On the one hand, it will be more functional, and constantly pursue the perfection of product function and extension of service life; On the other hand, while optimizing the quality of products, we will pursue to greatly reduce the cost of raw materials and operating costs, so as to obtain greater benefits.
Medium and large blow molding products
Three basic principles should be taken into account in the formulation design of blow molding products:
1) Try to meet the various functions and uses of hollow blow molding products;
2) The plastic raw material formula has good processing performance;
3) Reduce production cost through formulation design and improvement.
At the same time, due to the expansion of extrusion blow molding products and engineering supporting range, the performance of blow molding products put forward higher technical requirements. Such as automobile, car, high-speed rail industry, aviation, aerospace, navigation, machinery, electronics, chemical, logistics, drug packaging, food and beverage packaging, daily household, agriculture, engineering application, surface floating body and many other industries supporting blow molding products and so on, High strength, high stiffness, high precision, long life and good temperature resistance are required for plastic blow molding products. Therefore, the modification of these blow molding products is very important.
Plastic modification methods mainly include physical modification and chemical modification. Chemical modification refers to modification methods that change the types and combinations of atoms or groups on the molecular chain of polymers by chemical methods. Plastics can form new specific polymer materials by block copolymerization, graft copolymerization, cross-linking reaction, or by introducing new functional groups. Chemical modification can make the product obtain new functions or better physical and chemical properties.
In the actual operation of formula modification of extrusion blow molding products, physical modification technology is more commonly used than chemical modification technology. The physical modification technology of extrusion blow molding products is commonly used in the following ways: ① filling modification; ② Blending modification; ③ Enhanced modification; (4) toughening modification; (5) nano-composite modification; ⑥ Functional modification and so on.
1. Formulation technology of commonly used blow molding products
1) 25L plastic bucket formula, see Table 1.
25L plastic bucket formula
It can be seen from the formula in Table 1 that two brands of HDPE are used in the formula, and the strength, hardness and toughness of blow molded products can be guaranteed to meet the basic requirements of 25L series plastic buckets.
The two main ingredients in the formula are configured in half. In practical application, the proportion of main ingredients in the formula can be adjusted according to different performance needs. At the same time, the brand selection of main ingredients can also be selected according to the specific situation of the market supply.
2) Formulation design of hollow plastic packaging barrel for hazardous Chemicals:
Such as: trial production of 25L container packaging drum, the mass of the drum is 1800g. Used for containing concentrated nitric acid of 68.2% concentration. The resistance of pure HDPE container to concentrated nitric acid is insufficient, but the resistance of HDPE to concentrated nitric acid can be significantly improved by adding appropriate polymer modifier. That is, EVA and LC are used to modify HDPE to produce concentrated nitric acid packaging container. The test formula is shown in Table 2.
Formula of hollow plastic packing barrel for dangerous chemicals
In Table 2, HDPE is HHM5205, and melt flow rate MFI=0.35g/10min. EVA 560, melt flow rate MFI= 3.5g /10min, density =0.93, VA content 14%; Low molecular modifier LC, made in China, industrial grade. The test results of packing drums prepared by the above three formulas are shown in Table 3. The above three formulations are all qualified by ordinary packing inspection. However, for containing concentrated nitric acid, formula 1 month after the rupture, so it is not suitable for containing concentrated nitric acid; Formula 2 6 months after the drop test barrel broke, unqualified, although other tests passed, if used to contain concentrated nitric acid is dangerous, it is not recommended to use;
Medium and large hollow blow molding product formulation technology
Formula 3 As shown in Table 3-18, all tests were qualified after half a year of concentrated nitric acid.
In conclusion, after adding EVA and LC into HDPE, the resistance of modified HDPE to concentrated nitric acid is improved obviously, and it can be used to manufacture concentrated nitric acid (68.4%) packaging barrel.
3) A plastic formula table for outdoor plastic seats. (See Table 4)
Note: 7000F and 6098 in the formula in Table 4 are hdPe with high molecular weight. 18D is low density polyethylene.
EVA is mainly used as a processing aid in this formula to improve the appearance quality of blow molded products and enhance the impact resistance. And it has a longer resistance to environmental stress cracking time.
4) For the recipe of 50-100L blow molded containers, see Table 5.
The utility model relates to a plastic formula table for outdoor plastic seats
The formula in Table 5 can be adjusted according to actual use.
In the formula in Table 5, with the increase of the proportion of plastic raw materials with higher molecular weight, the strength, stiffness and temperature resistance of the products are enhanced, and the environmental stress cracking resistance time is prolonged. Product manufacturers can adjust the different proportions of various plastic raw materials according to the requirements of different products to meet different technical requirements.
5) 100-220L blow molded containers
Because the relative molecular weight of ordinary high density polyethylene resin is not high, such as HHM5502 resin is a typical blow molded ethylene and hexene copolymer with a relative molecular weight of about 150,000, although its mechanical properties, rigidity and surface hardness are good, But the environmental stress cracking resistance and impact strength are poor, the melt strength is not high, and the drooping phenomenon is serious in the process of extrusion billet. If the resin manufacturing 200L, net weight 10.5kg plastic VAT according to the national standard for drop test, there will be rupture phenomenon. It can be seen that the resin with lower molecular weight is basically not suitable for the production of large plastic barrels of more than 100 ~ 200L. Using HMWHDPE resin with a relative molecular weight of more than 250 thousand blow molding of more than 200L large bucket in the same test conditions as the drop test, usually does not occur rupture phenomenon, at the same time the uniformity of the barrel wall thickness has been significantly improved, the large bucket resistance to environmental stress cracking ability has been doubled. Therefore, when designing the formula of 100-220 liters large hollow plastic barrel, the relative molecular weight greater than 250,000 must be considered as the first indicator, followed by the density of resin. Practice has proved that, When the density of resin is in the range of 0.945 ~ 0.955g/cm 3, the rigidity and stress cracking resistance of high molecular weight HIGH-DENSITY polyethylene resin products are relatively balanced.
In industrial production, when the impact resistance and stress cracking resistance of products are demanding (such as gasoline tank, etc.), resin with a density of 0.945g/cm 3 is often used as raw material; The second is the processing properties of relative ease.
Nowadays, many countries design and produce special raw materials for large plastic buckets. Its relative molecular weight, melt flow rate and relative density are suitable for making large hollow plastic buckets.
In 200 L double L ring production formula of dangerous package barrel, long-term blow molding production experience has shown that using a variety of grades of high molecular weight polyethylene plastic raw materials combination formula for production, its product quality is better than the single plastic raw materials formula production stability and other performance will improve more, this worthy cause dangerous package barrel products factory attaches great importance to, In order to reduce the production loss caused by single plastic raw material. In addition, it is worth reminding that due to the special use requirements of 200L double L ring dangerous bale drums, it is concluded from a lot of practical experience that: Don’t blindly in large-scale hollow blow molding of plastic raw materials adding mineral masterbatch to reduce costs or improve the hardness, or greater impact on the quality of products, especially for the liquid dangerous goods packaging barrels, the quality of the products will be difficult to fully safeguard, in this recipe modification technology has yet to be further research and development.
Extrusion blow molding products more and more, the use of conditions vary, the use of more and more plastic raw materials, varieties, brands are also numerous, from the reality of production, blow molding manufacturers need to design and improve the formula of each product according to their own product characteristics, so as to achieve better results. The common formula technology introduced above is only the common formula of some common blow molding products, and it is suggested to be used for reference in the specific production of blow molding products.
Post time: Oct-28-2021