Stress and Strain Characteristics of Molds for Different Blow Molding Processes

Plastic molds are tools matched with plastic molding machines in the plastics processing industry, which endow plastic products with complete shapes and precise dimensions. Blow molds are specially used to form hollow plastic containers, such as beverage bottles, daily chemical packaging containers and other hollow products.

Based on process principles, blow molding is mainly divided into extrusion blow molding, injection blow molding, injection stretch blow molding (commonly known as ISB), multi-layer blow molding and sheet blow molding. The corresponding equipment for hollow product blow molding is generally referred to as plastic blow molding machines. Blow molding is only applicable to the production of thermoplastic products. Blow molds feature relatively simple structures and are mostly made of carbon steel.

Molds for different blow molding processes show distinct differences in stress and strain characteristics.

(1) Soft TypeIt is characterized by low modulus, low yield point, moderate elongation after fracture and low cracking strength.

(2) Hard and Brittle TypeIt has a high modulus and extremely low elongation after fracture. It exhibits slight yielding or no yielding at all before cracking.

(3) Hard and High-strength TypeIt features high modulus and high yield point, low elongation after fracture, indistinct yielding and high cracking strength.

(4) Soft and Tough TypeIt has low modulus and low yield point, accompanied by large elongation after fracture and moderately high cracking strength.

(5) Hard and Tough TypeIt is characterized by high modulus, relatively high yield point, large elongation after fracture and high cracking strength.

The area enclosed by the tensile curve and the horizontal coordinate axis represents the work done by the load on the material, which reflects the material's toughness. It serves as an important reference for material selection.

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