ADVANCED BIO-FRIENDLY POLYMERS

Györgyi Szarka

Food packaging and use of stabilizers

Packaging materials

• Paper• Metal• Plastic:-PP

-PET box

-PS

-PVC

-Polyesthers foil

-PE

http://www.foodpackagingforum.org/Food-Packaging-Health/Food-Packaging-MaterialsC. Silvetre et. al. Prog. Polym. Sci., 36, 2011, 1766.

light, transparent, unbreakable,minimal use of material,good gas and aroma closing, valuable raw material

Polymer additives

FUNCTIONAL• Plasticizer• Lubricant• Antistatic • Filler• Foaming / Crosslinking• Colorant• Flame retardant

PROTECTING• Heat stabilizer• Light stabilizer• Antioxidant

TYPICAL STABILIZERS

Primary stabilizers/ antioxidants:Hindered phenols, aromatic amines

Secondary stabilizers / peroxide decomposers:Organic thioesters, phosphites and metal-thiocarbamates

Chelating agent/metal deactivator:Organic phosphites and hydrazides

Problem related to food packaging

• Migration of additives

• Chemical changes during processing

• Health problem due to synthetic stabilizers

FOODFOOD FOOD

Strategies to avoid migration

• Macromolecular stabilizer

grafting by chemical decomposition of 1,2,2,6,6-pentamethyl-4-piperidyl-acrylate (PMPA)

• Connect the stabilizer to the polymer (grafting / copolymerization )

M. L. Binet, S. Commereuc, P. Lajoie, J. Lacosta, J. Photochem. Photobiol. A: Chem., 137, 71, (2000)

T.L. Pattorn, J. T. Horeczy, D. E. Brown (to Esso Research and Engineering Co.) U. S. 3,477,991 (1969)T. Iwata, J. Sasaki (to Mitsui Petrochemical Co., Ltd), Canadian 876,769 (1971)

1. time antioxidant used in copolymerization with olefin under Ziegler-type conditions

OH

C(CH3)3(CH3)3C

(CH2)3CH CH2

OH

O

n m

3

Changes during processing

• Manufacturer should guarantee not only the safe use of the additive but the product(s) of them after processing

There are some health concern in relation to BHT, the quinone form causes lung cancer in mice. Human health problem has not been proved yet.

HO RPO2 + O RPOOH +

O R O R

PO2 + O R O

R

OOP

Natural materials in packaging

Environmental and health problem due to synthetic stabilzers

•Natural antioxidant: lignin, carotin, quercetin

•Radical scavenger: vitamin E

carotin

vitamin E

quercetin

BIODEGRADABLE POLYMERS:

• PHA, PHB, PLA

(Ecoflex, Ecovio)

1. Brocca, D.; Arvin, E, Mosbaek, H: Water Res., 36, 3675-3680, 20022. Pataki P., Imra B., Földes E., Pukánszky B., Műanyag és Gumi, 2012, 1

O

HO

O

OH

OH

OH

O

HO

OH

1935/2004/EC regulation

• This Regulation covers all materials and articles that are intended to come into contact with food: all types of packaging, bottles (plastic and glass), cutlery, and even adhesives and inks for printing labels.

• They must under no circumstances transfer substances to the food with which they are in contact in quantities likely to:

– endanger human health;– bring about an unacceptable change in the composition of the food; or– bring about a deterioration in the organoleptic characteristics thereof.

• Active materials and articles: intended to come into contact with food: materials and articles that are intended to extend the shelf-life or to maintain or improve the condition of packaged food. They are designed to deliberately incorporate components that would release or absorb substances into or from the packaged food or the environment surrounding the food.

• Intelligent materials and articles intended to come into contact with food: materials and articles which monitor the condition of packaged food or the environment surrounding the food.

Active and intelligent material• Oxygen absorbents: ascorbic acid, metal-sulfides, glucose oxidase,

catalase enzyme, amorphous polyamide

• Oxygen exclusion: ethylene/vinyl alcohol closing coating

with Fe-compound• Water vapour absorbents: molecular sieve, silica, CaO, Al coating• Moisture controller: salts• Antimicrobial packaging: sorbic acid, Ag

Summary

• The use of plastics is rapidly expanding in foodpackaging industry

• The new products are more sophisticated and fit

better to the improved claims with specialpolymers and active additives

• These materials should improve not only thephysical, chemical but the health safety properties of the package (EU) due to

- reducing migration- and full controll of all the used materials and evolved products during processing

Macrostabilizer strategy

Compatibilizer

Hyperbranched polymer

Stabilizers

Acknowledgement

HUSK /1101/1.2.1/0209

Hungarian Academy of Sciences

Research Centre for Natural Sciences

Institute of Materials and Environmental Chemistry

Department of Polymer Chemistry

Packaging• Barrier protection - A barrier from oxygen, water vapor, dust, etc., is often required.

