Polish polymer processing companies

>> Monday, 29 December 2008

We would like to present the new series called Polish polymer processing companies. Firstly Zakłady Maszyn Chemicznych „METALCHEM” leading polymer extrusion machinery producer. Some information from the official web page below.

Almost since the beginning of its independent existence Zakłady Maszyn Chemicznych „METALCHEM” have produced machines for the chemical industry, gradually increasing the share of plastics processing machines. At present extruders, extrusion lines as well as spare parts for these machines, including chiefly the plasticizing units account for 100% of production.

Major events in the history of METALCHEM:

Zakłady Maszyn Chemicznych „METALCHEM” Sp. z o.o (Chemical Machinery Plant „METALCHEM” Ltd) is a single-plant company located in the industrial district on the outskirts of Gliwice. The company is a direct legal successor of the state enterprise having the same name.
The Minister of Chemical Industry issues an order on establishing a state company “Gliwickie Zakłady Budowy Urządzeń Chemicznych” („The Factory of Chemical Machinery Construction in Gliwice”)
The District Court in Katowice enters the company into State Companies Register (item 62)
Pursuant to the Order issued by the Minister of Chemical Industry the company’s name is changed into Zakłady Maszyn Chemicznych „METALCHEM” (Chemical Machinery Plant „METALCHEM”)
In his decision No. DR-IV/BS/15/92 the Minister of Industry and Trade delegates the function and rights of the Founding Institution to the Silesian Province Governor
ZMCh „METALCHEM” Sp. z o.o. starts its activities on the basis of a decision issued by the Minster of Treasury– Commercialization Act dated 19th May 2006. The company is registered in the National Court Register under the number KRS 0000260220.; all the shares in the company are currently owned by the Treasury.


Test Your Rheology IQ

>> Saturday, 20 September 2008

Win T-shirt, I lost (only 40%, I will try some day), have fun!

Test Your Rheology IQ


Mold balancing part 2/2

Mold balancing is design and mold manufacturing problem, machine, set up factors have lower impact. We can not skip factors result from viscosity changing, which are filling stage set up and polymer rheology. Factors which have impact on polymer flow parameters (temperature, pressure, viscosity). It is important to secure symmetry distribution in velocity, shear rate, temperature, viscosity, for mold balancing. Title and body refer to mold, injection mold, but in the same way can be analyze any tool in polymer processing (e.g. extrusion die). Interesting problem is flow balancing in extrusion blow molding and parison centering, measured by wall thickness (e.g. botlle), the problem will be described soon.

How mold balance impact parts?

Each cavity is filled and packed in different stage for imbalanced mold. One cavity can be full filled during injection (over pack) and other partly filled during holding, when we fill shrinkage losses. Effect we receive parts with different stresses distribution, shrinkage, and dimensions.

How find reasons in mold imbalance ?

Imbalance for molding cycle to cycle can be machine and viscosity difference. Factors influence imbalance for the same cycle, can be divided for:

geometrical (geometrical differences between cavities, nozzle gate dimensions and shape),
thermal (design and heating and cooling system function),
mechanical (damage, blocked cavities)

How check mold balance?

Procedure you will find in part 1/2.

When we do the mold balance test?

The best time is to do it when you validate your mold during commissioning. I establish that all your molds are balanced otherwise we can not talk about process stability and capability.

How to deal with imbalanced mold?

Identify the reason. In most cases setting up: mold, hot runner or nozzle temperature is sufficient. If not follow the rule always chose mold adjustment not molding parameters. Mold adjustment you will always do once, parameters you have to always monitor, any deviation and you will receive bad part.


Bimodal high density polyethylene, HDPE

>> Wednesday, 17 September 2008

We will try to imagine how bimodal molecular weight distribution rise. We will focus on two main properties: processing and mechanical. We start from normal (unimodal) molecular weight distribution (please, start to analyze the graph). Macromolecules with short chains, are easiest to process, polymer has lower viscosity, long chains are responsible for mechanical properties the grow. Considering, what left (middle), can be replaced. The idea was simple, eliminating average properties, we receive polymer with key properties.

