Thermal sterilisation

Because flexible films have excellent strength and good electrical and thermal properties, have low permeability to gases, water, oil, odour and could be sterilised so they are used in capacitors, cables, magnetic recording tapes, typewriter ribbons, food packaging, tracing film, book covers, etc. The film is coated with aluminium by vacuum disposition and used for decoration and in textiles. 

M. Lewis and N. Heppell, Continuous Thermal Processing of Foods — Pasteurisation and UHT Sterilisation, Aspen Publishers, New York, 2000. 

Thermal treatment or filter sterilisation is advised when risk of bottle infection is high... 

Like thermal treatment, radiation processing causes some loss of vitamins, but they are only important at sterilisation doses, level which is only used for special applications such as diets for immunologically-incompetent patients. 

The British Pharmacopoeia 1980 included this as a sterilising process for aqueous products where the drug entity exhibits thermal instability but will withstand up to 100 °C for 30 min. The process was subsequently excluded from the BP 1988. 

Thermally stable material such as glassware or metal instruments may be sterilised by heating them in an oven at 185°C for two hours. The material is wrapped in autoclave paper prior to heating, and after removal remains sterile until the wrapping paper is removed. Steam treatment in an autoclave is normally used for the sterilisation of aqueous material. The autoclave uses steam at a pressure greater than atmospheric and laboratory systems normally operate at 15 lbs in which corresponds to a temperature of 121 °C. This makes the assumption that the atmosphere inside the autoclave is composed only of steam and therefore it is necessary to expel all the air before the sterilisation process commences. 

The time taken to sterilise materials depends on the load, but typically loads made up of relatively small volumes would be treated adequately within 20 minutes. Loads containing large volumes take longer and suitable times can be determined by the use of thermal probes or spore strips (see page 86). 

Material which is thermally unstable cannot be sterilised by autoclaving, and solutions should be sterilised by membrane filtration through a membrane with a pore size of less than 0.45 pm. Membrane filtration is dealt with in more detail in the chapter on water testing. It should be noted that membrane filters will only remove bacteria and do not necessarily remove viruses. 

Non-thrombogenic Physico-chemical Thermal Mechanical Biological Application-related properties Easy to manipulate Sterilisable Storable... 

PSU Engineering applications, valve bodies, under honnet components, replacement for stainless steel parts Electrical and electronic components, switch housings Very good thermal stability Medical sterilising trays, radiation resistance parts... 

The mechanical, electrical and thermal properties of polymers are discussed as are other diverse applications such as solvent and detergent resistance, frictional and hardness properties, food packaging applications and gas barrier properties. In addition a very important application is discussed of the resistance of plastics to gamma and other forms of radiation namely their use in nuclear industry, medical applications and food sterilisation. 

Sterilisation in the final container is not possible for suspension-type eye ointments. During heating the ointment base melts and the dispersed powder particles will settle. Active substances intended for use in suspension ointments must be purchased sterile or sterilised by dry heat prior to use if their thermal stability is sufficient. The container with the raw material should only be used for the preparation of eye ointments. 

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