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antioxidant behavior in flexible pu foam.

by:Qihao      2019-09-02
Oxidation resistance behavior of Flexible PU foamThe (CFCs)
And other halogen hydrocarbon foaming agents in the slabstock foam have forced the use of a foam formula with an increasing water content to meet the density requirements.
These elevated water levels can increase the maximum temperature exposed in the foam and increase the risk of burnt degradation and discoloration (
Polymer decomposition).
In extreme cases, the foam may suffer from physical performance or even self-ignite.
To prevent the decomposition of polymers, antioxidants are usually present in commercial polyols.
Oxidation inhibitors exist in a wide variety of molecular classes that have different mechanisms of action (refs. 1 and 2).
Regardless of the specific mechanism by which a given antioxidant inhibits decomposition, mobility is a parameter common to all types of antioxidants.
A given molecule must have sufficient permeability in the polymer matrix in order to reach the threshold point.
On the other hand, compounds that are too free to migrate may migrate out of the foam, resulting in a loss of effective antioxidant concentrations.
In addition to the solubility and diffusion parameters that affect the migration capacity of compounds, the thermal gradient also contributes significantly to the movement of small and medium molecules in the polymer (ref. 3).
With regard to polyurethane foam bread, there is very little data describing the other profiles produced.
Several factors such as preparation changes (
Especially water level, indicator and alternate blow agent)
, The size of the buns, the reaction temperature and the environmental conditions may help to the temperature distribution measured in the foam bread.
In this article, data on the distribution of AO concentration on foam bread is given as a function of the corresponding temperature distribution of foam studied, three of which are in Texas, located at Dow Chemical Company Freeport
The fourth purpose of the study was to produce a foam of scale at the Texas fiber company in the Leggett & Platt division of Brunham, Texas.
The foam produced by Varimax includes the formula using 4. 1, 5. 1 and 6.
Perhundred parts (1 part)pphp)
Water is based on polyols and can be associated with 4.
1 pphp water foam made of Texas fiber.
Temperature data collected from foamin-
Place the thermocouple grid, give the time-
Temperature distribution in the asa position function of foam bread.
Through methane chloride extraction and liquid chromatography analysis, the antioxidant components of foam samples removed from the corresponding position of the thermocouple were examined.
Our goal is to determine the significance of the foam environment as a recipe function for antioxidant behavior.
Materials and methods for polyurethane foam used in this study foam formulation and manufacture are shown in Table 1.
Every one of the three levels creates a bubble (4. 1, 5. 1 and 6. 1 pphp)
Pilot lineat Dow chemistry using Varimax.
1 foam at 4.
1 pphp water level was made on texasfiber.
The initial reaction temperature is kept at 20-22 [degrees]C.
The ambient temperature of the free port operation is about 22 [degrees]C andfrom 25-34 [degrees]
Texas fiber.
Any deviations in the formula component are recorded in Table 1.
Table: Table 1-
Description of foam formula ingredients polyols-Voranol(1)3512TB; TDI -Voranate(1)T-80 (120 index); Surfactant -Q2-5160 (pilot line)Niax(2)L-562 (Texas Fibers); Amine -D 8264 (pilot line), BL 13/Dabco(3)33LV 1. 5/1 (Texas Fibers); Tin -
8-1
Trademarks of Voranol and Voranate Dow Chemical. ; 2 -
Niax is a trademark of United carbide. ; 3 -
Dabco trademark ofAir products.
The size of the foam bread varies depending on the formula used and the connection width of the two foam machines. The 4. 1, 5. 1 and 6.
1 pphp water wire foam is 27 \"x 50\", 36 \"x 51\" and 40 \"x 50\", respectively \".
The Texas fiber foam is 37 \"x 85 \".
Sample physical properties of foam (15\" x 15\")
According to the ASTM program, cut from the center of each foam used for physical testing.
