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Plasticizers- Phthalic Acid Esters and Phthalic anhydride

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Plasticizers, not only to Phthalic Acid Esters and Phthalic anhydride but a wide variety and kinds, are often added to a lot of engineering and modern polymers and general plastics to improve their process ability, improve their flow ability and injection molding characteristics and also to improve their elasticity or reduce brittleness in them. The form in which plastics are used before injection molding is short pellets, which seem to have been cut out from a long wire extruded shape. To actually mold these plastics, the injection molding machine and its operator need to perform a lot of tasks, such as mounting the mold on injection machine with the help of a crane, screwing the mold onto the machine and then clamping it securely, feeding the properly dried plastic material to the hopper unit. From there onwards setting the injection parameters into the screen, which range from the opening closing distance of the mold with differential high and low pressures, setting the screw velocities and screw displacements, setting of the heating units of the screw to proper temperatures and then molding parts.

Below is a picture of a cute kid playing with flexible plastic toy.

Anyhow, in today’s post, our main motive is to study about plasticizers, and not injection molding. So lets begin by discussing what are plasticizers and why are they added to plastics. The basic understanding about uses of plasticizing will provide us with a good base to understand Phthalic Acid Esters and Phthalic anhydride more clearly.
Plasticizers are organic substances of low volatility that are added to plastics compounds to improve their flexibility, extensibility, and  processability. They increase flow and thermoplasticity of plastic materials by decreasing the viscosity of polymer melts, the glass transition temperature (Tg) the melting temperature, and the elasticity modulus of finished products.

Plasticizers are particularly used for polymers that are in a glassy state at room temperature. These rigid polymers become flexible by strong interactions between plasticizer molecules and chain units, which lower their brittle-tough transition or brittleness temperature (Tb) (the temperature at which a sample breaks when struck) and their Tg value, and extend the temperature range for their rubbery or viscoelastic state behavior.

Side Note: In this regards, Preparation of aniline and itaconic anhydride may be something I will ike to discuss in my coming posts. Also, I will try to provide maximum information on synthesis of alcohols, synthesis of acetanilide and synthesis of alkenes. Plastic making is similar to production of acids and some chemicals in many regards. So to understand it completely, we also need to look more into methods such as oxidation of benzaldehyde, 4-bromotoluene, preparation of amides, preparation of aldehydes, synthesis of amines, phenylacetyl chloride and such similar processes which are in really high demand today.

Mutual miscibility between plasticizers and polymers is an important criterion from a practical point of view. If a polymer is soluble in a plasticizer at a high concentration of the polymer, the plasticizer is said to be a primary plasticizer. Primary plasticizers should gel the polymer rapidly in the normal processing temperature range and should not exude from the plasticized material. Secondary plasticizers, on the other hand, have lower gelation capacity and limited compatibility with the polymer. In this case, two phases are present after plasticization process—one phase where the polymer is only slightly plasticized, and one phase where it is completely plasticized. Polymers plasticized with secondary plasticizers do not, therefore, deform homogeneously when stressed as compared to primary plasticizers.
The deformation appears only in the plasticizer-rich phase and the mechanical properties of the system are poor. Unlike primary plasticizers, secondary plasticizers cannot be used alone and are usually employed in combination with a primary plasticizer.

Plasticizer properties are determined by their chemical structure because they are affected by the polarity and flexibility of molecules. The polarity and flexibility of plasticizer molecules determine their interaction with polymer segments. Plasticizers used in practice contain polar and nonpolar groups, and their ratio determines the miscibility of a plasticizer with a given polymer.
Plasticizers for PVC can be divided into two main groups according to their nonpolar part. The first group consists of plasticizers having polar groups attached to aromatic rings and is termed the polar aromatic group. Plasticizers such as phthalic acid esters and tricresyl phosphate belong to this group. An important characteristic of these substances is the presence of the polarizable aromatic ring. It has been suggested that they behave like dipolar molecules and form a link between chlorine atoms belonging to two polymer chains or to two segments of the same chain.
Plasticizers belonging to this group are introduced easily into the polymer matrix. They are characterized by ability to produce gelation rapidly and have a temperature of polymerplasticizer miscibility that is low enough for practical use. These plasticizers are therefore called solvent-type plasticizers, and their kerosene extraction (bleeding) index is very low. They are, however, not recommended for cold-resistant materials.

The picture below shows the percentage use of various plasticizers world-wide

The second group consists of plasticizers having polar groups attached to aliphatic chains and is called the polar aliphatic group. Examples are aliphatic alcohols and acid or alkyl esters of phosphoric acid (such as trioctyl phosphate). Their polar groups interact with polar sites on polymer molecules, but since their aliphatic part is rather bulky and flexible other polar sites on the polymer chain may be screened by plasticizer molecules. This reduces the extent of intermolecular interactions between neighboring polymer chains.
Polar aliphatic plasticizers mix less well with polymers than do polar aromatics and, consequently, may exude (bloom) from the plasticized polymer more easily. Their polymer miscibility temperature is higher than that for the first group. These plasticizers are called oil-type plasticizers, and their kerosene extraction index is high. Their plasticization action is, however, more pronounced than that of polar aromatic plasticizers at the same molar concentration. Moreover, since the aliphatic portions of the molecules retain their flexibility over a large temperature range, these plasticizers give a better elasticity to finished products at low temperature, as compared to polar aromatic plasticizers, and allow the production of better cold-resistant materials. In PVC they also cause less coloration under heat exposure.
In practice plasticizers usually belong to an intermediate group. Mixtures of solvents belonging to the two groups discussed above are used as plasticizers to meet the requirements for applications of the plasticized material.
Plasticizers can also be divided into groups according to their chemical structure to highlight their special characteristics. Several important plasticizers in each group (with their standard abbreviations) are cited below.

