Plastic additives & Fabrication processes


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Plastic additives : 

Plastic additives Constituents added in to basic resin or compound to improve a polymer’s performance during processing, or tailor a polymer’s performance capabilities for end use. Additives used routinely in thermoplastic formulation are: 1. Plasticizers 6. UV absorbents 2. Lubricants 7. Colourants 3. Stablizers 8. Antistatic agents 4. Fillers 9. Opacifiers 5. Antioxidants

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Plasticizers : T hese are a broad group of chemically and thermally stable materials, ranging from liquids to solids. They are used in plastic compounds to impart flexibility, resilience, reduced brittleness, and softness to various polymers, at the same time, they may facilitate the process. Plasticizers may be liquid monomers, viscous polyesters and epoxides , or solid rubbery polymers. eg . Dioxtyl phthalate, and low mol. wt. polyesters. Lubricants : These are used to assist processing of plastic during the molding or extrusion operations. These can be classified into two types: Internal lubricants : These must be compatible with the polymer. Their action is to reduce internal cohesive forces allowing the molecule greater mobility. This results in lower melt viscosity, increased flow, and reduced energy requirement for processing. eg . Polydimethyl siloxane , stearamides .

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External lubricants : They must be relatively incompatible with the polymer as they must migrate to the surface during hot processing to reduce friction b/w the polymer and hot metal surface. eg . Fatty acid esters, fatty acid amides, liquid paraffin. Lubricants may also be used as dispersing agents, plasticizers, or slip agents depending on their chemical nature. These are usually included up to 1% level.

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Stabilizers : During the manufacturing process heat, pressure and shear energy can cause degradation of the polymer. Addition of heat stabilizer will reduce these undesirable reactions. Stabilizers are also used to retard or to prevent the deterioration of plastic materials resulting from exposure to light, and to improve their aging characteristics. eg . Organometallic compounds, fatty acid salts, inorganic oxides. Fillers : A filler is an inert solid substance. It may reduce degradation of plastic or be used simply to reduce cost. The maximum limit of fillers is around 1:1. Addition of fillers to base polymer may result in reduced flexibility and chemical resistance, improved heat stability. eg . Carbon black, wood flour, glass fibres etc.

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Antioxidants : . Antioxidants: Many plastic materials are susceptible to oxidative degradation and require antioxidants to slow down the process and to give them a longer shelf life. Polymers are often exposed to heat, light, ozone, and mechanical stress, in the presence of oxygen during fabrication process. The resulting oxidative effect will cause the formation of free radicals, which contribute, in turn, to the degradation of the polymer. Antioxidants are used at 0.01- 0.4% level. Antioxidants are of two types: Primary antioxidants: They interrupt oxidative degradation of plastics by tying up the free radicals. eg . Butylated hydroxytoluene (BHT) Secondary antioxidants: They decompose the unstable hydroperoxides formed in plastic degradation process to inert products. eg . Thioester and phosphites

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UV Absorbers : To protect plastic from UV degradation To prevent product degradation Usually added at 0.1-0.2% level. Eg . Hydroxybenzophenones , compounds of oxalic anilide . Colorants: These are used to impart color. Both dye and pigment are used for this purpose. Dye molecule have a tendency to bleed out of the polymer matrix upon aging, but pigments have been shown to be non bleeding. Ultramarine blue is commonly used colorant for parenterals .

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Antistatic agents : prevent buildup of static charges on the metal surface. They are normally incorporated at 0.01-0.2% level eg . surfactants. Opacifiers : eg . Titanium dioxide (1-3%).

There are many processes used to convert plastic resin from pellets into desired shapes or configurations. All plastic processes are similar in the use of three basic elements to convert the resin from a pellet to its processed shape. Heat: Excites molecular structure to allow free movement of molecules. Pressure: To form the free flowing polymer into a desired shape. Time: Required to allow for transfer of heat into the plastic followed by time for removal of heat(cooling). Fabrication process for plastics


EXTRUSION PROCESS Compression process in which material is forced to flow through a die orifice to provide long continuous product whose cross‑sectional shape is determined by the shape of the orifice. Widely used for thermoplastics and elastomers to mass produce items such as tubing, pipes, hose, structural shapes, sheet and film, continuous filaments, and coated electrical wire. Carried out as a continuous process; extrudate is then cut into desired lengths.

