CN115746455A - Free radical oxidation resistant polypropylene and preparation method thereof - Google Patents
Free radical oxidation resistant polypropylene and preparation method thereof Download PDFInfo
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Abstract
The application relates to the technical field of polypropylene high polymer materials, and particularly discloses free radical oxidation resistant polypropylene and a preparation method thereof. The polypropylene for resisting free radical oxidation comprises the following substances in parts by weight: 100 parts of polypropylene powder and 0.4-1 part of antioxidant, wherein the antioxidant comprises one or two of kudzu root extract and lignin. The preparation method comprises the following steps: and (3) mechanically blending the polypropylene powder and the antioxidant, putting the mixture into a double-screw extruder, performing melt extrusion at 170-190 ℃, and granulating to obtain the polypropylene master batch. The polypropylene master batch can be used in the fields of packaging bags, woven bags and the like, and has the advantages of oxidation resistance and high mechanical property.
Description
Technical Field
The application relates to the technical field of polypropylene high polymer materials, in particular to free radical oxidation resistant polypropylene and a preparation method thereof.
Background
When the polymer material is exposed to different conditions, the polymer material can be subjected to oxidative degradation and performance degradation and even failure due to various possible influences, such as increased temperature, shearing force and the presence of oxygen, which are main factors for degradation in the processing process, and the exposure to air pressure difference, temperature difference and light during use can also be a reason for accelerating the oxidation of the polymer material, and the exposure to the factors can cause the thermo-mechanical or thermo-oxidative degradation of the polymer material.
In order to improve the antioxidant performance of the polymer material, an antioxidant (stabilizer) is usually added to the polymer material to improve the antioxidant effect of the polymer material. Polypropylene is a common high molecular material, tertiary carbon atoms in the polypropylene are sensitive to oxygen, and hindered phenol antioxidants such as 2,6-di-tert-Butylphenol (BHT), antioxidant 1010, antioxidant DMB and the like are usually added into the polypropylene.
Aiming at the related technologies, most of the currently industrially used antioxidants are organic antioxidants, the use cost is high, the environment is easily damaged, and the antioxidants are easily migrated in the polypropylene, so that the polypropylene has the defect of poor antioxidant effect.
Disclosure of Invention
In order to overcome the defect that the polypropylene has poor antioxidant effect, the application provides free radical oxidation resistant polypropylene and a preparation method thereof.
In a first aspect, the present application provides a free radical oxidation resistant polypropylene, which adopts the following technical scheme:
the polypropylene for resisting free radical oxidation comprises the following substances in parts by weight: 100 parts of polypropylene powder and 0.4-1 part of antioxidant, wherein the antioxidant comprises kudzu root extract and lignin.
Through adopting above-mentioned technical scheme, preferably adopt the root of kudzu vine extract as antioxidant among this application technical scheme, the root of kudzu vine extract can clear away DPPH free radical, hydroxyl free radical and super oxygen anion free radical to the root of kudzu vine extract has good reducing power, consequently gives antioxidant excellent antioxidant effect.
The kudzu root extract is matched with the lignin, the lignin is in a fiber structure with a three-dimensional network structure, the kudzu root extract can be loaded, and the dispersion uniformity of the lignin in the polypropylene can be promoted due to the good compatibility and combination performance between the kudzu root extract and the polypropylene. In addition, the mechanical strength of the polypropylene can be effectively improved by adding the lignin, the better mechanical property of the polypropylene can be still maintained when the polypropylene is slightly aged, and the mechanical property loss caused by the breakage of hydrogen bonds in the polypropylene is compensated.
And secondly, as the phenolic hydroxyl and alcoholic hydroxyl structures on the lignin have excellent activity and oxidation resistance, after the lignin is added into polypropylene, free radicals generated by molecular chain fracture are removed, the oxidation resistance of the polypropylene is further improved, and the aging speed of the polypropylene is delayed.
Finally, the lignin and the kudzu root extract are natural materials, so that the environment is friendly, and the cost is low, so that the obtained polypropylene has excellent antioxidant effect and is environment-friendly.
Preferably, the extraction of the pueraria lobata extract comprises the following steps: mixing radix Puerariae powder with water to obtain a mixture, adding sodium hydroxide solution into the mixture, performing alkali extraction, performing constant temperature water bath, centrifuging, collecting supernatant, adding hydrochloric acid solution, adjusting to isoelectric point, centrifuging, collecting precipitate, dialyzing, concentrating, and drying to obtain radix Puerariae extract.
