DESC:FIELD
The present disclosure relates to polybutadiene nanocomposites.
DEFINITIONS
As used in the present disclosure, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used indicate otherwise.
Polymer nanocomposite : Polymer nanocomposite consists of a polymer or co-polymer having nanoparticles or nanofillers dispersed in the polymer matrix.
Tensile strength: Tensile strength is a measure of the force required to pull a material such as rope, wire, or a structural beam to the point where it breaks.
Modulus : The modulus is a measure of the stiffness of the material, or it is the amount of force needed to deform a material by a set amount. Modulus can be measured in any mode of deformation, i.e., tension (stretching), compression, (crushing), flexing, (bending), or torsion (twisting).
BACKGROUND
Polymer nanocomposites, prepared by dispersing nanofillers in polymer matrix, are widely used in diverse applications ranging from automotive industry/products to household applications. The development of polymer nanocomposites is of great advantage to the rubber industry, due to the improved physical properties of nanocomposites, such as tensile strength. For preparing the polymer composites, the conventional fillers are required in large amounts. By using smaller amounts of nanofillers for preparing nanocomposites, the performance and properties of the nanocomposites can be tailored at low cost.
Polymer nanocomposites can be prepared by various methods such as melt intercalation and solution blending. These processes have drawbacks as the nanoparticles are unevenly/poorly dispersed in the polymer matrix. The poor dispersion of nanofillers leads to weak intercalation of nanofillers in the polymeric material resulting in poor mechanical properties.
There is, therefore felt a need to provide a method for preparation of polymer nanocomposites that overcome the problem of poor dispersion and/or weak intercalation.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
An object of the present disclosure is to provide a method for preparing polybutadiene nanocomposites.
Still another object of the present disclosure is to provide polybutadiene nanocomposites having improved tensile strength at lower concentration of nanofillers.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure provides a method comprising a step of preparing a polybutadiene nanocomposite, which includes a step of embedding a nanofiller in a polybutadiene during the process of polymerization of 1,3-butadiene.
The present disclosure provides an in-situ method for preparing the polybutadiene nanocomposite. The method comprises mixing a predetermined amount of 1,3-butadiene with at least one first fluid medium to obtain a feed. The feed, at least one nanofiller, a catalyst composition, and at least one second fluid medium are introduced into a reactor to obtain a reaction mass. The reaction mass is stirred under inert atmosphere, at a temperature in the range of 50 °C to 80 °C, for a time period in the range of 1 hour to 5 hours to polymerize 1,3-butadiene to obtain a first mixture. The polymerization is terminated by adding a terminating agent to the first mixture to obtain a second mixture comprising the polybutadiene nanocomposite. The polybutadiene nanocomposites are separated from the second mixture, followed by drying at a temperature in the range of 30 °C to 60 °C, for a time period in the range of 4 hours to 8 hours to obtain the polybutadiene nanocomposites.
The first fluid medium and second fluid medium are independently selected from the group consisting of heptane, cyclohexane, hexane, toluene, benzene and ethylbenzene. The nanofiller is at least one selected from the group consisting of carbon nanotubes and nanosilica.
The catalyst composition comprises a catalyst component, a co-catalyst component and a promoter.
The catalyst component is at least one selected from the group consisting of cobalt octoate, nickel naphthenate and titanium supported on MgCl2.
The co-catalyst component is at least one selected from the group consisting of triethylaluminum (TEAL), tridecylaluminum, tri-n-butylaluminum, tri-isopropylaluminum, tri-isoprenylaluminum, tri-isobutylaluminum, ethyl aluminum sesquichloride, diethylaluminum chloride (DEAC), di-isobutyl aluminum chloride, triphenylaluminum, tri-n-octylaluminum and tri-n-decylaluminum.
In accordance with an embodiment of the present disclosure, the promoter is at least one selected from the group consisting of water, boron trifluoride, glycerol and methanol.
The terminating agent is at least one selected from the group consisting of phosphate of polyoxyethylene alkyl phenyl ether (PPA), 0.5% of di-tertbutyl-para-cresol (DTBPC) in methanol, and combinations thereof.
The weight ratio of the catalyst component to 1,3-butadiene is in the range of 1:100 to 1:1000.
The weight ratio of the co-catalyst component to the catalyst component is in the range of 5:1 to 50:1.
The ratio of the promoter to the co-catalyst component is in the range of 1:1 to 1:5.
The polybutadiene nanocomposites are characterized by tensile strength in the range of 1.8 to 3.6 MPa. The polybutadiene nanocomposites of the present disclosure comprises the nanofiller embedded therein during the stage of polymerization from 1,3-butadiene.
DETAILED DESCRIPTION
The development of polybutadiene nanocomposite is of great advantage to the rubber industry, due to the improved physical properties of nanocomposite, such as tensile strength.
The present disclosure relates to an in-situ method for the preparation of polybutadiene nanocomposites. The polybutadiene nanocomposites synthesized using the method of the present disclosure possess enhanced tensile strength.
