Study on the thermal stability of TPU modified by silicone rubber highly filled with MQ silicone resin

doi:10.21203/rs.3.rs-3902154/v1

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Study on the thermal stability of TPU modified by silicone rubber highly filled with MQ silicone resin

https://doi.org/10.21203/rs.3.rs-3902154/v1

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Procuring silicone rubber composite with different content of vinyl MQ silicone resin was prepared and its thermal stability was evaluated. A total of 50wt% MQ resin containing 5wt% vinyl MQ exhibited optimal thermal stability and was consequently chosen. This silicone rubber composite was blended with TPU at high temperature using an internal mixer to produce a modified TPU. The TPU modified by silicone rubber was firstly investigated by Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA). The FTIR results indicated that negligible chemical reactions occurred between TPU and silicone rubber during the mixing process. Furthermore, the TGA results demonstrated that the silicone rubber composite positively influenced the thermal stability of TPU. Additionally, the modified TPU displayed satisfactory thermal stability even after aging. Moreover, Scanning Electron Microscope (SEM) results indicated that uniform dispersion of silicone rubber was facilitated by the banburying method. The tensile strength of modified TPU initially increased and then decreased when the content of silicone rubber reached 3wt%. On the other hand, the elongation at break of modified TPU demonstrated continuous improvement. Furthermore, the mechanical properties of the modified TPU were still acceptable after aging.

silicone rubber

MQ resin

thermoplastic polyurethane

thermal stability

mechanical properties

Thermoplastic polyurethane (TPU) is a thermally processed elastomer with high elasticity and plastic properties. It exhibits several advantageous characteristics such as radiation resistance, impact resistance, electrical insulation, and wear resistance, which have contributed to its wide-ranging applications across various industries [1–7]. Nevertheless, TPU does have certain shortcomings, with one of the notable issues being its inadequate thermal stability. Extensive studies have shown that some properties of TPU declines apparently when the using temperature surpasses 80℃, and decomposition occurs when the temperature reaches 200℃. These limitations restrict the use of TPU in specific conditions, making the investigation of thermal stability of TPU a hot topic in both industry and academia worldwide [8–15]. As is known, silicone rubber is a type of polymer elastomer with a unique combination of inorganic and organic structures, enabling it to demonstrate excellent thermal stability, weather resistance, hydrophobicity, and chemical stability. However, its mechanical properties are relatively poor, restricting its application in certain fields [16–22]. If it were possible to develop a composite material incorporating both the advantageous mechanical properties of TPU and the exceptional thermal stability of silicone rubber, the range of applications for such a combined composite would be significantly expanded. Conventionally, polyurethane and silicone rubber are blended together to prepare the composite material. The silicone rubber is sheared into particles under high shear force and dispersed evenly in the polyurethane matrix, which forms the "sea island" structure. However, TPU is a polar polymer, while silicone rubber is non-polar, resulting in poor compatibility between the two materials. Consequently, the interface between the two polymers is challenging to achieve fusion, leading to the occurrence of numerous interface bonding defects. These defects, in turn, hinder the mechanical properties of the blended composite.

On the basic of the above background, in this paper, the procuring silicone rubber composite with brilliant thermal stability was prepared and then intermixed with TPU at high temperature. As a result, the silicone rubber was completely solidified and the modified TPU with high thermal stability was obtained. The interaction between TPU and silicone rubber was studied by FTIR and SEM. Besides, the modified TPU was analyzed by TGA to clarify the influential mechanism of silicone rubber on the thermal stability of TPU. Furthermore, tensile strength and elongation at break of the modified TPU were also explored.