Through adopting above-mentioned technical scheme, preferably adopting alkali to carry out the extraction to the root of kudzu vine by acid precipitation method among this application technical scheme, alkali carries out acid precipitation to the reproducibility of the root of kudzu vine albumen in the root of kudzu vine better, extracts the root of kudzu vine albumen in the root of kudzu vine, and no organic solvent adds, and the root of kudzu vine albumen is difficult for the deactivation, and the extraction of root of kudzu vine albumen is comparatively abundant, therefore the root of kudzu vine extract purity that obtains is high and the activity is excellent, can stably play the effect to anti free radical in polypropylene.
Preferably, the mass ratio of the kudzuvine root powder to water is 1-15.
Through adopting above-mentioned technical scheme, optimized the material liquid ratio that the root of kudzu vine drawed among this application technical scheme, suitable material liquid ratio can promote the interact power between root of kudzu vine protein and the hydrone, accelerates the dissolution of root of kudzu vine protein, increases the extraction rate of root of kudzu vine protein. Under the proper extraction temperature, the interaction between the pueraria protein and the water molecules can be strengthened, the solubility of the protein in water is promoted, the pueraria protein is not easy to be inactivated due to overhigh temperature, and the excellent antioxidant effect of the pueraria protein is maintained. The proper alkali extraction time promotes the cell membrane rupture of the particles in the kudzuvine root powder and accelerates the precipitation and dissolution of protein; the proper alkali extraction pH value can accelerate protein dissolution and reduce the possibility of protein denaturation, and can effectively improve the extraction effect and the antioxidant activity of the pueraria protein.
Preferably, the radix puerariae extract is wrapped by a modifier, the modifier comprises zein and biochar, and the biochar is of a porous structure.
Through adopting above-mentioned technical scheme, adopt porous structure's biological charcoal as the modifier among the application technical scheme, porous structure's biological charcoal can carry out the load to the root of kudzu vine extract, and the compatibility between zein and the root of kudzu vine extract is preferred to polarity difference between zein and the polypropylene is less, consequently can promote the combination effect between biological charcoal and the polypropylene, stably improves the mechanical strength of polypropylene.
Meanwhile, the charcoal has a better high-temperature resistant effect, and can protect the radix puerariae extract to a certain extent, so that the radix puerariae extract can play a stable anti-oxidation role in polypropylene. The addition of a small amount of biochar can reduce the crystallinity of polypropylene and further improve the mechanical strength of the polypropylene. And after the porous structure of the biochar is combined with the polypropylene, a multi-component coexisting interface of the polypropylene, the radix puerariae extract, the zein and the biochar can be formed, namely, each component in the antioxidant can be effectively combined with the polypropylene, so that the interface stability and the antioxidant effect of the polypropylene are improved.
Preferably, the antioxidant further comprises nano titanium dioxide, the nano titanium dioxide and lignin are mutually loaded, and the lignin comprises protective lignin treated by the nano titanium dioxide.
Through adopting above-mentioned technical scheme, preferably adopting in this application technical scheme adds nanometer titanium dioxide in the antioxidant, and nanometer titanium dioxide has good ultraviolet shielding effect, adds in polypropylene back, can stably improve the anti ultraviolet ageing effect of polypropylene. Through the matching of the nano titanium dioxide and the lignin, the surface active groups of the lignin are increased, the ultraviolet rays are shielded, the effect of the active groups in the lignin on removing free radicals in the polypropylene is improved, and the antioxidant effect of the polypropylene is stably improved.
Preferably, the preparation method of the protected lignin comprises the following steps: taking lignin, acetone and water, stirring and mixing, carrying out rotary evaporation and concentration, and cooling and drying to obtain lignin colloid balls; dispersing lignin colloid balls in absolute ethyl alcohol, performing ultrasonic dispersion, and adding n-butyl titanate to obtain a dispersion liquid; taking absolute ethyl alcohol and concentrated hydrochloric acid to obtain intermediate solution; and adding the intermediate solution into the dispersion solution, continuously stirring, centrifuging, retaining solids, washing and drying to obtain the protective lignin.
