1. DEFNYDDIAU MATERIALS
Ar gyfer unrhyw swyddogaeth peirianneg mae’n bwysig fod y defnydd yn addas ar gyfer y swydd.
For any engineering application it’s important that the material is suitable for the job.

2. METELAU / METALS DEIAGRAM DOSBARTHIAD METELAU
METALS CLASSIFICATION DIAGRAM
METELAU / METALS
METELAU FFERUS /
FERROUS METALS
METELAU ANFFERUS /
NON FERROUS METALS
DUR /
STEEL
HAEARN /
IRON
DUR CARBON /
CARBON STEEL
DUR CARBON UCHEL /
HIGH CARBON STEEL
DUR CARBON CANOLIG /
MEDIUM CARBON STEEL
DUR CARBON ISEL /
LOW CARBON STEEL
ALIWMINIWM /
ALUMINIUM
COPR /
COPPER
SINC /
ZINC
DUR ALOI/
ALLOY STEEL
ALOI ANFFERUS/
NONFERROUSALLOYS

3. METALAU FFERUS – cynnwys Haearn / FERROUS METALS – contain Iron
Er mwyn galw metel yn DUR rhaid i’r carbon fod o dan 1.8%, dros hyn mae’r metel yn galed iawn ond yn frau – esiampl Dur Bwrw Llwyd efo cynnwys carbon rhwng 3.2% a 3.5%. Mae’r diagram ar y dudalen nesaf yn dangos yr effaith mae carbon yn cael ar fetel.
To call a metal steel it must have less than 1.8% carbon, over this and it’s very hard but brittle, example – grey cast irons has a carbon content of between 3.2% and 3.5 %. The diagram on the following page shows the effect of carbon on metals.
ENW / NAME
CARBON %
DEFNYDD / APPLICATION
DUR MEDDAL MARW
DEAD MILD STEEL
DUR RHATAF AR UN A DDEFNYDDI’R FWYAF
CHEAPEST STEEL BUT MOST WIDELY USED
LOW CARBON ISEL
PANELI CEIR, WEIREN A TIWBIAU
CAR BODY PANELS WIRE + TUBE
DUR MEDDAL
MILD STEEL
GWAITH CYFFREDINOL GWEITHDY
GENERAL PURPOSE WORKSHOP
DUR MEDDAL CANOLIG
MEDIUM CARBON STEEL
CRYFACH, MWY GWYDN A CALETACH OND MWY COSTUS NA DUR CARBON ISEL
HARDER, TOUGHER AND STRONGER BUT MORE COSTLY THAN LOW CARBON STEEL
SIAFTIAU CRANC, GOFANNU, ECHELAU
CRANKSHAFTS, FORGINGS, AXLES
PENNAU MORTHWYL, CYNION OER
HAMMER HEADS COLD CHISELS
DUR CARBON UCHEL
HIGH CARBON STEEL
CRYFACH, MWY GWYDN A CALETACH OND MWY COSTUS NA DUR CARBON CANOLIG
HARDER, TOUGHER AND STRONGER BUT MORE COSTLY THAN MEDIUM CARBON STEEL
0.8 – 1.0
SPRINGIAU COIL , CYNION COED
COIL SPRINGS, WOOD CHISELS
1.0 – 1.2
FFEILIAU, DRILIAU, TAPIAU / DEIAU
FILES, DRILLS, TAPS / DIES
1.2 – 1.4
ARFAU YMYLON MÂN – CYLLILL
FINE EDGED TOOLS - KNIVES
HAEARN BWRW LLWYD
GREY CAST IRON
DEFNYDD CALED IAWN – OND RHY FRAU AR GYFER ARFAU
VERY HARD MATERIAL – TOO BRITTLE FOR MAKING INTO TOOLS
3.2 – 3.5
CASTIAU PEIRIANNAU
MACHINE CASTINGS

5. Dalen + Plât / Sheet + Plate
Castinau / Castings
Rhannau / Sections
Bariau / Bars
Gofaniadau / Forgings
Tiwbiau / Tube
Dalen + Plât / Sheet + Plate
Weiren / Wire
Torch / Coil
Ffurfiau Cyflenwi Metalau / Forms of Supplying Metals

