CN115926362A - Composite material for enhancing PLA melt strength and preparation method and application thereof - Google Patents
Composite material for enhancing PLA melt strength and preparation method and application thereof Download PDFInfo
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- CN115926362A CN115926362A CN202211516627.3A CN202211516627A CN115926362A CN 115926362 A CN115926362 A CN 115926362A CN 202211516627 A CN202211516627 A CN 202211516627A CN 115926362 A CN115926362 A CN 115926362A
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W90/00—Enabling technologies or technologies with a potential or indirect contribution to greenhouse gas [GHG] emissions mitigation
- Y02W90/10—Bio-packaging, e.g. packing containers made from renewable resources or bio-plastics
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Abstract
The invention discloses a composite material for enhancing PLA melt strength, a preparation method and an application thereof, wherein the composite material is prepared from the following components in parts by weight: 10-20 parts of SEBS (styrene-ethylene-butadiene-styrene), 5-10 parts of polyester-polyether block copolymer, 5-8 parts of SEBS-g-MAH (maleic anhydride-maleic anhydride) and 0.5-2 parts of oxidized PE (polyethylene) wax; and carrying out melt blending and extrusion granulation by a double-screw extruder to obtain the SEBS/polyester-polyether block copolymer/SEBS-g-MAH composite material of white or milky granules. Melting and blending PLA, the composite material and the oxidized PE wax by a double-screw extruder according to the parts by weight to obtain the high melt strengthPLA. The reinforced PLA has the following characteristics: the degree of chain entanglement is 3.5-4.1mol/cm 3 The melt strength is 13.6-16.8cN, the tensile strength is 49.5-64.2MPa, and the elongation at break is 25.4-64.5%.
Description
Technical Field
The invention relates to the technical field of polymer composite materials, in particular to a PLA composite material for producing disposable plastic films and a preparation method and application thereof.
Background
Along with the rapid development of logistics economy, the demand of disposable plastic film products is rapidly increased, and the disposable plastic film products become indispensable flexible packaging materials for the development of modern logistics industry. The disposable plastic film used in the prior art is petroleum-based polyethylene and polypropylene film. Petroleum belongs to non-renewable resources, and the cost price of polyethylene and polypropylene films is increased due to the continuous increase of the price in the near future. In addition, polyethylene and polypropylene films are difficult to recycle after being used and are difficult to naturally degrade, thereby causing great pollution to the ecological environment.
Polylactic acid (PLA) is a biodegradable bio-based material that has the most potential to replace polyethylene, polypropylene films on a scale. However, the PLA has a low melt strength due to its high critical entanglement molecular weight, and the melt is stretched to exhibit strain softening, which restricts the molding process of the PLA in blow molding equipment such as extrusion blow molding and stretch blow molding, and the film has a low tensile strength. To achieve the mechanical strength of a PLA film for its use, manufacturers can only increase the film thickness, which undoubtedly increases the cost of using PLA films. Therefore, in the PLA forming process, the PLA chain entanglement molecular weight in the melt is reduced, the melt strength can be fundamentally improved, and the mechanical strength of the PLA film is improved.
The long-chain branched PLA prepared by polymerization can improve the entanglement degree of PLA melt chains, thereby improving the melt strength of the PLA. However, the preparation of long-chain branched PLA by polymerization reaction is complex in process and high in input cost of a polymerization production line, so that the large-scale production of the long-chain branched PLA is limited.
Disclosure of Invention
One of the purposes of the invention is to provide a composite material for enhancing the melt strength of PLA, which can effectively improve the melt strength and the mechanical strength of the PLA.
The invention also aims to provide the preparation method of the composite material for enhancing the melt strength of the PLA, which has simple process and low production cost.
It is a further object of the present invention to provide the use of the above composite material for enhancing the melt strength of PLA.
In order to realize the purpose, the technical scheme adopted by the invention is as follows:
in a first aspect, the invention provides a composite material for enhancing the melt strength of PLA, which is prepared from the following components in parts by weight: 10-20 parts of hydrogenated styrene-butadiene-styrene block copolymer (SEBS); 5-10 parts of a polyester-polyether block copolymer; 5-8 parts of maleic anhydride grafted hydrogenated styrene-butadiene-styrene block copolymer (SEBS-g-MAH); 0.5-2 parts of oxidized PE wax; wherein the SEBS has a star-chain structure and a styrene/rubber ratio of 30/70.
Preferably, the polyester-polyether block copolymer has a linear chain structure and a polyester/polyether ratio of 38/62.
Preferably, the SEBS-g-MAH is a linear chain structure, the grafting rate of maleic anhydride is 1.5%, and the styrene/rubber ratio is 30/70.
Preferably, the oxidized PE wax has a molecular weight of 2500 to 3200.
