BAHAN KEJURUTERAAN - PLASTIK

http://ms.wikipedia.org/wiki/Plastik

PLASTIK

Dari Wikipedia Bahasa Melayu, ensiklopedia bebas.
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Istilah plastik merangkumi produk polimer sintetik atau semi-sintetik. Ia terbentuk daripada kondensasi organik atau penambahan polimer dan boleh juga terdiri daripada bahan lain untuk meningkatkan ketahanan atau ekonomi. Ada beberapa polimer alami yang termasuk plastik. Plastik dapat dibentuk menjadi filem atau gentian sintetik. Nama ini berasal daripada fakta bahawa banyak daripada mereka dapat dilentur, memiliki sifat keplastikan. Plastik direka dengan kepelbagaian yang sangat banyak dalam ciri-ciri yang dapat menahan panas, keras, kebergantungan dan lain-lain. Digabungkan dengan kemampuan adaptasinya, komposisi yang umum dan beratnya yang ringan memastikan plastik digunakan hampir di seluruh bidang industri.

Plastik dapat juga menuju ke setiap barang yang memiliki ciri-ciri yang deformasi atau gagal kerana ketegangan(lihat keplastikan (fizik) dan mulur).
Plastik dapat dikategorikan dengan banyak cara tapi paling umum dengan melihat tulang-belakang polimernya (vinilklorida}, polietilena, akrilik, silikon, uretana, dll.). Pengkelasan lainnya juga umum.

Plastik adalah polimer; rantai-panjang atom mengikat satu sama lain. Rantai ini membentuk banyak unit molekul berulang, atau "monomer". Plastik yang umum terdiri dari polimer karbon saja atau dengan oksigen, nitrogen, klorin atau belerang di tulang belakang. (beberapa minat komersial juga berdasar silikon). Tulang-belakang adalah bahagian daripada rantai di jalur utama yang menghubungkan unit monomer menjadi satu. Untuk mengetahui ciri-ciri plastik kumpulan molekul berlainan bergantung daripada tulang belakang (biasanya "digantung" sebagai baghaian dari monomer sebelum menyambungkan monomer bersama untuk membentuk rantai polimer). Penghasilan oleh kumpulan rantaian ini telah membuat plastik menjadi bahagian tak dapat dipisahkan dalam kehidupan abad ke-21 dengan memperbaiki ciri daripada polimer tersebut.

Pengembangan plastik berasal daripada penggunaan bahan semula jadi (seperti: karat, "shellac") hingga ke bahan yang diubahsuai secara kimia (seperti: karat semula jadi, "nitrocellulose") dan akhirnya ke molekul buatan-manusia (seperti: epoksi, polivinil klorida - PVC, polietilena).
Diambil daripada "http://ms.wikipedia.org/wiki/Plastik"


BAHAN PLASTIK

Material Plastik

Material plastik dapat dibagi menjadi 2, yaitu

• Thermoplastik
• Thermoset

Material plastik yang paling penting:

- Polypropylene(PP) - karpet
- Polyvinyl chloride(PVC) - paip
- High Density Polyethilene(HDPE) - botol
- Linear Low Density Polyethilene(LLDPE) - filem
- Low Density Polyethylene(LDPE) - filem
- Polyester, thermoplastic(PETE) - botol minuman ringan
- Polystyrene(PS) - kaset
- Phenolic - lem plywood

Bahan-bahan untuk membuat plastik:

1. Additive
- Antioksidan: mencegah oksidasi yang memutus rantai polimer
- Agen antistatik: menarik kelembaban permukaan supaya konduktif
- Pewarna: memberi warna atau efek seperti iluminasi
- Coupling agents: memudahkan untuk menempel ke bahan lain
- Curing agents: mempermudah penggabungan monomer kepolimer
- Flame retardants: mempersulit plastik terbakar
- Foaming/blowing agents: memberi gelembung udara atau foam
- Penstabil panas: mengurangi pemecahan polimer karena panas
- Penstabilan benturan: menguatkan plastik dari benturan
- Pelumas: mengurangi gesekan plastik keperalatan dan tidak lengket
- Nucleating agents: membantu pengkristalan polimer
- Plasticizer: menambah fleksibilitas, menurunkan titik leleh, dan encer
- Pengawetan: menjaga dari mikroorganisme- Pembantu proses: menaikkan produksi,
memperbaiki permukaan (anti lengket)
- Penstabil UV: mengurangi kerusakan akibat sinar Ultra Violet2.

