스크랩 주요 수지 물성 정리

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About ABS materials

Generic Class

ABS (Acrylonitrile-Butadiene-Styrene)

Typical Applications

Automotive (instrument and interior trim panels, glove compartment doors, wheel covers, mirror housings, etc.), refrigerators, small appliance housings and power tools applications (hair dryers, blenders, food processors, lawnmowers, etc.), telephone housings, typewriter housings, typewriter keys, and recreational vehicles such as golf carts and jet skis.

Injection Molding Processing Conditions

Drying	ABS grades are hygroscopic and drying is required prior to processing. Suggested drying conditions are 80 - 90 C (176 - 195 F) for a minimum of 2 hours. The material moisture content should be less than 0.1%
Melt Temperature	200 - 280 C (392 - 536 F); Aim: 230 C (446 F)
Mold Temperature	25 - 80 C (77 - 176 F). (Mold temperatures control the gloss properties; lower mold temperatures produce lower gloss levels)
Material Injection Pressure	50 - 100 MPa
Injection Speed	Moderate - High

Chemical and Physical Properties

ABS is produced by a combination of three monomers: acrylonitrile, butadiene, and styrene. Each of the monomers impart different properties: hardness, chemical and heat resistance from acrylonitrile; processibility, gloss, and strength from styrene; and toughness and impact resistance from butadiene. Morphologically, ABS is an amorphous material.

The polymerization of the three monomers produces a terpolymer which has two phases: a continuous phase of styrene-acrylonitrile (SAN) and a dispersed phase of polybutadiene rubber. The properties of ABS are affected by the ratios of the monomers and molecular structure of the two phases. This allows a good deal of flexibility in product design and consequently, there are hundreds of grades available in the market. Commercially available grades offer different characteristics such as medium to high impact, low to high surface gloss, and high heat distortion.

ABS offers superior processibility, appearance, low creep and excellent dimensional stability, and high impact strength.

About PC materials

Generic Class

PC (Polycarbonate)

Typical Applications

Electronic and business equipment (computer parts, connectors, etc.), appliances (food processors, refrigerator drawers, etc.), transportation (head lights, tail lights, instrument panels, etc.).

Injection Molding Processing Conditions

Drying	PC grades are hygroscopic and pre-drying is important. Recommended drying conditions are 100 - 120 C (212 - 248 F) for 3 to 4 hours. Moisture content must be less than 0.02% prior to processing.
Melt Temperature	260 - 340 C (500 - 644 F); higher range for low MFR grades and vice-versa
Mold Temperature	70 - 120 C (158 - 248 F); higher range for low MFR grades and vice-versa
Material Injection Pressure	As high as possible for rapid molding
Injection Speed	Slow injection speeds when small or edge gates are used; high speeds for other types of gates

Chemical and Physical Properties

Polycarbonate is a polyester of carbonic acid. All general-purpose polycarbonates are based on bisphenol A. The bisphenol A component of the molecule contributes to the high glass transition temperature (150 C / 302 F). The rotational mobility of the carbonyl group within the molecule contributes to the high ductility and toughness of the material.

PC is an amorphous engineering material with exceptionally good impact strength, heat resistance, clarity, sterilizability, flame retardancy, and stain resistance. The notched Izod impact strength of PC is very high and mold shrinkage is low and consistent (.1 -.2 mm/mm).

High molecular weight PCs (which translate to low melt flow rate) have higher mechanical properties, but processibility of such grades becomes difficult. The type of PC chosen for a particular application should be based on the desired criteria (for high impact properties, use a low-MFR PC; conversely, for optimal processibility, use a high-MFR PC).

The melt viscosities are typically Newtonian up to shear rates of 1000 1/s and decrease beyond that. The Heat Deflection Temperature Under Load is typically between 130 -140 C (266 - 284 F) and the Vicat Softening Point is typically around 155 C (311 F).

About PMMA materials

Generic Class

PMMA (Polymethyl methacrylate)

Typical Applications

Automotive (signal light devices, instrument panels, etc.), medical (blood cuvettes, etc.), industrial (video discs, lighting diffusers, display shelving, etc.), consumer (drinking tumblers, stationery accessories, etc.)

Injection Molding Processing Conditions

Drying	PMMA is hygroscopic and must be dried prior to molding. Drying at 90 C (194 F) for 2-4 hours is recommended.
Melt Temperature	240 - 280 C (460 - 536 F)
Mold Temperature	35 - 80 C (90 - 176 F)
Injection Speed	Moderate

Chemical and Physical Properties

Pellets for injection molding are made either by bulk polymerization of methyl methacrylate followed by extrusion and pelletization or by polymerization in an extruder. Formulations vary by molecular weight and physical properties such as flow rate, heat resistance, and toughness. Higher molecular weight grades are tougher than lower molecular weight grades. High flow formulations are generally preferred for molding.

