Application of PP/nano-calcium carbonate composite in automotive engineering plastics
Polypropylene/nano-calcium carbonate and polypropylene/nano-calcium carbonate/elastomer composites were prepared by different processes and formulations, and the effects of processing technology and formulation on the properties of the composites were compared. The results show that the self-made passivation agent and ultra-high speed stirring method adopt the master granulation process, with 8303 as the matrix resin and the content of nano-calcium carbonate is 4%, the comprehensive energy of the obtained composite material is good.
Keywords: nanoparticle modified polypropylene automotive engineering plastics
Foreword
Nanomaterials refer to materials with dimensions of less than 100 nanometers in one or two dimensions. They have small particle size and large specific surface area. Due to quantum effects and surface effects, the physical, chemical and electrical properties of nanomaterials are higher than those of micron materials. A big difference. Since the first preparation of nylon nanocomposites by the Toyota Materials Research Center in Japan in 1987, nanocomposites have attracted attention due to their excellent properties. At present, there are many types of nano-materials. In terms of inorganic fillers, there are nano-montmorillonite, nano-titanium dioxide, nano-silica, nano-calcium carbonate and the like. Among them, nanometer calcium carbonate is widely used in plastic modification due to its wide source and low price. It is estimated that the consumption of nanometer calcium carbonate in plastic products in developed countries reached 200KT in 1999, and the amount used in China is only 12KT.
Polypropylene has been widely used due to its excellent comprehensive properties. However, its toughness is not good. When it is used in a car bumper, it must be toughened and modified. The traditional modification method is toughening with an elastomer, and the process is relatively mature. Its main disadvantages are poor processing performance, poor flow performance and high cost. The product strength is not good, and it is necessary to use a large amount of foreign exchange to import elastomers. The use of rigid nanomaterials to toughen polypropylene can increase the rigidity and fluidity of polypropylene while toughening, and the cost is not high, and it does not need to use foreign exchange.
The mechanism of rigid particles toughening polypropylene is: due to the addition of rigid particles, the stress concentration of the polypropylene body is changed, and the rigid particles are simplified into a spherical shape. Then, in the tensile stress field, the initial stage of deformation (interfacial debonding) Before), the force of the matrix on the filler is at two extreme tensile stresses, which is compressive stress at the equator, and near the equator, the matrix is ​​also subjected to the pressure of the filler. The addition of rigid particles causes stress concentration around the rigid particles when the polypropylene is subjected to impact, which tends to cause micro-cracking of the matrix resin and absorb a certain deformation work. At the same time, the existence of rigid particles hinders and inactivates the microcrack propagation of the matrix resin, and does not develop into destructive cracking. However, since the compatibility between calcium carbonate and polypropylene is not good, when the particle size of calcium carbonate is large (up to 10 micrometers or more), the interface between it and polypropylene is debonded under stress, and the microcrack is expanded to Macroscopic cracks, but reduce the toughness of the material. Some scholars have suggested that many components that are generally incompatible in the molten state have certain compatibility at the nanometer scale. Due to its extremely small particle size and large surface area, the nano-calcium carbonate has an uncrystallized asymmetric atom on the surface, which makes the nano-calcium carbonate highly active and can form a good bonding interface with the polypropylene matrix.
1 experiment
1.1 main raw materials
Polypropylene 8303 Beijing Yanshan Petrochemical Co., Ltd.; polypropylene 191 imports; K7726 Beijing Yanshan Petrochemical Co., Ltd.; nano-calcium carbonate (60-90 nm) Shanghai Biming; passivation agent, homemade.
1.2 Experimental process
Nanoparticles→Surface Treatment→Masterbatch
→Mixing→Extrusion granulation→Measuring, testing, packaging
Matrix resin
1.3 Testing and characterization
The test strips are injection molded by Z-800 injection molding machine, and then obtained by HY-W universal sample preparation mechanism. The injection temperature is 180 °C, 190 °C, 185 °C, and the injection pressure is 30, 40, 60. . The impact strength was tested by XJ-300A impact test machine according to GBl843-86. The tensile strength and elongation at break were tested by XLL-250 tensile test according to GBl040-92. The bending elastic modulus and bending strength were tested by CMT4303 electronic universal experiment. The machine was tested according to GB/T9341, and the melt flow rate was tested by XRL-500C melt flow rate tester according to GB/T3682.
