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About molding methods

Various FRP molding methods

FRP can be molded using the following methods

  • Hand lay-up method

    【Boats, tanks, septic tanks, housings】

    After applying a mold release agent to the mold, gel coat is applied, after curing, glass mat and cloth are set in the mold, resin is applied and impregnation curing is carried out with a roll.

  • Pultrusion molding method

    【Poles, fishing rods, angles】

    The roving is impregnated with resin in advance, heat-cured in a mold and pulled out.

  • Spray-up method

    【Bathtubs, septic tanks, containers, boats】

    After applying a release agent to the mold, a gel coat is applied and after curing, the resin, curing agent and roving are sprayed together in a spray machine and cured.

  • Filament-widening method

    【Pipes, tanks, ducts】

    Glass roving is impregnated with resin in advance and cured by wrapping it around a rotating mandrel under tension.

  • Cold press method

    【Water tanks, containers】

    Glass mat and cloth are placed in a mold made of FRP reinforced with Resikon, resin is poured into the mold and cured by pressure impregnation.

  • Rotational molding method

    【Pipes, tanks】

    Glass mat, cloth, etc. are placed inside a hollow mandrel, and resin is poured into the mandrel while rotating, impregnating and curing.

  • SMC method

    【Bathtubs, bathroom floor pans, automotive parts】

    SMC cut to the required dimensions is charged into a die and cured under high temperature and pressure.

  • Preform matched die method

    【Water tank panels, helmets】

    A preform prepared in advance is set in the die, charged with resin and cured at high temperature and high pressure.

Features of different FRP molding methods

POLYHOPE™ cures at both room temperature and high temperatures, and the curing time can be easily adjusted. Therefore, you can choose the molding method that best suits your purpose, from the general hand lay-up method to high-purity injection molding.

molding method
Hand lay-up Spray-up Cold press Resin injection Preform matched die (MMD) SMC BMC Filament winding Drawing
Design cost Cheapest Cheapest Medium Medium High High High Medium to high Medium to high
molding material cost Cheap Cheap Medium Medium High High High Medium Medium
Number of man-hours Max Large Medium Medium Small Small Small Small Small
Size limit No No Yes Yes Yes Yes (medium) Yes (small) Yes Yes
Proficiency Required Required Not required Not required Not required Not required Not required Not required Not required
Shape Relatively simple Relatively simple Relatively simple Relatively simple Complex possible Complex possible Complex possible Limited to rotating bodies Limited to one direction
Wall thickness Uneven Uneven Constant Constant Constant Constant Constant Constant Constant
Other High labour costs - Gel coatings possible Gel coatings possible - Joints by flow Joints by flow High strength Continuous forming
Glass substrate Matt glass cloth
Roving cloth		 Roving cloth Continuous matt matte Continuous matt matte Chopped strand Chopped strand Chopped strand Roving yarn tape Roving continuous matt
Normal glass content (%) 27～45 30 25～35 25～35 30 25～30 15～25 50～75 50～70
Maximum filler content (phr) 50 50 50 50 100 250 250 50 50
Forming temperature (°C) Room temperature Room temperature 15～60 15～60 100～150 120～150 120～160 15～60 130～160
molding pressure
(×10-1MPa)		 Contact pressure Contact pressure 2～5 1～10 7～21 7～200 15～140 Winding force Pulling force
molding cycle 30min-1day 30min-1day 15-60min 20-60min 1-5min 0.5-5min 0.5-5min 0.5-6m/min 0.5-3m/min
Minimum thickness 1.5mm 1.5mm 1.5mm 2mm 0.7mm 1.3mm 1.5mm 2.5mm 1.0mm
Maximum thickness 25mm 12mm 13mm 13mm 7mm 25mm 25mm 75mm 50mm
Thickness variation ±0.5mm ±0.5mm ±0.5mm ±0.5mm ±0.2mm ±0.13mm ±0.05mm ±0.3mm ±0.1mm
Minimum radius 6.4mm 6.4mm 6.4mm 6.4mm 3.2mm 1.4mm 0.8mm 3.2mm 1.0mm

Comparison of properties with various materials

Material type molded product FRP molded products (note) SMC molded product Aluminium Steel Wood Hard vinyl chloride
Specific gravity 1.2 1.5 1.8 2.7 7.8 0.4～0.8 1.4
Tensile strength (MPa) 47 147 90 88 333～402 45～88 99～59
Flexural strength (MPa) 110 216 180 197 - 99～98 69～108
Flexural modulus (GPa) 4.4 9.8 10.5 68.6 206 8.0～15.0 2.9
Compressive strength (MPa) 155 255 180 - - 29～59 59～78

Note: Laminates made with a glass fiber content of 30%. The physical properties listed in this table are representative values and not standard values.

Japan Composite Co., Ltd.

8th Floor, Muromachi Furukawa Mitsui Building (COREDO Muromachi 2),
2-3-1 Nihombashi-Muromachi, Chuo-ku, Tokyo 103-0022