In a second aspect, the present invention provides a method for preparing the above composite material for enhancing PLA melt strength, comprising the steps of:
(1) Weighing SEBS, a polyester-polyether block copolymer, SEBS-g-MAH and oxidized PE wax according to a ratio, and adding into a mixer to mix uniformly to obtain a premix;
(2) Adding the premix obtained in the step (1) into a double-screw extruder for melt blending, extruding and granulating; the temperatures of the working sections of the twin-screw extruder were set at 180 ℃, 190 ℃, 195 ℃, 190 ℃, 185 ℃, 170 ℃, the head temperature was 170 ℃ and the screw speed was 300 revolutions per minute.
In a third aspect, the present invention provides an application of the above composite material in the preparation of polylactic acid with high melt strength, comprising the following steps: respectively weighing 100 parts of PLA, 10-25 parts of composite material and 0.5 part of oxidized PE wax, uniformly mixing, and performing melt blending, extrusion and granulation in a double-screw extruder; the temperatures of the working sections of the twin-screw extruder were set at 175 deg.C, 180 deg.C, 175 deg.C, 165 deg.C, the head temperature was 165 deg.C, and the screw rotation rate was 200 rpm.
Compared with the prior art, the invention has the following beneficial effects:
1. according to the invention, the SEBS/polyester-polyether block copolymer/SEBS-g-MAH composite material is introduced into the existing PLA and is used as a three-dimensional chain entanglement center of a composite material melt to regulate and control the melt chain entanglement degree and further control the melt strength of the composite material, so that the PLA composite material is endowed with good blow molding processability and excellent tensile strength;
the reinforced PLA of the SEBS/polyester-polyether block copolymer/SEBS-g-MAH composite material has the following characteristics: the chain entanglement degree is 3.5-4.1mol/cm 3 The melt strength is 13.6-16.8cN, the tensile strength is 49.5-64.2MPa, and the elongation at break is 25.4-64.5%.
Detailed Description
The present invention will be described in further detail with reference to specific examples.
Example 1
Weighing 10kg of SEBS, 7.5kg of polyester-polyether block copolymer, 5kg of SEBS-g-MAH and 0.5kg of oxidized PE wax, and adding the SEBS-g-MAH and the oxidized PE wax into a mixer for premixing; adding the premix into a double-screw extruder for melt blending, extruding and granulating. The temperatures of the working sections of the twin-screw extruder were set at 180 ℃, 190 ℃, 195 ℃, 190 ℃, 185 ℃, 170 ℃ and the head temperature was 170 ℃. The screw speed was 300 rpm.
Example 2
Weighing 15kg of SEBS, 7.5kg of polyester-polyether block copolymer, 6kg of SEBS-g-MAH and 1.5kg of oxidized PE wax, and adding the materials into a mixer for premixing; adding the premix into a double-screw extruder for melt blending, extruding and granulating. The temperatures of the working sections of the twin-screw extruder were set at 180 ℃, 190 ℃, 195 ℃, 190 ℃, 185 ℃, 170 ℃ and the head temperature was 170 ℃. The screw speed was 300 rpm.
Example 3
Weighing 20kg of SEBS, 10kg of polyester-polyether block copolymer, 8kg of SEBS-g-MAH and 2kg of oxidized PE wax, and adding the materials into a mixer for premixing; adding the premix into a double-screw extruder for melt blending, extruding and granulating. The temperatures of the working sections of the twin-screw extruder were set at 180 ℃, 195 ℃, 200 ℃, 195 ℃, 185 ℃, 170 ℃ and the head temperature was 170 ℃. The screw speed was 300 rpm.
Example 4
Weighing 12.5kg of SEBS, 5kg of polyester-polyether block copolymer, 7kg of SEBS-g-MAH and 1.5kg of oxidized PE wax, and adding the materials into a mixer for premixing; adding the premix into a double-screw extruder for melt blending, extruding and granulating. The temperatures of the working sections of the twin-screw extruder were set at 180 ℃, 190 ℃, 195 ℃, 190 ℃, 185 ℃, 170 ℃ and the head temperature was 170 ℃. The screw speed was 300 rpm.
In the above examples, SEBS having a star-chain structure and a styrene/rubber ratio of 30/70 was used.
In the above examples, the polyester-polyether block copolymer used was a linear chain structure with a polyester/polyether ratio of 38/62.
In the above examples, SEBS-g-MAH was used having a maleic anhydride grafting ratio of 1.5% and a styrene/rubber ratio of 30/70.
In the above examples, the oxidized PE wax used had a molecular weight of 2500 to 3200.