Return to the most important, processing and final product properties, considering molecular weight distribution. Short fractions or single monomers are gaseous substance, waxes, their impact is questionable (easy degradation, responsible for bad odor) and appear for unimodal distribution, changing the distribution we eliminate them. Long fractions generally affect mechanical properties, e.g. stiffness, it is possible to reduce wall thickness (shorter cooling time, than cycle time, higher output) with the same results in drop and top load tests, etc. increase ESCR. Bimodal, HDPE is specially recommended for aggressive substances, e.g. in household segment. It has low die swell, Barus effect close to 1, designing the forming instrumentation we know the key parameter, on the other hand changing from unimodal to bimodal grade will probably cause investment in new instrumentation (from large cross-section to smaller, not possible!).

Summary, main properties for bimodal HDPE:
• higher stiffness (higher density),
•higher chemical resistance, ESCR (Environmental Stress Cracking Resistance),
• higher impact,
• low die swell (Barus effect),
• low degradation,
• no bad odor.

Bimodal HDPE has the same product application as unimodal grade, e.g. films, bottles, tubes, caps, etc. and it is a great example in developing on polymer segment.


Polymer viscoelasticity part 2/2

>> Tuesday, 16 September 2008

Once more, technical issue, from Massachusetts Institute of Technology web page click right on Rheological Behavior of Fluids than save target as on your drive, and run using Realplayer

Conclusion and complement for part 1/2, polymer viscoelasticity effects: Weissenberg and Barus.

Weissenberg effect during shear flow between two coaxial cylinders appear climbing up along the rotating rod for no-newtonian fluids, that is melted polymers. The same effect can be observe during stain an paint mixing and can not be observe for newtonian fluids, e.g. water.Weissenberg effect is a result in generating during shear flow extra stain, called normal stresses. Barus effect appears during extrusion and it is observed by swelling extruded material leaving nozzle. For melted polymers the effect is big and describe as relation between flow and nozzle diameter, it is beetwen 1,2-2,5. Depends on flow capacity, tool geometry, but the most on relation channel length/diameter and polymer properties, less observed for bimodal polyethylene about it in the next act. The same as Weissenberg effect, Barus effect it is due to a non-zero first normal stress difference.


Molecular weight in polymer processing

>> Monday, 15 September 2008

A polymer is a set of molecules with very high molecular weight called macromolecules. Macromolecules are composed of basic units called monomers. Monomers are groups of the same linked atoms. Molecular weight is a sum of atoms weight for molecule.
Molecular weight impacts everything, viscosity, strength, thermal resistance, light transmition, but not density. Macromolecules are different, different in length, start from monomers and end up with “huge” macromolecules. This is the statistical (e.g. normal distribution) process of production, every lot (even bag!) from the same plant, from the same method, can be different in molecular weight distribution and average molecular weight.

Different fractions have different impact on processing and application properties. Short fractions, or single monomers are gaseous substances, waxes and the advantages are problematic (easy degradation, there are responsible for bad odor) With molecular weight grow, viscosity will grow, mechanical properties will grow, etc. chains will be longer.
Average molecular weight and the range have to be consider during choosing the grade for processing methods, e.g. extrusion blow molding one of the most important is melt strength which protect against sagging. It will be possible for grades with grater viscosity, high molecular weight, etc. for low shear rate.
Technique still benefits natural polymers, e.g. caoutchouc from elastomers, from polymers cellulose and proteins and it derivative.

PS. Picture shows: molecular chain of polyethylene and comes from: University of Florida, USA


Mold balancing part 1/2

>> Sunday, 14 September 2008

Does your mold balanced? There will be the part of just preparing problem for mold balancing. Fundaments with mechanism in part 2/2 which formally is the first part.

How to check mold balance?
The eases way is to weigh parts from mold. I suggest go to the shop floor take the full shot and weigh on the most precise available weight. Date you can compile in the form presents below. The best you can do is to take more than one shot and count the average from the same cavity. You have two ways, try both, count deviation from maximum weight (first way) and from average weight (second way) for all cavities. Formulas are in the table, where indexes; m – maximum weight from all cavities, n – weight for the variable cavity, a – average weight for all cavities.

Few conclusions from the above example. Cavities 7 and 10 are extreme first is the most second the least filled. Deviation from average gives the tendency +/- from average. Cavities 9 and 10 are the worst balanced. I would assume 5% as boundary between cavities and allow mold to be acceptance during commissioning.
The same you can do for not full filled mold, assume, 50% filled, there will be more visual rating.
When you analyze your case include the cavity, hot runner and cooling system location.