6. COSTAU METALAU METAL COSTS Metal costs depend on a number of factors:
Purity of the grade, Alloying elements, Demand around the world, local economy,
Also the daily price of steel on the trading market
The table below gives a guide on the trading stock metal prices (2009)
Mae cost metel yn dibynnu ar nifer o bethau:
Pa mor bur ydi’r gradd, Elfennau aloi, Faint sydd ei angen ar draws y byd, Economi lleol,
Hefyd pris dyddiol metel ar y farchnad stoc
Tabl isod yn rhoi syniad prisiau metel ar y farchnad stoc (2009)
DEFNYDD
Material
DWYSEDD Density
Cost/tonne
Cost /m3
kg/m3
£/tonne
£/m3
DUR Carbon Steel
7820
550
4301
DUR Alloy Steels
830
6490,6
HAEARN BWRW Cast Iron
7225
5996,75
DUR GWTHSTAEN Stainless Steel
7780
4450
34 621
ALOI ALIWMINIWM Aluminium/alloys
2700
2220
5994
ALOI COPR Copper /Alloys
8900
5550
49 395
ALOI ZINC Zinc alloys
7100
15 762
ALOI MAGNESIWM Magnesium /alloys
1800
4000
7200
ALOI Titanium /alloys
4500
17 000
76 500
ALOI NICEL Nickel alloys
18 000

7. 070M20 SYSTEM CÔD METALAU METAL CODING SYSTEM BS 970-1:1996
Pwrpas ‘British Standard’ 970 ydi gwneud yn siwr for pawb sy’n cynhyrchu metel yn defnyddio yr un system er mwyn “enwi” graddau o fetelau gwahanol -
Mae esboniad o’r system rhifo isod – ac esiamplau o fetelau poblogaidd ar y dair sleid nesaf
METAL CODING SYSTEM
The purpose of the British standard 970 Coding system is to ensure every metal manufacturer uses the same codes for “naming” all grades of steel –
An explanation of the standard and the coding system in given below – examples of popular meatals used are on the following three slides
BS 970-1:1996
Specification for wrought steels for mechanical and allied engineering purposes. General inspection and testing procedures and specific requirements for carbon, carbon manganese, alloy and stainless steels
BS970 Numbering system explained
The BS970 code number is constructed as follows;
a) The first three symbols are a number code indicating the type of steel:
000 to 199 Carbon and carbon-manganese steels. The number represents the manganese content x 100
200 to 240 Free cutting steels. The second and third number indicate the sulphur content x 100
250 Silicon Manganese valve steels
300 to 499 Stainless and heat resisting steels
500 to 999 Alloy Steels
b) The fourth symbol is a letter code .
A The steel is supplied to a chemical compostion determine by analysis of the batch sample.
H The steel is supplied to a hardenability specification
M The steel is supplied to a Mechanical Property specification.
S The steel is a stainless steel
c) The fifth and sixth symbol is a number is the actual mean carbon content x 100
Esiampl / Example
070M20
Carbon Steel 0.7% magnesium supplied as normalised with 0.2% carbon
Or “Workshop Mild Steel”

8. CÔDAU DUR CARBON “POBLOGAIDD”
CODES FOR “POPULAR”
CARBON STEELS
CÔDAU DUR CARBON “POBLOGAIDD”
Dur Carbon / Carbon Steel
BS M07 (EN1A)
Dur carbon isel, sy’n torri yn rhwydd ac yn addas ar gyfer ei beiriannu. Ar gael mewn ffurf fflat, crwn a hecsagon .
A low carbon, free cutting, mild steel suitable for machining using automatic and CNC machines. Available as rolled or normalised in round, flat or hexagon form
BS M20 (EN3A)
Dur meddal ar gyfer defnydd cyffredinol – gellir ei weldio a’i beiriannu ac ar gael mewn amrywiaeth o siapiau.
A mild steel used for general purposes. Suitable for lightly stressed fasteners ,shafts etc. Can be easily machined and welded. Available hot rolled, normalised, cold drawn or turned. Supplied in Black round or square , bright round square, flat and hexagon.
BS M30 (EN5/EN6)
Dur a chryfder canolig – defnyddir i gynhyrchu siafftiau, bolltau, roleri ac yn y blaen (ar gael yn grwn. fflat neu sgwar).
A medium strength steel. Used to make, shafts, racks, pinions, studs, bolts, nuts, rollers, etc. Supplied as square bar, or round bar or flat.
BS M40 (EN8)
Dur a chryfder canolig – ar gael mewn ffurf sgwar, crwn a fflat.
A medium strength steel. Suitable for stressed pins, shafts studs, keys etc. Available as rolled or normalised. Supplied as square bar, or round bar or flat.
BS M55 (EN9)
Dur carbon canolig gellir ei galedu.
A hard wearing medium carbon steel which can be hardened. Available as hot rolled, normalised, Cold drawn or turned. Sections available black round, black square, bright round and black flat.
BS M15 (EN32)
Dur meddal ei gyfer ei grofennu ar gyfer pwrpasau cyffredinol o fewn peirianneg. Defnyddir i gynhyrchu geriau a roleri.
A case hardening mild steel suitable for general engineering applications. When case hardened results in a hard surface with a tough core. Used for making gears cams and rollers etc. Supplied as black round bar and sections