2.1Materials:

Thermoplastic polyurethane85085A was supplied by Bayer AG., Ltd., vnyl silcone oil (mass fraction and molar content of vinylare1.44wt%and 0.053mol/g separately, M_W is 50000 g/mol, dynamic viscosity is 8000 mPa•s), hydrogen-containing silicone oil (mass fraction and molar content of hydrogen is 0.36wt% and 0.36mol/g separately, MW is 16000 g/mol, dynamic viscosity is 240mPa•s) were supplied by Foshan Huagu organic silicon Co., Ltd., vinyl MQ resin(mass fraction and molar content of vinyl is 2.0wt% and 0.074mol/g separately) and methyl MQ resin were supplied by Wynca chemical industry group Co. Ltd., platinum catalyst (5000ppm) was supplied by Dongguan Kebei Silicone Material Co., Ltd., cyclohexane (99.8wt%)and methyl butynel alcohol(99.8wt%) were supplied by Aladdin Co., Ltd..

2.2Experiment:

The graphical abstract is as follows:

Vinyl MQ resin, methyl MQ resin, vinyl silicone oil, hydrogen-containing silicone oil, platinum catalyst and methyl butynel alcohol as inhibitors (were dissolved in cyclohexane. The proportion of each material was listed in Table 1.Thenthe mixture was uniformly dissolved in cyclohexane and put into a planetary power mixer. And the solvent was removed by vacuum distillation at 50℃for 1 hour to obtain the procuring silicone rubber composite with different content of vinyl MQ resin. Then the thermal stability of different kinds of silicone rubber was evaluated by TGA to gain optimum formula.

Table 1

Procuring silicone rubber composite with different content of vinyl MQ resin
samples		50wt% MQ resin		vinyl silicone oil	hydrogen-containing silicone oil	platinum catalyst	inhibitors
samples		vinyl	methyl	vinyl silicone oil	hydrogen-containing silicone oil	platinum catalyst	inhibitors
0wt% Vi-MQ 5wt% Vi-MQ 10wt%Vi-MQ 30wt% Vi-MQ		0g 5.1g 10.2g 30.5g	50.8g 45.7g 40.6g 20.3g	40g 40g 40g 40g	10.8g 10.8g 10.8g 10.8g	0.1g 0.1g 0.1g 0.1g	0.05g 0.05g 0.05g 0.05g

The selected procuring silicone rubber composite was mixed with TPU in different proportion via banburying at 140℃ for 10min as shown in Fig. 1. Then the modified TPU with different content of silicone rubber was prepared. Furthermore, the modified TPU was crushed into particles and the required samples were prepared by injection molding according to the relevant test standards.

2.3Measurements

2.3.1Thermogravimetric analysis (TGA)

Thermogravimetry investigations of samples were conducted with a SDT-Q600 (TA Instruments, Inc.). Samples of 5 ~ 10 mg were heated in nitrogen or air atmospheres with a gas stream of 10 ml/min at a heating rate of 10K/min.

2.3.2 Fourier transform infrared spectroscopy (FTIR)

TPU thin films for FTIR test were prepared in an oven at 140℃by clipping two pieces of slide glass together with samples squeezed in the gap. The measurement was conducted on a Nicolet Magna 560 IR spectrometer (Spectra Lab Scientific Inc.) at a resolution of 4 cm^− 1, from 400 cm^− 1 to 4000 cm^− 1.

2.3.3Scanning electron microscope (SEM)

Scanning electron microscope (SEM) observation of a fractured surface after notched impact test was performed using a KYKY-2800 SEM with the operating voltage of 15 kV.

2.3.4Tensile strength and elongation at break test

Tensile strength and elongation at break were measured by Instron 4320 test machine according to GB/T 1040-92.

