PART 2a

this is an experiment attempting to make a filament out of throwaway plastics. The aim is as always to try to keep it simple. And, as i have been making fibre for a long time from polyethylene, i have chosen to exclude this material. In throwaway 1c I experimented with making string from a polystyrene/methylene chloride solution, by extruding the thick viscous liquid through a pin prick in the tip of a syringe. the resulting filament was fairly brittle, breaking easily. Which lead me to try other plastics. Nylon and PET, are, unlike polystyrene, commonly used in making fibre and filament industrially. As these plastics are not easily dissolved in a solvent, the extrusion process usually involves the plastic in its molten state. The melted plastic is forced through tiny holes in a metal plate - the "spinneret" and simultaneously cooled, stretched and wound.

A draw back when melting plastics are their hygroscopic properties. not all plastics are hygroscopic (absorbing water into their molecular structure) but nylon and PET are. Under normal conditions these plastics absorb moisture from their surroundings and this alters the plastics properties - making it difficult to melt, for example, or prone to discoloration, or causing increased brittleness etc if melted when "wet". Normally if these plastics are being prepared for melting they are dried first, by heating with dehumidified air (for in most instances, several hours) below their melting point. An additional complication in the case of nylon is its tendency to oxidise in hot air - again detrimental to the polymer's properties. The moral of the story so far is you cant just melt hygroscopic polymers. moisture + heat = bad. air + heat = bad. So what to do if i want to melt PET and Nylon? We need upwards of 200 and something degrees C, no air, no moisture. The one thing that sprung to my mind was OIL. Good old everyday cooking oil. Well known to be unfriendly to water and smothering out any air. And HOT. So i put it to the test. These are the initial plastics i sampled - nylon whippersnipper cords (picked up from the footpaths and verges) and PET supplement bottles (thanks Jesika!) and used nylon try-sox courtesy of the shoe shop.

P.S. -an interesting thread on "hygroscopic" - more >

the equipment i have used to heat the oil. A bunsen burner, a tripod with gauze, a beaker, a thermometer, and a gauze platform fitted inside the beaker to prevent the plastic sticking to the bottom and potentially overheating. I am aiming for an oil temperature of about 250C.

the portions of plastic before dropping into the hot oil.

the same portions of plastic after dropping into the hot oil. The whippersnipper cords noticeably sizzle and bubble, but do melt into a soft and pliable material. the stockings melt well too, and without sizzle or bubble. The PET however, shrinks quite noticeably, thickens, but does not soften, unfortunately.

At a later stage i intend to "dry" samples in the oil by holding it at a lower temperature (80C in the case of nylon, 140C for PET, for probably an hour or so (until it stops giving off bubbles?) then raising the temperature of the oil to the plastic's melting point) rather than just dropping the pieces into oil hot enough to melt them. this should give better results...

a piece of red whippersnipper cord and stocking heating in the oil

once the plastic is pliable, it is wrapped around the end of a heatproof rod.

an edge of the soft plastic blob is grasped in a pair of tongs...

and gently pulled upwards out of the oil. hopefully a fine thread will form. I have found that keeping the melted plastic just below the surface of the oil works best. keep pulling, and the thread should continue to lengthen.

at a certain point the length of the thread will become unwieldy. Rolling onto a short length of dowel can make it more managable, and easier to draw the thread at a consistent rate - which will produce a more even thickness of the thread.

an example of some of the thread produced, from the whippernsipper cord.

some more thread. The very fine parts were stretched after the plastic cooled - the plastic maybe doubles or triples in length, along with becoming much thinner. The resulting filaments are very strong.