AU2021104323A4 - Corncob Powder/Polylactic Acid Composite Material and Preparation Method Therefor - Google Patents
Corncob Powder/Polylactic Acid Composite Material and Preparation Method Therefor Download PDFInfo
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- AU2021104323A4 AU2021104323A4 AU2021104323A AU2021104323A AU2021104323A4 AU 2021104323 A4 AU2021104323 A4 AU 2021104323A4 AU 2021104323 A AU2021104323 A AU 2021104323A AU 2021104323 A AU2021104323 A AU 2021104323A AU 2021104323 A4 AU2021104323 A4 AU 2021104323A4
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- polylactic acid
- corncob powder
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- composite material
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- 239000000843 powder Substances 0.000 title claims abstract description 242
- 229920000747 poly(lactic acid) Polymers 0.000 title claims abstract description 204
- 239000004626 polylactic acid Substances 0.000 title claims abstract description 204
- 239000002131 composite material Substances 0.000 title claims abstract description 89
- 238000002360 preparation method Methods 0.000 title abstract description 9
- 238000002156 mixing Methods 0.000 claims abstract description 71
- 239000012943 hotmelt Substances 0.000 claims abstract description 26
- 238000000034 method Methods 0.000 claims abstract description 26
- RGSFGYAAUTVSQA-UHFFFAOYSA-N Cyclopentane Chemical compound C1CCCC1 RGSFGYAAUTVSQA-UHFFFAOYSA-N 0.000 claims abstract description 12
- 239000001913 cellulose Substances 0.000 claims abstract description 12
- 229920002678 cellulose Polymers 0.000 claims abstract description 12
- 238000005422 blasting Methods 0.000 claims abstract description 6
- DMEGYFMYUHOHGS-UHFFFAOYSA-N heptamethylene Natural products C1CCCCCC1 DMEGYFMYUHOHGS-UHFFFAOYSA-N 0.000 claims abstract description 6
- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 claims abstract description 6
- 125000001624 naphthyl group Chemical group 0.000 claims abstract description 5
- 229920002732 Polyanhydride Polymers 0.000 claims abstract description 3
- 150000001875 compounds Chemical class 0.000 claims abstract description 3
- 239000003607 modifier Substances 0.000 claims description 28
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 22
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 21
- 238000001035 drying Methods 0.000 claims description 19
- 230000001965 increasing effect Effects 0.000 claims description 16
- ANSXAPJVJOKRDJ-UHFFFAOYSA-N furo[3,4-f][2]benzofuran-1,3,5,7-tetrone Chemical compound C1=C2C(=O)OC(=O)C2=CC2=C1C(=O)OC2=O ANSXAPJVJOKRDJ-UHFFFAOYSA-N 0.000 claims description 15
- 238000012545 processing Methods 0.000 claims description 15
- 238000002791 soaking Methods 0.000 claims description 15
- 230000007935 neutral effect Effects 0.000 claims description 11
- 239000003963 antioxidant agent Substances 0.000 claims description 9
- 230000003078 antioxidant effect Effects 0.000 claims description 9
- -1 naphthalenetetracarboxylic anhydride Chemical class 0.000 claims description 8
- 239000012670 alkaline solution Substances 0.000 claims description 7
- STZIXLPVKZUAMV-UHFFFAOYSA-N cyclopentane-1,1,2,2-tetracarboxylic acid Chemical compound OC(=O)C1(C(O)=O)CCCC1(C(O)=O)C(O)=O STZIXLPVKZUAMV-UHFFFAOYSA-N 0.000 claims description 6
- CYIDZMCFTVVTJO-UHFFFAOYSA-N pyromellitic acid Chemical compound OC(=O)C1=CC(C(O)=O)=C(C(O)=O)C=C1C(O)=O CYIDZMCFTVVTJO-UHFFFAOYSA-N 0.000 claims description 6
- 239000002994 raw material Substances 0.000 claims description 6
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 claims description 5
- ARCGXLSVLAOJQL-UHFFFAOYSA-N trimellitic acid Chemical compound OC(=O)C1=CC=C(C(O)=O)C(C(O)=O)=C1 ARCGXLSVLAOJQL-UHFFFAOYSA-N 0.000 claims description 4
- GTDPSWPPOUPBNX-UHFFFAOYSA-N ac1mqpva Chemical compound CC12C(=O)OC(=O)C1(C)C1(C)C2(C)C(=O)OC1=O GTDPSWPPOUPBNX-UHFFFAOYSA-N 0.000 claims description 3
- MZYHMUONCNKCHE-UHFFFAOYSA-N naphthalene-1,2,3,4-tetracarboxylic acid Chemical compound C1=CC=CC2=C(C(O)=O)C(C(=O)O)=C(C(O)=O)C(C(O)=O)=C21 MZYHMUONCNKCHE-UHFFFAOYSA-N 0.000 claims description 3
- 238000004140 cleaning Methods 0.000 claims description 2
- SRPWOOOHEPICQU-UHFFFAOYSA-N trimellitic anhydride Chemical compound OC(=O)C1=CC=C2C(=O)OC(=O)C2=C1 SRPWOOOHEPICQU-UHFFFAOYSA-N 0.000 claims description 2
- 239000007864 aqueous solution Substances 0.000 claims 1
- 229920003023 plastic Polymers 0.000 abstract description 9
- 239000004033 plastic Substances 0.000 abstract description 9
- 239000000126 substance Substances 0.000 abstract description 9
- 238000011049 filling Methods 0.000 abstract description 5
- 125000000524 functional group Chemical group 0.000 abstract description 3
- 239000003513 alkali Substances 0.000 abstract 1
- 239000000243 solution Substances 0.000 description 28
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 18
- 229910052708 sodium Inorganic materials 0.000 description 18
- 239000011734 sodium Substances 0.000 description 18
- 239000002253 acid Substances 0.000 description 15
- 238000006243 chemical reaction Methods 0.000 description 13
- BGYHLZZASRKEJE-UHFFFAOYSA-N [3-[3-(3,5-ditert-butyl-4-hydroxyphenyl)propanoyloxy]-2,2-bis[3-(3,5-ditert-butyl-4-hydroxyphenyl)propanoyloxymethyl]propyl] 3-(3,5-ditert-butyl-4-hydroxyphenyl)propanoate Chemical compound CC(C)(C)C1=C(O)C(C(C)(C)C)=CC(CCC(=O)OCC(COC(=O)CCC=2C=C(C(O)=C(C=2)C(C)(C)C)C(C)(C)C)(COC(=O)CCC=2C=C(C(O)=C(C=2)C(C)(C)C)C(C)(C)C)COC(=O)CCC=2C=C(C(O)=C(C=2)C(C)(C)C)C(C)(C)C)=C1 BGYHLZZASRKEJE-UHFFFAOYSA-N 0.000 description 12
- 239000000463 material Substances 0.000 description 12
- 238000005406 washing Methods 0.000 description 11
- 239000012153 distilled water Substances 0.000 description 10
- 239000011159 matrix material Substances 0.000 description 10
- 239000002904 solvent Substances 0.000 description 9
- 238000003756 stirring Methods 0.000 description 9
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 5
- 238000002844 melting Methods 0.000 description 5
- 230000008018 melting Effects 0.000 description 5
- 230000004048 modification Effects 0.000 description 5
- 238000012986 modification Methods 0.000 description 5
- 230000035484 reaction time Effects 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 4
- 238000001125 extrusion Methods 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000003179 granulation Effects 0.000 description 3
- 238000005469 granulation Methods 0.000 description 3
