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Brentwood Plastics blog

PE Film Lead Time Factors

Posted by Joel Longstreth on Thu, Dec 08, 2016 @ 05:52 PM

The ship date for custom PE film involves much more than a first-come-first-serve queue.  An extruder who runs their
backlog in this fashion or has a salesman running the backlog is not long for this world.  

The primary consideration in setting up a backlog is minimizing scrap.  Clearly at loggerheads with customer's
urgency.  Keeping peace with all parties is an art.  The scheduler's agenda is to consolidate a sequence of films made out
of the same PE resin as long as possibleto avoid transition scrap.  With resin cost at about 75 cents per pound, every pound
of scrap is really about $ 1.00 lost factoring in labor, electricity and overhead.

A medium scale extruder puts out about 500 pounds an hour.  What would you do ?

It's best practices to have some leeway in ship dates.  We promise our orders for "week of _____ ".  A smart play is to promise
a Thursday ship date.  4 out of 5 chance it will ship early or on the date.  1 in 5 chance it will be a day late and so what ?  only a
day late.

It's also best practices to have a few dummy orders in the backlog to both act as a cushion for breakdowns and allow for opportunities.
If an order comes in with a ship date 3 to 4 weeks out for a resin running today, it makes common sense to tail it in to
avoid setup scrap instead of running it as a stand-alone 3 weeks from now. 

Distant secondary considerations are width and thickness changes ( there's the central theme of avoiding scrap again ) followed by pigmentation.  
Cleaning out after colors is time consuming and messy.  The line must be shut down, purged, what is called the screen pack / breaker plate must be changed.
The ordeal is followed by an expensive, frustrating waiting game while the remnants of the color clear out. 

Back in the day, we had a shrewd customer who went out of his way to pay his bills every Saturday.  A check for all invoices in the week would show up like clockwork on Monday morning.  Why ?  To tempt the film extruder to deviate from fundamental priorities.

Of course, there are justifiable exceptions but they are few.  Re-work of returned or defective product or doing an occasional favor for a good customer who is out of film and shut down.  

So now you know why:

Coextruded films have such extended lead times

shrink films have such a wide variation in MD / TD shrink ratios
( the order goes on the machine that needs work )

pigmented films have longer lead times

Are you wondering where is our proof that first-in-first-out doesn't work ?  That's easy.  The outfit we sold out to in 1984 ran orders in the sequence received.
It took them about 3 years to declare bankruptcy.


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Topics: LDPE film, poly film, polyethylene film

PE Film Industry Consolidation ?

Posted by Joel Longstreth on Thu, Sep 15, 2016 @ 12:35 PM

Like any industry which matures, there is first a dynamic growth curve followed by the inevitable consolidation wave.  The blown PE film business is both consolidating and contracting.

By the 1920's, there was a proliferation of automobile manufacturers in the thousands.  Aerospace didn't have
thousands of airplane manufacturers, but maybe hundreds.  An early map of the Kimberley mine was complex
with stakes by numerous colorful characters.  Where are they now ?  

Back in the 1950's, the commercial viability of blown PE film was uncertain.  Before our founder Joe Longstreth
established Brentwood Plastics in 1961, he sold PE resin by setting up companies from scratch to make LDPE film and take away market share from old fashioned true cellophane.  

Cut to present day.  The number of PE film outfits worldwide is certainly in the thousands.  "Turn-Key" film lines are ubiquitous.  Back in the early days, we bought the components separately and made some of the parts ourselves.  My grandfather designed a surface winder for narrow width tubing from scratch which is still in service.

In the US, the consolidation phase has been going on for decades at every strata.  The largest instituional trash can liner manufacturer is actually an amalgamation of formerly regional players.  You can't argue with the success of Sigma group's strategy of expansion by acquisition of financially distressed extruders.  By contrast, the largest manufacturer of private-label trash bags is Poly-America who has grown dramatically mostly by organic growth. 

