What is the effect of increasing molecular weight on tensile strength according to the material?

• A. Increases tensile strength
• B. Decreases tensile strength
• C. Has no effect on tensile strength
• D. Causes tensile modulus to increase instead

Answer: (A)

Increasing molecular weight means longer polymer chains that can become more entangled and better able to transfer load between chains. Longer chains resist slippage under stress, and the greater number of entanglements effectively ties the material together, so more stress is required to pull it apart. Additionally, having fewer chain ends per unit mass reduces sites where damage can initiate, further boosting strength. While there are other properties that can also change with molecular weight, the net effect on tensile strength is an increase, especially for polymers where entanglements play a dominant role. The option that predicts a change in modulus rather than strength is not addressing the observed trend in strength, and the other choices contradict the typical behavior of polymers as chain length grows.