Plastic Properties and Molding Conditions
A comprehensive guide to understanding the characteristics and processing requirements of various injection molding materials used in manufacturing.
Understanding Injection Molding Materials
Different plastics exhibit unique properties and require specific molding conditions. Even the same type of plastic can vary significantly in characteristics and processing requirements depending on the manufacturer. This variation is crucial for engineers and manufacturers working with injection molding materials to understand, as it directly impacts product quality, production efficiency, and material selection.
The properties of injection molding materials determine their suitability for specific applications. Factors such as density, shrinkage rate, and temperature resistance must be carefully considered when selecting the appropriate plastic for a project. Similarly, understanding the optimal molding conditions ensures that the manufacturing process runs smoothly and produces consistent, high-quality parts.
This guide provides detailed information on commonly used domestic and imported plastics, their key properties, and recommended processing parameters. Whether you're an experienced engineer or new to working with injection molding materials, this resource will help you make informed decisions about material selection and processing.
Common Domestic Injection Molding Materials and Their Properties
The following table presents detailed characteristics of commonly used domestic injection molding materials. These plastics are widely utilized in various industries due to their specific properties and cost-effectiveness. Understanding their unique attributes helps in selecting the right material for your application.
| Plastic Name | Abbreviation | Density (g/cm³) | Shrinkage Rate (%) | Molding Temperature (°C) | Mold Temperature (°C) |
|---|---|---|---|---|---|
| Acrylonitrile-Butadiene-Styrene Copolymer | ABS | 1.01-1.04 | 0.4-0.7 | 210-240 | 40-90 |
| High Impact, High Heat Resistance, Flame Retardant, Reinforced ABS | ABS | 1.05-1.08 | 0.4-0.7 | 220-250 | 40-90 |
| Transparent ABS | ABS | 1.16-1.21 | 0.4-0.8 | 210-240 | 40-90 |
| Acrylonitrile-Acrylate-Styrene Copolymer | AAS | 1.28-1.36 | 0.1-0.2 | 210-240 | 40-90 |
| Heat Resistant AAS | AAS | 1.07 | 0.6-0.8 | 210-240 | 40-90 |
| Polystyrene | PS | 1.08-1.09 | 0.4-0.7 | 210-240 | 50-85 |
| Impact Resistant PS | PS | 1.04-1.1 | 0.1-0.8 | 200 (approx) | 60-80 |
| Acrylonitrile-Styrene Copolymer | AS (SAN) | 1.08 | 0.2-0.6 | 200 (approx) | 60-80 |
| Reinforced AS | AS (SAN) | 1.2-1.33 | 0.2-0.6 | 200 (approx) | 60-80 |
| Butadiene-Styrene Copolymer | BS | 1.075-1.1 | 0.1-0.3 | 200 (approx) | 60-80 |
ABS Plastics
ABS (Acrylonitrile-Butadiene-Styrene) is one of the most versatile injection molding materials, offering a good balance of strength, toughness, and rigidity. Its properties can be modified through additives to enhance impact resistance, heat resistance, and flame retardancy.
ABS is widely used in automotive parts, consumer electronics, and household appliances due to its ease of processing and ability to be colored and finished in various ways.
Polystyrene Variants
Polystyrene and its derivatives are common injection molding materials known for their clarity and processability. General purpose polystyrene offers excellent transparency but limited impact resistance, while high-impact polystyrene incorporates rubber modifiers to improve toughness.
These materials find applications in packaging, disposable utensils, and consumer goods where clarity and cost-effectiveness are important factors.
| Plastic Name | Abbreviation | Density (g/cm³) | Shrinkage Rate (%) | Molding Temperature (°C) | Mold Temperature (°C) |
|---|---|---|---|---|---|
| Low-Density Polyethylene | LDPE | 0.91-0.925 | 1.5-5 | 180-250 | 50-70 |
| Medium-Density Polyethylene | MDPE | 0.926-0.940 | 1.5-5 | 180-250 | 50-70 |
| High-Density Polyethylene | HDPE | 0.941-0.965 | 2-5 | 180-240 | 35-65 |
| Cross-linked Polyethylene | PE | 0.93-0.939 | 2-5 | 180-240 | 35-65 |
| Ethylene-Ethyl Acrylate Copolymer | EEA | 0.93 | 0.15-0.35 | 205-315 | Below 60 |
| Ethylene-Vinyl Acetate Copolymer | EVA | 0.943 | 0.7-1.2 | 120-180 | 24-40 |
| Unmodified Polypropylene | PP | 0.902-0.91 | 1-2.5 | 240-280 | 40-60 |
| Copolymer Polypropylene | PP | 0.89-0.905 | 1-2.5 | 240-280 | 40-60 |
Polyethylene Variants
Polyethylene (PE) is one of the most widely used injection molding materials, available in several density grades. Low-density polyethylene (LDPE) offers flexibility and toughness, while high-density polyethylene (HDPE) provides greater rigidity and chemical resistance.
These materials are valued for their excellent chemical resistance, low moisture absorption, and ease of processing. They find applications in packaging, containers, pipes, and various consumer products.
Polypropylene Applications
Polypropylene (PP) is a versatile member of the polyolefin family of injection molding materials, offering an excellent balance of properties including chemical resistance, fatigue resistance, and high melting point. Its relatively low density makes it ideal for lightweight applications.
Polypropylene is widely used in automotive components, medical devices, food packaging, and household goods. Copolymer grades offer improved impact resistance, particularly at lower temperatures.
Polyamide (Nylon) Injection Molding Materials
Polyamides, commonly known as nylons, are a family of high-performance injection molding materials valued for their excellent mechanical properties, wear resistance, and thermal stability. They are available in various grades, including reinforced and impact-modified versions, to suit different application requirements.
| Plastic Name | Abbreviation | Density (g/cm³) | Shrinkage Rate (%) | Molding Temperature (°C) | Mold Temperature (°C) |
|---|---|---|---|---|---|
| Polyamide 66 | PA66 | 1.13-1.15 | 0.5-1.5 | 240-280 | 40-60 |
| 30% Glass Fiber Reinforced PA66 | PA66G30 | 1.38 | 0.2-0.8 | 240-280 | 40-60 |
| Polyamide 6 | PA6 | 1.12-1.14 | 1-2.5 | 160-220 | 40-60 |
| 30% Glass Fiber Reinforced PA6 | PA6G30 | 1.35-1.42 | 0.8-1.5 | 315-371 | 21-94 |
| PA66/PA6 Blend | PA66/PA6 | 1.08-1.14 | 0.5 | 260-310 | 30-85 |
| PA6/PA12 Blend | PA6/PA12 | 1.06-1.08 | 0.4-0.6 | 260-310 | 30-85 |
| Impact Modified Polyamide | PA | 1.0-1.3 | 0.6-1.5 | 250-305 | 35-80 |
Key Characteristics of Nylon Injection Molding Materials
Nylons are distinguished by several key properties that make them valuable injection molding materials across various industries:
- Excellent mechanical properties: High tensile strength, impact resistance, and fatigue resistance make nylons suitable for load-bearing applications.
- Wear resistance: