Plastics

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Infobox on Plastics
Example of Plastics
Plastics.jpg
Facts
Origin -
Stowage factor (in m3/t) -
Humidity / moisture -
Ventilation -
Risk factors See text

Description / Application / Shipment and storage / Risk factors

Plastic materials which become contaminated with dust, dirt, etc., may, if such foreign matter cannot be separated, become useless for the production of high-grade articles. When this material is in dried form, moulding powders, etc., and is packed in paper bags, it is particularly liable to depreciation by reason of the bags coming into contact with foreign substances. Care is necessary in handling damaged bags to avoid contamination of the unexposed portion of the contents. The following are individual comments on various plastic materials for guidance in assessing the cause and extent of damage, and in the handling and treatment of plastic materials:

The effect of damage by:
1 a) High humidity
b) Salt water
c) Fresh water
d) Treatment, if any

2 a) Effect of damage by heat
b) Treatment, if any

Acetal Polymers
1.   (a), (b) and (c): All three causes render material unsuitable for use.
      (d) Vacuum drying would make material suitable for processing in case of (a) and (c) but not (b).
2.    Melts at 165°C. Has a high thermal stability in air up to 100°C; will begin to degrade at approx. 190°C.

Acrylic Moulding Material
1.   (a) and (c) Adversely affects processing and the general appearance of moulding.
      (b) As for (a) but with additonal deterioration of electrical properties.
      (d) Drying rectifies damage due to (a) and (c) but not that caused by (b).
2.   (a) The product is not damaged by temperatures lower than 80°C

Acrylic Sheet
1.   (a) No effect on the product, but the protective paper is subject to mould growth.
      (b) and (c) Very little effect on the product itself, but water removes the protective paper coating and this leads to damage of the surface of the sheets.
2.   (a) Temperatures above 50°C are liable to damage the surface protection and may also cause the sheets to warp. Damp storage conditions should be avoided.

Acrylonitrile Butadiene Styrene (ABS) Moulding Materials
1.   (a), (b) and (c) Adversely affects moulding characteristics.
      (d) By using a vacuum drying oven at 70°C material damaged by (a) and (c) may be made good for processing but not for (b).
2.   (a) Material begins to soften at about 90°C and as temperature rises the granules will coalesce in the bags. Providing the material does not char (at approx. 160°C) it may be       reground and used as scrap.

Acrylontrile Butadiene Styrene (AMS) Sheet
ABS sheet is not affected by water.
ABS sheet must not be subjected to loads at temperatures above 60°C as permanent deformation may occur.

Alkyd Moulding Resins
1.   (a) Materials cannot be moulded satisfactorily. Electrical and mechanical properties seriously impaired or reduced to unacceptable levels.
      (b) Material is irrecoverably damaged.
      (c) Material cannot be moulded satisfactorily. Electrical and mechanical properties reduced to unacceptable levels. Powder forms aggregates.
      (d) It is sometimes possible to recover part of the value of the material damaged under conditions (a) and (c) by reprocessing on the original manufacturing plant.
2.   (a) Material hardens and is irrecoverably damaged. The material should be stored in a cool place below deck.

Cellulose Acetate, Cellulose Acetate Butyrate and Celulose Proprionate Moulding Material
1.    (a) Would need to be pre-dried before moulding.
       (b) Becomes useless as a moulding compound.
       (c) Depends on the degree of saturation. If slight, pre-drying prior to moulding might make it serviceable. Immersion in water for any length of time would make it useless as a
            moulding compound.
       (d) (a) Drying. (b) None – doubtful whether there is any scrap value. (c) Drying or reprocessing.

Great care is taken in the manufacture of Cellulose Acetate and Cellulose Acetate Butyrate to avoid any kind of contamination from dust or moisture and any damage to the containers used for carrying the material could render it unsuitable for processing.

