previously obtained on HDPE [19]
The proposed simplified method is emphasized-
The nuclear structure exists and is strictly consistent with the assumptions of the method.
In addition, one should realize that the result is different from x-Ray diffraction
In conclusion, when determining the two-way orientation factors of ldpes using different techniques, care should be taken about their interpretation.
The infrared spectrum may be over-valued.
Axis direction;
The breakdown of different contributions can be difficult.
In the infrared spectral results, the determination of the orientation of the purple crystal ball may be significantly affected by peaksoverrap. Blown films (
Low direction)
Affected by these differences is greater than the stretch film (
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