Major Project (2nd Draft)

Preparation of silica-supported 2-mercaptobenzimidazole and its antioxidative behavior in styrene-butadiene rubber

Zhong et al. (2014) conducted a study to prepare silica-supported 2-mercaptobenzimidazole (SiO₂-s-MB) as a novel antioxidant in rubber and to investigate its properties and application in styrene-butadiene rubber (SBR). SiO₂-s-MB was synthesized by the reaction of 2-mercaptobenzimidazole (MB) with chlorosilane-modified silica (m-SiO₂). SiO₂-s-MB was then analyzed by Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA) to confirm the supporting of antioxidant MB onto the surface of silica particles. SiO₂-s-MB particles were filled in SBR and vulcanized to obtain SBR composites. Confirmation of dispersion of SiO₂-s-MB in SBR matrix was performed by Scanning electron microscope (SEM) and compared to the results of SiO₂ in SBR matrix. The oxidative efficiency of SiO₂-s-MB during short-term oxidation was determined using oxidative reduction time (OIT) method. The change of mechanical properties before and after aging was used to evaluate the thermal oxidative stability of SBR composites. The results showed that MB has been successfully bonded onto the silica surface through chemical linkages between chlorosilane on the m-SiO₂ and MB. For SBR composites, the SiO₂-s-MB particles were homogeneous dispersed in SBR matrix and no agglomeration of SiO₂-s-MB particles was observed. The oxidative efficiency of SBR/SiO₂-s-MB was much higher than that of SBR/m-SiO₂/MB due to harder migratory and volatile of MB from rubber matrix. Additionally, mechanical properties retention of SBR/SiO₂-s-MB was significantly improved comparing to low molecular MB. The researcher suggested that SiO₂-s-MB might be used as a rubber antioxidant with high performance and environmentally friendly characteristic due to its lower migration and volatility, and homogeneous dispersion in rubber matrix.

            This study provides a novel antioxidant in rubber with high performance and environmentally friendly. However, there are some limitations.

1)               The researcher did not study the oxidative efficiency and mechanical property retention of pure SBR as reference. The researcher might miss some effects which related to pure rubber. Normally, many studies in polymer nanocomposite field are necessary to compare their results with pure polymer as reference. Kongsinlark et al. (2012) study the effect of heat aging on mechanical property retention of natural rubber (NR) composites filled with polyisoprene (PIP)-SiO₂ in comparison with pure NR.  It was found that PIP-SiO₂ could enhanced the improvement of the interaction between SiO₂ and NR resulting in an increase in mechanical property retention comparing with pure NR.

2)         This study did not investigate the thermal properties of composite materials, such as glass transition temperature (T_g) and decomposition temperature (T_id and T_max), which is important data to select the appropriate materials using in various application. All polymer composites should be analyzed because adding of filler or antioxidant in the polymer matrix significantly affect the thermal properties and stability of materials (Grassie & Scott, 1988).

3)         This study used only SEM to confirm the homogeneous dispersion of SiO₂-s-MB in SBR matrix. The researcher might have bias when selecting part of sample to analyze because some part of composite may obtained the agglomeration of SiO₂-s-MB. One of common methods to observe the distribution of filler in polymer matrix is dynamic light scattering (DLS) technique. Using a combination of SEM and DLS is more effective for investigation of SiO₂-s-MB distribution in SBR matrix than using one of these methods alone (Kongsinlark et al., 2012).

            The strength of this study is that the confirmation of supporting of MB onto silica surface used 4 techniques to analyze. These methods are widely acceptable for research in the polymer nanocomposite field and are efficiency technique to specify functional groups and composition of material. Furthermore, this novel rubber antioxidant have possible potential for future applications, which could suppress the migration and volatility being major problem for low molecular weight antioxidant resulting in high performance and environmentally friendly.

References

Grassie, N., & Scott, G. (1988). Polymer degradation and stabilisation: CUP Archive.

Kongsinlark, A., Rempel, G. L., & Prasassarakich, P. (2012). Synthesis of monodispersed polyisoprene–silica nanoparticles via differential microemulsion polymerization and mechanical properties of polyisoprene nanocomposite. Chemical Engineering Journal, 193–194, 215-226.

Zhong, B., Shi, Q., Jia, Z., Luo, Y., Chen, Y., & Jia, D. (2014). Preparation of silica-supported 2-mercaptobenzimidazole and its antioxidative behavior in styrene-butadiene rubber. Polymer Degradation and Stability, 110, 260-267.

