Transparent CNC-Lignin UV Films via Alkaline Dispersion

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Solution Overview

Problem

Current methods for producing homogeneous and transparent films using cellulose nanocrystals (CNC) and lignin face challenges due to incompatibility between hydrophilic CNC and hydrophobic lignin, requiring expensive organic solvents or lengthy preparation times, and result in opaque or non-biodegradable products.

Innovation Solution

A novel approach using an aqueous alkaline solvent containing sodium hydroxide (NaOH) to disperse CNC and lignin, allowing for the formation of transparent, UV-blocking films without organic solvents, by optimizing NaOH concentration and lignin content to achieve homogeneity and UV-absorption properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If organic solvents are used to disperse CNC and lignin, then homogeneity of the film is improved, but the cost increases and environmental friendliness deteriorates

Engineering Contradiction:

ImprovehomogeneityVSAvoidcost

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent changes the chemical parameters of the solvent system by using aqueous alkaline solutions with specific pH ranges (9-14) and controlled NaOH concentrations (0.1-10 wt%). This parameter change allows lignin to deprotonate and become soluble in water, achieving homogeneity without organic solvents and reducing cost while maintaining environmental friendliness.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If inorganic UV-blocking agents are used, then UV-blocking capability is improved, but transparency deteriorates due to agglomeration

Engineering Contradiction:

ImproveUV-blocking capabilityVSAvoidtransparency

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent uses CNC as an intermediary carrier to disperse lignin particles uniformly throughout the film matrix. The CNC prevents lignin agglomeration by providing a nanoscale dispersion network, thereby maintaining transparency while achieving effective UV-blocking through the lignin's natural UV-absorbing properties.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent creates a composite material system combining CNC, lignin, and aqueous alkaline solution. This composite approach leverages the complementary properties of each component: CNC provides structural integrity and dispersion, lignin provides UV-blocking, and the aqueous alkaline medium enables processing without organic solvents, achieving both transparency and UV-protection.

Inventive Principle:

Principle #40Composite materials

3Reliability

If hydrophilic CNC and hydrophobic lignin are mixed, then UV-blocking capability is improved, but compatibility deteriorates leading to phase separation

Engineering Contradiction:

ImproveUV-blocking capabilityVSAvoidcompatibility

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent changes the pH parameter of the aqueous solution to alkaline conditions (pH 9-14), which causes lignin to deprotonate and develop negative charges. This parameter change transforms lignin from hydrophobic to hydrophilic, enabling compatibility with CNC and preventing phase separation while maintaining UV-blocking capability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The aqueous alkaline solution acts as an intermediary medium that facilitates interaction between hydrophilic CNC and hydrophobic lignin. The alkaline environment modifies lignin's surface properties, enabling it to disperse uniformly among CNC particles and form a stable composite with enhanced UV-blocking properties.

Inventive Principle:

Principle #24Intermediary (Mediator)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The method produces transparent, homogenous CNC/lignin films with enhanced UV-blocking capabilities, stability under UV exposure, and improved thermal stability, while reducing the need for organic solvents and shortening preparation times, making the process more economical and environmentally friendly.

Implementation Method 1

dispersing cellulose nanocrystals and lignin in an aqueous, alkaline solution to yield a dispersion

Methodology Applied

Scientific EffectDispersion: Dispersion (of waves)

Implementation Method 2

evaporating the aqueous, alkaline solution for a time and at a temperature to yield a homogeneous, visibly transparent film

Methodology Applied

Scientific EffectEvaporation: Evaporation

Implementation Method 3

Lignin is a natural UV blocker due to its functional groups, such as phenolic units, ketones, and other chromophores

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Data Source

PatentUS11807727B2Transparent and homogenous cellulose nanocrystal-lignin UV protection films

Publication Date: 2023.11.07 AUBURN UNIVERSITY

AI summary

A visibly transparent, homogeneous UV-blocking cellulose nanocrystal/lignin nanocomposite film and a method of making the same. The film is made by dispersing cellulose nanocrystals and lignin in an aqueous, alkaline solution to yield a dispersion; casting the dispersion onto a substrate; and evaporating the aqueous, alkaline solution to yield a homogeneous, visibly transparent film that at least partially absorbs ultraviolet (UV) radiation.