Plastic Melting Temperature and Injection Molding Temperature Chart

ABS (full name: acrylonitrile-butadiene-styrene)

Baking: ABS is hygroscopic and needs to be dried before processing.
ABS Drying temperature: 80 – 90 C (176 – 195 F)
ABS Drying time: minimum 2 hours. Material moisture content should be less than 0.1%
ABS Melt temperature: 200 – 280 C (392 – 536 F); Target: 230°C (446°F)
ABS Mold temperature: 25 – 80 degrees Celsius (77 – 176 degrees Fahrenheit). (Mold temperature controls gloss; lower mold temperatures produce lower gloss)
ABS Injection pressure: 50 – 100 MPa
ABS Injection speed: medium – high

Chemical and physical properties
ABS is made from a combination of three monomers: acrylonitrile, butadiene, and styrene. Each monomer imparts different properties: acrylonitrile for hardness, chemical resistance and heat resistance; styrene for processability, gloss and strength; butadiene for toughness and impact resistance. Morphologically speaking, ABS is an amorphous material.

The polymerization of three monomers produces a terpolymer with two phases: a continuous phase of styrene-acrylonitrile (SAN) and a dispersed phase of polybutadiene rubber. The performance of ABS is affected by the monomer ratio and the two-phase molecular structure. This allows for great flexibility in product design, so there are hundreds of grades available on the market. Commercially available grades have different properties, such as medium to high impact, low to high surface gloss, and high thermal distortion.

ABS offers excellent processability, appearance, low creep and excellent dimensional stability, as well as high impact strength.

ABS Injection Molding Applications
Automotive (dash and interior panels, glove box doors, wheel covers, mirror housings, etc.), refrigerators, small appliance housings and power tool applications (hair dryers, blenders, food processors, lawn mowers, etc.), telephone housings , typewriter casings, typewriter keys, and recreational vehicles such as golf carts and motorboats.

Drying is usually not required if stored properly
Melt temperature: 220 – 280 C (428 – 536 F); not to exceed 280°C
Mold temperature: 20 – 80 C (68 – 176 F); Recommended: 50 C (122 F) Crystallinity level is determined by mold temperature.
Injection pressure: up to 180 MPa
Injection speed: Generally, fast injection speed is used to minimize internal stress; if surface defects occur, slow molding at higher temperatures is preferred.

Runners and gates
For cold runners, typical diameter range is 4 – 7 mm. It is recommended to use full round gates and runners. All door types can be used. Typical pin gate diameters range from 1 – 1.5 mm, but diameters as small as 0.7 mm can also be used. If edge gates are used, the minimum gate depth should be half the wall thickness and the width should be at least twice the wall thickness. Hot runners can be easily used for PP molding.

Chemical and physical properties
PP is produced by polymerizing propylene using a stereospecific catalyst. Mainly produces isotactic polypropylene (the methyl group is on one side of the carbon chain). This linear plastic is semi-crystalline due to its ordered molecular structure. It is harder than PE and has a higher melting point. PP homopolymer becomes very brittle at temperatures above 0 C (32 F), so many commercial grades are random copolymers containing 1 – 4% ethylene or block copolymers with higher ethylene content. Copolymers have a lower heat deflection temperature (approximately 100 C / 212 F), poor transparency, gloss, and stiffness, but high impact strength. As the proportion of ethylene increases, the material becomes tougher. The Vicat softening point is approximately 150 C (302 F). Due to the high degree of crystallinity, these materials have higher surface hardness and scratch resistance.

PP does not have environmental stress cracking problems. PP is often modified by adding glass fibers, mineral fillers or thermoplastic rubbers. The MFR range of PP is 1 to 40; materials with lower MFR have better impact strength, but lower tensile strength. Copolymers of the same MFR are tougher than homopolymers. Its viscosity is more sensitive to shear and temperature than PE.

Due to the crystallinity, the shrinkage is relatively high (0.018 – 0.025 mm/mm or 1.8 – 2.5%). Shrinkage is more uniform than PE-HD (difference in flow and cross-flow shrinkage is typically less than 0.2%). Adding 30% glass reduces shrinkage to approximately 0.7%.

Both homopolymer and copolymer PP have excellent moisture resistance and good chemical resistance to acids, bases and solvents. But it is not resistant to aromatic hydrocarbons such as benzene and chlorinated hydrocarbons such as carbon tetrachloride. Its antioxidant capacity at high temperatures is not as good as PE.

Main Injection Molding Applications:
Automotive (mainly using mineral-filled PP: dashboard components, ductwork, fans and some under-hood components), appliances (door linings for dishwashers, ductwork for dryers, racks and lids for washing machines, refrigerator liners etc.), consumer products (lawn/garden furniture, lawn mower components, sprinklers, etc.).