3.1 thermal stability of silicone rubber added with MQ resin

Samples of pure silicone rubber and the silicone rubber added with 50wt% MQ resin which contained different content of vinyl MQ resin were tested by thermogravimetric analysis, and the effect of vinyl MQ resin on the thermal stability of silicone rubber was studied. TG and DTG curves in nitrogen are shown in Fig. 2, and the characteristic temperatures (onset decomposition temperature T_onset, maximum decomposition temperature T_max) and maximum decomposition velocity V_max are listed in Table.2. T_onset of original silicone rubber is 450.6℃, while T_onset of silicone rubber added with 50wt% methyl MQ resin was 285.4℃. Meanwhile, the T_onset was 281.6℃, 283.8℃, 281.2℃, respectively, when the content of vinyl MQ resin reached 5wt%, 10wt% and 30wt%.This may result from the fact that MQ resin is a compact globoid which has a "core-shell" structure, making the viscosity of the procuring composite increase sharply when the filling amount of MQ resin was high. This would also make a small amount of hydrogen-containing silicone oil out of touch with vinyl group, so this part of hydrogen-containing silicone would not participate in the crosslinking network structure of silicone rubber. The residual hydrogen-containing silicone oil with a lower boiling point volatilizes at lower temperature, which would reduce the T_onset of silicone rubber when heated. When the temperature continued to increase, the decomposition velocity of original silicone rubber increased rapidly and reached the maximum of 0.38%/℃ at 511.1℃.

Nevertheless, the max decomposition velocity of all the silicone rubber filled with 50wt% content of MQ resin increased slowly, and it is apparently lower than that of original silicone rubber. Specially, the max decomposition velocity of silicone rubber filled with 50wt% MQ resin (containing 0wt% vinyl MQ resin) just reached the maximum of 0.13%/℃ at 526.7℃, and it decreased to 0.11%/℃ at 528.2℃ when the content of vinyl MQ resin increased to 5wt%. Nevertheless, the Vmax started to rise when the content of vinyl MQ resin continued to increase, and reached 0.27%/℃when the content of vinyl MQ resin reached 30wt%. As the temperature increased, the decomposition velocity of all the samples declined and decreased to 0 at nearly 800℃. The final carbon residue rate of original silicone rubber was about 47wt%, while that of silicone rubber filled with 50wt% MQ resin (containing 0wt% vinyl MQ resin) increased to 70wt%. As the content of vinyl MQ resin increased, carbon residue rate first increased but then decreased, which reached the maximum of 73wt% when the vinyl MQ resin content was 5wt%. This was probably because that MQ silicone itself has extremely high thermal resistance and a stable cross-linked network structure, thus leading to severe entanglement of silicone rubber molecular chains, which would limit the thermal movement of polysiloxane macromolecules and improved the thermal stability of silicone rubber. Furthermore, MQ resin has a higher proportion of Si element and can generate a higher proportion of inorganic Si-C and SiO₂ at high temperature, which would form a dense protective layer on the surface bringing in better heat resistance of silicone rubber and lower escape rate of small molecule^{[23, 24]}.Besides, vinyl MQ resin could be cross-linked in the whole network structure of silicone rubber through hydrosilylation when its content was low, reducing the generation of volatile small molecule siloxane ring during heating process. This also reduced the V_max and finally increased carbon residue rate. Nevertheless, excess vinyl MQ resin could not be cross-linked completely through hydrosilylation, which caused higher mass loss as vinyl group would generate free radicals leading to access the degradation at high temperature. Therefore, the V_max rose while carbon residue rate declined instead. Overall, silicone rubber filled with total 50wt% MQ resin (containing 5wt% vinyl MQ resin) was selected as the optimum prepared silicone rubber to modify the TPU.

Table 2

TGA characteristic parameters of different silicone rubber in nitrogen
Samples	T_onset(℃)	T_max(℃)	V_max(%/℃)
silicone rubber	450.6	511.1	0.38
silicone rubber added with 0wt% vinyl MQ resin	285.4	526.7	0.13
silicone rubber added with 5wt% vinyl MQ resin	281.6	528.2	0.11
silicone rubber added with 10wt% vinyl MQ resin	283.8	535.6	0.11
silicone rubber added with 30wt% vinyl MQ resin	281.2	538.2	0.27

3.2 FTIR results of TPU modified by silicone rubber

TPU modified with prepared silicone rubber was tested via FTIR to evaluate the possible chemical effect on TPU during the process of banburying. As depicted in Fig. 3, no distinct absorption peaks associated with polysiloxane were observed, likely attributable to the relatively low silicone rubber content. The absorption peaks at 3340 cm^− 1, 2900 cm^− 1, 1727 cm^− 1, 1543 cm^− 1 to 1350 cm^− 1, and 1090 cm^− 1 corresponded to N-H, C-H, C = O, N-C, and C-O groups, respectively, in the unmodified TPU. These absorption peaks were clearly retained in the TPU modified by the prepared silicone rubber, with minimal changes as the silicone rubber content increased, and no new absorption bands were discernible. Hence, we can conclude that there was negligible chemical reaction between the TPU and silicone rubber, indicating that their blending occurred predominantly at a physical interface.

