Method and a device for measuring a glass transition temperature and a degree of crystallinity of a polymer

Abstract

Provided are a method of and a device for measuring a glass transition temperature and a degree of crystallinity of a polymer. According to the measurement method and the device of one exemplary embodiment of the present invention, a glass transition temperature and a degree of crystallinity may be measured easily, rapidly, and accurately in a field other than a laboratory, and fast and accurate conversion is possible for various measurement conditions such as temperature, frequency, etc.

Claims

1. A method of measuring a glass transition temperature of a polymer, the method comprising the steps of: A) (a1) colliding a collision sphere with a polymer specimen by dropping the collision sphere onto the polymer specimen from a predetermined drop height (H.sub.0); (a2) measuring a maximum bounce height (H.sub.1) of the collision sphere bounced by a resilience after colliding with the polymer specimen, and calculating a ratio (H ratio, H.sub.1/H.sub.0) of the maximum bounce height to the drop height; B) measuring the H ratio according to each temperature by repeating the steps of a1 and a2 while varying the temperature; and C) work calculating the glass transition temperature from the measured H ratio according to each temperature.

2. The method of claim 1, wherein the step C) includes the step of (c1) examining a temperature (T) at a point where the H ratio has a local minimum value, thereby estimating the temperature T as the glass transition temperature.

3. The method of claim 2, further comprising the step c2 of correcting the T value obtained in (c1).

4. The method of claim 3, wherein in the step c2, the glass transition temperature value is obtained by correcting the T value by a parallel movement model according to the time-temperature superposition principle.

5. The method of claim 3, wherein the step c2 of correcting includes the steps of: calculating a collision time (s, second) between the collision sphere and the polymer specimen in the step a1; calculating a collision frequency (f1, Hz) from the collision time (s); and calculating a correction factor value (Cf) by substituting a frequency (f0, Hz) in a standard method of measuring a glass transition temperature and the above collision frequency (f1) into the following Equation 1: $\begin{array}{cc}{C}_f=\log \frac{f_0}{f_1}& \left[\mathrm{Equation}1\right]\end{array}$ in Equation 1, Cf represents a correction factor value, f0 represents a frequency (Hz) used in a standard method of measuring a glass transition temperature of a polymer, and f1 represents a collision frequency (Hz) obtained from a collision time (s, second) between a collision sphere and a polymer specimen.

6. The method of claim 5, comprising the step of obtaining the glass transition temperature by the following Equation 2: $\begin{array}{cc}{T}_0=T+\frac{C_2{C}_f}{C_1+C_f}& \left[\mathrm{Equation}2\right]\end{array}$ in Equation 2, T0 represents a glass transition temperature value of a polymer resin to be obtained, T represents a temperature at a point where the H ratio has a local minimum value, Cf represents the correction factor value obtained by Equation 1 of claim 5, and C1 and C2 represent each constant value determined according to the type of the polymer resin.

7. A device for measuring physical properties of a polymer, the device comprising: a dropping part 100 for dropping a collision sphere; a collision part 200 for generating a collision between the collision sphere and a polymer specimen; a collision time-measuring part for measuring the collision time of the collision sphere and the polymer specimen; and a height-measuring part 300 for measuring a drop height (H0) of the collision sphere and a maximum bounce height (H1) of the collision sphere bounced by a resilience after colliding with the polymer specimen.

8. The method of claim 1, wherein the step C) includes the steps of (c3) obtaining a temperature-H ratio curve from the measurement value; and (c4) examining a temperature at which the H ratio value starts to most rapidly decrease on the temperature-H ratio curve, thereby estimating the temperature as the glass transition temperature.

9. The method of claim 8, wherein the step c4 includes the steps of calculating an instantaneous rate of change (a first rate of change) of the H ratio according to temperature; calculating an instantaneous rate of change (a second rate of change) of the instantaneous rate of change of the H ratio according to temperature; and examining a temperature at which the second rate of change has a minimum value on the temperature-H ratio curve, thereby estimating the temperature as the glass transition temperature.

10. The method of claim 8, wherein the step c4 includes the steps of calculating an instantaneous rate of change (a first rate of change) of the H ratio according to temperature; calculating an instantaneous rate of change (a second rate of change) of the instantaneous rate of change of the H ratio according to temperature; obtaining a tangent line (a first tangent line) in a first temperature range in which the first rate of change is smaller than 0 and the second rate of change is 0 on the temperature-H ratio curve; obtaining a tangent line (a second tangent line) in a second temperature range in which the first rate of change is smaller than 0 and the second rate of change is 0 on the temperature-H ratio curve; and estimating, as the glass transition temperature, a temperature at the intersection of the first tangent line and the second tangent line.