Major Project (1st Draft)

Preparation of silica-supported 2-mercaptobenzimidazole and its antioxidative behavior in styrene-butadiene rubber

Zhong et al. (2014) conducted a study to prepare silica-supported 2-mercaptobenzimidazole (SiO₂-s-MB) as a novel antioxidant in rubber and to investigate its properties and application in styrene-butadiene rubber (SBR). SiO₂-s-MB was synthesized by the reaction of 2-mercaptobenzimidazole (MB) with chlorosilane-modified silica (m-SiO₂). SiO₂-s-MB was then analyzed by Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA) to confirm the supporting of antioxidant MB onto the surface of silica particles. SiO₂-s-MB particles were filled in SBR and were vulcanized to obtain SBR composites. Confirmation of dispersion of SiO₂-s-MB in SBR matrix was performed by Scanning electron microscope (SEM) and compared to the results of SiO₂ in SBR matrix. The oxidative efficiency of SiO₂-s-MB during short-term oxidation was determined using oxidative reduction time (OIT) method. The change of mechanical properties before and after aging was used to evaluate the thermal oxidative stability of SBR composites. The results showed that MB has been successfully bonded onto the silica surface through chemical linkages between chlorosilane on the m-SiO₂ and MB. For SBR composites, the SiO₂-s-MB particles were homogeneous dispersed in SBR matrix and no agglomeration of SiO₂-s-MB particles was observed. The oxidative efficiency of SBR/SiO₂-s-MB was much higher than that of SBR/m-SiO₂/MB due to harder migratory and volatile of MB from rubber matrix. Additionally, mechanical properties retention of SBR/SiO₂-s-MB was significantly improved comparing to low molecular MB. The researcher suggested that SiO₂-s-MB might be used as a rubber antioxidant with high performance and environmentally friendly characteristic due to its lower migration and volatility, and homogeneous dispersion in rubber matrix.

            This study provides a novel antioxidant in rubber with high performance and environmentally friendly. However, there are some limitation.

1)               The researcher did not study the oxidative efficiency and mechanical property retention of pure SBR as reference. The researcher might miss some effect related to pure rubber. Normally, many research study in polymer nanocomposite field have to compare their results with pure polymer as reference. Kongsinlark et al. (2012) study the effect of heat aging on mechanical property retention of natural rubber (NR) composites filled with polyisoprene (PIP)-SiO₂ in comparison with pure NR.  It was found that PIP-SiO₂ could enhanced the improvement of the interaction between SiO₂ and NR resulting in an increase in mechanical property retention comparing with pure NR.

2)         This study did not investigate the thermal properties, such as glass transition temperature (T_g) and decomposition temperature (T_id and T_max), of composite materials which is important data to select the appropriate materials using in various application. All polymer composites should be analyzed because adding of filler or antioxidant in the polymer matrix significantly affect the thermal properties and stability of materials (Grassie & Scott, 1988).

3)         This study used only SEM to confirm the homogeneous dispersion of SiO₂-s-MB in SBR matrix. The researcher might have bias when selecting part of sample to analyze because some part of composite may obtained the agglomeration of SiO₂-s-MB. One of common method to observe the distribution of filler in polymer matrix is dynamic light scattering (DLS) technique. Using a combination of SEM and DLS is more effective for investigation of SiO₂-s-MB distribution in SBR matrix than using one of these method alone (Kongsinlark et al., 2012).

            The strength of this study is that the confirmation of supporting of MB onto silica surface used 4 techniques to analyze. These method are widely acceptable for research in the polymer nanocomposite field and are efficiency technique to specify functional groups and composition of material. Furthermore, this novel rubber antioxidant have possible potential for future applications, which could suppress the migration and volatility being major problem for low molecular weight antioxidant resulting in high performance and environmentally friendly.

References

Grassie, N., & Scott, G. (1988). Polymer degradation and stabilisation: CUP Archive.

Kongsinlark, A., Rempel, G. L., & Prasassarakich, P. (2012). Synthesis of monodispersed polyisoprene–silica nanoparticles via differential microemulsion polymerization and mechanical properties of polyisoprene nanocomposite. Chemical Engineering Journal, 193–194, 215-226.

Zhong, B., Shi, Q., Jia, Z., Luo, Y., Chen, Y., & Jia, D. (2014). Preparation of silica-supported 2-mercaptobenzimidazole and its antioxidative behavior in styrene-butadiene rubber. Polymer Degradation and Stability, 110, 260-267.