2.   (a) Softens at about 50-90°C according to type. Would decompose around 240°C

Cellulose Acetate Sheet, Rod, Tube, Film, Foil, Profile Shapes
1.   (a) Temporary effect: If 35% RH rising to 95% RH expansion of plastics 0,5% linear occurs; if properly packed no permanent distortion should result.
      (b) and (c). If immersed for longer than a few minutes warping would ensue later and on drying out.
      (d) Sea-water contamination would need washing off with clean water. Warped sheets could be flattened in presses. Film and badly warped shaped articles could be re-worked only as            scrap.
2.   (a) Heat up to 50°C, if not prolonged, and if articles properly packed, would not cause appreciable damage. If articles come under pressure from packing they may have surface                   markings impressed, or become distorted.
      (b) Sheets can be repolished at the manufacturers’ factory.

Exposed surfaces of some types of cellulose acetate plastics may develop mould on prolonged exposure to high humidity in warm climate. Stowage should be in a cool, dry place. Has very little surface static electrical effect. Although the surface hardness is not very high it is nevertheless quite man-resistant in service. When Cellulose Acetate and Cellulose Acetate Butyrate are brought into intimate contact with other plastics there is some danger of plasticizer migration which may have undesirable effects.

Celluloid Sheet, Rod, Tube, Film, Foil, Profile Shapes
1.    (a) Little effect
       (b) and (c) Damage to surface finish
       (d) Drying and reprocessing
2.    (a) Is highly flammable.

Because of its flammability, this material must be kept away from excessive heat and naked lights. Under standard conditions it will not fume off below 150°C. It has no flash point at all. Requires special stowage, preferably between deck, away from boilers.

NYLON Moulding Material
Polyamides will absorb or release water, rending to estasblish equilibrium with the surrounding atmosphere to a degree governed by the temperature and moisture content of the surroundings. Consequently, care should be taken to ensure there is no damage to their packages which are either hermetically sealed, aluminium foil lined, bags or tins.

1.   (a), (b) and (c) All three causes render the material unsuitable for use.
      (d) Vacuum drying would rectify damage caused by (a) and (c) but not that caused by (b)
2.   (a) The product is not damaged by temperatures below 80°C.

Polycarbonate Mouldings Materials.
1.   (a), (b) and (c) All three causes render the material unsuitable for use.
      (d) Damage by (b) renders the material unusable. For (a) and (c) vacuum drying will restore the material to a usable condition without any effect on the physical properties.
2.   (a) Has a high thermal stability, starting to soften at 145°C and becomes a melt at 220°C. Will decompose above 320°C.
      (b) No damage up to 145°C, but if it melts into a solid mass at temperatures above this, it then has only scrap value.

Polyethylene Moulding Materials
1.   (a), (b) and (c) All three causes render the material unsuitable for processing.
      (d) Vacuum drying in the case of (a) and (c) will enable the material to be used satisfactorily, but not for(b).
2.   (a) The material consolidates above 50°C and melts at 110°C.
      (b) Provided no degradation has taken place, polyethylene that has melted into lumps may be reground for scraps.

Polythene Film
1.   (a), (b) and (c) No effect.
2.   (a) Softening, distortion and finally melting at 115°C. In roll form layers of polythene film will weld together at temperatures somewhat below this.
      (b) Should be stored in a cool place away from heat.

Polythene Sheet
1.   (a), (b) and (c) No effect
      (d) Material can be washed and dried. Drying should take place at moderate temperature, say not above 60°C
2.   (a) Material melts. This material is inert and very free of inherent vice, but should be kept away from heat.

Polypropylene Moulding Compounds (PP)
1.   (a), (b) and (c) All three causes render the material unsuitable for processing.
      (d) Vacuum drying will overcome (a) and (c) but not (b).
2.   (a) Melts at 160°C. It should be all right provided material has not degraded or coalesced.

Polypropylene Film
1.    (a), (b) and (c) Material is unaffected by all three, but as a lot of this material is used in the packaging of foods, any damage or contamination, however slight, will be sufficient for it to         be rejected for such applications.