9. CÔDAU DUR GWRTHSTAEN “POBLOGAIDD”
CODES FOR “POPULAR”
STAINLESS STEELS
CÔDAU DUR GWRTHSTAEN “POBLOGAIDD”
Dur Gwrthstaen / Stainless Steel
BS S21 (EN56)
Gellir ei galedu a’i dymheru er mwyn cryfder. Gellir ei ddefnyddio ar gyfer cytleri, offer llawfeddygol, falfiau a siafftiau.
Martensitic (Magnetic), can be hardened and tempered to give improved tensile strength. FM** grade. Typical applications include cutlery, surgical instruments, fasteners, valves, spindles and shafts.
BS S29 (EN57)
Defnyddir i gynhyrchu cytleri a falfiau ac yn y blaen.
Martensitic (Magnetic). Supplied heat treated with a high tensile strength. Typical applications include cutlery, surgical instruments, fasteners, valves, spindles and shafts.
BS S15 typ (EN60)
Gwan ond yn hydwyth – defnyddir ar gyfer offer arlwyo, egsost ceir ac yn y blaen.
Ferritic. Low Strength but good ductility. Used food processing and catering equipment and automotive trim,car exhaust systems etc.
BS 970 Grade 304S15 (EN58-)
Aml bwrpas ac yn boblogaidd iawn ar gyfer ei ddefnyddio mewn sefyllfaoedd domestig.
Austenitic (Non-Magnetic)Cannot be heat treated but work hardens. Readily formed and welded,used mainly in domestic, dairy and decorative appliances general purpose grade for corrosion resistant applications. This grade is the most widely used of all stainless steels. Its chemical composition,provide the best all-round performance S.S. at relatively low cost. It has excellent low temperature properties. Lower Carbon grades (S15 and less) have improved weldability.
BS 970 Grade 316S16 (EN58J)
Yn gwrthsefydd cyrydiad.
Austenitic (Non-Magnetic)Cannot be heat treated but work hardens. It offers high resistance to corrosion. Generally machined components and pipe fittings. This grade is almost as popular as the 304 grade the increased Mo content makes the steel more suitable for resisting pitting and crevice then 304 Grade.  Lower Carbon grades (S15 and less) have improved weldability.
BS 970 Grade 321S12 (EN58B-C)
Ni ellir derbyn triniaeth gwres.
Austenitic (Non-Magnetic)Cannot be heat treated but work hardens. Titanium stabilized, which offers improved welding properties.
BS 970 Grade 310S31
Yn gweithio yn dda mewn tymheredd uchel.
Austenitic (Non-Magnetic). Posesses good resistance to scaling at high temperatures. For continuous high temperature service in the range C

