measuring the effects of post-cure heat aging on compound dynamic properties.

by:Keyuan     2020-06-12
RPA 2000 rubber process analyzer from Alpha Technologies (
The rubber industry has been in use for over 15 years as a very effective raw polymer Tester, a handling tester for mixed rubber stock, an advanced wiper and DMRT for post-measurement
Dynamic properties of curing (ref. 1).
Alpha polymer iesapa 2000 advanced polymer analyzer (
Was introduced into the polymer industry in 1998 to test plastics (ref. 2).
APA is different from RPA because it can install parallel plate molds (figure 1).
The cured rubber sample can be taken out and placed aftercure air oven.
The sample can then be re-inserted into the parallel plate mold for additional dynamic characteristic measurements.
It is impractical to re-insert the cured rubber sample from RPA\'s double cone mold, because it is difficult to get good contact between the sample and the mold.
Since 1987, the double cone mold has been commercial in the rubber industry.
They are basically the de facto standards used in today\'s rubber industry (ref. 3).
However, on 2004, when a cured rubber sample needs to be removed and re-inserted for use-
Study of treatment or study of air aging.
Some rubber compounds based on high performance specialty rubber need \"post
After their normal pressing order, cure \"to achieve the best curing physical properties. The post-
Curestep is usually carried out in the air
Circulating oven (
In ambientpressure)
150-3 to 24 hours232[degrees]
C depends on the pound.
Sometimes, a post
When curing compounds based on FKM, Q, ACM, the curing step is necessary, AEM or HNBR in order to discharge the gas formed from the vulcanization process, these gases may destroy or destroy the chemical cross-linking formed by curing and damage the final physical properties (refs. 4-7).
For FKM treatment, one after
Curing is the most critical for the treatment of double phenol, and for silicone treatment, for peroxide treatment, curing is the most critical.
For the purpose of this study, we quantified
Curing of peroxide cured silicone compounds and abis phenol AF cured FKM compounds (ref. 8).
Different from the primary curing process
The curing process is very aerobic, and if the exposure time is long enough and the temperature is high enough, the oxidation effect can be measured with compounds based on general rubber.
Thus, the study also included the second series of tests that quantify the effects of aerobic aging and anaerobic overaging
Curing comparison of a series of rubber stocks containing different levels of antioxidants and anti-reversal agents.
The antioxidants studied in the NR test formula include TMQ and 6PPD. Anti-
The reduction additives also studied in the same testrecipe include the Liujia ring-1,6-bis-thiosulfate (HTS)and1,3-bis-(
Citraconimidomehyl)-benzene (BCI-MX).
Most of the tests carried out in this study were done with apa2000.
APA is very similar to RPA 2000 except that it has software and hardware tested with a parallel flat die, not just a double cone die.
The parallel plate mold enables the rubber sample to be removed after curing and placed after
Solidify the oven and re-insert it into the lower mold for re-testing (figure 2).
The lower die is connected to a high-tech robot motor, which is programmed to oscillate in a sine wave with a rubber sample.
The upper mold is connected to the reaction torque sensor to measure the complex torque response (S*)
And the angle of work (6).
These measurements enter the Fourier transform to calculate the pure elastic response (S\')
Pure viscous torque response (S\"). [
Figure 1 slightly][
Figure 2:
For parallel plate molds, the relationship between torque and shear modulus is shown in equation 1. T = [[tau][R. sup. 4]/2L]G*[theta](1)
Among them: T = torque;
L = sample thickness; R = die radius;
G * = complex shear modulus; and [theta]= strain (radians).
This equation can be rearranged as follows: G * = T /[[tau](20. 63mm)[sup. 4]/(2)(2. 576mm)][theta](2)
So it\'s simple if the mold gap is set to 2.
58mm, shear modulus G (in kPa)
Can be from torque (in dNm)
Simplify the equation by: G = (54. 1 x torque)/(
Degree arc strain)(3)Also,every [+ or -]1.
0 degree arc strain equal [+ or -]14% strain.
All tests are patented o-
In the case of no loss of Test pressure, the ring procedure for sealing test materials between parallel plate molds (ref. 9).
This technique is usually used to test thermoforming materials, thermoplastic plastic and thermoplastic elastic materials;
However, it is also suitable for rubber testing with or without piles
Treatment or aging of air.
Figure 3 shows the rubber sample placed in a special environment
Ring on nylon 6, 6 film.
Figure 4 shows the rubber test sample o-
Before curing, the ring and film should be placed in APA. [
Figure 3 slightly][
Figure 4 slightly]
Figure 5 shows how APA parallel plates can be used in sampleand o-ring.