Berry Plastics' mega merger with AEP is the latest chapter in consolidation of companies with roots going back to the 1970's.  Armin Kaufman, founder of Armin Films sold out to Tyco who unloaded their film maker portfolio to Berry in 2005. Berry merged with another large bankrupt player who had gone bankrupt in 2009 - Pliant.  

Where is Armin Kaufman now ?  In Hillside, NJ where he founded Hillside Plastics with the proceeds from the Tyco sale in direct competition.

To take stock, we compiled a list of US operations which include polyethylene blown film extrusion with apologies to anyone we overlooked ( call us if you want to be included ).  There was no clear trend.  A lot of old names were gone either due to buyouts or going out of business ( this is a capital-intensive business; the tripling of resin cost since the mid 90's has weeded out players with inadequate working capital ).  Many have vertically integrated blown film in their operations.  Some niche players were unchanged, some have developed into giants. Next Generation films is an extreme example.

We have been there / done that selling out thing back in 1984, probably not going back there for a while.  We believe there is enough demand for an old school, handcrafted monolayer operation.

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Topics: pe film

Developing Custom Plastic Films

Posted by Joel Longstreth on Tue, Sep 06, 2016 @ 03:35 PM

Product development is a rough, bumpy ride with no certain outcome.


It's always a bracketing process which requires many iterations no matter how methodical the approach.
Sir James Dyson thrives on failure.  His vacuum cleaner has been through 5,126 versions.  Well tested products often result in recalls.  


What replaces a bad idea ?  A better one, of course.  De Havillands' culture was that if something
didn't look right, it probably wasn't right.  The reason airplane windows are rounded is that the Comet broke up in flight because the square windows cracked in the corners.


Thomas Edison famously went through 940 filament candidates before he hit on tungsten.  In retrospect
he was more alchemistic than methodical.   Failures did not discourage him.  Instead, he viewed 
failures as data about what did not work.


Today's short attention span is not conducive to perseverance.  By the third iteration, many prospective customers figure we are guessing and dismiss us as incompetent after we are unsuccessful at solving a problem nobody else has been able to solve.  Group think kicks in when the big boss gets the super compressed zip file executive thumbnail version.  Plastic film is a lot simpler than molding, so we rarely need more than three attempts and there are no molds.  

Unlike automotive, our customer's plant is the proving ground and beta test site.


We can't run tests at our facility before presenting a version. With each failed iteration, our credibility erodes.

Suppliers who initially appear discouraging or negative are often the best to work with in the long haul.  These seasoned veterans already know what will work and what won't.  Contrast this approach with a company whose positive-minded sales rep makes promises the company can't deliver.  Like so many things in life, it's not complicated entering relationships; it's extricating oneself which is difficult.  In injection molding, molds are the ties that bind.  Sadly, the empty promises often lead to ugly lawsuits.

It's intuitive that the more complex the problem, more perseverance and revisions are required.   After nearly sixty years, you might think launches would be old hat for rocket scientists.  Everybody except NASA has not given up.  Elon Musk said the last disaster was Space-X's most complex undertaking.


" Design creep" is a plot twist which always sends the process into overtime.  Design creep is introduced in two ways.  Most often, it's after the first or second iteration despite our efforts to capture all the performance parameters up front ( see contact us tab ).  

                                             "Oh, we forgot to tell you we need the film to ______________ ".
For example, we just found out that a film needs to unroll easily after being stored in a desert warehouse all summer.  After the third iteration.  Had this requirement been disclosed in the beginning, we could have saved a lot of time, money and plastic.  Design creep is also introduced when marketing gets into the act and imposes new features often without thinking through the ramifications.  The scary bit is this is America; one must always be thinking of how one could get sued despite best intentions.

It's important to know if the project is ready for prime time.  In the words of one of my former bosses, " you need to be realistic about whether you are in the development stage or in the commercial phase."  Disasters often occur with wishful thinking when on the cusp of going from development to commercial.  And in the words of another of my former bosses, " there's only one thing worse than not having a product - it's having a product that's not fully baked." 

