Property of Plastics

This trial version can use only a part of item.

Property of Plastics

This chapter explains the properties of plastics and the characteristics of typical material in mold processing.

Property of Plastics

Plastic properties are classified by 5 criteria.
The properties mentioned here could be references for plastic selection. However, these properties are subject to change due to temperature or humidity changes. Therefore, it is necessary to account for changes in environmental conditions on selection of plastics.

Mechanical properties

Mechanical properties refer to displacement or breakage of plastic due to some mechanical change such as applying some load.
Mechanical properties are dependent on the temperature, force (load), and the duration of time the load is applied. It may also be affected by ultra-violet radiation when used outside.

Thermal properties

Thermal properties include heat resistance or combustibility.
Thermoplastic has a larger coefficient of thermal expansion or combustibility and a smaller thermal conductivity or specific heat than other material such as metals.

Chemical properties

Chemical resistance, environmental stress crack resistance , or resistance to environmental change are referred as chemical properties.
When a plastic contacts chemicals, there is some kind of change. After having a plastic in contacted with chemicals under no stress for about a week, changes in appearance, weight and size of the plastic are examined. Such changes are referred to as chemical properties.

Electric properties

Electric properties are also referred to as electromagnetic properties. Electric properties include insulation, conductivity and electro-static charges.
Due to their good insulation property, plastics are often used in electric fields. However, plastics do have a defect; they are easily electrified.

Physical properties

Specific gravity, index of refraction and moisture absorption are called physical properties.
The specific gravity of the plastic is small, and it varies depending on the character of high polymer , or thermal and mechanical treatment of the plastic.

Characteristics of Molding Material

Here, characteristics, application, cautions, molding condition and physical properties of typical molding material (thermosetting plastic has only physical properties.) are described.
Molding material often changes into different states due to many factors. General features, applications, caution and molding conditions are presented as follows:

Polyamide (Nylon) (PA)

Characteristics: Excellent in impact resistance and chemical resistance as well as in electric property and low temperature; Higher fusing point, good thermal resistance.; Due to its self-lubricant character, it is often used for bearings of mechanical parts.
Use: Often used for moving parts of machines (bearing, gear, cam) or bolt.
Caution: Because of its water-absorption character, dimension accuracy may be affected and the material quality may change. So, it needs to be dry enough before molding.; Low dissolving (melting) viscosity- watery texture may cause development of flashs.
Molding condition: Resin temperature is generally set high.; Control the mold temperatures for uniform cooling.

PROPERTY-1 (Drying temperature - injection pressure)
Resin	Grade	Fillers	Abbreviation #	Drying temperature []	Drying time [hours]	Cylinder temperature []	Mold temperature []	Injection pressure [kgf/]
Polyamide (Nylon)	Nylon 6	-	PA6	80	8 - 15	220 - 300	20 - 90	800 - 1500
Polyamide (Nylon)	Nylon 6-6	-	PA66	80	8 - 15	250 - 350	20 - 90	1000 - 1500
PROPERTY 2 (Elongation - Specific gravity)
Resin	Grade	Fillers	Abbreviation #	Elongation[%]	Molding shrinkage[%]	Consecutive heat resistance[]	Thermal deflection temp. []	Specific gravity
Polyamide (Nylon)	Nylon 6	-	PA6	25 - 320	0.5 - 1.5	82 - 121	60 - 70	1.12 - 1.14
Polyamide (Nylon)	Nylon 6-6	-	PA66	60 - 320	0.8 - 2.0	82 - 121	66 - 105	1.13 - 1.15
PROPERTY 3 (Tensile strength - impact strength)
Resin	Grade	Fillers	Abbreviation #	Tensile strength [kgf/]	Compressive strength [kgf/]	Bending strength [kgf/]	Impact strength [kgf/]
Polyamide (Nylon)	Nylon 6	-	PA6	490 - 850	914	560 - 1250	1.0 - 20.0
Polyamide (Nylon)	Nylon 6-6	-	PA66	630 - 850	1050	430 - 1200	1.0 - 5.4

Polypropylene (PP)

Polypropylene (PP): Lightest specific gravity among all plastics generally used; Excellent liquidity; Applied for various gates such as pinpoint gate , direct gate , special gate, etc.; No need to dry as it has little water absorption; Molding shrinkage rate changes according to mold temperature
Use: Often used for extra large molding parts or extremely thin parts; Due to its excellent fatigue resistance, it is often used for hinges that are subject to repeated bending
Caution: Due to its large shrinkage rate, it may experience deformation if the cooling of the mold is not sufficient.; Temperature adjustment must be performed for molding that requires precise dimension.; When using the mold that may cause sink marks or holes, injection pressure should be set relatively higher.
Molding condition: Molding temperature is usually 40 - 60; Injection pressure standard is 800 - 1200kgf/; however, the highest pressure free of flash is appropriate.; The temperature range appropriate for molding is 200 - 300, and it is better to set up within the higher range.

