RECYCLING PLASTICS
Plastics – what are they and how do they behave?
Plastics are organic polymeric materials consisting of giant organic molecules. Plastic
materials can be formed into shapes by one of a variety of processes, such as extrusion,
moulding, casting or spinning. Modern plastics (or polymers) possess a number of extremely
desirable characteristics; high strength to weight ratio, excellent thermal properties, electrical
insulation, resistance to acids, alkalis and solvents, to name but a few.
These polymers are made of a series of repeating units known as monomers. The structure
and degree of polymerisation of a given polymer determine its characteristics. Linear
polymers (a single linear chain of monomers) and branched polymers (linear with side
chains) are thermoplastic, that is they soften when heated. Cross-linked polymers (two or
more chains joined by side chains) are thermosetting, that is, they harden when heated.
Figure 1: Polymer structures
Thermoplastics make up 80% of the plastics produced today. Examples of thermoplastics
include;
• high density polyethylene (HDPE) used in piping, automotive fuel tanks, bottles, toys,
• low density polyethylene (LDPE) used in plastic bags, cling film, flexible containers;
• polyethylene terephthalate (PET) used in bottles, carpets and food packaging;
• polypropylene (PP) used in food containers, battery cases, bottle crates, automotive
parts and fibres;
• polystyrene (PS) used in dairy product containers, tape cassettes, cups and plates;
• polyvinyl chloride (PVC) used in window frames, flooring, bottles, packaging film, cable
insulation, credit cards and medical products.
There are hundreds of types of thermoplastic polymer, and new variations are regularly
being developed. In developing countries the number of plastics in common use, however,
tends to be much lower.
Thermosets make up the remaining 20% of plastics produced. They are hardened by curing
and cannot be re-melted or re-moulded and are therefore difficult to recycle. They are
sometimes ground and used as a filler material. They include: polyurethane (PU) –
coatings, finishes, gears, diaphragms, cushions, mattresses and car seats; epoxy –
adhesives, sports equipment, electrical and automotive equipment; phenolics – ovens,
handles for cutlery, automotive parts and circuit boards (The World Resource Foundation).
Nowadays, the raw materials for plastics come mainly from petrochemicals, although
originally plastics were derived from cellulose, the basic material of all plant life.
Linear Polymer Branched Polymer Cross-linked Polymer
Recycling of Plastics Practical Action
參考答案:塑料回收塑料-怎么就是他们要如何做? 塑料是有机高分子材料组成的巨型有机分子. 塑胶原料可形成各种形状的过程之一,如挤出成型、 铸造或考场. 现代塑料(或聚合物)具有多项特色极不可取; 高强度重量比,热性能优异, 电气绝缘、耐酸、碱、溶剂,等等. 这些聚合物制成一系列重复单位称为单体. 结构与某一程度的聚合高分子确定其特征. 线性聚合物(单一线性链单体)和枝状聚合物(直线与侧链)热塑, 这是他们在激烈的软化. 交联聚合物(由两个或两个以上的连锁店加入侧链)热固性,即他们在激烈板结. 图1:高分子结构占80%的热塑性塑料制作. 热塑性塑料包括例子; ●用高密度聚乙烯(HDPE)管道、汽车油箱、瓶子、玩具、 ●低密度聚乙烯(LDPE)使用塑料袋,抱着电影、灵活器皿; ●用聚酯瓶(宠物)、地毯、食品包装; ●聚丙烯(PP)使用的餐具,广管局 陶器案件瓶箱、汽车零部件、纤维; ●聚苯乙烯(PS)用于乳制品容器,录音带盒、铜 聚苯乙烯和名牌; ●聚氯乙烯(PVC)用于窗框、地板、瓶子、包装薄膜、电缆绝缘、铬 编辑卡及医疗产品. 有数百种热塑性聚合物、新变化,经常被开发. 在发展中国家的一些常用塑料,但往往会大大降低. 其余20%弥补热固性塑料制作. 他们是被固化和硬化不能再熔化或重新塑造,因此也很难再用. 他们有时地上用作填充材料. 它们包括:聚氨酯(浦)--涂料、饰面、齿轮、隔板、座垫、床垫、汽车座位; 环氧胶粘剂、体育器材、 电动汽车和设备; 酚醛塑料-烘炉、扶手餐具、汽车零部件、电路板(世界资源基金会). 现在,塑料原料主要来自石化、塑胶虽然原本来自纤维素、 所有植物生命的基本物质. 线性高分子聚合物支交联聚合物回收塑料实际行动
