High-Flow vs Low-Flow Plastics

High-flow vs low-flow plastics are classified based on Melt Flow Rate (MFR) or Melt Volume Rate (MVR), with key differences in processability and applications.

1. Definitions of High-Flow vs Low-Flow Plastics

High-Flow Plastics:

High MFR (e.g., >30 g/10min).
Low melt viscosity, easy flow.

Low-Flow Plastics:

Low MFR (e.g., <10 g/10min).
High melt viscosity, high flow resistance.

2. Material Properties Comparison of High-Flow vs Low-Flow Plastic

Property	High-Flow Plastics	Low-Flow Plastics
Molecular Structure	Short chains, less branching (e.g., LDPE)	Long chains, possible crosslinking (e.g., UHMWPE)
Crystallinity	Low (e.g., atactic PP)	High (e.g., high-crystallinity PA66)
Thermal Stability	Prone to degradation (chain scission)	More stable (heat-resistant, e.g., PPS)
Shrinkage	High (1.5–2.5%)	Low (0.5–1.5%, especially with glass fiber)
Mechanical Strength	Lower tensile/impact strength	High rigidity, wear-resistant (e.g., POM, PEEK)

Processing Techniques of High-Flow vs Low-Flow Plastics

High-Flow Plastics

Injection Parameters:

Low injection pressure (<80 MPa).
Low mold temp. (40–80°C), shorter cooling time.

Common Defects & Solutions:

Flash: Increase clamping force or reduce injection speed.
Sink marks: Optimize packing pressure (limited effect).

High-Flow Plastics

Injection Parameters:

High injection pressure (>100 MPa), may require electric machines.
High mold temp. (100–150°C) to prevent premature solidification.

Common Defects & Solutions:

Short shots: Increase melt temp. or use spiral gates.
Degradation: Strict temp. control (e.g., PEEK <400°C).

Advantages & Disadvantages of High-Flow vs Low-Flow Plastics

Type	Pros	Cons
High-Flow	Easy processing, fast cycles, fine details	Lower strength, warping risk
Low-Flow	High strength, heat resistance, dimensional stability	Difficult processing, expensive equipment

Modification Methods

Improving Flowability

Add lubricants (silicone oil, stearates).
Reduce molecular weight (e.g., peroxide-treated PP).
Blend with low-viscosity resins (e.g., PP+PE).

Reducing Flowability

Add fillers (glass fiber 20–40%, carbon fiber, talc).
Crosslinking (e.g., radiation-crosslinked PE for cables).

Material Examples & Applications of High-Flow vs Low-Flow Plastics

High-Flow Plastics

Material	Example Grade	MFR	Applications
PP	Sabic® 575P	55	Thin-wall containers, syringes
ABS	LG Chem AF-343A	35	Phone cases, LEGO bricks
POM	DuPont™ Delrin® 570	25	Precision gears, zippers

Low-Flow Plastics

Material	Example Grade	MFR	Applications
PC	Covestro Makrolon® 2805	6	Bulletproof glass, car lenses
PEEK	Victrex® 450G	5	Aerospace bearings, implants
PA66+30%GF	BASF Ultramid® A3WG6	3	Engine covers, power tools

By selecting the right material, manufacturers can balance productivity and performance. Modifiers (e.g., flow enhancers or reinforcing agents) further fine-tune flow properties for specific needs.