Phthalic Acid Esters and Phthalic anhydride

Di(2-ethyl hexyl) phthalate (DOP) and diisooctyl phthalate (DIOP) are largely used for PVC and copolymers of vinyl chloride and vinyl acetate as they have an affinity to these polymers, produce good solvation, and maintain good flexibility of finished products at low temperature. The use of n-octyl-ndecyl phthalate in the production of plastics materials also allows good flexibility and ductility at low temperature. Diisodecyl phthalate (DDP), octyl decyl phthalate (ODP), and dicapryl phthalate (DCP) have a lower solvency and are therefore used in stable PVC pastes. Butyl octyl phthalate (BOP), butyl decyl phthalate (BDP, and butyl benzyl phthalate (BBP) have a good solvency and are used to adjust melt viscosity and fusion time in the production of high-quality foams. They are highly valued for use in expandable plasticized PVC.
Dibutyl phthalate (DBP) is not convenient for PVC plasticization because of its relatively high volatility. It is a good gelling agent for PVC and vinyl chloride-vinyl acetate copolymer (PVCA) and so is sometimes used as a secondary plasticizer in plasticizer mixers to improve solvation. DBP is mainly used for cellulose-based varnishes and for adhesives. It has a high dissolving capacity for cellulose nitrate (CN).
Dimethyl phthalate (DMP) also has high dissolving capacity for CN. It has good compatibility with cellulose esters and are used in celluloid made from CN and plastic compounds or films made from other cellulosic polymers, cellulose acetate (CA), cellulose acetate-butyrate (CAB), cellulose acetate-propionate (CAP), and cellulose propionate (CP). It is light stable but highly volatile. Diethyl phthalate (DEP) possesses properties similar to DMP and is slightly less volatile.

So that it all that is to Phthalic Acid Esters and Phthalic anhydride, which are widely used as Plasticizers for various high grade plastics. Of course, I had to prepare a lot of information about these in general so you can understand these two better.

I know I am not a master in this field as my primary field of expertise is Injection Molding Troubleshooting. So if you find any mistakes, then point them out and leave me comments below, I will correct them so other readers do not face same problems as you did. Remember to bookmark Molding Plastic Components  and keep checking periodically for more updates on Plastic Injection Mold Design.

Precision Plastic Injection Molding

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Precision Plastic Injection Molding is fast gaining a huge importance in the modern manufacturing industry as Precision molded products are replacing their metallic counterparts at a rapid speed. Metallic components are not only expensive, but also have longer lead times, shorter cycle times and are a few times more expensive than plastic parts. So precision injection molded plastics possess a clear advantage over other materials such as precision molded rubber or castings for the reasons mentioned above.
The company I work for, Kyowa Plastics Japan, had set up its own precision plastic injection mould facility around 6 years back. The technical expertise of our Engineering staff, with faculty possessing over 30 years of experience in Plastic Injection molding, has helped us to become the number one in precision injection molding field in the whole South China territory.
Our company expanded into China with a Globalist approach and a positive frame of mind around 20 years ago. Since then it has never looked back. The huge support and trust from large International and Japanese companies such as Honda, Nypro, Brother, Pioneer, Fuji Xerox and Flextronics to name a few, have given us tremendous exposure in the manufacturing field of precision plastics in the recent years. We have monopolized in the production of Auger units for Printer parts, digital camera lens assemblies for the mobile phone and miniature cameras, including the Yoke assemblies, lens assemblies and similar high precision parts, which requires tolerances to be maintained within a couple of microns, not only for the tooling or the plastic mold testing, but also during the actual production stage.

We now have Flexible Manufacturing Systems (FMS) facilities in Hongkong(Office), Shenzhen- South China(Complete manufacturing facility), Dalian- North China (Complete manufacturing facility) and Japan. In case you have any queries related to the Precision Plastics manufacturing, you can call me at (0081)8024132781 or send me a mail at abhinav-m at kyowajpn. co. jp, please change at to @ and remove the spaces after “jpn” and “.co.”. I have done so to prevent the spambots from getting access to my email. I usually respond within 24 hours and will give you a complete feedback about what you may expect from the type of work you want to get done.
Sure, there are many companies that furnish precision molded rubber as well, but we are currently limited to Precision Plastic Injection Molding only and will therefore be able to reply you with queries related to Precision Plastic work only.
With the recent advancements in the manufacturing field, which include in mold labelling, in mold decoration, custom gas assisted injection molding, and super fast cycle time moldings (Injection time below 4 seconds), there is no doubt in my mind that Precision Plastic Injection Molding will continue to dominate the manufacturing industry and replace more and metal parts in the coming future as well.

Thermoplastics and Thermosetting plastics

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A lot of molding engineers and technical university students are left wanting for the knowledge about Thermoplastics and Thermosetting plastics differences. If you have  been looking for some similar information, then worry no more, this post is going to explain everything in detail. By the way, I would really appreciate some sort of feedback from you after you finish reading this post on Polymer Types and Processes used for the manufacturing for each of these. Do not feel shy to leave a little comment at the bottom of this post by using the comment form. If you really like this post, then please remember to share it on your Facebook and other social accounts. Buttons are provided below the article for this purpose, just press the button as a way to thank me for this post. If you are just starting out and have no idea about plastics and polymers, then read the post What Is A Polymer before reading this post.

