Category: V-belts

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.

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.

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

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

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.

It is divided into two types: molding method (using dry glue as raw material) and casting method (using liquid polyurethane as raw material).

(1) Molding method

1) The main raw material rubber is mainly neoprene, and the reinforcing layer is usually made of steel wire rope or aramid rope. Requirements for strong ropes include high elongation, low elongation and low thermal deformation.
2) Two methods of forming parting and forming drum:
The mold method is divided into five steps, the first step, the patch cloth (lapped with 45° obliquely); the second step, the embedded rack; the third step, the winding rope, the single tension requirement reaches 78-100N; Four steps, filming, with a 0.5mm thick film multi-layer package to the specified thickness; the fifth step, add the outer hoop, put it into the vulcanization tank for vulcanization.
The forming drum method is carried out on a single drum forming drum. First, attach the hanging tape to the forming drum, wrap the wire rope, and attach a layer of tape to complete the forming of the embryo.

（3) Vulcanization in two ways.

a. The iron hoop pressure vulcanization is suitable for the semi-finished product formed by the die method, pressurized by the iron hoop, and then vulcanized by placing it in a vulcanization tank or a flat press.
b. The rubber sleeve vulcanization is suitable for the forming of the drum formed by the drum. The embryo with the forming drum is sleeved on the rubber sleeve and sent to the vulcanization tank, and simultaneously pressurized and heated inside and outside. The first stage is 0.3~0.4MPa vapor pressure, which is maintained for 2~3min; the second stage is further pressurized to 0.8~1MPa, and continues to the specified curing cycle.

(2) pouring method

Polyester polyurethane is used as the main material and is completed in four steps.
1 Polycondensation is carried out by using adipic acid and ethylene glycol as raw materials to obtain a dihydroxy-terminated polyester.
2 Add toluene diisocyanate to the polyester and extend the chain to form a prepolymer.
3 Vacuum and defoam the prepolymer.
4 Add the curing agent MOCA, stir evenly, and pour into the cavity with the strength layer preset. After heating, solidifying and demoulding, the finished product is obtained.

application

The synchronous toothed belt is thin and strong, and is resistant to flexing. Therefore, the transmission speed is high and the transmission efficiency is high, up to 100 kW. It is used to replace the chain or gear transmission, which can reduce noise and save lubricating oil. Therefore, it is widely used in precision machine tools, computers, chemical fiber machinery, textile machinery, automotive transmission systems and general machinery.

The V-belt is a large class of transmission tapes. It is named after the isosceles trapezoidal section. It has developed rapidly since the advent of the last century and can replace mechanical gear transmissions. The V belt is widely used for power transmission of electric motors and internal combustion engines. This is because it is continuously improved in terms of material, structure and shape, and combines many advantages such as high power, high speed, small deformation, long life and small space.

With the diversification of the use requirements, the classification of V-belts is also increasing day by day. According to the belt structure, there are edging and trimming points; according to the core structure, there are disc cores and wire cores; depending on the application, there are industries. , the agricultural machinery industry and the automotive industry; according to the shape of the broken (cut) face, there is a wide and narrow difference. According to the shape of the section, it can be divided into the following three types.

(1) ordinary V belt

The ratio of the section height/top section width of the ordinary V-belt is 0.7, and the wedge angle is 40°, which is suitable for general mechanical transmission, but is not suitable for use in automobiles and agricultural machinery. It consists of a top coat, a top coat, a strong (stretch) layer (raw curtain or cord) and a primer (compressed) layer (see Figure 6·IO). O strength layer material is divided into two types: wire and cord. The advantages of the wire structure include relatively high flexibility, no quality problems such as interlayer displacement and delamination, but the wire rope V-belt of the same specification is not as strong as the V-belt of the cord. The section specifications are divided into 0, A.E, C, D, E, F and other models from small to large.
All kinds of V belts can be made into a single root, that is, the molding to vulcanization is carried out separately, which is called a cloth type; or the cylindrical shaped embryo can be formed first, and then vulcanized and then cut into a single root, which is called a cutting belt. From the appearance, the entire body of the former is covered with a cloth without being exposed, and the sides of the latter are exposed. The production efficiency of the dicing tape is high, but the reinforcing layers on both sides are exposed, and the fiber ends are prone to disorder.

(2) Narrow V-belt

The shape parameters of the section are different from those of the ordinary: the aspect ratio of the section is 0·9, which is higher than 0.2 of the ordinary V-belt, and the appearance is obviously narrow.
This structural feature gives it the following performance characteristics:
1 higher transmission power, 0.5-1.5 times higher than the V-belt of the common structure;
2 The structure is compact and 50% smaller than the ordinary structure;
3 line speed is high, up to 40~50m∕s, suitable for high speed operation;
4 The center distance of the transmission wheel and the width of the wheel groove can be reduced to make the overall transmission system more compact.

(3) Wide V belt

The wide V-belt refers to a flat V-belt with a height/width ratio of only about 0.3. It is usually used in a belt-type transmission. Therefore, it is also called a variable-speed V-belt, which is developed rapidly due to smooth transmission, convenient maintenance, and low manufacturing cost. In order to meet the needs of shifting, the top and bottom surfaces can also be toothed to improve the engagement with the drive wheel.