Much has been written about inventions, the tenuous path to commercialization and accidental discoveries. What we do is relatively simple.  If you want us to solve a problem for you, just tell us what you want.  The long form on the contact us page is not best practice for capturing leads.  In lieu of finding out the performance parameters over the course of literally months, we are trying to capture all the performance parameters up front.


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Topics: custom PE film, custom LDPE film

PE Film Make / Buy Decision

Posted by Joel Longstreth on Mon, Aug 08, 2016 @ 03:51 PM

It's cliche but true - when milk is cheap, why buy a cow ?  Peter Drucker said it is better to integrate upstream than downstream.  The case for vertical integration play involves payback analysis and other factors.  Henry Ford made his own power mainly because he was fed up with dirty intermittent power.  I can relate.

The often overlooked lynchpin of a successful captive film operation is making it a stand-alone P & L.  


Many companies opt to buy film even though they consume enough film to feed a grass roots film plant.
Procter and Gamble Clopay have had a symbiotic relationship for generations.  When P & G puts up a diaper operation, a Clopay embossed film plant will pop up in close proximity.  It's only one item.  

Custom flexible packaging has more moving parts.  There are good reasons to buy PE film on the outside:
1.  Lead time     Using multiple extruders increases the likelyhood of finding a line which needs work.  The New York tri-state area is the best example in the US.

2.  Painless rejection   Rejecting film which comes from an outside source does not generate the acrimony resulting from an internal rejection.  Gotta keep the prima donna pressmen happy, right ?  Finding another film source is easy.  Finding a reliable pressman is not.  If you don't reject film outright, specious claims are a time-tested means to shaving a few cents off raw matierial costs.  The extruder would rather take a discount than see the film show up on his dock.

3.  Cash flow and turns   Most bag makers do not understand the concept of borrowing to pay invoices timely.   Line of credit ?   What's that ?   It's simpler to buy from multiple sources and string out your accounts payable.  If you do hit your credit limit, buy from a different extruder.  

Buying resin is more complex.  
You have to:
forecast 90 days rolling
wait sometimes five weeks for the railcar to show up
pay bills timely
provide quarterly financial statements to the resin companies

If you're on the wrong side of the market, every penny you're off =  $ 2,000.   Film prices drop shortly after CDI comes out.  Whatever is in the silos gets devalued.  Why bother ?   It's much less risky to order film for each job.

4.  Lowest cost   Overcapacity in blown film is a time-honored tradition.  Don't just keep your supplier honest.  Constant reverse auctions give new definition to keeping a supplier honest.

One of our successful alumni - Dave Frecka, founder of Next Generation Films - is betting big on yet another expansion literally the size of two homesteads.  He's betting that his customers will not make their own film.

Flexible packaging converters see making film as much simpler than their complicated processes which involve inks, plates, solvent recovery, adhesives, people, bag and pouch making.  They visit a blown film plant, see an operator sitting down reading a book or taking a smoke break.  The operator is sitting down because he's exhausted from all hell breaking loose over the last two hours.

In theory making blown film is a simple, continuous process.  If it was really difficult and complex, there would not be over 27,000 known blown film shops on the planet. The truth is making blown film is an art despite what equipment manufacturers proffer as "turn-key" lines.  There is a learning curve. 

Let's look at how seemed to be a good idea at the time that led to a salvage play.

The same schedulers who won't schedule a print job until the plates and film are both present hate to wait for film.  The reason the printer has to wait is that a properly run film backlog prioritizes minimal scrap. When the backlog is set up on a first-in-first-out basis or disrupted by the printing plant manager who succumbs to an ultimatum from the cutomer who has threatened to cancel ( sticking the converter with the cost of the film and plates ), excessive transition scrap is the result.   Scrap factors which are not captured in the in the justification for going vertical are transition scrap, internally rejected film, startup and shutdown scrap.  The boffins pick up on the higher than projected cost of goods sold first.  Until the day of accounting reckoning arrives, it's a myopic free-for-all.  Everybody feels good about percieved free film, controlling their destiny and not getting ripped off by their film supplier.