Heat deflection temperature under load varies from 75 C (167 F) for high flow materials to 100 C (212 F) for low flow (high molecular weight) materials.

PMMA has excellent optical properties and weatherability. The white light transmittance is as high as 92%. Molded parts can have very low birefringence which makes it ideally suited as a material for video discs.

PMMA exhibits room temperature creep. The initial tensile strength is high but under long term, high stress loading, it exhibits stress craze. Impact strength is good but it does show some notch sensitivity.

About POM materials

Generic Class

POM (Polyacetal or Polyoxymethylene)

Applications

Acetals have a low coefficient of friction and good dimensional stability. This makes it ideal for use in gears and bearings. Due to its high temperature resistance, it is used in plumbing (valve and pump housings), and lawn equipment.

Injection Molding processing conditions

Drying	Not usually required but the material should be stored in a dry atmosphere.
Melt Temperature	180 - 230 C (356 - 446 F) for homopolymer; 190 - 210 C (374 - 410 F) for copolymer
Mold Temperature	50 - 105 C (122 - 221 F); Higher mold temperatures are preferred for precision molding which reduce post-molding shrinkage
Material Injection Pressure	70 - 120 MPa
Injection Speed	Medium - High

Runners and Gates

Any type of gate may be used. When using tunnel gates, the short type is preferred. Insulated, hot tip runners are preferred for homopolymers; both internally and externally heated hot runners may be used in the case of copolymers.

Chemical and Physical Properties

Acetals are tough, resilient materials and exhibit good creep resistance, dimensional stability, and impact resistance even at low temperatures. Acetal grades are either homopolymers or copolymers. Homopolymers have better tensile strength, fatigue resistance and hardness but are difficult to process. Copolymers have better thermal stability, chemical resistance and processibility. Both homopolymers and copolymers are crystalline and have low moisture absorption.

Copolymers may be used continuously at air temperatures up to 100 C (212 F); homopolymers have slightly higher temperature resistance. Many grades of acetal materials are available, tailored to different applications.

High crystallinity levels of acetals lead to relatively high shrinkage levels of 0.02 - 0.035 mm/mm. Differential shrinkage is observed with reinforced grades.

About PP materials

Generic Class

PP (Polypropylene)

Typical Applications

Automotive (mostly mineral-filled PP is used: dashboard components, ductwork, fans, and some under-hood components), appliances (doorliners for dishwashers, ductwork for dryers, wash racks and lids for clothes washers, refrigerator liners, etc.), consumer products (lawn/garden furniture, components of lawn mowers, sprinklers, etc.).

Injection Molding Processing Conditions

Drying	Not normally necessary if proper storage is used
Melt Temperature	220 - 280 C (428 - 536 F); not to exceed 280 C
Mold Temperature	20 - 80 C (68 - 176 F); suggested: 50 C (122 F) The crystallinity level is determined by the mold temperature.
Material Injection Pressure	Up to 180 MPa

Injection Speed

Typically, fast injection speeds are used to minimize internal stresses; if surface defects occur, slow speed molding at a higher temperature is preferred. Machines capable of providing profiled speed is highly recommended.

Runners and Gates

In the case of cold runners, typical diameters range from 4 - 7 mm. Full round sprues and runners are recommended. All types of gates can be used. Typical pin gate diameters range from 1 - 1.5 mm, but diameters as low as 0.7 mm may be used. In case of edge gating, the minimum gate depth should be half the wall thickness and the width should be at least double the thickness. Hot runners can readily be used for molding PP.

Chemical and Physical Properties

PP is produced by the polymerization of propylene using stereospecific catalysts. Mainly, isotactic PP is produced (the methyl groups lie on one side of the carbon chain). This linear plastic is semicrystalline because of ordered molecular structure. It is stiffer than PE and has a higher melting point. The PP homopolymer becomes very brittle at temperatures higher than 0 C (32 F) and for this reason, many commercially available grades are random copolymers with 1 - 4% ethylene or block copolymers with higher ethylene content. Copolymers have a lower heat distortion temperature (approximately 100 C / 212 F), less clarity, gloss, and rigidity, but greater impact strength. The material becomes tougher as the ratio of ethylene increases. The Vicat softening point is approximately 150 C (302 F). Because of high levels of crystallinity, the surface hardness and scratch resistance is higher for these materials.

PP does not have environmental stress cracking problems. PP is usually modified by addition of glass fibers, mineral fillers, or thermoplastic rubbers. The MFR of PP ranges from 1 to 40; lower MFR materials have better impact strength but lower tensile strength. The copolymer is tougher than the homopolymer of the same MFR. The viscosity is more shear and temperature sensitive than PE.

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

Both homopolymer and copolymer PP offer excellent resistance to moisture and good chemical resistance to acids, alkalis, and solvents. However, it is not resistant to aromatic hydrocarbons such as benzene, and chlorinated hydrocarbons such as carbon tetrachloride. It is not as resistant to oxidation at high temperatures as PE.