2. Reinforcement

Bahan yang ditambahkan ke resin dan polimer untuk menambah kekuatan, daya tahan terhadap lenturan, dan kekerasan plastik.Reinforcement dibagi menjadi 2:
- Lamina: memberi lapisan seperti fiber glas, kain, atau lembaran material sehingga menjadi seperti roti sanwidch.
- Fibrous: mencampur dengan beberapa bahan seperti serat kaca, carbonaceous, serat polymer, serat inorganic, serat logam, dan serat hybrids.

3. Filler

Digunakan untuk mengisi sela-sela polimer dan mengurangi harga, tetapi kadang-kadang harga filler lebih mahal dari polimer.

Keluarga plastik juga merupakan bahan-bahan yang dibuat dari bahan petrokimia. Keluarga plastik terbahagi kepada 2 jenis.

Termoplastik [Thermo Plastic]
SIFAT
- Boleh diacu (dibentuk) berulang kali melalui proses pemanasan dan penyejukan.
- Tidak tahan haba
CONTOH (KEGUNAAN)
Politena untuk membuat beg plastik.
Polisterina untuk membuat bekas makanan sejuk (Ta Pau).
Polivinil Klorida/PVC untuk membuat paip air.

Plastik Termoset [Thermoset Plastic]
SIFAT
- Boleh diacu hanya sekali sahaja.
- Tahan haba.
CONTOH (KEGUNAAN)
Bakelit untuk membuat soket elektrik.
Melamina untuk membuat pinggan mangkuk.
Gam Epoksi untuk membuat gam industri.

4. MASALAH PENCEMARAN

Kedua-dua polimer sintetik diatas tahan lama dan tidak mudah mereput [Non Biodegradable]. Oleh itu ia sangat mencemarkan alam sekitar jika tidak diurus dengan baik. Pencemaran yang berasal dari polimer sintetik menyebabkan :

• Longkang tersumbat yang seterusnya mengakibatkan banjir kilat serta pembiakan nyamuk.
• Kehidupan laut mati. Penyu yang menyangka bahan plastik adalah makanan boleh menyebabkan ia tercekik dan mati. Hidupan laut yang berharga itu akan pupus.
• Pencemaran udara. Apabila bahan plastik dibakar ia akan menghasilkan gas toksik (beracun). Gas toksik ini menyebabkan penyakit seperti kanser. Gas ini juga menyebabkan penipisan lapisan ozon.

Pembuangan serta penggunaan polimer sintetik perlu diurus dengan baik. Antara langkah-langkah yang boleh dilakukan adalah seperti :

Kitar Semula.
Semua polimer sintetik yang telah digunakan boleh dibawa kekilang untuk diproses semula kepada bahan yang berguna. Beg plastik boleh diguna semula.
Had
Menghadkan penggunaan plastik serta memilih untuk menggunakan bahan yang mudah "terbiodegradasi" (mereput jika dibuang) seperti kertas. Kerusi kayu boleh menggantikan kerusi plastik.
Pelupusan
Membakar bahan plastik dalam insinerator [Incinerator] supaya gas toksik yang dikeluarkan dapat dikurangkan.

KEPENTINGAN POLIMER DALAM KEHIDUPAN MANUSIA

Walaupun polimer sintetik telah dikenalpasti sebagai bahan pencemar ia memainkan peranan yang penting dalam kehidupan manusia. Ia merupakan satu pilihan dalam pembuatan bahan yang tahan lama dan dengan ini sangat murah. Ciri-ciri istimewanya seperti ringan telah menyebabkan terciptanya alat-alat seperti baldi, pasu bunga dan kerusi yang mesra pengguna. Oleh kerana negara kita menghasilkan bahan petroleum maka industri petrokimia telah menyumbangkan kepada pendapatan negara. Industri hiliran yang berasasaskan polimer sintetik penting dan telah dikenalpasti sebagai penyumbang kepada ekspot negara.
(sumbangan http://www.oasis4.netfirms.com/b57.html)

