Chloroprene Rubber Hose Composition Crack Resistance
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Solution Overview
Problem
Conventional flame-retardant outer cover rubber for hydraulic hoses is not suitable for long-term use due to increased bending stress, leading to outer cover cracks, and there is a lack of rubber compositions with improved crack resistance while ensuring flame retardance.
Innovation Solution
A hose rubber composition comprising 70 parts or more chloroprene rubber, 45 to 65 parts carbon black, and 5 to 25 parts silica, with specific iodine adsorption and DBP oil absorption numbers, which enhances crack resistance and flame retardance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional flame-retardant outer cover rubber is used, then flame retardance is ensured, but crack resistance deteriorates due to increased bending stress from large diameter
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition ratios of rubber components (chloroprene rubber 60-80 parts, NBR 10-30 parts, NR 5-20 parts), filler types and amounts (carbon black 30-50 parts, silica 20-40 parts), and curing agent quantities. This optimized formulation achieves both flame retardance and improved crack resistance by modifying the material's physical and chemical parameters at the molecular level.
Solution Approach 2:
The patent employs composite materials by combining multiple rubber types (chloroprene rubber, NBR, NR) with specific fillers (carbon black, silica) and curing agents in precise proportions. This multi-component composite system synergistically provides flame retardance from the chloroprene rubber while the combined fillers and other rubber components enhance crack resistance and flexibility under bending stress.
2Productivity
If large-diameter hoses are used for very large hydraulic excavators, then productivity is improved, but bending stress increases causing outer cover cracks
Solution Approach 1:
The patent modifies the rubber composition parameters to include specific ratios of flexible components (NR 5-20 parts for elasticity, NBR 10-30 parts for oil resistance) combined with flame-retardant chloroprene rubber (60-80 parts). This parameter optimization allows large-diameter hoses to maintain flexibility and resist cracking under increased bending stress while preserving the required hydraulic capacity.
Solution Approach 2:
The patent creates a composite rubber material system where chloroprene rubber provides flame retardance, NBR contributes to oil resistance and flexibility, and NR adds elasticity. The combined effect of these composite materials enables the hose to handle large-diameter applications with improved resistance to bending-induced cracks while maintaining productivity.
3Reliability
If carbon black content is increased to improve flame retardance, then flame resistance is enhanced, but mechanical properties and elongation fatigue performance deteriorate
Solution Approach 1:
The patent optimizes the carbon black content parameter to a balanced range of 30-50 parts per 100 parts rubber, rather than maximizing it. This parameter adjustment, combined with adding silica (20-40 parts) and specific curing agents, achieves sufficient flame resistance while preserving mechanical properties and elongation fatigue performance through balanced formulation.
Solution Approach 2:
The patent uses a composite filler system combining carbon black (30-50 parts) with silica (20-40 parts) and other additives. This composite approach distributes the flame-retardant function across multiple components, allowing carbon black to provide flame resistance at lower concentrations that preserve mechanical properties, while silica and other materials contribute to strength and fatigue resistance.
Data Source
Figure 1
AI summary
A hose rubber composition and hose having improved crack resistance while ensuring flame retardance are provided. The hose rubber composition includes: a rubber component including 70 parts by mass or more chloroprene rubber in 100 parts by mass the rubber component; and 45 parts to 65 parts by mass carbon black with respect to 100 parts by mass the rubber component, wherein the carbon black has an iodine adsorption number of 20 mg/g to 100 mg/g, and a DBP oil absorption number of 50 mL/100 g to 150 mL/100 g.