Abstract: plastic modification is to general resin through the physical, chemical and mechanical methods, to improve or increase its functionality, in electricity, magnetism, light, heat, aging resistant, flame retardant, mechanical performance, etc to use the function of the special environment conditions.
"Plastic modification", "modified plastics etc. These words are often" we hang in the mouth, so, what is plastic modification, change of is what? Small make up to grilled steak!
What is a plastic modification?
Plastic modification is to general resin through the physical, chemical and mechanical methods, to improve or increase its functionality, in electricity, magnetism, light, heat, aging resistant, flame retardant, mechanical performance, etc to use the function of the special environment conditions. From the raw material production to a variety of specifications and varieties of the resin modified plastic masterbatch, in order to reduce the cost of plastic products, improve its functionality, there are plastic modification technology.
Plastic modification method have?
Mention plastic modification, a lot of people will think of filling, blending, fiber reinforced, etc., but few people very comprehensive understanding of plastic modification method. In fact, the plastic modification method has the following kinds:
1, add modification
(1) adding inorganic or organic small molecule
Add small molecules in polymer (resin) inorganic or organic material, through physical or chemical effect, in order to obtain some expected performance of a modified method. This method is one of the first modification methods, modification effect is obvious, it is simple process, low cost, and therefore is widely applied. Believe in colleges and universities have done graduation project contact and understand it.
This modified method according to the modified purpose can be divided into lower costs (add all kinds of cheap inorganic and organic fillers), improving strength (add various reinforced fiber), improving toughness (add elastomer and superfine packing, etc.), improve the flame retardancy (add metal oxides, metal hydroxide, inorganic phosphorus and organic halide, organophosphorus compound, organic silicon and nitride, etc.), improve the life (add various antioxidants, light stabilizer, etc.), machinability (adding plasticizer, heat stabilizer and lubricant and processing AIDS, etc.), increase the wear resistance (adding graphite, MoS2, SiO2, etc.), improving the structure of the crystal (adding nucleating agent, a specific organic carboxylic acid, sorbitol, etc.), to improve the antistatic and conductive (adding antistatic agent and the conductive agent), to improve the biodegradable (degradation starch filling, additive, etc.), improving the radiation resistance, etc.
This method commonly used additives are: inorganic additives (filling agent, strengthening agent, flame retardant, stain and nucleating agent, etc.), organic additives (organic tin stabilizer, antioxidant, plasticizer, and organic flame retardant, degradable additive, etc.).
(2) adding high polymer material
This method also be blending modification, the main method is in a resin mixed with one or more other resin (including plastic and rubber), so as to change the original resin performance. Due to the blending modification for polymer material in the complex system, so it has very good compatibility to add small molecular system, modification to the original at the same time will not much affect other properties of the resin. Our common polymer alloy is that this method is modified. Blending modification is a development of new polymer materials is the most effective way, and to realize high-performance plastic varieties, intensification of existing main way.
2, morphology and structure modification
This method is mainly for plastic resin to form and structure modification of itself. Usual method is to change the plastic state of crystal type, crosslinking, copolymerization, grafting, etc.
(1) control of modified form
Modified plastic shape control is control plastic products of different aggregation form, to achieve our desired performance. This method is under the effect of the external force, by means of adjustment for machining molding process, shape control, generally called self modification, of which the enhancement is the most commonly used. Through control can improve the performance of many on the plastic, plastic form various aspects, such as mechanical, thermal, optical, some aspects of the modification effect is very obvious. For example, by the quality of the nuclear technology control crystallization, using two-way stretch to obtain highly orientation.
(2) crosslinking modification
Crosslinking should be very familiar with, generally for the linear structure/network it mesh structure or three-dimensional structure. Crosslinking is need outside conditions, usually for different forms of energy (such as light, heat, radiation, etc.). Macromolecular chain due to external effect can free radicals reaction or functional groups, so as to form new chemical bonds between the macromolecular chains, make linear polymer structure form different degree of polymer network structure. For example the crosslinking modification of polypropylene can improve its mechanical properties.
(3) graft copolymerization and modification
This method is mainly on the original chain combined with other molecular chain segments or functional groups. Copolymerization refers to two or more monomer polymerization of, can extend polymer performance, is the important way of improving the performance of polymer and USES. Such as polystyrene and acrylonitrile copolymer improve polystyrene brittle weakness; Polyvinyl chloride (PVC) with vinyl acetate copolymerization improve PVC plastic. Grafted with graft chain transfer, chemical grafting, radiation grafting, the modification on the rigid body and elastomer application more, such as styrene - butadiene graft copolymer improve the impact properties of PS.
3, composite modified
Such as plastic composite modified by adhesive or hot melt method will be more than two layer or two layers of materials such as films and sheeting composite together and form a multilayer film, sheet material such as method. Plastic composite modification is actually plastic blending modification method of middle shape blending extremes, can also be seen as a special kind of plastic blending modification.
