1. What is a polymer processing aid? What is its function?
Answer: Additives are various auxiliary chemicals that need to be added to certain materials and products in the production or processing process to improve production processes and enhance product performance. In the process of processing resins and raw rubber into plastic and rubber products, various auxiliary chemicals are needed.
Function: ① Improve the process performance of polymers, optimize processing conditions, and submit processing efficiency; ② Improve the performance of products, enhance their value and lifespan.
2.What is the compatibility between additives and polymers? What is the meaning of spraying and sweating?
Answer: Spray polymerization – precipitation of solid additives; Sweating – the precipitation of liquid additives.
The compatibility between additives and polymers refers to the ability of additives and polymers to be uniformly mixed together for a long time without producing phase separation and precipitation;
3.What is the function of plasticizers?
Answer: Weakening the secondary bonds between polymer molecules, known as van der Waals forces, increases the mobility of polymer chains and reduces their crystallinity.
4.Why does polystyrene have better oxidation resistance than polypropylene?
Answer: The unstable H is replaced by a large phenyl group, and the reason why PS is not prone to aging is that the benzene ring has a shielding effect on H; PP contains tertiary hydrogen and is prone to aging.
5.What are the reasons for PVC’s unstable heating?
Answer: ① The molecular chain structure contains initiator residues and allyl chloride, which activate functional groups. The end group double bond reduces thermal stability; ② The influence of oxygen accelerates the removal of HCL during the thermal degradation of PVC; ③ The HCl produced by the reaction has a catalytic effect on the degradation of PVC; ④ The influence of plasticizer dosage.
6. Based on current research results, what are the main functions of heat stabilizers?
Answer: ① Absorb and neutralize HCL, inhibit its automatic catalytic effect; ② Replacing unstable allyl chloride atoms in PVC molecules to inhibit the extraction of HCl; ③ Addition reactions with polyene structures disrupt the formation of large conjugated systems and reduce coloration; ④ Capture free radicals and prevent oxidation reactions; ⑤ Neutralization or passivation of metal ions or other harmful substances that catalyze degradation; ⑥ It has a protective, shielding, and weakening effect on ultraviolet radiation.
7.Why is ultraviolet radiation the most destructive to polymers?
Answer: Ultraviolet waves are long and powerful, breaking most polymer chemical bonds.
8. What type of synergistic system does intumescent flame retardant belong to, and what is its basic principle and function?
Answer: Intumescent flame retardants belong to the phosphorus nitrogen synergistic system.
Mechanism: When the polymer containing the flame retardant is heated, a uniform layer of carbon foam can be formed on its surface. The layer has good flame retardancy because of its heat insulation, oxygen isolation, smoke suppression and drip prevention.
9. What is the oxygen index, and what is the relationship between the size of the oxygen index and flame retardancy?
Answer: OI=O2/(O2 N2) x 100%, where O2 is the oxygen flow rate; N2: Nitrogen flow rate. The oxygen index refers to the minimum volume percentage of oxygen required in a nitrogen oxygen mixture airflow when a certain specification sample can burn continuously and steadily like a candle. OI<21 is flammable, OI is 22-25 with self extinguishing properties, 26-27 is difficult to ignite, and above 28 is extremely difficult to ignite.
10.How does the antimony halide flame retardant system exhibit synergistic effects?
Answer: Sb2O3 is commonly used for antimony, while organic halides are commonly used for halides. Sb2O3/machine is used with halides mainly due to its interaction with the hydrogen halide released by the halides.
And the product is thermally decomposed into SbCl3, which is a volatile gas with a low boiling point. This gas has a high relative density and can stay in the combustion zone for a long time to dilute flammable gases, isolate air, and play a role in blocking olefins; Secondly, it can capture combustible free radicals to suppress flames. In addition, SbCl3 condenses into droplet like solid particles over the flame, and its wall effect scatters a large amount of heat, slowing down or stopping the combustion speed. Generally speaking, a ratio of 3:1 is more suitable for chlorine to metal atoms.
11. According to current research, what are the mechanisms of action of flame retardants?
Answer: ① The decomposition products of flame retardants at combustion temperature form a non-volatile and non oxidizing glassy thin film, which can isolate air reflection energy or have low thermal conductivity.
② Flame retardants undergo thermal decomposition to generate non combustible gases, thereby diluting combustible gases and diluting the concentration of oxygen in the combustion zone; ③ The dissolution and decomposition of flame retardants absorb heat and consume heat;
④ Flame retardants promote the formation of a porous thermal insulation layer on the surface of plastics, preventing heat conduction and further combustion.