All thermoset plastics are self-extinguishing. Among thermoplastics, nylon, polyphenylene oxide, polysulfone, polycarbonate, poly(vinyl chloride), chlorinated polyether, poly(chlorotrifluoroethylene) and fluorocarbon polymers have self-extinguishing properties. Compression and transfer molding are the most common methods of processing thermosetting plastics. For thermoplastics, the more important processing techniques are extrusion, injection, blow molding, and calendaring; other processes are thermoforming, slush molding, and spinning. More recently, modified machinery and molding compositions have become available to provide the economics of thermoplastic processing to thermosetting materials. Injection molding of phenolics and other thermosetting materials are such examples. Nevertheless, it is still a widespread practice in industry to distinguish between thermoplastic and thermosetting resins.
Compression and transfer molding are the most common methods of processing thermosetting plastics. For thermoplastics, the more important processing techniques are extrusion, injection, blow molding, and calendaring; other processes are thermoforming, slush molding, and spinning.
The image below should give you a fairly good idea of what is the difference between Thermoplastics and Thermosetting plastics on base of their linking structures.

Thermoplastic resins consist of long polymer molecules, each of which may or may not have side chains or groups. The side chains or groups, if  present, are not linked to other polymer molecules (i.e., are not cross-linked). Thermoplastic resins, usually obtained as a granular polymer, can therefore be repeatedly melted or solidified by heating or cooling. Heat softens or melts the material so that it can be formed; subsequent cooling then hardens or solidifies the material in the given shape. No chemical change usually takes place during this shaping process.
In thermosetting resins the reactive groups of the molecules from cross-links between the molecules during the fabrication process. The cross-linked or “cured” material cannot be softened by heating.
Thermoset materials are usually supplied as a partially polymerized molding compound or as a liquid monomer–polymer mixture. In this uncured condition they can be shaped with or without pressure and polymerized to the cured state with chemicals or heat.
With the progress of technology the demarcation between thermoplastic and thermoset processing has become less distinct. For thermosets processes have been developed which make use of the economic processing characteristics or thermoplastics. For example, cross-linked polyethylene wire coating is made
by extruding the thermoplastic polyethylene, which is then cross-linkedd (either chemically or by irradiation) to form what is actually a thermoset material that cannot be melted again by heating.
New plastics, such as the Grilamid TR90, are being developed everyday. As a result the manufacturing industry is accepting both Thermoplastics and Thermosetting plastics into the Plastic Injection Mold Design for Molding Plastic Components. Make sure that you bookmark the site to get updated information for various polymers.

Grilamid TR 90 and Grilamid TR 55-Clear Plastics(Transparent)

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Recently we have been searching for some clear plastics which have high strength and can maintain good transparency even when wall thickness is relatively large. We were unable to find a good material which could fit our Plastic Design specifications of high stress crack resistance and has a good color blend ability in spite of being transparent. This is where we came across Grilamid TR90 and Grilamid TR55. Both these transparent plastic grades are excellent polyamide thermoplastics which possess the qualities of an engineering polymer, although they are transparent. We have added them into our list of the chosen resins for Electrical parts, electronic parts, car parts and other automobile parts and other similar applications in domestic appliances.
The technical data sheet of Grilamid, both TR90 and TR 55 provides us with essential properties that Grilamid possesses, and renders it as the best choice of transparent material. I have often seen a lot of clear plastic parts cracking and bending too much, but Grilamid has got rid of this problem in transparent plastic processing.

Now I will provide you with a few basic runner and gating
design guidelines for Grilamid injection molding processing that should be incorporated into tooling and molds. Although this information is available freely on the Grilamid website, I though it would be good to share it here to save time of those reading this article. To achieve an optimal mold-fill and to avoid sink marks, a central gate at the thickest section of the moulding is recommended. Pin point gate  (direct) or tunnel gates are more economical and more common with technical molding.
To avoid premature solidification of the melt and difficult mould filing, the following points should be considered:
Gate Diameter: 0.8 x thickest wall section of the injection molding part
Runner Diameter: 1.4 x thickest wall section of the injection molding part (but minimum 4 mm)
The drying time for Grilamid is a bit long, which is understandably so, as most of the clear resins require a long drying time to avoid bubbles and air traps due to moisture. It needs a Desiccant dryer and the drying time needs to be over 5 hours with a temperature of 80 degrees Celsius. If you use a vacuum oven, you need to dry it for at least 8 hours at the same temperature.
Will continue with this post later when we actually mold the Grilamid part to update with the optimum injection and processing conditions on our plastic processing equipment. Make sure that you bookmark the site to get updated information on Plastic Injection Mold Design for various polymers.

Plastic Processing Equipment

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As discussed in our previous article on Polymer Testing Equipment, plastic is fast becoming the most popular choice of material in manufacturing industries. As many readers have been asking me to give some details about Plastic Processing Equipment and methods, I took out time to inform our readers about the various methods involved in procuring finished plastic parts.
The family of polymers is extraordinarily large and varied. There are, however, some fairly broad and basic approaches that can be followed when designing or fabricating a product out of polymers or, more commonly, polymers compounded with other ingredients. The type of fabrication process to be adopted depends on the properties and characteristics of the polymer and on the shape and form of the final product.
In the broad classification of plastics there are two generally accepted categories: thermoplastic resins and thermosetting resins.

