How Are the Oil, Acid, and Alkali Resistance Functions of Safety Shoes Achieved?​

The oil, acid, and alkali resistance of safety shoes are achieved through ​material selection, structural design, and surface treatment technologies, ensuring effective protection in chemically hazardous environments. Below are the key principles and technologies involved:

 

​1. Oil Resistance​

 

​Material Selection​

​Synthetic Rubber (e.g., Nitrile Rubber/NBR, Hydrogenated Nitrile Rubber/HNBR)​:

Polar molecular groups (e.g., cyanide) repel non-polar oil molecules, preventing dissolution or swelling.

NBR outperforms natural rubber in oil resistance, making it ideal for oil-exposed environments (e.g., automotive repair, machining).

​Thermoplastic Polyurethane (TPU)​:

High-density molecular structure resists oil penetration while maintaining abrasion resistance.

​Structural Design​

​Multi-Layer Sole Construction:

Outer layer uses oil-resistant rubber, while inner layers (e.g., PU) provide cushioning for comfort.

​Seamless Bonding:

Seamless integration between sole and upper prevents oil seepage through gaps.

​Testing Standards​

​EN ISO 20345: Tests sole expansion rate after oil immersion (e.g., engine oil, diesel; ≤12% expansion qualifies).

​ASTM D471: Evaluates material properties (e.g., tensile strength, hardness) after oil exposure.

 

​2. Acid and Alkali Resistance​

 

​Material Selection​

​Chloroprene Rubber (CR)​:

Chlorine atoms enhance resistance to low/medium-concentration acids and alkalis.

​Polyvinyl Chloride (PVC)​:

Low permeability against dilute acids/alkalis but prone to deformation at high temperatures.

​Fluoroelastomer (FKM)​:

Fluoropolymer structure resists strong acids (e.g., sulfuric acid), alkalis, and solvents, though costly.

​Surface Treatments​

​Chemical Coatings (e.g., PTFE)​:

Polytetrafluoroethylene (PTFE) coatings create a barrier against chemical penetration.

​Resin Impregnation:

Fabrics (e.g., canvas) are soaked in acid/alkali-resistant resins for enhanced protection.

​Structural Design​

​Molded One-Piece Sole:

Eliminates seams to prevent chemical ingress.

​Splash Guards:

High ankle collars and extended tongues block liquid splashes.

​Testing Standards​

​EN ISO 20345: Measures mass change (≤10%) after 24-hour immersion in 20% sulfuric acid or sodium hydroxide.

​ISO 6112: Tests chemical penetration resistance.

 

​3. Key Technologies and Innovations​

 

​Composite Materials:

Example: Outer sole (FKM for acid resistance), midsole (TPU for pressure resistance), and inner layer (EVA for cushioning).

​Smart Protective Technologies:

​Microporous Liquid-Repellent Structure: Mimics the "lotus effect" using nanotechnology for hydrophobic/oil-repellent surfaces.

​Self-Healing Coatings: Minor scratches automatically repair to maintain integrity.

​Environment-Specific Designs:

​Temperature Adaptability: Rubber formulations stable in extreme temperatures (-30°C to +150°C).

 

​4. Recommendations for Different Scenarios​

 

​Environment​	​Recommended Materials​	​Protection Focus​
​Oily Surfaces​ (e.g., workshops)	NBR, TPU	Oil resistance, slip resistance
​Low-Concentration Acids/Alkalis​ (e.g., labs)	CR, PVC	Penetration resistance, lightweight
​Strong Acids/Alkalis​ (e.g., chemical plants)	FKM, PTFE coatings	Corrosion resistance, sealing
​Mixed Chemical Exposure​	Multi-layer soles + FKM coatings	Comprehensive protection

 

​5. Maintenance and Precautions​

 

​Regular Cleaning: Use neutral detergents to remove chemical residues and prevent material degradation.

​Avoid High Temperatures: Materials like PVC may deform under heat, reducing performance.

​Inspect Coatings: Replace shoes if coatings are damaged to prevent chemical infiltration.