10. CODES FOR “POPULAR” CÔDAU DUR ALOI ALLOY STEELS “POBLOGAIDD”
BS M36 (EN16)
Hydwyth a gyda cryfder mecanyddol da.
A manganese molydenum steel with good ductily and mechanical strength. Available in heat treated condition e.g (R,S,T).Supplied as black round or square bar and bright round or square, and hexagons.
BS M40 (EN19)
Defnyddir ar gyfer sefyllfaoedd lle mae angen cryfder.
A 1% typical chromium molybdenum steel with higher molybdenum. Can be induction hardened. Used for gears, and high strength shafts etc. Suitable for higher strength applications when resistance to shock is required. Available annealed. Supplied as black round or square bar and bright round or square, and hexagons.
BS M40 (EN24)
Cryfder a gwydnwch yn amlwg.
A nickel chromium molybdenum steel with high strength and toughness. Used for gears axles and high strength studs. Supplied as rolled, annealed and hardened and tempered. Supplied as black round or square bar and bright round or square, and hexagons
BS M13 (EN36)
Ansawdd da lle mae angen arwyneb da.
A high quality nickel chromium case hardening steel. Can be hardened to provide hard surface with a strong tough core. Used for high duty gears and shafts. Supplied in as-rolled condition in black square and round bar and bright round.
BS M24 (EN40B)
Craidd gwydn gyda arwyneb da.
A 3% chromium molybdenum nitriding steel. Provide good tough core strength with a hard nitrided surface for wear resistance. Supplied in as-rolled, annealed and hardened and tempered condition in black square and round bar.

11. METAL COLOUR CODING SYSTEM
CÔD LLIW METALAU
Pan yn prynu dur gan cyflenwr mae ganddynt system lliwio pennau pariay ayyb er mwyn adnabod y dur yn sydyn – ond nid oes system rhyngwladol felly mae pob cyflenwr yn defnyddio lliwiau gwahanol - rhaid archebu dur drwy ddefnyddio codau BS970!
METAL COLOUR CODING SYSTEM
Steel suppliers use a colour coding system to quickly identify a steel. The paint is located at the ends of stock – however there is no international standard for colour coding so each supplier use different colours- when ordering steel use the BS 970 coding system!
Esiampl o system lliwio gan:
Example colour coding from :

12. ANFETELAU / NON -METALS DEFNYDDIAUSYNTHETIG /
DEIAGRAM DOSBARTHIAD ANFETELAU
NON - METALS CLASSIFICATION DIAGRAM
ANFETELAU / NON -METALS
DEFNYDDIAUSYNTHETIG /
SYNTHETIC MATERIALS
DEFNYDDIAU NATURIOL /
NATURAL MATERIALS
ELASTOMERAU /
ELASTOMERS
THERMOPLASTIG
THERMOPLASTIC
ELASTOMERAU /
ELASTOMERS
PREN /
TIMBER
MINERALAU /
MINERALS
DEFNYDDIAU SMART
SMART MATERIALS
THERMOSET
CERAMIG
CERAMICS

13. METALAU ANFFERUS – dim Haearn / NON FERROUS METALS – no Iron
COPR
Defnyddi’r copr pur i wneud cydrannau trydannol oherwydd ei dargludedd uchel – ail i arian ond llawer rhatach. Mae rhy feddal I’w weithio yn fecanyddol yn
bur, felly defnyddi’r Copt pich – gwydn, mae hwn yn cynnwys ocseid copr sy’n ei wneud yn fwy gwydn – priodweddion copr, cryfder uchel, hydwythedd uchel, atal cyrrydu, gallu ei sodro, ar gael fel rodiau, barrau, tiwbiau a llenfetel.
ALIWMINIWM
Mae aliwminiwm pur yn 33% yn ysgafnach na
metel, ond llawer gwanach ac yn anodd i’w
weithio drwy ymuno, felly rhaid adio metelau
eraill i greu aloi sydd llawer mwy cryf a gwydn
fel yr aliwminiwm sydd ei angen mewn
cydrannau awyrennau.
Mae’r aliwminiwm sydd yn y gweithdy yn
cynnwys tua 1% o Silicon felly yn gryfach a
mwy gwydn, hawdd i’w ymuno ai dorri.
PRES
Aloi o copr a sinc, gall pres ei ddinistrio gan ddwr halen oherwydd cynnwys y sinc, felly maent yn adio dipyn o
Tin ir alloy. Mae press yn torri yn daclus ar
beiriannau – defnyddio ar gyfer cydrannau
plymio a partiau falfiau
COPPER
Pure copper used for electrical components because of its high conductivity – second to silver but a lot cheaper, however its too soft for mechanical work. Tough – pitch copper is used for mechanical tasks as its tougher due to the inclusion of copper oxide. – properties– high strength, ductile, high electrical conductivity, resists corrosion, can be soldered or brazed available in rods wire sheet and tubes.
ALUMINIUM
Pure aluminium is 33% the weight of steel, but weaker and very difficult to join by soldering or welding, so it’s alloyed with other metals to create stronger aluminium such as the components needed in aircraft.
Workshop aluminium contains up to 1% Silicon so its stronger and tougher easily joined and machined.
BRASS
Alloy of copper and zinc, brass is attacked by salt water due to the zinc being attacked so Tin is added. Brass machines to a very high finish – used a lot for plumbing and valve parts