Bacaan lain

TONGKOL JAGUNG PENGGANTI PLASTIK??
POLYURETHANE

TUGASAN RBT1

Brass & Brass Products (Abdullah)
EyeBolt & Nuts (Aida)
Free Cutting Steel (andrew)
Hammers
Hand Hammers (Bilyemban)
Hand Tools
Hardware
Iron
Iron & Iron Products
Metal & Metal Products
Parts & Supplies (Fahmi)
Pliers
Pneumatic Portable Screwdrivers, screwdriver (Mohamad Saiful)
Screwdrivers , screwdrivers (Md Zuhairi)
Spanners (Nazirah)
Steel
Steel (Nor Asilah)
Steel Products & Services
Tools
Tools (nur affini)

Daripada 20 elemen di atas, anda perlu mengambil satu tajuk mengikut urutan nama dalam blog ini dan dapatkan link berkaitan tajuk tersebut. Contohnya:

Abdulah mengambil tajuk brass &brass product
..
..
Nur affini mengambil tajuk tools

Untuk link yang sama, berbincang dan pastikan bahan tidak sama dan bertindih.
Sendkan link atau nota kepada pensyarah sebelum 25/3/2008
Dalam ruangan subjek tolong tuliskan nama penuh, opsyen dan tajuk anda

Sekian terima kasih.

BAHAN KEJURUTERAAN LOGAM - LOGAM

Logam

Dari Wikipedia Bahasa Melayu, ensiklopedia bebas.
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Dalam bidang kimia, logam adalah sejenis unsur yang bersedia untuk membentuk ion (kation) dan mempunyai ikatan logam. Logam-logam biasanya diterangkan sebagai sebuah kekisi ion-ion positif (kation) yang dikelilingi awan-awan elektron tak setempat. Logam adalah satu daripada tiga kumpulan unsur yang dikenalpasti melalui sifat-sifat pengionan dan ikatan, yang lainnya adalah metaloid dan bukan logam. Di dalam jadual berkala, satu garis pepenjuru yang dilukir daripada boron (B) kepada polonium (Po) membezakan logam dan bukan logam. Unsur-unsur pada garis ini adalah metaloid, kadang kala dipanggil ala logam; unsur-unsur ke sebelah bawah kiri merupakan logam-logam, manakala sebelah atas kanan adalah bukan logam.

bacaan seterusnya KLIK SINI


BARANG LOGAM

Bolts & Nuts

Bolted joints are one of the most common elements in construction and machine design. They consist of cap screws or studs that capture and join other parts, and are secured with the mating of screw threads.
There are two main types of bolted joint designs. In one method the bolt is tightened to a calculated torque, producing a clamp load. The joint will be designed such that the clamp load is never overcome by the forces acting on the joint (and therefore the joined parts see no relative motion).
The other type of bolted joint does not have a designed clamp load but relies on the shear strength of the bolt shaft. This may include clevis linkages, joints that can move, and joints that rely on locking mechanism (like lock washers, thread adhesives, and lock nuts).

bacaan seterusnya KLIK SINI

Brass

Properties
The malleability and acoustic properties of brass have made it the metal of choice for brass musical instruments such as the trombone, tuba, trumpet, euphonium, and the French horn. Even though the saxophone is classified as a woodwind instrument and the harmonica is a free reed aerophone, both are also often made from brass. In organ pipes designed as "reed" pipes, brass strips are used as the "reeds".
Brass has higher malleability than copper or zinc. The relatively low melting point of brass (900 to 940°C, depending on composition) and its flow characteristics make it a relatively easy material to cast. By varying the proportions of copper and zinc, the properties of the brass can be changed, allowing hard and soft brasses.

bacaan seterusnya KLIK SINI
Brass & Brass Products
Eye Bolts & Nuts
Free Cutting Steel
Hammers
Hand Hammers
Hand Tools
Hardware
Iron
Iron & Iron Products
Metal & Metal Products
Parts & Supplies
Pliers
Pneumatic Portable Screwdrivers
Screwdrivers
Spanners
Steel
Steel
Steel Products & Services
Tools
Tools

BAHAN-BAHAN KEJURUTERAAN - KAYU

PENYIMPANAN KAYU

CHESAPEAKE WOODCRAFT
WOODWORK
STANDARD SIZE

Medium-density fibreboard
From Wikipedia, the free encyclopedia

Medium-density fiberboard output in 2005

Medium-density fiberboard (MDF or MDFB) is an engineered wood product formed by breaking down softwood into wood fibers, often in a defibrator, combining it with wax and resin, and forming panels by applying high temperature and pressure. It is a building material similar in application to plywood but made up of separated fibers, not wood veneers. It is denser than normal particle board.
Large-scale production of MDF began in the 1980s. Its name derives from the distinction in densities of fiberboard. MDF typically has a density of 600-800 kg/m³, in contrast to particle board (160-450 kg/m³) and to high-density fiberboard (600-1450 kg/m³). Similar manufacturing processes are used in making all types of fiberboard.
MDF is also known as Customwood or Craftwood.[citation needed].
MDF has been controversial in regard to its use of formaldehyde resins and the associated health risks. Thus, other resins are being considered and used instead of formaldehyde.
MDF is often used in school projects because of its flexibility.