Permeation is a critical factor in design. Some packages contain desiccants or Oxygen absorbers to help extend shelf life. Modified atmospheres or controlled atmospheres are also maintained in some food packages. Keeping the contents clean, fresh, and safe for the intended shelf life is a primary function..

• Convenience - Packages can have features which add convenience in distribution, handling, stacking, display, sale, opening, reclosing, use, and reuse.

Macromolecular stabilizers Advantages

– Very low migration to the surface– Long and predictable effect– Properties (eg. solubility, miscibility) can be

easily modified by molecular weight and functionality

Disadvantages– Further functionalization reactions, which are

often expensive and time consuming

INTERPACK 2011

Other additives• Antiaging additives:

BHT has been cleared by the FDA

The branched polymers have all the beneficial properties of dendrimers.

Synthesis: different one-step reactions Polycondenzation of ABn-type

monomers Sequential grafting INIMER POLYMERIZATION Self-grafting of polymersSelf-grafting of polymers

no special main chain statistical distribution of branch points

repetitively branched molecules start-up of one well defined central core low viscosity

high chain-end funcionality developing of generations can be made by only expensive, difficult and time consuming methods and reactions

Dendrimers:

Hyperbranced polymers:

MULTIFUNCTIONAL HYPERBRANCHEDPOLYMERS

ONE NEW CANDIDATE FOR BIO-FRIENDLY STABILIZER:

HYPERBRANCHED POLYGLYCEROL

Properties Synthesis: cationic or anionic Ring Opening Polymerization of glycidol

Well defined product (Mn, PD, number of OH-groups) Good solubility in water OH-groups can be functionalized easily Biocompatible

─ does not induce an immune response─ oligomers are FDA approved for food and pharmaceutical additives

OOH

baseslow monomer

addition

O

O

O

O

OOH

OHOH

O

OH OH

OOH

OH

OHOH

CoreCore

THE TARGET STABILIZER

O

O

OH O

O

O

O

OOH

OHOH

O

OH OH

OO

OH

OHOH

O

O

O

O

O

OH

OH

O

OOH

OH

O

OOH OH

O

O

O

O

O

O

STABILIZER

COMPATIBILIZER

Effect of antioxidant• Stabilization of chain-breaking antioxidants

• Stabilization by preventive (secondary) antioxidants

phosphites, organic sulfides

Effect of heat stabilizerThe processing temperature is about 180-200 °C.

• ROOH + Mn+ ROO. + M(n-1)+ + H+

• ROOH + M(n-1)+ RO. + Mn+ +OH-

• 2ROOH ROO. + RO. + H2O

Much more efficient inhibition is achieved by using metal deactivators, together with the antioxidants.

Mn+/M(n-1)+

Effect of light stabilizerSmall amounts of impurities or chromophores can be sufficient to induce

photooxidaiove degradation even in the absence of appreciable UV absorption by a polymer.

Types:• UV absorbers: absorption of harmful UV radiation and it dissipation that

does not form heat. Need a thickness. Hxdroperoxybenzophenones and hydroxyphenyl benzotriazoles.

• Quenchers of excited states: light stabilizers able to take over energy absorbed by the chromophores present in the plastic and to dispose of it efficiently to prevent degradation.

• Hydroperoxide decomposers: metal complexes of sulfur-containig compounds such as dialkyldithiocarbamates, dialkyldithiophosphates and thiobisphenolates.

• Free radical scavengers: n-butylamine-nickel-2,’2-thio-bi-(4-tert.-octylphenolate) nickel-bis(3,5-di-tert.-butyl-4-hydroxybenzol-phosphonic acid monobutylester). Hindered amine typelight stabilizers: bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate.

Food packaging and use of stabilizersGyörgyi Szarka, Béla Iván

Department of Polymer Chemistry Institute of Materials and Environmental Chemistry 

Research Centre for Natural Sciences, Hungarian Academy of Sciences