Collecting temperature distribution of foam bread using foam measurement temperature datain-
Place the aluminum frame on the grid of the 15, 20 Gauge thermocouple wires connected to the personal computer.
The actual position of each thermocouple in the foam is measured, as shown in Figure 1.
From pouring to pouring for 20 hours, the temperature is recorded every 30 seconds.
The shelf is manually placed in a rising foam a few feet from the head.
The rack is stable before the foam gel strength is enough to support the thermocouple mesh.
A slight wrinkle occurred near the top of the foam, which came into contact with the shelf.
In addition to a small amount of compaction along the path of the thermocouple wire, the internal foam cell structure does not appear to be disturbed.
When they leave the foam machine tunnel, the foam beam is cut and the rack is located in an area 8 feet long.
Extraction and analysis of antioxidants in vertical slices (one inch thick)
After about 20 hours, every foam produced was taken out. Samples (about 1 gram)
Shot from the position in the foam corresponding to each thermocouple position.
Put these samples into the Asian nail Blue (60 ml)
Three days before the analysis
Reverse phaseliquid 18 column chromatography for the determination of the concentration of Austrian extract Novapak and water:60:40)
As a solvent for eluding.
Repeated extraction of a single foamsample with fresh solvents does not produce detectable AO.
The initial AO content of polyols used in this study was also determined.
In the case of 5.
1 pphp water foam produced in Freeport, additional foam samples for AO analysis were collected from vertical slicesat 6. 5, 33. 5, 61.
5 minutes 106 minutesThe 6.
Samples were collected at the cutting site for 5 minutes
After removing the foamproducced of 3 feet originally produced, turn off the saw.
4 steamed buns of 8 feet length (
One with hot coffee)
Was hacked and allowed to stand. The 33. 2, 61.
Take out 5 and 106 minutes of foamslices from three of these 8 feet loaves.
In this way, additional foam slices are collected, making them experience the same hot history.
Table 2 shows the physical properties of the foam prepared for this study.
Regarding the possibility of heat dissipation and migration of antioxidants, foam density is a major concern.
As expected, the density is from 1 as the water level increases. 04 to1.
53 The pcf is on the pilot bubble line. The two 4.
1 pphp water foam produced (
Liberty Port and Texas fiber)
The density is basically the same (1. 53and 1.
56, respectively).
Additional physical performance parameters are proposed for inspection.
Table: Table 2-
Foam physical performance density, % ILD the peak temperature of each foam occurs within about 50 minutes after pouring (figure 2).
As expected, the maximum core temperature of the three pilot bubbles is proportional to the water level.
Although there is some dispersion in the production foam temperature data, its maximum temperature (154 [degrees]C)
Closely replicate in the pilot line (155 [degrees]C).
The results of these peaks are basically the same ([+ or -]5 [degrees]C)
Previous thermocouple measurements.
Each of these peak core temperatures lasted about one to two hours in each of the three pilot bubbles.
The rate of temperature loss is proportional to the maximum temperature observed.
After 2-
The core temperature of these three bubbles is about 1/2 hours ,[degrees]C cooler (
Compare 50 minutes, figure 2)for the 4. 1, 5. 1 and 6.
1 pphp water foam respectively (figures 2 and3).
The difference in cooling rates observed in these three bubbles may be due in part to their respective densities.
The rapid cooling of the Epilot line foam results in a 5 equilibrium. 1 and 6.
1 pphp foam core temperature (149 and 148 [degrees]C)
About five hours after pouring wine. figure 4).
As mentioned above, both the trial line and the largerproduction size foam in Varimax are in 4.
1 Water, showing a similar peak infiltration.
The similarity of the temperature distribution of these two kinds of foam passes through 2-1/2 hours (figure 3)
But shortly after three hours, the difference in heat loss rate became a factor.
5-hour inspection of exotherm files (figure 4)shows a 24 [degrees]
The difference between the two bubbles.
