How many kinds of plastic forming craft have, specific practice is how, have what advantage or disadvantage?
Plastic probably has extrusion, injection, molding, blow molding, roll-casting, casting, dip plastic and other kinds of molding processes, according to different materials and products specific selection, it is difficult to say the advantages or disadvantages.Below I use PE plastic processing method to say simply, PE can be made by very wide different processing methods.With ethylene as the main raw material and propylene, 1-butene and hexene as copolymers, under the action of catalyst, slurry polymerization or gas phase polymerization process was adopted, resulting polymers were obtained through flash evaporation, separation, drying, granulation and other processes, and the products with uniform particles were obtained.Include such as sheet extrusion, film extrusion, pipe or profile extrusion, blow molding, injection and roll molding.Extrusion: the grade used in extrusion production generally has melt index less than 1 and MWD of medium to wide.In the process of processing, the suitable melt strength can be obtained with low MI.Wider MWD grades are more suitable for extrusion because they have higher production speed, lower die pressure and a reduced melt fracture trend.PE has many extrusion USES, such as wire, cable, hose, pipe and profiles.Pipe applications range from small section yellow pipes for natural gas to thick black pipes with a diameter of 48in for industrial and urban pipelines.Large diameter hollow walls have grown rapidly as replacements for concrete rainwater drainage pipes and other sewer pipes.Plate and heat forming: the heat forming lining of many large picnic coolers is made of PE and has toughness, light weight and durability.Other sheet and heat forming products include fender, tank liner, tray cover, transport box and tank.A large number of rapidly growing sheet materials are used in mulch or poolside villages, which are based on the toughness, chemical resistance and impermeability of MDPE.Fax: over one third of the hdpepe sold in the United States is for blow molding purposes.These range from bottles filled with bleach, oil, detergent, milk and distilled water to large refrigerators, car fuel tanks and cans.The characteristics of blow molding grade, such as melt strength, es-cr and toughness, are similar to those used in sheet metal and thermal forming applications, so similar grade can be adopted.Injection - blow molding is usually used to make smaller containers (less than 16oz) for packaging drugs, shampoo and cosmetics.One of the advantages of this process is that the production bottle is automatically removed from the corner, and there is no need for the post-finishing process like the general blow molding process.Although some narrow MWD grades are used to improve surface finish, the wide to wide MWD grades are generally used.HDPE has countless applications, ranging from reusable thin-walled beverage cups to 5-gsl cans, consuming one-fifth of the domestically produced HDPE.The general melt index of injection molding grade is 5 ~ 10, and there are high fluidity grade with low toughness and high processability.USES include daily necessities and food thin-walled packaging;Tough and durable food and paint cans;High resistance to environmental stress cracking applications such as small engine fuel tanks and 90-gal garbage cans.Materials used in this process are generally crushed into powder material to melt and flow in a heat cycle.Roll-molding USES two types of PE: general purpose and crosslinking.The usual density range for general-purpose MDPE/HDPE is from 0.935 to 0.945g/CC, with narrow MWD, makes products with high impact and minimum warping, its melt index range is generally 3-8.Higher MI grades are generally not applicable because they do not have the impact and anti-environmental stress cracking qualities desired by rolling products.High performance rolling plastic applications make use of its unique properties of chemically crosslinked products.These grades in the first phase of the molding cycle, good fluidity, and then cross-linked to form its excellent anti-environmental stress cracking, toughness.Wear resistance and weather resistance.Crosslinked PE is unique for large containers, ranging from 500-gal chemical storage tanks to 20,000-gal agricultural storage tanks.PE film blowing: PE film processing is generally done by ordinary blowing film processing or horizontal extrusion processing.Most PE is used in thin films and can be used for general low density PE (LDPE) or linear low density PE (LLDPE).HDPE film grade is generally used in places that require superior tensile strength and excellent impermeability.For example, HDPE film is often used in commercial bags, grocery bags and food packaging.