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We blog only about timely and relevant topics.  The software does not allow rearranging posts, so they are chronological.  You can browse by topic or keywords by scrolling down on the right side.

Brentwood Plastics blog

Polyethylene Price Increases after Harvey

Posted by Joel Longstreth on Thu, Apr 25, 2019 @ 04:03 PM

Replacement costs are uncertain in Harvey's aftermath.

chevronsign-1.jpgmurph449.jpgmurph313.jpg

Scroll down for updates

Predictions range from complacent denial from buyers of finished parts ( "it might go up" ) to "scary" from a decades - old plastics credit reporting agency.  

 

It's a fluid situation which is not moving by the hour like back in 1973 - 74.  In the wake of hurricanes Katrina and Rita in 2005, the CDI became the agreed-upon benchmark for polyethylene prices.  At this writing, the nominated three cent increase for August is generally accepted with a few exceptions.  The supply chain dominoes haven't all fallen yet, so there is no sense of panic or urgency among the smaller

 processors. It's like the force majeure letters never existed. 

Large volume buyers of finished goods are fighting the August 3 cent increase tooth and nail.  What is happening does not fit their Walmartized reality.  The large volume extruders have laid  people off and they are scrounging for resin.  Dow's second letter announces a second price increase, but fails to mention allocation.  Customers are asking us for documentation because it is difficult to pass price increases along these days.

Herewith is a compilation of letters and updates we have received in Harvey's aftermath.  

Harveypriceincreaseletters

 

 
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Topics: PE resin price, price for polyethylene, polyethylene price,

The Truth About Coextruded Film Packaging

Posted by Joel Longstreth on Thu, Apr 25, 2019 @ 03:59 PM

A properly designed machine has no unnecessary parts.  Anybody who makes coextruded multilayer plastic films will tell you a simple monolayer plastic film is sooo 1970 !  Getting coex specified is a barrier to entry to monolayer film producers.   Complex is sexy.  Simple is boring.  Problem: There is an interdependency between the layers.  If something goes awry with one layer, it affects the entire structure.

dreamstimeextrasmall_5573876.jpg

In general, it's a good idea to ask somebody what they do for a living before you ask them for advice.  The questions you need to ask proponents of coextruded blown film:

Q.   Why does the structure absolutely have to be coex ? 

A.  When each layer has a specific job to do.  Hosokawa Alpine now has an 11 layer line.  Seriously ?  
is 11 enough ?

Examples of must-have coex: 

differential COF - high slip / low slip  ( mattress bags )
light blockout ( white / black election signs )
differential melt temps ( vertical form/fill/seal )

A common example of 2 layer coex can be found in a cereal or crouton box.  The verbal shorthand is "chip film" or cereal liner.  This 2 layer structure is the low, mature end of coex.  

cereal box.jpg

The outer layer is HDPE for barrier.  The LDPE is for sealability.  See our blog post on PE

Election signs and overnight envelopes must be 100% opaque and require a "core" layer of black.

 

A more complex example is the category of meat films.  They commonly have a core layer of EVOH.  Since the viscosity of the core layer is so much different than the outer layer usually of PE, a "tie" layer which takes up the slack in viscosity between the layers is necessary.  So just like that, you're up to 5 layers.  The Achilles heal of EVOH is the tie layers.  If they are off, it's a nightmare scenario.  EVOH is very hydroscopic.  If the EVOH layer is not isolated from the ambient, it will degrade. 

A big selling point with die manufacturers is enabling the extruder to bury scrap that would otherwise be discarded in one or more core layers to keep costs down.

Here are a few examples of films which absolutely do not need to be coex:

Blue / white surgical drape films.  Over 50 years ago, somebody made the case for a 2 layer laminate as a pinhole-free film.  The theory is that the chances of 2 pinholes lining up is infinitesimal.  True for a lamination, but not for coex.  Coex film can create voids as it exits the die just like monolayer film.  When coex came along, the film was made in 2 colors to emulate the lamination.  Albeit slowly, drapes such as mayo stand covers and nurse's back table drapes transitioned to single layer.