12.Why is plastic prone to static electricity during processing or use?
Answer: Due to the fact that the molecular chains of the main polymer are mostly composed of covalent bonds, they cannot ionize or transfer electrons. During the processing and use of its products, when it comes into contact and friction with other objects or itself, it becomes charged due to the gain or loss of electrons, and it is difficult to disappear through self conduction.
13. What are the characteristics of the molecular structure of antistatic agents?
Answer: R-Y-X R: oleophilic group, Y: linker group, X: hydrophilic group. In their molecules, there should be an appropriate balance between the non-polar oleophilic group and the polar hydrophilic group, and they should have a certain compatibility with polymer materials. Alkyl groups above C12 are typical oleophilic groups, while hydroxyl, carboxyl, sulfonic acid, and ether bonds are typical hydrophilic groups.
14. Briefly describe the mechanism of action of anti-static agents.
Answer: Firstly, anti-static agents form a conductive continuous film on the surface of the material, which can endow the surface of the product with a certain degree of hygroscopicity and ionization, thereby reducing the surface resistivity and causing the generated static charges to quickly leak, in order to achieve the purpose of anti-static; The second is to endow the material surface with a certain degree of lubrication, reduce the friction coefficient, and thus suppress and reduce the generation of static charges.
① External anti-static agents are generally used as solvents or dispersants with water, alcohol, or other organic solvents. When using anti-static agents to impregnate polymer materials, the hydrophilic part of the anti-static agent firmly adsorbs on the surface of the material, and the hydrophilic part absorbs water from the air, thereby forming a conductive layer on the surface of the material, which plays a role in eliminating static electricity;
② Internal anti-static agent is mixed into the polymer matrix during plastic processing, and then migrates to the surface of the polymer to play an anti-static role;
③ Polymer blended permanent anti-static agent is a method of uniformly blending hydrophilic polymers into a polymer to form conductive channels that conduct and release static charges.
15.What changes usually occur in the structure and properties of rubber after vulcanization?
Answer: ① The vulcanized rubber has changed from a linear structure to a three-dimensional network structure; ② Heating no longer flows; ③ No longer soluble in its good solvent; ④ Improved modulus and hardness; ⑤ Improved mechanical properties; ⑥ Improved aging resistance and chemical stability; ⑦ The performance of the medium may decrease.
16. What is the difference between sulfur sulfide and sulfur donor sulfide?
Answer: ① Sulfur vulcanization: Multiple sulfur bonds, heat resistance, poor aging resistance, good flexibility, and large permanent deformation; ② Sulfur donor: Multiple single sulfur bonds, good heat resistance and aging resistance.
17. What does a vulcanization promoter do?
Answer: Improve the production efficiency of rubber products, reduce costs, and improve performance. Substances that can promote vulcanization. It can shorten the vulcanization time, lower the vulcanization temperature, reduce the amount of vulcanizing agent, and improve the physical and mechanical properties of rubber.
18. Burn phenomenon: refers to the phenomenon of early vulcanization of rubber materials during the processing.
19. Briefly describe the function and main varieties of vulcanizing agents
Answer: The function of the activator is to enhance the activity of the accelerator, reduce the dosage of the accelerator, and shorten the vulcanization time.
Active agent: a substance that can increase the activity of organic accelerators, allowing them to fully exert their effectiveness, thereby reducing the amount of accelerators used or shortening the vulcanization time. Active agents are generally divided into two categories: inorganic active agents and organic active agents. Inorganic surfactants mainly include metal oxides, hydroxides, and basic carbonates; Organic surfactants mainly include fatty acids, amines, soaps, polyols, and amino alcohols. Adding a small amount of activator to the rubber compound can improve its vulcanization degree.
1) Inorganic active agents: mainly metal oxides;
2) Organic active agents: mainly fatty acids.
Attention: ① ZnO can be used as a metal oxide vulcanizing agent to crosslink halogenated rubber; ② ZnO can improve the heat resistance of vulcanized rubber.
20.What are the post effects of accelerators and what types of accelerators have good post effects?
Answer: Below the vulcanization temperature, it will not cause early vulcanization. When the vulcanization temperature is reached, the vulcanization activity is high, and this property is called the post effect of the accelerator. Sulfonamides have good post effects.
