ADVANTAGES OF BIODEGRADABLE POLYMERS

1.        Compost derived in part from biodegradable plastics increases the soil organic content.

2.        The water and nutrients are retained.

3.        The chemical inputs and plant diseases are suppressed.

4.        Biodegradable shopping and waste bags disposed in a landfill can increase the rate of organic waste degradation in landfills.

5.        Methane harvesting potential is also enhanced.

6.        The landfill space usage is decreased. Biodegradable landfill covers can extend landfill life considerably.

7.        Energy required to synthesize and manufacture biodegradable plastics is much lower for most biodegradable plastics than for non-biodegradable plastics.

8.        Biodegradable plastics also offer important environmental benefits through the use of renewable energy resources and reduced greenhouse gas emissions.

MECHANISM OF POLYMER DEGRADATION

Polymer degradation is broadly of two types:

Chain degradation: Here the degradation starts from the chain ends resulting in successive release of monomer units. It is reverse of chain propagation hence can be called de polymerization.

Random degradation: It occurs at any random point along the polymer chain. It is reverse of poly condensation process. Here the polymer degrades to lower molecular weight fragments and practically no monomers are released.

TYPES OF POLYMER DEGRADATION:

Degradation usually involves the chemical modification of polymer by its environment. Degradation of  polymer may be brought about by:

THERMAL DEGRADATION

Traces of transition metals accelerate thermal oxidative process by inducing hydro peroxide decomposition.

MECHANICAL DEGRADATION

Stretching, grinding, milling and any type of polymer shearing process produce free radicals as a result of main chain fracture. Upon warming; these radicals attack the polymer matrix and lead to further scission reaction through radical rearrangement reactions. In the melt, it is difficult to separate the combined degradative effects of torque, time and temperature.

DEGRADATION BY IONIZING RADIATION

The interaction of high energy radiation with polymers generates free radicals and produce defected products. Aliphatic polymers are damaged largely by post irradiation thermal oxidation.

METAL CATALYZED DEGRADATION

Polymers contain metallic compounds, as impurities or deliberately incorporated additives induce both photo and thermal stability problems.

OXIDATIVE DEGRADATION

Oxygen is present in the amorphous domains of all polymers, crystallites of some polymers and in fast quenched polyolefin. The oxidative chain reaction is initiated by any process capable of generating free radicals.

SOLAR DEGRADATION

Photo catalytic decomposition of organic dyes in aqueous solution has been carried out with nano size TiO_2. Solar degradation of aqueous wastes are carried out by out door exposure to sun on rotating plastic disc fitted with TiO₂   coated plastic sheet.

HYDROLYTIC DEGRADATION

Hydrolysis of the polymer backbone requires water and can be considered a bimolecular reaction.

ULTRASONIC WAVE AND HIGH ENERGY RADIATION DEGRADATION

Polymers are subjected to Ultrasonic waves, uv and g radiation during polymer processing to reduce the bacterial contamination. Radiation effects occur at random, throughout a polymer.

PHOTO DEGRADATION

Photo degradation occurs when polymers are exposed to sunlight during their outdoor service. Pigments protect against or sensitize photo degradation.

CHEMICAL DEGRADATION

It occurs by introducing hydrolysable or oxidative functional group into the polymer backbone. The polymer chains become labile to an aqueous environment and thus, chemical degradation initiates polymer erosion.

BIO DEGRADATION

It implies the degradation that is mediated by a biological system. It is a mass loss of monomers, oligomers. Chemical reactions describing biodegradation of a hydrocarbon polymer in aerobic and anaerobic environment can be expressed as:

AEROBIC ENVIRONMENT:

Polymer + O₂      →     CO₂   +    H₂O + Biomass + Residue

ANAEROBIC ENVIRONMENT:

Polymer →     CO₂/CH₄   +    H₂O + Biomass + Residue

BIODEGRADABLE POLYMER TERMINOLOGY

Many polymers that are claimed to be ‘biodegradable’ are in fact ‘bioerodable’, ‘hydrobiodegradable’ or ‘photo-biodegradable’. These different polymer classes all come under the broader category of ‘environmentally degradable polymers’.