3.3 thermal stability of TPU modified by silicone rubber

As depicted in Fig. 3a and Table 3a, the T_onset (onset temperature) of the original TPU was 347.3°C. However, when 1wt% silicone rubber was added to the TPU, the T_onset decreased to 342.3°C, exhibiting a 5.0°C reduction compared to the original TPU. This reduction can be attributed to the slight excess of hydrogen-containing silicone, which was necessary for ensuring the complete curing of the silicone rubber during the preparation process. Consequently, a very small amount of uncross-linked hydrogen-containing silicone was unavoidably present. Due to its low boiling point, this uncross-linked silicone tends to volatilize at lower temperatures, leading to a decrease in the T_onset of the TPU modified by the silicone rubber. Moreover, the modified TPU, prepared via the melt mixing method, caused the degradation of a small fraction of TPU, resulting in the generation of small-molecular by-products. This degradation process further contributed to the reduction in the T_onset of the modified TPU. When the silicone rubber content reached 2wt% and 3wt%, the T_onset of the TPU further decreased to 333.1°C and 336.1°C, respectively. This trend highlighted the higher presence of residual hydrogen-containing silicone oil with increasing amounts of the curing silicone rubber. Consequently, a larger proportion of volatilization occurred at lower temperatures, leading to a lower T_onset of the TPU. However, as the silicone rubber content reached 5wt%, the T_onset of the TPU increased slightly to 339.2°C. This suggests that the residual hydrogen-containing silicone oil had a limited impact on the T_onset of the TPU at this stage. This observation may be attributed to the poly-condensation reaction taking place within the hydrogen silicone oil under the influence of residual platinum catalyst during heating. As a result, even with increased content of silicone rubber, the proportion of volatile loss caused by the hydrogen-containing silicone oil remained limited.

The thermal decomposition of thermoplastic polyurethane (TPU) can be roughly divided into two stages. Initially, degradation started from the hard chain segment of the polyurethane, where the carbamate groups on the backbone chain begun to break at the C-O bond, generating isocyanates and polyol oligomers at temperatures ranging from 250°C to 350°C. These low-molecular-weight compounds volatilized as the temperature increases. As the temperature continued to rise, the second stage of thermal degradation begun, primarily occurring in the soft chain segment of the polyurethane. Here, the ether bond in polyether started to break and polyether or polyester as soft segments decomposed into monomers ^[25]. However, the hard chain segment did not completely decompose during the heating process. Due to the superposition of these two degradation stages, the thermal decomposition rate increased sharply and reached a maximum of 1.54%/°C at 375.3°C. When 1wt% silicone rubber was added to TPU, the decomposition velocity reached a maximum of 1.19%/°C at 380.5°C. Furthermore, as the content of silicone rubber increased to 5wt%, the maximum decomposition rate of TPU decreased to 0.84%/°C. Clearly, V_max (maximum decomposition rate) of all the modified TPUs is significantly lower than that of pure TPU. This could be attributed to the fact that the prepared silicone rubber had a thermally stable Si-O bond, which was not easily prone to generating free radicals, thereby providing excellent thermal stability. After being mixed, the silicone rubber dispersed in the thermoplastic polyurethane as particles, blocking the further generation of free radicals and reducing degradation caused by free radicals. Additionally, the silicone rubber formed inorganic Si-C and SiO₂, which created a dense protective layer on the surface, reducing thermal transmission at high temperatures. This, in turn, decreased the escape velocity of small molecules during TPU degradation, ultimately improving the thermal stability of TPU^[26,27].

