Plastic Injection Molding

There are various kinds of plastics applied for automotive industry to be molded as interior parts, exterior parts and functional parts by processes of plastic injection molding , blow molding, extrusion molding, compression molding and so on. While according to using feature we also classify plastics as general-purpose plastics, engineering plastics and special-use plastics.

General-purpose plastics are plastics of huge output, great molding feature, cheap cost and widely using such as PP, PE, PVC, PS and ABS which are all thermal plasticity polymers.

It’s a white ceraceous polymer, transparent, light and of great fluidity in injection moulding process. Its water absorbency is lower than 0.02% and shrinkage 1.0~3.5%, proper product wall thickness 1.5~2.5mm.

Due to its inflammability and brittle point, there will be additives to put in pp production like fire retardant, EPDM, TD, GF,etc. in industrial applications. Instrument panel, door panel, pillars, bumper, water tank, decorative trims may use PP.

It is one of the lightest plastics, white ceraceous, semi-transparent, great water resistance, acid & alkali resistance and organic solvent resistance, great Electrical insulation. Its shrinkage is 1.5~4.0% and proper product wall thickness 1.0~2.5mm. Flame retardant is always put in pp for its defect of inflammability. Auto parts that may use PE includes oil tank, air duct, seat cover, air stack assembly.

PVC is a multi-component polymer, presenting different mechanical features with different compositions, normally classified as soft PVC (shrinkage 2~2.3%) and hard PVC (shrinkage 1~1.5%) . Its proper product wall thickness is 2~3.5mm. As PVC costs low and has great processing property and general mechanical property, vehicles use PVC for IP board envelop skin, steering wheel, lining board, floor cover, etc.

PS is transparent and water insulating, and material of glass imitation, also called hard plastic with great fluidity. Its shrinkage is 0.4~0.7% and proper product wall thickness 2~3mm. PS always with C4H6 (rubber ingredient) is to make HIPS so anti-impact strength and hardness are largely improved.

PS is widely used for meter housing, lamp shade and other lighting products. PS is also processed by foam molding to make into packing material or heat insulating material for auto roof lining production. And being composed with other material many PS alloy plastics can be produced such as SMA which can be made for automotive instrument panel frame work.

ABS is white with shrinkage of 0.4~0.7%, commonly called super-unbreakable plastic. Its proper product wall thickness can be 1.8~3mm.

ABS is very popular for its low cost and performance. If the product needs surface process like water transfer printing and painting, ABS shall be chosen otherwise substitutes like AES and ASA are better for ABS is worse in weather fastness. For auto parts like decorative trim, handle and armrest, license plate, spoiler plate, radiator grille, etc. are made of ABS and mostly by plastic injection molding process.

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