Because of the o-position
When the mold is closed, the pressure between the parallel plate mold and the sample is maintained more effectively (
This explains why it is usually used to test plastic Hot Melt Adhesive with relatively low viscosity). Also, these o-
There is no measurable effect on the calculation of the Ring (ref. 10).
Usually, the mold gap of the parallel plate mold is 2.
58mm, no-o is used for most rubber samplesring.
However, when the rubber sample is used with special o-
Ring, the target thickness is 2. 8 ram.
Target weight used with this o-
The loop test procedure is first determined by curing excess body material on parallel plates without o-ring.
The flash on this curedsample was carefully cut off from the sample and weighed carefully.
So when using theo-
The loop program is equal to the weight of the cured sample that takes out the flash plus 0. 2 grams. Target weight (for o-ring method)
= Weight at 100% fill factor + 0. 2 g (4)
Figure 6 shows the sample taken from APA after the curing test is completed. [
Figure 5 Slightly][
Figure 6 slightly]
The orientation of the cured sample is marked before removal so that it can be re-inserted into the lower mold in the same position. The o-
Remove the ring from the sample and measure and record the thickness of the center sample using a thousand-meter.
According to Equation 1, these values are directly entered into APA Pathfinder Software for dynamic modulus calculation.
The cured APA specimen and its o-
The removed ring is put back on the lower die of APA to measure the curing dynamic die that is usually 50 [degrees]C.
The process is repeated until apa establishes an aging (original)
After-sales dynamic property base line at50 【degrees]C.
These APA specimens were placed centrally in anair-
Cycle oven aftercure (
For special rubber-based compounds)or air aging (
For common rubber-based compounds).
During a predetermined time interval, APA samples are taken out of the oven, allowing cooling to room temperature, and placed back on the lower APA mold according to their marking position, to measure the change of curing dynamic properties of 50 [degrees]
C. base temperature.
Silica gel studies six uncured silicone rubber final compounds, based on the same Masterbatch in two different batches, each with an increased peroxide treatment load, using APA o-
Already discussed earlier. For silicone (Q)
, The target weight of the sample of Theo-
The loop program is 4. 4 [+ or -]0. 1 grams. (The 4.
4g target weight is passed in no o-
After Ringand, remove the cured specimen, carefully cut off the flash, re-weigh without flash, add 0.
2g, 4. 4g. )
One 4 per test.
4g samples are placed in o-
Ringon of nylon 6, 6 film (23 [micro]m thick).
Then another piece of nylon film was placed on both items, the sample and ring were quickly placed on the APA lower mold, after which the mold was quickly removed.
At116 [APA constant temperature curing material for each sample]degrees]C, 2. 8% and 1.
67Hz in 5 minutes
After the sulfur hot curing test is completed, set the mold to open automatically and mark the curing sample carefully (
Notice that it is aligned with the lower mold).
Then the rubber specimens have been taken from lowerdie and o-
Carefully remove the ring and film from the test sample. [
Figure 7 Slightly][
Figure 8:
These cured APA specimens (or pieces)
Is allowed to cool, and each of these test pieces is carefully re-inserted into the groove of the lower parallel plate (
Original orientation)
Diesel oil is turned off and tested at 50 [degrees]C, 2.
8% and 1. 67 Hz.
The test was repeated three times. (
This establishes an original, unaged, dynamic baseline of property for future comparisons. )
After finishing these-
Measurement of dynamic properties of Cure 50 [degrees]
Together with APA, these test pieces are placed in apre-
[Gravity convection oven set 205]degrees]C.
All of these APA test pieces were kept in this oven for a full four hours (
During this period, these APA sheets were randomly rearranged at least once to avoid the effect of a possible uneven temperature distribution in the oven).
After four hours of oven aging, all APA test pieces were removed from the oven and allowed to cool to room temperature.
They then re-tested individually on APA using the same test conditions and the same techniques described earlier. [
Figure 9 omitted[
Figure 10 slightly]
In addition, another set of samples were also cured at a constant temperature of 116 [on RPA]degrees]
C at 01:05. 67 Hz, and 2.
8% strain, then ASTM D6601 strain at 116 [scan]degrees]
C was executed in the same test.
A rubber compound based on fluorine rubber (FKM)
As shown in Table 1, a double phenol af/Onium curing system was selected for this study.
ASTM International is currently considering this compound (
D11 committee on rubber)
Standard reference compound for rotor-free wiper testing.
This is due to the fact that with the blocking chemical reaction of the biphenol curing system, this compound should have a very long shelf life at room temperature without changing its performance.