- 229920000642 polymer Polymers 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 239000002023 wood Substances 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- UFWIBTONFRDIAS-UHFFFAOYSA-N Naphthalene Chemical group C1=CC=CC2=CC=CC=C21 UFWIBTONFRDIAS-UHFFFAOYSA-N 0.000 description 2
- JKIJEFPNVSHHEI-UHFFFAOYSA-N Phenol, 2,4-bis(1,1-dimethylethyl)-, phosphite (3:1) Chemical compound CC(C)(C)C1=CC(C(C)(C)C)=CC=C1OP(OC=1C(=CC(=CC=1)C(C)(C)C)C(C)(C)C)OC1=CC=C(C(C)(C)C)C=C1C(C)(C)C JKIJEFPNVSHHEI-UHFFFAOYSA-N 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 2
- 239000004743 Polypropylene Substances 0.000 description 2
- 229920001587 Wood-plastic composite Polymers 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 2
- 238000004132 cross linking Methods 0.000 description 2
- 238000006731 degradation reaction Methods 0.000 description 2
- XBDQKXXYIPTUBI-UHFFFAOYSA-N dimethylselenoniopropionate Natural products CCC(O)=O XBDQKXXYIPTUBI-UHFFFAOYSA-N 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 230000002708 enhancing effect Effects 0.000 description 2
- 125000004185 ester group Chemical group 0.000 description 2
- 150000002148 esters Chemical class 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- 229920001155 polypropylene Polymers 0.000 description 2
- 230000001737 promoting effect Effects 0.000 description 2
- 239000011155 wood-plastic composite Substances 0.000 description 2
- 239000006087 Silane Coupling Agent Substances 0.000 description 1
- 150000008064 anhydrides Chemical class 0.000 description 1
- 239000004566 building material Substances 0.000 description 1
- 238000005034 decoration Methods 0.000 description 1
- 229920006237 degradable polymer Polymers 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000005886 esterification reaction Methods 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 125000004464 hydroxyphenyl group Chemical group 0.000 description 1
- 230000000877 morphologic effect Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- NFHFRUOZVGFOOS-UHFFFAOYSA-N palladium;triphenylphosphane Chemical compound [Pd].C1=CC=CC=C1P(C=1C=CC=CC=1)C1=CC=CC=C1.C1=CC=CC=C1P(C=1C=CC=CC=1)C1=CC=CC=C1.C1=CC=CC=C1P(C=1C=CC=CC=1)C1=CC=CC=C1.C1=CC=CC=C1P(C=1C=CC=CC=1)C1=CC=CC=C1 NFHFRUOZVGFOOS-UHFFFAOYSA-N 0.000 description 1
- 239000002861 polymer material Substances 0.000 description 1
- 239000011160 polymer matrix composite Substances 0.000 description 1
- 235000019260 propionic acid Nutrition 0.000 description 1
- IUVKMZGDUIUOCP-BTNSXGMBSA-N quinbolone Chemical compound O([C@H]1CC[C@H]2[C@H]3[C@@H]([C@]4(C=CC(=O)C=C4CC3)C)CC[C@@]21C)C1=CCCC1 IUVKMZGDUIUOCP-BTNSXGMBSA-N 0.000 description 1
- 238000012216 screening Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
- C08L67/04—Polyesters derived from hydroxycarboxylic acids, e.g. lactones
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/91—Polymers modified by chemical after-treatment
- C08G63/912—Polymers modified by chemical after-treatment derived from hydroxycarboxylic acids
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L1/00—Compositions of cellulose, modified cellulose or cellulose derivatives
- C08L1/02—Cellulose; Modified cellulose
Abstract
The present application relates to the field of composite materials, in particular to
a corncob powder/polylactic acid composite material and a preparation method
therefor. The method comprises the following steps: modifying polylactic acid by a
polyanhydride or polycarboxy compound with a benzene ring, a naphthalene ring or
cyclopentane, so that a chain end group structure of a polylactic acid molecule is
changed from a monohydroxy structure into a rigid ring molecular structure containing
polycarboxy groups; treating corncob powder by an alkali liquor, and microwave
blasting to expose polyhydroxyl cellulose of the corncob powder; and then hot-melt
blending end-group modified polylactic acid with modified corncob powder, so as to
remarkably promote chemical bonding between polylactic acid and the surface of the
corncob powder by means of rigid polycarboxy functional groups at a chain end of
polylactic acid and polyhydroxyl cellulose exposed on the corncob powder. The
composite material prepared by the method of the present application has high
interfacial strength, and the corncob powder is connected with each other by polylactic
acid to form a cross-linked network, so that the composite material still shows good
mechanical properties at high corncob powder filling rate. Therefore, the method of
the present application can be widely applied to the field of environment-friendly plastic
products.
Description
Corncob Powder/Polylactic Acid Composite Material and Preparation
Method Therefor
The present application relates to the field of composite materials, in
particular to a corncob powder/polylactic acid composite material and a
preparation method therefor.
Plastic products are widely used due to the advantages of easy access to
materials, convenient processing, low price and light texture. However, the
white pollution caused by plastic products is also becoming increasingly
serious.
As a new type of material prepared from wood and plastic, the wood
plastic composite combines the advantages of wood and plastic, for example,
low product cost, improved product texture and environmental protection, and
is widely used in the fields of building materials, interior decoration materials,
packaging and transportation materials as well as cultural and sports goods.
The wood-plastic composite can help to alleviate the problem of "white
pollution" caused by waste plastics. However, common wood-plastic
composites are not fully degradable, and it is even less common to observe a
fully-degradable polymer matrix composite with the addition of corncob
powder.
Corncob is obtained by threshing cobs and then strict screening, and has
the advantages of uniform texture, proper hardness, good toughness and
good wear resistance. Due to huge yield and low cost, corncob is suitable for
the preparation of wood-plastic composites. However, the poor compatibility between corncob and polymer materials such as polypropylene, polyethylene and polylactic acid leads to low interfacial adhesion, which affects the mechanical property of a corncob/polymer composite.
It is known that a main method for improving the interfacial strength of
corncob powder/polymer composites is surface grafting of corncob powder by
adding silane coupling agent to ethanol solution and then blending with
plastics such as polypropylene and polyethylene. However, this method has
limited significance to improve the interfacial strength, and results in a poor
mechanical property of composites highly filled with corncob powder.