In accordance with one aspect of the present disclosure, there is provided an in-situ method for preparing the polybutadiene nanocomposite from 1,3-butadiene, the method comprises the following steps:
Initially, 1,3-butadiene is mixed with a first fluid medium to obtain a feed having a predetermined concentration of 1,3-butadiene.
The predetermined concentration of 1,3-butadiene in the feed is in the range of 18% to 22% w/w of the first fluid medium.
In accordance with the embodiments of the present disclosure, the first fluid medium is at least one selected from the group consisting of heptane, cyclohexane, hexane, toluene, benzene, and ethylbenzene.
In accordance with one embodiment of the present disclosure, 1,3-butadiene is mixed with toluene, at a temperature in the range of 2°C to 7°C, to obtain the feed.
In accordance with another embodiment of the present disclosure, 1,3-butadiene is mixed with a mixture of n-heptane:toluene (50:50), at a temperature in the range of 2°C to 7°C to obtain the feed.
At higher temperature, the solubility of 1,3-butadiene in the fluid medium tends to decrease.
Prior to mixing, 1,3-butadiene stream can be purified by passing it through a solution of triethylaluminum in the first fluid medium, and resultant stream can be further passed through molecular sieves.
The next step involves introducing the feed, at least one nanofiller, a catalyst composition, and at least one second fluid medium into a reactor to obtain a reaction mass.
In accordance with the embodiments of the present disclosure, the nanofiller is at least one selected from the group consisting of carbon nanotubes, and nanosilica.
In accordance with embodiments of the present disclosure, the catalyst composition comprises a catalyst component, a co-catalyst component, and a promoter.
In accordance with the embodiments of the present disclosure, the catalyst component is at least one selected from the group consisting of cobalt octoate, nickel naphthenate, and titanium supported on MgCl2.
In accordance with the embodiments of the present disclosure, the co-catalyst component is at least one selected from the group consisting of triethylaluminum (TEAL), tridecylaluminum, tri-n-butylaluminum, tri-isopropylaluminum, tri-isoprenylaluminum, tri-isobutylaluminum, ethyl aluminum sesquichloride, diethylaluminum chloride (DEAC), di-isobutyl aluminum chloride, triphenylaluminum, tri-n-octylaluminum and tri-n-decylaluminum.
In one embodiment, the catalyst composition comprises nickel naphthenate as the catalyst component, triethylaluminum (TEAL) as co-catalyst component and boron trifluoride ether complex as the promoter.
In another embodiment, the catalyst composition comprises cobalt octoate as the catalyst component, diethylaluminum chloride (DEAC) as the co-catalyst component and boron trifluoride ether complex (BRF) as the promoter.
The amount of diethylaluminum chloride (DEAC) can be 7.5 millimoles per hundred grams of 1,3-butadiene and the promoter is selected from the group consisting of water, boron trifloride, glycerol, and methanol.
Further, the reaction mass is stirred under an inert atmosphere, at a temperature in the range of 50 °C to 80 °C, for a time period in the range of 1 hour to 5 hours to polymerize 1,3-butadiene in the reaction mass to obtain a first mixture. An inert atmosphere is used to prevent oxides being formed during the polymerization reaction. Advantageously antioxidants and antiozonants may also be used.
The polymerization is terminated by adding a terminating agent to the first mixture to obtain a second mixture comprising the polybutadiene nanocomposites. The terminating agent can be at least one selected from the group consisting of phosphate of polyoxyethylene alkyl phenyl ether (PPA), 0.5% of di-tertbutyl-para-cresol (DTBPC) in methanol, and combinations thereof.
In accordance with one embodiment of the present disclosure, the terminating agent is 0.5% of di-tertbutyl-para-cresol (DTBPC) in methanol.
In accordance with another embodiment of the present disclosure, the terminating agent is a mixture of phosphate of polyoxyethylene alkyl phenyl ether (PPA) and 0.5% of di-tertbutyl-para-cresol (DTBPC) in methanol.
In accordance with one embodiment of the present disclosure, the polymerization is terminated either by adding phosphate of polyoxyethylene alkyl phenyl ether (PPA), followed by coagulation with methanol containing 0.5% of di-tert-butyl-para-cresol in methanol or by adding 0.5% solution of di-tert-butyl-para-cresol in methanol to the reaction mixture.
The next step involves separating polybutadiene nanocomposites from the second mixture. The separation can be achieved by any suitable separation technique such as filtration, evaporation and decantation.
Typically, the polybutadiene nanocomposites are dried at a temperature in the range of 40 °C to 80 °C, for a time period in the range of 4 hour to 8 hours to obtain the dried polybutadiene nanocomposites. Alternatively, drying is carried out at room temperature, followed by drying under reduced pressure at 30 to 60 °C for 4 to 8 hours.
Compositing of nanofillers with polybutadiene is an exothermic reaction. When carbon nanotubes (CNT) are used as nanofillers, the reaction isotherm more or less remains same up to CNT loading of 0.8 phr. However, for CNT loading beyond 2 phr, negative temperature difference is observed. On the other hand, when nanosilica is used as the nanofiller, it is observed that the reaction isotherm and the reaction time increases. However, with the increasing concentration of nanosilica, the exothermicity decreases.