21. Definition of lubricants and differences between internal and external lubricants?
Answer: Lubricant – an additive that can improve the friction and adhesion between plastic particles and between the melt and the metal surface of processing equipment, increase the fluidity of resin, achieve adjustable resin plasticization time, and maintain continuous production, is called lubricant.
External lubricants can increase the lubricity of plastic surfaces during processing, reduce the adhesion force between plastic and metal surfaces, and minimize the mechanical shear force, thereby achieving the goal of being most easily processed without damaging the properties of plastics. Internal lubricants can reduce the internal friction of polymers, increase the melting rate and melt deformation of plastics, reduce melt viscosity, and improve plasticization performance.
The difference between internal and external lubricants: Internal lubricants require good compatibility with polymers, reduce friction between molecular chains, and improve flow performance; And external lubricants require a certain degree of compatibility with polymers to reduce friction between polymers and machined surfaces.
22. What are the factors that determine the magnitude of the reinforcing effect of fillers?
Answer: The magnitude of the reinforcement effect depends on the main structure of the plastic itself, the amount of filler particles, the specific surface area and size, surface activity, particle size and distribution, phase structure, and the aggregation and dispersion of particles in polymers. The most important aspect is the interaction between the filler and the interface layer formed by the polymer polymer chains, which includes both the physical or chemical forces exerted by the particle surface on the polymer chains, as well as the crystallization and orientation of the polymer chains within the interface layer.
23. What factors affect the strength of reinforced plastics?
Answer: ① The strength of the reinforcing agent is selected to meet the requirements; ② The strength of basic polymers can be met through the selection and modification of polymers; ③ The surface bonding between plasticizers and basic polymers; ④ Organizational materials for reinforcing materials.
24. What is a coupling agent, its molecular structure characteristics, and an example to illustrate the mechanism of action.
Answer: Coupling agents refer to a type of substance that can improve the interface properties between fillers and polymer materials.
There are two types of functional groups in its molecular structure: one can undergo chemical reactions with the polymer matrix or at least have good compatibility; Another type can form chemical bonds with inorganic fillers. For example, silane coupling agent, the general formula can be written as RSiX3, where R is an active functional group with affinity and reactivity with polymer molecules, such as vinyl chloropropyl, epoxy, methacryl, amino, and thiol groups. X is an alkoxy group that can be hydrolyzed, such as methoxy, ethoxy, etc.
25. What is a foaming agent?
Answer: Foaming agent is a type of substance that can form a microporous structure of rubber or plastic in a liquid or plastic state within a certain viscosity range.
Physical foaming agent: a type of compound that achieves foaming goals by relying on changes in its physical state during the foaming process;
Chemical foaming agent: At a certain temperature, it will thermally decompose to produce one or more gases, causing polymer foaming.
26. What are the characteristics of inorganic chemistry and organic chemistry in the decomposition of foaming agents?
Answer: Advantages and disadvantages of organic foaming agents: ① good dispersibility in polymers; ② The decomposition temperature range is narrow and easy to control; ③ The generated N2 gas does not burn, explode, liquefy easily, has a low diffusion rate, and is not easy to escape from the foam, resulting in a high robe rate; ④ Small particles result in small foam pores; ⑤ There are many varieties; ⑥ After foaming, there is a lot of residue, sometimes as high as 70% -85%. These residues can sometimes cause odor, contaminate polymer materials, or produce surface frost phenomenon; ⑦ During decomposition, it is generally an exothermic reaction. If the decomposition heat of the foaming agent used is too high, it may cause a large temperature gradient inside and outside the foaming system during the foaming process, sometimes resulting in high internal temperature and damaging the physical and chemical properties of the polymer Organic foaming agents are mostly flammable materials, and attention should be paid to fire prevention during storage and use.
27. What is a color masterbatch?
Answer: It is an aggregate made by uniformly loading super constant pigments or dyes into a resin; Basic components: pigments or dyes, carriers, dispersants, additives; Function: ① Beneficial for maintaining the chemical stability and color stability of pigments; ② Improve the dispersibility of pigments in plastics; ③ Protect the health of operators; ④ Simple process and easy color conversion; ⑤ The environment is clean and does not contaminate utensils; ⑥ Save time and raw materials.
28. What does coloring power refer to?
Answer: It is the ability of colorants to affect the color of the entire mixture with their own color; When coloring agents are used in plastic products, their covering power refers to their ability to prevent light from penetrating the product.
Post time: Apr-11-2024