Frozen food IQF packaging.  Barrier films promoted for frozen food have a feelgood security blanket factor, but are unnecessary.  We have made monolayer film for IQF frozen film for decades (both form/fill/seal and thermoformed bone guard ).  By the way, barrier won't prevent freezer burn.


Coex layers are described by letters, each designating a resin type.  An " A/B/C/B/A " structure is a symmetrical structure.  Going back to the example of meat film, the A layer is LDPE, B is the "tie" layer and "C" is the nylon or EVOH "core" layer.  C does not stand for core. 

drawbacks to coex:

scheduling with ramifications for longer lead times and higher minimums

Minimizing scrap is even more important in the coex realm.  Instead of taking less than an hour to change over with a single layer film, it can take literally all day to set up a coex structure.  After a coex order is set up, staying in that structure as long as possible makes common sense.  It is very expensive to break in to accomodate a customer who calls with a hot fill-in requirement.  All the time an order is being set up, the extruder is running scrap.  It takes as long as it takes for transition materials to clear out and for the new structure to do what operators call "settle down."  There are no short cuts.  The higher setup costs must be amortized with high minimums.  Some coextruders such as CharterNex won't talk to you about running a trial even if you offer to pay for the scrap and machine time.  It's 10,000 pounds minimum.  

did you notice ?   coex films are very rarely an even number of layers, they are almost always an odd number of layers

 

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Topics: coextruded film, coextruded films, multilayer film, coex films

Is plastic from oil ? What is plastic made from ?

Posted by Joel Longstreth on Thu, Apr 25, 2019 @ 03:58 PM

Plastic POLYmers are made from building block MONOmers.  The naturally occurring monomers (feedstocks ) can be derived from plants, coal, natural gas or oil.

dreamstime_xs_23706085  dreamstime_xs_39797967  dreamstime_xs_22681245  dreamstime_xs_11433558 
tater4

Long chains of monomers are polymers.  Ethylene becomes polyethylene, propylene becomes polypropylene, styrene becomes polystyrene, etc.  A polymer comprised of only one monomer is known as a homopolymer.  A polymer with two monomers is called a copolymer ( ethylene vinyl acetate EVA )and you guessed it - three polymers is called a terpolymer ( acrylonitrile / butadiene / styrene or ABS ).

http://www.brentwoodplastics.com/polyethylene

Bio-based plastics from plants are promoted as better for the environment because of their renewable sources vis-a-vis types of plastic made from non-renewable petroleum-based fossil fuels.  The giant food companies quickly realized "gen 1" bioplastics would skyrocket their raw material costs..  Just as ethanol increased prices for other crops, if more land is used for plastic feedstocks, the price of other crops will increase.

Plastic can be derived from both plants and conventional feedstocks without being biodegradable.  Braskem's so-called green plastics are plant plastics derived from cane sugar and are not biodegradable.  Their polypropylenes and polyethylenes are indistinguishable at a molecular level from fossil fuel based polypropylene and polyethylene. It is interesting to note that Braskem is putting on a billion pound annual capacity plant in La Porte, TX.  Their feedstock choice ?  Fracked American natural gas, not ethanol derived from sugar cane.  Their CEO praised the American shale gas feedstocks.

In the US, most plastic is made from natural gas.  The resin producers simply take what they want from the natural gas pipeline and put the rest back.  PVC is a combination of ethylene and chlorine salt. http://www.pvc.org/en/p/how-is-pvc-made

The other choice of feedstock is naptha.  Naptha is the creme de la creme of a barrel of oil which cannot be refined into gasoline or motor oil.  Naptha is the feedstock of choice in the rest of the world because it is sort of a by product of the refining process.  So it is true that some plastics, not all plastics, are made from oil. 

20150918_113134

These items could all have been derived from oil or natural gas.  Display courtesy of Ocean Star Drilling Rig Museum in Galveston, TX. 