Typically, the first fluid medium used for mixing with 1,3-butadiene to obtain feed, is anhydrous and purified. While mixing 1,3-butadiene and the first fluid media, the temperature of the first fluid medium is in the range of 2°C to 7°C. The concentration of 1,3-butadiene in the first fluid media is calculated gravimetrically by determining the weight gain of the pre-weighed first fluid medium.
In accordance with the embodiments of the present disclosure, the weight ratio of the catalyst component to 1,3-butadiene is in the range of 1:100 to 1:1000.
In accordance with the embodiments of the present disclosure, the weight ratio of the co-catalyst component to the catalyst component is in the range of 5:1 to 50:1.
In accordance with the embodiments of the present disclosure, the ratio of the promoter to the co-catalyst component is in the range of 1:1 to 1:5.
In accordance with one embodiment of the present disclosure, the amount of cobalt octoate, used for the polymerization is 0.02 millimoles per hundred grams of 1,3-butadiene.
In accordance with one embodiment of the present disclosure, polymerization is carried out using Buchi reactor provided with inert gas line, port for charging raw materials, thermocouple, bottom outlet, and external heating/cooling jacket system.
In accordance with the embodiments of the present disclosure, the method of the present disclosure comprises a step of preparing a polybutadiene nanocomposite, which includes a step of embedding a nanofiller in a polybutadiene during the process of polymerization of 1,3-butadiene.
Conventionally, the composites/ nanocomposites are prepared using the ex-situ method. The ex-situ method comprises melt compounding the polymer with at least one nanofiller/filler at a temperature greater than the glass-transition temperature (Tg) of the polybutadiene to obtain a mixture, and cooling the mixture to obtain the polybutadiene nanocomposite/composite.
The butadiene rubber without any filler embedded in it, has tensile strength of 1.6 MPa. When the butadiene rubber is converted to polybutadiene composite comprising at least one filler, the tensile strength increases, exhibiting better mechanical properties of composite as compared to butadiene rubber.
Further, it is found that the tensile strength of the polybutadiene composite increases with increased loading of filler. With an increase in the filler loading, the rubber–filler interaction increases, resulting in the increased tensile strength. However, filler loading of greater than 10 phr results in brittle polybutadiene. To avoid such problem, nanofillers, which impart better mechanical properties at lower loading, were used for preparing the nanocomposites.
The butadiene rubber composites prepared using ex-situ method, comprising 7 phr loading of carbon black and silica show tensile strength of 1.8 MPa and 2.8 MPa, respectively. The polybutadiene nanocomposites exhibit better tensile strength at lower nanofiller loading as compared to the conventional filler loading.
After studying mechanical properties of the polybutadiene nanocomposites prepared using ex-situ method, it is observed that CNT provides best results at 5 phr loading and nanosilica provides the best results at 3 phr loading.
In order to select the nanofillers to be used for preparing polybutadiene nanocomposites by in-situ method, experiments were performed using ex-situ method. The nanocomposites prepared using the method of the present disclosure exhibit uniform dispersion of nanofillers in the nanocomposites.
In accordance with the present disclosure, the percent conversion of 1,3-butadiene to polybutadiene nanocomposite is in the range of 40 % to 70%. The yield of the method of the present disclosure is found to be better as compared to the conventional methods for the preparation of nanocomposite. The polybutadiene nanocomposite obtained using the method of the present disclosure is lighter and therefore convenient for handling.
In accordance with the present disclosure, the polybutadiene nanocomposites obtained using the method of the present disclosure, are characterized by tensile strength in the range of 1.8 to 3.6 MPa.
The polybutadiene nanocomposite comprising 0.5 phr loading of CNT, prepared by ex-situ method, has a tensile strength of 1.7 MPa. Whereas, the poybutadiene nanocomposite comprising 0.2 phr loading of CNT, prepared by in-situ method, has a tensile strength of 1.8 MPa. Thus, it is clear that the tensile strength of nanocomposites prepared by the ex-situ method can be achieved using lesser amount of nanofillers prepared by in-situ method.
After studying the temperature profiles of formation of polybutadiene nanocomposites at different CNT loading, it is observed that the reaction slowed down at 3 phr loading of CNT, due to higher nanofiller loading, which indicate that the higher CNT loading reduces butadiene polymerization. The maximum conversion is achieved at 0.2 phr CNT loading using in-situ method.
In the present disclosure, polybutadiene nanocomposites prepared using in-situ method requires lesser amount of nanofillers to achieve desired properties of the nanocomposites as compared to the ex-situ method.
The present disclosure is further described in light of the following experiments, which were conducted on manufacture of polybutadiene rubber using the conventional fillers and nanofillers, prepared using the ex-situ method as compared to similar products manufactured in the present disclosure by the in-situ method.

