Which one of the following statements is not ture ?

Options

A. In vulcanisation, different chains make rubber harder and stronger
B. Natural rubber has the trans-configuration at every double bond
C. Buna-S is a copolymer of butadiene and siyrene
D. Natural rubber is a 1,4-polymer of isoprene

Explanation

To determine which of the following statements is not true, we will analyze each statement one by one.

1. **Statement A**: "In vulcanization, different chains make the rubber harder and stronger."
- **Analysis**: This statement is true. Vulcanization is a chemical process that involves the addition of sulfur to rubber, which creates cross-links between the polymer chains. This process enhances the strength and elasticity of rubber, making it more durable.

2. **Statement B**: "Natural rubber has trans configuration at every double bond."
- **Analysis**: This statement is false. Natural rubber is primarily composed of polyisoprene, which has a cis configuration at the double bonds. Therefore, this statement is not true.

3. **Statement C**: "Buna S is a copolymer of butadiene and styrene."
- **Analysis**: This statement is true. Buna S is indeed a copolymer formed from the polymerization of butadiene and styrene, which is used in various applications including tires and other rubber products.

4. **Statement D**: "Natural rubber is a 1,4 polymer of isoprene."
- **Analysis**: This statement is true. Natural rubber is formed from the polymerization of isoprene (2-methyl-1,3-butadiene) in a 1,4 addition manner.

Based on the analysis, the statement that is not true is **Statement B**.

### Final Answer:
The statement that is not true is: **"Natural rubber has trans configuration at every double bond."**