PROPERTY-1 (Drying temperature - injection pressure)
Resin	Grade	Fillers	Abbreviation #	Drying temperature []	Drying time [hours]	Cylinder temperature []	Mold temperature []	Injection pressure [kgf/]
Polypropylene (PP)	General	-	PP	-	-	180 - 300	20 - 90	600 - 1410
Polypropylene (PP)	-	Glass fiber 40%	PP	-	-	200 - 300	20 - 90	703 - 1410
PROPERTY 2 (Elongation - Specific gravity)
Resin	Grade	Fillers	Abbreviation #	Elongation[%]	Molding shrinkage[%]	Consecutive heat resistance[]	Thermal deformation temp. []	Specific gravity
Polypropylene (PP)	General	-	PP	100 - 800	1.0 - 2.5	88 - 115	103 - 130	0.90 - 0.91
Polypropylene (PP)	-	Glass fiber 40%	PP	2.0 - 4.0	0.2 - 1.8	121 - 138	110 - 161	1.22 - 1.23
PROPERTY 3 (Tensile strength - impact strength)
Resin	Grade	Fillers	Abbreviation #	Tensile strength [kgf/]	Compressive strength [kgf/]	Bending strength [kgf/]	Impact strength [kgf/]
Polypropylene (PP)	General	-	PP	210 - 400	260 - 562	352 - 492	1.5 - 110
Polypropylene (PP)	-	Glass fiber 40%	PP	560 - 1000	387 - 492	492 - 1000	6 - 11

Polyethylene (PE)

Characteristics: There are two types of polyethylene: low density polyethylene and high-density polyethylene.; Low-density polyethylene is softer than high-density polyethylene. It is excellent for molding.; High-density polyethylene has excellent stiffness and impact resistance.; Excellent chemical resistance; No need to dry because it does not absorb water
Use: Low-density polyethylene is used for products requiring softness and flexibility. It is often used for complex-shaped plastic or packing material.; Low-density polyethylene is also used to improve flow of molding materials.; High-density polyethylene is used for cylindrical containers, or for large plastic products such as containers.
Caution: Higher mold temperature results in the following: molding cycle becomes longer, impact strength is reduced, molding shrinkage becomes higher, and specific gravity increases.; Lower mold temperature causes the surface of the plastic to peel off or deform.
Molding condition: Higher mold temperature will improve brilliance and appearance of the part.; Higher injection pressure will result in uniform temperature of the molten plastic inside the mold. It also enhances the density and strength of the plastic.; It is advised to apply low holding pressure after filling the molten plastic.

PROPERTY-1 (Drying temperature - injection pressure)
Resin	Grade	Fillers	Abbreviation #	Drying temperature []	Drying time [hours]	Cylinder temperature []	Mold temperature []	Injection pressure [kgf/]
Polyethylene (PE)	Low density	-	LDPE	-	-	150 - 270	20 - 60	500 - 2110
	Intermediate density	-	MDPE	-	-	200 - 300	10 - 60	562 - 2110
	High density	-	HDPE	-	-	200 - 300	10 - 80	600 - 1410
PROPERTY 2 (Elongation - Specific gravity)
Resin	Grade	Fillers	Abbreviation #	Elongation[%]	Molding shrinkage[%]	Consecutive heat resistance[]	Thermal deformation temp. []	Specific gravity
Polyethylene (PE)	Low density	-	LDPE	90 - 800	1.5 - 5.0	80 - 100	37.6 - 49.2	0.91 - 0.925
	Intermediate density	-	MDPE	50 - 600	1.5 - 5.0	48.7 - 121	48.7 - 73.7	0.926 - 0.940
	High density	-	HDPE	20 - 130	2.0 - 6.0	78 - 124	59.8 - 88	0.941 - 0.965
PROPERTY 3 (Tensile strength - impact strength)
Resin	Grade	Fillers	Abbreviation #	Tensile strength [kgf/]	Compressive strength [kgf/]	Bending strength [kgf/]	Impact strength [kgf/]
Polyethylene (PE)	Low density	-	LDPE	42 - 161	-	-	hard to break
	Intermediate density	-	MDPE	84 - 246	-	337 - 492	2.7 - 87
	High density	-	HDPE	218 - 387	190 - 253	-	2.7 - 87