By adopting the technical scheme, the nano titanium dioxide is preferably loaded on the lignin colloid spheres in the technical scheme of the application to form the titanium dioxide-lignin sphere-based composite material with the shell-core structure, the whiteness of the titanium dioxide can cover the deep color of the lignin, and the obtained composite material is regular in shape and light in color, so that the protective lignin not only obtains excellent ultraviolet and oxidation resistant effects, but also obtains light color, and the polypropylene maintains good chromaticity while obtaining excellent oxidation resistant effect.
Preferably, the antioxidant further comprises nanocrystalline cellulose, wherein the nanocrystalline cellulose is loaded with an organic acid, and the organic acid comprises either or both of protocatechuic acid and gallic acid.
By adopting the technical scheme, the cellulose nanocrystalline is preferably added into the polypropylene in the technical scheme, and the fiber structure of the cellulose nanocrystalline is matched with lignin in the antioxidant, so that the skeleton structure in the polypropylene can be constructed together, and the mechanical strength of the polypropylene is improved. The method has the advantages that the high crystallinity of the nanocrystalline cellulose and the phenolic hydroxyl group of the protocatechuic acid can be maintained by loading the protocatechuic acid on the nanocrystalline cellulose, the nanocrystalline cellulose is endowed with excellent antioxidant effect, and the protocatechuic acid is grafted and fixed on the nanocrystalline cellulose, so that the migration of the protocatechuic acid in the polypropylene can be reduced, namely, the polypropylene obtains stable and safe antioxidant effect.
Secondly, gallic acid is loaded on nanocrystalline cellulose, and the number of phenolic hydroxyl groups on the gallic acid is large, so that free radicals generated in polypropylene can be stably removed.
And finally, the gallic acid and the protocatechuic acid are grafted on the nanocrystalline cellulose in a matching way, so that phenolic hydroxyl groups on the nanocrystalline cellulose are improved, free radicals in the polypropylene are stably removed, and the antioxidant effect of the polypropylene is stably improved.
Preferably, the nanocrystalline cellulose is pretreated, the pretreatment comprising the steps of: preparing nanocrystalline cellulose and methanol to obtain a suspension, adding polyethyleneimine into the suspension, stirring, centrifuging, retaining a solid, soaking the solid in a glutaraldehyde solution, centrifuging, retaining the solid, and washing with water to obtain the pretreated nanocrystalline cellulose.
By adopting the technical scheme, the nanocrystalline cellulose is pretreated, so that long-chain groups are grafted on the nanocrystalline cellulose, the poly-amination of the nanocrystalline cellulose is realized, the grafting is favorably completed by amidation reaction between the nanocrystalline cellulose and organic acid, and the excellent antioxidant effect is given to the nanocrystalline cellulose.
Preferably, the antioxidant further comprises butyl gallate.
By adopting the technical scheme, the butyl gallate is added into the antioxidant, and the butyl gallate and the gallic acid have excellent compatibility, namely the compatibility among the components in the antioxidant is better, so that the antioxidant effect of the polypropylene can be synergistically improved. The butyl gallate has high content of phenolic hydroxyl groups and high density of hydroxyl groups, and can provide more H atoms to block molecular chain breakage or degradation in polypropylene molecules, thereby stably improving the oxidation resistance of acrylic acid.
In a second aspect, the application provides a preparation method of polypropylene resistant to radical oxidation, which adopts the following technical scheme:
a preparation method of polypropylene for resisting free radical oxidation comprises the following steps: and (3) mechanically blending the polypropylene powder and the antioxidant, putting the mixture into a double-screw extruder, performing melt extrusion at 170-190 ℃, and granulating to obtain the antioxidant polypropylene.
By adopting the technical scheme, the polypropylene powder and the antioxidant are melted and extruded for granulation at a proper temperature, and the antioxidant is uniformly dispersed in the polypropylene, so that the polypropylene obtains a uniform antioxidant effect. Secondly, the proportion between the polypropylene powder and the antioxidant is optimized in the technical scheme of the application, and the appropriate antioxidant addition amount enables the polypropylene to obtain the antioxidant effect, and the cost of the antioxidant can be reduced.
In summary, the present application has the following beneficial effects:
1. the kudzu root extract can remove DPPH free radicals, hydroxyl free radicals and superoxide anion free radicals, and has excellent reducing capacity, so that the antioxidant has excellent antioxidant effect.
