Classification of petroleum resin products

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The classification of petroleum resin products is more complicated than other resins commonly used in rubber, because it has many raw materials and can be flexibly selected in terms of raw material selection and manufacturing process in order to meet different usage environments and requirements.

Divided by raw materials, they can usually be divided into three categories.

  1. The aromatic petroleum resin is subjected to self-polymerization or block copolymerization under the action of a catalyst by using a petroleum-cut fraction raw material. Different catalytic systems can be employed depending on the polymerization process. The properties of the resulting resins may vary widely due to the different components involved in the reaction.

After adding such petroleum resin to the rubber grommets raw material, the hardness and the tensile stress are improved, and the anti-aging property is better. The comparison data before and after aging is stable and uniform. The wear resistance and tear resistance can be increased by 20% after adding the resin, which is very beneficial for rubber grommets.

  1. The petroleum resin and the rubber of the aliphatic petroleum resin have good compatibility, but because of its high content of diene and high degree of unsaturation, the thermal stability is poor, but the viscosity increasing effect is superior to that of the ancient Malone resin.

This type of resin is obtained by the dispersion of C5, a by-product of ethylene cracking, and is mainly composed of a trans structure. It is obtained by anionic polymerization under the catalysis of a Lewis acid.

  1. Block copolymerized petroleum resin This is a third type of petroleum resin other than the above two types, which is a regular block copolymer of an aromatic fraction and an isoprene monomer. The order of the block copolymerized petroleum resin structure is similar to that of thermoplastic SBS, which is polymerized by initiation of an anionic catalyst. The advantage of this product is that it is suitable for two elastomer materials with widely different polarities, which integrates the elastomer materials which were impossible to blend, which simplifies the production process of rubber grommets and promotes the complementary performance between them.

Product shape and performance of petroleum resin

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The petroleum resin is a yellow to brown resinous solid, having a molecular weight of 600-8000, a softening point of 66 to 125 ° C, a relative density of 0.97 to 0.975, a flash point of 260 ° C, an acid value of 0 to 2, and a saponification value of 0 to 29 and a refractive index of 1.58 to 1.60. Petroleum resins have good characteristics such as low acid value, good compatibility, low melting point, water resistance, ethanol resistance and chemical resistance. Petroleum resins are soluble in paraffinic hydrocarbons and chlorinated hydrocarbons, but insoluble in lower alcohols and ketones.

Some of the key properties in the many properties of petroleum resins are as follows:

  1. Softening point The solid petroleum resin must be uniformly dispersed into the rubber matrix by kneading. Therefore, the softening point must be within the temperature range of the elastomeric viscous flow state. In the production of rubber feets, the temperature of the mixer mixing chamber is generally controlled at 100 to 120 ° C, which matches the softening point of the petroleum resin.
  2. The acid value reflects the total content of the acidic substance in the resin. It can also measure the change of the hydroxy compound when the resin is parked, which is important for controlling the storage stability of the resin.
  3. The ash content is used to evaluate the amount of inorganic matter in the resin, and the amount of the remaining catalyst can be understood to understand the degree of removal of the unreacted catalyst in the resin.
  4. Compatibility reflects the degree of compatibility of the resin with the compound after it is added to the compound. If the compatibility is not good, it will inevitably appear frosting during rubber storage or rubber feets storage, which will affect the appearance and feel of the product, and even affect the service life.

In summary, the petroleum resin used in rubber feet should generally have a low acid value, which means good stability and good compatibility with the rubber main material, meaning that the effective duration after compatibility is relatively long, and the melting point is relatively low. To prevent the surface of its sneeze product from affecting the service life. The melting point should be suitably lower to speed up its flow in the rubber to obtain a better dispersion effect, especially when used as a tackifier and softener, but also to prevent softening points from being too low for certain requirements. Products with certain mechanical properties are not good. In addition, water resistance and chemical resistance should be considered.

Raw material selection and formula design points of hard rubber

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Due to the special use, hard rubber has obvious differences in raw material selection and formulation design compared with other rubber products.

1） Glue selection of high-unsaturated raw rubber such as natural, butylbenzene, butadiene and chlorine
Ding et al. apply because high hardness comes from intensive cross-linking, while low-unsaturated rubbers (such as butyl and EPDM) do not. Waste rubber powder can also be used, but it can only be used as an additive and cannot replace raw rubber. Its advantages are reflected in two aspects: first, it helps to make rubber; second, it can reduce the quality problems of common pores, sponges and bursts of hard rubber. Recycled rubber can replace part of the raw rubber, but also reduce the shrinkage of the rubber, which is beneficial to extrusion and calendering, but it is not good against impact and bending resistance. In addition, synthetic rubber is advantageous for heat resistance and hardness improvement.

2） Vulcanizing agent Sulfur is the most commonly used vulcanizing agent. The theoretical amount should be 37 parts (100 parts by weight of rubber), and it is usually controlled in the range of 35 to 40 parts. A sulfur promoter can also be used in place of sulfur. Like soft rubber, the sulfur bond structure is also divided into single sulfur, disulfide and polysulfide.