The embodiments of the present application are intended to provide a
corncob powder/polylactic acid composite material and a preparation method
therefor, aiming at solving the problems of low interfacial strength between
corncob powder and polylactic acid, poor overall mechanical property and
difficulty in achieving high filling rate in the existing corncob powder/polylactic
acid composite materials.
In a first aspect, the present application provides a method for preparing
a corncob powder/polylactic acid composite material, wherein the method
includes reacting end-group modified polylactic acid and modified corncob
powder through hot-melt blending;
wherein a chain end of the end-group modified polylactic acid is a rigid
ring molecule with a plurality of carboxyl groups; and
polyhydroxy cellulose is exposed on the surface of the modified corncob
powder.
According to the method, the end-group modified polylactic acid with a plurality of carboxyl groups and molecules with rigid ring structures at the chain end is hot-melt blended with the modified corncob powder with polyhydroxy cellulose exposed on the surface, and the polycarboxy functional groups at a chain end of polylactic acid can react with polyhydroxy cellulose exposed on the surface of corncob powder to generate high-density ester groups, thereby increasing the chemical bonding between polylactic acid matrix and corncob powder, increasing the interfacial strength between the two, promoting the formation of cross-linked networks between corncob powder by polylactic acid molecular chains, and enhancing the overall mechanical property of materials.
In a second aspect, the present application provides a corncob
powder/polylactic acid composite material prepared by the method for
preparing a corncob powder/polylactic acid composite material.
The corncob powder/polylactic acid composite material has high
interfacial strength between corncob powder and polylactic acid, with a cross
linked network formed between corncob powder; as a result, the composite
material shows excellent mechanical properties as a whole regardless of the
corncob powder filling rate.
To make more clearly the technical solution in the embodiments of the
present application, the figures required for describing the embodiments will
be briefly described hereinafter. It should be understood that the following
figures only show some embodiments of the present application, and should
not be regarded as limiting the scope of the present application; and for a
person skilled in the art, other figures may also be obtained based on these figures without paying any creative effort.
FIG. 1 and FIG. 2 show SEM graphs of frozen brittle section of an
unmodified polylactic acid-corncob powder composite material provided in
Comparison Example 1.
FIG. 3 and FIG. 4 show SEM graphs of frozen brittle section of a
polylactic acid/corncob powder composite material provided in Example 1.
To make more clearly the purpose, technical solution and advantages of
the present application, the technical solution in the embodiment of the
present application will be clearly and completely described with reference to
the figures in the embodiment of the present application. Obviously, the
embodiments described are only a part of the embodiments of the present
application and not all of them. The components of the embodiments of the
present application described and illustrated in the figures can be usually
arranged and designed in various different configurations.
Therefore, the following detailed description of the embodiments of the
present application provided in the figures is not intended to limit the scope of
the claimed present application, but only represents the selected
embodiments of the present application. All other embodiments obtained by
those of ordinary skill in the art without creative efforts shall fall within the
scope of protection of the present application.
An embodiment of the present application provides a method for
preparing a corncob powder/polylactic acid composite material, wherein the
method includes:
reacting end-group modified polylactic acid and modified corncob powder through hot-melt blending; wherein a chain end of the end-group modified polylactic acid is a rigid ring molecule with a plurality of carboxyl groups; and polyhydroxy cellulose is exposed on the surface of the modified corncob powder.
According to the method, the end-group modified polylactic acid with a
plurality of carboxyl groups and molecules with rigid ring structures at the
chain end is hot-melt blended with the modified corncob powder with
polyhydroxy cellulose exposed on the surface, and the polycarboxy functional
groups at a chain end of polylactic acid can react with polyhydroxy cellulose
exposed on the surface of corncob powder to generate high-density ester
groups, thereby increasing the chemical bonding between polylactic acid
matrix and corncob powder, increasing the interfacial strength between the
two, promoting the formation of cross-linked networks between corncob
powder by polylactic acid molecular chains, and enhancing the overall
mechanical property of materials.
In some embodiments of the present application, the method for
preparing a corncob powder/polylactic acid composite material includes:
step S1. preparing end-group modified polylactic acid through hot-melt
blending of polylactic acid with an end-group modifier.
Furthermore, the end-group modifier is polyanhydride with a benzene ring,
a naphthalene ring or a cyclopentane rigid ring molecule; or the end-group
modifier is a polycarboxy compound with a benzene ring, a naphthalene ring
or a cyclopentane rigid ring molecule.
Furthermore optionally, the end-group modifier is selected from any one of pyromellitic anhydride, pyromellitic acid, trimellitic anhydride, trimellitic acid, naphthalenetetracarboxylic anhydride, naphthalenetetracarboxylic acid, cyclopentanetetracarboxylic dianhydride or cyclopentanetetracarboxylic acid.
The hot-melt blending of the end-group modified polylactic acid with the
modified corncob powder, on the one hand, generates high-density ester
groups, which can significantly increase the chemical bonding between
polylactic acid matrix and corncob powder, promote the dispersion of corncob
powder and increase the interfacial strength between the two;
on the other hand, the stress conduction between corncob powder and
polylactic acid matrix is further enhanced due to the intrinsic rigidity of
benzene ring, naphthalene ring and cyclopentane in the selected end-group
modifier.
Furthermore, during the hot-melt blending of polylactic acid with the end
group modifier, the mass/molar mass ratio of the polylactic acid to the end
group modifier is 1:1-1:4.
Exemplarily, pyromellitic anhydride (PMDA) is selected as the end-group
modifier; during the hot-melt blending of polylactic acid with PMDA, the
mass/molar mass ratio of polylactic acid to PMDA is 1:2.
Furthermore, the step of hot-melt blending of the polylactic acid with the
end-group modifier includes:
providing an internal mixer with the set temperature of 175-185 0C and a
rotation speed of 12-25 rpm, adding an antioxidant to molten polylactic acid,
mixing for 1-2 min, adding an end-group modifier, mixing for 1-2 min, then
increasing the rotation speed to 45-65 rpm, so that the polylactic acid reacts
with the end-group modifier for 10-20 min.
In the range of the above temperature, speed and mixing time, thermal
oxygen degradation of polylactic acid under strong shear conditions can be
avoided effectively, and the adequate mixing and reaction of polylactic acid
and the end-group modifier can be ensured.
Exemplarily, the step of hot-melt blending of the polylactic acid with the
end-group modifier includes: providing an internal mixer with the set
temperature of 180 0C and a rotation speed of 20 rpm, adding an antioxidant
to molten polylactic acid, mixing for 1 min, adding an end-group modifier,
mixing for 1 min, then increasing the rotation speed to 60 rpm, so that the
polylactic acid reacts with the end-group modifier for 15 min.