Of course, there are many successful vertically integrated operations.  If the end product has ample gross margin, allocation of the cost burden is moot.  I'm not making this up - many lucrative operations have an internal transfer cost of a penny over resin.   

A blown film operation is capital intensive with inherent high operating leverage.  It makes or loses money incrementally on either side of break-even.  When volume falls short of the break-even, the "prisoner's dilemma" follows.  Running at a loss is better than shutting the line down.  The penultimate desperate phase is scrambling for cheap work to maintain cash flow.  Over the years, I have been to many industrial funerals known as auctions.    We get notifications of liquidations every 6 weeks or so.  We hear from leasing companies who ask if we are interested in lines they have "carved out" of a converting operation.  When the line was first up and running, there was a party atmosphere - " whooopee !  free film !  on demand ! "

So if you are contemplating making your own film either financed or with a few extra millions of extra cash, our advice is to be sure you have:

1.  sales to feed the fixed cost beast
2.  lots working capital and a line of credit
3.  a strong plant manager
4.  commitment to a 24 / 7 operation

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Topics: LDPE film, PEfilm

Homopolymers, Copolymers and Terpolymers - easy as 1, 2, 3

Posted by Joel Longstreth on Thu, Mar 31, 2016 @ 06:16 PM

The terms homopolymer, copolymer and terpolymer may sound like Latin or Greek to you.  In any case, they're not complicated.

Let's start with the common thread "polymer" first.  " Poly " comes from the Greek word for many.  As it pertains to plastic, it means many of the building blocks of monomers such as ethylene, propylene, styrene, etc. strung together in long chains to add up to polymers.

For more in-depth, visit our post on "where does plastic come from ? "

If the polymer is made simply from only one monomer, it is called a HOMOpolymer, or made from only one monomer.  POLYethylene, POLYpropylene, POLYstyrene, etc.  Far as I can tell, 1,2 Syndioatctic Polybutadiene is a homopolymer even thought the word is long.  Butadiene is the only monomer.

You guessed it - if there is another conjoined monomer ( not a mechanical blend ), you got a COpolymer.  Examples:  "ethylene vinyl acetate" or EVA for short - vinyl acetate monomer married to ethylene monomer, "styrene butadiene styrene" or SBS - styrene and butadiene building blocks,

And a TERpolymer is three monomers.  An oldie-but-goodie example is old fashioned phones which were made from "acrylonitrile butadiene styrene" or ABS.  Jump cut to present day - ABS is the default choice for 3 D printing.  Ethyl Methyl Acrylate, or EMA is all around us in upholstery commonly referred to as the "quiet film"

oldphone.jpgphoto courtesy of The Cathedral of Junk in Austin, TX

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Topics: polymers, plastic, copolymer, homopolymer

High Density HMWDPE Conundrum

Posted by Joel Longstreth on Thu, Mar 31, 2016 @ 05:20 PM

The acronyms HMWHDPE and  UHMWHDPE are confusing.  This discussion breaks down high molecular weight jargon.


Starting with the MW bit -  MW is short for molecular weight.  MWD, or molecular weight distribution is the full name.  Accoring to Handbook of Polyethylene by Andrew Peacock:

     " The size of a polyethylene molecule is normally described in terms of its molecular weight.  All polyethylene resins consist of a mixture of molecules with a range of molecular weights.. The average molecular weight and the distribution of chain lengths comprising a polyethylene resin profoundly affect is ( sic ) properties.  The molecular weights of molecules found in commercial resins may range from a few hundred up to 10 million... Often it is found that those molecules making up the higher molecular weight fractions also display the lowest levels of branching. "

Without getting deep into the five geeky ways to measure MWD, suffice to say that a high molecular weight resin is concentrated, very crystalline ( little short chain brancing ) and very dense. No surprize that by definition the density is high - high density ( HD ), or over .940 gm / cc.