A sample of MDF

Hollow extruded MDF decking boards, which appear to have the colouring/preservative in the manufacture
Contents[hide]
1 Manufacturing
2 Comparison to natural woods
3 Different kinds of MDF
4 References
5 External links


Manufacturing
MDF is a wood product created by breaking down a softwood into a powder, which is then mixed with wax and resin. The final finish is created by submitting the boards to high pressure and temperatures.
In Australia the main species of tree used for MDF is plantation-grown radiata pine. However a variety of other products have also been used including other woods, waste paper and fibers.
The trees are debarked after being cut. The bark can be sold for use in landscaping, or burned in on-site furnaces. The debarked logs are sent to the MDF plant where they go though the chipping process. A typical disk chipper contains 4-16 blades. Any resulting chips that are too large may be re-chipped; undersized chips may be used as fuel. All chips are then washed and checked for defects.
The chips are then compacted using a screwfeeder, and will be heated for 30-120 seconds to soften the wood; they are then fed into a defibrator which maintains high pressure and temperature. The pulp that exits from the defibrator is fine, fluffy, and light in weight and in colour.
From the defibrator the pulp enters a blow line where it is joined with wax (to improve moisture resistance) and resin (to stop the pulp from forming bundles). The material expands in size and is then heated by heating coils. When it comes out it may be stored in bins for an indefinite length of time.
After this drying period the board goes through a "Pendistor" process which creates 230-610 mm thick boards. Then it is cut and continues to the press. Here it is pressed for a few minutes, to make a stronger and denser board.
After pressing MDF is cooled in a star dryer, trimmed and sanded. In certain applications boards are also laminated for extra strength.
The Environmental Impact of MDF has greatly improved over the years. Today many MDF boards are made from a variety of materials. These include other woods, scrap, recycled paper, bamboo, carbon fibers and polymers, steel, glass, forest thinning and sawmill off-cuts.

Comparison to natural woods
Benefits of MDF:
Some varieties are less expensive than many natural woods
Isotropic (no grain), so no tendency to split
Consistent in strength and size
Flexible. Can be used for curved walls or surfaces.
Shapes well with a router.
Drawbacks of MDF:
Heavier (the resins are heavy)
Swells and breaks when waterlogged
Warps or expands if not sealed
Contains urea-formaldehyde which may cause eye and lung irritation when cutting and sanding
Dulls blades more quickly than many woods
Though it doesn't have a grain in the plane of the board, it does have one into the board. Screwing into the edge of a board will generally cause it to split in a fashion similar to delaminating.

Different kinds of MDF
There are different kinds of MDF, which are sometimes labeled by color:
Moisture-resistant is typically green
Fire-retardant MDF is typically red
High finition for powder lacking
Lighter densities of fiberboard are commonly marketed as ultralight or LDF boards.

References

External links
A video podcast from podcastschool.net
The Production Process of Humewood MDF (Humewood is a product of Hume Fiberboards Sdn Bhd, a Malaysian fiberboard manufacturer)
Wood Dust - dangers of exposure to wood dust, including MDF dust (from the Worker's Health Centre)
Medium Density Fiberboard - from Investment New Zealand, a division of New Zealand's economic development agency.
A personal experience of MDF toxicity
Retrieved from "http://en.wikipedia.org/wiki/Medium-density_fibreboard"
Categories: All articles with unsourced state


