INDEX 1. BASIC INFORMATION 2. PLASTIC PROPERTIES 3. HOW TO CLASSIFY: THERMOSETTING AND THERMOPLASTIC 4. ELABORATED PROCESS: BLENCH, SLIM, CALLENDER AND MOULDING 5. PLASTIC RECICLYING
PLASTIC´S ORIGIN Plastics Plastics are man-made materials. Plastics have taken the place of traditional materials like woods and metals. Plastics differ from other materials largely because of the size of their molecules. Most materials have molecules made up of less than 300 atoms, plastics contain thousands of atoms. We call them Macromolecules. Some plastics are derived from natural substances such as animals, insects and plants but most are man-made. These are named Synthetic Plastics. Most synthetic plastics come from crude oil but coal and natural gas is also used. When crude oil is refined gasses are given off . The gasses are broken down into Monomers. These are chemical substances consisting of a single molecule. Thousands of these are linked together in a process called Polymerisation to form new compounds called Polymers.
BASIC INFORMATION WHAT IS PLASTIC? Plastics are materials formed by long chains of carbon and hydrogen called polymers, formed by units called monomers. the most important characteristic of plastic is the capacity of deformation WHAT ARE THEY MADE OF? They are made of: · Crude oil · Natural origins: rubber or cellulose
PLASTICS PROPERTIES · DEFORMING CAPACITY: it means that other materials like iron can't deformate so easy as plastic because plastic has more flexibility than iron (i.e.) · LIGHTNESS: it means that it weighs less than other materials for example, plastic is lighter than the iron or steel (Low Density) · INSULATING: it is divided into termical and electrical insulation: · TERMICAL: it resists very well the heat so for example the shield of a computer has to bear very high temperatures · ELECTRICAL: it protects the electric cables core (Electroshock)
PLASTIC PROPERTIES · MECANIC RESISTANCE: it means that it does not break easily if it falls down to the floor or crash with something, like other materials, for example glass. · ATMOSPHERIC RESISTANCE : it resist very well at the humidity and the high and low temperatures. for that reason, objects at the outside are painted, because the paint is a plastic in a liquid state. . GOOD SURFACE FINISH: This material offers a very good surface finish.
HOW TO CLASSIFY: THERMOPLASTICS · THERMOPLASTICS are those that can be melted many times. · CELLULOSICS THERMOPLASTICS: they are divided into: · cellulose acetate · etil cellulose · PETROLEUM THEMOPLASTICS. they are divided into : · polyethylene · pvc (polyvinyl chloride) · polymethyl methacrylate (Acrylic) · polystyrene (expanded) · polypropylene · polyamides
HOW TO CLASSIFY: THERMOSETTING THERMOSETTINGS are the ones that only can be melted once. · PHEONELIC RESIN are also known as bakelite for example: the kitchen utensils handles are made with bakelite · MELAMINE is used, for example, to cover sheets of wood. · POLYESTERS. The majority of the clothes have, at least, a little percentage of polyester . SKETCH ·
ELABORATED PROCESS THERE ARE MANY ELABORATED PROCESS TO WORK WITH THE PLASTICS. THE MOST IMPORTANT ONES ARE: · BLENCH · SKIM · CALLENDER · MOULDING
BLENCH BLENCH consist on spilling the melted plastics into a mold, when the plastic become colder it takes the shape The mold could be from pieces like plaster, wood or different metals.
SKIM THE SKIM consist of inject air or gas into a plastic mass to form bubbles in order to make it lighter. for example: mattresses, bike helmets, sponges...
CALLENDER CALLENDER consist on passing the plastic through rollers called callenders until it becomes thin sheets for example: to make awnings, folders...
MOULDING MOULDING consists on giving shape to the plastics. They introduce it into a mold by pressure. Moulding is divided in two groups: HIGH PRESSURE AND LOW PRESSURE HIGH PRESSURE: · COMPRESSION: the plastic is heated between the two parts that compound the mould and is compressed with a hydraulic press. for example: kitchen utensils
MOULDING · INJECTION: the granulated plastic is introduced into a cylinder and when it is heated, a screw push it and inject it at a high pressure into a steel mould for example: cars compounds, buckets... · EXTRUSION: is similar to the injection but instead of a mould, it uses a nozzle of different shapes to make pieces. for example: bars
MOULDING LOW PRESSURE: This is used to give shape to the plastic sheets by the application of low heat and pressures in order to adapt it into a mold basically by two ways: · MOULD AT A LOW PRESSURE: consist on absorbing the air between the mold and the warm sheet to adapt to the shape of the mold. for example: food containers · MOULD AT A LOW PRESSURE BY BLOWING: consist of apply air at a pressure against the plastic sheet until it is adapted to a warm mold . for example: bottles and hollow pieces. Blow Moulding Video
MOULDING THE ROTATIONAL MOULDING consist on moving slowly a mould that has plastic inside. The centrifuge force plus heat, make the plastic sticks on the walls of the mould, taking the shape of the object that we like to make. is especially used in objects of big size, for example: bins, canoes, traffic cones… Video Rotational
PLASTIC RECYCLING RECYCLING IS TO COLLECT AND TO TRANSFORM THE MATERIALS THAT HAS BEEN REFUSED INTO USEFUL PRODUCTS. THERE ARE FOUR TYPES OF RECYCLING: · THE PRIMARY RECYCLING: it consist on transforming the plastic refuses in plastics with the same properties of the original materials. · THE SECONDARY RECYCLING: It lets us recover the thermosetting or contaminated plastics, plastics with lower properties than the original ones.
PLASTIC RECYCLING · TERTIARY RECYCLING breaks down the plastic in chemical and fuel compounds. · THE QUATERNARY RECYCLING consist on burning the plastic in order to use the heat that it produces like energetic source. It costs too much and it produces gases. We produce 20 times more plastic today than we did 50 years ago!