Thermoplastic resins consist of long polymer molecules, each of which may or may not have side chains or groups. The side chains or groups, if present, are not linked to other polymer molecules (i.e., are not cross-linked). Thermoplastic resins, usually obtained as a granular polymer, can therefore be repeatedly melted or solidified by heating or cooling. Heat softens or melts the material so that it can be formed; subsequent cooling then hardens or solidifies the material in the given shape. No chemical change usually takes place during this shaping process.
In thermosetting resins the reactive groups of the molecules from cross-links between the molecules during the fabrication process. The cross-linked or “cured” material cannot be softened by heating.
Thermoset materials are usually supplied as a partially polymerized molding compound or as a liquid monomer–polymer mixture. In this uncured condition they can be shaped with or without pressure and polymerized to the cured state with chemicals or heat.
With the progress of technology the demarcation between thermoplastic and thermoset processing has become less distinct. For thermosets processes have been developed which make use of the economic processing characteristics or thermoplastics. For example, cross-linked polyethylene wire coating is made by extruding the thermoplastic polyethylene, which is then cross-linked (either chemically or by irradiation) to form what is actually a thermoset material that cannot be melted again by heating.
More recently, modified machinery and molding compositions have become available to provide the economics of thermoplastic processing to thermosetting materials. Injection molding of phenolics and other thermosetting materials are such examples. Nevertheless, it is still a widespread practice in industry to distinguish between thermoplastic and thermosetting resins.
Compression and transfer molding are the most common methods of processing thermosetting plastics. For thermoplastics, the more important processing techniques are extrusion, injection, blow molding, and calendaring; other processes are thermoforming, slush molding, and spinning.
Tooling for plastics processing defines the shape of the part. It falls into two major categories, molds and dies. A mold is used to form a complete three-dimensional plastic part. The plastics processes that use molds are compression molding, injection molding, blow molding, thermoforming, and reaction injection molding (RIM). A die, on the other hand, is used to form two of the three dimensions of a plastic part. The third dimension, usually thickness or length, is controlled by other process variables.
The plastics processes that use dies are extrusion and thermoforming. Many plastics processes do not differentiate between the terms mold and die. Molds, however, are the most predominant form of plastics tooling.
Types of Molds for Plastic Processing Equipment




The basic types of mold, regardless of whether they are compression, injection, transfer, or even blow molds, are usually classified by the type and number of cavities they have. For example, Figure below illustrates three mold types: (a) single-cavity, (b) dedicated multiple-cavity, and (c) family multiple cavity.
Single-cavity mold represents one of the simplest mold concepts. This design lends itself to low-volume production and to large plastic part designs. The multiple-cavity molds may be of two types. A dedicated multiple-cavity mold has cavities that produce the same part. This type of mold is very popular because it is easy to balance the plastic flow and establish a controlled process. In a family multiple-cavity mold , each cavity may produce a different part. Historically, family mold designs were avoided because of difficulty in filling uniformly; however, recent advances in mold making and gating technology make family molds appealing. This is the case especially when a processor has a multiple-part assembly and would like to keep inventories balanced.
Not: You might want to check out for a complete article on Injection Molding Troubleshooting and get some important Plastic Injection Mold Design and Process Tips to guard against the problems that might appear when Molding Plastic Components .
Types of Dies for Plastic Processing Equipment
Within the plastics industry, the term die is most often applied to the processes of extrusion (see EXTRUSION). Extrusion dies may be categorized by the type of product being produced (e.g., film, sheet, profile, or coextrusion), but they all have some common features as described below.
1. Steel. The extrusion process being continuous, both erosion and corrosion are significant factors.
Hence the dies must be made of a high-quality tool steel, hardened so that the areas that contact the plastic material do not erode. Additionally, many dies have a dense, hard chrome plating in the area where plastic melt contacts the die.
2. Heaters. Extrusion dies are to be heated in order to maintain a melt flow condition for the plastic material. Most of the heaters are cartridge-type elements that slip fit into the die at particular locations. In addition to the heaters, the dies have to accommodate temperature sensors, such as thermocouples.
3. Melt Pressure. Many sophisticated dies are equipped with sensors that monitor melt pressure. This allows the processor to better monitor ad control the process.
4. Parting Line. Large extrusion dies must be able to separate at the melt flow line for easier fabrication and maintenance. Smaller extrusion dies may not have a parting area, because they can be constructed in one piece.
5. Die Swell Compensation. The polymer melt swells when it exits the die, as explained previously.
This die swell is a function of the type of plastic material, the melt temperature, the melt pressure, and the die configuration. The die must be compensated for die swell so that the extruded part has the corrected shape and dimensions. Molds and dies for different fabrication processes will be
described later in more detail when the processes are discussed in coming posts on our site.
This concludes our informative post on Plastic Processing Equipment and you should have a clear idea about it by now. If you have any doubts then read the post again. In case of more queries, contact me and I will answer you as ASAP. Also, feel free to add comments below to get answers quickly and help others. For more informative posts on Plastic Injection Mold Design, be sure to bookmark this page and check back regularly.

Plastic Design

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Plastic design is a highly specialized area of designing where continuous improvements are necessary to get high quality and low price plastic products. As polymer manufacturing is becoming the major source of our daily use necessities, this is one field of design engineering that cannot be ignored. We see the same sort of approach being applied in plastic part designing and mold tool designing, over and over again. This means that the progress in designing and manufacturing is a real minimum, where most of the companies are just concerned with getting the parts at the lowest costs. But they tend to forget that advancements in technology involves the investment of time and money for one time only, and after the research part has been completed, it reaps benefits for the whole industry for coming years. So it is essential that the manufacturing giants get together and start thinking about advancing the injection mold designs and polymer part designs. This will help all the smaller industries to follow the Plastic Design Guidelines and implement them in their system.