14. NON - METALS ANFETELAU Esiamplau / examples alumina silicon carbide
CERAMICS
Very hard material available in 4 groups CRYSTALLINE (hardest – used to make cutting tools) AMORPHOUS, BONDED and CEMENTS. They are very strong in compression, but brittle because they are very hard – used as cutting tools and can cut HSS tools. They can withstand high temperatures and are used as furnace liners, and are excellent electrical insulators hence their use as insulators on high voltage cables.
WOODS
Good fatigue strength because of its ability to bend .
Three classes of timber
Softwood – cheaper than hardwood, used for machine packaging, pallets, building frames, example – pine.
Hardwood – More expensive than soft, used for decorative work, flooring or exposed building framework, examples – oak, mahogany
Processed – fairly cheap compared to natural woods and less likely to distort – many types available with many applications, examples – plywood, MDF.
ANFETELAU
SERAMIG
Defnydd caled iawn wedi ei rannu i 4
dosbarth CRYSTALLINE ( caletach –
defnyddir fel arfau torri) AMRPHOUS,
BONDED a CEMENTS. Cryf iawn dan
llwyth cywasgiad, ond yn frau oherwydd
yn galed – gall arf seramig dorri arf
HSS. Gallant wrthsefyll tymheredd
uchel a defnyddir i leinio ffwrneisi,
ynyswyr trydannol gwych felly llawer
o ddefnydd fel ynyswyr as
llinellau foltedd uchel.
COED
Cryfder da pan o dan pwysau lluddedu
Tri dosbarth o coed:
Meddal – rhatach na caled – defnyddio ar gyfer
pacedu, storio, fframwaith adeiladu,
enghraifft - pinwydden,
Caled – Llawer drytach na meddal ai ddefnyddio
ar gyfer gwaith deiniadol fel lloriau neu fframiau
adailadau gweladwy, esiamplau - derw,
mahogani
Prosesu – defnydd rhad iw gymharu a pren
Naturiol ac yn llai tebygol o colli siap – nifer fawr
ar gael gyda swyddogaeth eang, esiamplau –
pren haenog, MDF,
Esiamplau / examples
alumina
silicon carbide
zirconia
silicon nitride
Diamond
Cubic boron nitride
Magnesia
Tungsten Carbide

15. PLASTIG THERMOSET / THERMOSETTING PLASTIC
Plastigion / Plastics
PLASTIG THERMOSET / THERMOSETTING PLASTIC
Plastigion ar gael mewn ffurf powdwr neu graniwl ac wed ei wneud o “llenwr” a resin synthetig. Cael eu mowldio fel arfer o dan bwysau a gwres. Unwaith mae wedi “ciwrio” gan y gwres ni all ei ail siapio
A plastic available in powder or granular form nade from a synthetic resin with a filler. Mostly moulded under pressure and heat. Once curing has occurred under heat it cannot be re heated and re shaped
THERMOPLASTIG / THERMOPLASTIC
Plastigion gwahanol thermoset, posib ail siapio neu torri fynnu ai ailgylchu – Wedi gweld y symbolau yma or blaen?
The opposite to thermosetting plastic, possible to reheat and reshape, or cut up and recycle – Have you seen these symbols?

