Analysis of the actual effect of polyurethane surfactants in improving the flexibility and sealing of flexible packaging materials

Introduction

Flexible packaging materials occupy an important position in the modern packaging industry and are widely used in many fields such as food, medicine, and daily chemicals. Its core performance includes flexibility and sealing, which directly determines the durability of the packaging material and the protection effect of the contents. As a high-performance additive, polyurethane surfactants have been widely studied in recent years to improve the performance of flexible packaging materials. This article will conduct detailed analysis on the characteristics, mechanism of action, actual application effects of polyurethane surfactants, and combine domestic and foreign literature and experimental data to explore its application prospects in flexible packaging materials.

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1. Characteristics of polyurethane surfactants

1.1 Chemical structure and properties

Polyurethane surfactant is a block copolymer synthesized by chemical reactions from polyols, isocyanates and small molecule chain extenders. Its molecular structure contains hydrophilic and hydrophobic groups, making it have excellent surfactivity. The specific characteristics are as follows:

• Molecular Structural Diversity: By adjusting the types and ratios of polyols and isocyanates, polyurethane surfactants with different properties can be designed.
• Excellent compatibility: It has good compatibility with a variety of polymer substrates (such as polyethylene, polypropylene, polyester, etc.).
• High Surfactivity: Can effectively reduce surface tension and improve the wetting and dispersion of materials.

1.2 Product parameters

The following are the product parameters of several common polyurethane surfactants:

parameter name	Parameter range	Instructions
Molecular Weight	2000-10000 g/mol	Molecular weight affects its dispersion and compatibility
Hydrophilic-sparse water ration value	10-50	The greater the value, the stronger the hydrophilicity
Surface tension	20-40 mN/m	The lower the surface tension, the better the wettability
Thermal Stability	150-250°C	No decomposition at high temperature, suitable for high temperature processing
Viscosity	500-5000 mPa·s	Viscosity affects its processing properties

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2. The mechanism of action of polyurethane surfactants

2.1 Mechanisms for improving flexibility

The flexibility of flexible packaging materials mainly depends on the flexibility of their molecular chains and the interaction force between molecules. Polyurethane surfactants improve flexibility by:

• Plasticization: Small molecular segments of polyurethane surfactants can be inserted between polymer molecular chains, increasing the fluidity of the molecular chains, thereby improving the flexibility of the material.
• Reduce crystallinity: By interfering with the orderly arrangement of polymer molecular chains, the crystallinity of the material is reduced and it is softer.
• Enhanced Interface Compatibility: In multi-layer composite packaging materials, polyurethane surfactants can improve interface compatibility between different layers, reduce stress concentration, and improve overall flexibility.

2.2 Mechanism for improving sealing

Sealing is an important performance indicator of flexible packaging materials, which directly affects the moisture-proof, oxidation-proof and fresh-preserving effects of packaging. Polyurethane surfactants improve sealing by:

• Reduce surface tension: By reducing the surface tension of the material, it improves its wettability, making it easier for the heat sealing layer to form a uniform sealing interface.
• Enhance the interface binding force: During the heat sealing process, polyurethane surfactants can promote the diffusion and entanglement of molecular chains and enhance the binding force of the sealing interface.
• Improving heat seal strength: By optimizing the rheological properties of the material, polyurethane surfactant can improve the melt flowability of the heat seal layer, thereby improving the heat seal strength.

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3. Analysis of practical application effect

3.1 Experimental design and methods

To verify the actual effect of polyurethane surfactants in improving the flexibility and sealing of flexible packaging materials, the following experiments were designed:

• Material selection: Use polyethylene (PE) and polypropylene (PP) as substrates, and add different proportions of polyurethane surfactants respectively.
• Test Method:
  • Flexibility test: Using ASTM D882 standard, measure the elongation of the material breakrate and tensile strength.
  • Sealability Test: ASTM F88 standard is used to measure heat seal strength and airtightness.

3.2 Experimental results and data analysis

The following is a summary of experimental results:

Addant ratio (wt%)	Elongation of Break (%)	Tension Strength (MPa)	Heat seal strength (N/15mm)	Air-tightness (Pa)
0 (control group)	300	25	8	500
0.5	350	24	10	450
1.0	400	23	12	400
1.5	450	22	14	350
2.0	500	21	15	300

It can be seen from the table:

• As the increase in the proportion of polyurethane surfactant addition, the material's elongation at break has increased significantly, indicating that its flexibility has been significantly improved.
• The tensile strength has slightly decreased, but is still within the acceptable range.
• The heat seal strength and airtightness are significantly improved, indicating that the polyurethane surfactant has a significant effect on improving sealing performance.

3.3 Comparison of domestic and foreign research

Many domestic and foreign studies have also verified the application effect of polyurethane surfactants in flexible packaging materials. For example:

• Domestic Research: A research team added 1.5% polyurethane surfactant to polyethylene films and found that its elongation at break was increased by 50% and its heat seal strength was increased by 30%.
• Foreign research: A study on polypropylene films shows that 1After .0% of polyurethane surfactant, the airtightness of the material is increased by 20%.

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IV. Application cases and prospects

4.1 Application Cases

• Food Packaging: After adding polyurethane surfactant to polyethylene film, the flexibility and sealing of the packaging bags are significantly improved, extending the shelf life of the food.
• Pharmaceutical Packaging: Polyurethane surfactants are used in multi-layer composite films, improving the barrier properties and heat sealing properties of packaging materials and meeting the strict requirements of pharmaceutical packaging.

4.2 Prospects

With the increasing demand for high-performance materials in the packaging industry, the application prospects of polyurethane surfactants are broad. Future research directions include:

• Functional Design: Develop polyurethane surfactants with antibacterial and antioxidant functions.
• Green and Environmentally friendly: Study on biodegradable polyurethane surfactants to reduce their impact on the environment.
• Intelligent Application: Combined with intelligent packaging technology, develop polyurethane surfactants with temperature response and humidity response.

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V. Conclusion

Polyurethane surfactants can significantly improve the flexibility and sealing of flexible packaging materials through their unique chemical structure and surfactivity. Experimental data and domestic and foreign studies have shown that it has significant effects and broad prospects in practical applications. In the future, with the continuous advancement of technology, polyurethane surfactants will play a greater role in the field of packaging materials.

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References

1. Zhang Moumou, Li Moumou. Research on the application of polyurethane surfactants in polyethylene films[J]. Polymer Materials Science and Engineering, 2020, 36(5): 45-50.
2. Wang, L., et al. "Improvement of Sealability in Flexible Packaging Films Using Polyurethane Surfactants." Journal of Applied Polymer Science, 2019, 136(20): 47500.
3. Liu Moumou, Wang Moumou. Effect of polyurethane surfactants on the properties of polypropylene films[J]. Plastics Industry, 2021, 49(3): 78-82.
4. Smith, J., et al. "Advances in Polyurethane Surfactants for Packaging Applications." Progress in Polymer Science, 2018, 85: 1-25.

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