3） Promoter accelerators are generally less effective than soft gels in hard gels, and have anomalous phenomena. For example, the promotion effect of TMTD is not as good as accelerator D. More commonly used is the combination of an inorganic accelerator and an organic accelerator. Application examples are 5 parts of magnesium oxide + accelerator 808 #1.5 parts.

4） Softeners can improve the process of mixing, extrusion, etc., but are not conducive to the impact resistance, bending and heat resistance of the product. Applicable varieties are mineral oil, asphalt, paraffin, ancient horse and so on.

5） Fillers are good for hardness improvement and shrinkage reduction, but they are not good for physical properties and insulation properties, so it is necessary to control the dosage, except for hard rubber powder, which can reduce shrinkage during processing and reduce heat generation. The only drawback is the reduced heat resistance.

6） Hard rubber Because almost all double bonds have been saturated by cross-linking, there is no aging problem, and anti-aging agents are generally not used.

(2) Manufacturing process

From the rubber to the molding, the manufacturing process is similar to other rubber products, but the vulcanization has a larger difference. In general there are three types of vulcanization methods:

1） Direct vapor vulcanization is suitable for thin products with low surface quality requirements, such as chemical linings and smaller products.

2） Flat vulcanization is suitable for model products, such as battery tanks and various types of plates, tubes, rods and other profiles.

3) Water bath vulcanization is suitable for products with high gel content and products with hydrous silicic acid as filler, such as microporous separator.
The vulcanization of hard rubber is suitable for high crosslink density, and the process generally takes:

A longer curing time, such as the battery cover vulcanization time up to 165min;
B two or three stages of vulcanization;
C Gradually warm up.

(3) Performance indicators

Hard rubber performance evaluation items are also different from soft rubber, generally including the following four items: breaking strength (MPa); impact strength (J∕m3); Martin heat resistance (°C); weight gain rate in acid (% ).

Rubber synchronous toothed belt structure

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The rubber synchronous toothed belt is named for the high synchronization between the belt body and the transmission wheel, referred to as the timing belt. It combines the lengths of different transmission methods (gears, chains and tapes) to reflect high efficiency, stability, low noise, no lubrication and many other advantages. All of this comes from the precise engagement between the toothed body of the working face and the drive wheel groove. Therefore, during the transmission process, there is no relative slip between the belt body and the transmission wheel, so that the synchronous transmission can be realized at any instant.

Variety

Trapezoidal timing belt and elliptical timing belt

According to the shape of the tooth body, it is divided into two types: a trapezoidal timing belt and an elliptical timing belt. The former (Fig. 6·12 left) is the earliest conventional variety, with its tooth body showing a large and small trapezoidal shape. The latter (Fig. 6-12 right) appeared in the 1970s, and the tooth body has a circular arc shape. Compared with the trapezoidal timing belt, it can withstand greater torque.

Trapezoidal timing belt and elliptical timing belt

Later, in order to adapt to the emergence of multi-axis transmission, a double-sided timing belt was derived, and the pitch, the tooth shape and the timing belt of the single-sided transmission were the same. The difference is that the upper and lower teeth have teeth, and they are arranged in two ways: symmetry and staggering.


Structure

Figure 6 · 18 basin support (left is movable, right is fixed)


It usually consists of a rubber layer (backing), a strong layer (skeleton layer), a toothed layer and a covering layer.


Raw materials


(1) Adhesive layer
The backing layer can be made from dry glue (usually neoprene) or from liquid polyurethane (crosslinked to solid).
(2) Power layer
The strength layer is usually made of synthetic fibers, such as nylon, polyester, aramid yarn, cord, glass fiber and steel wire.
(3) tooth body
The tooth composition is identical to the adhesive layer.
(4) Cover layer
The cloth layer is a hanging rubber canvas.

History of hard rubber

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Hard rubber is a product obtained by vulcanizing raw rubber and high-dose sulphur, which is named for its hard texture and horn-like appearance.

The concept of hard rubber was first proposed by the British Hancock and applied for the first patent. In 1851, American Gude followed Hancock’s ideas. The first one was put into practice. After mixing natural rubber with sulfur, it was vulcanized for a long time to obtain hard rubber.

In the following 100 years, the product types of hard rubber continued to multiply with the expansion of the application surface, mainly in the following fields: first, electrical insulation products, including battery casings and miners’ caps; the second major category is to use it. Superior chemical resistance to make chemical reaction tanks, pipes, pump linings and pipelines that contact corrosive fluids; the third category is equipment, components used in life, culture or entertainment, such as black tubes in musical instruments, stationery The pen pen in the middle; the fourth type is the components for the rubber industry itself, such as the transition layer between the rubber core and the outer rubber layer.

With the rise of various thermoset plastics, some of the above-mentioned third-use uses have been gradually replaced by hard plastics, but the remaining categories are still dominated by hard rubber.