Table 3 TGA characteristic parameters of TPU by different content of silicone rubber

a.in nitrogen

Samples	T_onset(℃)	T_max(℃)	V_max(%/℃)
Crude TPU	347.3	373.6	1.56
Crude TPU+1wt% silicone rubber	342.3	379.6	1.18
Crude TPU+2wt% silicone rubber	333.1	347.1	1.11
Crude TPU+3wt% silicone rubber	336.1	393.5	0.89
Crude TPU+5wt% silicone rubber	339.2	381.6	0.83

b. in air

Samples	T_onset(℃)	T_max(℃)	V_max(%/℃)
Samples	T_onset(℃)	max1 max2	max1 max2
Crude TPU	299.1	346.1 390.1		1.01 0.93
Crude TPU + 1wt% silicone rubber	317.3	348.5 406.5		0.87 0.96
Crude TPU + 2wt% silicone rubber	318.9	347.1 405.2		0.79 0.96
Crude TPU + 3wt% silicone rubber	320.9	349.1 401.1		0.79 0.80
Crude TPU + 5wt% silicone rubber	330.9	348.1 406.3		0.78 0.85

The thermal stability of TPU modified by silicone rubber in air was observed and characterized in Fig. 3b and Table 3b. The T_onset (onset temperature) of the original TPU was measured at 299.1℃, but when 1wt% of silicone rubber was added, the T_onset rose to 317.3℃. Furthermore, when the content of silicone rubber increased to 5wt%, the T_onset of the TPU reached 330.9℃. It is evident that the onset decomposition temperatures of all the samples improved in air, with the modified TPU exhibiting significantly higher temperatures compared to pure TPU. This enhancement in thermal stability can be attributed to the presence of silicone rubber, which acts as a protective layer on the surface of the TPU. This protective layer reduces the penetration of oxygen, which is known to accelerate the degradation of the TPU backbone chain during the initial degradation stage. As a result, the T_onset of the TPU modified by silicone rubber is improved. Similarly, when the experiments were conducted in a nitrogen atmosphere, the thermal decomposition of the thermoplastic polyurethane occurred in two stages. The first stage involved the degradation of the hard chain segment of the polyurethane, where isocyanates and polyol oligomers decomposed in the temperature range of 250℃ to 360℃. All the samples exhibited the first decomposition peak during this stage. Interestingly, as the content of silicone rubber increased, the T_max1 (temperature at which the first decomposition peak occurred) showed a slight increase. The decomposition rate of pure TPU during this stage was measured at 1.01%/℃, with the peak occurring at 346.1℃. This rate decreased as the content of silicone rubber increased. Finally, when the TPU was modified with 5wt% silicone rubber, the T_max1 decreased to 0.79%/℃ at 348.1℃. This decrease in T_max1 can be attributed to the enhanced decomposition of the TPU under oxygen, which generates an apparent decomposition peak. However, the presence of silicone rubber as a protective layer delays the occurrence of T_max1 by alleviating the influence of oxygen on degradation. In the second stage of decomposition, the soft chain segment of the polyurethane breaks down and decomposes into monomers. In the presence of air, these monomers further oxidize into carbon dioxide and water. It is important to note that the protective function of silicone rubber is weakened during this stage, as it is also oxidized, resulting in the formation of a less effective inorganic layer. As a result, while the T_max2 (temperature at which the second decomposition peak occurred) showed a slight increase with 5wt% silicone rubber content, the V_max2 (decomposition rate at the second peak) remained fairly consistent among all the samples.