High impact polystyrene, HIPS

>> Saturday, 13 September 2008

Short and in the theme about mass thermoplastic polymer as high impact polystyrene, HIPS is. As I know there is not always known but all the power is in the name. Let’s try to decode. Impact is the resistance for cracking. This properties HIPS owes polybutadiene rubber. And that’s all. When you compare light transmission, HIPS is translucent and general purpose polystyrene, GPPS transparent.


Polymer viscoelasticity part 1/2

There will be screenshots from Rheological Behavior of Fluids movie applied, it is available from Massachusetts Institute of Technology web page, Realplayer is an requirement.
The movie is s great introduction for no-newtonian fluids (as polymers are) properties. There are many experiments which will be key for polymer processing understanding where this properties emerge. The movie history reaches latest 60th (fundaments for fluid mechanics and rheology are the same) it is not short more than 22 minutes but it is worth seeing more than once. As you listen carefully you will find answers for problems from: newtonian fluids, no-newtonian fluids (Bingham, pseudoplastic, dilatant fluids), viscoelasticity effects, Weissenberg effect, Barus effect, time dependent effects
Viscoelasticity is the property of materials that exhibit both viscous and elastic characteristics when undergoing deformation. Viscous materials, resist shear flow and stain linearly with time when a stress is applied. Elastic materials strain instantaneously when stretched and just as quickly return to their original state once the stress is removed. Viscosity we know already. Elasticity is material return ability to their original state once the stress is removed.

Polymers have both solid and fluid properties and are time dependent (because of its molecular structure). Viscoelasticity gauge in polymer processing is relation between characteristic material time and characteristic process time defined as Deborah number.

Back to the movie, the first example shows how time scale is important, ball (viscoelastic material, why, find below) for very short time, process time behaves as elastic solid (Deborah number tends to infinity).

For long time, process time ball behaves as viscous fluid ( Deborah number tends to zero).

In part 2/2 there will be about viscoelasticity effects, that is Weissenberg effect and Barus effect.

Once more, technical issue, from Massachusetts Institute of Technology web page click right on Rheological Behavior of Fluids than save target as on your drive, and run using Realplayer


Autodesk® acquired Moldflow®

>> Tuesday, 29 July 2008

25th July 2008 Autodesk® acquired Moldflow®, about plans I informed recently. The transaction is worth a total of USD 297 million.

I wrote then…

Moldflow® today is not only injection simulation software, CAE (Computer Aided Engineering) based on FEM (Finite Element Method) but offers process optimization, management and production control. This acquisition evidence of development in mold and plastic injection production and shows how plastics impact our life. Autodesk® sees it. CAD/CAM/CAE integration will not stop only on this tree systems in the way of full computer integration.


Intrinsic viscosity, I.V

>> Sunday, 27 July 2008

Terms, allegiances, connecting molecular weight (or range) and viscosity will be explained for polyethylene terephthalate, PET and how it influences applications and processing.
Intrinsic viscosity, I.V we measure by measuring viscosity of solvent and polymer solution solved in it.
How to interpreted I.V? Molecular weight grow means longer polymer chains consistence intrinsic viscosity, I.V grow, forward, e.g. stiffness grow. I.V determinates PET resin application, for I.V:

• 0,40-0,60 dl/g fiber
• 0,76-0,84 dl/g bottles
• 0,85-1,05 dl/g extrusion

As we know the relations we can chose the adequate resin for the application. When we produce bottles in, injection stretch blow molding, ISBM for e.g. water we will chose higher I.V (0.82 – 0.84 dl/g), bottle stiffness will be the most important. For cosmetic packaging, when shapes are more complicated we will chose lower I.V (0.76 – 0.80 dl/g) for better flow properties, which will give better detail mapping.


100% biodegradable and 100% compostable bag

>> Saturday, 28 June 2008

The first polish 100% biodegradable and 100% compostable bag from corn comes from BIOERG which is DIN EN 12432:2000 certificated.