It is also obvious that, compared with the pilot production line foam, the larger production foam has different temperature distribution from top to bottom, and the upper foam area is obviously warming.
Differences observed over time
The term, 5 to 20 hours later, the thermal history of the medium test line and the production foam are most easily explained by the surface area and volume differences that exist in both cases.
As expected, smaller foam with a high surface area to volume ratio is faster to dissipate heat than larger foam with a smaller surface area to volume ratio.
The entire 20-hour thermal distribution measured with thermocouple 2, 5, 8, 11, and 14 shows each of the four bubbles (figures 5 to 8).
Table 3 and Table 4 list the 20-hour antioxidant concentration distribution of phenol and amine inhibitors, respectively.
In the center, the number of both AOsis has decreased (
Corresponding to thermocouple 5, 8, 11)
All the studied bubbles
Table: Table 3-
Concentration distribution of phenol antioxidants (ppmppolyol)4. 1 Water5. 1 Water6. 1 Water4.
Table 4-1 water production
Distribution of amine antioxidant concentrations (ppmppolyol)4. 1 Water5. 1 Water6. 1 Water4.
4. production of water.
1 pphp Water pilot line foam contains high concentrations of phenol and amine AO along the top and left columns of the thermocouple position.
In fact, all of these values are greater than the original alcohol AO content (
3,308 phenol/1,564 amine).
It was found that the ean phenol AO content of this cross-section was 3,068 ppmor 93% of the initial AO level.
The average amine AO content of this sample is 1,362 ppm or 87% of the initial AO level. The 5. 1 and 6.
The 1 pphp Water pilot foam has a similar distribution of ao concentrations and the remaining AO is much less than 4.
1 pphpwater pilot line foam.
The average phenol AO content is 1,435 ppm (5. 1water)and 1,833 ppm (6. 1 water)
These bubbles.
The content of this extracted phenol AO represents 43% and 55% of the initial alcohol AO content, respectively.
The average amine AO content of these two kinds of foam is 496 ppm (5. 1 water)and 534 ppm (6. 1 water).
These values accounted for only 32% and 34% of the initial alcohol amine AO content.
AO concentration profile of 4.
The water-producing foam mainly displays the bid value along the side of the foam bread, especially the top of the foam bread.
The phenol AO values corresponding to thermal coupling 4, 7 and 10 far exceed 3,420 ppm in the alcohol originally used for this foam.
The average phenol AO content for this cross-section is 2,285 ppm or 67% of the initial value.
The amine AO profile does not contain a value of more than 1, 713ppm of the initial alcohol content and gives a cross-sectional average of 661 ppm or 39% of the initial amount. The 5.
1 The change of the concentration distribution of foam AO in water wire with time was also studied.
6 Phenol AO profiles. 5, 33.
5 minutes and 106 minutes from pour are very different from the last 20 hours.
These early cross-sections show a high concentration of phenol AO in the center of the foam relative to the edges. The 6.
The 5-minute cross-section gives an average phenol AO content of 3,068 ppm or 93% of the initial polyols value.
This cross section was taken very well after the explosion.
Closing indicates that there is little loss of phenol AO. The 33. 5, 61.
Cross sections of 5 and 6 minutes produce 2,238 ppm, 2,214 ppm and 2,043 ppmaverage phenol AO.
These values represent 68%, 67% and 62% of the initial alcohol AO content, respectively.
As noted above, the average phenol AO content in the 20-hour cross-section was found to be 1, 435ppm or 43% of the starting value.
The distribution of amine AO concentrations showed similar results over time, but the cross-sectional mean was much lower. The 6. 5, 33. 5, 61.
The mean values for 5 minutes and 106 minutes were 1,149 ppm, 614 ppm, 486 ppm and 532 ppm, respectively, or 73%, 39%, 31% and 34% of the initial alcohol amine AO content.
Similarly, the 20-hour amine AO cross-sectional average for this foam is 445 ppm or 28%.