Various classes of biodegradable plastics, considered in terms of the degradation mechanism are:

1.         Biodegradable

2.         Compostable

3.         Hydro- biodegradable

4.         Photo- biodegradable

5.         Bioerodable

6.         Degradable  polymers

7.         Degradation

8.         Disintegration

9.         Elimination

10.       Erosion

BIODEGRADABLE

Biodegradation is degradation caused by biological activity, particularly by enzyme action leading to significant changes in the materials chemical structure. In essence, biodegradable plastics should break down cleanly, in a defined time period, to simple molecules found in the environment such as carbon dioxide and water.

COMPOSTABLE

Compostable biodegradable plastics must be demonstrated to biodegrade and disintegrate in a compost system during the composting process (typically around 12 weeks at temperatures over 50°C).

HYDRO-BIODEGRADABLE

Hydro-biodegradable polymers are broken down in a two-step process - an initial hydrolysis followed by further biodegradation.

PHOTO-BIODEGRADABLE

Photo-biodegradable polymers are broken down in a two-step process - an initial photo-degradation stage, followed by further biodegradation.

BIO-ERODABLE

Many polymers are  ‘bioerodable’. They degrade without the action of micro-organisms. This is also known as abiotic disintegration, and include processes such as dissolution in water, ‘oxidative embrittlement’ (heat ageing) or ‘photolytic embrittlement’

DEGRADABLE POLYMERS

A material is called degradable if it undergoes degradation to a specific extent within a given time measured by specific Standard Test methods.

DEGRADATION

It is an irreversible process leading to a significant change of the structure of a material, typically characterized by a loss of properties (e.g. integrity, molecular weight, structure or mechanical strength) and/ or fragmentation.

DISINTEGRATION

Disintegration means the falling apart into very small fragments of packaging or packaging material caused by degradation mechanisms.

ELIMINATION

It is the excretion and metabolism of polymer and erosion product from mammals.

EROSION

It is the mass loss of a polymer matrix which can be due to the loss of monomers, oligomers or even pieces of non degraded polymers. Erosion can be the result of biological, chemical or physical effect.

Dr. Shah G.D., submitted to Modern Plastics & Polymers- Plastics @ Gujarat, for supplement March 2011 edition.

Published as 

Skill development- Fostering new talent  by Kymberlee Fernandes, rewiew interview of Dr. Shah G.D., Modern Plastics & Polymers- Plastics @ Gujarat, supplement March 2011 edition. pp 50-52.

 

JOURNEY OF PLASTIC TECHNOLOGICAL GROWTH FROM GLOBE TO GUJARAT

Dr. Mrs.G.D.Shah (PhD. Chemical Engg.) 
I/C Head Of Plastics Engg. Dept. 
Govt. Polytechnic.

Lord Krishna preferred Gujarat as the place to live in by residing at Dwarika. Since then, Gujarat has been a favoured state to live in and do business. Consequently, with the blessings of Mahatma Gandhi, Sardar Vallbhbhai Patel the Technology and Gujarat has so developed that the Mountain is compelled to come to the Mohamed. No one can bypass the achievements of Gujarat. This is because both the CMs – The Chief Minister and the Common Man -- in Gujarat think for the development of Gujarat. The Chief Minister of Gujarat, H’ble Shri Narendra Modi, having the heart of Common Man of Gujarat has made the Gujarat State the most favoured destination of India for sharing technology and do Global business.