Thus we see that correlations between barrels of oil and plastic bags are not taken seriously by anyone in the plastic industrial complex. 

Here is a decision guide I put together to capture the ramifications of plastics made from different feedstocks:http://info.brentwoodplastics.com/bioplastics-or-conventional-plastics?&t=61295.  

Perception is reality.  Fact checking is obsolete.  Feel good press releases such as this one from Subway play into the public's ignorance about where plastics come from:http://www.prnewswire.com/news-releases/subway-restaurant-chain-continues-to-live-green-with-salad-bowls-made-from-95-percent-recycled-materials-147592125.html.   Lego bought into Braskem's marketing message and in turn duped the general public. 

Remember freshman econ about factors of production ?  Where plastic is made and what plastic is made from influence the cost of plastic.  The major factors are feedstocks and exchange rate. 

Like it or not, the US gulf coast is poised to once again become the low cost producer of volume thermoplastics.  Thank you, George Mitchell !     For polyethylene alone, there is an additional 20 billion pounds of annual capacity going on stream by 2021.  These are not projects which have a 5 to 10 year investment recapture.  They are more along the lines of 40 to 50 year life expectancy.   

http://www.plasticsnews.com/headlines2.html?id=25219

:

How plastics degrade is the other side of the coin.  There are a lot of misperceptions on this subject.  
With the exception of PVC, most plastics degrade back into their harmless monomer building blocks.   It doesn't take millions of years; more like a half life of hundreds of years.  This will be a problem for future generations when the toxic chemicals largely from households start to leak into the water table.  Fortunately the plastic landfill liners will protect the environment for a few hundred years. 

 20150918_143812

The author in front of Lyondell Chocolate Bayou resin plant in Texas with examples of natural gas derived high density polyethylene ( HDPE ) products.  

For a discussion of why plastic recycling rates are so low, watch this video. 

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Topics: what is plastic made from ?, plastic made, plastic from oil

Green Wash - What is Green Wash Plastics ?

Posted by Joel Longstreth on Thu, Apr 25, 2019 @ 03:56 PM

Greenwashing is ubiquitous. 

Claims of plastic biodegradability are vague and play into the public's emphasis on end-of-life.

The FTC lags in prosecuting specious claims and only prosecutes the most flagrant offenders.

http://www.ftc.gov/bcp/grnrule/guides980427.htm


So how can one make an informed decision about ostensibly eco friendly biodegradable plastic without a 3 hour course on confusing biodegradability standards ? 

ASTM D 6400, ASTM D 6954-04, ASTM D 5511, ASTM D 5526, ASTM D 7021, ISO 15985, EN 14995, EN 13432, ISO 17088 to name a few.

Compliance with specific test methods is rarely mentioned at point-of-sale.

The sad truth is there is a lot of biodegradable patent medicine being peddled these days.  Us plastic nerds have heated debates about these standards while this information doesn't usually reach the consumer.

If you don't know your PLA from your PHA or your PHB, if you don't know your oxobio from your bioplastic, here are 3 dumb questions which will make you an informed consumer:

Does it comply with at least one standard ?

Does the companies' website have one study to substantiate their claims ?

If the product claims to be compostable, is it home compostable or must it be transported to a commercial composting facility ?

If the onset of degradation is specific, such as 2 weeks after the product is used, how does the plastic know it is time to initiate degradation ?  In other words, how is the plastic so smart it knows it is no longer on the supermarket shelf ?

If the bag, usually a newspaper bag, claims a percent of POST CONSUMER content, did the plastic really get discarded, collected, sorted, returned and repelletized then made into plastic film again ?  According to the FTC and ASTM, true post consumer means made from previously used product.

http://en.wikipedia.org/wiki/Greenwash

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Topics: biodegradable plastics, green wash, greenwashing, what is greenwash ?, green washed

EPR Extended Producer Responsibility - You will pay, not producers

Posted by Joel Longstreth on Thu, Apr 25, 2019 @ 03:51 PM

Extended Producer Responsibility ( EPR ) and product stewardship are ideas which are gaining traction globally.  Vilifying corporations may be satisfying to NGO's but the expense of recovery will be passed along to the consumer.  

