new technology to produce silicone sponge without chemical blowing agents or vocs.

by:Keyuan     2020-06-20
Silicone Sponge materials are used for applications that require the benefits of silicone polymers, such as low temperature flexibility, heat resistance, UV and ozone resistance, and electrical insulation properties.
In addition, sponge rubber has the advantages of light weight, good damping effect and heat insulation.
In today\'s more competitive and demanding markets, silicone sponges offer significant cost reductions compared to compact elastic materials, as fewer materials are used as sequences with a lower proportion of sponges
Add chemical blowing agent (s)
Rubber compounds produce traditional silicon responses.
In the process of vulcanization, heating will decompose the foaming agent, produce bubbles surrounded by rubber, and form the cells of the sponge.
These traditional blowing agents may be toxic. products.
A new silicone sponge technology for closed batteries has been developed, replacing the use of traditional reactive chemical cleaning agents and volatile organic materials (VOC)
As an extension source.
This new sponge technology uses water as a foaming agent to create a uniform cellular sponge structure that can be used for food contact applications.
Performance features include: * flexibility;
* Low compression settings;
* Eliminate environmental controls related to sponge processes;
* Reduced demand for ventilation systems;
* No bad smell;
* Easy to form and squeeze;
* Smooth and uniform extrusion surface;
* Application for food contact is acceptable.
These sponge products can be enhanced with additives and modifiers.
This paper will present the technological advances, performance and performance features of rubber manufacturers and end users, as well as the potential benefits of silicon sponges.
Sponge rubber can be open or closed.
The cell structure is defined by opening a link to the area (open cell)
Or the individual properties of the sponge structure opening (closed cell).
Silicone rubber can be made into a sponge by using a foamer in an open or closed cell structure.
These foaming agents create bubbles when heated to develop the cell structure, while the vulcanization reaction occurs on the cross-junction of the rubber.
Hamilton summarizes the physical and cost-effectiveness of using an expanded sponge (ref. 1).
In addition to the lower sealing pressure, shape consistency and lower density and weight, silicone sponge rubber provides enhanced temperature range applicability (from -60[degrees]
Cto 250C for long-
Performance of the term and up to 400 [degrees]C for short-Regular application).
This provides a wider range of operating temperatures compared to organic rubber sponges.
Traditionally, silicone sponge rubber is produced using an Peroxide curing system with a foamer that can release toxic substancesproducts.
Food grade silicone sponges are possible in some cases, but these materials may be affected by process constraints and poor performance, including compression sets and densities.
New technology silicone sponge rubber is cured with platinum (addition cure)
Water is used as a blowing medium.
This new technology provides consistent cell structure, odor-free sponge manufacturing, uniform surface of parts and stable process conditions.
Silicone Sponge rubber is widely used.
Some of the more common include car washers for sealing compartments, as well as office equipment rollers used in copiers, printers, and fax machines.
Consumer uses requiring food access to safety materials include electrical seals for dishwashers and ovens and lunch boxes for transporting food.
When solid rubber produces excessive sealing or matching force, priority is given to the use of silicone rubber sponge rubber, reducing the density can reduce the cost of the overall material, the need for heat insulation, irregular surface contact with the corresponding rubber seal, includes insulation, sponge washers, plates, fillers, rollers and extruded profiles.
Sponge technology traditionally, silicone sponge rubber is produced by adding chemical cleaning agents to the rubber formula.
Chemical blow molding agents break down under heating conditions for curing rubber.
The resulting gas (
Nitrogen is the most common)
Provides batteries or bubbles generated when hot rubber is cross-linked during parallel processes.
2,2 azobisisobutyronitrile (AIBN)
Commonly used as nitrogen-
High consistency silicone rubber sponge rubber cured with peroxide produces chemical cleaning agent.
While the sponge structure produced by this technology is satisfactory in terms of consistency and cell size, a major drawback is the generation of toxic and eco-friendly-
Product, teramethylsuccionitryl.
This has been considered as a major limiting factor in the rubber manufacturing industry for the use of silicone sponges, non-
Products that need toxic and environmental protection.
Other chemical blow molding agents with less risk can also be provided.
Diammonium dinitro (DNPT)
And even killing amine (ADCA)
It is two foaming agents with lower toxicity, but because of their use, the cell structure is poor and the physical performance is not consistent.
Recently, another manufacturer reported on the development of silicone sponges using hollow fillers based on ceramic or organic materials (ref. 2).
The second manufacturer reported the use of flexible microbeads as a means of obtaining sponge structures (ref. 3).
However, Dow Corning\'s sponge rubber technology is based on silicone.
The new technology uses water as a blow, not a chemical that breaks down.
In addition, the system uses proprietary silicone technology that supports waterto-
Steam blistering leads to regular and consistent cell structure.
When heated, water dispersed in the silicone rubber matrix creates bubbles, resulting in a uniform bubble structure.
The new sponge technology allows to change the temperature conditions of the manufacturing process to achieve the desired volumetric expansion properties.
As shown in Figure 1, where the curing/sponge temperature is increased from 200 [degrees]C to 250[degrees]
C, resulting in a decrease in specific gravity and hardness. [
Figure 1 slightly]
The final result of this new sponge technique is a consistent cellular structure that can be adjusted to change the volume expansion.
This allows manufacturers to control specific gravity using curing/sponge temperatures.
Figure 2 The new silicone sponge technology was compared with the traditional sponge using a chemical cleaning agent.
This technique provides a homogeneous and finely segmented cell structure. [
Figure 2:
The new silicone sponge technology eliminates the use of chemical blow molding agents and potentially dangerous by-products.
Therefore, this material has no obvious smell and can be treated with less ventilation than the traditional sponge material.
