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With China Plastic Machinery
With China Plastic Machinery
Plastic profile products are widely used in: window frames, stair handrails, wiring troughs, skirting boards, special-shaped pipes, etc. The raw materials are mainly hard PVC, and a few are semi-hard PVC, soft PVC, polyurethane low foaming and other materials.
Due to the huge market demand and broad development prospects, plastic profile products have been rapidly developed in China in recent years. Due to the fierce market competition, all plastic machinery manufacturers consider a problem, how to improve the productivity and qualified rate of plastic profile products under the premise of ensuring product quality, and give full play to the maximum capacity of equipment to reduce the production cost of products.
With the continuous intensification of competition in the plastic profile industry, mergers and acquisitions and capital operations between large plastic profile companies are becoming more and more frequent. China's excellent plastic profile manufacturers are paying more and more attention to the research on the industry market, especially the in-depth research on the development environment of enterprises and the changes in customer demand trends. Because of this, a large number of excellent Chinese plastic profile brands have risen rapidly and gradually become the leaders in the plastic profile industry!
Plastic profiles are widely used in: window frames, stair handrails, wiring troughs, skirting boards, special-shaped pipes, furniture, building materials and other accessories. The raw materials are mainly hard PVC, and a few are semi-hard PVC, soft PVC, polyurethane low foaming and other materials.
For hard PVC plastic profiles, there is a disadvantage of poor impact resistance, and they are often modified by adding ACR, CPE, EVA, MBS, etc. to improve the impact strength. CPE (chlorinated polyethylene), EVA (ethylene-vinyl acetate copolymer), ACR (acrylate), MBS (methyl methacrylate-butadiene-styrene graft copolymer) are generally added in an amount of 6%~10%. MBS is mainly used in transparent plastic profile products. EVA is best not to be used with lead stabilizers. When used together, the molding processability is poor and it is easy to cause powder spots. CPE is best not to be used with zinc stabilizers, and CPE's low temperature performance is not very good.
When producing plastic profile products, process conditions such as temperature, screw speed, traction speed, etc. are controlled.
Plastic profiles are listed as one of the key building materials developed in China for their excellent thermal insulation performance. In the production process of plastic profiles, what issues need to be paid attention to in order to ensure the quality and process of the profiles. Let's take a look at what plastic profile additives are there?
If no impact modifier is added in the production of plastic profiles, the plastic profiles will be very brittle and hard, and will be easily broken with a slight collision. The impact modifiers commonly used in the production of plastic profiles are mainly divided into the following three categories: chlorinated polyethylene, polyacrylates, and ethylene-vinyl acetate copolymers.
Plastic profiles are heat-sensitive plastics, so heat stabilizers are indispensable in the production and processing of plastic profiles. The metal salt in the heat stabilizer can absorb HCL decomposed from PVC, so it can slow down the decomposition speed of plastic and prolong the decomposition time. The most commonly used in the production of plastic profiles is the composite lead salt, which has high thermal stability efficiency and low price.
The main function of the lubricant is to reduce the mutual friction between the polymer and the processing equipment and between the internal molecules of the polymer, prevent the resin degradation caused by excessive friction heat, and improve the efficiency of the heat stabilizer.
Processing aids are a type of improvement additives developed mainly to improve the processing performance of plastic molding. The processing temperature of plastic profiles is close to the decomposition temperature, the fluidity is poor, and it is easy to stick to the equipment and coke. Therefore, a certain amount of processing aids needs to be added in the production of plastic profiles to overcome the defects of the plastic profiles themselves.
Light stabilizers can inhibit the photo-oxidative degradation reaction of polymers by shielding and absorbing ultraviolet rays, quenching excitation energy capture free radicals, etc., thereby giving the products good light stabilization effects and extending their service life.
Fillers are solid additives that are different from plastics in composition and structure, also known as fillers. It has obvious effects and economic value on improving certain physical and mechanical properties of plastics and reducing plastic costs. Adding fillers to the production formula of plastic profiles can reduce the rate of dimensional change of plastic profiles after heating, improve impact strength, increase rigidity, and reduce production costs.
In the production process of plastic profiles, due to improper formulation or unreasonable plastic processing technology, plastic profiles become brittle, with the main characteristics of: collapse during feeding and cold punching rupture. The following Qingdao Plastic Machinery provides you with the reasons for the poor physical and mechanical properties of plastic profile products.
Reason 1 for brittle plastic profiles: unreasonable formula and process during the production of plastic profiles
Due to the decrease in the price of plastic profiles and the increase in the price of raw materials, many manufacturers have reduced the quality of plastic profiles while reducing costs. Due to the composition of the formula, the most direct and effective way is to increase the filler. The commonly used filler in the production of PVC-U plastic profiles is calcium carbonate. With the development of technology, most of them use ultra-fine lightweight activated calcium carbonate, or even nano-scale calcium carbonate, which not only increases rigidity and fills, but also has a modifying effect. However, the amount of calcium carbonate added is not unlimited, and its proportion should be controlled. Nowadays, some manufacturers add calcium carbonate to 20-50 parts by mass in order to reduce costs, which greatly reduces the physical and mechanical properties of the profiles and causes the brittleness of plastic profiles.
