Dalian extrusion molding, as one of the commonly used methods in plastic processing, is widely used in the production of products such as pipes, sheets, films, and profiles. Material selection is a crucial step in the extrusion molding process, directly affecting product quality, production efficiency, and production costs.

2、 Material performance factors

1. Melt flow performance

The melt flow index (MFI) is an important indicator for measuring the extrusion performance of materials. Excessive MFI may result in insufficient product strength, while insufficient MFI may increase extrusion difficulty. The ideal extruded material should have a moderate MFI value, typically within the range of 0.1-50g/10min. Different products have different MFI requirements, for example, film production usually requires a higher MFI (1-10), while thick walled pipes require a lower MFI (0.1-1).

2. Thermal stability

During the extrusion process, the material needs to undergo high-temperature shear, so thermal stability is crucial. The material should remain stable at the processing temperature without significant degradation. Special attention should be paid to the selection of stabilizers and the control of processing temperature for heat sensitive materials such as PVC.

3. Mechanical properties

According to the intended use of the final product, mechanical properties such as tensile strength, impact strength, and bending modulus of the material need to be considered. PE pipes require good long-term static hydraulic strength, while PP sheets require high rigidity and surface hardness.

4. Thermal performance

The thermal deformation temperature and Vicat softening point of the material determine the temperature range of the product's use. Engineering plastics such as ABS, PC, etc. have high heat resistance and are suitable for high-temperature applications.

3、 Process adaptability factors

1. Processing temperature range

Different materials have different processing temperature ranges. A narrow temperature window will increase the difficulty of process control. For example, the processing temperature range of LDPE is wide (150-300 ℃), while the processing temperature range of PVC is narrow (160-190 ℃).

2. Melt strength

During the extrusion process, the melt needs to maintain sufficient strength to prevent sagging or cracking. HDPE has high melt strength and is suitable for extruding large hollow products; LLDPE has lower melt strength and is more suitable for film production.

3. Shrinkage rate

The shrinkage rate during the cooling process of materials affects the dimensional accuracy of products. Crystalline materials (such as PP and PE) have a larger shrinkage rate (1.5-3%), while amorphous materials (such as PS and PC) have a smaller shrinkage rate (0.4-0.7%).

4. Adhesive properties

The adhesion between materials and molds affects the surface quality of products and the difficulty of demolding. Some materials, such as TPU, are prone to sticking to molds and require the use of release agents or special mold surface treatments.

4、 Economic factors

1. Raw material costs

The price of materials directly affects the cost of products. General plastics such as PP and PE have lower prices, while engineering plastics such as PC and POM have higher prices. A balance needs to be struck between performance and cost.

2. Processing energy consumption

Different materials require different processing temperatures and shear forces, resulting in differences in energy consumption. Processing PVC requires higher energy consumption than PE.

3. Waste recycling rate

The recyclability affects the overall cost of materials. Thermoplastic materials are usually recyclable, while thermosetting materials are difficult to recycle.

4. Production efficiency

The extrusion speed allowed by the material affects production efficiency. HDPE allows for higher extrusion speeds, while PVC has relatively lower extrusion speeds.

5、 Product requirement factors

1. Operating environment

Outdoor products need to consider weather resistance, food contact products need to comply with food safety standards, and electronic and electrical products need to have flame retardancy.

2. Appearance requirements

High gloss products should be made of materials with good fluidity and uniform shrinkage; Transparent products should be made of amorphous or low crystallinity materials such as PS, PC, PMMA.

3. Functional requirements

Special functions such as anti-static, conductive, and antibacterial require the selection of corresponding modified materials or the addition of special additives.

4. Regulatory compliance

Different industries and application areas have specific material standards and requirements, such as drinking water pipes that must comply with GB/T 17219 and medical materials that must comply with ISO 10993.

6、 Environmental factors

1. Sustainability

Biobased materials (such as PLA) and biodegradable materials (such as PBAT) are increasingly being valued, in line with environmental trends.

2. Carbon footprint

The energy consumption and emissions during the material production process have gradually become factors to consider when choosing.

3. Convenience of Recycling

Materials that are easy to sort and recycle are more in line with the requirements of a circular economy.

The selection of extrusion molding materials is a multi factor comprehensive decision-making process that requires balancing material properties, process adaptability, economy, product requirements, and environmental factors. The ideal choice should meet the performance requirements of the product, while also having good processability, reasonable cost, and environmental friendliness. With the development of materials science and advances in processing technology, new high-performance, multifunctional, and environmentally friendly extrusion materials continue to emerge, opening up broader space for extrusion molding applications.