I personally believe that Plastic Design is a field where the mold designer working on a new part design can save time and locate the areas that require real work, i.e., innovation, with the help of his vast experience in similar design projects. He can see how others have faced and solved similar problems, while he can evaluate their results and create something even better ~ instead of “reinventing the typewriter”. One basic requirement to be met by every mold intended to run on an automatic injection molding machine is this: the molded part has to be ejected automatically and not require subsequent finishing (degating, machining to final dimensions, etc.)
For practical reasons, injection molds are best classified according to both the major design features of the molds themselves and the molding-operational features of the molded parts. These include the:

1. type of gating/runner system and means of separation .
2. type of ejection system for molded parts.
3. presence or absence of external or internal undercuts on the part to be molded.
4. the manner in which the molded part is to be released.

Important to note here that the final mold design cannot be prepared until the part design has been specified and all requirements affecting the design of the mold have been clarified. So Plastic Part Design directly determines the lead time of the whole project as well.

Types of Injection Mold Designs
There are Various types of designs which are used depending on the situation we want to use these molds in and the type of plastic components we want to produce. These may be listed as:

1. standard molds (two-plate molds)
2. split-cavity molds (split-follower molds)
3. stripper plate molds
4. three-plate molds
5. stack molds
6. hot runner molds

In normal conditions, injection molds are used in the manufacturing of following types of raw plastic materials:

1. thermoplastics
2. thermosets
3. elastomers

Just recently, elastomer injection machines have been introduced in the market and inspite of a few restrictions, they are really beating conventional elastomer molding processes by offering a lots of competitive cost advantages.
having stated that, lets describe the above mold types by their functional use. Cold runner molds for runnerless processing of thermosetting resins in analogy to the hot runner molds used for processing thermoplastic compounds and elastomers.
Runner Layout guidelines
Sometimes runners cannot be located in the mold parting plane, or each part in a multi-cavity mold has to be center-gated. In such cases, either a second parting line (three-plate mold) is required to remove the solidified runner, or the melt has to be fed through a hot runner system. In stack molds, two or more molds are mounted back-to-back in the line of closing, but without multiplying the required holding force. The prerequisite for such solutions is large numbers of relatively simple, e.g., flat molded parts, and their attractiveness comes from reduced production costs. Today’s stack molds are exclusively equipped with hot runner systems that have to meet strict requirements, especially those involving thermal homogeneity.
Conclusion to Plastic Design Guidelines
Although it is not possible to cover all the complexities and instructions related to injection mold design and plastic parts designing in this single tutorial, I will split them up into smaller and easy to read in the next few weeks and lay them out in the form of injection mold design tutorials.

Polymer Testing Equipment

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In today’s article, we will be discussing an important part of materials development and proper materials selection, i.e., testing and standardization of polymers with the Polymer Testing Equipment. The latter part of this article is therefore devoted to this aspect. It presents schematically (in simplified form) a number of standard test methods for plastics, highlighting the principles of the tests and the properties measured by them.

There are two stages in the process of becoming familiar with plastics. The first is rather general and involves an introduction to the unique molecular structures of polymers, their physical states, and transitions which have marked influence on their behavior. These have been dealt with in article “What is a Polymer”. The second stage, which will be treated in this article, is more specific in that it involves a study of the specific properties of plastics which dictate their applications.

Besides the relative ease of molding and fabrication, many plastics offer a range of important advantages in terms of high strength/weight ratio, toughness, corrosion and abrasion resistance, low friction, and excellent electrical resistance. These qualities have made plastics acceptable as materials for a wide variety of engineering applications. It is important therefore that an engineer be aware of the performance characteristics and significant properties of plastics.
In this article plastics have been generally dealt with in respect to broad categories of properties, namely, mechanical, electrical, thermal, and optical. In this treatment the most characteristic features of plastic materials have been highlighted.

Testing for Mechanical Properties Of Plastic
Several unfamiliar aspects of material behavior of plastic need to be appreciated, the most important probably being that, in contrast to most metals at room temperature, the properties of plastics are time dependent [1-4]. Then superimposed on this aspect are the effects of the level of stress, the temperature of the material, and its structure (such as molecular weight, molecular orientation, and density). For example, with polypropylene an increase in temperature from 20 to 608C may typically cause a 50% decrease in the allowable design stress. In addition, for each 0.001 g/cm3 change in density of this material there is a corresponding 4% change in design stress. The material, moreover, will have enhanced strength in the direction of molecular alignment (that is, in the direction of flow in the mold) and less in the transverse direction.
Because of the influence of so many additional factors on the behavior of plastics, properties (such as modulus) quoted as a single value will be applicable only for the conditions at which they are measured.
Properties measured as single values following standard test procedures are therefore useful only as a means of quality control. They would be useless as far as design in concerned, because to design a plastic component it is necessary to have complete information, at the relevant service temperature, on the timedependent behavior (viscoelastic behavior) of the material over the whole range of stresses to be experienced by the component.