Components and features of a (single‑screw) extruder for plastics and elastomers: 

Components and features of a ( single‑screw ) extruder for plastics and elastomers

Extruder Screw: 

Extruder Screw Divided into sections to serve several functions: Feed section - feedstock is moved from hopper and preheated Compression section - polymer is transformed into fluid, air mixed with pellets is extracted from melt, and material is compressed Metering section - melt is homogenized and sufficient pressure developed to pump it through die opening

Die End of Extruder: 

Die End of Extruder Progress of polymer melt through barrel leads ultimately to the die zone Before reaching die, the melt passes through a screen pack - series of wire meshes supported by a stiff plate containing small axial holes Functions of screen pack: Filter out contaminants and hard lumps. Build pressure in metering section. Straighten flow of polymer melt and remove its "memory" of circular motion from screw.

Injection Molding: 

Injection Molding Polymer is heated to a highly plastic state and forced to flow under high pressure into a mold cavity where it solidifies and the molding is then removed from cavity. Typical cycle time  10 to 30 sec, but cycles of one minute or more are also common. Mold may contain multiple cavities, so multiple moldings are produced each cycle.

Injection Molding Machine : 

Injection Molding Machine

Reaction Injection Molding: 

Reaction Injection Molding RIM is a relatively new process where the plastic is obtained by a reaction prior to the final injection process eg . Reaction between polyol and isocyanate . COMPRESSION MOLDING

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Mold is heated and molten materials are held under pressure until hardening is completed. Gases and water vapours are released so mold has to be vented. Excess powder is added for complete filling. DIP MOULDING Solid shape is dipped into a mobile liquid. When the material has set the formed shape is stipped from the mould.

Sheet and Film Production Processes: 

Sheet and Film Production Processes Processes include: Slit‑Die Extrusion of Sheet and Film:- Production of sheet and film by conventional extrusion, using a narrow slit as the die opening. Slit may be upto 3m wide and 0.4mm narrow. Blown‑Film Extrusion Process:- Extrusion of tube. Tube is drawn upward while still molten and simultaneously expanded by air inflated into it through die.

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Calendering :- Molten plastic is passed through a series of highly polished (heated) rollers followed by a cooling roller nip. Blow Molding Molding process in which air pressure is used to inflate soft plastic into a mold cavity. Important for making one‑piece hollow plastic parts with thin walls, such as bottles.

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Accomplished in two steps: Fabrication of a starting tube, called a parison Inflation of the tube to desired final shape Forming the parison is accomplished by either Extrusion or Injection molding

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Extrusion blow molding : (1) extrusion of parison ; (2) parison is pinched at the top and sealed at the bottom around a metal blow pin as the two halves of the mold come together; (3) the tube is inflated so that it takes the shape of the mold cavity; and (4) mold is opened to remove the solidified part.

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Injection blow molding : (1) parison is injected molded around a blowing rod; (2) injection mold is opened and parison is transferred to a blow mold; (3) soft polymer is inflated to conform to the blow mold; and (4) blow mold is opened and blown product is removed.


Thermoforming Flat thermoplastic sheet or film is heated and deformed into desired shape using a mold. Vacuum thermoforming: (1) a flat plastic sheet is softened by heating Vacuum thermoforming: (2) the softened sheet is placed over a concave mold cavity

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(3 ) a vacuum draws the sheet into the cavity (4) plastic hardens on contact with the cold mold surface, and the part is removed and subsequently trimmed from the web.

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Plastic containers for parenteral preparations are manufactured generally by using one or more of following polymers:- Polyethylene Polypropylene PVC Only virgin plastic material is used in the manufacture of containers for parenterals . Additives such as antioxidants , lubricants, plasticizers, stabilizers etc. may be used but no pigments, antistatic agents and mould releasing agents should be used. The container chosen for any particular product should be such that the ingredients of the product in contact with the plastic material are not significantly adsorbed on its surface and do not significantly migrate into or through the plastic.

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The containers may be bags or bottles. They have site suitable for the attachment of an infusion set designed to ensure a secure connection. They have a site that allows an injection to be made at the time of use. They usually have a part that allows them to be suspended and which will withstand the tension occurring during use.