Furthermore, the polylactic acid is further dried at 100-106 0C for 20-25 h
before internal mixing.
Furthermore optionally, the polylactic acid is further dried at 103-1050 C
for 20-25 h before internal mixing.
Exemplarily, the polylactic acid is further dried at 100 0C for 25 h before
internal mixing, or dried at 103 0C for 22 h, or dried at 1050 C for 20 h.
In other optional embodiments of the present application, the step of hot
melt blending of the polylactic acid with the end-group modifier includes:
evenly mixing the end-group modifier, an antioxidant and the polylactic
acid, and then granulating and extruding by a twin screw extruder at 180-250
rpm. The rotation speed of the extruder affects the residence time and the
shear rate of the above raw materials in the extruder. By setting the rotation
speed in the range of 180-250 rpm, good granulation and extrusion effect can
be ensured. Furthermore optionally, the granulation extrusion effect is
optimum at the rotation speed of 200 rpm.
Furthermore, temperature range of a section from a feed port to a
discharge port of the twin-screw extruder is as follows: Zone 1: 145-155C,
Zone 2:155-165 0C, Zone 3: 165-175 0C, Zone 4: 175-185°C, Zone 5: 175
185 0C,Zone 6:175-185 0C, and Zone 7:170-180°C.
Exemplarily, the end-group modifier, the antioxidant and the polylactic
acid are evenly mixed, and then granulated and extruded by a twin screw
extruder, wherein temperature range of a section from a feed port to a
discharge port of the twin-screw extruder is as follows: Zone 1: 1500 C, Zone 2:
160 0C, Zone 3: 170 0C, Zone 4: 180 0C, Zone 5: 1800 C, Zone 6: 1800 C, and
Zone 7: 1750 C.
Furthermore, antioxidant 1010 can be selected as the above antioxidant.
The chemical name of antioxidant 1010 is tetrakis[p-(3,5-di-tert-butyl-4
hydroxyphenyl)propionic acid] pentaerythritol ester, white crystalline powder
with stable chemical properties, and can effectively prevent polymer oxidation
when used in polylactic acid.
Furthermore, the addition amount of antioxidant accounts for 0.2%-1% of
polylactic acid by mass fraction.
In other optional embodiments of the present application, the antioxidant
can be selected from antioxidant 168. Furthermore optionally, the addition
amount of antioxidant 168 accounts for 0.5%-0.85% of polylactic acid by
mass fraction.
step S2. preparing modified corncob powder.
Furthermore, a step of preparing the modified corncob powder includes:
soaking a corncob raw material in an alkaline solution, cleaning to neutral,
and then microwave blasting into powder.
Through alkaline washing and microwave blasting, cellulose of corncob
can be exposed, and cellulose contains abundant hydroxyl groups which can
significantly increase the probability of esterification reaction of polylactic acid
with corncob powder surface, so that the polycarboxy functional groups at a
chain end of end-modified polylactic acid react with a large number of
hydroxyl groups to generate high-density ester groups. Therefore, the
chemical bonding between polylactic acid matrix and corncob powder is
significantly increased, the interfacial strength between the two is increased,
and the dispersion and crosslinking of corncob powder is promoted.
Furthermore, the above alkaline solution is sodium hydroxide solution
with a mass fraction of 5-15%, and the soaking time is 30-180 min.
Exemplarily, the soaking time is 180 min when the alkaline solution is 5%
sodium hydroxide solution; and the soaking time is 30 min when the alkaline
solution is 15% sodium hydroxide solution.
Furthermore, 0.1-0.2 g of corncob raw material is soaked in each milliliter
of alkaline solution.
Exemplarily, 240 g of corncob raw material is soaked in 1400 ml of 15%
sodium hydroxide solution.
Furthermore, the above sodium hydroxide solution is prepared by
dissolving sodium hydroxide in distilled water.
Furthermore, the microwave blasting refers to microwave processing at
the microwave frequency of 300 MHz to 3 GHz and at the microwave power
of 500-1000 W for 1-2 min.
Exemplarily, the wet corncob powder after washing is processed in a
microwave oven with a microwave frequency of 2.4 GHz and a set power of
600 W for 1 min.
Further, after microwave processing, the corncob powder is dried until the
water content of the corncob powder is lower than 3%.
Exemplarily, the corncob powder subjected to microwave processing is
dried in a blast air oven at 900 C until the water content of the corncob powder
is lower than 3%.
step S3: hot-melt blending the end-group modified polylactic acid with the
modified corncob powder;
Furthermore, during the hot-melt blending of the end-group modified
polylactic acid with the modified corncob powder, the addition amount of the
modified corncob powder accounts for 20-75% of the corncob
powder/polylactic acid composite material by mass fraction.
The method adopted by the embodiments of the present application can
ensure high interfacial strength and overall mechanical property of the
corncob powder and polylactic acid at high corncob powder filling rate.
Furthermore optionally, during the hot-melt blending of the end-group
modified polylactic acid with the modified corncob powder, the addition
amount of the modified corncob powder accounts for 40-70% of the corncob
powder/polylactic acid composite material by mass fraction.
Furthermore optionally, during the hot-melt blending of the end-group
modified polylactic acid with the modified corncob powder, the addition
amount of the modified corncob powder accounts for 45-65% of the corncob
powder/polylactic acid composite material by mass fraction.
Exemplarily, during the hot-melt blending of the end-group modified
polylactic acid with the modified corncob powder, the addition amount of the modified corncob powder accounts for 50%, 55%, 60% or 65% of the corncob powder/polylactic acid composite material by mass fraction.
Furthermore, the step of hot-melt blending of the end-group modified
polylactic acid with the modified corncob powder includes:
providing an internal mixer with the set temperature of 175-1850 C, and
mixing the end-group modified polylactic acid and the modified corncob
powder at 25-35 rpm for 5-10 min.
Based on the above temperature, speed and mixing time, thermal oxygen
degradation of polylactic acid under strong shear conditions can be avoided
effectively, and the adequate mixing and reaction of polylactic acid and
corncob powder can be ensured.
Exemplarily, the step of hot-melt blending of the end-group modified
polylactic acid with the modified corncob powder includes: providing an
internal mixer with the set temperature of 1800 C, and mixing the end-group
modified polylactic acid with the modified corncob powder at 30 rpm for 8 min.
In other optional embodiments of the present application, the step of hot-melt
blending of the end-group modified polylactic acid with the modified corncob
powder includes:
evenly mixing the end-group modified polylactic acid and the modified
corncob powder, and then granulating and extruding by a twin screw extruder
at 150-220 rpm. The ration speed is set in the range of 150-220 rpm, which
can ensure a full reaction between polylactic acid and modified corncob
powder as well as moderate extrusion pressure. Furthermore optionally, the
granulation extrusion effect is optimum at the rotation speed of 180 rpm.