So HMWHDPE = " High Molecular Weight High Density Polyethylene"

As you might expect, these resins are among the strongest polyethylenes pound for pound.  They are so viscous that the ASTM 1238 test for melt index had to be revised when the original Mitsui 7000F came along in the late 1970's.  Melt index is a measure of viscosity.  The test method consists of a cylindrical specimen in basically a heated can with a weight and a hole at the bottom.  The number of grams which come out of the hole in ten minutes is called the melt index.  This provides a crude predictor of the resin's personality.  Garden variety LDPE resins are about 2 grams or the verbal shorthand " 2 melt".   Mitsui 7000 F, American Hoechst GM9255F2 and Conoco / Dupont 5000 had values of + - 0.05.  So the HMW film resins are now tested with a " high load melt index", or "HLMI" which simply means higher weight to get a more meaningful sample.  Some prefer to make it sound more daunting by saying  "HLMIHMWDPE."  The most cotidien examples are single use grocery bags and star- seal trash bags.


Did you know ?  If there is not adequate haul-off speed, thicker HMWHD films will be weaker.  Why ?
the strength is a function of how well the polymer is "knitted" in the transverse direction ( TD ).  Here's how it works:  HMHD is made with a "stalk" or "wine glass" vis-avis "in the pocket" in LDPE.


 When the elastic energy dissipates, the bubble is created.  The tear strength and is a function of how fast the melt is oriented in the TD.  Simply slowing the line speed will create weaker, "splitty" film.

UHMWHDPE as you might guess is an even higher protein version with molecular weights starting around 2,000,000.  Those are long chains.  That said, most grades are in the .928 to .941 range which fall into the category of medium density polyethylene ( MDPE ). You can't make blown film out of it.  It has to be cast, or made with a slot die.  It is very stiff and slippery to the point of having a weird self-lubricating effect.  This trait makes it a popular choice for conveyor belts. I recently had a partial knee replacement.  Instead of a meniscus, I have a stainless steel end of my tibia moving against an insert of HMWHD in my fibula.  ( i have an image, but it's not for the faint of heart ).  There are lots of uses - the most popular is pressure-sensitive tape commonly referred to as "poor man's teflon." 

For the basics of PE, click here.

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Topics: HDPE, HDPE film resin, HDPE resin, UHMWHDPE, HMWHDPE

Packaging Film Blame Game

Posted by Joel Longstreth on Mon, Mar 21, 2016 @ 02:03 PM

A plastic film spec properly crafted by a packaging machine manufacturer ensures that the film can always be blamed  That's what an OEM told me last week.


Over the years, we have tried to partner with packaging machine manufacturers with no success.  Now I know why at the tender young age of 63.  We have even cited success stories in which our film has enabled frustrated plant managers to have consistent performance at speeds which exceed the OEM's claims.


To use a military analogy, the machine manufacturers are like the tank corps.  The tanks take the terriority and the infantry follows.  The machinery makers just figure the customer will figure the film out on their own.  When a machine is placed, the distributors find it first and swarm in.   Another set of problems arises from lack of continuity of supply when the distributor "shops" every order.

The setting of this worn out script which happened last week was the last stage of an installation.  The upstream issues were sorted out.  The last tech who was packing up and leaving said all three laminated film candidates were bad. Last remaining problem: good end seals, inconsistent back seams and occasional pinholes.  " FIrst time it ever happened" didn't do the customer much good.

The panicked customer contacted us.  I explained that if they were getting good end seals, they were hitting the optimum combination of heat / pressure / dwell. (The film is the same throughout, therefore the acid test variable is the sealing jaws.)  The heat and dwell time were both too high, resulting in "overcooking".  Turning the heat down - cooler - solved the problem.  Random pinholes in the end seals were the last problem.  

Turns out the packages were dropped three feet to the conveyor.  The molten film did not have enought time to crystallize.  The impact created the pinholes.  The pinholes disappeared when the conveyor was simply elevated.

We didn't get a sale out of it and consulted for a lot less than minimum wage.   

It's a natural human tendency to blame the party who is farthest away from the scene.  In the packaging business, the Napoleonic logic always blames the film first.  


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Topics: packaging machinery, packaging, packaging film

What Is Polyethylene?