The kudzuvine root extract is matched with the lignin, the lignin is in a fiber structure with a three-dimensional network structure, the kudzuvine root extract can be loaded, and the compatibility and the combination performance between the kudzuvine root extract and the polypropylene are good, so that the dispersion uniformity of the lignin in the polypropylene can be promoted. In addition, the mechanical strength of the polypropylene can be effectively improved by adding the lignin, the better mechanical property of the polypropylene can be still maintained when the polypropylene is slightly aged, and the mechanical property loss caused by the breakage of hydrogen bonds in the polypropylene is compensated.
2. Through nanometer titanium dioxide and lignin cooperation in this application, increased the surface active group of lignin, when shielding ultraviolet ray, the effect of cleaing away of active group in to the free radical in the polypropylene in the improvement lignin, the anti-oxidant effect of stable improvement polypropylene.
3. Nanometer titanium dioxide is loaded on the lignin colloid spheres to form a titanium dioxide-lignin sphere-based composite material with a shell-core structure, the whiteness of the titanium dioxide can cover the deep color of lignin, the obtained composite material is regular in shape and light in color, so that the protective lignin not only obtains excellent ultraviolet-resistant and antioxidant effects, but also obtains light color, and the polypropylene maintains better chromaticity while obtaining excellent antioxidant effect.
4. In the application, butyl gallate is added into the antioxidant, and the butyl gallate and the gallic acid have excellent compatibility, namely, the compatibility among all the components in the antioxidant is better, and the antioxidant effect of the polypropylene can be synergistically improved. The butyl gallate has high phenolic hydroxyl content and high hydroxyl surface density, and can provide more H atoms to block molecular chain breakage or degradation in polypropylene molecules, so that the antioxidant performance of acrylic acid is stably improved.
Detailed Description
The present application will be described in further detail with reference to examples.
Preparation example
Preparation of Pueraria protein
Preparation example 1
Taking 50g of radix puerariae powder and 750g of water, mixing to prepare a mixed solution, adding 1mol/L of sodium hydroxide to adjust the pH value to 9, carrying out water bath reaction for 1h at 40 ℃, cooling to room temperature, centrifuging at 4000r/min, retaining the supernatant, adding 1mol/L of hydrochloric acid, adjusting the pH value to =7, carrying out centrifugal separation, retaining the precipitate, dialyzing, concentrating and drying to obtain the puerarin 1.
Preparation example 2
Taking 50g of radix puerariae powder and 1000g of water, mixing to prepare a mixed solution, adding 1mol/L sodium hydroxide to adjust the pH value to 10, carrying out water bath reaction at 45 ℃ for 2h, cooling to room temperature, centrifuging at 4000r/min, reserving supernatant, adding 1mol/L hydrochloric acid to adjust the pH value to =7, carrying out centrifugal separation, reserving precipitate, dialyzing, concentrating and drying to obtain the radix puerariae protein 2.
Preparation example 3
Mixing 50g of radix puerariae powder with 1250g of water to prepare a mixed solution, adding 1mol/L of sodium hydroxide to adjust the pH value to 11, carrying out water bath reaction at 50 ℃ for 3h, cooling to room temperature, centrifuging at 4000r/min, retaining the supernatant, adding 1mol/L of hydrochloric acid, adjusting the pH value to =7, carrying out centrifugal separation, retaining the precipitate, dialyzing, concentrating and drying to obtain the puerarin 3.
Preparation of kudzu root extract
Preparation examples 4 to 6
Mixing 1kg of radix Puerariae polysaccharide, 1kg of radix Puerariae protein 1-3, 1kg of radix Puerariae flavone and 1kg of radix Puerariae polyphenol to obtain radix Puerariae extract 1-3.
Preparation example 7
Adding 10g of titanium dioxide powder into 100mL of 1mol/L hydrochloric acid aqueous solution, performing ultrasonic treatment for 10min to uniformly disperse the powder, continuously stirring for 2h, performing centrifugal separation, retaining solids, washing with water, and performing freeze drying to obtain hydroxylated titanium dioxide.
Preparing lignin and tetrahydrofuran to obtain 0.1g/L dispersion liquid, adding hydroxylated titanium dioxide into the dispersion liquid, performing ultrasonic dispersion, and heating and refluxing at 70 ℃ to obtain mutually loaded titanium dioxide and lignin.