Furthermore, temperature range of a section from a feed port to a discharge port of the twin-screw extruder is as follows: Zone 1: 145-155C,
Zone 2:155-165 0C, Zone 3: 165-175 0C, Zone 4: 175-185 0C, Zone 5: 175
185 0C,Zone 6:175-185 0C, and Zone 7:180-190°C.
Exemplarily, the end-group modified polylactic acid and the modified
corncob powder are evenly mixed, and then granulated and extruded by a
twin screw extruder, wherein temperature range of a section from a feed port
to a discharge port of the twin-screw extruder is as follows: Zone 1: 150C,
Zone 2:160 0C, Zone 3: 170 0C, Zone 4: 1800 C, Zone 5: 1800 C, Zone 6: 180C,
and Zone 7: 1850 C.
Some embodiments of the present application further provide a corncob
powder/polylactic acid composite material, which is prepared by the method
for preparing a corncob powder/polylactic acid composite material provided by
the previous embodiments. The corncob powder/polylactic acid composite
material has high interfacial strength between corncob powder and polylactic
acid, and excellent mechanical property.
Furthermore, the corncob powder/polylactic acid composite material has
a wide range of applications and can be used for preparing sheets, films, bar
fibers and the like.
Exemplarily, the prepared corncob powder/polylactic acid composite
material is pressed into dumbbell-shaped splines at a temperature of 1800 C
and a pressure of 15 MPa.
The features and properties of the present application are described in
further detail below in conjunction with embodiments.
Example 1
A corncob powder/polylactic acid composite material was prepared by the following steps:
Drying polylactic acid at 106 0C for 20 h; then adding the dried polylactic
acid to an internal mixer at a temperature of 180 0C and a rotation speed of 20
rpm, fully melting, adding antioxidant 1010 and mixing for 1 min, wherein the
mass fraction of antioxidant 1010 accounts for 0.5% of polylactic acid; adding
pyromellitic anhydride and mixing for 1 min, wherein the molar ratio of
pyromellitic anhydride to polylactic acid was 2:1; and increasing the rotation
speed to 60 rpm and the reaction time to 15 min to obtain the end-group
modified polylactic acid.
With 1200 ml of distilled water as solvent, preparing 15% sodium
hydroxide solution, and then soaking 200 g of corncob powder in the sodium
hydroxide solution while stirring continuously for 30 min; after the complete
reaction, washing the treated corncob powder to neutral for later use;
processing the washed moist corncob powder in a microwave oven at a
microwave frequency of 2.4 GHz and a microwave power of 600 W for 1.5
min; and drying the corncob powder in a blast air oven at 900 C until the water
content of the corncob powder is lower than 3% to obtain the modified
corncob powder.
Adding the modified corncob powder and the end-group modified
polylactic acid to an internal mixer at a set temperature of 180 0C and a
rotation speed of 30 rpm, and blending for 8 min to obtain the corncob
powder/polylactic acid composite material; wherein the addition amount of the
modified corncob powder accounts for 75% of the corncob powder/polylactic
acid composite material by mass fraction.
Example 2
A corncob powder/polylactic acid composite material was prepared by the
following steps:
Drying polylactic acid at 100 0C for 25 h. then adding the dried polylactic
acid to an internal mixer at a temperature of 175 0C and a rotation speed of 15
rpm, fully melting, adding antioxidant 1010 and mixing for 2 min, wherein the
mass fraction of antioxidant 1010 accounts for 0.5% of polylactic acid; adding
pyromellitic anhydride and mixing for 2 min, wherein the molar ratio of
pyromellitic anhydride to polylactic acid was 1:1; and increasing the rotation
speed to 55 rpm and the reaction time to 10 min to obtain the end-group
modified polylactic acid.
With 1200 ml of distilled water as solvent, preparing 5% sodium
hydroxide solution, and then soaking 150 g of corncob powder in the sodium
hydroxide solution while stirring continuously for 180 min; after the complete
reaction, washing the treated corncob powder to neutral for later use;
processing the washed moist corncob powder in a microwave generator at a
microwave frequency of 3 GHz and a microwave power of 500 W for 1 min;
and drying the corncob powder in a blast air oven at 900 C until the water
content of the corncob powder is lower than 3% to obtain the modified
corncob powder.
Adding the modified corncob powder and the end-group modified
polylactic acid to an internal mixer at a set temperature of 175 0C and a
rotation speed of 25 rpm, and blending for 10 min to obtain the corncob
powder/polylactic acid composite material; wherein the addition amount of the
modified corncob powder accounts for 20% of the corncob powder/polylactic
acid composite material by mass fraction.
Example 3
A corncob powder/polylactic acid composite material was prepared by the
following steps:
Drying polylactic acid at 102 0C for 24 h; then adding the dried polylactic
acid to an internal mixer at a temperature of 185 0C and a rotation speed of 25
rpm, fully melting, adding antioxidant 1010 and mixing for 1.5 min, wherein the
mass fraction of antioxidant 1010 accounts for 0.5% of polylactic acid; adding
pyromellitic anhydride and mixing for 1.5 min, wherein the molar ratio of
pyromellitic anhydride to polylactic acid was 4:1; and increasing the rotation
speed to 65 rpm and the reaction time to 15 min to obtain the end-group
modified polylactic acid.
With 1200 ml of distilled water as solvent, preparing 15% sodium
hydroxide solution, and then soaking 150 g of corncob powder in the sodium
hydroxide solution while stirring continuously for 150 min; after the complete
reaction, washing the treated corncob powder to neutral for later use;
processing the washed moist corncob powder in a microwave oven at a
microwave frequency of 2.4 GHz and a microwave power of 1000 W for 1.5
min; and drying the corncob powder in a blast air oven at 900 C until the water
content of the corncob powder is lower than 3% to obtain the modified
corncob powder.
Adding the modified corncob powder and the end-group modified
polylactic acid to an internal mixer at a set temperature of 185 0C and a
rotation speed of 35 rpm, and blending for 7 min to obtain the corncob
powder/polylactic acid composite material; wherein the addition amount of the
modified corncob powder accounts for 50% of the corncob powder/polylactic acid composite material by mass fraction.
Example 4
A corncob powder/polylactic acid composite material was prepared by the
following steps:
Drying polylactic acid at 102 0C for 24 h; then adding the dried polylactic
acid to an internal mixer at a temperature of 185 0C and a rotation speed of 25
rpm, fully melting, adding antioxidant 1010 and mixing for 1.5 min, wherein the
mass fraction of antioxidant 1010 accounts for 0.5% of polylactic acid; adding
pyromellitic anhydride and mixing for 1.5 min, wherein the molar ratio of
pyromellitic anhydride to polylactic acid was 2:1; and increasing the rotation
speed to 65 rpm and the reaction time to 15 min to obtain the end-group
modified polylactic acid.