 

 

The logic is that a corporation must be responsible for the entire life cycle of a product all the way to final disposal at end-of-life ( Germany holds the manufacturer legally responsible for the entire life cycle of the product under what is called "comprehensive outcome" ).  This would include re-use, take back and/or recycling. Problem: this costs money which is not presently included in the cost of the item.  Now the consumer pays for only the cost of the item hopefully produced with a small profit and quite possibly at loss. There is simply not enough profit built in to absorb these additional costs.  Packaging does not have a secondary use and cannot be repurposed.  

Container deposit legislation shows the consumer that recycling and recovery costs are extra.

The cost of disposing of toxins is often included in the sale price of some items.  Extending this principle to inert, non-toxic plastics is a bit of a stretch.  Just my opinion.  Container deposit legislation shows the consumer that recycling costs more than the container by itself.

Follwing the logic, the plastic processors are responsible for the behavior of the consumer who chooses to litter instead of recycling.  2 out of 3 containers made from #1 PET, the most recyclable of all polymers, end up as litter or landfill despite the best efforts of large corporations to encourage recycling.

Crafting EPR legislation might get complicated.  How would the cost be allocated ?  How much should the resin manufacturer be responsible for and how much for the processor ?  So-called "triple bottom line" concepts such as environmental full cost accounting ( EFCR ) and true cost accounting ( TCA ) attempt to capture the costs of the entire life cycle. They are open-ended and subjective at best.

file:///C:/Users/Joel%20Longstreth/Downloads/EPR_Packaging-Fact-Sheet.pdf

If the blame for plastic waste gets shifted to us plastic straw men, reality is the consumer will ultimately pay. Just as corporations pass along the costs of taxes, the plastic industry will pass these costs along.  

 update January 14, 2019

Look who's paying the sugar tax in Seattle.

 

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Topics: EPR, extended producer responsibility

Designing for Recycling and Sustainability

Posted by Joel Longstreth on Thu, Apr 25, 2019 @ 03:50 PM

Cradle-to-Cradle, Recyclability, Sustainability and reclamation have historically been low priorities in design considerations.  The biggest obstacle to these goals is dissimilar materials in the same product.  Just as form follows function, selection of raw materials teamed up to do a job is determined by the properties raw materials can deliver.

 

Recycle Across America correctly attributes the recycling collapse and crisis to contamination.  

"... the collapse of recycling is primarily due to high contamination levels in the recycling stream.  Contamination cripples the economics of recycling.  The process to remove contamination reduces profitability, driving up the cost of recyclables, thereby preventing many manufacturers from reusing recycled materials. As a result, they continue to deplete finite resources at alarming levels." 

Note how economic sustainability dovetails with environmental sustainability.  The recycling business is tough at best because prices drop when there are more recycled materials are on the market.  There is not enough margin to absorb the additional cost of sorting.

It's not complicated.  The more dissimilar materials are contained in a product, the more difficult it is to
recycle for practical purposes.  If a product contains more than one polymer, it should be labeled a resin identification code ( or RIC for short ) symbol 7.

recycle7.png

Sweden has it down to a fine art.  They claim only 4% of their discards end up in the landfill. 

 

So just make the product out of the same resin.  Simple solution, right ?
Problem: one resin can't deliver all the attributes needed

Often the resolution to a problem is meeting halfway.  This mailing envelope solves the debate over paper or plastic.  Instead of an all polyethylene #4 recyclable envelope, it is made from both polyethylene bubble pack and kraft paper.  

pregis.jpg

Proponents of plastic often ask why cut down a new tree when you can use an old dinosaur ?  The rejoinder is usually "you're still usin' fossil fuels, man".  This brilliant example of an unrecyclable #7 satisfies all demographics.  Proof that it satisfies the demands of the consumer for green products is it's ubiquitous presence in UPS stores.  