Minor Project

Minor Project

My research question is whether synthesizing core-shell structured polybutadiene (PB)-SiO₂ nanoparticles via differential microemulsion polymerization can improve the compatibility of silica in PB matrix. The combination of silica with polymers can be applicable to a wide variety application because they provide improved mechanical, electrical and thermal properties over pure polymers.

Researchers who have looked at this subject are Guan et al. (2011) and Zhong et al. (2014). They exhibited that properties of polymer were improved by filling silica in the polymer matrix.

Guan et al. (2011) reported that the hydrogenated nitrile butadiene rubber (HNBR) composites filled with fumed silica were prepared to improve their ablation performance and thermal stability. However, the applications of this composite were largely limited at high silica loading, due to the agglomeration of silica particles.

Zhong et al. (2014) reported that silica-supported 2-mercaptobenzimidazole (SiO₂-s-MB) had high antioxidative efficiency and low color contamination, migration and volatility could be used as an environmentally friendly rubber antioxidant to improve thermal oxidative stability of styrene butadiene rubber (SBR) composite.

Debate centers on the basic issue of inferior compatibility and less stability between the polymer matrix and silica at high silica loading due to the large quantity of hydroxyl groups on the silica surface and the high surface energy and polarity.

There is still work to be done on encapsulation of silica with polymer to improve the compatibility and dispersion of silica in polymer matrix. Thus, silica dispersion and performance of the polymer composite will be improved.

My research is closest to that of Zhong et al. because I will use their technique to modify silica surface with silane coupling agent that will provide vinyl group on the silica surface. The vinyl group can react with butadiene monomer molecule to generate PB on the silica surface.

Hopefully, my contribution to the debate will be to obtain the new composite particle of silica core and PB shell that will enhance compatibility and dispersion of silica in PB matrix, reduce filler-filler interaction and achieve homogeneity of silica in PB.

Reference List

Guan, Y., Zhang, L., Zhang, L., & Lu, Y. (2011). Study on ablative properties and mechanisms of hydrogenated nitrile butadiene rubber (HNBR) composites containing different fillers. Polymer Degradation and Stability, 96, 808-817.

Zhong, B., Shi, Q., Jia, Z., Luo, Y., Chen, Y., & Jia, D. (2014). Preparation of silica-supported 2-mercaptobenzimidazole and its antioxidative behavior in styrene-butadiene rubber. Polymer Degradation and Stability, 110, 260-267.

Assignment2: Writing an introduction

SYNTHESIS OF POLYBUTADIENE-SILICA NANOPARTICLES VIA DIFFERENTIAL MICROEMULSION POLYMERIZATION

by

Thanyaporn Tancharernrat

Stage 1:   Polymer nanocomposites have drawn a great deal of interest in recent years because these materials possess high potential to achieve great property improvement by adding a small amount of nanofillers in the polymer matrices. The combination of nanoscale inorganic species (filler) with organic polymers has highly efficiency for future applications. These materials are widely used in automotive, aerospace, construction, and electronic industries because they provide improved mechanical (e.g., stiffness, strength), electrical, thermal and physical properties over pure polymers (Chen & Feng, 2009). One of the most common inorganic systems is nanosilica that has many functional properties and effective reinforcement. It was widely used in colloidal products, paints, catalysis, chromatographic separation, rubber and plastic reinforcement due to silica is chemically inert and optically transparent (Zhang et al., 2004; Sun et al., 2005).

Stage 2:   Many previous studies have reported on improved properties of polymer filled with nanosilica. According to Zhong et al. (2014), silica-supported 2-mercaptobenzimidazole (SiO₂-s-MB) had high antioxidative efficiency and low color contamination, migration and volatility could be used as an environmentally friendly rubber antioxidant to improve thermal oxidative stability of styrene butadiene rubber (SBR) composite. Guan et al. (2011) reported the hydrogenated nitrile butadiene rubber (HNBR) composites filled with fumed silica was prepared to improve their ablation performance and thermal stability. According to Kongsinlark et al. (2012), polyisoprene (PIP)–SiO₂ nanoparticles produced with a size of 20–60 nm and have been used as an effective nano-filler in natural rubber (NR) latex. The NR filled with PIP-SiO₂ clearly presented an improvement in the storage modulus, tensile strength, modulus at 300% strain and anti-aging properties. In addition, Chuayjuljit et al. (2010) reported that hybrid nanoparticles of polystyrene (PS)-silica were prepared by grafting polymerization and the resulting particles were used as a filler in the NR latex resulting in improved tensile strength, modulus at 300% strain and flammability of NR at low PS-silica loading of 3-9 parts per hundred rubber (phr).