Experiments
Experiments 1 (Comparative): Ex-situ method for preparing composites/nanocomposites via melt compounding
In a PlastiCorder PL 2000 (Brabender), unvulcanized butadiene rubber (BR) was mixed with di-tert-butyl-p-cresol (DTBC), N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6ppd), and microcrystalline wax (mixture of a higher percentage of isoparaffins (branched) to obtain a mixture. Di-tert-butyl-p-cresol (DTBC), N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6ppd) were used as antioxidants and microcrystalline wax was used as antiozonant. The mixture was stirred at 25 rpm and at different temperatures in the range of 130 to 140 °C for a time period of 1 minute. Zinc oxide and stearic acid were then introduced in the Brabender. The resultant mixture was further stirred at 40 rpm and at different temperatures in the range of 130 to 140 °C for a time period of 2 minutes. This was followed by addition of ingredients like nanofillers/conventional fillers, aromatic oil (presence of double bonded mix ring carbon structure) and stirring was continued at different temperatures in the range of 130 to 140 °C at 40 rpm for 5 minutes. In order to achieve proper mixing, the unvulcanized butadiene rubber was passed through a two roll mixing mill. Remixing was carried out for another 2 minutes. Sulfur and accelerators having sulfenamide group (N-cyclohexyl-2-benzthiazole-sulfenamide (CBS), N-tert-butyl-2-benzothiazolesulfenamide (TBBS)), sulfur and CBS (N-cyclohexyl-2-benzothiazyl sulfenamide) were added by passing it through a two roll mixing mill. Then the butadiene rubber was vulcanized at 145 °C in a compression molding press at optimum cure time. The vulcanized butadiene rubber samples were cut from the vulcanized sheets for the analysis.
The weight of the butadiene rubber (BR) and the additives used for the ex-situ preparation of nanocomposites are given in Table 1.
Table 1: Formulation of nanocomposites of Experiment 1
Materials phr
BR 100
N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine (6 ppd) 1
Di-tert-butyl-p-cresol (DTBC) 0.5
Zinc Oxide 5
Stearic Acid 2
Sulfur 1.3
N-cyclohexyl-2-benzothiazyl sulfenamide (CBS) 1.3
CNT 2
Aromatic Oil (double bonded mix ring carbon structure) 0.5
Microcrystalline wax 0.5

