PVC is mainly composed of polyvinyl chloride, bright color, corrosion resistance, strong durability, because in the manufacturing process to increase the plasticizer, anti-aging agents and other toxic auxiliary materials to enhance its heat resistance, toughness, ductility, etc., so its products generally do not store food and medicine. It is a kind of synthetic material that is popular in today's world and has been widely used. Its global use is ranked second in all kinds of synthetic materials. According to statistics, only 1995 years, PVC production in Europe is about 5 million tons, and its consumption is 5.3 million tons. In Germany, the average production and consumption of PVC is 1.4 million tonnes. PVC is being produced and applied worldwide with a growth rate of 4%. The growth rate of PVC in Southeast Asia has been particularly remarkable in recent years, thanks to the urgent need for infrastructure construction in Southeast Asian countries. In the material that can produce three-dimensional surface film, PVC is the most suitable material.
The use of PVC materials is very wide, mainly used for production: Priven PVC card, PVC sticker, PVC wire, PVC curtain, PVC coated welded wire mesh, PVC foam board, PVC ceiling, PVC water pipe, PVC kick line and so on, as well as threading tube, cable suppliers insulation, plastic doors and windows, plastic bags and so on. PVC products are seen everywhere in our daily life field. PVC is used to make all kinds of imitation leather, for luggage bags, sports products, such as basketball, football and rugby. It can also be used to make belts for uniforms and special protective equipment. PVC material is very widely used, and has good processability, low manufacturing cost, corrosion resistance, insulation and other good characteristics.
Performance of PVC Hose
Pure polyvinyl chloride (PVC) resin belongs to a kind of strong polar polymer, its intermolecular force is larger, which leads to the softening temperature of PVC and the high melting temperature, which generally need 160~210℃ to process. In addition, PVC molecule contains some substitution chlorine base easily lead to PVC resin off hydrogen chloride reaction, resulting in PVC degradation reaction, so the heat is very unstable PVC, temperature rise will greatly promote the PVC off HCL reaction, pure PVC in 120 ℃ when the start off HCL reaction, resulting in PVC degradation. In view of the above two deficiencies, PVC in processing need to add additives, in order to be able to produce a variety of people to meet the needs of soft, hard, transparent, electrical insulation good, foaming and other products. In selecting the variety and dosage of auxiliaries, we must consider all factors, such as physical-chemical properties, fluidity and formability, and finally establish the ideal formula. In addition, we also need to make a choice of the resin model according to the different use and the processing way.
Forming temperature of PVC Hose
1. Raw materials according to the formula requirements, a variety of raw materials in the first PVC resin and plasticizer into the mixing mixer mixing. Specific requirements and PVC hose raw materials blending method. When the material temperature reaches 110~120°. , in the cold mixer, stir and break the caking material, so that the mixture of uniform temperature drops to 45 ℃ below.
2. For the inner layer of extruded PVC hose, the temperature of the extruder barrel Feeding section is 90~120℃, the temperature of plasticizing section is 130~150℃, the homogenization temperature is 160~170℃, and the forming mold temperature is 170~180℃.
3. For extrusion laminating PVC Hose outer layer, extruder barrel Feeding section temperature is 110~130℃, plasticizing section temperature is 140~160℃, homogenization section temperature is 160~170℃, molding mold temperature is 170~180℃.
The formula of PVC Hose
I. Selection of resins
The usual viscosity or K value in industry denotes weight (or average degree of aggregation). The molecular weight of the resin is related to the physical and mechanical properties of the product. The higher the molecular weight, the higher the tensile strength, the impact strength and the elastic modulus of the product, but the fluidity and plasticity of the resin melt decreased. At the same time, the synthetic process, resulting in a different form of resin, we are common is the suspension of the production of loose resin, commonly known as SG resin, its loose tissue, irregular surface shape, the cross-section of the transmission of porous mesh. Therefore, SG resin absorbs plasticizer quickly, plasticizing speed quickly.
II. Plasticizer System
The addition of plasticizers can reduce the force of the PVC molecular chain, so that the glass temperature of PVC plastic, the flow temperature and the melting point of the micro-crystal are reduced, plasticizer can improve the plasticity of the resin, so that the product is soft and low temperature resistance.
The effect of plasticizer on the mechanical strength is not obvious when the 10 parts are below, when the plasticizer with about 5 parts is added, the mechanical strength is the highest, so-called anti plasticizing phenomenon It is generally believed that the reverse plasticizing phenomenon is added to a small amount of plasticizer, macromolecular chain activity increases, so that the molecular order to produce microcrystalline effect. With a small amount of plasticizer of hard products, the impact strength is less than no overtime, but after the increase to a certain dosage, the impact strength increases with the dosage, to meet the universal law. In addition, the addition of plasticizers, products of heat resistance and corrosion resistance have decreased, each addition of a plasticizer, Martin Heat-resistant $number. Therefore, the general hard products do not add plasticizers or less plasticizer. Several plasticizers are sometimes added to improve processing liquidity. and soft products need to add a large number of plasticizers, the greater the plastic dosage, the softer the product.