Acrylonitrile butadienstylene(ABS)

Characteristics: Elastic and unbreakable; Since it is Non-crystalline plastic , it has poor climate resistance; Easy to maintain dimension accuracy, well-balanced material; Relatively easy to perform secondary processing (mechanical treatment or galvanized treatment, solvent sealing, etc.)
Use: Often used for home electric appliances or interior parts
Caution: Due to its moisture-absorption characteristics, drying is critical before molding. Otherwise, bubbles or cracks may appear on surface.; Thin plastic shapes, where it is hard to fill in the molten plastic, should be avoided.
Molding condition: Maintain the mold temperature relatively high, around 60 - 80 to stabilize the temperature; Set injection pressure high as Acrylonitrile butadienstyrene has poor flow.

PROPERTY-1 (Drying temperature - injection pressure)
Resin	Grade	Fillers	Abbreviation #	Drying temperature []	Drying time [hours]	Cylinder temperature []	Mold temperature []	Injection pressure [kgf/]
Acrylonitrile butadienstylene	High stiffness	-	ABS	70 - 80	2	180 - 260	40 - 80	560 - 1760
	Heat resistance	-	ABS	70 - 80	2	250 - 300	40 - 80	560 - 1760
	-	Glass fiber 20% - 40%	ABS	70 - 80	2	200 - 260	40 - 80	1050 - 2810
PROPERTY 2 (Elongation - Specific gravity)
Resin	Grade	Fillers	Abbreviation #	Elongation[%]	Molding shrinkage[%]	Consecutive heat resistance[]	Thermal deflection temp. []	Specific gravity
Acrylonitrile butadienstylene	High stiffness	-	ABS	3.0 - 20.0	0.2 - 0.9	60 - 93	82 - 108	1.02 - 1.07
	Heat resistance	-	ABS	5.0 - 25.0	0.2 - 0.9	88 - 165	93 - 122	1.05 - 1.08
	-	Glass fiber 20% - 40%	ABS	2.5 - 3.0	0.1 - 0.2	93 - 110	93 - 118	1.22 - 1.36
PROPERTY 3 (Tensile strength - impact strength)
Resin	Grade	Fillers	Abbreviation #	Tensile strength [kgf/]	Compressive strength [kgf/]	Bending strength [kgf/]	Impact strength [kgf/]
Acrylonitrile butadienstylene	High stiffness	-	ABS	400 - 610	127 - 879	773 - 1000	6 - 33.7
	Heat resistance	-	ABS	400 - 560	506 - 702	703 - 1050	10.9 - 35.4
	-	Glass fiber 20% - 40%	ABS	570 - 740	600 - 1550	1120 - 1900	5.4 - 13.1

Polycarbonate (PC)

Characteristics: High melting point, high melting (fusing) viscosity; Relatively small molding shrinkage rate (0.5 - 0.8%), and not affected by the position of the gates; Does not soften below 150; Excellent impact strength
Use: Used for the parts requiring strength or parts subjected to dynamic and severe loads
Caution: This plastic needs drying before molding due to its water absorption characteristics; otherwise, appearance or quality may be affected.; High mold temperature causes longer molding cycle; Low mold temperature may cause deformation of the part; If injection pressure is too high, the part may deform internally and be easily broken.
Molding condition: Mold temperature is appropriate between 85 - 110; Higher temperature will lead to better flow and glossy appearance(brilliance). It also reduces deformation of the product; Injection pressure should be set high; Molding temperature should be between 260 - 300

PROPERTY 1 (Drying temperature - injection pressure)
Resin	Grade	Fillers	Abbreviation #	Drying temperature []	Drying time [hours]	Cylinder temperature []	Mold temperature []	Injection pressure [kgf/]
Polycarbonate (PC)	General	-	PC	120	24	250 - 380	80 - 120	700 - 1500
	-	Glass fiber less than 10%	PC	120	24	270 - 380	80 - 120	700 - 1410
	-	Glass fiber 10%	PC	120	24	270 - 380	80 - 120	1050 - 2810
PROPERTY 2 (Elongation - Specific gravity)j
Resin	Grade	Fillers	Abbreviation #	Elongation[%]	Molding shrinkage[%]	Consecutive heat resistance[]	Thermal deflection temp. []	Specific gravity
Polycarbonate (PC)	General	-	PC	100 - 130	0.5 - 0.7	121 - 133	132 - 143	1.19 - 1.20
	-	Glass fiber less than 10%	PC	5 - 10	0.2 - 0.5	135	146	1.27 - 1.28
	-	Glass fiber less than 10% - 40%	PC	0.9 - 5.0	0.1 - 0.3	135	149 - 154	1.24 - 1.52
PROPERTY 3 (Tensile strength - impact strength)
Resin	Grade	Fillers	Abbreviation #	Tensile strength [kgf/]	Compressive strength [kgf/]	Bending strength [kgf/]	Impact strength [kgf/]
Polycarbonate (PC)	General	-	PC	550 - 735	844	950	66 - 100
	-	Glass fiber less than 10%	PC	630 - 675	984	1050	6.5
	-	Glass fiber 10% - 40%	PC	840 - 1760	914 - 1480	1200 - 2250	11