2 Results and discussion
2.1 Effect of stirring process on the properties of composite materials
Table 1 Effect of stirring process on properties of composites
Stirring method melt flow rate
g/10min
Impact strength
KJ/m2
Flexural modulus
Mpa
Bending strength
MPa
Plastic kneading machine 4.39
16.14
1012
28.37
High speed mixer 4.96
20.75
961
27.24
Powder machine 5.44
31.83
937
27.26
It can be found from Table 1 that the material obtained has the highest impact strength, the best fluidity, and the lowest flexural modulus. The composite material obtained by stirring with a plastic kneader has the lowest impact strength and the bending elastic modulus. The highest amount, the material obtained by stirring with a high-speed mixer, the performance is between the two, and their rotation speed from high to low in order, powder machine, high-speed mixer, plastic kneader. The nanometer calcium carbonate has a small particle size, a large specific surface area, and is highly prone to agglomeration, so that the actual particle size of the calcium carbonate becomes large, and in the case of severe, it can reach the micron order. Due to the high rotation speed of the powdering machine, it can effectively prevent the agglomeration of the nanometer calcium carbonate during the stirring process, or break up some of the agglomerated nanoparticles. When the filling amount is small, the agglomeration effect of the nano calcium carbonate is not obvious, and it can be considered that Most of them are dispersed in the nano-scale in the matrix, and the strong shearing action of the twin-screw forms a physical and chemical bond with the polypropylene matrix. Have a good combination of strength. This structure, on the one hand, reduces the entanglement density of the polypropylene, making it more fluid, and on the other hand, improving its impact properties. Stirring with a plastic kneader, because of their low rotation speed, can not break up the agglomerated calcium carbonate, the particle size of calcium carbonate has increased, even reaching the micron level, so its effect on the performance of polypropylene is the same as micron-sized carbonic acid. There is no significant difference in calcium, and it has no obvious toughening effect.
2.2 Effect of matrix resin on material properties
Table 2 Effect of matrix resin on mechanical properties of composites
Matrix resin impact strength KJ/m2
Flexural modulus of elasticity Mpa
Bending strength MPa
8303
31.83
937
27.26
191
18.48
810
22.21
7726
4.20
1007
27.05
It can be seen from Table 2 that with 8303 as the substrate, the impact strength is much higher than that of 191 and 7726 as the matrix, the flexural modulus is also higher, and the overall performance is the best. 8303 is an ethylene or propylene copolymer, which has high impact strength and poor fluidity. When nano-calcium carbonate toughens polypropylene, the higher the impact strength of the polypropylene matrix, the more obvious the toughening effect. Moreover, the compatibility of the nanometer calcium carbonate and the polyethylene is better than that of the polypropylene, which is more favorable for forming a good bonding interface between the nano calcium carbonate and the matrix resin, and further improving the impact strength of the system.
2.3 Effect of Elastomer and Nano Calcium Carbonate on Properties of Polypropylene
Table 3 Effect of Elastomer on Properties of Nano Calcium Carbonate Modified Polypropylene
Nano calcium carbonate consumption%
Elastomer usage %
Impact strength
KJ/m2
Tensile strength Mpa
Elongation%
Flexural modulus of elasticity Mpa
Bending strength
MPa
4
0
31.83
24.16
500
979
28.01
4
5
55.10
20.48
700
850
23.87
It can be seen from Table 3 that the addition of the elastomer can significantly improve the impact strength and elongation of the composite, but the flexural modulus and flexural strength of the composite are both decreased. That is, the rigidity of the material is adversely affected. This is basically consistent with the laws of elastomers and micron calcium carbonate modified polypropylene.
