1, physical properties:
Pure PP is semi-transparent ivory-white, waxy; non-toxic, odorless, tasteless milky white highly crystalline polymers, density 0.90-0.91g/cm3, is the lightest of the general-purpose plastics. Molding shrinkage: 1.0-2.5% It is especially stable to water, the water absorption rate in water is 0.01% in 24 hours, it has good molding property, but the shrinkage rate is large, and it is easy to make thick-walled products to be concave. Product surface gloss is good, easy to color.
2, mechanical properties:
PP (polypropylene) of high crystallinity, structural regularity, has good mechanical properties, its strength and hardness, elasticity are relatively good, but at room temperature and low temperature impact strength is poor, the molecular weight increases, the impact strength is also increased, but molding and processing performance deteriorates.PP (polypropylene) is the most prominent performance is the bending fatigue. The coefficient of dry friction is similar to that of nylon, but not as good as nylon under lubricating oil.
3, thermal properties:
Polypropylene's heat of combustion is very high, it is difficult to make flame-retardant products, PP (polypropylene) has a good heat resistance, melting point of 164-170 ° C, made of products can be sterilized at temperatures of 100 ° C or higher; in the absence of external forces 150 ° C does not deform. But the low temperature becomes brittle, not wear-resistant, easy to aging. The embrittlement temperature is -35℃. Can be used for a long time at about 100 degrees.PP is not suitable for use below 0oC.
Because homopolymer-type PP is very brittle at temperatures below 0oC, many commercial PP materials are irregular ****polymers with 1~4% ethylene added or pincushion-type ****polymers with a higher ratio of ethylene content. The *** polymer type of PP material has a lower heat distortion temperature (100°C), low transparency, low gloss, and low rigidity, but has greater impact strength.The strength of PP increases as the ethylene content increases.The Vicat softening temperature of PP is 150°C. The crystallinity of this material is higher than that of the polypropylene. Due to its high crystallinity, this material has good surface stiffness and scratch resistance properties.PP does not suffer from environmental stress cracking. PP also does not have oxidation resistance at high temperatures like PE.
4, chemical properties:
PP (polypropylene) chemical stability is very good, in addition to strong oxidizing agents and non-polar solvents can make PP degradation, (Example: concentrated sulfuric acid, concentrated nitric acid, fuming sulfuric acid, fuming nitric acid, chromic acid solution, halogens, benzene, carbon tetrachloride, chloroform), PP has a strong resistance to chemical attack. Lower concentration solutions are harmless to PP. However, low molecular weight aliphatic hydrocarbons, gasoline, xylene, chlorinated hydrocarbons, etc. can soften and swell PP (polypropylene). The degree of swelling of *** polymer is higher than that of homopolymer. after PP is removed from such solvents, its dimensions return to their original state. Due to the extreme surface inertness of PP, it is difficult to print, paint and bond on PP without using flame treatment or similar techniques.
5, electrical properties:
PP (polypropylene) has excellent high-frequency insulation properties, because it is almost non-absorbent, so the insulating properties are not affected by humidity.PP (polypropylene) has a high dielectric coefficient, as the temperature rises, it can be used to make the heated electrical insulating products, and it is also very high breakdown voltage.PP (polypropylene) voltage resistance, good resistance to electric arc, but the It has a high degree of static electricity and ages easily in contact with copper. Can make high purity PP, used in the semiconductor industry.
6, weathering:
PP (polypropylene) is very sensitive to ultraviolet light, ultraviolet spin resistance, resistance to other penetration performance is poor. Add zinc oxide, di-lauroyl thiopropionate, carbon black or similar opalescent fillers can improve its aging resistance.
7, molding properties :
1. Crystalline material, hygroscopicity, easy to melt rupture, long-term contact with hot metal decomposition.
2. Good fluidity, but the shrinkage range and shrinkage value is large, easy to occur shrinkage holes. Dents, deformation.
3. Cooling speed, pouring system and cooling system should be slow heat dissipation, and pay attention to control the molding temperature. The material temperature is low, the direction of the direction is obvious. Low temperature and high pressure is especially obvious, mold temperature is lower than 50 degrees, the plastic is not smooth, easy to produce poor fusion, leaving traces, more than 90 degrees prone to warping and deformation
4. Plastic wall thickness should be uniform, to avoid the lack of glue, sharp corners, in order to prevent the concentration of stress.
Two, PP (polypropylene) modification
PP (polypropylene) can be filled, reinforced, *** mixed, *** polymerization, cross-linking to modify. Add calcium carbonate, talc, inorganic minerals and other fillers can improve the PP (polypropylene) rigidity, hardness, heat resistance and dimensional stability; add glass fiber, asbestos fibers, mica, glass beads, etc. to improve the tensile strength, and can improve creep resistance, low-temperature impact resistance; add thermoplastic elastomers such as TPE / TPR or rubber to improve the impact performance, transparency and so on. The application is very wide, even Australia's banknotes are made of PP. Banknotes are made of biaxially oriented PP (BOPP), so that its durability improves the PP has an unusual resistance to chemical solvents, acid and alkali resistance.