Polystyrene (PS)

Characteristics: Excellent liquidity; Less molding shrinkage, no water absorption; Due to its stable thermal character, thermal decomposition does not occur even at excessive molding temperature.; Excellent electric insulation and chemical resistance
Caution: If molding condition is inappropriate, deformation may develop and remain inside the part. This will cause cracks upon removal from the mold.; Excessive injection pressure may affect mold removal or cause development of flashs
Molding condition: In general, mold temperature is appropriate below 40 To improve surface brilliance, 60 - 70 is recommended.

PROPERTY 1 (Drying temperature - injection pressure)
Resin	Grade	Fillers	Abbreviation #	Drying temperature []	Drying time [hours]	Cylinder temperature []	Mold temperature []	Injection pressure [kgf/]
Polystyrene (PS)	General	-	GPPS	-	-	120 - 310	20 - 70	700 - 2110
	High impacts	-	HIPS	-	-	190 - 280	10 - 80	703 - 2110
	Thermal resistance	-	PS	-	-	190 - 280	20 - 80	703 - 2110
	-	Glass fiber 20% - 30%	PS	-	-	170 - 280	20 - 80	1050 - 2810
PROPERTY 2 (Elongation - Specific gravity)
Resin	Grade	Fillers	Abbreviation #	Elongation[%]	Molding shrinkage[%]	Consecutive heat resistance[]	Thermal deflection temp. []	Specific gravity
Polystyrene (PS)	General	-	GPPS	1.6 - 4.0	0.2 - 0.7	60 - 80	74 - 110	1.03 - 1.09
	High impacts	-	HIPS	13.0 - 50.0	0.2 - 0.8	59.8 - 82	72 - 104	1.03 - 1.06
	Thermal resistance	-	PS	2.0 - 60.0	0.2 - 0.6	-	-	1.05 - 1.09
	-	Glass fiber 20% - 30%	PS	1.0 - 2.0	0.1 - 0.3	82 - 93	97 - 110	1.20 - 1.33
PROPERTY 3 (Tensile strength - impact strength)
Resin	Grade	Fillers	Abbreviation #	Tensile strength [kgf/]	Compressive strength [kgf/]	Bending strength [kgf/]	Impact strength [kgf/]
Polystyrene (PS)	General	-	GPPS	350 - 840	809 - 1120	550 - 1000	1.1 - 2.2
	High impacts	-	HIPS	200 - 476	281 - 633	211 - 844	2.6 - 20.0
	Thermal resistance	-	PS	350 - 530	-	-	2.2 - 19.0
	-	Glass fiber 20% - 30%	PS	630 - 1050	949 - 1270	738 - 1410	1.4 - 2.2

Polyvinyl chloride (PVC)

Characteristics

High viscosity at the time of melting; Poor liquidity of molten plastic; Excellent chemical character such as anti-oxidant and anti-alkaline character; Poor climate resistance, weak against temperature difference
Caution

Temperature control is critical; if it is not properly done, the part may burn through thermal decomposition or corrode the mold.

For better transfer of injection pressure , sprue, runner and gate need to be thicker and shorter, and the thickness of the part made needs to be as thick as possible.

If ejection speed is too fast, friction heat may develop and cause combustion.

Molding condition

Molding should be performed within the injection pressure range of 800 - 1200kgf/

. It is advisable to set the pressure a little higher.