Photo http://www.plastech.pl

DIN EN 12432:2000
Requirements for packaging recoverable through composting and biodegradation - Test scheme and evaluation criteria for the final acceptance of packaging


Optimization in polymer processing

>> Monday, 16 June 2008

An introduction to optimization in polymer processing based on extrusion. Described methods are universal and can be applied in other polymer processes. We start from definition than optimization methods, how we acquire input and output date and for the end input and output data in extrusion.

Every task to do we can present as an answer. Optimization would be looking for the best (extremum) in the possible answers with assumed criteria, defined target function (e.g. max. output, min. power consumption).

For small area statistical methods like regression analysis when full area is scanned is applied. For large area artificial intelligence methods have to be applied, e.g. neural networks, genetic algorithms and hybrid methods (connect more than one). Extrusion optimization is complex. There are many optimization criteria, they can be conflicting like max. output and min. power consumption and many input data (geometrical, process parameters).

We have two ways of collecting the output data for optimization. Experiments and simulations. First can not be applied in some situation like changes in screw design. Second does not have this limitation and it can be effective tool for acquiring the data.

The characteristic process for optimization is the constant development which you can see on the picture. Output data from experiment or simulation as optimized can be applied as input data for other research.

This is the introduction. In the near future DOE (design of experiments) will be described as a one of the optimization technique.
From one site we have simulations and experiments one and other cost, experiments we know why, and simulations (e.g. REX, Moldflow, Cadmould 3D-F, etc.) software availability, not cheap. On the other hand, optimization the same software availability (e.g. Statistica). The best would be both simulation and optimization integration. What is more know how. Does it limit anything? Investment which will return. This is the way of doing business. Would you like to know more please let me know in mail or in comment. I will try to add what is needed.


The world’s first polymer banknote

>> Tuesday, 3 June 2008

After plastic cards it is time to polymer banknote.

For hundreds of years, banknotes have been made from rag-based paper. Today, banknote issuers are faced with the challenge of increasingly sophisticated counterfeiting techniques and there are serious doubts that paper remains a viable material for secure banknotes.
CSIRO’s expertise in polymer and synthetic chemistry was used to develop a non-fibrous and non-porous plastic film, which the banknotes are printed on. This substrate gives high tear initiation resistance, good fold characteristics and a longer lifetime than paper.
The substrate and the specially-developed protective overcoat prevent the absorption of moisture, sweat and grime so that the polymer banknotes stay cleaner.
CSIRO has also developed a variety of overt and covert security features for use on polymer banknotes. These security features are produced from a combination of spectroscopic techniques, synthetic chemistry, nanotechnology, surface science microstructure manipulation and polymer chemistry.


Awards and prizes Plastpol 2008

The list of prize exhibitors at Plastpol 2008.

Distinctions of Kielce Trade Fairs

MAR-PACK Wytwórnia Opakowań z Folii, Maszyny - Chwaszczyno
FOMPOL Sp. z o.o. - Katowice
KONEK PSN - Bydgoszcz
Zakłady Azotowe w Tarnowie Mościcach
BIOERG Sp. z o.o. - Dąbrowa Górnicza
BIBUS MENOS Sp. z o.o. - Gdynia
PLASTECH Paweł Wiśniewski - Toruń
SMARTTECH Sp. z o.o. - Łomianki
WADIM PLAST - Michałowice

Medals of Kielce Trade Fairs:

ENGEL POLSKA Sp. z o.o. - Warszawa
FRIUL FILIERE S.p.A. - Buia, Italy
DOPAK Sp. z o.o. – PROSES

Distinctions of Kielce Trade Fairs for stand arrangement

DOPAK Sp. z o.o. - Wrocław
BRENNTAG POLSKA Sp. z o.o. - Kędzierzyn-Koźle
BASELL ORLEN POLYOLEFINS Sprzedaż Sp. z o.o. - Płock
ALBIS POLSKA Sp. z o.o. - Poznań
GRAFE POLSKA Sp. z o.o. - Lubliniec
TISZAI VEGYI KOMBINAT RT - Hungary and SLOVNAFT A.S. - Slovak Republic
GABRIEL-CHEMIE BOHEMIA s.r.o.- Czech Republik and GABRIEL-CHEMIE POLSKA Sp. z o.o. - Pruszków
Polimeri Europa Polska Sp. z o.o. - Warszawa and DUNASTYR Polystyrene Manufacturing C.Co.Ltd - Budapest/Hungary

Medals of Kielce Trade Fairs for stand arrangement:

ARBURG POLSKA Sp. z o.o. - Opacz


Animal waste gets chance to become biodegradable plastic

>> Monday, 2 June 2008

For full story please visit University of Waikato web site. There will be no comment this time.