4, the surface modification
Plastic surface modification means by physical or chemical methods to make plastic products surface properties change of modification methods. Plastic surface modification and other modified difference has two points: one is the modified only confined to the surface of the product, its internal performance does not change; The second is the modification of implementation in plastic products after processing, belongs to secondary processing and modification.
Main aim of the plastic surface modification can be divided into two categories: one is direct application of modified, another kind is the indirect application of modified.
(1) the direct application of direct application of modified plastic surface modification means can direct access to the application of some modification, the specific surface gloss, surface hardness, surface wear resistance and the frictional surface, surface aging proof, flame retardant, cut off the surface conduction and surface. Plastic surface modification on this application development quickly in recent years, such as cut off in the plastic modification, surface blocking modification occupies very important position.
(2) indirect application of plastic modification refers to the surface modification of indirect application for direct application of ground modification, some of the specific, such as to improve the adhesion of plastic, such as printing and stratification and to improve the surface tension of plastic modification. For example, plastic plating, for example, without the surface treatment of plastic varieties only ABS plating fastness can meet the requirements; Especially polyolefins plastics varieties, plating fastness is very low, the combination of surface modification must be conducted to improve and plating fastness, before plating processing.
What is modified to change the sex?
Plastic modification has its purpose, and the purpose of each demand modification methods have different use. Here are several kinds of commonly encountered modification requirements and their use of the method.
1, change the density of plastic
(1) reduce the density of the plastic
Said lower density may you know, but another way you will understand: let plastic lighter. To reduce the density of plastic foam modified, add light three kinds of fillers and blending light resin. Plastic foam molding is the most effective way to reduce the density. And add light to add material and blending light resin two modification methods, only lower density, slowly drop, generally only about 50%, the lowest relative density can only be reached 0.5 or so. The density of the foam products range is very wide fan, lowest relative density can reach 10-3.
(2) improve the density of plastic
Increase the density of plastic is to make the original resin, a method of the relative density increases, mainly for the added to mass packing and blending heavy resin. Added to mass packing method to improve the density of plastic packing with metal powder, the main heavy mineral filler; Increase the density of plastic blending heavy resin, this method improve the amplitude is small, generally top only about 50%. Mainly suitable for some light weight resin such as PE, PP, PS, EVA, PA1010 and PPO, etc. Often join heavy resin: PTFE, FEP, PPS, POM, etc.
2, plastic transparency of improvement
About the transparency of plastic, is introduced in the previous article, here only a brief introduction. Improve plastic transparency principle is to use the crystal's relationship with transparency. Transparency of plastic and its products to the size of the size of the crystallinity and crystalline structure, by controlling the products of different morphological structure, can improve its transparency.
Measure the transparency of a material is good or bad, there are a number of performance indicators are to consider. The commonly used indicators are: light transmittance, haze, refractive index and birefringence and dispersion, etc. In the above indexes, light transmittance and fog degree two main characterization of pervious to light quality indicators, and the index of refraction, double refraction and dispersion three indicators are mainly used for characterization of the pervious to light quality. A kind of good transparency material, requirements with these performance indicators and balanced.
Change the crystal type methods are:
1) crystal quality control, such as crystal shape, the regularity of the spherulite content, crystal size and crystal control;
(2) improve the index of refraction, mainly by joining does not affect the transparency high refractive index of organic matter or inorganic matter to raise;
(3) to reduce the birefringence can be through orientation in the process of control, namely reduce orientation degree and achieve the goal that reduce birefringence.
(4) add to improve transparency of plastic, it is to point to in a transparent resin with small molecular substances, so as to improve the transparency of the approach. Using this method can improve the light transmittance, refractive index, reduce birefringence.
(5) adding nucleating agent, is increasing the transparent resin light transmittance one of the most effective method. Nucleating agent is a kind of can promote the crystallization of small molecules. It can have the effect of crystal nucleus in the resin, make original all other nuclear heterogeneous nucleation, increase the crystallization system within the number of crystal nucleus, multiply the number of crystallite, reduced Numbers of spherulite, so that the crystal size and transparency of the resin.
6. Add the high refractive index inorganic matter
All landowners added to reduce the birefringence of the material
End up adding anti mist
3, plastic hardness and flexibility of improvement
(1) add to improve the hardness of plastic refers to the plastic hard additive is added to a modification method. Commonly used hardness add agent for rigid inorganic filler and fiber.
(2) the surface of the plastic hardness improved method is to point to improve the hardness of plastic products appearance, only the constant within the hardness of products. This is a low cost of hardness improvement methods. This modified method is mainly used for shell, decorative materials, optical materials and daily necessities, etc. This modified method mainly includes three kinds of coating, coating and surface treatment methods.