Polystyrene Moulding Material (PS)
1.   (a), (b) and (c) All three causes render the material uisuitable for processing.
      (d) Problems from (a) and (c) are eliminated by vacuum drying but not for (b).
2.   (a) Material softens, granules coalesce and finally may char and burn.
      (b) Material which has coalesced can be reground, provided no charring or discolouring has occurred, but has only scrap value.

Polystyrene has a surface static electrical effect which attracts dirt, and therefore contaminates very easily from air, especially if the packages are broached or broken. Should be stowed underdeck away from heat.

Polystyrene Sheet
1.   (a) Little or no action.
      (b) and (c) There may be a tendency to slight swelling of surface, with possible distortion.
2.   (a) Thermal distortion – local overheating may result in carbonisation.
      (b) Slightly distorted sheets could be restraightened by heat and pressure.

Contact with other plasticised thermoplastic sheet, e.g. cellulose acetate, should be avoided, due to tendency of plasticiser migration. The material should be stored in a cool place, away from direct sunlight, as certain modified polystyrene sheets are liable to impairment of physical properties as a result of contact with sunlight. Wrapping in moisture-proof, e.g. polythene, envelopes would avoid possible moisture damage.

Polystyrene – Expandable Bead (EPS)
1.   (a), (b) and (c) Providing the wetting is not excessive it has very little effect and will not be detrimental to any processing.
      (d) Do not dry as this will cause expansion of the beads. As they are often processed in a moist condition, no remidial steps need to be taken.
2.   (a) As the polystyrene beads contain a blowing agent, care should be taken to ensure that the material is kept under cool conditions. The beads will soften and expand at temperatures       above 90°C.
      (b) The material is not recoverable once the beads are blown.

Polytetrafluorethylene
1.   (a), (b) and (c) As PTFE is used in powder form, presence of moisture will cause the material to cake.
      (d) Due to the very high technical specification of the material, it is unlikely that wet damaged material would be accepted.
2.   (a) Melting point is 327°C. Will withstand high temperatures without damage.

PVC Moulding and Extrusion Material
1.   (a) and (c) Humidity adversely affects the processing of the product.
      (b) As for (a) but with additional deterioration of electrical characteristics.
      (d) Drying at 50-80°C would largely overcome the effect of high humidity and fresh water, but would not get rid of the contamination resulting from contact with salt water.
2.   (a) Above 50°C the material consolidates.
      (b) Further treatment will not rectify damage caused by excessive heat.

PVC Thick Sheet (Polyvinyl Chloride)
1.   (a) Unlikely to have any effect.
      (b) and (c) Very little effect on coloured materials, but haziness or opacity may be caused in clear sheeting with slight dimensional alterations in both coloured and plain sheeting.
      (d) Prolonged air drying can be used provided too much heat is avoided. Re-processing would not be economic and is unlikely to be satisfactory due to loss of plasticisers and           deterioration caused by further treatment. Discolouration would also probably be experienced.
2.   (a) Loss of embossing, dimensional change and adhesion of sheets. Under normal conditions this material is stable and should not suffer from any inherent vice. Should be stowed in a           cool place.

Coated PVC Sheet
1.   (a) Mildew damage
      (b) Tendering of cloth, i.e. cloth base, is subsequently weakened.
      (c) Nil
2.   (a) Loss of surface texture and finish.

Mould growth and sweating is possible under tropical conditions. Should be stored in a cool place.

PVC Emulsions and Dispersions
1.   (a), (b) and (c) Contamination by (a), (b) and (c) will render the material unusable.
      (d) No recovery possible.
2.   (a) Emulsions: Precipitation and total loss. Solutions: Would probably explode.
      (b) If heat exceeds 80-90°C contents will probably be a total loss.

Emulsions are liable to damage by freezing, and while they should not be exposed to extreme heat, require frost-proof storage. Solutions, due to their inflammability, should be stowed on deck.

Polyvinyl Acetate (PVA) Adhesives
1.   (a) No effect
      (b) and (c) Separation of constituents, breakdown of emulsion.
2.   (a) No serious effect, unless temperature very high.