With 1200 ml of distilled water as solvent, preparing 15% sodium
hydroxide solution, and then soaking 150 g of corncob powder in the sodium
hydroxide solution while stirring continuously for 150 min; after the complete
reaction, washing the treated corncob powder to neutral for later use;
processing the washed moist corncob powder in a microwave generator at a
microwave frequency of 2 GHz and a microwave power of 700 W for 1.5 min;
and drying the corncob powder in a blast air oven at 900 C until the water
content of the corncob powder is lower than 3% to obtain the modified
corncob powder.
Adding the modified corncob powder and the end-group modified
polylactic acid to an internal mixer at a set temperature of 185 0C and a
rotation speed of 25 rpm, and blending for 7 min to obtain the corncob
powder/polylactic acid composite material; wherein the addition amount of the modified corncob powder accounts for 40% of the corncob powder/polylactic acid composite material by mass fraction.
Example 5
A corncob powder/polylactic acid composite material was prepared by the
following steps:
Drying polylactic acid at 105 0C for 21 h; then adding the dried polylactic
acid to an internal mixer at a temperature of 180 0C and a rotation speed of 20
rpm, fully melting, adding antioxidant 1010 and mixing for 1 min, wherein the
mass fraction of antioxidant 1010 accounts for 0.5% of polylactic acid; adding
pyromellitic acid and mixing for 1 min, wherein the molar ratio of pyromellitic
anhydride to polylactic acid was 2:1; and increasing the rotation speed to 60
rpm and the reaction time to 15 min to obtain end-group modified polylactic
acid.
With 1200 ml of distilled water as solvent, preparing 15% sodium
hydroxide solution, and then soaking 200 g of corncob powder in the sodium
hydroxide solution while stirring continuously for 30 min; after the complete
reaction, washing the treated corncob powder to neutral for later use;
processing the washed moist corncob powder in a microwave oven at a
microwave frequency of 300 MHz and a microwave power of 800 W for 1.5
min; and drying the corncob powder in a blast air oven at 900 C until the water
content of the corncob powder is lower than 3% to obtain the modified
corncob powder.
Adding the modified corncob powder and the end-group modified
polylactic acid to an internal mixer at a set temperature of 180 0C and a
rotation speed of 30 rpm, and blending for 8 min to obtain the corncob powder/polylactic acid composite material; wherein the addition amount of the modified corncob powder accounts for 45% of the corncob powder/polylactic acid composite material by mass fraction.
Example 6
A corncob powder/polylactic acid composite material was prepared by
the following steps:
Drying polylactic acid at 105 0C for 21 h; adding
naphthalenetetracarboxylic anhydride and dried polylactic acid to a high
speed mixer according to a molar ratio of 2:1, and mixing for 5 min; then
granulating and extruding by a twin-screw extruder at 180 rpm, wherein
temperature range of a section from a feed port to a discharge port of the
twin-screw extruder was as follows: Zone 1: 153 0C, Zone 2: 1640 C, Zone 3:
174 0C, Zone 4: 184 0C, Zone 5: 1840 C, Zone 6: 1840 C, and Zone 7: 175C;
and finally, obtaining the modified polylactic acid.
With 1200 ml of distilled water as solvent, preparing 12% sodium
hydroxide solution, and then soaking 220 g of corncob powder in the sodium
hydroxide solution while stirring continuously for 60 min; after the complete
reaction, washing the treated corncob powder to neutral for later use;
processing the washed moist corncob powder in a microwave oven at a
microwave frequency of 2.4 GHz and a microwave power of 1000 W for 1.5
min; and drying the corncob powder in a blast air oven at 900 C until the water
content of the corncob powder is lower than 3% to obtain the modified
corncob powder.
Evenly mixing the modified corncob powder and the end-group modified
polylactic acid, and then granulating and extruding by a double-screw extruder at 150 rpm, wherein temperature range of a section from a feed port to a discharge port of the twin-screw extruder was as follows: Zone 1: 145°C,
Zone 2: 155 0C, Zone 3: 1650 C, Zone 4: 1750 C, Zone 5: 175C, Zone 6: 175C,
and Zone 7: 180°C; and finally, obtaining the corncob powder/polylactic acid
composite material, wherein the addition amount of the modified corncob
powder accounts for 45% of the composite material by mass fraction.
Example 7
A corncob powder/polylactic acid composite material was prepared by the
following steps:
Drying polylactic acid at 106 0C for 20 h, adding
naphthalenetetracarboxylic acid and dried polylactic acid into a high-speed
mixer according to a molar ratio of 2:1, mixing for 5 min, and then granulating
and extruding by a twin-screw extruder at 250 rpm, wherein temperature
range of a section from a feed port to a discharge port of the twin-screw
extruder was as follows: Zone 1: 1550 C, Zone 2: 1650 C, Zone 3: 175C, Zone
4: 1850 C, Zone 5: 1850 C, Zone 6: 1850 C, and Zone 7: 180°C; and finally,
obtaining the modified polylactic acid.
With 1200 ml of distilled water as solvent, preparing 10% sodium
hydroxide solution, and then soaking 150 g of corncob powder in the sodium
hydroxide solution while stirring continuously for 60 min; after the complete
reaction, washing the treated corncob powder to neutral for later use;
processing the washed moist corncob powder in a microwave generator at a
microwave frequency of 600 MHz and a microwave power of 800 W for 1.5
min; and drying the corncob powder in a blast air oven at 900 C until the water
content of the corncob powder is lower than 3% to obtain the modified corncob powder.
Evenly mixing the modified corncob powder and the end-group modified
polylactic acid, and then granulating and extruding by a double-screw extruder
at 220 rpm, wherein temperature range of a section from a feed port to a
discharge port of the twin-screw extruder was as follows: Zone 1: 145C,
Zone 2: 155 0C, Zone 3: 1650 C, Zone 4: 1750 C, Zone 5: 175C, Zone 6: 175C,
and Zone 7: 180°C; and finally, obtaining the corncob powder/polylactic acid
composite material, wherein the addition amount of the modified corncob
powder accounts for 55% of the corncob powder/polylactic acid composite
material by mass fraction.
Example 8
A corncob powder/polylactic acid composite material was prepared by the
following steps:
Drying polylactic acid at 101 0C for 25 h; adding
cyclopentanetetracarboxylic dianhydride and dried polylactic acid to a high
speed mixer according to a molar ratio of 2:1, and mixing for 5 min; then
granulating and extruding by a twin-screw extruder at 200 rpm, wherein
temperature range of a section from a feed port to a discharge port of the
twin-screw extruder was as follows: Zone 1: 155 0C, Zone 2: 1650 C, Zone 3:
175 0C, Zone 4: 185 0C, Zone 5:1850 C, Zone 6:1850 C, and Zone 7:180°C;
and finally, obtaining the modified polylactic acid.