Drying is usually not required if stored properly.
HDPE plastic melting temperature range: 180 – 280 C (356 – 536 F); For high molecular weight grades, recommended HDPE melt temperature range: 200 – 250 C (392 – 482 F)
HDPE injection mold temperature range: 20 – 95 C (68 – 194 F)
(Temperatures are higher for wall thicknesses up to 6 mm; temperatures are lower for wall thicknesses greater than 6 mm.) The cooling rate should be uniform to minimize shrinkage changes. For optimal cycle times, the cooling channel diameter should be at least 8 mm and must be within 1.3 d of the mold surface (where “d” is the diameter of the cooling channel).
HDPE material injection pressure range: 70 – 105 MPa
Injection Speed: High injection speeds are recommended; for parts with large surface areas, contour injection speeds can be used to reduce warpage.

HDPE injeciton mold runners and gates designs
The diameter of the flow channels ranges from 4 – 7.5 mm (usually 6 mm). The length of the runner should be as short as possible. All door types can be used. Gate pad length should not exceed 0.75mm. Ideal for hot runner molds; when color changes frequently, insulated hot tip runners are preferred.

HDPE Chemical and physical properties
High-density polyethylene is produced by polymerization of ethylene (using lower temperature and pressure conditions compared to the production of low-density polyethylene). The material is not branched, which is achieved through the use of stereospecific catalysts. HDPE has a higher degree of crystallinity (compared to LDPE) due to molecular regularity.

Higher levels of crystallinity contribute to increased density, tensile strength, heat deflection temperature, viscosity, and chemical resistance. high-density polyethylene is more resistant to penetration than LDPE. Impact strength is low. The properties of HDPE are controlled by density and molecular weight distribution. Injection molding grades typically have narrower molecular weight distributions.

Class 1 materials have a density range of 0.91 – 0.925 g/cm^3;
Class 2 materials have a density range of 0.926 – 0.94 g/cm^3;
Class 3 materials have a density range of 0.94 – 0.965 g/cm^3;

The material flows easily and has an MFR range of 0.1 – 28. Higher molecular weights (lower MFR grades) provide better impact resistance.

As a semi-crystalline material, molding shrinkage is high (0.015 – 0.04 mm/mm or 1.5 – 4%). This depends on the degree of orientation and crystallinity of the part (which in turn depends on processing conditions and part design).

PE is susceptible to environmental stress cracking, which can be minimized through proper design and the use of minimum MFR materials at specific density levels to reduce internal stresses. HDPE is soluble in hydrocarbons at temperatures above 60°C but is more resistant to these materials than LDPE.

HDPE Common applications
High-density polyethylene HDPE is widely used for molding the containers in refrigeration equipment, storage containers, household items (kitchenware), sealing caps, PET bottle bases, etc. HDPE is mostly used in blow molding applications (packaging applications) like jerry can, laundry detergent bottles, body lotion containers, motor oil containers, Flip-top caps and most of caps not for food packing, Plastic crates, paint buckets,etc.

PET ( Full name: polyethylene terephthalate)

Injection molding processing conditions

Drying: Drying is required before molding. PET is very sensitive to hydrolysis. Recommended drying conditions are 120 – 165 C (248 – 329 F) for 4 hours. Moisture content should be less than 0.02%.

PET Melt temperature of unfilled grades: 265 – 280 C (509 – 536 F)

Glass reinforcement grade PET melting point: 275 – 290 C (527 – 554 F)

PET Mold temperature: 80 – 120 C (176 – 248 F); preferred range: 100 – 110 C (212 – 230 F)

Material injection pressure: 30 -130 MPa

Injection speed: high speed, will not cause embrittlement

PET injection molding mold runners and gates
All conventional door types can be used; gates should be 50 – 100% of the part thickness.

Chemical and physical properties
PET is an aromatic polyester polymerized from terephthalic acid (TPA) or dimethyl terephthalate (DMT) and ethylene glycol (EG). The glass transition temperature is approximately 165°C (330°F) and the material crystallizes in the temperature range 120 – 220°C (248 -428°F).

PET is highly sensitive to moisture at high temperatures and can exhibit excessive warping when reinforced with fiberglass. Crystallinity is promoted by adding nucleating agents and crystal growth accelerators. Crystalline molded articles exhibit high modulus, gloss and heat distortion temperature. Warpage can be minimized by adding particulate fillers such as mica. When low mold temperatures are used, transparent molded products

PET injection molding applications
Polyethylene terephthalate PET is diverse used in packing industry. The most seen PET injection molded products are water bottles, Cocacola bottle, Pepsi bottles, grreen tea bottles, orange juice bottles, tomato juice bottles, edible oil bottles, comestic bottles, refrigerater containers, food container jars, 3 & 5 gallon buckets, etc. Most of PET containers are made by two steps which firstly used granual raw material to produce PET preforms by injection molding machine, and then the blow to bottles and containers by stretch blow molding machines.