2.4 Effect of nanometer calcium carbonate dosage on impact properties of materials
Figure 1 Effect of the amount of nanometer calcium carbonate on the properties of composites
As can be seen in Table 1, for the polypropylene/nano-calcium carbonate system, as the amount of nano-calcium carbonate is increased, the composite material
The impact strength of the material first increased, reaching a maximum at the content of 4%. Later, as the amount of nano-calcium carbonate increased, the impact strength of the composite gradually decreased. This indicates that when the content of nanometer calcium carbonate is small, the agglomeration effect is not obvious, and the toughening effect on polypropylene is obtained. With the increase of the amount of nanometer calcium carbonate, the agglomeration effect is more and more obvious, and the calcium carbonate particles with larger particle diameter are more obvious. The content is also more and more, so the toughening effect is also worse. When the filling amount is too large, the agglomeration phenomenon is very serious, and when the content of the micron-sized calcium carbonate is too high, the impact strength of the material is even lowered. For the polypropylene/elastomer/nano-calcium carbonate system, with the increase of the content of nano-calcium carbonate, the notched impact strength of the system first increases. When the content reaches 4%, until the nano-calcium carbonate content reaches 10% or more, the system The impact strength remains essentially unchanged. This should be the toughening effect of the elastomer on the system.
2.5 Effect of pretreatment on material properties
Table 4 Effect of pretreatment on material properties
Stirring method Melt flow rate g/10min
Impact strength
KJ/m2
Tensile strength Mpa
Elongation%
Flexural modulus of elasticity Mpa
Bending strength
MPa
Unprocessed 5.33
16.45
23.62
350
1070
28.34
Processing 6.64
31.83
21.45
550
936
25.28
As can be seen from Table 4, the appropriate surface treatment of the nanometer calcium carbonate with a passivating agent can greatly improve the impact strength of the composite material. This is because although nano-calcium carbonate and polypropylene can form a better bonding interface. However, since the activity of the nano calcium carbonate is large, agglomeration is liable to occur, and the particle diameter is increased, so that the toughening effect cannot be achieved. The pretreatment of nano-calcium carbonate with a coupling agent not only provides a good interface, but also improves the interfacial adhesion, but encapsulates the particles with high activity, which is actually a passivation effect. To some extent, the agglomeration of nano calcium carbonate is prevented, and the dispersion of nano calcium carbonate in polypropylene is promoted. By making the average particle diameter of calcium carbonate small, the proportion of particles actually in the nanometer order is increased, thereby greatly increasing the impact strength of the composite material.
2.6 Effect of processing technology on material properties
Table 5 Effect of processing technology on material properties
Processing technology melt flow rate g/10min
Impact strength
KJ/m2
Tensile strength Mpa
Elongation%
Flexural modulus of elasticity Mpa
Bending strength
MPa
Nano calcium carbonate is added directly to 6.44
31.83
23.13
450
988
22.26
Master granulation 7.87
57.56
22.92
670
1007
26.74
As can be seen from Table 5, the impact strength of the composite material can be improved by the master batching method. This is because, by the method of master granulation, the nano-calcium carbonate is strongly sheared twice by twin screw, which is more advantageous for its uniform dispersion in polypropylene. Promotes the refinement of the particles and enhances the toughening effect from the surface.
3 Conclusion
(1) High-speed stirring and pretreatment with passivating agent, using master granulation method, more favorable for nano-calcium carbonate
Dispersion in polypropylene. Prevent the agglomeration of nano calcium carbonate. The resulting material has the best overall performance.
(2) The optimum amount of nano calcium carbonate in polypropylene is 4%. When the system contains an appropriate amount of elastomer, the amount of the nanoparticles is increased, and the impact strength of the material remains substantially unchanged.
(3) When used in automobile bumpers, the base resin is 8303, which has the best impact strength and the best comprehensive performance.
(4) The nanometer calcium carbonate modified polypropylene engineering plastic obtained by the above method has an impact strength of 58 KJ/m2,
The flexural modulus was 1007 MPa, the flexural strength was 26.74 MPa, the melt flow rate was 7 g/10 min, the tensile strength was 23 MPa, and the elongation was 700%. Meet the requirements of automotive bumpers for material properties.