A cotidien example of several resins in one product is a soft drink cup with a straw and lid.  It has three different polymers with three different job descriptions:  The stiff and pliable straw is polypropylene, the rigid lid is polystyrene and the paper is coated with low density polyethylene.  One resin is not versatile enough to do all three jobs.

 

 

At Sustpack2016, the common threads of marathon presentations by large companies were source reduction and landfill reduction.  They have all made great initial strides mainly through reduction of corrugated packaging. Just my opinion - it will be more difficult to maintain the same rate of progress after another few years.  Corrugated recycles allright.  It also cuts down trees and uses oodles of fossil fuels.  Chemical runoff is minimal compared to decades ago.  

 

Consumers feel best about recycled content to assuage their irrational conditioned consumer guilt.  Using less, or source reduction, is the most incontrovertible way to go green.  But it's too abstract and not fungible.  

It's an issue for not just the flexible packaging industry.  The green building culture is scrutinizing materials with emphasis on cradle-to-cradle. There are several recent success stories such as the Long Center for performing arts in Austin, TX.

 

This is not new.  Humans have been recycling construction materials for millenia with an efficiency motive. Construction waste is one of the major contributors to landfill, but that's another conversation.  Here is a great infographic about recycling across the globe and in recent U S history.

Like everybody, the meeting and convention industry is under pressure to show they are going green.  
bins.jpgconstructiongarbage.jpgLVrecycle.jpg

Recently, it has become common practice to place a recycling dumpster next to the dumpster for non-recyclables.  What the convention industry used to pitch is turning out to be a massive trove of raw materials.
Here's the bargain: the recycler gets the cast-offs for free.  His cost of goods is the cost of hauling and sorting.

A big problem for both conventions and builders alike is carpet.  Carpet can have several components which makes it hard to sort.  Despite this obstacle, carpet recycling is catching on.  Cleaning and re-shipping carpet is a major headache for convention contractors ( the people who put up the booths, signage and install the
carpet ).  For example - Freeman the industry leader, has at any given moment 300,000 square yards of carpet in a cook's pot being cleaned and recycled.  The trend is toward nonwoven single-use polypropylene #5 used one time and sent to the recycler.  There will be a tipping point if the price drops to where the cost is less than transport + cleaning + transport again. 

The bad news is that even if products could be made with only one resin, it would not be a solution.  The major obstacle to recycling is indifference from the general public.  Proof is the low recycling rate of water bottles.  They are made from polyethylene terephthalate ( PET ) #1.  PET is the only commodity resin FDA approved for 
food contact and medical after repolymerization.  The recycling rate has dropped to 30.1 %.  More than 1 in 3 water bottles are discarded despite the efforts from giants like Coca Cola to make recycling easy.

Could it possibly be that consumers just aren't that concerned about the environment and only pay lip service ? 

It's more fun to blame and vilify evil corporations.

For more information on the 7 basic commodity resin identification codes, watch this short video.

 

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Topics: plastics recycling,, sustainability, resin identification codes, RIC

" Gen 3 " Plastic Packaging

Posted by Joel Longstreth on Thu, Apr 25, 2019 @ 03:48 PM

Giant retailers and consumer product companies are under tremendous pressure to be perceived as green and sustainable.  They are somewhere between frantic and panic.  Rumor has it the CEO of WalMart wants produce bags to contain partial bioplastics by 2020. Meantime, the major plastic resin producers are doubling down on conventional fossil-fuel based resins.  Sounds like a script straight out of  The Innovator's Dilemma.

 

Jimmy Durante said "everybody wants ta get inna de act" apparently does not apply here.  Timing is just as important to biodegradablity as it is to comedy. ( Dow divested their interest in Nature Works years ago. ) At the recent NPE show, there were only two new US based exhibitors and they were not from the major resin producers.