Posted by Joel Longstreth on Wed, Jan 20, 2016 @ 09:19 AM

What is Polyethylene?

Polyethylene is comprised of long chains of the building block ethylene monomer. Ethylene monomer
C2H4 ( or just "C2" for short ) looks like this in English:


Ethylene monomer occurs naturally in both natural gas and as a component of naptha - the portion of a barrel of oil which cannot be refined into gasoline or oil.  So now you know that correlations between zillions of barrels of oil and plastic grocery bags are just more fake news.

                                      Did you know ?  Climacteric plants produce ethylene to induce ripening.


Polyethylene looks like this in English:


How these chains are put together determine the wide variety of resin properties. The fancy name for this is molecular weight distribution, or MWD for short.  MWD influences the 2 main properties which dictate a resins's personaliity - density and melt index.  The variations determine what applications a specific resin will work for.  

Polyethylene is the largest volume thermoplastic resin.  As such, it has a wide variety of uses.  Worldwide, there are probably hundreds of grades just for film alone.

What is Polyethylene?

Polyethylene is very inert.  The prelude to the iconic scene in episode 2 of season 1 of breaking bad illustrates this point.



The character Jesse called Walter from the store asking about what kind of plastic bin to buy.  Walter told him to look for the " LDPE 4 polyethylene " symbol on the bottom.  Jesse pours hydrofluoric acid packaged in a #2 HDPE #2 on the body in the bathtub.  After the bathtub falls through two floors, Walter explains that hydrofuoric acid is so aggressive that it eats through ceramic and metal ( but not polyethylene ).


Melt index (MI) measures viscosity by weighing the amount of plastic resin which extrudes from a cylinder with a hole in the bottom at 300 degrees for 10 minutes. The test method is ASTM D1238. The number of grams is the melt index, or MI.

A low melt index ( under 1 ) is referred to as a fractional melt  or less than a gram / 10 minutes.  Lower MI resins are used for pipe and profile extrusion.   It's common sense that resins with high viscosity (resistance to flow) are inherently strong. In film applications, fractional melt is suitable for shipping sacks and shrink film. Generally there is a trade off between melt index and clarity. The higher the melt index, the clearer the resin.  So a fractional melt is not a good choice when clarity is important and a high clarity "whole melt" or resin with a melt index of over 1.0 is not appropriate for shipping sacks.

By contrast, high melt index resins are used for injection molding.  For injection molding, it is desirable to have a material which flows easily to fill the mold cavity.

This has been a very cursory basic introduction.  To learn about where polyethylene comes from, visit our
post .  Polyethylene is processed by almost every thermoplastic process.

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Topics: polyethylene, LDPE, HDPE

Why Recycled Plastic Content is not Always Practical

Posted by Joel Longstreth on Tue, Dec 01, 2015 @ 06:47 PM

"Recycled Content" must score well in focus groups.  What else could explain why we are getting more requests for recycled content than ever ? 

 The economics of recycling is an entirely separate discussion.  Here are a few reasons why it is not always practical to recycle plastics.

" ( Post-consumer resins are) very important to some brand owners"   
-  Pedro Morales, KW Plastics


2ndplantbottle.jpg posttotalrecycled.jpgminrecycled.pngrecycsymbols.jpg

Problem:  With very few exeptions, recycled content compromises the properties of the virgin resin.  This has many ramifications.  Taking the exception first, let's look at polyethylene terephthalate a/k/a PETE #1.  It is not melted down and mixed back in with the virgin resin.  Instead, it is repolymerized.  The polymer is broken down into pure monomer and water and reassembled into pure polymer.  PETE is the only recycled resin approved for medical devices.  Not so fun fact:  the general public chooses to recycle only 1 in 3 PET bottles.

" We need ( post-consumer) polyethylene to be looked at like recycled PET is...  Recycled PET  is sold at a premium ( to virgin PET ).  ( Post-consumer) polyethylene needs that same kind of attention." 
- John  Picciuto, president of Western Plastics Association

For this to happen, post-consumer PE ( #2  & # 4 ) would have to attain the same FDA-approved status that PETE has.  