The invention relates to an application of a composite material for enhancing PLA melt strength, which is prepared by weighing 100 parts of PLA, 10-25 parts of the composite material and 0.5 part of oxidized PE wax, uniformly mixing, melting, blending and extruding the materials in a double-screw extruder for granulation; the temperatures of the working sections of the twin-screw extruder were set at 175 ℃, 180 ℃, 175 ℃, 165 ℃, the head temperature at 165 ℃ and the screw speed at 200 rpm.
The storage modulus (G') and loss modulus (G ") of the PLA composites were tested using an AR 1500ex rheometer. From the G ', G' and PLA molecular weights, the platform modulus was calculated
Calculating the chain entanglement molecular weight (M) according to formula (2) e )：
In the formula: rho is density, g/cm 3 (ii) a R is a gas constant, J/(mol. K); t is temperature, K;
Pa。
the melt chain entanglement degree was calculated according to the formula (2).
The melt strength of the composite material is tested by adopting a melt extensional rheometer, the initial speed is 20mm/s, and the acceleration is 2mm/s 2 。
And (3) testing the tensile strength and the elongation at break of the composite material according to GB/T1040.3-2006, wherein the tensile rate is 5mm/min, and each group of samples are subjected to parallel determination for 5 times and an average value is obtained.
The following table shows the performance test results of the composite reinforced PLA of the present invention.
The weight average molecular weight of PLA used in the above examples and comparative examples was 8 ten thousand.
The melt strength of the unreinforced PLA was 5.2cN, the tensile strength was 31.3MPa, and the elongation at break was 22.6%. The composite material for enhancing the PLA melt strength can effectively improve the chain entanglement degree of the PLA melt. Compared with the non-reinforced PLA, the melt strength and the mechanical property of the reinforced PLA are greatly improved, the melt strength is 13.6-16.8cN, the tensile strength is 49.5-64.2MPa, and the elongation at break is 25.4-64.5%.
The above description is only for the purpose of illustrating the embodiments of the present invention, and the scope of the present invention should not be limited thereto, and any modifications, equivalents and improvements made by those skilled in the art within the technical scope of the present invention as disclosed in the present invention should be covered by the scope of the present invention.
Claims (6)
1. The composite material for enhancing the melt strength of the PLA is characterized by being prepared from the following components in parts by weight: 10-20 parts of hydrogenated styrene-butadiene-styrene block copolymer; 5-10 parts of a polyester-polyether block copolymer; 5-8 parts of maleic anhydride grafted hydrogenated styrene-butadiene-styrene block copolymer; 0.5-2 parts of oxidized PE wax; wherein the hydrogenated styrene-butadiene-styrene block copolymer has a star chain structure and a styrene/rubber ratio of 30/70.
2. The composite material for enhancing the melt strength of PLA as claimed in claim 1, wherein the polyester-polyether block copolymer has a linear chain structure and the polyester/polyether ratio is 38/62.
3. The composite material for enhancing the melt strength of PLA is characterized in that the maleic anhydride grafted hydrogenated styrene-butadiene-styrene block copolymer has a linear chain structure, the grafting ratio of maleic anhydride is 1.5%, and the ratio of styrene to rubber is 30/70.
4. A composite material for enhancing PLA melt strength as claimed in claim 1, wherein the oxidized PE wax has a molecular weight of 2500-3200.
5. A method of preparing a composite material for enhancing the melt strength of PLA according to any one of claims 1 to 4, characterized by comprising the steps of:
(1) Weighing hydrogenated styrene-butadiene-styrene block copolymer, polyester-polyether block copolymer, maleic anhydride grafted hydrogenated styrene-butadiene-styrene block copolymer and oxidized PE wax according to the proportion, adding into a mixer, and uniformly mixing to obtain premix;
(2) Adding the premix obtained in the step (1) into a double-screw extruder for melt blending, extruding and granulating; the temperatures of the working sections of the twin-screw extruder were set at 180 ℃, 190 ℃, 195 ℃, 190 ℃, 185 ℃, 170 ℃, the head temperature was 170 ℃ and the screw rotation speed was 300 rpm.
6. Use of a composite material according to any one of claims 1 to 4 for the preparation of a high melt strength polylactic acid, comprising the steps of: respectively weighing 100 parts of PLA, 10-25 parts of composite material and 0.5 part of oxidized PE wax, uniformly mixing, and performing melt blending, extrusion and granulation in a double-screw extruder; the temperatures of the working sections of the twin-screw extruder were set at 175 ℃, 180 ℃, 175 ℃, 165 ℃, the head temperature at 165 ℃ and the screw speed at 200 rpm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211516627.3A CN115926362A (en) | 2022-11-30 | 2022-11-30 | Composite material for enhancing PLA melt strength and preparation method and application thereof |
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| CN202211516627.3A CN115926362A (en) | 2022-11-30 | 2022-11-30 | Composite material for enhancing PLA melt strength and preparation method and application thereof |
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