Testing for Stress and Strain limits of Polymers
Any force or load acting on a body results in stress and strain in the body. Stress represents the intensity of the force at any point in the body and is measured as the force acting per unit area of a plane. The deformation or alteration in shape or dimensions of the body resulting from the stress is called strain. Strain is expressed in dimensionless units, such as cm/cm, in./in., or in percentage.
Corresponding to the three main types of stress?tensile, compressive, and shear?three types of strain can be distinguished.
1. Tensile strain is expressed as elongation per unit length
2. Compressive strain as contraction per unit length
3. Shear strain

That is the end of our discussion about “Polymer Testing Equipment” and you should have a fairly good idea about the various aspects involved in Polymer Testing and the sort of Equipment required to carry it out. If you have any tips or suggestions that you think might be useful for other Plastic Injection Molding Design or Processing related engineers, then do mention them so all can benefit from them. Leave a comment below for such design or processing tips.

What Is A Polymer- Polymer Engineering Solutions

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A lot of plastic and polymer processing engineers often want to know what is a polymer. In an easy to understand engineer’s language, polymer is described as a material that is capable of flowing through the mold runner and gates to take a defined shape, when heated to a temperature, which is more than its melting point. To describe in the engineer’s language: A molecule has a group of atoms which have strong bonds among themselves but relatively weak bonds to adjacent molecules. Examples of small molecules are water (H2O), methanol (CH3OH), carbon dioxide, and so on. Polymers contain thousands to millions of atoms in a molecule which is large; they are also called macromolecules. Polymers are prepared by joining a large number of small molecules called monomers. Polymers can be thought of as big buildings, and monomers as the bricks that go into them.

Monomers are generally simple organic molecules containing a double bond or a minimum of two active functional groups. The presence of the double bond or active functional groups act as the driving force to add one monomer molecule upon the other repeatedly to make a polymer molecule. This process of transformation of monomer molecules to a polymer molecule is known as polymerization. For example, ethylene, the prototype monomer molecule, is very reactive because it has a double bond.

Under the influence of heat, light, or chemical agents this bond becomes so activated that a chain reaction of self-addition of ethylene molecules is generated, resulting in the production of a high-molecular weight material, almost identical in chemical composition to ethylene, known as polyethylene, the polymer of ethylene (Please refer to the Figure above). The difference in behavior between ordinary organic compounds and polymeric materials is due mainly to the large size and shape of polymer molecules. Common organic materials such as alcohol, ether, chloroform, sugar, and so on, consist of small molecules having molecular weights usually less than 1,000. The molecular weights of polymers, on the other hand, vary from 20,000 to hundreds of thousands.

The name polymer is derived from the Greek poly for many and meros for parts. A polymer molecule consists of a repetition of the unit called a mer. Mers are derived from monomers, which, as we have seen for ethylene, can link up or polymerize under certain conditions to form the polymer molecule. The number of mers, or more precisely the number of repetitions of the mer, in a polymer chain is called the degree of polymerization (DP). Since the minimum length or size of the molecule is not specified, a relatively small molecule composed of only, say, 3 mers might also be called a polymer. However, the term polymer is generally accepted to imply a molecule of large size (macromolecule). Accordingly, the lower molecular- weight products with low DP should preferably be called oligomers (oligoZfew) to distinguish them from polymers. Often the term high polymer is also used to emphasize that the polymer under consideration is of very high molecular weight.
Because of their large molecular size, polymers possess unique chemical and physical properties. These properties begin to appear when the polymer chain is of sufficient length?i.e., when the molecular weight exceeds a threshold value?and becomes more prominent as the size of the molecule increases.

This concludes our discussion about “What is a Polymer” and you should have a fairly good idea about the various properties and constituents a plymer is supposed to possess. If you have any tips or suggestions that you think might be useful for other Plastic Injection Molding Design or Processing related engineers, then do mention them so all can benefit from them. Leave a comment below for such design or processing tips.

Molding Plastic Components

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A good knowledge of Plastic Injection Mold Design is undoubtedly the single most important factor in Molding Plastic Components. A lot of improvements have been made in the Molding processes over time, but the basics still remain the same. Mold design has been more of a technical trade than an engineering process. Traditionally, practitioners have shared standard practices and learned tricks of the trade to develop sophisticated molds that often exceed customer expectations.

However, the lack of fundamental engineering analysis during mold design frequently results in molds that may fail and require extensive rework, produce moldings of inferior quality, or are less cost effective than may have been possible. Indeed, it has been estimated that on average 49 out of 50 molds require some modifications during the mold start-up process. Many times, mold designers and end-users may not know how much money was “left on the table”.

The word“Injection Mold Engineering”in implies a methodical and analytical approach to thermoplastics mold design. The engineer who understands the causality between design decisions and mold performance has the ability to make better and more informed decisions on an application by application basis. Such decision making competence is a competitive enabler by supporting the development of custom mold designs that outperform molds developed according to standard practices. The proficient engineer also avoids the cost and time needed to delegate decision to other parties, who are not necessarily more competent.

This site is geared towards professionals working in a tightly integrated supply chain including product designers, mold designers, and injection molders. This site aims to provide working examples with rigorous analysis and detailed discussion of vital mold engineering concepts. It should be understood that this textbook purposefully  investigates the prevalent and fundamental aspects of injection mold engineering.

We will keep updating this article to include more information on both, resin and polymer parts and tool design. Meanwhile feel free to check out the Common Injection molding troubleshooting guide and other engineering plastics articles on our site.

Injection Molding Troubleshooting for common design defects

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Common Defects in Injection Molding and Plastic Injection Troubleshooting and Solutions
If you have been troubled by a lots of problems and errors during injection molding and looking for fast ways to troubleshoot them, then do not worry, you are at the right place. We will discuss about a lot of common errors that occur in injection molding cycle.