The new process, developed over two years by University of Waikato chemical engineer Dr Johan Verbeek and Masters student Lisa van den Berg, can turn animal protein waste like blood meal and feathers into a biodegradable plastic using industry-standard plastic extrusion and injection moulding machinery.

A process developed at the University of Waikato will allow animal waste to be turned into useful and biodegradable plastic.

"Proteins are polymers so we know they can be turned into plastics," Dr Verbeek said. "Plant proteins successfully been used to make bioplastics, but animal protein has always ended up gumming up the extruder. The process we've developed gets round that problem. People said it couldn't be done, but we did it!"

It's a source of plastic that doesn't rely on petroleum, so we also see it potentially being blended with conventional plastics to reduce the total petroleum load.

Plastic Fantastic - University of Waikato scientist Dr Johan Verbeek says the bioplastic created from animal protein waste can be used for plastic sheeting.


Plastpol 2008

>> Sunday, 1 June 2008

Just few words about 12th International Fair of Plastics Processing Plastpol which took place in Kielce, Poland 27-30 May, 2008. Sorry but there will be no sum up and statistics and even my own consideration the next time I will be prepared better. There are only two pictures of extrusion machines. The picture below presents machines from polish plastics machine manufacturer ZMCh Metalchem Gliwice one of it with high torque synchronous motor.
PS. Have you visited Plastpol? Please share your impressions.


Win Receive 2 tickets for 12th PLASTPOL, Kielce, Poland

>> Monday, 26 May 2008

There were no good answers, more there were no answers at all. The exhibitions starts tomorrow and if you would like to receive two tickets for…:

The largest exhibition in Central Europe

12th International Fair of Plastics Processing


27-30 May, 2008
Kielce, Poland

…just pass over the password: polymer processing at the checking desk and you should get it.

See you there!

Best regards,

Piotr S.


Books recommendation.

>> Saturday, 24 May 2008

There is a books recommendation widget on right as you have probably noticed. I would like to present full package and books are on of the puzzle in it. I only recommend publications which I know, read and come back. I have chosen from one of the affiliate programs and wanted to be the global one. It helps to present the book. The choice always belongs to you.
There is the last recommendation. When you search for books choose authors which are known experts because they represent quality. E.g. Johannaber Fredrich, Klemens Kohlgruber, Michaeli Walter, Osswald Tim A., Potente Helmut, Rao Natti S., Rauwendall Chris, Tadmor Zehev, White James L., Wilczyński Krzysztof and some more most of them are height professors and industrial experts in polymer processing.


PET (polyethylene terephthalate) processing.

>> Friday, 23 May 2008

This is huge subject. Many resins, many processes. I will focus on selected problems which can be interesting for packaging and one stage method, ISBM (injection stretch blow molding). In this way we had defined the resin, it will be bottle grade with intrinsic viscosity I.V. in range 0,76-0,84 dl/g .In the early 1940s PET was used for the first time in synthetic fiber application this is still on of its major uses. Bring over by checking yours cloths tag (polyester).
The most important is to understand polymer morphology. PET the one which comes in the bag has crystalline structure (temp. softening and melting point 250 dC) during injection step and rapid cooling then stretching and blowing we receive amorphous structure. The reason for it is that when we cool polymer chain can not position themselves to establish crystalline structure. When we consider the bottle which has the amorphous structure filled with hot water it will be softening from 60 dC (carefully with experiment because scalding).

Each step of the ISBM process has reflection in the product properties. Transparency because of amorphous structure that is rapid cooling. Good barrier properties come by biaxial orientation during stretching and blowing.


Masterbatch and polymer processing.

>> Thursday, 22 May 2008

I would like to analyze dyeing and it influence on polymer processing and the final product properties. The key point will be the crystallization. Thermoplastics we can divide into that with amorphous (irregular) and semi crystalline structure (regular) it means crystalline in some area and amorphous in other. Crystallization fallows through the nucleation process when crystals rise and grow.