16. PLASTIG THERMOSET / THERMOSETTING PLASTIC
Phenolig Yn gryd, brau acyn insiwleiddwyr trdanol da. Gall wrthsefyll tymheredd hyd at 150 C.
Sar gyfer plygiau, swits ac offer trydanol cyffredinol.
Plastig Amino -UF..Urea Formaldehyde Caled, yn gwrthsefyll cemegau a sgriffiniadau. Yn ddiogel gyda bwyd. Defnydd: plastigau domestig, seddau toiledau, blychau bwyd.
Plastig Amino-MF..Melamine Formaldehyde Yn galetach na UF . Gwrthsefyll gwres a staen. Defyddir ar gyfer offer domestig. Gall laminadau gwydr wrthsefyll gwres hyd at 200 C.
Polyestr. Yn gwrthsefyll UV, dwr, asid a thoddyddion.
Wedi eu cryfhau a ffibrau gwydr. Defnyddir ar gyfer cyrff ceir a chychod.
Epocsidau Maent yn wydn ac yn gwrthsefyll alcali. Defnyddir ar gyfer cydrannau electroneg. Defnyddir epocsidau gwydr ar gyfer ffatroedd cemegolion.
Phenolics Phenolics are strong, brittle, good electrical insulators
and can withstand temperatures up to 150 deg. C..
Uses:-electrical plugs, switches, general electrical fittings.
Amino Plastic -UF..Urea Formaldehyde Good hardness, abrasion and chemical resistance. Safe with
food lots of colours.. Uses:- domestic plastics e.g toilet seats,
food containers.
Aminoplastic -MF..Melamine Formaldehyde Harder than UF . Good heat and stain resistance. Generally
used for domestic table ware. Glass reinforced laminates have
a heat resistance up to 200 deg. C.
Polyesters. Resistance to UV, water, acids, alkalis and organic solvents.
Usually reinforced with fibres mostly in the form of woven cloth
chopped strands (GRP). Uses:- roof sheeting, car bodies,
tanks, boat hulls etc.
Epoxides They are tough and good resistance to alkalis.
Uses:- encapsulate electronic components.
Glass-reinforced epoxides are used in chemical plants

17. THERMOPLASTIG / THERMOPLASTIC
ABS (AcronitrileButedeneStyrene Gwydn a gallu io wrthsefyll sgriffiniadau. Gellir ffurfio ABS drwu fowldio chwitrell, allwthio, mowldio cylchol a ffurfio drwy wres. Defnyddir ar gyfer cychod, peipiau a llestri domestig.
PVC (PolyVinylChloride ) Hyblyg iawn. Defnyddir i gynhyrchu ceblau/insiwleiddio, gwadnau esgidiau a menyg diwydiannol.
UPVC (PolyVinylChloride ) Caled a gwydn gyda nodweddion gwrthsefyll tywydd da. Gellir ei allwthio, chwistrell fowldio, mowldio cylchol a ffurfio gyda gwres. Defnyddir ar gyfer poteli, a fframiau ffenestri..
Polyethylene Yn wydn ar dymheredd isel gyda nodweddion cemegol a thrydanol da ar gyfer insiwleiddio.
LDPE- Polyethlen dwysedd isel – mae hwn yn wydn ac yn hyblyg gyda nodweddion gwrthsefyll cemegol. Defnyddir ar gyfer peipiau.
HDPE- Polyethylen dwysedd uchel - yn gryfach ac yn anhyblyg. Defnyddir ar gyfer tanciau, peipiau a biniau ysbwriel.
Polypropylen Nodweddion da yn gwrthsefyl. Cemegau – gellir ei allwthio, chwistrell fowldio, chwyth fowldio a ffurfio gyda gwres.
ABS (AcronitrileButedeneStyrene Tough, stiff, abrasive resistant. ABS can be injection moulded, extruded, rotationally moulded and thermoformed. Typical applications include boat hulls, telephones, piping/fittings, and domestic durables.
(Plasticised) PVC (PolyVinylChloride ) Flexibility Used for cable/wire insulation, soles of footwear, and coating linen liners of industrial gloves.
(UnPlasticised) UPVC (PolyVinylChloride ) Hard/tough/ strong and stiff with good weathering properties. UPVC can be extruded, injection moulded, blow moulded, rotationally moulded and thermoformed. It is mostly used for making pipe/pipe fittings, bottles, and window frames .
Polyethylene Tough at low temperatures with excellent chemical and electrical insulation properties.
LDPE- Low Density Polyethylene is very tough and flexible with excellent chemical resistance. Used for pipes
HDPE- High Density Polyethylene is much stronger and stiffer. It is used for tanks, pipes dustbins etc.
Polypropylene Excellent fatigue resistances, chemical and electrical properties. Can be extruded, injection moulded, blow moulded, rotationally moulded and thermoformed.

