Several gratings with different materials
The material of the grating should have high transparency, high refractive index, good gloss, strong plasticity, stability and other properties. The materials used for making toys and food packaging also require non-toxic and harmless. In order to ensure the three-dimensional effect of three-dimensional printing, the material of the grating should be carefully considered. At present, three kinds of grating plates made of polystyrene (PET), polypropylene (PP) and polyvinyl chloride (PVC) are mainly used in the market.
â‘ Polystyrene resin (PET)
Polystyrene (PET) is used to make hard plastic gratings and can be printed directly with ordinary ink. The polystyrene raw material is processed by injection molding to form a concave-convex cylindrical mirror grating.
Polystyrene is colorless and transparent (transparency is 88% -92%), refractive index is 1.59-1.6, non-ductile and flammable. Because of such a high refractive index, it has good gloss. Its tensile strength is 3.52-6.33MPa, its bending strength is 6.12-9.84MPa, and its thermal deformation temperature is 70-98 ° C.
The chemical properties of polystyrene are resistant to certain mineral oils, organic acids, alkalis, salts, lower alcohols and their aqueous solutions. It is softened after being eroded by hydrocarbons, ketones, higher fatty esters, etc. It is soluble in aromatic hydrocarbons and toluene, ethylbenzene and styrene monomers. In some cases, the degree of erosion of polystyrene by chemical reagents can be reduced by annealing, stress relief and other measures.
Polystyrene has good stability, high picture quality, non-toxic raw materials, and high chemical resistance, but it is more difficult to bond and process. Mostly used in toys, fine advertising, etc.
â‘¡ Polypropylene (PP)
Polypropylene (PP) can be printed directly with ordinary ink, but the surface should be treated with sparks, and the ink dries faster than polystyrene.
Polypropylene is softer than polystyrene and harder than polyvinyl chloride. The stability is high, but the image quality is average. The raw materials are non-toxic, low chemical resistance, easy to bond processing, mostly used in packaging, stationery, etc.
â‘¢ Polyvinyl chloride (PVC)
Polyvinyl chloride (PVC) is used to make soft plastic cylindrical lens grating. A hot oil press is required to press and shape the picture and the PVC film base through a metal grating drum or grating plate.
Polyvinyl chloride is a polymer compound formed by polymerizing chlorinated olefins and is difficult to burn. Although polyvinyl chloride and polyethylene are both milky white, polyvinyl chloride can be made into a colorless, transparent and shiny film, and can produce various softness films according to the content of plasticizer. The fastness of this material after pulse heat sealing and high frequency heat sealing is also large. The chemical properties of PVC have good chemical resistance, but poor thermal stability and light resistance. Hydrogen chloride begins to decompose at 140 ° C, and stabilizers need to be added during manufacturing. Polyvinyl chloride has a chlorine content of 56% -58%. Low molecular weight is easily soluble in ketones, esters and chlorinated hydrocarbon solvents; high molecular weight is difficult to dissolve.
Polyvinyl chloride has low stability and rough picture quality. In addition, because the PVC grating is toxic and not environmentally friendly, it is generally not used in toys and food packaging products in European and American countries.
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