Impact modifiers are a kind of high molecular polymer that can increase the total energy of polyvinyl chloride rupture under stress. The main types of impact modifiers for rigid polyvinyl chloride are CPE, ACR, MBS, ABS, EVA, etc. Among them, the molecular structure of CPE, EVA, and ACR modifiers does not contain double bonds, has good weather resistance, and is suitable for outdoor building materials. When mixed with PVC, they can effectively improve the impact resistance, processability, weather resistance, and weld angle strength of rigid polyvinyl chloride within a certain range. Experimental demonstration shows that the impact strength of ACR is about 30% higher than that of CPE. Therefore, the PVC/ACR blend system is used as much as possible in the formula, and when CPE is used for modification and the amount is less than 8 parts by mass, it often causes the plastic profile to become brittle.
The amount of stabilizer varies depending on the type of plastic profile, but in general, excessive use will delay the plasticization time of the material, so that the material is still under-plasticized when it exits the mold. The molecules in the formula system are not completely dissolved, and the intermolecular structure is not strong. When the dosage is too small, the relatively low molecular weight substances in the formula system will be degraded or decomposed (it can also be said to be over-plasticization), which will damage the stability of the molecular structure of each component. Therefore, the amount of stabilizer used will also affect the impact strength of the plastic profile. Too much or too little will cause the profile strength to decrease and cause the plastic profile to become brittle.
The external lubricant has low solubility with the resin and can promote the sliding between the resin particles, thereby reducing the friction heat and delaying the melting process. This effect of the lubricant is the greatest in the early stage of the processing process. External lubricants are divided into early lubrication and late lubrication. Over-lubricated materials show poor appearance under various conditions. If the lubricant is not used properly, it may cause flow marks, low yield, turbidity, poor impact, rough surface, adhesion, poor plasticization, etc. In particular, when the dosage is too large, it will cause poor density and poor plasticization of the plastic profile, resulting in poor impact performance and causing the plastic profile to become brittle.
Plastic profile extrusion mold is the core part of extrusion production. The technical status of plastic profile extrusion mold is directly related to the stability of extrusion production, the quality of extruded products, the extrusion production efficiency and the service life of the mold itself. Therefore, the correct use and maintenance of plastic profile extrusion mold is very important.
1. Unpacking inspection of plastic profile extrusion mold after arrival
Unpacking inspection, the packaging is intact: after unpacking, take out the packing list, instruction manual and other technical documents, and count the mold parts, accessories, special tools, etc. according to the contents of the packing list.
2. Half of the technical requirements and status of plastic profile extrusion mold
£¾£¾ Especially when the extruded material is modified polyvinyl chloride, the molding parts of plastic profile extrusion mold are generally made of corrosion-resistant materials such as stainless steel, and tempered to HRC24 or above to ensure a certain service life.
£¾£¾ The working surfaces of the die, shaping die and their parts should be smooth, and should not have defects such as bumps, scratches, burrs, attachments and rust.
£¾£¾ The die head flow channel system should be smooth along the direction of melt flow, and try to avoid sudden changes in cross-section and stagnant areas.
£¾£¾ There should be reliable positioning between each template, and the loading and unloading repeatability error between the corresponding positions of each template should not exceed 0.03mm; the joint surfaces and joints of the die head of the plastic profile extrusion mold should be well fitted, and the local gap should not be greater than 0.02mm.
£¾£¾ The cooling system and vacuum system of the shaping mold should be unobstructed and leak-free. Under normal circumstances, the water and gas systems should not be connected to each other. The water pipe joints and vacuum pipe joints of the shaping mold of the plastic profile extrusion mold should have obvious signs and should not affect the connection of the pipeline.
£¾£¾ The shaping die of the plastic profile extrusion die should be flexible to open and close, and the blocks in each section of the shaping die and the water tank should ensure a certain degree of coaxiality.
In recent years, China's plastic profile industry has accelerated the pace of research and development and promotion and application, and its production and sales volume has remained the largest in the world. Among them, plastic pipes, plastic sheets and other products have entered a stable and mature growth period and are the most mature varieties of plastic profiles.
The main products of the plastic profile industry include: plastic doors and windows, plastic pipes, plastic sheets, plastic waterproofing membranes and plastic profiles. Among them, plastic profiles, plastic pipes, plastic sheets and other products have formed a huge chemical building materials industry chain in China. Plastic profiles alone have an annual production capacity of 2.8 million tons, and China has entered the ranks of plastic powers.
Today, plastic building materials and other products have begun to develop from interior decoration parts to structural parts and functional parts. The sales of plastic flooring and wall decorations have maintained a steady growth. Polymer building templates, waterproof materials, exterior wall supports, exterior wall insulation boards, plastic reinforced bricks, etc. have been increasingly used, and their growth rate has even exceeded that of plastic pipes.
It is expected that in the next 5-15 years, under the guidance of various national building energy-saving policies, the plastic building materials market is expected to develop more rapidly. By 2015, the average market share of various building plastic pipes and plastic doors and windows in China will reach 50% and 30% respectively. In terms of demand, the total demand for various building plastic pipes and plastic doors and windows, plus polymer waterproof materials, decorative materials, insulation materials and other plastic products for construction is expected to reach 10 million tons.
The rapid development of the industry and the continuous expansion of production capacity have intensified the competition among plastic profile companies. In addition, the Chinese market has gradually become saturated, and many profile companies have begun to look for development opportunities in the international market. In the future, competition among plastic profile companies will depend more on the level of mastery of core technologies among companies. In addition to continuously improving the comprehensive level of their products, companies must also adapt to industry standards in different countries and obtain relevant international certifications or access permits.
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