Nucleation impacts on polymer processing and product properties by increasing:
• crystallization temperature (reduces cooling time in injection and extrusion molding up to 20%!),
• transparency,
• mechanical properties.

the reason for it is that we have more crystallization centers and fine grained structure opposite to large sferolits.

Everything would be ok if we had this knowledge otherwise it can happen that when we dye polymers e.g. with phthalocyanine pigments (blue and green colors) we will receive “natural” nucleation. There is one feature not always desired the shrinkage which comes with the regular structure of polymer. The general rules the darker color the higher nucleation with all adventures and disadvantages. The problem will come out when you produce the same item with different colors. Every time it is needed to correct the machine settings and it means: scrap, downtime, etc. We can find polymers (the described problem we can match e.g. with polypropylene the semi crystalline polymer) where nucleating agents eliminate the effect of nucleation from masterbatch.

Best Regards,

Piotr S.


Polymer Extrusion by Chris Rauwendaal.

>> Wednesday, 21 May 2008

This is a book which I do not have to recommend for people who are involved in the extrusion process. For those who are not just briefly one sentence. This book demonstrates how extrusion theory can be applied to actual extrusion problems such as screw design, die design, and troubleshooting. The recommendation can be the author achievements in the extrusion field in numbers of equations and patents.


Autodesk® acquires Moldflow®

>> Monday, 19 May 2008

One of the topics which will come back are simulations and engineering in the polymer processing this is the reason I could not pinch the comment that Autodesk® announces intent to acquires Moldflow® As I have noticed Autodesk® is active on this field lately. Moldflow® today is not only injection simulation software, CAE (Computer Aided Engineering) based on FEM (Finite Element Method) but offers process optimization, management and production control. This acquisition evidence of development in mold and plastic injection production and shows how plastics impact our life. Autodesk® sees it. CAD/CAM/CAE integration will not stop only on this tree systems in the way of full computer integration.


Polymers genealogical tree.

I like this picture. What do you think?


“Innovation in polymer processing”

>> Wednesday, 14 May 2008

It will be an information from Poland about past event the conference “Innovation in polymer processing” - science and industry partnership. For more information use http://www.polimer2008.pl/ sorry only polish. The reason I am writing about it is the Prof. James L. White person. One of the important person in the world’s polymer processing made a speech “Polymer Processing: Past, Present, Future” The subject says everything, we were experienced with the past of our industry and the evolution in process modeling (single / twin screw extrusion, and injection molding). It was not the only lecture this day. I would just mention that there were from both science and industry sites. Congratulation for students an interesting idea and perfect realization.

Photographer Kinga Kurowska, comes from http://www.tworzywa.pl/

Dr. James L. White
The University of Akron

Professor of Polymer Engineering,
Founding Director of the Institute of Polymer Engineering,
Harold A. Morton Professor of Polymer Engineering

I would only recommend from Prof. James L. White an author of rheological equation known as White-Metzner fundamental publications from polymer processing as:


Cyclo Olefin Polymer

>> Thursday, 8 May 2008

I would like to interest you in thermoplastic engineering Cyclo Olefin Polymer. The reason I thought that you can find some application for it. For me what I see from the first study it is transparent, resistance for: acids, alcohols and fragrances and possibility to convert in various processing methods For more information please visit:



Polymer processing recommendation

>> Tuesday, 6 May 2008

I start with a new page element the new consideration called recommendation.
The first is a magazine about polymer and rubber called: British Plastics & Rubber.


Why? We can find information from polymer world on the web site, this is standard. What next? We find archive articles from the previous magazines, with download option, free of charge. Free of charge is the on-line version for current publication the print one is not. Advantage: clear categories, you will find what you need at the specific topic.