Conclusion three water levels (4. 1, 5. 1 and 6. 1 pphp)
This study represents a series of potential changes in the future of polyurethane foam manufacturing. The 4.
1 pphp water foam is a common upper limit for full water foam currently used by commercial foam producers. The 5. 1 and 6.
1 pphp water foam represents possible changes in the future as the use of alternative blowing agents decreases.
The core temperature and maximum temperature values of the three pilot wire foam are very consistent with the previous single probe data.
The temperature distribution reported here defines the gradient that leads to a low thermal conductivity of polyurethane foam.
This characteristic causes the continuous warm core of the foam edge temperature to drop.
The peak discharge time of these three bubbles occurs within one hour after pouring, and the peak discharge ratio increases as the water level increases in the formula.
After about two hours, the foam begins to cool, and the cooling rate is proportional to the maximum temperature.
The higher the foam core temperature, the faster the cooling speed.
Due to different cooling rates, 5. 1 and 6.
1 The water foam has a similar temperature distribution for about five hours after being poured.
The cooling rate of foam bread is also affected by the foam size. The 4.
1 pphp water production and pilot foam have similar peak temperature distribution;
The initial heat generated is the same.
However, when these bubbles start to cool, the larger the specific surface area (mass)
The foam of the pilot line allows it to cool faster.
The difference became apparent five hours later.
After ten hours, there were nearly 50 [degrees]
The difference between the two bubbles.
The effects of different thermal histories of the four foam studied can be seen in the distribution of antioxidant concentrations.
The most eco-friendly foam.
1 pphp Water pilot line foam, retains the minimum mass of its initial AO package even after 20 hours.
Two other pilot bubbles, five. 1 and 6.
1 pphp water, lose more than half of the starting AO content within 20 hours.
When comparing production and pilot foam at the same water level (4. 1 pphp)
See the different AO contours.
The production foam with large temperature gradient is less recyclable AO than the cooling pilot line foam with large temperature gradient. Both of the 4.
1 The AO concentration distribution of pphp water foam supports the hypothesis of AO migration.
The AO concentration detected along the sides and edges of these foam exceeds the initial load of AO in the polyalcohol used.
The only way this can happen is to migrate ao from the warm center of the foam to the cool edge.
Finally, the AO concentration examined as a function of time indicates that the small AO will be lost due to blow off.
Looks like at least through the first 1-
There are still a large number of AO in the foam center for 1/2 hours.
However, it can also be seen that the total AO content is 6-
1/2 minutes 1/2 hours after pouring water
After 1-1, continuous AO loss and final AO concentration distribution will occur
1/2 hours until some time 20 hours after the fall.
It is not yet known how much undiscovered AO is consumed and how much is lost through migration to the atmosphere.
In addition, since there is no significant discoloration of these substances, we are unable to check the interaction between AO concentration distribution and color formation.
These areas will be the subject of future work. References[1. ]Lutz, J. T. , Jr. , ed. 1989.
Thermoplastic polymer additives: theory and practice.
New York: Marcel Decker[2. ]Ranby, B. andJ. F. Rabek. 1975.
Degradation, photooxidation and photostability of polymers.
John Willie and his sons. [3. ]Tochacek, J. and J. Sedlar. 1989.
\"The effect of molecular weight on the efficiency of phenol antioxidant as polypropylene stabilizer --
Brief communication, \"Degradation and Stability of polymer, 24: 1-6.
Figure 1-
Position of thermocouple (
View from mixhead)
Figure 2-
Introduction to foaming temperature rise (
Up to 50 minutes)
Figure 3-
Introduction to foaming temperature rise (at 2. 5 hours)
Figure 4-
Introduction to foaming temperature rise (five hours)
Figure 5-4.
1 Water wire foamPHOTO: Figure 6-5.
Figure 7-1 foamPHOTO water wire6.
Figure 8-1 foamPHOTO water wire4.
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