Plastics have replaced wood, paper, glass, steel, and aluminum as the materials of choice for many common objects used today. They usually have interior mechanical properties such as stiffness, strength, and temperature resistance to the materials they have replaced. However, plastics succeed because of their low density, toughness, and design flexibility. Much of this design flexibility is due to the manufacturing processes that have been developed to shape them into simple and complex forms that would be costly or even impossible to produce with traditional materials.Moulding processes have been around for a long time and are particularly suited to making plastic parts. Most of the processes can efficiently produce plastic parts in high numbers, but even where low numbers are involved, the complexity of the required shape may reduce the cost of moulding a part in plastic over machining a part from metals.Plastics production really started in the mid-20th century. Today there are hundreds of different plastics available, each one developed to have specific characteristics to meet the requirements of different users. The list of plastics appears to be endless but they fall into two categories, thermoplastics and thermosets. Thermoplastics can be melted and recycled into new parts. Thermosets are stronger than thermoplastics but cannot be recycled into new parts and have to be disposed of in other ways. Because plastics are not naturally biodegradable and not all plastics can be recycled, there is a real problem in disposing of plastic waste.To help answer this concern, bioplastics are being developed from plant materials. It is possible to produce a mouldable “plastic” with ground-up natural cellulose, other materials, and water. Drug capsules are made from starch-based bioplastics.Summary:Plastics are used for many common objects because they are strong, stiff and have (1) to temperature. The design flexibility of plastic makes it easy to be shaped into simple and complex forms, which is more expensive or impossible to manufacture with other (2) . Moulding process is a suitable method for making plastic parts. The cost of moulding a part in plastic is cheaper than one in (3) . Plastics are divided into two (4) . Thermoplastics can be heated and recycled into new parts but thermosets have to be disposed of in other ways. To solve the problem of disposing of plastic waste (5), are produced from plant materials. Drug capsules are made from this material.

Plastics (will give) additional characteristics such as fire retardancy to allow them to be used in aircraft parts in the future. Injection-moulded parts (may include) glass or carbon fibres for strength. Plastics (can mould) with a foaming agent which (will reduce) the density and hence the weight of the final component and reduce the material required so reducing the cost. The list of plastics appears to be endless but they fall into two categories, thermoplastics and thermosets. Thermoplastics (can melt and recycle) into new parts. Thermoset plastics are stronger than thermoplastics but (cannot recycle) into new parts and have to be disposed of in other ways.

Oil and natural gas are the main raw materials which (can use) in the production of plastics.Plastics (will use) in the production of a wide range of household appliances.The car industry (may use) high-precision components in their vehicles.The majority of plastic parts (could not manufacture) using injection molding many years ago.Manufacturers (could not make) make plastics to a high standard of quality before they started to use oil.Soon plastics (will make) from any kind of plant material.

Read the text below about plastic and complete the text using the active or passive form of the verbs and modal verbs in brackets. One gap can be filled with the active or passive of the verb.Plastics (will give) additional characteristics such as fire retardancy to allow them to be used in aircraft parts in the future. Injection-moulded parts (may include) glass or carbon fibres for strength. Plastics (can mould) with a foaming agent which (will reduce) the density and hence the weight of the final component and reduce the material required so reducing the cost. The list of plastics appears to be endless but they fall into two categories, thermoplastics and thermosets. Thermoplastics (can melt and recycle) into new parts. Thermoset plastics are stronger than thermoplastics but (cannot recycle) into new parts and have to be disposed of in other ways.

Read the text about problems and solutions for plastic moulding and fill in each blank with NO MORE THAN TWO WORDS from the textPlastic Injection Molding Problems And SolutionsThe advantages of plastic injection molding for manufacturing parts methods include fast production speed, high efficiency, automation of operation, shapes, and size flexibility. Moreover, the injection molding products are accurate in size, easy to be replaced, and the mold parts can be formed into complex shapes. This eco-friendly method is suitable for the molding processing fields such as mass production and complex shape products.However, although the operators are familiar with specific machines and the operational skills in the molding process of plastic parts, the various rapid injection molding defects on mold design and materials are inevitable. The article aims to plastic injection molding problems and solutions, mainly as follows:Short ShotsShort shots are a phenomenon in which the mold cavity cannot be completely filled.Causes:- Die temperature, material temperature or injection pressure and speed are too low- Uneven plasticization of raw materials- Poor exhaust- Insufficient liquidity of raw materials- The part is too thin or the gate size is too small- Polymer melt is prematurely cured due to unreasonable structural designRemedies:Material: Use more fluid materialsMold design:- Fill the thick wall before filling the thin wall to avoid the retention phenomenon.- Appropriately increase the number of gates and runner size to reduce the process ratio and flow resistance- The position and size of the exhaust port should be properly set to avoid the phenomenon of the poor exhaust.Machine:- Check whether the check valve and the inner wall of the material cylinder are seriously worn- Check if the feeding port has material or whether it is bridged.Air TrapsAir traps is that air is trapped in the cavity to create bubbles in the part.Causes: It is caused by the air being unable to escape from the parting surface, the ram, or the vent when the two melt fronts meet.Remedies:- Structural design: Reduce thickness inconsistency and try to ensure uniform wall thickness- Mold design: (1) Add a vent at the last filled place (2) Redesign the gate and runner systemBrittlenessBrittleness is that the plastic part is easily cracked or broken in some placeCauses:- Dry conditions are not suitable; use excessive recycled materials- Injection temperature setting is wrong- The gate and runner system settings are not appropriate- The melting mark strength is not highRemedies:Material:- Set appropriate drying conditions before injection molding- Reduce the use of recycled materials and increase the proportion of raw materials.- Use high-strength plastic.Mold design: Increase the size of the main runner, branch runner, and gateMachine: Choose a well-designed screw to make the temperature distribution more uniform during plasticization- (1) molding is an eco-friendly method, which is reasonable for bulk production and complex shape products.- Three main problems of this process are short shots, air trap and (2) .- Short shots can caused by many reasons such as uneven plasticization and insufficient liquidity of (3) , insufficient exhaust , too thin part or small (4) , or the melting of polymer.- (5) happens when the air cannot be escaped from the parting surface, the ram, or the vent when the two melt fronts meet. This can be prevented by testing the (6) and (7) design.- The plastic part can easily (8) or broken in some place, it is because of unsuitable condition, injection temperature, in appropriate gate and runner system settings, or low (9) mark strength.

State two things you must consider when designing a mould for a thermoset plastic