The glass polymer® processing

>> Monday, 5 May 2008

Not just about Eastman Chemical Company products but the trade name is perfect for properties of copolyesters. There is one more which I know SK Chemicals (in Poland known from PET installation) and maybe someone else but sorry if I skip it. Some information from chemistry. Amorphous transparent copolyester is produced by the reaction of terephthalic acid (TPA) with ethylene glycol (EG) which a certain amount of EG is replaced with cycloheksane dimethanol (CHDM). The most important factor is the proportion between EG and CHDM. When we increase the CHDM level we prevent crystallization, increase chemical resistant, transparency, and improve processability (lower melt temp., less restricted drying).
For the reason I am involved in polymer field I promote even I do not know about it polymers. The key point is to replace glass, on the other hand to replace polymers such as: PMMA, SAN, etc. in the packaging segment. These materials have some adventures comparing to copolyesters, primo there are cheaper per kg but it is not always the way we should go and it can draw to wrong conclusions.
There are not so many PETG commercial applications but I think there are notable. For those who are more interested please use net sources. When we compare to PMMA it is margin. When you take products from this two materials you will feel the difference not only in your pocket. PETG is heavy has higher density, maybe it will be subjective but it is more like glass this is what you can see, the effect. There will be better impact, chemical resistant, stress cracking, you can eliminate PP insert.
I have been focused just on packaging application and more on cosmetic and injection molded parts. On the other hand believe me even packaging can be technological challenge when we consider parts with wall thickness higher than 10 mm. There is a space for the most important what I wanted add, my own experience. This two suppliers offer grades known as extrusion blow molding and I suggest to take a shot and inject it. What we receive, lower material costs (this grades are much cheaper!) if we can not convince the customer in the other way. It is worth trying.


...and how it could have been started

>> Saturday, 3 May 2008

It will less serious than the last time. Would you decided what to do in life after seeing a movie? I think some of you have done it even me I wanted to become a sport’s agent, but it was before seeing “Jerry Maguire” directed by Cameron Crowe. Please enjoy episode from “The Graduate” (1967) about…


“...just one word...plastics...it is a great future in plastics..." and all true.

What was yours first contact with plastics and what makes that you think about them? Maybe you remember the beginning?


How have it been started...

>> Sunday, 27 April 2008

I found polymer processing as something: new/fresh (it was for me, and it is comparing to tooling methods), exciting (later about it), growing (new: processes, tools, machines, materials, etc.) and mystery (viscoelasticity). It was about 10 years ago in Poland at Warsaw University of Technology.

What I like in polymers the most? We know about the non-Newtonian characteristic of melted polymers. For that who are not familiar with basic terms for polymer processing I will prepare some more detailed information in the near future.

Briefly it is non-linear characteristic between shear stress, and shear rate, known as a flow curve. For Newton fluids (ex. water, petrol, melted metals, etc.) the curve is straight and dynamic viscosity, (the most important term in polymer processing!!!) is constant. For melted polymers (pseudoplastics fluids, viscosity falls with increasing shear rate) we can mark out tree characteristics stages for viscosity, linear for small shear rates, 1/10-10 [1/s], non-linear and linear for high shear rates 10^5-10^6 [1/s] when the shear viscosity is constant.

This is it I like the most. The non-linear behavior of polymers. When you increase the speed (ex. screw speed) you will observe that for some values your output (ex. power consumption) will be not increasing (or will not increase as much) will be constant, but you will have higher output. Sometimes it can be more complicated and depends on more factors!!! Characteristic is that in polymer processing everything depends on everything. You can apply it in the real process. It will be explained for injection molding. When you increase injection speed (proportional to sear rate) you should find the point when viscosity will be constant. It gives you quality, any changes in material or machine will not influence so much the product (ex. shrinkage). If you can try to use higher injection speed (if possible). How to do that the scientific approach will tell you and I will do it in the future.

I wanted to describe it simple but now I do not know if it was done simple. What do you think?



>> Saturday, 26 April 2008

I would like to welcome everyone who is visiting the polymer processing’s blog. First of all I apologize for any language mistakes. I hope that I will be not prevent from supporting in helpful information and will not discourage you from visiting it. I am going to do one’s best. Why I decided to do it? I have started from http://www.tworzywa.blogspot.com/ this is about polymer processing. I understand you could not notice it because it is in polish. Most of my knowledge based on global sources and it is sometimes different from that I find in Poland. It is more complex. In this way of thinking about polymer processing I am away from that I see around and it sometimes helps but for this blog will be not competent. There are many others reasons but about them in the future. Both blogs will be living separate life because have different views. I hope meet from time to time. Both will be a record from my experience in the polymer processing field. Tools which I have explored, my point of view, when I focus on the original information with explanation. There is the staff you can find in the close future. You are welcome on both sites. Enjoy it.





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