(5) Applying this method to manufacture materials for automobile bumpers, because there is no expensive elasticity that needs to be imported.
Body can greatly reduce production costs and save a lot of foreign exchange. have a broad vision of application. Expected to have an economic life of 10
Keywords: nanoparticle modified polypropylene automotive engineering plastics
Foreword
Nanomaterials refer to materials with dimensions of less than 100 nanometers in one or two dimensions. They have small particle size and large specific surface area. Due to quantum effects and surface effects, the physical, chemical and electrical properties of nanomaterials are higher than those of micron materials. A big difference. Since the first preparation of nylon nanocomposites by the Toyota Materials Research Center in Japan in 1987, nanocomposites have attracted attention due to their excellent properties. At present, there are many types of nano-materials. In terms of inorganic fillers, there are nano-montmorillonite, nano-titanium dioxide, nano-silica, nano-calcium carbonate and the like. Among them, nanometer calcium carbonate is widely used in plastic modification due to its wide source and low price. It is estimated that the consumption of nanometer calcium carbonate in plastic products in developed countries reached 200KT in 1999, and the amount used in China is only 12KT.
Polypropylene has been widely used due to its excellent comprehensive properties. However, its toughness is not good. When it is used in a car bumper, it must be toughened and modified. The traditional modification method is toughening with an elastomer, and the process is relatively mature. Its main disadvantages are poor processing performance, poor flow performance and high cost. The product strength is not good, and it is necessary to use a large amount of foreign exchange to import elastomers. The use of rigid nanomaterials to toughen polypropylene can increase the rigidity and fluidity of polypropylene while toughening, and the cost is not high, and it does not need to use foreign exchange.
The mechanism of rigid particles toughening polypropylene is: due to the addition of rigid particles, the stress concentration of the polypropylene body is changed, and the rigid particles are simplified into a spherical shape. Then, in the tensile stress field, the initial stage of deformation (interfacial debonding) Before), the force of the matrix on the filler is at two extreme tensile stresses, which is compressive stress at the equator, and near the equator, the matrix is ​​also subjected to the pressure of the filler. The addition of rigid particles causes stress concentration around the rigid particles when the polypropylene is subjected to impact, which tends to cause micro-cracking of the matrix resin and absorb a certain deformation work. At the same time, the existence of rigid particles hinders and inactivates the microcrack propagation of the matrix resin, and does not develop into destructive cracking. However, since the compatibility between calcium carbonate and polypropylene is not good, when the particle size of calcium carbonate is large (up to 10 micrometers or more), the interface between it and polypropylene is debonded under stress, and the microcrack is expanded to Macroscopic cracks, but reduce the toughness of the material. Some scholars have suggested that many components that are generally incompatible in the molten state have certain compatibility at the nanometer scale. Due to its extremely small particle size and large surface area, the nano-calcium carbonate has an uncrystallized asymmetric atom on the surface, which makes the nano-calcium carbonate highly active and can form a good bonding interface with the polypropylene matrix.
1 experiment
1.1 main raw materials
Polypropylene 8303 Beijing Yanshan Petrochemical Co., Ltd.; polypropylene 191 imports; K7726 Beijing Yanshan Petrochemical Co., Ltd.; nano-calcium carbonate (60-90 nm) Shanghai Biming; passivation agent, homemade.
1.2 Experimental process
Nanoparticles→Surface Treatment→Masterbatch
→Mixing→Extrusion granulation→Measuring, testing, packaging
Matrix resin
1.3 Testing and characterization
The test strips are injection molded by Z-800 injection molding machine, and then obtained by HY-W universal sample preparation mechanism. The injection temperature is 180 °C, 190 °C, 185 °C, and the injection pressure is 30, 40, 60. . The impact strength was tested by XJ-300A impact test machine according to GBl843-86. The tensile strength and elongation at break were tested by XLL-250 tensile test according to GBl040-92. The bending elastic modulus and bending strength were tested by CMT4303 electronic universal experiment. The machine was tested according to GB/T9341, and the melt flow rate was tested by XRL-500C melt flow rate tester according to GB/T3682.