3.3 Thermal stability of aged TPU modified by silicone rubber

All TPU samples were subjected to a thermal oxygen aging process, where they were placed in air at a temperature of 100℃ for seven days before undergoing thermogravimetric analysis. Results presented in Fig. 4 and Table 4 show that the initial decomposition temperature of pure TPU after aging was 318.3℃, approximately 30℃ lower than that of its original form. Moreover, the initial decomposition temperature of TPU with a 1wt% added silicone rubber after aging was 317.3℃, which was about 25℃ lower than the original TPU. The initial thermal decomposition temperature of TPU modified by 2wt%, 3wt%, and 5wt% silicone rubber was reduced by 15℃, 15℃, and 8℃, respectively, after thermal oxygen aging. This decrease can be attributed to the small molecules generated during the aging process that escape at a lower temperature, causing a decrease in the initial thermal decomposition temperature. However, it can be observed that the decrease in the T_onset of thermal oxygen aged TPU reduces as the content of silicone rubber increases. This is because TPU generates free radicals during aging, and the dispersed silicone rubber inevitably migrates to the surface, resulting in a dense protective layer with higher thermal stability that reduces oxygen penetration and heat transfer and thus, the production of free radicals. During the process of thermogravimetric analysis, the dense protective layer formed could not block the heat transfer effectively, resulting in a decline in T_max and V_max values of pure TPU after aging. Specifically, after thermal oxygen aging, the T_max and V_max of pure TPU were recorded as 361.9℃ and 1.39%℃, respectively, both lower than those of pure TPU in its original form. However, all T_max of the modified TPU were higher than pure TPU, even though they all decreased after aging. Meanwhile, the V_max values of these modified TPU were lower than those of pure TPU, indicating a significant improvement in the thermal stability of TPU with the addition of silicone rubber.

Table 4

TGA characteristic parameters of aged TPU modified by silicone rubber in nitrogen.
Samples	T_onset(℃)	T_max(℃)
Crude TPU	318.3	361.9	1.42
Crude TPU + 1wt% silicone rubber	317.3	364.8	1.20
Crude TPU + 2wt% silicone rubber	317.5	363.2	1.21
Crude TPU + 3wt% silicone rubber	315.1	357.1	0.89
Crude TPU + 5wt% silicone rubber	328.9	379.1	1.01

3.5 SEM of TPU modified by silicone rubber

As is shown in Fig. 5, compared with pure TPU, white spherical silicone rubber dispersed in TPU which was modified via banburying method. As the content of silicone rubber increased, it became denser but sill dispersed evenly. Consequently, the modification method used in this study effectively enhances the dispersion of silicone rubber in TPU. This outcome can be attributed to the initial fluidity of the composite, allowing for uniform dispersion within the TPU matrix during the banburying process. As a result, molecular entanglement between TPU and silicone rubber is formed, increasing their compatibility. Subsequently, with prolonged heating time, the procuring silicone rubber undergoes gradual cross-linking, resulting in the formation of a network structure, yielding modified TPU.

3.6 Tensile strength and elongation at break of TPU modified by silicone rubber

As shown in Fig. 6a(all the standard deviation of tensile strength dataset is under 0.19 and all the standard deviation of elongation at break dataset is under 8.10), compared with original TPU, tensile strength of TPU added with 1wt% silicone rubber increased 0.2MPa and then increased 0.6MPa when the content of silicone rubber reached 3wt%. This enhancement can be attributed to the high filler content of methyl MQ and vinyl MQ resin within the silicone rubber, which exhibited a compact spherical structure known as the “core-shell” configuration. The spherical core possessed a Si-O chain with a high degree of crosslinking, whereas the spherical shell consists of organic groups ^[30]. Consequently, the compatibility between MQ resin and liquid silicone rubber improved, and MQ resin would function as a physical reinforcement through molecular entanglement and intermolecular interaction. Additionally, vinyl MQ resin would react with the surrounding liquid silicone rubber, resulting in a higher level of crosslinking and uniformed stress buffering along numerous molecular chains. As a result, the prepared silicone rubber, when mixed with TPU, formed an island phase uniformly dispersed throughout the continuous TPU phase. The intermolecular forces generated between silicone rubber and TPU chains created a net-like cross-linking structure. This evenly-distributed silicone rubber acted as a physical connection point, effectively dissipating forces and reducing local stress concentration when the modified TPU undergoes stretching. Thus, the modified TPU showed increased resistance to tensile stress ^[31]. Meanwhile, the elongation deformation of the TPU chain exhibited a tendency to align as a cohesive unit, thereby delaying the occurrence of molecular chain slippage and localized fracture, ultimately contributing to enhanced durability. Consequently, the tensile strength and elongation at break of the modified TPU material were substantially improved. However, the tensile strength of the modified TPU declined when the content of incorporated silicone rubber reached 5wt%. This can likely be attributed to the significantly lower tensile strength of the silicone rubber compared to that of TPU, and the propensity of the silicone rubber to reunite upon increasing its concentration. Consequently, the reunited silicone rubber points would fracture under relatively lower stretching stress, resulting in TPU rupture and diminished tensile strength. Nevertheless, the elongation at break of the modified TPU continued to increase, further validating the synchronized elongation of the TPU molecular chains and the similar behavior observed in the chain slippage phenomenon. Consequently, the overall deformation process was extended, leading to improved elongation at break.