Biologiq
a
nd
Danimer Scientific

the rest were from China

Jinhui
a
nd

Kangrunjie  ( can't link to their site )

 

Gen 1 " is defined as plastics derived from fossil fuels.

"Gen 2" is plastic derived from agricultural sources or "biopolymers ".

Nobody knows what " Gen 3 " will look like.  Maybe a hybrid ?   The first forays into Gen 2 did not catch on initially because a) consumers will not pay a green premium and b) timing.  Bags put on the shelf in May fell apart in stores by July.  Large food companies have seen what ethanol has done to raw material costs.  If plastic packaging made from agricultural sources crowds out arable land, food costs will skyrocket.  

Another aspect to consider is the involvement of the FTC.  They are finally cracking down on ostensibly biodegradable plastics, or what we call " additive cowboys ".  

 

It's all about perception.  Anything derived from fossil fuels is perceived as inherently evil and made from a source which is not sustainable.  Braskem has done a fabulous job marketing their "green" polyethylene and polypropylene made from sugar cane.  They get a premium and won't talk to you unless your volume is 1,000 metric tonnes annual - take or pay.  These resins do not biodegrade any faster than petroleum-based plastic.  Braskem is putting on a billion pounds annual capacity in La Porte, TX.  The feedstock ?  Fossil fuel natural gas.

With painstakingly politically correct word choice, Lego announced their selection of " green " plastic.  

There are two approaches to a quick fix.  Either "greenwash" ( defined as no change, spin only ) or make hasty changes out of fear of social media.  Notice how much emphasis is put on what a product does not contain these days ?

Bisphenol A is an excellent case study.   " BPA free" is an insult.  Only polycarbonate and PVC use it as a catalyst.  There are trace amounts in the final product.    If your product is made with any other resin, just say        " BPA free" and voila !   You take advantage of the consumer's fear and lack of understanding.which may be just enough to stimulate an impulse purchase.

Sometimes the alternative to the vilified material is worse.  Those who reacted to NGO's clamor for a BPA ban by substituting BPS and other materials were the biggest losers.  In retrospect they look impetuous.  The quiet epilogue: BPA's recent clean bill of health despite being put on California's prop 65 list and the EU's possible ban.  Did the NGO's give a public apology ?   A "never mind" a la Emily Latilla ?

 

Of course not.  The disingenuous virtue signaling malcontents just move on to another faux outrage cause.

The latest angle is apparently a hybrid of fossil fuels and potato starch from a company called Biologiq.  They offer both compostable biopolymers and combo fossil fuel resin / biopolymers.  The hybrid is chasing arrow #7, or "other" which makes it is not recyclable with other polymers.  They say the time is right.  The CEO of Walmart wants all their potato and apple bags converted to Biologiq yesterday. 

Let's look at how this could play out.  For starters, well-meaning consumers will recycle the potato resin bags with the other bags at the store entrance resulting in contamination.   If it takes off, Biologiq will need more than the by-products of potato chips.  What do you think would happen next ?  If you said, "potato prices will increase", go to the head of the class.  For now, the claim of "eco friendly" is not on the FTC's radar.  If the FTC wants a more precise definition of "eco friendly" it's going to be a problem. 

H. L. Mencken said " for every complex problem there is an answer that is clear, simple and wrong".  

To make an informed decision about conventional or biopolymers, click on the purple box on this page.

 

 

 

 

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Topics: eco friendly plastic,, sustainable packaging,

What Is Polyethylene?

Posted by Joel Longstreth on Thu, Apr 25, 2019 @ 03:46 PM

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.jpg

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:

polyethylene

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

Factors Determining Shelf Life

Posted by Joel Longstreth on Thu, Apr 25, 2019 @ 03:44 PM

Shelf life is subjective.   The definition of "use by" or "sell by" date depends on criteria and varying degrees of emphasis.   These dates are understandably conservative.  

