PET plastics has high film-forming property because of its highly symmetrical molecular structure and a certain cystallization orientation ability.PET plastics has good optical property and weathering resistance. Amorphous PET plastics has good optical transparency. What's more, PET plastics' PET molecular structure has nice abrasion performance, dimensional stability, and electric insulativity. Bottles made of PET are subjected to a wide range of applications, on account of its great intensity, good transparency,non poisonous,anti-permeability,light weight,and high production efficiency. PBT's molecular chain structure is similar to PET's. Most of their properties are same,except that molecular main chain becomes four methylene from two. That's why PBT's molecule is more flexible and better processable.
PET is opalescent or bright yellow polymer with high crystalline and glossy surface.Its properties are as follows:good creep-resistance,fatique resistance,and abrasion resistance,high hardness with low abransion wear, best toughness among thermoplastic plastics,good insulating property,little temperature influence,poor corona resistance, non-poisonnous,good weatherability and chemical resistant stability,low water absorption, mild acid and organic solvent-resistance, being unable to endure hot water immersion and resist alkali. PET resin has high glass transition temperature, low crystallization velocity, long molding cycle,large mold shrinkage, and poor dimensional stability. Its crystallized forming is brittle and low heat-resistant.
Through modified by nucleating agent,crystallizing agent and glass fibre reinforcement, PET also has the following characteristics besides owning PBT's properties:
1.Its distortion temperature and long-term use temperature is the highest one among thermoplastic general engineering plastics;
2.Because of its high heat resistance,reinforced PET can soak in tin soldering bath for 10s under the temperature of 250℃, without distortion and discolouring. It's very suitable for making components for tin soldering electronics and electrical appliances.
3. Flexural strength is 200MPa; Modulus of elasticity can reach to 4000MPa;Good creep resistance and fatigue resistance; High surface hardness; Mechanical properties similar to thermosetting plastics.
4. Because glycol used for producing PET is almost at half the price of butanediol used for producing PBT,prices of PET resin and reinforced PET are cheapest in engineering plastics. They have a high cost performance.
ABS resin is currently most productive and widely applied polymer. It organically unify the properties of PS,SAN and BS. It has excellent mechanical properties with balanced toughness,hardness and rigidity. ABS is the terpolymer of acrylonitrile,butadiene and styrene. A represents Acrylonitrile; B represents Butadiene; and S represents Styrene.
Chemical Name: Acrylonitrile-Butadiene-Styrene plastic
English Name: Acrylonitrile Butadiene Styrene plastic
ABS is non-poisonous and odorless. Its appearance is harfway transparent ivory,or transparent particle and powder. Its density is 1.08~1.18g/㎝3. Shrinkage is 0.4%~0.9%. Modulus value of elasticity is 0.2Gpa. Poisson's ratio is 0.394. Hygroscopicity is less than 1%. Melting temperature is 217~237℃. Decomposition temperature is more than 250℃.
ABS has excellent mechanical property. Its impact strength is very good,which allows that it can be used at extremely low temperatures. ABS also has excellent abrasive resistance, good dimensional stability, and oil resistivity, making it suitable for bearings under medium load and rotating speed. The creep resistance of ABS is better than that of PSF and PC, but worse than that of PA and POM. ABS's flexural strength and compressive strength is inferior compared with other plastics. The effect of temperature on its mechanical property is very strong.
Distortion temperature for ABS is 93~118℃. After annealing treatment, it can increase by about 10℃. Under the temperature of -40℃, ABS still can show a certain toughness. It can be used in the temperature range of -40~100℃.
Electrical insulation of ABS is very good, rarely affected by temperature, humidity and frequency. It can be used in most environments.
ABS is not affected by water,inorganic salt,alkali and various acids, but it's soluble in ketone,aldehydes and hydrochloric ether.And if it's eroded by glacial acetic acid and vegetable oil, it can lead to stress cracking phenomenon.ABS's weatherability is very poor. Under the action of ultraviolet light, degradation is easy to happen. And its impact strength will fall by about half if kept outside for half a year.
ABS Molding Technology
We also could say ABS is the modification of polystyrene. It has better impact strength,mechanical strength,and processability than HIPS. It can be used on plastic molding equipment like injection machine,extruder for injection molding,extrusion molding,blow molding,calendering,laminating,foaming,thermal forming, welding, coating, electroplating and machining. ABS has very strong water absorbability, so it need drying treatment before processing. Drying temperature should be 70~85℃,and drying time should be 2~6h. During processing, ABS is easy to generate internal stress. If the stress is too large, it easily makes product crack. So it need annealing treatment, putting product into hot air circulation drying oven for 2~4h under the temperature of 70~80℃ and then cooling to room temperature.