The types of plasticizers are phthalic acid esters, straight chain esters, epoxy, phosphate ester, and so on its comprehensive performance, DOP is a good variety, can be used in a variety of PVC products formulations, straight chain esters such as DOS are hardy plasticizer, long used in agricultural film, it and PVC compatibility is not good, generally not more than 8 copies, Epoxy Plasticizer In addition to cold resistance, but also with heat, light resistance, especially with the metal soap stabilizer with synergistic effect, epoxy plasticizer general dosage for $number. Wire, cable products need to be flame-retardant, and should be selected with relatively good electrical properties of plasticizers. PVC itself has flame-retardant property, but after the plasticized soft products are mostly flammable, in order to make the soft PVC products have flame-retardant, should add flame retardant plasticizer such as phosphate ester and chlorinated paraffin, the two types of plasticizers are better electrical properties than other plasticizers, but with the increase in plasticizer dosage, the overall electrical performance decreased. For non-toxic use of PVC products, should be used non-toxic plasticizers such as epoxy soybean oil. As to the total amount of plasticizer, it should be different depending on the degree of softness of the product and the use, process and environment. The general calendering process produces PVC film, the total amount of plasticizer is about 50. Blow plastic film slightly lower, generally in the 45~50 part.
III. Stabilizing Agent System
PVC is processed at high temperature, so it is easy to release HCL and form unstable polyolefin structure. At the same time, the HCL has the self catalysis, will cause the PVC further degradation. In addition, if the presence of oxygen or iron, aluminum, zinc, tin, copper and cadmium plasma presence, will be the degradation of PVC catalysis, accelerate its aging. Therefore, plastic will appear a variety of undesirable phenomena, such as discoloration, deformation, cracking, mechanical strength drop, electrical insulation performance decline, such as brittle. In order to solve these problems, the formula must be added stabilizer, especially heat stabilizer is essential. The stabilizers used for PVC include heat stabilizers, antioxidants, ultraviolet absorbers and chelating agents. In the formulation design, according to the product use requirements and processing technology requirements of different varieties, the number of stabilizers.
(i) Thermal stabilizer heat stabilizer must be able to capture PVC resin released by the self catalytic HCL, or can be produced with PVC resin instability of the structure of the polymer to reflect, to prevent or reduce the decomposition of PVC resin. Generally in the formulation of the selection of heat stabilizer characteristics, function and product requirements to consider. For example: Lead salt stabilizer is mainly used in hard ware.
The lead salt stabilizer has the advantages of good thermal stabilizer, excellent electrical properties and low price. But its toxicity is large, easy to pollute products, can only produce opaque products. In recent years, the composite stabilizer has appeared in large quantities and the single component stabilizer has been replaced. Composite stabilizer is characterized by strong specificity, small pollution, simple ingredients of processing enterprises and other advantages. However, because there is no uniform standard, the composite stabilizer varies greatly.
Barium-cadmium stabilizer is a kind of heat stabilizer with good performance. Widely used in PVC agricultural film. It is usually used for barium cadmium zinc and organic phosphite ester and antioxidant.
Calcium Zinc stabilizer can be used as a non-toxic stabilizer, in food packaging and medical equipment, pharmaceutical packaging, but its stability is relatively low, calcium-type stabilizer dosage is poor transparency, easy to spray frost. Calcium and zinc stabilizers generally use polyols and antioxidants to improve their performance, recently has been used in the domestic hard tubes calcium and zinc composite stabilizer appeared.
PVC products in the process of processing, due to the role of heating, ultraviolet radiation oxidation, oxidation and degradation of the formation of free radicals. The main antioxidant is a chain fracture termination agent or a free radical elimination agent. Its main role is to combine with the free radicals, forming a stable compound, so that the chain reaction is terminated, and the main antioxidant used for PVC is bisphenol A. There are also auxiliary antioxidant or hydrogen peroxide decomposition agent, PVC-assisted antioxidant for phosphite and diphenyl phosphite. The main auxiliary antioxidant can play a synergistic role.
(iii) Ultraviolet absorbing agent
In the outdoor use of PVC products, due to its sensitive wavelength range of ultraviolet irradiation, PVC molecules into an excited state, or its chemical bond is destroyed, causing the free radical chain reaction, to promote the degradation of PVC and aging. In order to improve the ability of anti-ultraviolet, often add ultraviolet absorbent. PVC commonly used ultraviolet absorber has triazine-5, UV-9, UV-326, TBS, Bad, OBS. Triazine-5 effect is best, but because the yellow makes the film slightly yellow, adding a small amount of phthalocyanine can be improved. PVC agricultural film commonly used UV-9, in the general dosage of 0.2 ~ 0.5 parts. is the salicylic acid type TBS, bad and OBS function moderate, with the use of antioxidant, will get very good anti-aging effect. For non-transparent products, generally by adding shading rutile titanium dioxide to improve weather resistance, at this time if the addition of ultraviolet absorbent, it will require a lot of dosage, not very good.
(iv) Chelating agents
In the PVC plastic stability system, the frequently added phosphite ester is not only the auxiliary antioxidant, but also acts as chelating agent. It can generate metal complexes and materials with harmful metal ions that drive PVC off the HCL. The commonly used phosphite esters are phosphoric acid diphenyl ester, dioctyl phosphite and Diphenyl phosphite. In the PVC agricultural film, the general dosage is 0.5 ~ 1 parts, the initial period is easy to color, the thermal stability is not good, generally with the metal soap class.