GPPS [General Purpose Polystyrene]

Properties and Characteristics of GPPS

GPPS, also known as Oriented Polystyrene (OPS), is derived from the homopolymerization of styrene. This polymer has a hard, strong, transparent, glossy, and very clear structure. The key features of GPPS include:

High tensile and flexural strength
Excellent dimensional stability and resistance to water and organic chemicals
Colorability and extrusion capability into desired shapes
Suitable for injection molding

GPPS is primarily used in industries such as packaging, optics, pharmaceuticals, and more.

Advantages and Limitations of GPPS

Advantages	Limitations
Low cost	Brittleness at room temperature
High transparency	Weak mechanical properties at temperatures above 70°C
High rigidity	Low chemical resistance to organic solvents
Good dimensional stability	UV sensitivity
Good electrical properties	High flammability
Gamma ray resistance	FDA compliance

Specifications and Characteristics of GPPS

Property	Value
Shrinkage	0.1-0.7%
24-hour Water Absorption	0.01-0.04%
Flammability (UL94)	HB
Tensile Strength at Break	35-60 MPa
Tensile Strength at Yield	35-60 MPa
Elongation at Break	1-4%
Rockwell Hardness M	60-75
Shore Hardness D	85-90
Flexural Modulus	2.5-3.5 GPa
Density	1.04-1.05 g/cm³
Glass Transition Temperature	90°C
Gamma Ray Resistance	Good
UV Resistance	Poor
HDT at 0.46 MPa	75-100°C
HDT at 1.8 MPa	70-90°C
Maximum Service Temperature	65-80°C
Minimum Service Temperature	-20°C

Applications of GPPS

Packaging: GPPS is extensively used in the packaging industry due to its low cost, easy processing, food-contact suitability, recyclability, and high rigidity.
Pharmaceutical and Health Industries: GPPS is used in the production of parts such as Petri dishes, test tubes, pipettes, and emergency instruments due to its low cost, transparency, chemical resistance, and easy processability.
Consumer Goods: GPPS is also used in manufacturing everyday items like cutlery, disposable dishes, shower enclosures, and lamp covers, due to its affordable cost, processability, and recyclability.
Optics: GPPS is applied in the optics industry, particularly for light diffusers, due to its high transparency and ease of processing.

GPPS Forming Process

GPPS can be shaped with all thermoplastic processing techniques. Generally, drying is not required before the forming process, but for very high gloss and clarity, it can be dried at 80°C for 2 hours.

Injection Molding of GPPS: The recommended melt temperature for GPPS is between 180°C and 280°C. The mold temperature should be around 30°C to 50°C, and for thin-wall molds, the temperature can be reduced to 10°C. GPPS mold shrinkage ranges between 0.4% and 0.7%, depending on the GPPS grade.
Extrusion Process for GPPS: GPPS grades with high viscosity (low MFR) are suitable for extrusion. A melt temperature of 180°C to 220°C is commonly used for this process.

GPPS [General Purpose Polystyrene]