The Plastics Industry in Gujarat has also joined hands to hands with the vibrant drive of development of Gujarat. Gujarat has approximately 15,000 units of which @80% are in small scale sector having annual turnover of @10,000 crores. This happens to be @one fifth of the total industrial units of plastics in India. Gujarat is the second highest exporter of India in Plastic sector. The availability of raw material is the key asset of Gujarat plastic industry. More than 70% of polymers are manufactured in Gujarat which is @ 60% of total output of the Indian Petrochemical Industry. Gujarat plastic industry has achieved annual growth of @15-20% in past years. Looking to the present per capita plastic consumption of 8-10 kg in India as against 25-30 kg in the developed economies and 85-100kg in the highly developed economies, the potential of growth of plastic industry in Gujarat is massive. Today major international companies from various segments of industry like automobile, food processing and packaging have set up their large manufacturing plants in Gujarat. With the growth of per capita income and favourable government support the Gujarat entrepreneurs are motivated to acquire/hire technical expertise, to achieve high quality standards.

The growing market of the technology will increase the requirement of technical expertise in the industry. In order to meet the requirements of industry the intake capacity of Government Polytechnic Ahmedabad is increased to double its original capacity i.e. from 30 to 60 since academic year 2008. The proposal was made well in advance in year 2007. Also the syllabus is revised on regular basis. The Diploma Plastics Engineering is the only Diploma course having tenure of 4 years—8 semesters. It is sandwich pattern course offering two industrial training of 24 weeks each under Apprenticeship act at the 5^th and 8^th semester level. The student placement is almost 100% with a start of 5000/- to 10,000/- per month. The students also get an opportunity to serve abroad in countries like South Africa, Saudi Arabia, Malaysia, Singapore, Australia, U.S., etc. They also can opt for higher studies in India as lateral entry in 2^nd year degree engineering. As the tenure of this Diploma is of 4 years the students can get direct admissions at the Masters courses after obtaining credits of certain courses as may be prescribed by individual Universities/Program in various countries mentioned. Most of the Diploma pass outs find professional opportunities in various fields of plastics industry like servicing/maintenance, marketing, processing, machine manufacturing, testing and quality assurance, mould designing and fabrication field.

To satisfy the industrial needs of constant skill up gradation the department conducts special self sustaining short term programs under continuing education centre. The duration and contents for these programs are designed as per the industrial need.

The Department, through the community Polytechnic wing of the institute also conduct various skill based short term program for the development of rural community through technology transfer. The rural community is imparted skills like fibre reinforced plastics product manufacturing, acrylic fabrication, screen printing technology etc. These skills require low investment and have high market generating self employment.

The Department, through SPPWD Study centre of the institute runs various non formal courses of 3 months duration. These courses are designed to impart technical skill to the physically challenged persons. The duration of the courses is of 3 months. After 3 months the persons with disability acquire technical skill and professional competency related to various miscellaneous plastic processing techniques like fibre reinforced plastics product manufacturing, acrylic fabrication, screen printing technology etc. After completion of the course they are assisted for their employment and/or are motivated for self employment. The students are paid a monthly stipend as per the Government Norms. To satisfy the industrial and social needs the Department has well equipped laboratories and highly qualified, intelligent and dedicated faculty/staff.

ack of Well established and proven plastic recycling line for plastics, and ignorance towards the disposal of plastic waste has become an issue of major concern. This has lead to a worldwide drive for the development of biodegradable plastics. To deal with this and other such issues in future, the Department plans to start a plastics testing cum research centre. The major beneficiaries of the plan are the industries, who strive for the international/national standards, and the young/upcoming researchers, as they can get the research facility under one roof. The Department also observe a continuous recycling line in the department itself.

 

 The development of biodegradable polymer is dealt in my personal capacity by developing a degradable polymer/theory while pursuing the doctorate degree in chemical engineering. Various study and research articles have been published in various national and international journals with a mention of recycling trends, biodegradability and eco friendly use of plastics.

Looking to the growth rate of plastics industry the Department would like to develop a processing, mould fabrication and testing laboratory possessing   modern equipments. Although the Department has a well equipped laboratory, the equipments with modern technology are still missing.