2 Results and discussion
2.1 Effect of stirring process on the properties of composite materials
Table 1 Effect of stirring process on properties of composites
Stirring method melt flow rate
g/10min
Impact strength
KJ/m2
Flexural modulus
Mpa
Bending strength
MPa
Plastic kneading machine 4.39
16.14
1012
28.37
High speed mixer 4.96
20.75
961
27.24
Powder machine 5.44
31.83
937
27.26
It can be found from Table 1 that the material obtained has the highest impact strength, the best fluidity, and the lowest flexural modulus. The composite material obtained by stirring with a plastic kneader has the lowest impact strength and the bending elastic modulus. The highest amount, the material obtained by stirring with a high-speed mixer, the performance is between the two, and their rotation speed from high to low in order, powder machine, high-speed mixer, plastic kneader. The nanometer calcium carbonate has a small particle size, a large specific surface area, and is highly prone to agglomeration, so that the actual particle size of the calcium carbonate becomes large, and in the case of severe, it can reach the micron order. Due to the high rotation speed of the powdering machine, it can effectively prevent the agglomeration of the nanometer calcium carbonate during the stirring process, or break up some of the agglomerated nanoparticles. When the filling amount is small, the agglomeration effect of the nano calcium carbonate is not obvious, and it can be considered that Most of them are dispersed in the nano-scale in the matrix, and the strong shearing action of the twin-screw forms a physical and chemical bond with the polypropylene matrix. Have a good combination of strength. This structure, on the one hand, reduces the entanglement density of the polypropylene, making it more fluid, and on the other hand, improving its impact properties. Stirring with a plastic kneader, because of their low rotation speed, can not break up the agglomerated calcium carbonate, the particle size of calcium carbonate has increased, even reaching the micron level, so its effect on the performance of polypropylene is the same as micron-sized carbonic acid. There is no significant difference in calcium, and it has no obvious toughening effect.
2.2 Effect of matrix resin on material properties
Table 2 Effect of matrix resin on mechanical properties of composites
Matrix resin impact strength KJ/m2
Flexural modulus of elasticity Mpa
Bending strength MPa
8303
31.83
937
27.26
191
18.48
810
22.21
7726
4.20
1007
27.05
It can be seen from Table 2 that with 8303 as the substrate, the impact strength is much higher than that of 191 and 7726 as the matrix, the flexural modulus is also higher, and the overall performance is the best. 8303 is an ethylene or propylene copolymer, which has high impact strength and poor fluidity. When nano-calcium carbonate toughens polypropylene, the higher the impact strength of the polypropylene matrix, the more obvious the toughening effect. Moreover, the compatibility of the nanometer calcium carbonate and the polyethylene is better than that of the polypropylene, which is more favorable for forming a good bonding interface between the nano calcium carbonate and the matrix resin, and further improving the impact strength of the system.
2.3 Effect of Elastomer and Nano Calcium Carbonate on Properties of Polypropylene
Table 3 Effect of Elastomer on Properties of Nano Calcium Carbonate Modified Polypropylene
Nano calcium carbonate consumption%
Elastomer usage %
Impact strength
KJ/m2
Tensile strength Mpa
Elongation%
Flexural modulus of elasticity Mpa
Bending strength
MPa
4
0
31.83
24.16
500
979
28.01
4
5
55.10
20.48
700
850
23.87
It can be seen from Table 3 that the addition of the elastomer can significantly improve the impact strength and elongation of the composite, but the flexural modulus and flexural strength of the composite are both decreased. That is, the rigidity of the material is adversely affected. This is basically consistent with the laws of elastomers and micron calcium carbonate modified polypropylene.