Stage 3:   However, the difficulties as an access to well dispersed silica in rubber matrix are due to  the large quantity of hydroxyl groups on the surface of the nanosilica and the high surface energy and porality, resulting in inferior compatibility and less stability between the rubber matrix and nanosilica; thus severe agglomeration and weak rubber-filler interaction occured (Kim et al., 2010). The great advantage provided by nanosilica can only be achieved if the particles are finely dispersed in the polymer matrix. Encapsulation is regarded as being of major importance since it offers interesting potential applications in different fields. Thus, encapsulation of nanosilica with polymer can improve the compatibility of nanosilica in the rubber matrix resulting in an improvement of filler dispersion and performance of the rubber composite.

Stage 4&5:  In this research work, new approach of the differential microemulsion polymerization method is applied to polybutadiene (PB)-silica. To obtain the core-shell morphology, the composite nanoparticle is designed to have core nanosilica and shell polybutadiene. These composites are desired not only to obtain much smaller diameter (smaller than 50 nm) but also to exhibit a narrow size distribution and thus resulting in reduced nanosilica aggregation at a low level of surfactant. The influence of silica loading, surfactant concentration, monomer to water ratio and initiator concentration on monomer conversion, grafting efficiency, silica encapsulation efficiency and particle size was also investigated. Thus, this novel PB-SiO₂ nanocomposite can be used as a nanoreinforcing filler and thermal and ozone stabilizer for NR composites.

Assignment1: Citation

Preparation of silica-supported 2-mercaptobenzimidazole 

and its antioxidative behavior in styrene-butadiene rubber

Abstract

A novel type of rubber antioxidant, silica-supported 2-mercaptobenzimidazole (SiO2-s-MB), was prepared by reacting 2-mercaptobenzimidazole (MB) with chlorosilane-modified silica (m-SiO2). Raman spectroscopy, FT-IR, XPS and TGA confirmed that MB was chemically bonded onto the surfaces of silica particles. SEM observation showed that SiO2-s-MB was homogeneously dispersed in the styrenebutadiene rubber (SBR) matrix. Based on the measurement of oxidation induction time (OIT) of SBR/SiO2-s-MB and SBR/m-SiO2/MB composites containing equivalent antioxidant components, it was found that the antioxidative efficiency of SiO2-s-MB was superior to that of the corresponding low molecular MB. By determining the changes of tensile strength, elongation at break and crosslinking density of SBR composites during long-term accelerated aging, it was shown that the thermal oxidative stability of SBR/SiO2-s-MB composites was much higher than that of SBR/m-SiO2/MB composites. Furthermore, the color contamination, migration and volatility of SiO2-s-MB were lower than those of MB, indicating that SiO2-s-MB is environmentally friendly.

Reference

Zhong, B., Shi, Q., Jia, Z., Luo, Y., Chen, Y., & Jia, D. (2014). Preparation of silica-supported 2-mercaptobenzimidazole and its antioxidative behavior in styrene-butadiene rubber. Polymer Degradation and Stability, 110, 260-267.

Results and findings

-Silica-supported 2-mercaptobenzimidazole (SiO2-s-MB) as a novel type of rubber antioxidant was prepared by reacting 2-mercaptobenzimidazole (MB) with chlorosilane-modified silica (m-SiO2).

- MB was chemically bonded onto the surfaces of silica particles.

- SiO2-s-MB was homogeneously dispersed in the styrenebutadiene rubber (SBR) matrix.

- The antioxidative efficiency of SiO2-s-MB was superior to that of the corresponding low molecular MB.

- The thermal oxidative stability of SBR/SiO2-s-MB composites was much higher than that of SBR/m-SiO2/MB composites.

- The color contamination, migration and volatility of SiO2-s-MB were lower than those of MB, indicating that SiO2-s-MB is environmentally friendly.

Citations

- According to Zhong et al. (2014), silica-supported 2-mercaptobenzimidazole (SiO2-s-MB) which was successfully prepared by reacting 2-mercaptobenzimidazole (MB) with chlorosilane-modified silica (m-SiO2) by chemical bonding onto the m-SiO2 surface was homogeneously dispersed in the styrenebutadiene rubber (SBR) matrix.
 

- Zhong et al. (2014) reported that silica-supported 2-mercaptobenzimidazole (SiO2-s-MB) had high antioxidative efficiency and low color contamination, migration and volatility could be used as an environmentally friendly rubber antioxidant to improve thermal oxidative stability of styrenebutadiene rubber (SBR) composite.