Mastering Blow Molded Product Design: From R Transitions to Material Selection

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Introduction to Design
Blow-molded products are widely used in various industries, especially in the beverage and drug packaging industry, and also in the toy industry.


Make R transition at edges and corners
Generally, the corners and corners of blow molded products should be made into R transition, because the larger blowing expansion ratio at sharp corners is easy to cause uneven wall thickness, and the sharp corners are also easy to produce pressure cracking, and the R transition of products can make the wall thickness of products uniform.

Increase structural design in compression, tension and torsion
With different product requirements, some structural design in compression, tension and torsion can also be added:

1. If you want to increase the longitudinal resistance of the product, you can design some stiffeners along the stress direction.
2. In order to improve the anti-collapse performance of the products, the surface can also be designed into an arc structure that is conducive to stress and supplemented with reinforcing ribs. The shoulder of the bottle products should be inclined, not flat and straight.

Generally, the bottle bottom is made into a concave shape to increase strength and placement stability. For example, we usually see bottles containing edible oil with some concave-convex shapes on the surface, which can not only increase the strength of the bottle body, but also facilitate the labeling of trademarks.

Requirements and introduction of blow molding materials
The development and application of blow molding technology is so extensive, which is complementary to the development of blow molding materials. Blow molding materials have gradually developed from the original LDPE, PET, PP and PVC products to blow molding engineering plastics, rubber and some composite materials.

Special requirements for rubber materials in various aspects of plastic blowing
1. Extrusion blow molding
Extrusion blow molding is carried out in a viscous flow state, so in order to reduce parison sag and optimize the wall thickness distribution, plastic with large molecular weight is usually used.

2. Injection blow molding
Injection blow molding is carried out in a high elastic state. In order to reduce the energy consumption of injection molding parison, some plastic that is easy to flow (plastic with small molecular weight) is used.

3. Injection stretch blow molding
Amorphous plastic is generally used. Because of the small intermolecular entanglement force of amorphous plastic, it is easier to stretch. Although PET is also crystalline, it is still the most important stretch blow molding material, and the crystallization rate is quite slow. In short, most blow molding grade plastics have medium to high molecular weight distribution.

Type of blow molding material
1. Polyolefins

HDPE, LLDPE, LDPE, PP, EVA are generally used for blow molding industrial products, containers and toy accessories, chemical storage containers, etc.

2. Thermoplastic polyester
PETG and PETP are mainly used for blowing carbonated beverage packaging bottles and wine bottles, which have gradually replaced PVC and are widely used. The disadvantage is that their costs are high, and they are mainly used for injection-drawing blow molding.

3. Engineering plastics (alloy)
ABS, SAN, PS, PA, POM, PMMA, PPO, etc. have been gradually applied in automobile, medicine, household appliances, chemical industry and other industries, especially PC and its blend plastics, which can be used to blow high-grade containers and automotive products (PC/ABS, etc.).

4. Thermoplastic elastomer
Generally, SBS, SEBS, TPU, TPE and other blow molding compounds are used, while thermosetting plastics, vulcanized rubber and crosslinked PE cannot be blow molded.


Common materials for injection blow molding

PE, PET, PVC, PP, PC and POM are mainly used for containers and structural parts with high molding accuracy and small volume.

Post time: Mar-22-2023