Typically, products made of FKM compounds are cured with abis phenol
Based on the system needs
Cure to achieve the best physical performance.
This is especially true for FKM compounds in the treatment of double phenol curing compounds compared to peroxide and diammonium curedFKM compounds, which may still require post-curing, but may not be very important. [
Figure 11 omitted][
Figure 12:
This FKM compound uses o-with APA-
Circular procedure for post-study effects
Curing of APA curing kinetic properties. The same APA o-
The ring procedure for silicone rubber is also used for this FKM compound, but under the new test conditions given below: * Sample target weight: 6. 3 g;
* APA curing test conditions: 175 [degrees]C, 1. 4% strain, 1.
67Hz for 6 minutes; * Post-
Aging conditions of curing furnace: 100 [1 hourdegrees]
C and test, add an hour at 125 [degrees]
C and testing, an extra hour, 150 [1 [degrees]
C and test, add an hour at 175 [degrees]
C and test, add an hour at 200 [degrees]
C and testing, 3 extra hours, 200 [degrees]
C and testing, 4 extra hours, 200 [1 [degrees]
Cand test, 4 extra hours, 200 [1 [degrees]C and test (
Total waiting time: 16 hours).
* Post APA test conditions
Curing performance: No film or o-
Loop, three independent measurement of dynamic properties (back-to-back)each at50[degrees]C, 1. 67 Hz and [+ or -]2. 8% strain (
Using matrix sub-Tests).
Discard the first measurement and average the last two.
As shown in Table 2, nine natural rubber-based compounds have been prepared for air aging studies of natural rubber. [
Figure 13:[
Figure 14 omitted]
It can be seen that two very effective antioxidants (6PPD and TMQ)
Was selected as the use of this natural rubber compound. Also, two well-
Duralink HTS and Perkalink 900, knownrevision inhibitors (BCI-MX)
FromFlexsys was also selected for this experiment.
These nine natural rubber-based compounds are used in APAusing o-
Ring procedure to study the effect of air aging on the later stage
A curing furnace with APA curing dynamic properties. The same APA o-
The ring procedure for silicone rubber and fluorine elastic rubber compounds is also used for these nine NR-based compounds, but under the new test conditions given below: * Sample target weight: 4. 5 g;
* APA curing test conditions: 150 [degrees]C, 1. 4% strain, 1.
67Hz for 40 minutes;
* Aging conditions of oven: 100 [1 hourdegrees]
C and testing, 3 extra hours, 100 [degrees]
C and test, additional 32 hours at100 [degrees]
C and testing, 48 extra hours, 100 [1 [degrees]
C and testing, additional 16 hours, 100 [1 [degrees]
C and test, extra 24 hoursdegrees]
C and test, another 24 hours at 140 [degrees]C andtest.
* APA test conditions for performance after aging: No film or o-
Loop, three independent measurement of dynamic properties (backto-back)each at50[degrees]C, 1. 67 Hz, and [+ or -]2. 8% strain (
Using matrix sub-Tests).
Discussion of post-APA test results for silicon
Curing measurement Figure 7 shows the increase of APA dynamic energy storage modulus G\' after air ovencure.
Can be seen, after
The curing process does result in an increase in the measured APA storage modulus G.
Figure 8 shows after-cure.
The mother material of Series 1 is the same as the mother material formula of series 2.
Although compound series 1 and Series 2 have the same level of peroxide efficacy, the formula for using No. 2 Masterbatch is always lower than the original curing modulus for using No. 1 masterbatch.
In addition, the increase of elastic modulus G\' from original to post
The compound based on the second Masterbatch is more solidified.
The reasons for these differences may be due to the different preparation and mixing of silicone Masterbatch, although they are the same in formula and composition.
Because when a lower test temperature is applied, the Heat shrinkage of silicone rubber is large, the curing modulus of silicone rubber is measured at 50 [degrees]
C. in the RPA test, due to the rubber shrinkage and resulting in loss of mold pressure, in the same test, it solidified at a higher temperature and therefore did not work.
This is because for RPA, the dynamic performance measurement of curing must be carried out in the same test, and in the same test, it is cured in situ in advance at a higher curing temperature.
However, o-
This shrinkage problem is avoided using theAPA loop program.
As mentioned earlier, o-
The ring test is divided into two steps.
In the first step, heat the sample at a higher curing temperature, and then remove o-from the diesel-
Remove rings and film.
Then, at a lower temperature, carefully re-insert this cured sample into the lower mold, in which case 50 [degrees]C.
