Weekly topic: 5 Wealth points for correct answers, 2 Wealth points for participation； Question 104

Amorphous polymers: high degree of orientation, high mechanical strength. Crystalline polymers: high degree of orientation, high mechanical strength, low elongation at break, good toughness

What are the effects of polymer orientation on the properties of the parts? Answer: Uniaxial orientation: In the direction of orientation, the tensile yield strength of the material increases, its modulus increases, while the compressive yield strength decreases. The elongation at break for amorphous polymers increases, whereas that for crystalline polymers decreases ； The performance variation in the non-oriented direction is the opposite of the above. Biaxial orientation: The modulus, tensile strength, and elongation at break of the product increase in the two orientation directions, but the degree of change in properties in the direction with lower degree of orientation is less than that in the other direction.

Amorphous polymers have a high degree of orientation and high mechanical strength. Crystalline polymers have a high degree of orientation, high mechanical strength, low elongation at break, and good toughness. Biaxial orientation (1): The stretching ratios in the two directions are the same, resulting in little anisotropy. (2) The stretching ratios in the two directions are different, resulting in high anisotropy.

Amorphous polymers have a high degree of orientation and high mechanical strength. Crystalline polymers have a high degree of orientation, high mechanical strength, low elongation at break, and good toughness. Biaxial orientation (1): The stretching ratios in the two directions are the same, resulting in little anisotropy. (2) The stretching ratios in the two directions are different, resulting in high anisotropy.

What are the effects of polymer orientation on the properties of the parts? In the unoriented state, the arrangement of macromolecular chains and segments is random, resulting in isotropy; after orientation, since the forces between atoms in the orientation direction are primarily chemical bonds, while in the directions perpendicular to it the forces between atoms are mainly van der Waals forces, anisotropy arises. This results in significant differences in the mechanical, optical, and thermal properties of the material before and after orientation. Mechanical properties: Tensile strength and bending fatigue strength increase in the orientation direction, while decreasing in the direction perpendicular to it; Optical properties: Birefringence occurs; Thermal properties: The Tg increases, and the density and crystallinity of crystalline polymers increase. Orientation degree is an important indicator for characterizing the orientation structure of materials, and it is usually expressed by the orientation function F: F=1/2(3cos2θ-1), where θ is the angle between the orientation direction and the principal axis of the molecular chain. The measurement methods include birefringence and sound speed methods

This post was last edited by Dawn Bellows on 2015-7-3 12:15. What is the impact of polymer orientation on the properties of the manufactured parts? Answer: In uniaxial orientation, the tensile yield strength and modulus of the material increase in the direction of orientation, while the compressive yield strength decreases. The elongation at break for amorphous polymers increases, whereas that for crystalline polymers decreases. The property changes in the direction perpendicular to orientation are the opposite of those described above. The modulus, tensile strength, and elongation at break of the product in the two orientation directions of biaxial orientation will increase.

Answer: 1. Amorphous polymers have a high degree of orientation and high mechanical strength. 2. Crystalline polymers have a high degree of orientation, high mechanical strength, low elongation at break, and good toughness. 3. Biaxial orientation: (1) The stretching ratios in the two directions are the same, resulting in little anisotropy. (2) The stretching ratios in the two directions are different, resulting in high anisotropy.

Answer: Mechanical properties ① Uniaxial orientation: In the direction of orientation, the tensile yield strength and modulus of the material increase, while the compressive yield strength decreases. The elongation at break for amorphous polymers increases, whereas that for crystalline polymers…↓； The performance changes in the non-oriented direction are the opposite of those mentioned above. ② Biaxial orientation: The modulus, tensile strength, and elongation at break of the product increase in the two orientation directions; however, the degree of change in properties in the direction with a lower degree of orientation is less than that in the other direction.

Amorphous polymers have a high degree of orientation and high mechanical strength. Crystalline polymers have a high degree of orientation, high mechanical strength, low elongation at break, and good toughness. Biaxial orientation (1): The stretching ratios in the two directions are the same, resulting in little anisotropy. (2) The stretching ratios in the two directions are different, resulting in high anisotropy.

High orientation and high mechanical strength. It has a high degree of orientation, high mechanical strength, low elongation at break, and good toughness. Amorphous polymers Crystalline polymers Biaxial orientation: (1) The stretching factors in both directions are the same, resulting in little anisotropy. (2) The stretching ratios in the two directions are different, resulting in high anisotropy.