18. THERMOPLASTIGION AMORPHOUS /AMORPHOUS THERMOPLASTICS
Acrylig Yn dryloyw – yn addas ar gyfer dei ddefnyddio oddi allan, ddim yn colli lliw. Mae’n anhyglyg, cryf ac yn gwrthsefyll dryllio.
Gellir ei allwthio, chwistrell fowldio a ffurfio gyda gwres. Defnyddir ar gyfer arwyddion, panelau a lensiau.
Polycarbonad Gwydn, tryloyw, anhyblyg a chryf. Gwrthsefyll trydan ac yn gallu gwrthsefyll elfenau allanol.
Gellir ei allwthio, chwistrell fowldio, chwyth fowldio a ffurfio gwactod. Defnydd: - helmedau a gorchuddion lampau stryd.
Polysulphones Cryf ac anhyblyg. Nid ydynt yn llosgi yn rhwydd ond yn gallu creu perygl gan gynhyrchu mwg. Gellir ei allwthio, chwistrell fowldio a ffurfio gyda gwres.
Defnydd: cabin i’r teithwyr mewn awyren, cydrannau trydanol sydd angen gweithio mewn tymheredd uchel.
Acrylics Completely transparent and optically clear.
Stable to outdoor weathering and do not discolour or degrade under UV light. Acrylics are stiff, strong and do not shatter.
Acrylics can be extruded, injection moulded, and thermoformed. Uses: - viewing panels, light housings, lenses and illuminated signs.
Polycarbonates Tough, transparent, stiff and strong. Good electrical insulation properties. Polycarbonates have moderate outdoor weather resistance.
Polycarbonates can be injection moulded, extruded, blow moulded, and vacuum formed. USES: - include street lamp covers, safety helmets.
Polysulphones Strong and stiff. They do not easily burn and do not present a smoke hazard. They can be extruded, injection moulded and thermoformed.
Uses:- passenger cabins in aircraft and electrical components requiring high service temperatures.

19. THERMOPLASTIGION CRYSTALLINE THERMOPLASTICS
Neilon
Mae deunyddiau neilon yn wydn, cryf ac yn gwrthsefyll sgraffiadau. Gellir ei chwistrell fowldio, ffurfio cylchol a’i allwthio.
Defnydd: insiwleiddwyr, a chydrannau peirianneg e.e geriau, beryn a bwshys. Gellir defnyddio neilon gyda gwydr ar gyfer casyn offer trydanol.
Polyacetal..
Anhyblyg, cryf ac yn gallu gwrthsefyll tymheredd uchel.
Defnydd: ffitiadau ar gyfer peipiau, spring, geriau a berynau.
PTFE..Polytetrafluoroethylen.
Mae PTFE yn gwrthsefyll amgylcheddau ymosodgar, mae ganddo gyfernod isel o ffrithiant, priodweddau da a ran ffrithiant a gellir ei ddefnyddio ar dymheredd o hyd at 250 gradd C.
Gellir ei brosesu gan ddefnyddio technegau sintro arbennig. Mae siapiau cynhleth i’w beiriannu a flociau wedi eu sintro.
Defnydd: beryn, insiwleiddio ar gyfer ceblau, wyneb ar gyfer offer cegin.
Nylon
Nylon materials are stiff, strong,tough and abrasion resistant. Nylon can be injection moulded, rotationally moulded and extruded.
Uses: insulators, and engineering components such as gears, bushes, and bearings. Glass filled nylon is used to make power tool housings etc.
Polyacetals..
Stiff, strong, resist high temperatures .
Uses: pipe fittings, light-duty beam springs, meat hooks, gears, bearings etc.
PTFE..Polytetrafluoroethylene.
PTFE resists all common aggressive environments, has exceptional low coefficient of friction, first class electrical properties and can be used at temperatures up to 250 deg C.
It can be processed only be a special sintering techniques. Complicated shapes are generally machined from sintered blanks.
PTFE is used for bearings, bearing surfaces treatments, high frequency cable insulation, coating for cooking utensils etc etc

