Production and Application of Corn-starch Biodegradable Material with PLA-based

Production and Application of Corn-starch Biodegradable Material with PLA-based

What is PLA material?

PLA material

Polylactic acid (PLA) is a polyester polymer obtained by polymerization with lactic acid as the main raw material, which is usually made from starch extracted from renewable plant resources (such as corn, cassava, etc.).

PLA materials are widely used in the field of 3D printing due to their environmental protection characteristics and easy handling advantages. Its raw materials are derived from renewable resources, which not only reduces the dependence on traditional petrochemical resources, but also exhibits a low carbon footprint in the production process. PLA has good air permeability and transparency, and can be processed in a variety of ways, including extrusion, spinning, injection blow molding, etc. This material is highly biocompatible, non-toxic to the human body, and can even be absorbed by the human body, so it also has a wide range of application prospects in the medical field.

In addition, although the heat resistance and mechanical properties of PLA are not as good as those of some engineering plastics, its tensile strength and flexural modulus are sufficient to meet the needs of daily use. For example, PLA has gradually replaced traditional plastics in food containers, packaging materials, and some consumer durables. PLA also has good degradability, and it is decomposed by microorganisms in the soil to produce carbon dioxide and water, which will not cause long-term pollution to the environment.

Overall, PLA is considered an ideal sustainable material choice due to its eco-friendly, biodegradable, and multi-purpose properties. In the future, with the advancement of science and technology and the improvement of environmental awareness, the application scope of PLA is expected to be further expanded.

PLA granules, also known as polylactic acid granules, are the basic raw materials for the manufacture of polylactic acid (PLA) products.

The manufacture of PLA granules involves several important steps that ensure that the final product has excellent biodegradability and mechanical properties. Every step of the manufacturing process, from the selection of raw materials to the final polymerization, is crucial. The manufacturing method of PLA granules is described in detail below:

1. Ingredients

  • Raw material acquisition: The manufacture of PLA begins with the selection of plant resources such as corn starch and cassava, which are crushed and starch extracted.
  • Saccharification process: The extracted starch is converted into glucose by saccharification, which is achieved by mixing and heating enzymes and other chemicals.

2. Ferment

  • Lactic acid fermentation: Next, glucose is converted into lactic acid using a microbial fermentation process. In this process, glucose is fermented to produce high-purity lactic acid.

3. Synthesis of PLA

  • Direct polycondensation method: In the presence of dehydrating agent, lactic acid molecules are directly condensed and polymerized into oligomers by thermal dehydration, and then chain extenders are added to generate high molecular weight PLA.
  • Two-step method: lactic acid is first converted to cyclic dimeric lactide, and then polymerized by ring opening to form PLA. This method allows the production of PLA with a high molecular weight and a narrow molecular weight distribution.

4. Refinement

  • Purification and adjustment: PLA is purified and finely tuned through different polymerization processes and conditions to obtain polymers with different crystallinity and molecular weights. This allows the properties of the PLA material to be adapted to the needs of different applications.

In summary, the manufacturing process of PLA granules not only considers environmental friendliness and sustainability, but also ensures that the final product has good mechanical properties and ease of processing. This granular raw material can be made into a variety of industrial and consumer products through subsequent melting, extrusion, or other processing processes, making it widely used in a variety of fields.

What are the physical modification granulations of PLA?

There are many methods for physical modification and granulation of PLA, mainly including filling modification, blending modification, morphological and structural modification, etc.

PLA modification and granulation extrusion machine

As an environmentally friendly biodegradable material, PLA is used to replace traditional plastics in the field of packaging applications in real life, in order to reduce costs and increase market competitiveness, the most modified applications are filled modification and blending modification, the following focuses on filling modification and blending modification methods and their specific applications:

1. Fill modification

  • Addition of small inorganic or organic molecules: Enhancement of certain properties by adding small molecule inorganic or organic substances to the polymer. This method is simple and inexpensive, and is widely used to enhance the strength, toughness and flame retardancy of materials.
  • Addition of polymers: This method, also known as blending, modifies the properties of the original resin by incorporating one or more other resins, including plastics and rubbers, into one resin. Compounding can significantly improve the compatibility and processability of materials.