 

Let's look at both the judging criteria and interdependent factors affecting shelf life.

The judging criteria are:

odor and taste      appearance      texture
Obviously the most common sense must-haves for consumer satisfaction, these criteria do not pick up on other factors which have the potential to sicken or kill the customer.

weight loss
Package must not dissipate moisture to comply with weight and measures.

micro loads  
Critical in fresh, unpasteurized food.   Judging by total micro load is an oversimplification and puts the processor in an impossible position.  Something is going to grow on the surface of the product, either friendly aerobic
( in the presence of oxygen ) or anaerobic ( no oxygen present ).   It's a zero sum game microbiologists call competition.  The battle between these types of bacteria dates back to pre-Cambrian times.  Aerobic = good, friendly.  Anaerobic = bad.  Anaerobic is where emerging pathogens such as shigella, campylobacter jejuni and classic clostridium botulinum thrive.  What's scary is listeria mycocytogenes  grows in both conditions and is undetectable to odor and taste.  A bag of salad which has been stored at 38 degrees for 25 days may look good, feel crunchy and taste fine while fraught with stealth populations of listeria.

Think petri dish.  The product is a growth medium for cultures of friendly and dangerous bacteria.  Microbiologists talk about " logs " of micro loads.  This is short for "logarithmic" growth starting with "seed" populations.  Fresh cut fruit has taken longer to catch on due to the higher amount of sugar vis-a-vis vegetables. 

Agricultural and Agri Food Canada ( AAFC ) for short usually picks up on listeria contamination in salad first.  No real surprize there.  The bags have a week to incubate in transport from California with greater chance of temperature abuse.

headspace analysis
Tracking headspace gases interpolates when the package will go anaerobic.  The biggest mistake in headspace analysis is not getting enough data.  Simply checking one or two packages every few days does not provide a true picture.  The right way is to sacrifice a lot of product, check several packages every day then graph the results after throwing out the highs and lows.

processing factors

raw material  
This refers to either the animal or vegetable and how it was handled not just in transport to the processing facility. In the case of vegetables, it's smart to look at conditions before the seed was put in the ground.  If manure was used to fertilize, Escherischia Coli has a way of finding it's way into the processing plant as seed populations.  Avoiding cross contamination requires close attention to HACCP.

processing conditions  
Before personnel set foot on the production floor, it is best practices to educate them about sanitation.  Seed populations of pathogens often enter the plant on the hands of employees.

packaging  
Packaging cannot make an inferior product into an acceptable product.  OTR is key.  For meats, fish and cheese, a barrier is essential.  For fresh produce the proper barrier or lack thereof is the lynchpin.  A lot of emphasis is put on OTR.  An overlooked factor is the CO2 transmission rate - about four times the OTR.  So the highest OTR without spoiling prevents the dnagerous anaerobic CO2 buildup.

distribution chain

 

Temperature during transit is not a factor with pasteurized canned or bottled product.  Wines can be ruined in just a few hours in a hot car.  For fresh products, when measuring headspace it is important to mimic as closely as possible the anticipated temperatures in the " cold chain".  This can be a touchy subject.  Who wants to be the one who has to tell their customer spoilage is due to breaks in the cold chain at  the customer's distribution hub ?  Besides, every Thermo King is at exactly 38 degrees F throughout the entire truck, right  ?   Sending the customer the impartial results from a Ryan often backfires.

I have seen several attempts to quantify the definition of shelf life by assigning a point value to each category adding up to a total of 100.  It never works.  If an item fails in any one of the criteria, it fails.

did you know ?

In the early 1800's there were an estimated 15,000 stills in Kentucky.  Distilling whiskey was a very rational alternative to selling corn.  The reason: practically indefinite shelf life.

The most toxic substance on this planet is not man made.  It is produced by Clostridium botulinum to defend itself against other predatory micro organisms.   Botox anyone ?

Meals Ready to Eat, or MRE's are expected to have a shelf life measured in years.  Exactly how long is time and temperature dependant.  If an MRE is puffy, you now know why it's gone bad.  It has gone anaerobic.