Examples of production of protected Lignin
Preparation example 8
1g of lignin, 88mL of acetone and 22mL of water are mixed in advance, 400mL of water is added, the mixture is stirred and mixed, rotary evaporation and concentration are carried out at the temperature of 45 ℃, and cooling and drying are carried out, so as to obtain a lignin colloidal sphere; dispersing 0.5g of lignin colloid spheres in 250mL of absolute ethyl alcohol, performing ultrasonic dispersion for 30min, and adding 4mL of n-butyl titanate to obtain a dispersion liquid; taking 250mL of absolute ethyl alcohol and 2mL of concentrated hydrochloric acid with the mass fraction of 38% to obtain intermediate solution; adding the intermediate solution into the dispersion solution, continuously stirring at the speed of 2rpm of a peristaltic pump for 12h, centrifuging, retaining the solid, washing with absolute ethanol for 3 times, and drying at 100 ℃ for 12h to obtain the protective lignin.
Preparation of nanocrystalline cellulose
Preparation example 9
Preparing 50mL of nanocrystalline cellulose suspension with the mass fraction of 2% and 100mL of methanol to obtain suspension, adding 0.5g of polyethyleneimine into the suspension, stirring for 2 hours at 35 ℃, centrifuging, retaining a solid, placing the solid in 1% glutaraldehyde solution, stirring for 20 minutes at 25 ℃, centrifuging, retaining the solid, and washing for 3 times to obtain the pretreated nanocrystalline cellulose.
Mixing 4g of protocatechuic acid with 10mL of ethanol to obtain a primary solution; 4.6g of 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (EDC) and 40mLpH =5.5 PBS buffer were added to the primary solution, and mixed with stirring to obtain a secondary solution. Preparing 1g of pretreated nanocrystalline cellulose and water to obtain a treatment solution with the mass fraction of 1%, adding the secondary solution into 100mL of the treatment solution, stirring and reacting at 25 ℃ for 12 hours, centrifuging, and reserving supernatant to obtain the nanocrystalline cellulose 1.
Preparation example 10
The difference from preparation 9 is that: nanocrystalline cellulose 2 was prepared using gallic acid of equal mass instead of protocatechuic acid in preparation example 9.
Preparation example 11
The difference from preparation 9 is that: nanocrystalline cellulose 3 was prepared using 2g of gallic acid and 2g of protocatechuic acid instead of protocatechuic acid in preparation example 9.
Preparation of butyl gallate
Preparation example 12
Taking 7.05g of gallic acid, 5.55g of n-butyl alcohol, 7.05g of p-toluenesulfonic acid and 50mL of 14-dioxane, carrying out reflux reaction for 8 hours, carrying out reduced pressure distillation, recrystallizing the residue with 20% alcohol water, and drying to obtain the butyl gallate.
Examples
Examples 1 to 3
In one aspect, the application provides free radical oxidation resistant polypropylene, which comprises polypropylene powder and an antioxidant, wherein the antioxidant comprises equal mass of radix puerariae extract 1 and lignin.
In another aspect, the present application provides a method for preparing polypropylene resistant to radical oxidation, comprising the following steps: and (2) mechanically blending the polypropylene powder and the antioxidant, putting the mixture into a double-screw extruder, performing melt extrusion at 180 ℃, and granulating to obtain 1-3 parts of antioxidant polypropylene.
TABLE 1 examples 1-3 Polypropylene compositions
Examples 4 to 5
The difference from example 2 is that: equal mass of kudzu root extract 2-3 is adopted to replace kudzu root extract 1 in example 2, and polypropylene 4-5 is prepared.
Example 6
The difference from example 2 is that: 10g of pueraria protein 2, 10g of zein and 20g of biochar are taken and stirred to be mixed to obtain the coated pueraria protein, 0.1kg of pueraria polysaccharide, 0.1kg of pueraria polyphenol and 0.1kg of pueraria flavone are taken and mixed to be used as a pueraria extract 4, and the equal mass of pueraria extract 4 is adopted to replace the pueraria extract 1 in the embodiment 2 to prepare the polypropylene 6.
Example 7
The difference from example 2 is that: polypropylene 7 was prepared using equal mass of titanium dioxide and lignin loaded onto each other instead of lignin as in example 2.
Example 8
The difference from example 2 is that: polypropylene 8 was prepared using 0.2kg of the titanium dioxide and lignin loaded onto each other and 0.2kg of the guard lignin instead of the lignin of example 2.
Example 9
The difference from example 2 is that: the antioxidant comprising 0.3kg of puerariae radix extract 1,0.3kg of lignin and 0.2kg of nanocrystalline cellulose 1 instead of the antioxidant of example 2, polypropylene 9 was prepared.