2. Blending modification

  • Plasticizer blending: PLA is a rigid material, and the addition of plasticizers such as triacetrate, tributyl citrate, polyethylene glycol (PEG), etc., can improve its flexibility and impact resistance. Studies have shown that citrate plasticizers can effectively reduce the glass transition temperature and improve the brittleness of PLA.
  • Nucleating agent blending: The addition of nucleating agent to PLA can speed up crystallization and improve its thermal and mechanical properties. For example, potassium besylate and surface-modified cellulose nanocrystals can improve the crystallinity and antimicrobial properties of PLA.
  • Inorganic filler blending: Layered silicates such as kaolin and montmorillonite are blended with PLA to prepare composite materials with high mechanical properties and thermal stability. For example, calcium carbonate and hydroxyapatite-modified PLA exhibit higher tensile strength and good biocompatibility.
  • Natural fiber blending: PLA is blended with natural fibers such as banana fiber and coconut palm fiber, which can not only improve its mechanical properties, but also increase its degradation properties. This composite material has excellent performance in terms of thermal stability and tensile modulus.
  • Blending with corn starch: PLA and starch (tapioca flour, yam flour, etc.) blending modification, combined with other compatibilizers and toughening agents, can improve its mechanical properties, tensile strength, increase its degradation properties, and shorten the degradation time. At the same time, it also reduces the cost of raw materials.

PLA’s physical modification granulation covers a variety of technologies, each optimized for different application needs. These modification methods not only improve the comprehensive properties of the material, but also reduce the production cost and expand the application range. When choosing the right modification method, it is necessary to consider factors such as the end use of the material, the cost, and the environmental impact.

Introduction to the production process of PLA granules:

The PLA pellet production process uses a twin-screw extruder with an air-cooled conveyor belt to pelletize, and the following is an analysis of the detailed steps:

1. Pretreatment of raw materials

  • Stirring and heating: first add starch, additives, etc. to the mixer, stir and heat, so that the material is fully mixed evenly, and finally add PLA and PBAT, continue to stir, the temperature is about 100°, the purpose of this step is: to change the surface compatibility of the filler, so that the material is easier to disperse and mix in the later equipment.
Pretreatment of raw materials

2. Compounding and extrusion

  • Twin screw extruder extrusion: The mixed materials are added to the twin screw extruder together, and the excellent mixing performance of the twin screw extruder is used, and the materials are completely melted and distributed mixed in the heating of the external heater. The material is extruded into a noodle-like substance through the die. The advantage of a twin-screw extruder is that it mixes, plasticizes and extrudes materials continuously and efficiently

3. Cooling and pelletizing

  • Air-cooled conveyor belt cooling: The extruded PLA noodles are cooled by passing them through an air-cooled conveyor belt. This method can quickly reduce the temperature of the particles, prevent adhesion between the particles, and ensure the dispersion and quality of the particles.
  • Pelletizing, the cooled noodles enter the pelletizer, and the noodles will be cut into 3XD3mm size particles by a high-speed rotating cutter

4. Sieving

  • Screening of particles that meet the standards: Finally, the processed particles are screened, and the granules that meet the standards and need to be further processed into plastic products are sorted and selected.

Application areas of PLA biodegradable granules:

PLA particles, i.e., polylactic acid particles, are bio-based degradable plastics obtained by polymerization with lactic acid as the main raw material. Due to its environmental protection characteristics and excellent physical properties, PAL particles are widely used in many fields. The following are the main application areas of PAL particles:

1. Medical field

  • Drug controlled release system: PLA has good biocompatibility and biodegradability, and the application in drug carriers can effectively achieve controlled drug release, reduce the number of drug administrations and improve the efficacy.
  • Orthopedic internal fixation materials: PLA materials can be used to produce screws, nails, rods and other orthopedic internal fixation materials, which can be gradually degraded in vivo, avoiding the problem that traditional metal internal fixation materials need to be removed by secondary surgery.

2. Packaging industry

  • Food packaging: Food packaging materials made of PLA granules, such as plastic bags, films, containers, etc., have good transparency and mechanical properties, and at the same time become an effective solution for white pollution because of their degradability.
  • Non-food packaging: PLA is also used in non-food packaging such as electronics and cosmetics, providing sustainable and environmentally friendly options to reduce environmental impact.