2.4 Effect of nanometer calcium carbonate dosage on impact properties of materials
Figure 1 Effect of the amount of nanometer calcium carbonate on the properties of composites
As can be seen in Table 1, for the polypropylene/nano-calcium carbonate system, as the amount of nano-calcium carbonate is increased, the composite material
The impact strength of the material first increased, reaching a maximum at the content of 4%. Later, as the amount of nano-calcium carbonate increased, the impact strength of the composite gradually decreased. This indicates that when the content of nanometer calcium carbonate is small, the agglomeration effect is not obvious, and the toughening effect on polypropylene is obtained. With the increase of the amount of nanometer calcium carbonate, the agglomeration effect is more and more obvious, and the calcium carbonate particles with larger particle diameter are more obvious. The content is also more and more, so the toughening effect is also worse. When the filling amount is too large, the agglomeration phenomenon is very serious, and when the content of the micron-sized calcium carbonate is too high, the impact strength of the material is even lowered. For the polypropylene/elastomer/nano-calcium carbonate system, with the increase of the content of nano-calcium carbonate, the notched impact strength of the system first increases. When the content reaches 4%, until the nano-calcium carbonate content reaches 10% or more, the system The impact strength remains essentially unchanged. This should be the toughening effect of the elastomer on the system.
2.5 Effect of pretreatment on material properties
Table 4 Effect of pretreatment on material properties
Stirring method Melt flow rate g/10min
Impact strength
KJ/m2
Tensile strength Mpa
Elongation%
Flexural modulus of elasticity Mpa
Bending strength
MPa
Unprocessed 5.33
16.45
23.62
350
1070
28.34
Processing 6.64
31.83
21.45
550
936
25.28
As can be seen from Table 4, the appropriate surface treatment of the nanometer calcium carbonate with a passivating agent can greatly improve the impact strength of the composite material. This is because although nano-calcium carbonate and polypropylene can form a better bonding interface. However, since the activity of the nano calcium carbonate is large, agglomeration is liable to occur, and the particle diameter is increased, so that the toughening effect cannot be achieved. The pretreatment of nano-calcium carbonate with a coupling agent not only provides a good interface, but also improves the interfacial adhesion, but encapsulates the particles with high activity, which is actually a passivation effect. To some extent, the agglomeration of nano calcium carbonate is prevented, and the dispersion of nano calcium carbonate in polypropylene is promoted. By making the average particle diameter of calcium carbonate small, the proportion of particles actually in the nanometer order is increased, thereby greatly increasing the impact strength of the composite material.
2.6 Effect of processing technology on material properties
Table 5 Effect of processing technology on material properties
Processing technology melt flow rate g/10min
Impact strength
KJ/m2
Tensile strength Mpa
Elongation%
Flexural modulus of elasticity Mpa
Bending strength
MPa
Nano calcium carbonate is added directly to 6.44
31.83
23.13
450
988
22.26
Master granulation 7.87
57.56
22.92
670
1007
26.74
As can be seen from Table 5, the impact strength of the composite material can be improved by the master batching method. This is because, by the method of master granulation, the nano-calcium carbonate is strongly sheared twice by twin screw, which is more advantageous for its uniform dispersion in polypropylene. Promotes the refinement of the particles and enhances the toughening effect from the surface.
3 Conclusion
(1) High-speed stirring and pretreatment with passivating agent, using master granulation method, more favorable for nano-calcium carbonate
Dispersion in polypropylene. Prevent the agglomeration of nano calcium carbonate. The resulting material has the best overall performance.
(2) The optimum amount of nano calcium carbonate in polypropylene is 4%. When the system contains an appropriate amount of elastomer, the amount of the nanoparticles is increased, and the impact strength of the material remains substantially unchanged.
(3) When used in automobile bumpers, the base resin is 8303, which has the best impact strength and the best comprehensive performance.
(4) The nanometer calcium carbonate modified polypropylene engineering plastic obtained by the above method has an impact strength of 58 KJ/m2,
The flexural modulus was 1007 MPa, the flexural strength was 26.74 MPa, the melt flow rate was 7 g/10 min, the tensile strength was 23 MPa, and the elongation was 700%. Meet the requirements of automotive bumpers for material properties.
(5) Applying this method to manufacture materials for automobile bumpers, because there is no expensive elasticity that needs to be imported.
Body can greatly reduce production costs and save a lot of foreign exchange. have a broad vision of application. Expected to have an economic life of 10
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