It is estimated that 40% of food in undeveloped countries spoils en route to market.  In the US, consumers pitch about 40% of their food.  Neither one is good from a methane generation standpoint. 

 

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Topics: shelf life

Fracking shale gas - how it affects price of plastic

Posted by Joel Longstreth on Thu, Apr 25, 2019 @ 03:39 PM

Feedstocks are the major drivers of the price of plastics.  Whether you are for or against fracking, it has had a dramatic effect on the price of anything derived from natural gas or oil. 

frackpic.jpg

Not so long ago, Alan Greenspan expressed concern about depletion of natural gas in the U S.   Time was "peak oil" was sacrosanct.

http://online.wsj.com/article/SB10001424053111904060604576572552998674340.html  The time horizon for peak oil gets pushed farther into the future.  Now it's cool to say "peak demand".  Soon we will have benevolent government control of our electric cars and solar powered airplanes.  About a year ago, Cheniere shipped their first order of fracked natural gas to India.  Who'd a thunk it ?

Skip ahead to today and we are running out of places to store natural gas thanks to the advent of fracking.  As of March 2016 there is over 2.536 trillion cubic feet in storage.  The active rig count for oil is down to 315.

http://www.plasticsnews.com/headlines2.html?id=25382

So how is this relevant to plastics ?  The debate about which feedstock choice for making plastic is sustainable is a hot topic.  Many major food companies are against bioplastics because they will drive up the price of their raw materials just as ethanol has driven up the price of protein.

Exxon and Chevron are confident enough about the continuing natural gas discoveries that they have commssioned capital intensive plants which will have a combined annual capacity of  over 5 billion pounds. Obviously, the factors of production are most favorable here in the US gulf coast.  They plan to make plastic from US natural gas, not oil.  Same goes for Braskem who is cranking up grass roots capacity for fossil fuel-derived plastic despite their success with their "green" plastic derived from sugar cane.  The common thread is that with the information they had when these plants were commissioned, the US looked like the low cost producer.  They made the right call.

The world consumed over 450 billion pounds of plastics in 2011.  About 99 % was derived from fossil fuels, though plastics production only accounts for 4% of overall fossil fuel usage.  Polyethylene capacity will increase from 324 billion pounds in 2017, growing at a rate of 3.4 %.  At the same time, global demand will increase 4.7 %. Much of that demand will be exported from American resin plants in Texas and Louisiana.

The global price of oil is a big factor in determining who has the best price for commodity thermoplastics.  If the price of oil drops enough, plastic derived from naptha will be cheaper than plastic derived from natural gas.

For the foreseeable future, most of the market is not ready to pay triple for plant based bioplastics, so plastics from natural gas looks like the most practical choice.  Major food companies are waiting for "generation 3" of bioplastics.  They do not want plastic made from agricultural sources because it would raise the price of their raw materials.  They have seen what ethanol has done to the price of protein.   " Fossil fuel" plastic is anathema to the focus groups, so they are waiting for a solution which is palatable to the general public that will not raise prices of other commodities.

Fracking will continue to widen the price disparity between fossil fuel plastics and bioplastics.  That is, unless the rules change.  The Obama administration is issuing a constant stream of regulations with the obvious end game of regulating the frackers out of business.  Despite oil and natural gas at an all-time low, the administration wants to implement a $10 per barrel tax on oil.  Hillary Clinton has stated that if all her conditions are met, there will be no more fracking. 

update January 17, 2017

What a difference a few years makes !  The scale of investment by globocorps in U S resin capacity is staggering.  It's happening not just in the traditional gulf coast, but places like Bartlesville, OK and West Virginia.  The reason why is simple: the US is the low cost producer.  Note the reference to fracking in this latest announcement of $ 1.7 billion investment in Texas.

 

 

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Topics: fossil fuels, plastic made, price for polyethylene, fracking

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