A blister is a raised area on the plastic surface, very similar to the medical condition of the same name. Many people have no clue as to what's the reason of air bubble in injection molded part.It is generally the product of too much heat on the tool or by inadequate cooling or venting. Depending on the type of tool, you can also find areas where full coverage is not working. For instance, if the injector has a flow pattern issue, it might not inject all the resin at once, allowing air bubbles to enter the molten resin. A hot runner tool might also suck air into the die because of area constriction, slowing the passage of the resin.



Good Solution to blisters:
Reduce the local spots with high temperatures by proper cooling in the mold

2.) Burn Marks on the molded part and its surface
Burn marks are generally caused by problems similar to blistering. They
manifest as literal burn marks on the plastic, black discolorations that resemble scorches. The general cause of burn marks is improper ventilation for the resin. When this happens, the burns are usually located in the position farthest away from the ventilation gate. Another cause might be that the resin is getting trapped in the injector and heating too long.
Solution to burn marks on molded parts:
1. Improve air venting to relieve trapped air and gases.
2. Reduce the material residual time in barrel.
3. Reduce the local high temperature spots in mold by proper cooling.

3.) Burrs and Flash appearing on mold's parting line
A common problem in many types of machining, burrs or flash appear on injected plastic products when extra pieces or scraps are attached to the finished piece. Burrs are usually a result of dull or inaccurately cut dies or molds. Sharpening or cleaning the dies are typically the most effective ways to remedy the situation. Mold opening during injection phase due to excessive pressure is one more resaon.
Solutions to Burrs and Flash problems:
1. Reduce the injection pressure.
2. Set clamping force to 100%.
3. Clean the parting line and check for damage or distortion on parting surface.

4.) Embedded contaminates
Then there is detritus in the finished product, it means that contaminates have somehow worked their way into the resin. A full cleaning of the machine may be necessary to find the source.

5.) Flow marks on injection molding part
Flow marks are look like discolored lines or patterns on the finished product.
When they occur, your injector might be functioning at too low a temperature. The gate might also not be properly ventilating the mold.
Remedy to Flow marks on plastic parts surface:
1. Increase and decrease injection speed to get optimized speed.
2. Increase gate size.
3. Reduce the mold temperature.
6.) Lamination or flaky layer on molding walls
This occurs when contaminates are introduced into the mold or resin but manifest as shiny flake layers in the wall of the part. These are a sign that purging compound was accidentally left in the mold.
Way to remove shiny surface or flakes from manufactured part's surface:
1. Clear the barrel and refill material.

7.) Sink marks opposite to thick walls or bosses
Sink marks are small holes or depressions, similar to tiny potholes, in the surface of the piece. There are a number of reasons they might appear. First, the material might simply be insufficient for the job. A cause that is easier to remedy is temperature variation, such as too short cooling time or too high melt and mold temperatures. The mold design can contribute to these causes, so it might be necessary to start from scratch.
How to remove sink marks from part's surface:
1. Try to increase holding pressure and injection pressure.
2. Increase material temperature.
3. Decrease mold temperature.
4. Increase injection speed.
5. If none of above works, then you need to cut plastic reduce the local section thickness.

8.) Short mold or short shot on thin sections such as ribs, incomplete filling
A “short mold” refers to a mold that is not completely filled, leading to deformation or “shortened,” parts. This occurs when the resin cannot fill the mold due to blockage, bottlenecking or injection that is either too fast or too slow.
How to remove short shot and fill part completely:
1. Make arrnagement for proper air venting in mold. Add vent pins with sufficient air vent allowance on diamter, just enough to let air pass through, but not the molten plastic. This is the most accurate and suggested solution.
2. Reduce the injection speed and increase the pressure gradually. If no change is noticed till extreme parameters are reached, then refer to 1.
The above information on injection molding defects and troubleshooting is always updating and you can check back for more details later. In case you have a problem related to defects of plastic molded parts that you want solution to, except for the points mentioned above, then send me a comment below. I will definitely help you solve it ASAP. Hope you have learned something from the above Injection Molding Troubleshooting tutorial and will visit back for more information on http://plasticinjectionmouldingdesign.blogspot.com/ .

Plastic Injection Mold Design and Process Tips

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Plastic Injection Molding (Written as “Moulding” in British Form of English) has established a significant place in the manufacturing industry, mostly as plastic has emerged as the fastest growing construction material in use today. Plastic Injection mold design is a complicated part of Injection molding process and needs to be understood well in order to gain maximum benefits from Plastic, as properly designed plastic parts are fast replacing their metallic and wooden counterparts in almost all industrial and domestic machinery components. Not only have they successfully replaced huge car parts, such as panels, bumpers and dashboards, but also fine precision components such as the camera lens assemblies, including the clear lens itself, and numerous minute watch parts.

Modern Engineering plastics such as the Liquid Crystal Polymer (LCP), Polybutylene Terephthalate (PBT),
Polyphenylene Sulfide (PPS), have replaced metallic components in automobile industry due to their excellent strength and mechanical properties, while offering evident reductions in cost and weights of machinery. With cycle times as low as 5 seconds with both thermoplastics and thermosets, injection molding has broken the barriers of costs and time limits in modern engineering. Metallic parts manufactured by conventional machining or casting processes, took around a few hours of labor and machining to obtain the finished product of similar levels.
The above discussion leaves no doubt in our mind as to why plastic injection molding is emerging as a clear process of choice over other manufacturing and machining operations. On this site, we will be discussing about very important details related to the process and design aspects of injection mold design. Plastic Injection Molding Process: Plastic in the molten form is injected or forced by pressure into a die, known as mold, and held in the mold at a high pressure until the plastic solidifies. For reducing the time required to cool the plastic, cooling channels are provided. Water is circulated through these channels at a decided temperature, which is defined by the plastic resin being used, and the molding machine’s toggle unit provides the pressure needed to carry out the operation without any opening of mold halves.