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The integrity of neck and shoulders of containers should be suitably and appropriately strengthened and LVP manufacturer should ensure that the containers withstand the stress conditions and rigors of transportation and packaging. The containers must withstand the sterilization conditions to which they will be submitted. The design of container and method of sterilization are chosen such that all parts of container that will be in contact with infusion are sterilized. The containers must be impermeable to microorganisms after closure. The containers should be such that after filling they are resistant to damage from accidental freezing.

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The containers should remain sufficiently transparent to allow the appearance of content to be examined at any time, unless otherwise justified and authorized.

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There should be proper labeling


POTENTIAL PROBLEMS SORPTION: Loss of product components to plastic. The bonding of solute to plastic is physiochemical phenomenon related to the properties of plastic and chemical structure of drug or other soluble components of preparation. Interactions of this type can be determined by measuring the loss of solute to plastic at equilibrium under constant temperature condition. DESORPTION: Loss of plastic component to product. Its rate and extent is affected by solvent system, ph, temperature conditions during processing and storage.

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PERMEATION: of moisture, gasses and light. Excessive permeation can cause chemical and physical deterioration of the product. In liquid preparation, containing organic solvents, drug concentration changes can occur through loss of solvent to atmosphere. PHOTODEGRADATION: Drug loss due to radiations. To obtain clear, colourless containers, organic UV absorbers can be used such as: O- hydrobenzophenone 2-hydroxyphenylbenzotriazoles Aspects such as convenience, appearance, while important, should not replace safety and efficacy .

Quality control Tests for plastic parenteral containers: 

Quality control Tests for plastic parenteral containers Leakage test:- Fill ten containers with water, fit with the intended closures and keep them inverted at room temperature for 24hours. There should be no signs of leakage from any container. Solution S:- Fill a container to its nominal capacity with water and close it, if possible using the usual means of closure, otherwise close using a sheet of pure aluminium . Heat in an autoclave so that a temperature of 121± 2º is reached within 20 to 30 minutes and maintain at this temperature for 30 minutes. If heating at 121º leads to deterioration of the container, heat at 100º for 2 hours. Use solution S within 4 hours of preparation.

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Blank:- Prepare a blank by heating water in a borosilicate glass flask closed by a sheet of pure aluminium at the temperature and for the time used for the preparation of solution S. Clarity and colour of solution S:- Solution S is checked for clarity and colourlessness . Acidity or alkalinity:- To a volume of solution S corresponding to 4 per cent of the nominal capacity of the container add 0.1ml of phenolphthalein solution. The solution is colourless . Add 0.4 ml of 0.01M sodium hydroxide. The solution is pink. Add 0.8 ml of 0.01M hydrochloric acid and 0.1 ml of methyl red solution. The solution is orange-red or red. Light absorption:- The light absorption in the range 230 nm to 360 nm of solution S using blank should not be more than 0.20.

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Reducing substances:- To 20.0 ml of solution S add 1 ml of dilute sulphuric acid and 20.0 ml of 0.002M potassium permanganate. Boil for 3 minutes. Cool immediately. Add 1 g of potassium iodide and titrate immediately with 0.01M sodium thiosulphate , using 0.25 ml of starch solution as indicator . Carry out a titration using 20.0 ml of the blank. The difference between the titration volumes should not be more than 1.5 ml. Labelling :- The label accompanying a batch of empty containers states : (1) the name and address of the manufacturer; (2) a batch number which enables tracing the history of the container and of the plastic material of which it is manufactured.


CONTAINERS FOR BLOOD AND BLOOD COMPONENTS Plastic containers for collection, storage, processing and administration of blood and its components are supplied sterile. The container may contain anticoagulant solution depending on their intended use. Each container is fitted with attachments suitable for intended use. The outlets are of shape and size allowing for adequate connection with blood giving equipment.

The protective coverings on the blood taking needles and appendages are designed to ensure that sterility is maintained, should be easily removable and tamper proof. Plastic syringes and needles supplied sterile are contained in packs that preserve their sterility. The batch number is clearly marked on the pack. Should not be reused.

The container should be sufficiently transparent to allow adequate visual examination of its contents before and after the taking of the blood and sufficiently flexible to offer minimum resistance during filling and emptying under normal conditions of use. The container should contain not more than 5 ml of air.

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