With 1200 ml of distilled water as solvent, preparing 5% sodium
hydroxide solution, and then soaking 150 g of corncob powder in the sodium
hydroxide solution while stirring continuously for 180 min; after the complete
reaction, washing the treated corncob powder to neutral for later use; processing the washed moist corncob powder in a microwave reactor at a microwave frequency of 3 GHz and a microwave power of 500 W for 1 min; and drying the corncob powder in a blast air oven at 900 C until the water content of the corncob powder is lower than 3% to obtain the modified corncob powder.
Evenly mixing the modified corncob powder and the end-group modified
polylactic acid, and then granulating and extruding by a double-screw extruder
at 180 rpm, wherein temperature range of a section from a feed port to a
discharge port of the twin-screw extruder was as follows: Zone 1: 146C,
Zone 2: 156 0C, Zone 3: 1660 C, Zone 4: 1770 C, Zone 5: 177C, Zone 6: 177C,
and Zone 7: 182C; and finally, obtaining the corncob powder/polylactic acid
composite material, wherein the addition amount of the modified corncob
powder accounts for 70% of the corncob powder/polylactic acid composite
material by mass fraction.
Example 9
A corncob powder/polylactic acid composite material was prepared by the
following steps:
Drying polylactic acid at 102 0C for 24 h; adding
cyclopentanetetracarboxylic acid and dried polylactic acid to a high-speed
mixer according to a molar ratio of 2:1, and mixing for 5 min; then granulating
and extruding by a twin-screw extruder at 220 rpm, wherein temperature
range of a section from a feed port to a discharge port of the twin-screw
extruder was as follows: Zone 1: 1470 C, Zone 2: 1550 C, Zone 3: 168C, Zone
4: 1780 C, Zone 5: 1780 C, Zone 6: 1780 C, and Zone 7: 175C; and finally,
obtaining the modified polylactic acid.
With 1200 ml of distilled water as solvent, preparing 12% sodium
hydroxide solution, and then soaking 150 g of corncob powder in the sodium
hydroxide solution while stirring continuously for 60 min; after the complete
reaction, washing the treated corncob powder to neutral for later use;
processing the washed moist corncob powder in a microwave generator at a
microwave frequency of 1.6 GHz and a microwave power of 1000 W for 1 min;
and drying the corncob powder in a blast air oven at 900 C until the water
content of the corncob powder is lower than 3% to obtain the modified
corncob powder.
Evenly mixing the modified corncob powder and the end-group modified
polylactic acid, and then granulating and extruding by a double-screw extruder
at 200 rpm, wherein temperature range of a section from a feed port to a
discharge port of the twin-screw extruder was as follows: Zone 1: 145C,
Zone 2: 155 0C, Zone 3: 1650 C, Zone 4: 1750 C, Zone 5: 1750 C, Zone 6: 175C,
and Zone 7: 185C; and finally, obtaining the corncob powder/polylactic acid
composite material, wherein the addition amount of the modified corncob
powder accounts for 65% of the corncob powder/polylactic acid composite
material by mass fraction.
Comparison Example 1
A corncob powder/polylactic acid composite material is provided. The
preparation steps are basically the same as those in Example 1, except that
neither polylactic acid nor corncob powder is modified; instead, corncob
powder and polylactic acid are directly blended.
Comparison Example 2
A corncob powder/polylactic acid composite material is provided. The preparation steps are basically the same as those in Example 3, except that corncob powder is not modified; instead, modified polylactic acid and corncob powder are directly blended.
Comparison Example 3
A corncob powder/polylactic acid composite material is provided. The
preparation steps are basically the same as those in Example 3, except that
polylactic acid is not modified; instead, corncob powder and polylactic acid are
directly blended.
The properties of corncob powder/polylactic acid composites provided in
Examples 1-9 and Comparison Examples 1-3 were investigated.
In Test Example 1, morphological characteristics of frozen brittle sections
of the corncob powder/polylactic acid composites provided in Example 1 and
Comparison Example 1 were observed under a scanning electron microscope.
The results are shown in FIGS. 1-4.
FIG. 1 and FIG. 2 are SEM graphs of a composite material prepared by
blending polylactic acid and corncob powder provided in Comparison
Example 1 without modification. As shown, the interface between the two
phases is clear, there is obvious gap between corncob particles and polylactic
acid matrix, and corncob powder is unevenly dispersed. Therefore, corncob
powder is simply surrounded by polylactic acid matrix and can be easily pulled
out from polylactic acid matrix, indicating a poor binding between polylactic
acid and corncob powder, and thus poor mechanical property of the
composite material.
FIG. 3 and FIG. 4 show SEM graphs of brittle section of a polylactic
acid/corncob powder composite material provided in Example 1. As shown, the interface between the two phases is fuzzy, and there is no obvious gap between corncob powder and polylactic acid matrix. Compared with FIG. 1 and FIG. 2, corncob powder is dispersed more evenly. In addition, a large number of filaments are distributed on the surface of corncob particles, and some corncob particles are connected by filaments, demonstrating that polycarboxy groups at a chain end of the end-group modified polylactic acid were esterified with the hydroxyl groups on the surface of corncob powder to form a chemical bonding and a cross-linked network when corncob particles are bonded by polylactic acid molecular chains.
In Test Example 2, tensile properties of corncob powder/polylactic acid
composites provided in Examples 1-9 and Comparison Examples 1-3 were
tested, and the specific steps are as follows:
The corncob powder/polylactic acid composite materials provided by
Examples 1-9 and Comparison Examples 1-3 were pressed into dumbbell
shaped splines at a temperature of 180 0C and a pressure of 15 MPa.
The dumbbell-shaped specimens were stretched at a constant speed as
per a stretching rate of 20 mm/min, which complies with the GB/T 1040. 2
2006.
The test results are shown in the table below:
Tensile Strength Elongation at Break Example 1 56MPa 10.2% Example 2 54MPa 12.1% Example 3 70MPa 18.2% Example 4 64MPa 17.8% Example 5 60MPa 15.9% Example 6 61MPa 15.4% Example 7 56MPa 14.4% Example 8 52MPa 13.9% Example 9 57MPa 12.9% Comparison Example 1 38Mpa 4.5% Comparison Example 2 42MPa 6.1% Comparison Example 3 43MPa 6.4%
According to the data in the above table, the tensile strength and
elongation at break of corncob powder/polylactic acid composites provided in
Examples 1-9 are obviously improved compared with those of common
composites provided in Comparison Example 1. Therefore, the interfacial
strength of the corncob powder/polylactic acid composite material provided by
the embodiments of the present application can be effectively improved, and
the cross-linking between corncob powder is promoted, so that the prepared
corncob powder/polylactic acid composite material still has excellent
mechanical properties even at high corncob powder filling rate.