Effect of conventional filler carbon black (CB) and precipitated silica (S) loading on butadiene rubber (BR) composites
Melt compounding of butadiene rubber with carbon black was carried out by mixing the butadiene rubber and carbon black above the glass-transition temperature (Tg) of the butadiene rubber. The melt blending of the butadiene rubber with silica was carried out in the presence of silane, by mixing the butadiene rubber above the glass-transition temperature (Tg) of the butadiene rubber to obtain polybutadiene composites. For melt compounding with silica, silane (10 wt% of silica) was used as a coupling agent, to enhance the dispersal of the silica and to build up a strong interfacial interaction between the butadiene rubber and silica.
Polybutadiene composites obtained were analyzed for tensile strength and the results are summarized in Table 2.
Table 2: Tensile strength of the polybutadiene composites prepared using the conventional fillers (Carbon black/ precipitated silica)
Sample Tensile Strength (MPa)
BR 1.6
BR/C-1 1.6
BR/C-3 1.7
BR/C-7 1.8
BR/C-10 1.9
BR/C-12 2.1
BR/C-15 3.0
BR/C-30 3.1
BR/C-50 3.6
BR/S-1 1.8
BR/S-3 2.2
BR/S-7 2.8
BR/S-10 3.0
BR: butadiene rubber, C- carbon black, S- silica, the numbers 1, 3, 7, 10, 12, 15, 30, 50, 1, 3, 7, and 10 of the column sample represent per hundred rubber (phr) loadings of the fillers.
From the results obtained, it is evident that the butadiene rubber has 1.6 MPa of tensile strength. When the butadiene rubber was transformed to butadiene rubber composite with 1 phr carbon loading the tensile strength did not change. The tensile strength of the polybutadiene composites increases with increased loading of carbon black. With an increase in the filler loading, the rubber–filler interaction increases, resulting in the increased tensile strength (Table 1). Thus, it is clear that the composites have better tensile strength as compared to the butadiene rubber.
Experiment 2: Effect of the amount of nanoclays on polybutadiene nanocomposites
In order to study the effect of nanofillers on the tensile strength of the butadiene rubber the conventional fillers were replaced with nanofillers. In this experiment nanoclay was chosen as the nanofiller. Polybutadiene nanocomposites with different amounts of nanoclays were prepared using the procedure similar to Experiment 1.
Polybutadiene nanocomposites obtained were analyzed for their tensile strength and the observed tensile strength of different nanoclay filled nanocomposites are summarized in Table 3.
Table 3: Tensile strength of polybutadiene nanocomposites prepared with organic/inorganic nanoclay
Sample Tensile Strength (MPa)
BR 1.6
BR/20A-3 2.7
BR/20A-7 3.7
BR/20A-10 3.1
BR/Na+-3 2.1
BR/Na+-5 2.5
BR/Na+-7 3.3
BR/Na+-10 2.0
BR: butadiene rubber, 20A: Cloisite 20A organic clay, Na+: Cloisite Na+ (inorganic clay) the numbers 3, 7, 10, 3, 5, 7, and 10 of the column sample represent per hundred rubber (phr) loadings of the nanofillers.
It is observed that the nanocomposites prepared using ex-situ method showed remarkable increments in the tensile strength of the polybutadiene nanocomposites with Cloisite 20A (organic) as well as Cloisite Na+ (inorganic) nanoclay.
From Table 3 it is clear that at 7 phr (per hundred rubber) loading, polybutadiene nanocomposites containing nanoclay showed improved tensile strength (231% and 206%).
Both, organic and inorganic nanocomposites, showed maximum improvement in the tensile strength at 7 phr loading, as a result of better polybutadiene-nanoclay interaction. On further increasing the amount of respective nanoclay in both the cases, the tensile strength decreased, as a result of agglomeration of the nanoclay.
In contrast, the conventional fillers like carbon black and silica showed very little improvement in tensile strength, at the filler loading of 7 phr. Therefore, by using nanofillers at such a low loading of 7 phr, nanocomposites with lighter weight and highly improved tensile strength can be made. Nanocomposites with both, Cloisite 20A (organic) and Cloisite Na+ (inorganic), showed improvement in tensile strength at 7 phr loading. Various combinations of Cloisite 20A (organic) and Cloisite Na+ (inorganic) were used in the ratio of 80:20, 60:40, 20:80, and 10:90 to make polybutadiene nanocomposites. The results are summarized in Table 4.
Table 4: Tensile strength of polybutadiene nanocomposites prepared with organic/inorganic nanoclay at 7 phr loading
Sample Tensile Strength (MPa)
BR/Na+-7 3.3
BR/20A-7 3.7
BR/(80:20)-7 3.9
BR/(60:40)-7 2.5
BR/(10: 90)-7 3.2
BR/(20: 80)-7 2.2
The number 7 of the column sample represents per hundred rubber (phr) loadings of the nanofillers.
From Table 4, it is observed that the combinations of nanoclays showed synergistic effect on the polybutadiene matrix. It did not have substantial effect on tensile strength of the polybutadiene nanocomposites.
Experiment 3: Effect of Carbon Nanotubes (CNT) filler loading on polybutadiene nanocomposites
Experimental procedure similar to that of Experiment 1 was followed. It was observed that the tensile strength increased with the increase in nanofiller loading. The results are summarized in Table 5.
Table 5: Tensile strength of polybutadiene nanocomposites with different CNT filler loading
Sample Tensile Strength (MPa)
BR 1.6
BR/CNT-0.5 1.7
BR/CNT-1 1.9
BR/CNT-3 2.3
BR/CNT-5 3.9
BR/CNT-8 3.3
BR/CNT-10 3.0
BR: butadiene rubber, CNT: carbon nanotubes, the numbers 0.5, 1, 3, 5, 8 and 10 of the column sample represent per hundred rubber (phr) loadings of the nanofillers.
It is observed that at 5 phr loading of CNT, the tensile strength has increased by 243%.
Experiment 4: Effect of Nanosilica-silane filler loading on polybutadiene nanocomposites
Experimental procedure was similar to that of Experiment 1. Tensile strength of the nanosilica silane modified composites are summarized in Table 6.
Table 6: Tensile strength of polybutadiene nanocomposites with different nanosilica filler loading
Sample Tensile Strength (MPa)
BR 1.6
BR/NS-0.1 1.6
NS-0.5 1.8
BR/NS-1 1.7
BR/NS-3 3.7
BR/NS-5 2.4
BR: butadiene rubber, NS: nanosilica, the numbers 0.1, 0.5, 1, 3 and 5 of the column sample represent per hundred rubber (phr) loadings of the nanofillers.
Hardness values for nanosilica loaded nanocomposites were found in the range of 40 to 50 shore A. Nanosilica based nanocomposites showed significant enhancement in the tensile strength at lower loading, whereas, to achieve similar results with silica, higher loading of silica was required.
From Table 6, it is observed that nanosilica at 3 phr provided maximum tensile strength (231%).
Comparison of different nanofillers with conventional fillers
Table 7 represents the comparison of conventional fillers with the nanofillers, used at their optimal filler loading. The polybutadiene nanocomposites prepared using carbon nanotubes showed improved tensile strength as compared to the polybutadiene composite prepared using conventional fillers (Table 7). As most of the nanocomposites were prepared with nanofillers, optimized at a loading of = 7 phr, their comparison with polybutadiene composites prepared using carbon black and silica was carried out at 7 phr.
Table 7: Comparative tensile strength of different fillers with conventional fillers
Sample Tensile Strength (MPa)
BR/S-7 2.3
BR/C-7 1.8
BR/20A-7 3.7
Na+-7 3.3
BR/NS-3 3.7
BR/CNT-5 3.9
BR: butadiene rubber, S: precipitated silica, 20A: Cloisite 20A (organic clay), Na+: Cloisite Na+ (Inorganic clay), NS: nanosilica, CNT: carbon nanotubes, the numbers 7, 3 and 5 of the column sample represent per hundred rubber (phr) loadings of the nanofillers.
General procedure for preparing polybutadiene nanocomposites by in-situ method of this disclosure, using cobalt octoate as a catalyst:
Predetermined amount of 1,3-butadiene was mixed with toluene to obtain a feed comprising 20 wt% 1,3-butadiene. 1,3-butadiene can be purified by passing it through a solution of triethylaluminum in the first fluid medium, and resultant stream can be further passed through molecular sieves. The feed, at least one nanofiller, 0.02 millimoles of cobalt octoate (5.1% concentration) per hundred gram of 1,3-butadiene, 7.5 millimoles of diethylaluminum chloride (DEAC) (12.1% concentration) per hundred gram of 1,3-butadiene and toluene were introduced into a reactor to obtain a reaction mass. The reaction mass was stirred under N2 atmosphere at 60 °C for 3 hours to polymerize 1,3-butadiene to obtain a first mixture. The polymerization of 1,3-butadiene was terminated by adding 0.5% of di-tertbutyl-para-cresol (DTBPC) in methanol to the first mixture to obtain a second mixture comprising the polybutadiene nanocomposite. The polybutadiene nanocomposites were separated from the second mixture by filtration, followed by drying at 45 °C, for 6 hours to obtain the polybutadiene nanocomposites.