11. The method of claim 8, wherein the device of claim 7 is used.

12. The method of claim 1, wherein the polymer specimen is in the form of a sheet.

13. The method of claim 1, wherein a thickness of the polymer specimen is 10 nm or more.

14. The method of claim 1, wherein a density of the polymer specimen is 0.01 g/cm3 to 2 g/cm3.

15. The method of claim 1, wherein the polymer specimen includes one or more polymer resins selected from the group consisting of polyolefin-based, polyimide-based, polystyrene-based, polyvinyl-based, polylactide-based, silicone rubber-based, polycarbonate-based, polyacrylonitrile-based, polyacrylic-based, cellulose-based, polyester-based, polyimide-based, polyacetal-based, fluorine-based, polysulfone-based, and polyketone-based polymers, and copolymers thereof.

16. The method of claim 1, wherein a ratio of the diameter of the collision sphere to the thickness of the polymer specimen is 1 or more.

17. The method of claim 1, wherein the collision sphere has a coefficient of restitution of 0.4 to 1.

18. The method of claim 2, wherein the device of claim 7 is used.

19. The device of claim 18, further comprising a temperature controller 400 for controlling the temperature of the target polymer specimen.

20. A method of measuring a degree of crystallinity of a polymer, the method comprising the steps of: A) (a1) colliding a collision sphere with a polymer specimen by dropping the collision sphere onto the polymer specimen from a predetermined drop height (H0); (a2) measuring a maximum bounce height (H1) of the collision sphere bounced by a resilience after colliding with the polymer specimen, and calculating a ratio (H ratio, H1/H0) of the maximum bounce height to the drop height; B) measuring the H ratio according to each temperature by repeating the steps of a1 and a2 while varying the temperature; and C) work calculating a local minimum value from the H ratio measurement value according to each temperature.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 shows a schematic illustration of a method of measuring physical properties of a polymer according to an exemplary embodiment of the present invention over time;

(2) FIG. 2 shows a schematic illustration of a device for measuring physical properties of a polymer according to an exemplary embodiment of the present invention; and

(3) FIGS. 3 to 10 show a graph summarizing the measurement results according to the method of measuring physical properties of a polymer according to an exemplary embodiment of the present invention.

MODE FOR INVENTION

(4) Hereinafter, the actions and effects of the present invention will be described in more detail with reference to the specific exemplary examples of the present invention. However, these exemplary examples are for illustrative purposes only, and the scope of the present invention is not intended to be limited thereby.

(5) As a polymer resin specimen, polylactic acid (PLA) was prepared in the form of a film with a thickness of 1 mm (amorphous PLA including L-PLA of about 88 wt %˜90 wt % and D-PLA of about 10 wt %˜12 wt %)

(6) The polylactic acid has a glass transition temperature of about 58.2° C., as measured by a DMA method (frequency: 0.05 Hz).

(7) The polylactic acid specimen was fixed to a collision part, a collision sphere was dropped thereon from a predetermined height (H.sub.0), a bounce height (H.sub.1) of the collision sphere bounced after colliding with the polymer specimen was measured, and a ratio (H.sub.1/H.sub.0) was calculated.

(8) As the collision sphere, a sphere made of non-magnetic stainless steel, with a diameter of 12.7 mm, 6.3 mm, and 3.2 mm, respectively, was used. (SUS304)

(9) The collision experiment was repeated under various temperature conditions from about 20° C. to about 180° C., and the measurement was carried out.

(10) The measurement results are shown in FIG. 3.

(11) FIG. 3 shows a graph summarizing the measurement results according to a method of measuring a glass transition temperature of a polymer according to an exemplary embodiment of the present invention.

(12) By analyzing the graph of FIG. 3, it was determined that a local minimum value of the measured temperature, i.e., a glass transition temperature of the polymer was about 80.5° C.

(13) This difference between the determined value and the glass transition temperature previously obtained is attributed to the difference in the measurement frequency, as described above, and correction was performed by the following method.

(14) First, the collision time in the collision experiment carried out at about 80.5° C. was about 112.5*10.sup.−6 seconds.

(15) The measurement frequency of the present invention calculated therefrom is about 8888 Hz, and thus, C.sub.f value is calculated as −5.25.

(16) $\begin{array}{cc}{C}_f=\log \frac{f_0}{f_1}& \left[\mathrm{Equation}1\right]\end{array}$

(17) This value was substituted into Equation 2.

(18) $\begin{array}{cc}{T}_0=T+\frac{C_2{C}_f}{C_1+C_f}& \left[\mathrm{Equation}2\right]\end{array}$

(19) T=80.5° C.; C.sub.f=−5.25; C.sub.1=17.44; and C.sub.2=51.6 were substituted into Equation 2, and as a result, T.sub.0 was calculated as about 58.3° C., which seems to be the same value as the known value of 58.2° C. within the error range of measurement and calculation.