Should be stored in a warm place. If allowed to freeze the emulsion is liable to break down, with consequent lumping and loss of adhesive properties.

Thermoset Moulding Material (Urea Formaldehyde, Phenol Formaldehyde, Melamine Formaldehyde)
1.   (a), (b) and (c) All three causes can seriously damage. Thermoset moulding material if the package protection fails.
      (d) None. Attempts to dry out powder which has been damaged by humidity, salt water or fresh water are likely to result in other defects.
2.   (a) High temperatures tend to make the powder difficult to mould by stiffening its flow. In extreme cases it can render the powder useless.

This material requires cool stowage, below water line.

Liquid Resins (Urea Formaldehyde, Phenol Formaldehyde, Resorcinol Formaldehyde)
1.   (a) No effect.
      (b) Poor performance due to dilution, ‘shorting’ under high frequency heating.
      (c) Poor performance due to dilution.
2.   (a) Progressive thickening of the liquid and even gelation if too long or too severe. Generally shortens the storage life.

Should be stored away from heat, and preferably under deck.

Surface Coating Resins
1.   (a) Material in sealed containers not affected. In bags no permanent damage.
      (b) No effect on material in sealed containers. In bags, reclamation may be possible.
      (c) Sealed containers should protect material. In bags, it should be possible to reclaim.
      (d) Resins in bags may possibly be dried, but complete removal of salt is not easy.
2.   (a) The resin would probably be rendered unsuitable.

Resins in general are heat-reactive and must be kept away from heat. Being compounded of oils, natural resins, etc., they are to some extent flammable and should accordingly be stowed in a cool place.

Catalyst Hardeners and Fillers in Powder Form
1.   (a) Caking
      (b) Caking. ‘Shorting’ if glue is to be used under high frequency heating. Possible destruction of actice ingredients in specific cases. Effective proportions lowered by dilution.
      (c) Caking. Effective proportions lowered by dilution. Possible destruction of active ingredients in specific cases.
      (d) Drying may be effective in the case of (a) and (c). This should be done by good air circulation, not by high temperature.
2.   (a) Possible destruction of active ingredients in specific cases.

Should be stored away from heat, not on open deck.

With most resin and plastic emulsions freezing causes breakdown, which may take the form of partial or complete coagulation. Generally speaking, the coagulation results in precipitation of ropy masses of resin and plasticiser which rapidly settle to the bottom, but there may remain in suspension a significant amount of dispersed coagulum which would mar seriously the properties of paints or adhesives in which the emulsion might subsequently be used. This dispersed coagulum could be removed by filtration through a 60-100 mesh screen. Generally speaking, the coagulation starts from the walls of the container and works inwards with the progressive drop in temperature or repetition of the freeze/thaw process. Some emulsions are more sensitive to freezing than others; for example, all the polystyrene emulsions, because of their fine particle size and low colloidal protection, tend to be unstable to freeze/thaw conditions and will generally break down on a single freezing. Polyvinyl acetate emulsions vary considerably in their freeze/thaw stability. The large particle type is much more stable than the fine and will stand repeated freezing and thawing without showing any coagulation. The same emulsion plasticised with dibutyl phthalate is rather more sensitive, but even so will withstand several cycles of freezing and thawing without coagulation.

Although by no means universally true, it is often the case that the thicker looking emulsions have the greater storage stability under cold conditions. This is because large particle size is usually associated with high viscosity and stability is enhanced by increase in particle size. The nature of the protective colloid, too, is critical, and some colloids, such for example as polyvinyl alcohol, are more effective than others which include the ethylene oxide alcohol derivatives.

If the emulsifying content is inadequate or unsuitable, or in the unlikely event of the water in the emulsion having too high a salt content, the emulsion may break up so that solidification occurs in the form of lumps at the bottom of the drums. Some emulsions are prepared to withstand long period of storage; others, owing to such inherent susceptibilities, may commence to break up within comparatively short periods. See also Expandable polymeric beads