1. Introduction
In developing countries, environmental pollution by synthetic polymers has assumed dangerous proportions. Petroleum-derived plastics are not readily biodegradable and because of their resistance to microbial degradation, they accumulate in the environment. In addition in recent times oil prices have increased markedly. These facts have helped to stimulate interest in biodegradable polymers. Biodegradable plastics and polymers were first introduced in 1980s. Polymers from renewable resources have attracted an increasing amount of attention over the last two decades, predominantly due to two major reasons: firstly environmental concerns, and secondly the realization that our petroleum resources are finite. There are many sources of biodegradable plastics, from synthetic to natural polymers. Natural polymers are available in large quantities from renewable sources, while synthetic polymers are produced from non-renewable petroleum resources. Biodegradation of polymeric biomaterials involves cleavage of hydrolytically or enzymatically sensitive bonds in the polymer leading to polymer erosion. A vast number of biodegradable polymers have been synthesized recently and some microorganisms and enzymes capable of degrading them have been identified.
Mercopoli is committed to increase, develop and promote the usage of Bio-Polymers to address the over increasing problem of plastic waste in our oceans and lands
2. Natural biodegradable polymers
Biopolymers are polymers formed in nature during the growth cycles of all organisms; hence, they are also referred to as natural polymers. Their synthesis generally involves enzyme-catalyzed, chain growth polymerization reactions of activated monomers, which are typically formed within cells by complex metabolic processes.
3. Our main Biobased polymers:
3.1 Polyhydroxyalkanoates PHAs
Are polyesters produced in nature by numerous microorganisms, including through bacterial fermentation of sugars or lipids. When produced by bacteria they serve as both a source of energy and as a carbon store. More than 150 different monomers can be combined within this family to give materials with extremely different properties. These plastics are biodegradable and are used in the production of bioplastics. They can be either thermoplastic or elastomeric materials, with melting points ranging from 40 to 180 °C. The mechanical properties and biocompatibility of PHA can also be changed by blending, modifying the surface or combining PHA with other polymers, enzymes and inorganic materials, making it possible for a wider range of applications.
Applications:There are potential applications for PHA produced by micro-organisms within the agricultural, medical and pharmaceutical industries, primarily due to their biodegradability.
Fixation and orthopaedic applications have included sutures, suture fasteners, meniscus repair devices, rivets, tacks, staples, screws (including interference screws), bone plates and bone plating systems, surgical mesh, repair patches, slings, cardiovascular patches, orthopedic pins (including bone.lling augmentation material), adhesion barriers, stents, guided tissue repair/regeneration devices, articular cartilage repair devices, nerve guides, tendon repair devices, atrial septal defect repair devices, pericardial patches, bulking and filling agents, vein valves, bone marrow scaffolds, meniscus regeneration devices, ligament and tendon grafts, ocular cell implants, spinal fusion cages, skin substitutes, dural substitutes, bone graft substitutes, bone dowels, wound dressings, and hemostats.
3.2 Polyvinyl alcohol PVOH, PVA, & PVAl
is a water-soluble synthetic polymer. It is used in papermaking, textile warp sizing, as a thickener and emulsion stabilizer in PVAc adhesive formulations and a variety of coatings. It is colourless (white) and odorless. It is commonly supplied as beads or as solutions in water.
Aplications : PVA is used in a variety of medical applications because of its biocompatibility, low tendency for protein adhesion, and low toxicity. Specific uses include cartilage replacements, contact lenses, and eye drops. Polyvinyl alcohol is used as an aid in suspension polymerizations. Its largest application in China is its use as a protective colloid to make polyvinyl acetate dispersions. In Japan its major use is the production of Vinylon fiber. This fiber is also manufactured in North Korea for self-sufficiency reasons, because no oil is required to produce it. Another application is photographic film. Medically, it may also used as the embolic agent in a Uterine Fibroid Embolectomy (UFE)
3.3 Polylactic acid, or polylactide PLA
it is a thermoplastic polyester PLA has become a popular material due to it being economically produced from renewable resources. In 2010, PLA had the second highest consumption volume of any bioplastic of the world, although it is still not a commodity polymer. Its widespread application has been hindered by numerous physical and processing shortcomings. PLA is the most widely used plastic filament material in 3D printing.
The monomer is typically made from fermented plant starch such as from corn, cassava, sugarcane or sugar beet pulp.
Applications: PLA is used as a feedstock material in desktop fused filament fabrication 3D printers. PLA-printed solids can be encased in plaster-like moulding materials, then burned out in a furnace, so that the resulting void can be filled with molten metal. This is known as “lost PLA casting”, a type of investment casting.
PLA can degrade into innocuous lactic acid, so it is used as medical implants in the form of anchors, screws, plates, pins, rods, and as a mesh. Depending on the exact type used, it breaks down inside the body within 6 months to 2 years. This gradual degradation is desirable for a support structure, because it gradually transfers the load to the body (e.g. the bone) as that area heals. The strength characteristics of PLA and PLLA implants are well documented.
PLA can also be used as a decomposable packaging material, either cast, injection-molded, or spun. Cups and bags have been made from this material. In the form of a film, it shrinks upon heating, allowing it to be used in shrink tunnels. It is useful for producing loose-fill packaging, compost bags, food packaging, and disposable tableware. In the form of fibers and nonwoven fabrics, PLA also has many potential uses, for example as upholstery, disposable garments, awnings, feminine hygiene products, and diapers. Thanks to its bio-compatibility and biodegradability, PLA has also found ample interest as a polymeric scaffold for drug delivery purposes.
3.4 Polybutylene succinate PBS
it is a thermoplastic polymer resin of the polyester family. PBS is a biodegradable aliphatic polyester with properties that are comparable to polypropylene.
Applications: As PBS decomposes naturally into water and CO2, it may be a biodegradable alternative to some common plastics. The scope of PBS application fields is still growing and several areas can be identified but it remains difficult to know precisely in which specific object PBS is actually used. First in the packaging field, PBS could be processed into films, bags, or boxes, for both food and cosmetic packagings. Other applications of PBS could be found as disposable products such as tableware or medical articles. In agriculture, PBS finds interest in the fabrication of mulching films or delayed release materials for pesticide and fertilizer. PBS is also promise to find market shares in fishery (for fishing nets), forestery, civil engineering or other fields in which recovery and recycling of materials after use is problematic. In the medical field, PBS could be used as biodegradable drug encapsulation systems, and is also investigated for implants.