However, Figure 9 shows the measurement of curing dynamic modulus G\' at a curing temperature of 116 [in this silicone study]degrees]
C is very relevant to the curing G\' value measured with APA at the age of [50]degrees]C, before post-cure.
On the other hand pre-post-
Curing dynamic characteristic data from APA or RPA is a bad predictor after final release
Cure dynamic properties, the month shown in the figure.
It emphasizes after the actual measurement of the cureddynamic attribute
Cure, instead of trying to predict it in the dynamic characteristic measurement carried out later
Peroxic silicone curing.
Coefficient of variation after measurement from APA replication testcure was 0.
8%, and in post-cure was 1. 1% APA post-
Curing measurement of fluorine rubber most fluorine rubber (FKM)
In general, a post-processing step is required for compounds and FKM compounds cured with double phenol to optimize physical reactions.
When the FKM compound is not
Removal of gas by-curing
Vulcanization products, these-
The product may affect the integrity of the cross-linked matrix.
These harmful vulcanization
Products must go
Through the post-processing process (refs. 11 and 12). [
Figure 15 omitted][
Figure 16 omitted]
The oven is controlled at a set temperature rise of 1 hour 100 [start]degrees]
C, 1 hour at 125 hours [degrees]
C, 1 hour at150 【degrees]
C, 1 hour at 175 hours [degrees]
C and 12 hours 200 [degrees]C(
A total of 16 hours at five different temperatures)
, As shown in Figure 11, the modulus of rise is monitored at the same time.
With more theoretical applications, this curve is gradually approaching a platform.
Figure 12 shows a reduction in curing tan 8 at 50 [degrees]
C. since post-cure.
Unlike Figure 11 of G\', this number seems to be more stable with the increase in the later period
History of healing
It doesn\'t seem to show up outside at 200 [16 hours later]degrees]C of postcure.
APA air oven measurement of natural rubber compounds natural rubber-based samples were also tested in air oven using APAafter incremental exposure time.
Figure 13 shows the effect of air oven aging on natural rubber compounds loaded with different concentrations of N-(
1, 3 dimethylbutyl)-N\'-phenyl-p-phenylene-diamine [6PPD]
And polymerization 1,2-dihydro-2,2,4-
Free of antioxidants.
Blank as expected (
Any AO is invalid)
With the increase of aging in hot air of 100 [continued softeningdegrees]
C, as shown in the g\' elastic modulus results.
On the other hand, compounds containing antioxidants actually become more difficult (by APAtesting)
Although these compounds are based on natural rubber, they increase with the aging of the air furnace.
If it\'s not because of oxygen (
Formed free radicals)
These compounds containing antioxidants may only soften (
Like under reduced anaerobic conditions).
These NR compounds become more difficult due to oxidation aging (figure13)
The increase in oxidation and cross-linking also led to tan 8 [tan 8= G\" (loss modulus)/ G\' (Storage modulus]
As shown in Figure 14, it begins to increase again due to more severe oxidation degradation.
In addition, due to continuous molecular chain breaks, the blank tan 8 continues to rise with greater air aging.
Figure 15 shows the effect of air oven aging on curing elastic modulus G\' of natural rubber compounds loaded with different concentrations of HTS [hexamethylene-l,6-bis(thiosulfate)
Sodium phosphate saltdihydrate]and BCI-MX [1,3-bis(
Both of these compounds are reduction inhibitors, not antioxidants.
HTS prevents the reversal of natural rubber-based compounds during vulcanization by forming a mixed cross-linking containing sulfur and carbon atoms, as shown below :-[S. sub. x]--S--(C[H. sub. 2])[sub. 6]-S--[S. sub. x]-
These bonds interact with other polys bonds.
The hexyl chain is more stable in thermodynamics than the polysulfur chain, and it is more resistant to high temperature curing and high temperature aging degradation than the polysulfur chain (refs. 13-15).
On the other hand, BCI-
MX prevents the effect of natural rubber recovery by forming a more stable C-
C. Cross chain in the vulcanization process to compensate for loss in the sulfur cross chain that has a softening effect on the cured compound. Carbon-
The carbon bond has higher binding strength than the sulfur bond.
Sulfur bonding. [
Figure 17 slightly][
Figure 18 slightly]
As the aging of the air furnace increases, the elastic modulus G\' of the blank continues to decrease.
However, with the increase of air aging, the HTS compounds remain very stable, showing better thermal stability of ethylene cross-linking. Also, the BCI-
MX compounds only increased slightly.
This slight increase may indicate the formation of carbon.
A more stable carbon bond in thermodynamics.