3. Textile industry

  • Apparel fibers: PLA pellets are processed into fibers that are used in the production of various apparel and textiles. This fiber is breathable and comfortable, while being biodegradable, reducing the environmental footprint of the apparel industry.
  • Home textiles: For example, bed sheets, curtains and other home textiles have also begun to use PLA materials, which not only meet the needs of use but also reduce environmental pollution.

4. Agriculture

  • Agricultural mulch film: The agricultural mulch film made of PLA particles not only has the heating and water retention function of traditional plastic mulch film, but also can be naturally degraded in the soil after use, avoiding the long-term pollution of the soil by plastic film fragments.
  • Nursery bowls and containers: PLA is also used to make seedling bowls and other planting containers, which can be directly degraded after use, reducing the cost and difficulty of disposing of waste containers.

5. Tableware industry

  • Disposable tableware: Disposable tableware made of PLA granules, such as bowls, plates, chopsticks, etc., is gradually replacing traditional plastic tableware with its environmental protection and degradable characteristics, especially in the takeaway and food packaging industries.

6. 3D the field of printing

  • 3D printing materials: PLA particles have become one of the most commonly used materials for 3D printing due to their good thermoplasticity and interlayer adhesion. Users can print a wide range of complex shapes and structures on demand for prototyping, teaching, and small-scale manufacturing.

7. Electronics industry

  • Plastic parts of electronic devices: PLA particles are used to manufacture plastic parts of some electronic devices due to their good insulation properties and degradability, so as to reduce environmental pollution while ensuring performance.

Due to its excellent environmental protection characteristics and physical properties, PLA particles have been widely used in many fields such as medical, packaging, textile, agriculture, tableware, 3D printing and electronics. With the enhancement of global environmental awareness and the advancement of technology, the application prospect of PLA particles will be broader. In practical applications, the appropriate modification or compounding method can be selected according to the specific needs to optimize the material properties to meet the specific requirements of different fields.

Is PLA safe?

As an emerging biodegradable material, the safety of polylactic acid (PLA) has become the focus of attention.

1. Biocompatible

  • Biomedical applications: PLA has proven its excellent biocompatibility in a wide range of biomedical applications, such as the production of disposable infusion appliances and non-dismantling surgical sutures.
  • Biodegradability: PLA can be completely degraded by microorganisms in nature after use, and finally generate carbon dioxide and water, which does not pollute the environment, which is very beneficial to the protection of the environment and is recognized as an environmentally friendly material.

2. Physical and chemical properties

  • Stability: PLA has good thermal stability, wide processing temperature range (170~230°C), and good solvent resistance.
  • Mechanical properties: PLA has good mechanical properties, such as tensile strength, elongation at break and impact strength, making it suitable for a variety of processing methods.

3. Safety during processing and use

  • Processing safety: PLA can be processed by extrusion, spinning, biaxial stretching, injection blow molding and other methods, and it is non-toxic and harmless during processing.
  • Safety of use: PLA products will not release harmful substances during use, such as food packaging, fast food lunch boxes, etc., and are harmless to the human body.

4. Environmental impact

  • Degradability: PLA can be completely degraded in the natural environment, avoiding the environmental pollution caused by traditional plastics.
  • Carbon footprint: Compared to petroleum-based plastics, PLA, as a bio-based plastic, has a lower carbon footprint during production and use, helping to reduce greenhouse gas emissions.

5. Flame retardant and smoke toxicity

  • Flame retardant: PLA has a certain degree of flame retardancy, which can slow down the spread of fire to a certain extent.
  • Flue gas toxicity: The flue gas produced during PLA combustion has relatively low toxicity and is less harmful to the human body.

6. Safety in skin contact and long-term use

  • Skin-to-skin contact safety: PLA products will not cause irritation or allergic reactions even if they are in direct contact with the skin.
  • Long-term use safety: PLA products have stable performance during long-term use and will not release harmful substances due to aging.

In summary, the safety of PLA has been widely recognized, and it has shown good safety in terms of biocompatibility, physical and chemical properties, processing and use, environmental impact, flame retardancy and flue gas toxicity. At the same time, PLA has broad application prospects, not only in the biomedical field, but also in daily life packaging, textile and other industries also show great potential. With the advancement of technology and the expansion of production capacity, PLA is expected to become an important force to replace traditional plastics, contributing to the realization of sustainable development and environmental protection.

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