After heating in air for 7days at 100℃, the modified polyurethane samples were subjected to tensile testing, and the results are shown in Fig. 6b(all the standard deviation of tensile strength dataset is under 0.14 and all the standard deviation of elongation at break dataset is under 13.92). The tensile strength of pure TPU decreased to 11.15MPa after aging, while the sample with 1% prepared silicone rubber increased to 11.35MPa. As the content of prepared silicone rubber rose, the tensile strength of TPU continued to increase and reached its maximum value of 12.57MPa when the prepared silicone rubber reached 3wt%. Nevertheless, with further increase in the amount of prepared silicone rubber, the tensile strength of TPU decreased. Meanwhile, the elongation at break of the aged TPU increased consistently with the increase in the content of prepared silicone rubber. The pure TPU exhibited an elongation at break of 305%, which increased to 372% when the content of prepared silicone rubber reached 5wt%. It can be concluded that the tensile strength and elongation at break of aged TPU are both lower than non-aged TPU due to the degradation of TPU during aging process, while the two indicators of TPU demonstrate consistent changes in trends before and after aging. However, there is a particular detail where the tensile strength of the aged TPU sample with 5wt% prepared silicone content remains at a high level while the non-aged TPU with 5wt% prepared silicone rubber declined significantly. This is due to the fact that a small amount of silicone rubber migrated to the TPU surface during aging process, which slowed down the permeation of moisture and oxygen in the air and reduced the aging degree of TPU.

TPU was mixed with procuring silicone rubber composite at high temperature via banburying method to prepare modified TPU, which was proved to be a feasible way. The TGA results showed that the procuring silicone rubber composite had superior thermal stability and brought in positive effect on the thermal stability of TPU in both nitrogen and air atmosphere. Besides, modified TPU still remained an acceptable level of thermal stability after thermal oxygen aging. SEM results showed that banburying method enabled the excellent dispersion of silicone rubber in TPU matrix. Tensile strength of modified TPU increased gradually until the content of silicone rubber reached 3wt% while elongation at break increased continuously. Besides, the mechanical properties of the modified TPU still demonstrated the same change in trends after thermo-oxidative aging.

Acknowledgments

The authors would be grateful to the financial support by the Natural Science Foundation of Guangdong Province (Grant No.2021A1515011708), Science and Technology Planning Project of Guangzhou (Grant No. 202102080198).Meanwhile, I deeply appreciate the valuable advice on the manuscript offered by my colleagues in Institute of Resources Uililization and Rare Earth Development, Guangdong Academy of Sciences.

Conflict of Interest

The authors declare that they have no conflict of interest.

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Reviewers invited by journal
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Study on the thermal stability of TPU modified by silicone rubber highly filled with MQ silicone resin

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Abstract

Figures

1. Introduction

2. Experimental sections

2.1Materials:

2.2Experiment:

2.3Measurements

2.3.1Thermogravimetric analysis (TGA)

2.3.2 Fourier transform infrared spectroscopy (FTIR)

2.3.3Scanning electron microscope (SEM)

2.3.4Tensile strength and elongation at break test

3. Results and discussion

4. Conclusion

Declarations

Acknowledgments

Conflict of Interest

References

Status:

Version 1