Polypropylene is widely used in the production of plastic pipes, but PP is a material with poor resistance to aging, in order to improve the performance of PP, through the chemical modification method invented PP-B and PP-R resin.
PP-B resin is propylene and ethylene block **** polymer. Synthesis of propylene-ethylene block **** polymer to use two polymerization reactor. One for monomer propylene polymerization into homopolymer polypropylene, the other is the first reactor produced by the introduction of homopolymerization of PP ethylene to form propylene - ethylene block **** polymer, that is, the formation of ethylene - propylene elastic segment.PP-B resin is essentially homopolymerization of PP and ethylene **** polymerization modification. The modified PP-B resin has both PE and PP performance advantages.
PP-R is based on **** poly PP modified with ethylene from the random polypropylene. The smallest molecular weight of random PP is only a few tens of thousands, small cohesion, low melting point, poor mechanical properties. Only through the ethylene modified random PP has practical application value. The modification process is to gasify propylene and feed it into the reactor by gas phase method, and use the airlock system to send the material from the first reactor to the second reactor, and add ethylene in the second reactor. Using high activity, high selectivity of propylene catalyst, added to the upper part of the reactor, by stirring it evenly dispersed to the powder layer, by controlling the proportion of ethylene and propylene to form a random **** polymer. This polymer changes the configuration of the PP molecular chain, so that ethylene is randomly and uniformly polymerized on the molecular chain of PP.
Compared with ordinary PP, PP-R material stress crack resistance has been greatly improved, in the temperature and internal and external pressure, its performance decay is very slow, is currently used as one of the most ideal materials for the production of hot and cold water pipes.
Like most polymers, polypropylene oxidizes, especially during melt processing. In the case of PP, the polymer is protected by removing free radicals that attack the tertiary hydrogen. For PP used for long periods at high temperatures, complex multi-component stabilizer systems are used; where odor or taste is limited, the stabilization system must be very simple. If used for sunlight (UV) protection carbon black can be added or a specialized stabilization method can be used.
Three, PP (polypropylene) molding process
Polypropylene's excellent flow properties and a wide range of flow rates, as well as other unique polymer properties combine to give it excellent processability. There are many methods of molding, including injection molding, blow molding, vacuum thermoforming, coating, rotational molding, plating and foaming, and spraying on metal surfaces. Among them, the proportion of injection molding is the largest, in order to prevent shrinkage and deformation caused by post-crystallization, the products generally need to be treated by hot water immersion.
The use of tubular water-cooled excitation process can be processed into PP *** extrusion blown film as well as monolayer film.PP can also be extruded into tubular products, such as beverage straws and drinking water hose.PP also has a use in the coating of cables. In general, low flow rate formulations are used for thick walled products and those requiring toughness. High flow rate materials are used for thin-walled parts and those requiring fast processing.
Injection Molding Process Conditions
Drying Process: Drying process is not required if stored properly. The pre-drying temperature is around 80°C.
Melting temperature: 220~275C, be careful not to exceed 275C.
Mold temperature: 40~80C, 50C is recommended. The degree of crystallization is mainly determined by the mold temperature.
Injection Temperature: Between 180-200C,
Injection Pressure: Injection Pressure is 68.6-137.2MPa,can be as big as 1800bar.
Injection Speed: Usually,using high speed injection can minimize the internal pressure. If there are defects on the surface of the product, then low speed injection at higher temperatures should be used.
Runners and Gates:For cold runners, typical runner diameters range from 4 to 7 mm.It is recommended to use injection ports and runners that are round through and through. All types of gates can be used. Typical gate diameters range from 1 to 1.5 mm, but gates as small as 0.7 mm can be used. For edge gates, the minimum gate depth should be half the wall thickness; the minimum gate width should be at least twice the wall thickness. PP materials are perfectly suited for hot runner systems.
The mold temperature is 50-90°C, with higher temperatures for higher dimensional requirements. Core temperature is lower than the cavity temperature of more than 5 ℃, runner diameter of 4-7mm, needle gate length of 1-1.5mm, the diameter can be as small as 0.7mm. edge gate length the shorter the better, about 0.7mm, the depth of half of the wall thickness, the width of the wall thickness is twice, and with the length of the melt flow in the mold cavity gradually increased. Mold must have good exhaust, exhaust hole depth O.025mm-O.038m, 1.5mm thick, to avoid shrinkage marks, we must use a large and rounded injection and round runners, the thickness of the reinforcement to be small (for example, is the wall thickness of 50-60%). Homopolymer PP manufactured products, the thickness can not exceed 3mm, otherwise there will be bubbles (thick-walled products can only be used **** poly PP).