ABS Injection Processing
Injection Molding. ABS is the most common engineering plastics, widely used for making wheel gear,wheel gear,handle,pump impeller,television,computer,typewriter shell, keyboard, electric instruments, accumulator tank, and refrigerator parts, as well as machinery industrial parts, various commodities, and consumer goods packaging. ABS injection molding temperature is between 160~220℃. Injection pressure is between 70~130Mpa. And Mold temperature is between 55~75℃.
ABS Extruding Processing
Extrusion. ABS can be used for products like tubing,plating,sheet,and section bar.Tubing is applied to various section bar,air tube,pipelines for lubricating oil and fuel oil. Plating and sheet are applied to floor board,furniture,tank,filter,interlayer, thermal forming and vacuum forming. The screw length-diameter ratio of extruding machine is usually very high. L/D is between 18~22,and compression ratio is （2.5~3.0）：1. It's better to use gradient type screw with torpedo head. Temperature for feeding cylinder is as follows, for feed hopper,150~160℃; for the front part of feed cylinder,180~190℃. Mould head temperature is 185~195℃. Mould temperature is 180~200℃.Blowing molding temperature can be controlled between 140~180℃.
PP plastics (polypropylene)
PP plastics concept
Molding temperature: 160-220℃
Material Performance: Small density,better than low-pressure polyethylene in intensity and stiffness,hardness and heat resistance. It can be used around the temperature of 100℃. It has great electrical property,high frequency insulativity, without being affected by humidity. However,at low temperatures, it's fragile and not abrasion resistant, prone to aging.It's suitable for making general mechanical parts, corrosion resistant parts and insulation parts.
1. Crystalline materials; low water absorbency;being prone to melt fracture, being easy to decompose if touching heated metal for a long time.
2. Good flowability; large shrinkage range and shrinkage value; easy to have sinkhole,sink mark and deformation.
3. Fast cooling speed. Gating system and cooling system should have a slow heat dissipation. And pay attention to the molding temperature control. The direction for place with low material temperature is perceptible, especially when low temperature and high pressure.If mould temperature is lower than 50℃, plastic parts are easy to be rough and have marks because of poor welding. If the temperature is higher than 90℃,buckling deformation will be easy to occur.
4. Try to make material's thickness uniform and avoid lacks of plastics and sharp corners, in case of stress concentration.
Easy to be decomposed under specific conditions
Common Products: basin, bucket, furniture, thin film, woven bag, cap, auto bumper and etc.
Polypropylene also includes copolymer of propylene and a little ethylene. PP granule is cylindrical particles with natural color. The particles are smooth and clean. Their sizes are 2mm～5mm in any direction, odorless, non-poisonous and no mechanical impurities. It uses high purity propylene as main raw material and ethylene as comonomer, and adopts highly active catalyst under the temperature of 62℃～80℃ and the pressure less than 4.0MPa to produce polypropylene powder via gaseous phase reaction. Then after drying, mixing, extruding, prilling, sieving and homogenizing, polypropylene powder will become polypropylene particles.
With density of 0.90 g/cm3～0.91g/cm3, it's the lightest one in general plastics. Polypropylene resin has excellent mechanical property and thermal endurance properties. Its usage temperature range is -30℃～140℃. At the same time, it also has excellent electrical insulation property and chemical stability. It's almost not bibulous and doesn't take effect with most chemicals. This material is corrosion resisting, and its tensile strength is 30MPa. Its intensity,rigidity,and transparency are all better than polyethylene. Its shortcomings are low-temperature impact resistance performance and prone to aging. But they can be overcomed via making modification and adding antioxidant. Touching fuming sulphuric acid,fuming nitric acid,chromic acid,halogen,benzene,carbon tetrachloride and chloroform, it will be corroded.It can be used as engineering plastics, applied to make television, radio shell, insulating material for electrical apparatus, antiseptic pipeline,plate and storage tank.It also can be used for producing ribbonfil, fibre and packaging film.
Auto Industry (mainly use PP with metallic addition:Mud Guard,Vent Pipe,Electric Fan,etc.),Apparatus (Dishwasher Door Gasket,Drying Machine Ventilation Tube,Washing Machine Frame and Cover, Refrigerator Door Gasket,etc.) Daily Consumer Goods (Lawn and Garden Equipment like lawn mower and sprayer)
Injection Molding Process Conditions:
Drying Treatment: No need under appropriate storage
Melting Temperature:220~275℃, never exceed 275℃
Mold Temperature: 40~80℃.Suggest using 50℃. Crystalline degree depends on mold temperature.
Injection Pressure: can reach to 1800bar
Injection Speed: Usually, high speed injection molding can minimize internal pressure. If there are defects on product surface, then choose low speed injection molding under high temperature.
Runner and Gate: for cold runner, common runner diameter is 4~7mm. Suggest to use the sprue and runner with whole round body.All gate methods are workable.Common gate diameter is 1~1.5mm,but it also gets access to the gate with diameter of 0.7mm. For edge gate, the minimum of gate depth should be half the thickness.And the minimum of gate width should be no less than twice the thickness.Product with PP material can completely use hot runner system.