Influence of injection molding process on mechanical properties of cellulose diacetate

doi:10.19491/j.issn.1001-9278.2024.10.015

Abstract

Abstract:

Cellulose diacetate plastic （DACP） was injection molded under different process conditions with a change in the injection temperature， injection speed， pressure， and other conditions one by one. The mechanical properties of the injection⁃molded products were investigated. The results indicated that with a change in the injection conditions， the molded products presented a regular change in their performance. The injection temperature exhibited a greater influence on the toughness and elongation at break of the molded products. Their toughness was further enhanced with an increase in the injection temperature， followed by a significant improvement in the elongation at break. However， the molded products started yellowing at a temperature of above 230 ℃. An over high or over low injection speed might lead to deterioration in the impact resistance of the molded products. The products molded at a medium speed of 55 % exhibited the highest impact strength. The change of injection pressure generated little effect on the performance of the molded products； however， an excessive pressure led to some defects such as flashing. The molded products exhibited the optimal overall performance at an injection temperature of 225 ℃， an injection speed of 55 %， and an injection pressure of 9 MPa In this sense， selecting an appropriate injection molding process condition can improve the performance of the injection⁃molded DACP products.

Key words: cellulose acetate, injection molding, mechanical property, molding process, spectacles frame, stress

CLC Number:

TQ320.66

CHENG Ming, WANG Yongkang, HE Jie, WANG Ruyi, XIANG Guanghui. Influence of injection molding process on mechanical properties of cellulose diacetate[J]. China Plastics, 2024, 38(10): 81-86.

Figures/Tables 16

Fig.1. Diagram of type A1 and type B1 splines

试样部位名称和符号	A1型（注塑）	B1型（注塑）
总长度（l₃）/mm	170	—
宽度平行部分之间的距离（l₂）/mm	109.3±3.2	—
窄部平行部分长度（l₁）/mm	80±2	80±2
肩部半径（r）/mm	24±1	—
端部宽度（b₂ ）/mm	20±0.2	—
窄部平行部分宽度（b₁ ）/mm	10.0±0.2	10.0±0.2
厚度（h）/mm	4.0±0.2	4.0±0.2

Tab.1. Dimensions of the A1 and B1 splines

Fig 2. A⁃notch shape

Fig.3. Changes of DACP tensile strength， yield strength and elongation at break at different injection molding temperature

Fig.4. Changes of flexure elastic modulus of DACP and impact strength of normal temperature cantilever beam at different injection temperature

Fig.5. Tensile stress⁃strain curves of DACP at different injection molding temperature

Fig.6. DACP tensile spline fracture morphology during injection molding at 205 ℃ and 245 ℃，respectively

Fig.7. Electron microscope scanning of DACP injection molded stretch spline section at 205 ℃ and 245 ℃，respectively

Fig.8. Permeability comparison of DACP at injection molding temperature of 205 ℃ and 245 ℃，respectively

Fig.9. Surface stress of DACP at different injection molding temperature

Fig.10. Internal stress of DACP at different injection molding temperature

Fig.11. Changes of DACP tensile strength， yield strength and elongation at break at different injection molding speed

Fig.12. Changes of flexural elastic modulus of DACP and impact strength of normal temperature cantilever beam at different injection speed

Fig.13. State of molten material entering the mold cavity at different injection speed

Fig.14. Changes of DACP bending elastic modulus and impact strength of cantilever beam at room temperature under different injection pressure

Fig.15. Changes of DACP tensile strength， yield strength and elongation at break under different injection pressure

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