Four, PP (polypropylene) uses
Used in the automotive industry (mainly using PP containing metal additives: fenders, ventilation ducts, fans, etc.), appliances (dishwasher door gaskets, dryer ventilation ducts, washing machine frames and lids, refrigerator door gaskets, etc.), consumer products (lawn and garden equipment such as lawn mowers and sprinklers, etc.).
It can be used as engineering plastics for making TV sets, radio shells, electrical insulation materials, anti-corrosion pipes, plates, storage tanks, etc. It is also used in the production of flat wires, fibers, packaging films, tubs, buckets, furniture, films, woven bags, bottle caps, automobile bumpers and so on.
It is also anti-bacterial production, suitable for disposable syringes and medical equipment.
Fiber is a major market for PP. Its tensile strength can be increased as much as 15 times by stretching or orientation. Draw products include clothing, diapers, nonwovens. Furniture leather, agricultural bags, cords, paving fabrics, tapes. Carpet and rug backing villages.PP can also be cast or directionally stretched into films. Directional film can be used as cigarette. Candy and many items of packaging materials; non-directional film for capacitors or packaging materials.
PP sheets are used to make thermoformed food containers, which, along with moisture barrier and gas and odor transmission properties must comply with FDA regulations. New very-low-modulus grades can be calendered and compete with soft vinyl resins.
PP can be processed into hollow products by injection blow molding, extrusion blow molding or stretch blow molding. High-melt-strength grades of PP have been developed to improve blow-molding and thermoforming properties.
Quick-processing extrusion adhesive grades of PP are available on the market; and polypropylene's excellent electrical properties make it suitable for insulating telephone wires and data-transmission cables.
Many different types of injection-molded parts are made from PP or its impact-resistant*** polymers. In the automotive market. **** polymers are used as interior assemblies and panels, exterior components, and batteries; homopolymers and filler grades are used for engine case covers or as instrument panels.
Glass filler grade PP is used as trim or parts of appliances. All filler-free PP resins can be used for housewares, medical appliances, including disposable radiocidal supplies, primarily using low-cost homopolymers and random*** polymers. Thin-wall molded containers to expand the scope of the PP traditional packaging market, such as tamper-proof sealers and dosers
Polypropylene (PP) mute drain series products, is to adapt to the market demand, the introduction of advanced international technology, the application of advanced sound-deadening technology developed a new type of building drainage pipe fittings, its characteristics are:
1, superior quietness:
2
2, strong chemical resistance: the inner layer of the pipe can resist acid up to PH2, alkali up to PH12. can discharge PH2-PH12 liquid.
3, excellent high temperature resistance: can withstand 95 degrees of hot water.
4, good impact resistance: the hard outer layer not only protects the middle structure, but also ensures that the pipe has good impact resistance.
5, advanced flexible connection: easy to dismantle and install, not limited by the installation environment, reduce installation costs. Watertight and self-adjusting performance, without the use of expansion joints, can save fittings at the same time, to avoid water impact on the wall of the pipe when the sound is transmitted to the next fittings.
6, strong environmental protection: non-toxic products can avoid environmental pollution. Comparison with other pipes (Ф110mm for example)
To achieve noise reduction through the following ways; change the internal microstructure of the pipe, increase the density and thickness of the pipe, adding special sound-absorbing materials.
Comparison with other pipes (Ф110mm for example)
Pipe fittings name
PVC-U cast iron pipe polypropylene mute drainpipe
Materials
PVC cast iron special sound-absorbing materials
Density of the pipe g/cm3
1.4 7.8 1.4-1.9
The pipe Wall thickness mm
3.2 5.5 4.5
Noise level dB
58 46.5 45
Easy installation:
Installation of piping, the distance between the two socket-type flexible joints shall not be more than 3 meters at the furthest, and for the need to compensate for the length of the pipe can be inserted into the socket and then withdrawn after the pipe is fully inserted into 10mm. The socket type flexible connection between the pipe fittings can absorb the thermal expansion of the pipe up to 10mm.
1. Cut the pipe to the required length, remove the burrs from the pipe ports and chamfer 30 degrees.
2. Insert the pipe into the bottom of the fitting's socket and mark the interface between the pipe and the fitting with a pen, then pull the pipe out by 10mm based on this mark and make a second mark. Clean the outside of the pipe and the inside of the fitting and apply lubricant (no oil or grease).
3. Special rubber sealing ring coated with lubricant, put into the tube groove, insert the tube directly into the tube to the second mark can be.