Comparative:- Polymerization of 1,3-butadiene using co-polymerization technique was done as per standard recipe without adding any filler.
The polymerization of 1,3-butadiene is exothermic. A significant temperature difference was observed as the reaction was advanced.
In-situ Polymerization at 0.2 phr CNT loading
Standard polymerization reactions were carried out with the filler loading of CNT. In all the in-situ reactions, firstly, the filler was added into the reactor followed by the feed, while agitating the mixture for a few seconds, and finally the catalyst composition.
There is little effect of 0.2 phr filler loading on the reaction exothermicity. It was observed that the CNT loading helps enhancing the reaction rate and conversion.
In-situ Polymerization at 0.6 phr CNT loading
The temperature profile of the polymerization was similar to the 0.2 phr CNT loaded polymerization.
It is observed that CNT loading of 0.6 phr helped enhancing the reaction rate and conversion.
In-situ Polymerization at 0.8 phr CNT loading
It is observed that CNT loading of 0.8 phr lowered the reaction rate due to higher filler loading. 10 °C reduction was seen in the ?T. The conversion was also reduced, while the viscosity of the polybutadiene remained unchanged.
In-situ Polymerization at 2 phr CNT loading
It is observed that CNT loading of 2.0 phr lowered the reaction rate due to higher filler loading. A negative difference of reactor and bath temperature was observed, which indicated that the higher loading of CNT resulted in endothermic reaction. The conversion was also reduced.
In-situ Polymerization at 3 phr CNT loading
The temperature profile at 3 phr CNT loading implies that the reaction was slowed down due to higher filler loading. Further, the drastic reduction in the temperature difference was observed, which showed that the higher loading of CNT reduced the polymerization of 1,3-butadiene. Furthermore, it reduced the conversion and consequently time duration of the reaction was longer.
A comparative study of conversion profiles against varying filler loadings is done. It is found that the maximum conversion is achieved at 0.2 phr CNT concentrations. The rate of conversion decreased with increasing CNT concentration.
Similarly, in case of nanosilica loaded nanocomposites prepared by in-situ method, the maximum conversion is achieved at lower concentrations and the rate of conversion decreased with increasing nanosilica concentration.
From the comparative study between 3 phr loaded nanosilica and nanocomposite, it is envisaged that higher conversion could be achieved for nanosilica in comparison to CNT at similar filler loading.
Tensile properties
Tensile properties of different in-situ nanocomposites are reported in Table 8. The tensile strength achieved with 0.5 phr CNT nanocomposites prepared by ex-situ method, was achieved with 0.2 phr CNT nanocomposites prepared by in-situ method. Similarly, the tensile strength achieved with 1 phr of nanosilica in in-situ was higher (41%) than 1 phr nanosilica-silane ex-situ nanocomposites.
Table 8: Tensile strength of nanocomposites prepared using in-situ method
Sample Tensile Strength (MPa)
PBR 1.6
PBR+CNT 0.2 1.8
PBR+CNT 0.6 1.9
PBR+CNT 0.8 2.1
PBR+CNT 3 2.2
PBR+NS 1 2.4
PBR+NS 3 2.7
PBR+NS 5 3.2
PBR+NS 7 3.6