The mold is split into two halves (Core and Cavity or Fixed half or movable half), sometimes more (Sliders and Angular ejectors or lifters), depending on the shape of component to be molded. This splitting provides a means of ejection of parts from mold after complete injection cycle and also facilitates in the easy machining and replication of shape of part. The More complex a part is, the more parting lines are needed to successfully eject it without damaging the part or the mold. If it has opening or bosses perpendicular to the opening direction of cavity and core, then we need to make use of sliders or angular ejectors (also called as lifters).
A mold designer has to be conversant with a number of important aspects about mold tooling and plastic resins. He needs to be able to clearly distinguish the type of resins or plastic material to use for a specific application and function. He needs to know which materials or alloys to use for making the core and cavity of the mold and which ones to use in the manufacturing of the other mold plates and standard parts such as ejector plates, ejector pins, sprue bush, knockout rods, support pins etc. Further, he needs to have basic understanding of injection molding machines, process, injection conditions and parameters, part design related aspects such as sink marks and weld lines. It usually takes years of experience to become a complete mold designer. Due to constant developments in both, the engineering plastic resins and mold materials, he needs to keep himself updated with the latest trends and make use of them while actually designing the molds.
For more information related to Plastic Injection Molding Design and Process Tips, bookmark our site and check back periodically to get the latest information on plastic parts process and mold designing tips.

Complete Santoprene Properties and Data

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Santoprene is a thermoplastic elastomer (TPE). It is the combination of in-situ cross linking of EPDM rubber and polypropylene. It is equipped as pre-compound material which is able to course of by typical thermoplastic tools. Santoprene is a thermoplastic compound that's processed in much the same approach as any kind of plastic. The distinction is that Santoprene possesses the same ranges of flexibility and durability that are generally found with natural rubber compounds. Because of the longer lifetime of santoprene in each excessive cold and warm environments, the fabric is often most well-liked over the usage of rubber.

Santoprene? thermoplastic vulcanizates (TPVs) are high-performance elastomers that mix one of the best attributes of vulcanized rubber ? comparable to flexibility and low compression set ? with the processing ease of thermoplastics.
SantopreneR can be processed in quite a lot of ways. The abrasive resistant material could be blow molded, teleformed, or injection molded with nice ease. Along with the fact that the material is very easy and price efficient to supply, SantopreneR also will be recycled. After merchandise made with SantopreneR have seen higher days, the identical materials might be reprocessed and molded into new products. The impact of this easily recycled substance on our environment is thus not solely constructive, but might also help remove much more unwanted items ending up in landfills.
In consumer1 and industrial2 product applications, the mixture of Santoprene TPV properties and ease of processing delivers improved performance, consistent quality and lower manufacturing costs. In automotive3 applications, the lighter weight of Santoprene TPVs contributes to improved efficiency, gas financial system and reduced costs. They also offer numerous benefits in appliance4 , electrical5 , construction6 , healthcare7 and packaging8 applications.

On normal thermoplastics equipment9 , Santoprene TPVs can be injection molded, extruded, blow molded or thermoformed, and clear scrap from these operations may be reused. Santoprene TPV is recyclable in the polyolefin recycle stream.

Editor’s Note: Other posts of interests for readers reading this post:

Injection Molding Troubleshooting

What Is A Polymer

Plastic Injection Mold Design

 

Santoprene TPV advantages

Harsh-surroundings efficiency
Components constructed from Santoprene TPVs provide a constant service temperature vary from -60°C to a hundred thirty five°C (-eighty one°F to 275°F) with no cracking or tackiness. Wonderful heat getting older combines with good resistance to many acids, bases and aqueous solutions. See online Fluid Resistance Guide10 .
As one of the best examples of thermoplastic rubber in the marketplace at the moment, SantopreneR is used in quite a lot of applications. Right here is a few background on the properties of SantopreneR, as well as some of the extra common makes use of of the material in each the house and in public places.

SantopreneR is a thermoplastic compound that is processed in a lot the same means as any type of plastic. The difference is that SantopreneR possesses the same levels of flexibility and durability which are commonly discovered with natural rubber compounds. Because of the longer life of SantopreneR in both excessive cold and hot environments, the fabric is often preferred over the usage of rubber.
Portfolio of bonding grades
Choose from more than 20 grades that bond with ETPs, nylons, metals and varied polyolefins. Overmolds as thin as 0.5 mm get rid of adhesives, bonding agents and mechanical interlocks. Save costs by means of parts consolidation and design flexibility.

Tender-touch aesthetics
The dry silky feel of grips, knobs and handles made with Santoprene TPVs provides buyer attraction and cost-effective market value to client and industrial products.

Broad range of flexibility
Santoprene TPVs range from supple 35 Shore A to powerful 50 Shore D. Common function grades are suitable for most applications. FDA-compliant, NSF-listed and medical grades are additionally available. Flame-retardant grades meet UL requirements.

Simpler design for complicated parts
Design tolerances could be two to three times extra exact than with EPDM or polychloroprene rubber. This permits product designers to create elements with thick or skinny partitions and to simplify multipart designs.

Hope you enjoyed this informative post about Santopere material and will visit back our site Plastic Injection Mold Design  for more details and information soon.