Figure 16 shows a change in tan 6 cured due to the presence of these reversal inhibitors. Because BCI-MX forms carbon
During air aging, the carbon chain replaced the lost sulfur chain, and the solidified tan 6 decreased because when bci-MX are used.
Overall, however, Tan [delta]
With air aging, the values remain relatively constant due to the presence of sterilization inhibitors. [
Figure 19 Slightly][
Figure 20 omitted]
Figure 17 and 18 show the effect of air aging at 140 [degrees]
C for NR compounds.
In 140 [further air aging of these specimensdegrees]
Instead of the usual 100 [degrees]
C does lead to aging hardening of these compounds.
However, the effectiveness of testing natural rubber based compounds in 140 [is questionable]degrees]
C will predict the low temperature of their field performance.
Figures 19 and 20 show the curing curve of 170 [degrees]
C. Natural Rubber based compounds are in 1.
The 67Hz and 7% strains lasted for 25 minutes under hypoxia conditions.
Fig. 19 comparison of blank NR compounds (
No AOs or reduction inhibitors)vs.
Other compounds containing tmq antioxidants with different loads and 6PPD antioxidants/ozone-resistant agents.
These anti-degradation drugs have little effect on reversal.
Figure 20 shows the HTS and BCI-
MX reduction inhibitor prevents reduction under hypoxia conditions [anaerobic]degrees]C.
As mentioned earlier, these reversal inhibitors are very effective in preventing reversal. Conclusions 1. The new APA o-
The loop program using parallel flat die is very effective in measuring the effect of post-curing on the composite properties of silicone and fkm. 2. This new APA o-
The ring procedure is also effective in measuring the effect of aging in oxidized air ovens on natural rubber-based compounds. 3.
The aerobic oxidation effect measured with APA oringprocedure was significantly different from the aerobic reduction effect measured on the same NR compound. 4.
Measurement repeatability of this new APA o-
The coefficient of variation of the loop program is 1% or better, very good.
This article is based on a paper submitted at the ACS theRubber branch meeting (www. rubber. org). References (1. )J. Dick and H.
Pawlowski, \"Application of rubber process analyzer\", rubber and plastic news, April 26 and. (2. )Xiaofeng (Joe)
Xu and Henry PawlowskL \"measuring the dynamic mechanical properties tester for the treatment of ofthermoset,\" submit POLYCHAR-
University Conference on polymer properties
January 7, North Texas, Denton, Texas9, 1997. (3. )ibid ref 1. (4. )J.
Dick, rubber technology, performance composite and testing, Hanser, Cincinnati/Munich, 2001, pp.
207, 223, 232, 236,244, 487. (5. )R. D.
DeMarco, \"New generation polymerization rubber\", rubber chemistry. Tech. , Vol. 52, 1979. (6. )L. F. Pelosi, A. L. Moran, A. E.
Balles and T. L.
\"Volatile products evolved from fluorine rubber compounds during curing\", rubber chemistry. Tech. , Vol. 49, 1976. (7. )
DuPont technical information company \"Fluorine rubber\" revised edition4, 2005. (8. )John S.
Dick and Alan T.
Worm, \"Storage Stability of luoroelastmer compounds based on the biphenol AF/Onium curing system and its potential use as a standard reference compound\", 1997 meeting of ACS Rubber Division autumn, held in Cleveland(9. )U. S.
Xu Xiaofeng, Henry Pawlowski, Alpha Technologies, patent 6,336,357, March 15, 1999. (10. )
Henry Pawlowski and Thomas wysswiski, \"measuring the melt viscosity and transformation of thermoplastic polymers using DMA with treated and pressurized sample chambers\", ANTEC meeting in Boston, MA, May 2, 2005(11. )ibid ref 6 (12. )J. Dick and A.
Worm, \"Storage Stability of luoroelastmer compounds based on a polyphenol AF/Onium curing system and its potential use as a standard reference compound\", World of rubber, January 1999. (13. )
Byron Toto, Otto Mande and Gilbert Antoine, \"Composite Post-vulcanization stabilizer for increased durability\"
135A, presented at the ACS rubber sector meeting on October. 16,2001. (14. )
Rabin Datta, \"ways to improve resilience,\" rubber and plastic news, February. 10, 1997. (15. )Fred Ignatz-
Hoover, Otto Mande and Rabin da ta, \"better features with anti-reversal compound\", rubber and plastic news, August. 23, 1999, p. 36. by John S. Dick, Henry A.
Rose and Jack Kuykendall, alphatechnoogies (www. alpha-technologies. com)
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