Furthermore, compared with Comparative Example 2 and Comparative
Example 3, the tensile strength and elongation at break of corncob
powder/polylactic acid composites provided in Examples 1-9 of the present
application are also significantly improved. Compared with Comparative
Example 2, the modification of corncob powder can expose cellulose with a
large number of hydroxyl groups on the surface of corncob, thus significantly
increasing the chemical bonding between polylactic acid matrix and corncob
powder. Compared with Comparative Example 3, due to the modification of
the PMDA end group, the end group structure of polylactic acid molecular
chain is changed from monohydroxy group to rigid polycarboxy ring group,
and the reaction site with hydroxyl groups is increased. Therefore, the
interfacial strength and stress conduction efficiency between polylactic acid
and corncob powder are improved, the formation of cross-linked network
between corncob powder promoted, and the overall mechanical properties of
composite materials is improved.
The foregoing is only a preferred embodiment of the present application,
and is not intended to limit the present application. For a person of ordinary
skill in the art, various modifications and variations can be made to the
present application. Any modification, equivalent replacement and
improvement made within the spirit and principle of the present application
should fall within the scope of protection of the present application.
Claims (10)
1. A method for preparing a corncob powder/polylactic acid composite
material, characterized by comprising reacting end-group modified polylactic
acid and modified corncob powder through hot-melt blending;
wherein a chain end of the end-group modified polylactic acid is a rigid
ring molecule with a plurality of carboxyl groups, and polyhydroxy cellulose is
exposed on the surface of the modified corncob powder.
2. The method for preparing a corncob powder/polylactic acid composite
material according to claim 1, characterized in that a step of preparing the
end-group modified polylactic acid comprises hot-melt blending of polylactic
acid with an end-group modifier, wherein the end-group modifier is
polyanhydride with a benzene ring, a naphthalene ring or a cyclopentane rigid
ring molecule; or the end-group modifier is a polycarboxy compound with a
benzene ring, a naphthalene ring or a cyclopentane rigid ring molecule;
optionally, the end-group modifier is selected from any one of pyromellitic
anhydride, pyromellitic acid, trimellitic anhydride, trimellitic acid,
naphthalenetetracarboxylic anhydride, naphthalenetetracarboxylic acid,
cyclopentanetetracarboxylic dianhydride or cyclopentanetetracarboxylic acid;
and
optionally, the mass/molar mass ratio of the polylactic acid to the end
group modifier is 1:1-1:4.
3. The method for preparing a corncob powder/polylactic acid composite
material according to claim 2, characterized in that the step of hot-melt
blending of the polylactic acid with the end-group modifier comprises:
providing an internal mixer with the set temperature of 175-185 0C and a rotation speed of 15-25 rpm, adding an antioxidant to molten polylactic acid, mixing for 1-2 min, adding an end-group modifier, mixing for 1-2 min, then increasing the rotation speed to 45-65 rpm, so that the polylactic acid reacts with the end-group modifier for 10-20 min; wherein optionally, the polylactic acid is further dried at 100-106 0C for 20-25 h before internal mixing.
4. The method for preparing a corncob powder/polylactic acid composite
material according to claim 2, characterized in that the step of hot-melt
blending of the polylactic acid with the end-group modifier comprises:
evenly mixing the end-group modifier, an antioxidant and the polylactic
acid, and then granulating and extruding by a twin screw extruder at 180-250
rpm, wherein temperature range of a section from a feed port to a discharge
port of the twin-screw extruder is as follows: Zone 1: 145-1550 C, Zone 2:155
165 0C, Zone 3: 165-175 0C, Zone 4: 175-185 0 C, Zone 5: 175-1850 C, Zone 6:
175-185 0C, and Zone 7: 170-180°C; and
optionally, the polylactic acid is further dried at 100-106 0C for 20-25 h
before extruded by the twin screw extruder.
5. The method for preparing a corncob powder/polylactic acid composite
material according to any one of claims 1 to 4, characterized in that a step of
preparing the modified corncob powder comprises:
soaking a corncob raw material in an alkaline solution, cleaning to neutral,
and then microwave blasting into powder;
wherein the alkaline solution is 5-15% sodium hydroxide aqueous
solution, and the soaking time is 30-180 min; 0.1-0.2 g of corncob powder
raw material is soaked in each milliliter of the alkaline solution; and the microwave blasting refers to microwave processing at the microwave frequency of 300 MHz to 3 GHz and at the microwave power of 500-1000 W for 1-2 min.
6. The method for preparing a corncob powder/polylactic acid composite
material according to claim 5, characterized in that a step of preparing the
modified corncob powder comprises:
after microwave processing, drying the corncob powder until the water
content of the corncob powder is lower than 3%.
7. The method for preparing a corncob powder/polylactic acid composite
material according to claim 1, characterized in that during the hot-melt
blending of the end-group modified polylactic acid with the modified corncob
powder, the addition amount of the modified corncob powder accounts for 20
% of the corncob powder/polylactic acid composite material by mass
fraction.
8. The method for preparing a corncob powder/polylactic acid composite
material according to claim 3, characterized in that the step of hot-melt
blending of the end-group modified polylactic acid with the modified corncob
powder comprises:
providing an internal mixer with the set temperature of 175-1850 C, and
mixing the end-group modified polylactic acid and the modified corncob
powder at 25-35 rpm for 5-10 min.
9. The method for preparing a corncob powder/polylactic acid composite
material according to claim 4, characterized in that the step of hot-melt
blending of the end-group modified polylactic acid with the modified corncob
powder comprises: evenly mixing the end-group modified polylactic acid and the modified corncob powder, and then granulating and extruding by a twin screw extruder at 150-220 rpm, wherein temperature range of a section from a feed port to a discharge port of the twin-screw extruder is as follows: Zone 1: 145-155C,
Zone 2:155-165 0C, Zone 3: 165-175 0C, Zone 4: 175-185 0C, Zone 5: 175
185 0C,Zone 6:175-185 0C, and Zone 7:180-190°C.
10. A corncob powder/polylactic acid composite material, characterized in
that the corncob powder/polylactic acid composite material is prepared by the
method for preparing a corncob powder/polylactic acid composite material
according to any one of claims 1-9.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU2021104323A AU2021104323A4 (en) | 2021-07-20 | 2021-07-20 | Corncob Powder/Polylactic Acid Composite Material and Preparation Method Therefor |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU2021104323A AU2021104323A4 (en) | 2021-07-20 | 2021-07-20 | Corncob Powder/Polylactic Acid Composite Material and Preparation Method Therefor |
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| Publication Number | Publication Date |
|---|---|
| AU2021104323A4 true AU2021104323A4 (en) | 2021-09-09 |
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ID=77589231
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| AU2021104323A Ceased AU2021104323A4 (en) | 2021-07-20 | 2021-07-20 | Corncob Powder/Polylactic Acid Composite Material and Preparation Method Therefor |
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| Country | Link |
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| AU (1) | AU2021104323A4 (en) |
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2021
- 2021-07-20 AU AU2021104323A patent/AU2021104323A4/en not_active Ceased
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