Thermal properties analysis
The thermal decomposition behavior of BR NCs was assessed by thermogravimetric analysis (TGA) and derivative thermogravimetric analysis (DTG). The results are reported in Table 9 in terms of Tmax (Temperature corresponding to the maximum value in the derivative thermo gram). It showed that Tmax increased and Tonset decreased after the incorporation of CNT in polybutadiene by in-situ method.
Table 9: First derivative temperatures of in-situ samples
Sample T max
In blank 466.56
In CNT 0.2 468.49
In CNT 0.8 470.58

In-situ nanocomposites prepared by Ni-polymerization method
General procedure for preparing polybutadiene nanocomposites by in-situ method, using nickel naphthenate as catalyst:
Predetermined amount of 1,3-butadiene was mixed with n-heptane:toluene (50:50) mixed solvent to obtain a feed comprising 20 wt% 1,3-butadiene. The feed, at least one nanofiller, 0.02 millimoles of nickel naphthenate per hundred gram of 1,3-butadiene and triethylaluminum (TEAL) were introduced into a reactor to obtain a reaction mass. The reaction mass was stirred under N2 atmosphere, at 60 °C, for 3 hours to polymerize 1,3-butadiene to obtain a first mixture. The polymerization of 1,3-butadiene was terminated by adding phosphate of polyoxyethylene alkyl phenyl ether (PPA) to the first mixture to obtain a second mixture comprising the polybutadiene nanocomposite. The polybutadiene nanocomposites were separated from the second mixture by filtration, followed by drying at 45 °C, for 6 hours to obtain the polybutadiene nanocomposites.
In addition to using cobalt octoate and nickel naphthenate, titanium supported on MgCl2 can also be used as the polymerization catalyst.
Rheometric study
The rheometric study of the polybutadiene rubber and 0.5 phr CNT loaded polybutadiene nanocomposite was carried out in order to understand the mechanical properties of the rubber.
From the rheomteric study, it was inferred that the nanofiller embedded PBR nanocomposites possess improved mechanical properties. Similar results were reflected in tensile strength data. The tensile strength of nanocomposite loaded with 0.5 phr CNT showed 21 % improvement, in comparison with butadiene rubber. The interaction between nanofillers and rubber matrix reflects upon their hardness value. The hardness increases in the presence of nanofillers. Interestingly, it is also noticed that the heat build-up of the system decreases with incorporation of nanofiller which is essentially required in rubber product application. With decreasing heat build-up of rubber compound, the rolling resistance of rubber significantly reduces which ultimately improve the fuel economy. This has positive impact in tire industry.
TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of:
- a method for manufacturing a polybutadiene nanocomposite that overcomes the poor dispersion of nanofillers in the polybutadiene matrix.
- a method for manufacturing a polybutadiene nanocomposite with improved/desired mechanical properties.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results. While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications to the formulation of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention.
The numerical values given for various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the invention unless there is a statement in the specification to the contrary.
While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.
,CLAIMS:WE CLAIM
1. An in-situ method for preparing a polybutadiene nanocomposite, said method comprising the following steps:
a) mixing a predetermined amount of 1,3-butadiene with at least one first fluid medium to obtain a feed;
b) introducing said feed, at least one nanofiller, a catalyst composition, and at least one second fluid medium into a reactor to obtain a reaction mass;
c) polymerizing said 1,3-butadiene by stirring said reaction mass under inert atmosphere, at a temperature in the range of 50 °C to 80 °C, for a time period in the range of 1 hour to 5 hours to obtain a first mixture;
d) terminating the polymerization by adding a terminating agent to said first mixture to obtain a second mixture comprising said polybutadiene nanocomposites; and
e) separating the polybutadiene nanocomposite from said second mixture, followed by drying at a temperature in the range of 30 °C to 60 °C, for a time period in the range of 4 hour to 8 hours to obtain a dry polybutadiene nanocomposite.

