Medium density polyethylene
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Alpha olefin is copolymerized in the synthesis process
MDPE (Medium density polyethylene)
Medium density polyethylene (MDPE) is copolymerized with alpha olefin in the synthesis process, and the density is controlled.
[Combustion characteristics] Flammable, can continue to burn after the fire, the upper end of the flame is yellow, the lower end is blue, burning will melt, there is liquid dripping, no black smoke, at the same time, emit the smell of paraffin burning.
【 Main advantages 】 Acid and alkali resistance, organic solvent resistance, excellent electrical insulation, low temperature, can still maintain a certain toughness. Surface hardness, tensile strength, rigidity and other mechanical strength are higher than LDPE, close to PP, tougher than PP, but the surface finish is not as good as PP.
[Main disadvantages] Poor mechanical properties, poor air permeability, easy deformation, easy aging, easy brittleness, brittleness lower than PP, easy stress cracking, low surface hardness, easy scratching. Difficult to print, printing, need to carry out surface discharge treatment, can not be electroplated, surface luster.
[Application] For extruding packaging film, rope, woven bag, fishing net, water pipe; Injection low-grade daily necessities and shells, non-load-bearing components, plastic boxes, turnover boxes; Extrusion blow molded containers, hollow products, bottles.
HDPE has countless applications, ranging from reusable thin-walled beverage cups to 5-gsl cans, consuming one-fifth of the HDPE produced domestically. The general melt index of injection grade is 5 ~ 10, and there are lower fluidity grades with toughness and higher fluidity grades with processability. Uses include daily necessities and food thin-wall packaging; Resilient, durable food and paint cans; High resistance to environmental stress cracking applications such as small engine fuel tanks and 90-gal waste tanks.
General HDPE melting point is 142℃, decomposition temperature is 300℃; The adjustable range of injection molding temperature is large. When injection molding, the general use temperature is 180℃-230℃; Because it is an olefin plastic, it does not absorb water, and does not need to be dried during production, but for product quality, it can be dried at 60 ° C for 1hr to discharge floating water; The melt viscosity of polyethylene is large, the flow length ratio is small, the thin-walled products may lack glue, so the gate and the flow channel are relatively large; Products are easy to carry static electricity, the surface is easy to absorb angstrom. The shrinkage rate was 16‰ and the overflow margin value was 0.05mm