Really truly recycled plastic is picked up curbside, sorted, reground, repelletized and extruded again.  Internally generated scrap which is recycled internally does not fit the definition, but nobody cares or checks up.


At every step there is a chance for contamination.  Cross contamination with other polymers is one of the top issues for recyclers.  If the recycler is fortunate enough to have a batch of just one polymer, that's not even half the battle.   There are variations on the theme of each resin.  So contamination from the same polymer can compromise the final product.  With each heat history, the performance of the polymer degrades due to dissipation of the anti-oxidant.  Recycling makes the public feel good.  In reality it is downcycling to a less critical application.

Medical and Clean Room Packaging

Would anyone in their right mind want to use a medical device such as a syringe which might contain even trace amounts of toxins ?   We have made film for ostomy bags ( prolonged direct dermal contact ) for over 15 years. It's tough enough just to get prime virgin resin approved.  The resin has been put through four biotoxicity tests. Only somebody who wants to get sued would consider using partially recycled content.  Same goes for surgical drapes which come in brief contact with surgical instruments.

The same hospital that discards a blood presure cuff ( after charging the patient $25 ) for fear of a MRSA lawsuit will recycle / sterilize sharps because it makes economic sense.

disposable blood pressure cuff

Clean room packaging has a very low parts per million threshold for many chemicals.  Introducing the wild card of recycled content would risk recall of an entire shipment and loss of a customer, not to mention getting charged back for having to repackage.



Food and Water Packaging

PETE is also the only recycled resin approved for prolonged and direct food contact by the FDA.  Same logic applies to food.  Would you feel comfortable with your food being packaged in a container which might contain toxic chemicals picked up as the scrap is transported and processed  ?   Plastics already get enough of a bad rap due to misperceptions and misinformation.

BPA free is an effective greenwash marketing tactic.  Food packaging also gets scrutinized for what is known as leachables and extractables to be sure undesirable flavors are not migrating into food.

cuisinart.jpg images.jpgdreamstime_s_29972885.jpg


Deposit Slip and Coin Packaging


All bags in this category must have a tamper-evident immediate bond.  The three things which prevent tape from sticking are moisture, dirt and grease.  As such, they have a zero tolerance for slip, or erucamides which are commonly added to make bags open easily.  Adding in recycled content which may have trace amounts of slip could prevent the tamper evident tape from sticking.  The center image is fifty pounds of loose coins.  It is very difficult to qualify film made from prime first quality resin.  The bags are put through multiple drop tests.  If the seals fail, the film is always blamed, not the bag maker.  You guessed it - recycled resin would make the bags weaker and possibly keep the tape from sticking.  

There are plenty of other applications, but you get the idea.  The common thread - is it prudent to risk so much just to appease a great idea from the marketing department ?  

If you think so - Mesdames, Messieurs, place your bets !



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Topics: recycling, recycled content, recycled plastics

Surlyn - sometimes there is no substitute

Posted by Joel Longstreth on Mon, Nov 30, 2015 @ 03:17 PM

Surlyn the most effective, forgiving sealant layer ever invented.  Q.  What makes it so effective ?  Why the search for alternatives?  

A.    Surlyn's properties derive from what is called an ionomer bond.  An ionomer of sodium or zinc is in limbo shared with the orbit of polyethylene molecules.  This delivers unsurpassed tack and toughness and strength.  Surlyn seals through contaminants better than any other resin.  This is very important in the large market for subprimal meat packaging.

A.  part 2

Surlyn has many other applications besides packaging.

Surlyn's  is expensive and difficult to process.  Plastic film plant managers were early adaptors of metallocenes because Surlyn is hydroscopic and corrosive to extruder screws and barrels.  Surlyn has to be dried before extruding.  It is incompatible with other common polyethylene resins.  So blown film managers were early adapters of metallocenes.  

Metallocenes deliver almost the same hot tack characteristics without the aggravation.  Metallocenes are plug and play.  No drying, no corrosion and lower cost.


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Topics: surlyn

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