(20) Meanwhile, in order to plot the results obtained in the above experiment on a curve and to interpret the results again, the temperature gap was reduced and measurement was performed again.

(21) FIG. 4 shows a graph summarizing the measurement results according to a method of measuring a glass transition temperature of a polymer according to an exemplary embodiment of the present invention.

(22) Referring to FIG. 4, when the H ratio is assumed as a function of temperature through the temperature-H ratio curve, a second-order derivative at each point of the corresponding function may be approximately confirmed.

(23) In addition, through analysis of the graph of FIG. 4, the point (p2) where the second-order derivative has a minimum value was derived, and this point was also confirmed as about 58.2° C., which seems to be the same value as the known value of 58.2° C. within the error range of measurement and calculation.

(24) At this time, the collision experiment was carried out by varying the kind of polymer samples, and the results are shown in FIGS. 5 to 9. The polymer samples used in the experiment are as follows. PA6: Polyamide 6 (6-Nylon), degree of crystallinity of about 50%; PMMA: Polymethyl methacrylate, amorphous; PS: Polystyrene, amorphous;

(25) FIGS. 5 to 10 shows a graph summarizing the measurement results according to a method of measuring a glass transition temperature of a polymer according to an exemplary embodiment of the present invention.

(26) Referring to FIGS. 5 to 10, it can be clearly confirmed that the glass transition temperature and the degree of crystallinity can be accurately derived not only for PLA, but also for other polymeric materials.

(27) Meanwhile, the following reagents were prepared for accurate calculation of the degree of crystallinity.

(28) First reagent: PLA; amorphous PLA including L-PLA of about 88˜90 wt % and D-PLA of about 10˜12 wt % was used; Example 1

(29) Second reagent: PLLA; crystallizable PLA including L-PLA of about 96˜96.5 wt % and D-PLA of about 3.5˜4 wt % was used; Example 2

(30) Third reagent: a mixture of PLA and PLLA at a weight ratio of 1:1 was used; Examples 3 to 6

(31) The first and second reagents were used to prepare a polymer resin specimen in the form of a film having a thickness of 1 mm.

(32) The third reagent was used to prepare a polymer resin specimen in the form of a film having a thickness of 0.5 mm.

(33) The specimen was fixed to a collision part, a collision sphere was dropped thereon from a predetermined height (H.sub.0), a bounce height (H.sub.1) of the collision sphere bounced after colliding with the polylactic acid specimen was measured, and a ratio (H.sub.1/H.sub.0) was calculated.

(34) Since PLLA is known to have the maximum crystal formation rate around 115° C., annealing was performed around 95° C. to clearly confirm the difference in the degree of crystallinity according to control of the annealing time by slowing the crystal formation rate.

(35) The first reagent (PLA) was tested immediately without any modification, and the second reagent (PLLA) was left at about 95° C. for about 26 hours and allowed to form crystals, and then the experiment was conducted. The third reagent (PLA:PLLA=1:1) was divided into the following four cases, and the degree of crystallinity was adjusted, and then the experiment was conducted.

(36) Example 3: 1:1 mixture was left at about 95° C. for about 3.3 hours and allowed to form crystals, and then the experiment was conducted.

(37) Example 4: 1:1 mixture was left at about 95° C. for about 6.3 hours and allowed to form crystals, and then the experiment was conducted.

(38) Example 5: 1:1 mixture was left at about 95° C. for about 8 hours and allowed to form crystals, and then the experiment was conducted.

(39) Example 6: 1:1 mixture was left at about 95° C. for about 26 hours and allowed to form crystals, and then the experiment was conducted.

(40) The experimental results are summarized in FIG. 10 and Table 1. In addition, for the same specimen, the comparative data measured by XRD and DSC are summarized in Table 1 below.

(41) TABLE-US-00001 TABLE 1 H ratio Temperature at local Xc (XRD) Xc (DSC) Note value minimum point [%] [%] Example 1 0.006 76.3 — — Example 2 0.41 89.5 38.3 35.63 Example 3 0.0334 81.9 3.97 4.17 Example 4 0.090 84.6 7.78 11.84 Example 5 0.23 87.4 22.83 16.79 Example 6 0.33 89.25

(42) Referring to FIG. 10 and Table 1, when the degree of crystallinity of the polymer resin was derived by the method according to an exemplary embodiment of the present invention, it was clearly confirmed that it is possible to obtain the substantially same value as in XRD or DSC within the measurement error range.

QUOTATION MARKS

(43) 510: First tangent line; 520: Second tangent line; 530: Intersection of first tangent line and second tangent line; 540: Degree of crystallinity.