2. An in-situ method for preparing a polybutadiene nanocomposite, said method comprising the following steps:
a) mixing 1,3-butadiene with toluene to obtain a feed comprising 20 wt% of 1,3-butadiene;
b) introducing said feed, at least one nanofiller selected from the group consisting of CNT and nanosilica, a catalyst composition comprising either nickel naphthenate, trietyl aluminum and boron trifluoride ether, or cobalt octoate, diethyl aluminum chloride, and boron trifluoride ether, and toluene into a reactor to obtain a reaction mass;
c) polymerizing said 1,3-butadiene by stirring said reaction mass under inert atmosphere, at 60 °C, for 3 hours to obtain a first mixture;
d) terminating the polymerization by adding a terminating agent to said first mixture to obtain a second mixture comprising said polybutadiene nanocomposites; and
e) separating said polybutadiene nanocomposites from said second mixture, followed by drying at 45 °C, for 6 hours to obtain said polybutadiene nanocomposites.

3. A method of preparing a polybutadiene nanocomposite, which includes a step of embedding a nanofiller in a polybutadiene during the process of polymerization of 1,3-butadiene.

4. The method as claimed in claim 1, wherein said first fluid medium and said second fluid medium are each at least one independently selected from the group consisting of heptane, cyclohexane, hexane, toluene, benzene, and ethylbenzene.

5. The method as claimed in claim 1, wherein said nanofiller is at least one selected from the group consisting of carbon nanotubes and nanosilica.

6. The method as claimed in claim 1, wherein said catalyst composition comprises at least one catalyst component, at least one co-catalyst component and at least one promoter.

7. The method as claimed in claim 6, wherein said catalyst component is at least one selected from the group consisting of cobalt octoate, nickel napthenate, and titanium supported on MgCl2; said co-catalyst component is at least one selected from the group consisting of triethylaluminum (TEAL), tridecylaluminum, tri-n-butylaluminum, tri-isopropylaluminum, tri-isoprenylaluminum, tri-isobutylaluminum, ethyl aluminum sesquichloride, diethylaluminum chloride (DEAC), di-isobutyl aluminum chloride, triphenylaluminum, tri-n-octylaluminum, and tri-n-decylaluminum; said promoter is at least one selected from the group consisting of water, boron trifluoride ether complex (BRF), glycerol and methanol.

8. The method as claimed in claim 1, wherein said terminating agent is at least one selected from the group consisting of phosphate of polyoxyethylene alkyl phenyl ether (PPA) and 0.5% of di-tertbutyl-para-cresol (DTBPC) in methanol.

9. The method as claimed in claim 6, wherein the weight ratio of said catalyst component to said 1,3-butadiene is in the range of 1:100 to 1:1000.

10. The method as claimed in claim 6, wherein the weight ratio of said co-catalyst component to said catalyst component is in the range of 5:1 to 50:1; and the ratio of the promoter to said co-catalyst component is in the range of 1:1 to 1:5.

11. The method as claimed in claim 1, wherein said 1,3-butadiene in step (a) is purified by passing it through a solution of triethylaluminum in the first fluid medium, and resultant stream can be further passed through molecular sieves.

12. The method as claimed in claim 1, wherein the percent conversion of said 1,3-butadiene to said polybutadiene nanocomposite is in the range of 40 % to 70%.
13. The polybutadiene nanocomposite obtained by the method as claimed in claim 1, wherein said polybutadiene nanocomposite is characterized by the tensile strength in the range of 1.8 to 3.6 Mpa.

14. A polybutadiene nanocomposite having a nanofiller embedded therein during the polymerization of 1,3-butadiene, wherein said polybutadiene nanocomposite is characterized by tensile strength in the range of 1.8 to 3.6 Mpa.