Plastic

Plastic introduction

Plastics is a synthetic polymer{polymer}, also commonly known as plastics or resin, and can freely change body styles. It is a material formed by the synthesis or condensation of monomer raw materials. It consists of synthetic resins and additives such as fillers,plasticizers , stabilizers, lubricants, and colorants.

Plastic classification

According to the different characteristics of plastic, plastic is usually pided into general plastic, engineering plastic and special plastic three types.

① General plastics

Generally refers to the production of large, widely used,good molding, cheap plastic. There are five major varieties of universal plastics, namely polyethylene(PE), polypropylene(PP), polyvinyl chloride(PVC), polystyrene(PS) and acrylonitrile butadiene styrene copolymer(ABS). They're all thermoplastics.

② Engineering plastics

Generally refers to the ability to withstand certain external forces, with good mechanical properties and resistance to high, low temperature performance, dimensional stability is good, can be used as an engineering structure of plastics, such as polyamide, polysulfone and so on.

③ Special plastics

Generally refers to plastics that have special functions and can be used in special applications such as aviation and aerospace. For example, fluorine plastics and organosilicon have outstanding special functions such as high temperature resistance and self-lubrication, and reinforced plastics and foams have special properties such as high strength and high buffer. These plastics belong to the category of special plastics.

Plastic composition

The plastic we usually use is not a pure substance. It is made of many materials. Polymer polymer (or synthetic resin) is the main component of plastics. In addition, in order to improve the performance of plastics, various auxiliary materials such as fillers, plasticizers, lubricants, stabilizers and colorants should be added to the polymer to make it a good plastics.

① Synthetic resin

Synthetic resin is the main component of plastics, and its content in plastics is generally between 40% and 100%. Resin is often regarded as a synonym of plastics because of its high content and the nature of resins often determines the nature of plastics. For example, polyvinyl chloride resin and polyvinyl chloride plastics, phenolic resin and phenolic plastics are mixed together. In fact, resin and plastic are two different concepts. Resin is an unprocessed raw polymer. It is not only used to make plastics, but also used as raw materials for coatings, adhesives and synthetic fibers. In addition to a very small part of plastics containing 100% resin, the vast majority of plastics, in addition to the main component resin, also need to add other substances.

② Filler

The filler, also known as the filler, can increase the strength and heat resistance of the plastic and reduce the cost. For example, adding wood powder to phenolic resins can greatly reduce costs, make phenolic plastics one of the cheap plastics, and at the same time significantly increase mechanical strength. Filling can be pided into organic fillers and inorganic fillers, the former such as wood powder, rags, paper and various fabric fibers, the latter such as glass fiber, diatomite, asbestos, carbon black and so on.

③ Plasticizer

Plasticizer can increase plasticity and softness of plastics, reduce brittleness, and make plastics easy to process. Plasticizers are generally high boiling point organic compounds which can be miscible with resins, non-toxic, odorless, light and heat stable. Phthalate esters are commonly used. For example, when producing polyvinyl chloride plastics, soft polyvinyl chloride plastics can be added if more plasticizers are added, if no plasticizers are added or less(dosage < 10%), get hard PVC plastic.

④ Stabilizer

In order to prevent synthetic resin in the process of processing and use by the role of light and heat decomposition and damage, extend the service life, to add stabilizer in the plastic. Commonly used stearate, epoxy resin, etc.

⑤ Colouring agent

Colouring agents can make plastic have a variety of bright, beautiful colors. Organic dyes and inorganic pigments are commonly used as colorants.

⑥ Lubricant

The function of lubricant is to prevent the plastic from sticking to the metal mold when forming, and to make the plastic surface smooth and beautiful. Commonly used lubricants are stearic acid and its calcium magnesium salt.

⑦ Antioxidant

To prevent the plastic from being heated and oxidized during heating molding or high temperature use, causing the plastic to turn yellow, crack, etc.

In addition to the above-mentioned additives, flame retardants, foaming agents, anti-static agents, etc. can also be added to the plastic to meet different requirements for use.

Plastic screening

① Screening of raw materials: such as polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS) and a acrylonitrile butadiene styrene copolymer (ABS), because the particles in the production are qualitative and uniform, their purpose of screening is to remove impurities and agglomerations.

② Waste plastic recycling screening: formed plastic products for recycling, for example: waste plastic pipes, waste plastic brackets, waste plastic bottles, etc., through the broken screening.

③ Screening of plastic particles: plastic particles after molding for classification, the purpose of screening is fine classification.

④ Screening of resin sections: it is difficult to screen, because the resin sections are easy to bond, and there will be a single body of super-long unqualified material, you can try to determine the screening requirements.

⑤ Screening of filler: screening of wood powder, glass fiber, diatomite, natural mineral powder, carbon black, etc.