Examples 10 to 11
The difference from example 9 is that: polypropylene 10-11 was prepared using nanocrystalline cellulose 2-3 of equal mass instead of nanocrystalline cellulose 1 in example 9.
Example 12
The difference from example 2 is that: the antioxidant agent included 0.2kg of puerariae radix extract 1,0.3kg of lignin and 0.3kg of butyl gallate instead of the antioxidant agent in example 2, to prepare polypropylene 12.
Example 13
The difference from example 2 is that: the antioxidant agent included 0.3kg of puerariae radix extract 1,0.3kg of lignin, 0.1kg of nanocrystalline cellulose 3 and 0.1kg of butyl gallate instead of the antioxidant agent in example 2 to prepare polypropylene 13.
Example 14
The difference from example 2 is that: the antioxidant agent included 0.2kg of puerariae radix extract 1,0.3kg of lignin, 0.2kg of butyl gallate and 0.1kg of antioxidant agent 168, instead of the antioxidant agent in example 2, to prepare polypropylene 14.
Comparative example
Comparative example 1
This comparative example differs from example 2 in that the antioxidant comprises only lignin, producing polypropylene 15.
Comparative example 2
This comparative example is different from example 2 in that the antioxidant only includes the pueraria lobata extract, and polypropylene 16 is prepared.
Comparative example 3
This comparative example differs from example 2 in that the antioxidant in this comparative example is antioxidant 168 and polypropylene 17 is prepared.
Performance test
(1) And (3) testing the oxidation resistance: the polypropylene 1-15 was tested for Oxidative Induction Time (OIT) according to GB T19466.6-2009 Differential Scanning Calorimetry (DSC) part 6 oxidative induction time.
(2) Tensile strength: the tensile strength of the polypropylene 1-15 was measured according to GBT 1041-92-test method for compression Properties of plastics.
(3) And (3) testing ultraviolet aging resistance: the ultraviolet aging resistance of the polypropylene 1-15 is tested according to ASTM G154-06 (non-metallic material) fast ultraviolet aging test method, and the aging time of the relatively smooth surface of the polypropylene is recorded.
TABLE 2 Performance test Table
The comparison of the performance tests in combination with table 2 can find that:
(1) Combining examples 1-3 and comparative examples 1-3, it can be found that: the oxidation resistance duration, the ultraviolet resistance duration and the tensile strength of the polypropylene prepared in the embodiments 1 to 3 are all improved, which indicates that the pueraria lobata extract is adopted to be matched with the lignin in the application, the pueraria lobata extract has a better free radical scavenging effect, and the lignin has more phenolic hydroxyl groups and alcoholic hydroxyl groups, so that the oxidation resistance effect of the polypropylene is synergistically improved; in addition, the three-dimensional structure of the lignin can form a skeleton structure in the polypropylene, so that the tensile strength of the polypropylene is improved, and the lignin can be promoted to be uniformly dispersed in the polypropylene through the better compatibility of the radix puerariae extract and the polypropylene, so that the polypropylene can obtain uniform mechanical properties.
(2) Combining examples 4-6, example 7 and example 2, it can be found that: the oxidation resistance duration, the ultraviolet resistance duration and the tensile strength of the polypropylene prepared in the examples 4 to 7 are all improved, which shows that the alkali extraction and acid precipitation method is adopted to extract the kudzuvine root in the application, and the reproducibility of the alkali extraction and acid precipitation on the kudzuvine root protein in the kudzuvine root is better; the temperature, the feed-liquid ratio, the alkali extraction time and the alkali extraction pH value in the extraction are optimized, the dissolving effect and the cell wall rupture effect of the pueraria protein in water can be promoted, and the extraction effect of the pueraria protein is improved. The puerarin is modified by matching the prolamin and the biochar, so that the temperature resistance effect of the puerarin is improved, and the mechanical strength and the antioxidant effect of the polypropylene are improved.
(3) A comparison of examples 7 to 8 with example 2 shows that: the polypropylene prepared in the embodiments 7 to 8 has improved oxidation resistance, ultraviolet resistance, and tensile strength, which means that the nano titanium dioxide is matched with lignin to increase the surface active groups of lignin, and the active groups in lignin can improve the effect of scavenging free radicals in polypropylene while shielding ultraviolet rays, thereby stably improving the oxidation resistance of polypropylene.
