Performance and application of the hottest polyole

Performance and application of polyolefin resin

polyolefin refers to polyethylene, polypropylene and their copolymer resins. Due to its good comprehensive properties, easy processing and molding, and high thermal decomposition temperature (generally above 315cc), it is a widely used non heat sensitive universal crystalline resin. The performance of polyolefin plastic packaging products is not only related to the type, molecular weight and crystallinity of polyolefin resin, but also related to the production process of packaging products. For example, extrusion blowing method, extrusion salivation method, biaxial stretching method, etc. for the production of thin films, extrusion blowing or injection blowing method, extrusion blowing or injection blowing method for the production of hollow containers, as well as the use of solid-phase thermoforming method, etc. Different production methods have different properties

polyethylene was first synthesized in the laboratory by British ICI company in 1933, and was industrialized by ICI company in 1939. It is called high pressure polyethylene (hPPE) because it is polymerized from high purity ethylene monomer by high pressure method. This kind of polyethylene has low density, which is also called low density polyethylene (LDPE). HDPE was invented in Germany in 1953 and industrialized in 1955. In 1977, American UCC company developed LLDPE. In 1958, Mitsui Petrochemical Company industrialized the production of UHMWPE. Very low density polyethylene (VLDPE) was industrialized by UCC in 1984. In the mid-1990s, Dow Chemical Company of the United States, BASF company of Germany and Mitsui Petrochemical Company of Japan industrialized the production of new metallocene polyethylene (MPE)

polypropylene was invented and produced by Italy in 1955. Due to its superior performance, PP has become an important landmark progress in the plastic industry

at present, polyolefin products occupy the first place in the world plastic products market, followed by PVC and other general-purpose plastics. The annual output of PP in the world has reached 41.5 million tons, while that of PE has reached 50million tons

first, the performance of polyethylene resin

1. LDPE

LDPE is a white wax with a density of 0..925g/cm3. It can also purchase multiple sets of equipment to produce solid particles at the same time; It is a typical crystalline thermoplastic polymer with a crystallinity of%, and a melting point of 105-126cc; It has good flexibility, electrical insulation and low temperature resistance; It is flammable and has the phenomenon of burning droplets. When burning, it emits the smell of candles, and the flame is smokeless and colorless; It has good heat sealing, moisture resistance, and good air permeability and transparency; It is easy to be processed and molded, and can be extruded and injected. It has good melt fluidity and is not easy to undergo thermal decomposition. It is a resin with good thermal stability, and its thermal decomposition temperature is above 3150c; Grease resistance and organic solvent resistance are worse than pp. therefore, if the thickness is thin, grease or gasoline will leak when placed for a long time; As it is a non-polar substance, it is easy to carry static electricity, which is harmful due to the accumulation of static electricity caused by friction during high-speed production. Antistatic agents or antistatic devices need to be added; The surface tension is low, only 31 dyne/cm. Therefore, in surface decoration or printing, surface treatment must be carried out in advance to improve the affinity of the surface

2. HDPE

HDPE is a high-density polyethylene with a density of 0.941-0.970g/cm3. With the increase of density, the crystallinity of HDPE increases (%), the melting point increases (CC), and the rigidity, toughness, mechanical strength, solvent resistance, environmental stress cracking resistance, and permeability are better than LDPE. Like LDPE, HDPE is a colorless, odorless and non-toxic resin, which can be directly contacted with food or drugs. It is as flammable as LDPE, with burning dripping phenomenon, candle oil smell when burning, and good electrical insulation. I-idpe film has poor transparency but high strength, which is often used as shopping bags, garbage bags, etc. Like LDPE, it has good moisture resistance and can be used for the packaging of dry food with good preservation effect; Due to its high permeability, it is not suitable for vacuum packaging or modified atmosphere packaging. It can be used in the environment of - 40cc-80cc for a long time, and the embrittlement temperature is -65cc. Surface treatment is also required in advance when printing, gluing or painting; It can be extruded, injected and other molding processing, with high thermal decomposition temperature

3. Mdpe

mdpe is medium density polyethylene, and its performance is between high-density polyethylene and low-density polyethylene. Its application and processing are also the same as HDPE and LDPE