20. RECOGNISING PLASTICS
An easy guide!
ADNABOD PLASTIGION
Y ffordd hawdd!

21. COMPOSITES - REINFORCED PLASTICS
A composite materials is created by combining two or more materials that have very different properties.   The different materials work together to give the composite superior properties compared to the individual properties of the original materials.  Within the composite the different materials are identifiable, they do not dissolve or blend into each other. The three main types of composite materials are:
Particle filled composite ....Particles have approximately the same dimensions in all directions in a matrix.
An example of this type of composite is concrete
2. Discontinuous fibre- reinforced...fibres have limited length/diameter ratio in a matrix. 
  An example of this type of composite is Glass fibre
3. Continuous fibre-reinforced ... Continuous fibres are constructed by winding or by using prepared layers.
An example of this form of composite is the carbon fibre
Gellir creu deunydd cyfansawdd gan uno dau neu fwy o ddeunyddiau gyda priodweddau gwahanol. Mae’r deunyddiau yn gweithio gyda’u gilydd er mwyn creu deunydd gyda priodweddau arbenig i’w gymharu a’r deunyddiau gwreiddiol. O fewn y deunydd cyfansawdd gellir adnabod y deunydd gwreiddiol gan nad ydynt yn ymdoddi i’w gilydd.
Y prif fathau yw: 
Llenwad gronynau ....Gronynau gyda’r un mesuriadau mewn gwahanol gyfeiriadau o fewn matirics. Esiampl yma yw concret.
2. Ffibr Gwydr...fmae ffibrau sydd wedi ei gyfyngu mewn hyd a diamedr wedi ei gymysgu o fewn matrics.
3. Ffibr parhaol... Defnyddir ffibrau gan eu gosod mewn haenau. Esiaml yma yw ffibr carbon.

22. DEFNYDDIAU SMART MATERIALS
Gellir newid a rheoli deunyddiau sydd a priodweddau gwahanol gan ddigwyddiadau allanol. Dyma rai esiamplau:
Piezoelectric defnyddiau sy’n creu foltedd pan greir diriant
Aleoen cof neu polymerau cof yn gallu newid ffurf gyda gwres neu newidiadau diriant.
Ffurf cof magnetig mae’r aloeon yma yn newid eu ffurf gan ymateb i newid mewn maes magnetig
Polymerau sy’n ymateb i wres defnyddiau sy’n newid gyda gwres.
Halochromic – sef deunyddiau sy’n cael eu defnyddio lle mae angen newid lliw pan mae newid mewn asidrwydd. Un defnydd yma yw ei ddefnyddio i ddangos pa bryd mae metel yn rhydu.
Electrochromig sef deunyddiau sy’n newid eu lliw pan gyflwynir foltedd
Thermochromicg - sef deunyddiau sy’n newid lliw yn ddibynol ar eu tymheredd.
Photochromig – sef deunyddiau sy’n newid lliw gyda golau – e.e. sbectol haul sy’n tywyllu.
Deunyddiau Mecanyddol – yn newid ffurf gyda golau.
Deunyddiau adnewyddol – yn gallu trwsio eu hunain ac felly yn ehangu eu bywyd.
Elastomerau Dielectric (DE) - yn gallu ehangu o fewn maes electroneg (hyd at 300%)
Materials that have one or more properties that can be significantly changed in a controlled fashion by external stimuli,
Some examples are as following:
Piezoelectric materials are materials that produce a voltage when stress is applied.
Shape memory alloys and shape memory polymers Change shape through temperature changes or stress changes
Magnetic shape memory alloys are materials that change their shape in response to a significant change in the magnetic field.
Temperature-responsive polymers are materials which undergo changes upon temperature.
Halochromic materials are commonly used materials that change their colour as a result of changing acidity.
One suggested application is for paints that can change colour to indicate rust in the metal underneath them.
Electrochromic materials, which change their colour or opacity on the application of a voltage LCD’s
Thermochromic materials change in color depending on their temperature
Photochromic materials, which change colour in response to light—for example, light sensitive sunglasses that darken when exposed to bright sunlight.
Photomechanical materials change shape under exposure to light.
Self-healing materials have the intrinsic ability to repair damage due to normal usage, thus expanding the material's lifetime
Dielectric elastomers (DEs) are smart material systems which produce large strains (up to 300%) under the influence of an external electric field.