(4) A comparison of examples 9 to 11 with example 2 shows that: the oxidation resistance duration, the ultraviolet resistance duration and the tensile strength of the polypropylene prepared in the examples 9 to 11 are all improved, which shows that the fiber structure of the cellulose nanocrystal and the lignin in the antioxidant are matched with each other, so that the skeleton structure in the polypropylene can be constructed together, and the mechanical strength of the polypropylene is improved. Organic acid is loaded on the nanocrystalline cellulose, so that phenolic hydroxyl is increased, the effect of removing free radicals in the polypropylene is improved, and the antioxidant effect of the polypropylene is further improved.
(5) A comparison of examples 12 to 14 with example 2 shows that: the oxidation resistance, the ultraviolet resistance and the tensile strength of the polypropylene prepared in examples 12 to 14 are all improved, which indicates that the butyl gallate has high phenolic hydroxyl content and high hydroxyl density, and can provide more H atoms to block the molecular chain breakage or degradation in the polypropylene molecule, thereby stably improving the oxidation resistance of the acrylic acid.
(6) In the embodiment 14, the butyl gallate is matched with the antioxidant 168, so that the antioxidant effect of the antioxidant can be effectively improved, and the antioxidant effect of the polypropylene can be stably improved.
The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.
Claims (10)
1. The free radical oxidation resistant polypropylene is characterized by comprising the following substances in parts by weight: 100 parts of polypropylene powder and 0.4-1 part of antioxidant, wherein the antioxidant comprises kudzu root extract and lignin.
2. The polypropylene as claimed in claim 1, wherein the radix Puerariae extract is extracted by the steps of: mixing radix Puerariae powder with water to obtain a mixture, adding sodium hydroxide solution into the mixture, performing alkali extraction, performing constant temperature water bath, centrifuging, collecting supernatant, adding hydrochloric acid solution, adjusting to isoelectric point, centrifuging, collecting precipitate, dialyzing, concentrating, and drying to obtain radix Puerariae extract.
3. The free radical oxidation resistant polypropylene according to claim 2, wherein: the mass ratio of the radix puerariae powder to water is 1-15, the constant temperature in the water bath process is 40-50 ℃, the alkali extraction time is 1-3h, and the pH value of the alkali extraction is 9-11.
4. The polypropylene according to claim 2, wherein the polypropylene is free radical oxidation resistant: the radix puerariae extract is wrapped by a modifier, the modifier comprises zein and biochar, and the biochar is of a porous structure.
5. The polypropylene according to claim 1, wherein the polypropylene is free radical oxidation resistant: the antioxidant also comprises nano titanium dioxide, the nano titanium dioxide and lignin are mutually loaded, and the lignin comprises protective lignin treated by the nano titanium dioxide.
6. The polypropylene according to claim 5, wherein the preparation method of the protective lignin comprises the following steps: taking lignin, acetone and water, stirring and mixing, carrying out rotary evaporation and concentration, and cooling and drying to obtain lignin colloid balls; dispersing lignin colloid balls in absolute ethyl alcohol, performing ultrasonic dispersion, and adding n-butyl titanate to obtain a dispersion liquid; taking absolute ethyl alcohol and concentrated hydrochloric acid to obtain intermediate solution; and adding the intermediate solution into the dispersion solution, continuously stirring, centrifuging, retaining solids, washing and drying to obtain the protective lignin.
7. The polypropylene according to claim 1, wherein the polypropylene is free radical oxidation resistant: the antioxidant also comprises nanocrystalline cellulose, wherein organic acid is loaded on the nanocrystalline cellulose, and the organic acid comprises any one or two of protocatechuic acid or gallic acid.
8. The polypropylene according to claim 7, wherein the polypropylene is free radical oxidation resistant: pretreating the nanocrystalline cellulose, wherein the pretreatment comprises the following steps: preparing nanocrystalline cellulose and methanol to obtain a suspension, adding polyethyleneimine into the suspension, stirring, centrifuging, retaining a solid, soaking the solid in a glutaraldehyde solution, centrifuging, retaining the solid, and washing with water to obtain the pretreated nanocrystalline cellulose.
9. The polypropylene according to claim 1, wherein the polypropylene is free radical oxidation resistant: the antioxidant also comprises butyl gallate.
10. The method for preparing polypropylene against radical oxidation as claimed in any one of claims 1 to 9, wherein: and (3) mechanically blending the polypropylene powder and the antioxidant, putting the mixture into a double-screw extruder, performing melt extrusion at 170-190 ℃, and granulating to obtain the polypropylene master batch.
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