4, lldpe

lldpe is linear low-density polyethylene, which is a kind of ethylene. Octene copolymer. Because LLDPE has more short branches than HDPE, less long branches than LDPE, and narrower molecular weight distribution than LDPE, its rheological properties are significantly different from LDPE. Compared with LDPE, LLDPE has the following outstanding differences in performance: LLDPE is a five color odorless and tasteless solid particle with a density of 0..930g/cm3, and its crystallinity is between HDPE and LDPE; Non toxic, can be directly used in food and drug packaging; Compared with LDPE, the point is CC higher than LDPE, and the melt viscosity is large. At the same melt temperature, the melt viscosity of LLDPE with the same molecular weight is more than 10 times that of LDPE. Therefore, the main motor power is much larger than that of LDPE in processing, for example, the medium 65mm extruder only needs kW main motor in processing LDPE, while adding 7-lldpe requires kW main motor. Liu. The viscosity of LLDPE melt is affected by melt temperature, Due to the great influence of shear stress, it is necessary to adopt methods to improve the processing speed. For example, in order to speed up the plasticizing time and strengthen the plasticizing ability of the screw processing LLDPE, a high-speed screw combined with a pin and a mixing head is used, and the L/D ratio is generally above 32; LLDPE has better transparency than LDPE, and the temperature of heat sealing is about 10Y higher than LDPE. It has excellent thermal adhesion and excellent inclusion heat sealing, so it is often used as heat sealing layer in soft plastic packaging; LLDPE has good stress cracking resistance, which can be used for blending with HDPE to improve the stress cracking resistance of HDPE; According to the viscoelasticity of LLDPE, it can be used to make winding film

5, VLDPE

very low density polyethylene is a kind of polyethylene with a density less than 0.91g/cm '. Lcldpe is softer, has excellent heat sealing property, and has great stress and crack resistance. It is an excellent stress cracking resistance modifier for HDPE or other PE

6, mpe

metallocene polyethylene (MPE) is the same as LLDPE. Copolymers of higher olefins with high reactivity. MPE is a colorless, odorless, tasteless, non-toxic thermoplastic with excellent transparency and the same flammability as LDPE; Mpeh has better toughness, strength, transparency and cleanliness than other types of PE. Due to the relatively narrow molecular weight distribution, the shrinkage of products is small; MPE is the same as LLDPE, which is the difference in quantity. The melt viscosity is quite high. Both of them can reduce the melt viscosity by increasing the shear stress, which is one of the reasons why MPE has better processability than LLDPE; The melt tension of MPE is higher than that of LLDPE, and the film bubble stability of film blowing is better. Due to the high melt strength, the expansion ratio and traction ratio can be larger during film blowing. The film thickness of thin 2 and 220 split single double reducer foam granulator can be smaller without rupture; Like LLDPE, rope has excellent stress cracking resistance and is an excellent modifier for other PE to improve stress cracking resistance

7, EVA, EEA and other ethylene copolymers

EVA is a copolymer of ethylene and vinyl acetate, which is often used as a modifier or hot melt adhesive material for low temperature heat sealing in soft plastic packaging. The performance of EVA is related to VA content. With the increase of VA content, the melting point decreases, EVA polar Q increases, the solubility in organic solvents changes from insoluble to swelling to complete dissolution, and the viscosity increases. Therefore, EVA with low VA content is thermoplastic, while EVA with high VA content is elastomer. With the increase of VA content, the density, transparency, crystallinity, stress cracking resistance and; Hit intensity increased. Due to the limited thermal stability of EVA, thermal decomposition will occur above 232cc

eea is a copolymer of ethylene with methyl acrylate and ethylene with maleic anhydride. It is a heat sealing resin for compatibilizers in the soft plastic packaging industry

8. Ionic resin (10nomer)

ionic resin is characterized by excellent inclusion heat sealing, high strength and toughness; Medium impact strength, excellent thermal adhesion, especially suitable for coating and compounding with aluminum foil, nylon and PE. It is an excellent inner sealing material, which can have a high thermal sealing strength even if it is polluted

II. Properties of polypropylene resin

polypropylene can be divided into homopolymer and copolymer. In homopolypropylene, according to the different arrangement positions of methyl groups in propylene molecules, there are isotactic (methyl groups are arranged in the same direction), syndiotactic (methyl groups are arranged alternately on both sides) and random (methyl groups are arranged in disorder). In CO polypropylene, the copolymer of ethylene and propylene is mainly used

1. Properties of homopolypropylene

homopolypropylene is a colorless, odorless, non-toxic solid particle with a density of 0..91g/GM3, which can be used for the packaging of instruments and drugs; It is inflammable, with burning drops. When burning, it has the smell of candle oil, smokeless with flame, and yellow; It has good strength, rigidity 2.5 and wear resistance, and can be used continuously at 110-120cc for a long time; It cannot be used in the environment below 0 ℃, with poor cold resistance and brittle hair; Poor weather resistance, colorability and antistatic property, and surface treatment should be done before painting or printing; It has good moisture resistance and can be used for the packaging of dry food, but it has high permeability, so it can not be used for vacuum packaging and inflatable packaging alone; When the isotacticity is above 94%, the melt has good fluidity, easy processing and molding, high thermal decomposition temperature and excellent electrical insulation

syndiotactic and atactic polypropylene are generally not used for molding due to their low mechanical strength, and are by-products of isotactic polypropylene production. Random polypropylene is commonly used as an auxiliary material for hot melt adhesive and parent carrier resin

2. Properties of CO polypropylene

co polypropylene is mainly a copolymer of ethylene and propylene. With the increase of ethylene composition, the flexibility and cold resistance of CO polypropylene are improved,; The impact strength increases and the melting point decreases