Molding temperature should be set lower, but in general, it is processed under 180 - 190

Reduce the injection speed

PROPERTY-1 (Drying temperature - injection pressure)
Resin	Grade	Fillers	Abbreviation #	Drying temperature []	Drying time [hours]	Cylinder temperature []	Mold temperature []	Injection pressure [kgf/]
Polyvinyl chloride (PVC)	Soft material	-	SPVC	-	-	140 - 190	10 - 60	562 - 1760
Polyvinyl chloride (PVC)	Hard material	-	HPVC	-	-	170 - 210	10 - 60	703 - 2810
PROPERTY 2 (Elongation - Specific gravity)
Resin	Grade	Fillers	Abbreviation #	Elongation[%]	Molding shrinkage[%]	Consecutive heat resistance[]	Thermal deflection temp. []	Specific gravity
Polyvinyl chloride (PVC)	Soft material	-	SPVC	200 - 450	1.0 - 5.0	-	-	1.35 - 1.6
Polyvinyl chloride (PVC)	Hard material	-	HPVC	40 - 80	0.1 - 0.5	54.2 - 105	57.0 - 82	1.30 - 1.58
PROPERTY 3 (Tensile strength - impact strength)
Resin	Grade	Fillers	Abbreviation #	Tensile strength [kgf/]	Compressive strength [kgf/]	Bending strength [kgf/]	Impact strength [kgf/]
Polyvinyl chloride (PVC)	Soft material	-	SPVC	100 - 240	63 - 120	-	2.2 - 100
Polyvinyl chloride (PVC)	Hard material	-	HPVC	385 - 630	562 - 914	703 - 1120	widely varied

Epoxy (EP)

PROPERTY 1 (Drying temperature - injection pressure)
Resin	Grade	Fillers	Abbreviation #	Drying temperature []	Drying time [hours]	Cylinder temperature []	Mold temperature []	Injection pressure [kgf/]
Epoxy (EP)	-	Glass fiber	EP	-	-	-	-	-
Epoxy (EP)	Low Specific gravity	Glass ball	EP	-	-	121 - 149	-	703 - 1050
PROPERTY 2 (Elongation - Specific gravity)
Resin	Grade	Fillers	Abbreviation #	Elongation[%]	Molding shrinkage[%]	Consecutive heat resistance[]	Thermal deflection temp. []	Specific gravity
Epoxy (EP)	-	Glass fiber	EP	4	0.1 - 0.5	149 - 260	-	1.6 - 2.0
Epoxy (EP)	Low Specific gravity	Glass ball	EP	-	0.6 - 1.0	-	-	0.75 - 1.0
PROPERTY 3 (Tensile strength - impact strength)
Resin	Grade	Fillers	Abbreviation #	Tensile strength [kgf/]	Compressive strength [kgf/]	Bending strength [kgf/]	Impact strength [kgf/]
Epoxy (EP)	-	Glass fiber	EP	703 - 1410	1760 - 2810	703 - 4220	10.9 - 163
Epoxy (EP)	Low Specific gravity	Glass ball	EP	176 - 281	703 - 1050	352 - 492	0.82 - 1.36

Phenolic resin (PF)

PROPERTY 1 (Drying temperature - injection pressure)
Resin	Grade	Fillers	Abbreviation #	Drying temperature []	Drying time [hours]	Cylinder temperature []	Mold temperature []	Injection pressure [kgf/]
Phenolic resin (PF)	-	-	PF	-	-	-	-	-
	High impact	Tree powder, Cotton	PF	-	-	183 - 222	-	703 - 1410
	High strength	Glass fiber	PF	-	-	165 - 199	-	352 - 1410
PROPERTY 2 (Elongation - Specific gravity)
Resin	Grade	Fillers	Abbreviation #	Elongation[%]	Molding shrinkage[%]	Consecutive heat resistance[]	Thermal deflection temp. []	Specific gravity
Phenolic resin (PF)	-	-	PF	1.0 - 1.5	1.0 - 1.2	121	-	1.21 - 1.30
	High impact	Tree powder, Cotton	PF	0.4 - 0.8	0.4 - 0.9	149 - 176	-	1.34 - 1.45
	High strength	Glass fiber	PF	0.2	0.1 - 0.4	176 - 288	-	1.69 - 2.0
PROPERTY 3 (Tensile strength - impact strength)
Resin	Grade	Fillers	Abbreviation #	Tensile strength [kgf/]	Compressive strength [kgf/]	Bending strength [kgf/]	Impact strength [kgf/]
Phenolic resin (PF)	-	-	PF	492 - 562	703 - 2190	844 - 1050	1.09 - 1.96
	High impact	Tree powder, Cotton	PF	352 - 633	155 - 253	492 - 984	1.31 - 3.27
	High strength	Glass fiber	PF	352 - 1270	1120 - 4920	703 - 422	1.63 - 100