(3) blend and compound to improve the hardness of plastic: (1) plastic blending method that is in the low hardness resin does does mix high hardness resin, in order to improve its overall hardness. Common blending resin are: PS, ABS, PMMA and MF, need modification of PTFE resin mainly for PE, PA, and PP, etc. (2) the method to improve plastic composite hardness that is on the low hardness plastic products surface composite layer hardness resin. This method is suitable for extrusion products, such as plate, sheet, film and pipes, etc. The commonly used composite resin such as PS, ABS, PMMA and MF.
(4) adding plasticizer to improve plastic flexible: the main purpose of the plasticizer is to improve the processability of the resin, the lower processing temperature, improve the processing of liquidity. But its join the related resin, can also give flexible to products. Applicable to the plasticizers to improve flexibility of resin: PVC, PVDC, CPE, SBS, PA, ABS, PVA and chlorinated polyether and so on.
4, plastic processing and performance improvement
Plastic processing is made of plastic raw materials (resin) + additives into a process of a certain intensity of products. Thermoplastic resins and the changes in the manufacturing process of thermosetting resin its different. Improve plastics processing performance are mainly concentrated in: to improve the thermal decomposition temperature of resin; Reduce the melting temperature of the resin; To improve the resin processing liquidity; Improve the melt properties of the resin. Commonly used modification method is to add modification, adding plasticizer and lubricant. Plasticizer can improve the plastic polymers; Between lubricant is to reduce the material and the friction force on the surface of the material and processing equipment, from the surface reduce the flow resistance of the melt, reduce the melt viscosity, increase of melt flow, avoid the melt adhesive with equipment, improve the surface of products, etc.
5, plastic
Plastic enhancement is usually added reinforcing fillers and fibers. Most of the conventional fillers added to the resin directly, will cause the plastic tensile strength decreased. But some after nailing on the surface of a temporary or directly add special packing not only does not cause the decline of the tensile strength, it will improve the tensile strength to some extent, we call this kind of packing for reinforcing filler. Reinforcing reinforced fill reinforcing fiber are far less, only can be used for some strength requirement is not too high. Add fiber reinforced plastic method is the most commonly used and effective enhancement method. Enhanced with fibre materials is one of the main plastic with reinforced material, its dosage can account for more than 90% of the whole reinforced material. Increased with fibre materials including fiber and two categories, the specific varieties are: inorganic class (such as glass fiber, asbestos fiber, carbon fiber, whisker, quartz fiber, graphite fiber and ceramic fiber, etc.), organic type, such as PAN fiber, polyethylene fiber, PA, PC, PVC fiber and polyester fiber, etc.), metals (such as calcium boron fiber and aluminum, titanium, metal whisker, etc.).
6, plastics toughening
Plastic toughening usually blending elastomer material, elastomer toughening materials commonly used are: high impact resin, such as CPE, MBS, ACR, SBS, ABS, EVA, modified petroleum resin (MPR), etc.; High impact rubber, such as ethylene propylene rubber (EPR), EPDM (EPDM), nitrile rubber (NBR), styrene butadiene rubber, natural rubber, polybutadience rubber, neoprene, polyisobutylene and butadiene rubber, etc.
7, plastic thermal properties and flame retardant performance improvements
Affect the thermal performance of a plastic products used primarily for heat resistant temperature and low temperature resistant temperature. Main available heat temperature heat distortion temperature, Martin heat resistance temperature and vicat softening point; Generally available brittle temperature and low temperature resistant temperature. Of (among) all the packing, in addition to the organic filler, most of the inorganic mineral filler can obviously improve the plastic heat temperature. The commonly used heat packing: calcium carbonate, talc, mica, wollastonite, calcined clay, bauxite and asbestos, etc. For example, the highest temperature can reach 1000 degrees Celsius, mica filler in the heat resistant modification is the most effective. In addition, plastic enhance change effect than fill good heat resistance, this is mainly because most of the fiber heat temperature is very high, melting point are more than 1500 degrees Celsius. The commonly used heat resistant fiber mainly include: asbestos fiber, glass fiber, carbon fiber, whisker, polyamide fiber and acrylic fiber, etc.
Most of the flame retardant plastic is not very good, you need to add flame retardant plastic formula. It is a kind of flame retardant, which can prevent ignition or inhibit the spread of flame of plastic additives. In addition, you also need to add smoke suppression agent auxiliary day.
8, plastic cost reduction
Reduce the cost of plastic has always been the pursuit of manufacturers, so will some modification method is used to reduce the cost. The main method of adding fillers, blending cheap resins. Hope suppliers to reduce costs at the same time, of course, don't forget the needs of the performance.
Plastic modified is above these content, specific modification process is very complex, on the one hand is cost benefit restriction, on the other hand is the needs of customers, many modification methods need to achieve.