The new technology sponge consists of three parts.
These components are HB-
AMS-ES 5000 sponge base
5000 sponge care andAMS-
5001 sponge surface modifier.
This system gives manufacturers the flexibility to choose to mix their own finished compounds using three materials, or to use finished compounds from Dow directly.
These three materials can be used separately, or other silicone substrates can be formulated with these system components to create sponges with different density and compression deflection.
This provides manufacturers with simple formula control and process flexibility to produce a variety of sponge products to meet different end-use requirements.
There are many industry specifications for the control and classification of flexible cellular rubber products.
In this article, we have tested and compared this new sponge material with several widely used industry specifications, to demonstrate the ability of this new system to flexibly meet the various requirements commonly required by the corresponding rubber manufacturing industry.
Table 1 summarizes the industry specifications that can be used to evaluate the technical performance of this new silicone sponge.
Table 2 details the test results of this new sponge technology compared to previously determined industry specification elements.
Three sponge recipes are listed in Thistable.
* A consists of three system components;
* B consists of three system components and 12.
5 parts of PX silicone rubber (
70 hardness);
And * C is a silicone rubber base consisting of three system components and 25 parts of PX (
70 hardness).
Sponge sample extrusion, hot air vulcanization for 10 minutes at240 【degrees]
C and post in 200 [cure for 4 hoursdegrees]C.
The results show that a certain range of compression
Specific goals can be achieved with simple recipe adjustments.
In addition, previous discussions about the change of sponge specific gravity with curing/sponge temperature show that compression-
The deviation may also vary as the process temperature is adjusted.
This may be because the addition curing system used in this new technology sponge is able to solidify the rubber at a certain temperature range.
Therefore, through simple formula adjustment and process temperature control, manufacturers using the Silastic sponge system can meet various sponge requirements.
The curing system and water blowing agent have no odor, uniform sponge, small cell structure, smooth and non-stick surface.
The new sponge technology can be used for food grade and low compression devices when properly cured (
Deflection at 25% and 50%)applications.
Sponge manufacturing extrusion the same extrusion machinery and curing equipment for standard silicone extrusion can also be used in this new silicone sponge technology.
The stock temperature of the screw tip should be 25 [degrees]to50[degrees]
C, so it is recommended to cool down a little.
The shape of the mold should reflect the linear expansion rate of the silicone rubber sponge at 1. 45 to 1.
65 compared with solid materials (
The volume increased by three times. 2 to 4.
4, depending on the curing conditions).
Mold geometry needs to be adjusted to compensate: * mold expansion of solid material (figure 3);
And * The Corner area expanded due to rapid heat transfer is less than the straight line area of the profile (
As shown in figure 4, the additional convex shape of the area shown as straight on the profile cross section). [
Figure 4 slightly]
The extrusion speed that can be achieved depends on the geometry of the profile and the ability of the equipment (
Length and efficiency of heat transfer in curing tunnel).
The control of the curing temperature depends to a large extent on the heating equipment used.
The curing temperature of the new sponge technology should be higher than that of the traditional chemical blowing sponge.
The higher the curing temperature, the lower the density.
The temperature of the tunnel opening should exceed 210 [degrees]
C get a good sponge.
The optimal conditions will be based on the combination of the size, shape, profile thickness and quantity and length of the curing furnace.
Sponge moldingA pre
The shape of enough shape should be inserted into the mold, leaving enough space to fill the mold and get the desired shape. The pre-
The shape weight is usually determined by teststo to determine the optimal quantity to provide full mold filling.
The density of the resulting molded sponge parts is affected by the geometry of the mold.
Mold temperature 200-250[degrees]
Typical curing time is 60 seconds per mm part thickness.
The processing advantages of the new technology sponge include the ability to use it during molding and extrusion processing, the addition of curing provides a more eco-friendly process, and the use of non-
Toxic foaming agents reduce the harm of environmental and personnel exposure.
Conclusion new technology silicone sponge eliminates the use of chemical cleaning agent and its potential dangerous decompositionproducts.
Take water as the foaming agent, add the curing material to make the rubber vulcanization.
This new sponge technology brings the following benefits: * can be used for food contact applications;
* No bad smell during processing;
* Reduced process ventilation requirements;
* The structure of sponge cells is uniform and fine; * smooth, non-
Sticky sponge surface;
* Control sponge properties by simple recipe or process temperature change.
The data shows available elastic, compression deflection, density, and compression sets to allow manufacturers to meet the requirements of the silicone sponge primary industry specifications.
There are three silicone sponges.
Component systems that provide flexibility for manufacturers by allowing manufacturers to choose to mix their own compounds or use finished compounds directly from Dow Corning. References(1. )J. R.
228 rubber world Hamilton II3, 35 (June 2003). (2. )S. Sekiguchi, S.
Hirabayashi and N.
\"New Silicone Sponge\", 3rd International silicone conference, Cleveland, Ohio (2003). (3. )D.
Klingberg and B.
Griffin, \"a new method for the manufacture of silicone rubber sponges\", 3rd International Silicon Conference, Cleveland, Ohio (2003). (4. )
ASTM standard D1056-
00, \"Standard Specification for flexible honeycomb materials--
\"Sponge or expanded rubber . \"BookASTM Stand. 08. 01, 1 (2000). (5. )
ASTM standard D6576-
00, \"Standard Specification for chemical blowing of flexible honeycomb rubber\", Annu.
Book ASTM stand. 08. 03, 1 (2000). (6. )
AMS 3195E, \"silicone rubber sponge closed battery, medium\", SAE, 1 (1996). (7. )
AMS Saff, \"sponge, silicone rubber, enclosed battery, firm\", SAE, 1 (2001).
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