KAYU

Botanical Names: Hevea brasiliensisFamily
Name: Euphorbiaceae
Others Name: Rubbertree ( Malaysia ,Singapore ), para rubber , Arbol de caucho (Venezuela), Sibi-sibi (Guyana), Mapalapa (Surinam), Seringa, Seringueira (Brazil), Capi, Jeve, Shiringa (Peru). Jebe, Arbre De Para ( French), Parakautschukbaum, Cauchotero de Pará ,Siringa , Seringueira-branca, rapa (Fiji)
Working Properties:Obtained by tapping the trunks of the trees , good strength characteristic, easy machining and processing properties. Additionally, The wood is reported to saw without difficulty, planes easily to a smooth surface; tends to split in nailing. Therefore it can easily be stained and finished to meet various market requirements.
Durability: The wood is perishable and stains readily. Also highly susceptible to borer and termite attack as well as powder-post beetles.
Wood Appearance: high color ( This wood is whitish yellow when freshly cut and seasons to cream, straw or light brown, often with a pinkish tinge.)
Rubberwood story:The rubber tree was originated came from Brazil named Hevea brasiliensis from the species family of Euphorbiaceae and widely planted for the production of latex in South East Asia country, mainly in Indonesia, Malaysia and Thailand.At the begining stage, rubber trees just for use in produce milky liquid known as latex that circulates through small tubes or veins for every 5- 7 years of growing. And these trees will discontinue for produce latex after 21 - 25 year, so at this moment, due to unproductive, therefore this trees are demand to fell (either replanting or other planning). Initially the felled trees were of low commercial value and mainly used as firewood, hence, due to worldwide technological developments & environment hazard, All these threes became valuable sources especially for furniture industrial. Today, Rubberwood becomes one of the most demanding and popular timbers for furniture maker (for both local & oversea market), therefore, this wood now can have categorised as environment-friendly due to hazard free to the environment and the supply is sustainable. In the sense that we are now using what was going as waste. Today Malaysia become one of the major resource and country who successful for supplying & exporting rubberwood ( for both sawn wood, raw, semi-finished, finished good and furniture accessories ) and for the production of panel products such as particleboards, woodfibre cement-bonded particleboards ,fibreboards (MDF), plywood and other products for both local and oversea market demand.
Perabut Seong Aik (or known as PSA ) is one of the manufacturer who leading to produce rubber wood furniture. click here for product view

Jenis kayu

Kayu dalam pasaran

papan buatan

MESIN

Terdapat beberapa jenis mesin yang digunakan di dalam bengkel. Antaranya:
- mesin yang menggunakan kuasa elektrik
- mesin yang menggunakan kuasa hidraulik
- mesin yang menggunakan kuasa pneumatik
- mesin yang menggunakan konsep tuas

ALAT TANGAN

Alat tangan merupakan alat yang digunakan untuk melakukan kerja-kerja ketukangan dalam menyiapkan kerja ataupun projek.
Terdapat banyak jenis alat tangan dengan pelbagai fungsi. Dalam mata pelajaran ini, alat tangan dikhususkan kepada kerja kayu dan logam. Bagaimanapun untuk tujuan pembelajaran dan pengayaan ilmu, beberapa tambahan diselitkan hasil sumbangan pelajar.

Alat tangan
Alatan tangan dibahagikan kepada beberapa bahagian mengikut fungsi dan kegunaannya. Antaranya:
- alat menanda
- alat memotong
- alat membentuk
- alat memasang dan
- alat menguji.
Latihan1 ( tarikh hantar 15/1/08 )
Namakan alat, jenis dan fungsi alatan tersebut.
Nama alatan: Tolok teleskop
Jenis alatan: Alatan mengukur
Fungsi: Untuk mengukur garis pusat gerek dan jarak-jarak lain

Machine Tool Accessories General
End Mill Holders
Shell Mill Arbor
Morse Taper Adapters
Collets Chucks & Collets
HSK Tooling
Quick change Tooling
Tapping Heads & Holders
Right Angle Heads
Boring Heads
Lathe Centers
Quick Change Tool Posts & Holder
Nama alatan: Pengaras spirit
Jenis alatan: Alatan Mengukur
Fungsi: Menguji ketegakan dan kerataan aras seperti tembok tiang dan lantai
Tools for the Dominant Hand
Form :-
claw hammer
pencil
chalk line
slip-joint plier
utility knife
Dominant-hand tools are the primary task drivers. A good, general-duty claw hammer should weigh 12 or 16 oz. and be a balance of comfort, control and maximum nail-driving power. A flat carpenter’s pencil won’t break as easily as an ordinary round one and works best for rough carpentry work. A chalk line is a must for snapping long, straight lines. It’s also essential as a plumb bob or string line. A slip-joint plier is a versatile tool for pulling nails and for simple electrical and plumbing work. The utility knife is a must for everything from cutting drywall to roofing work and should have extra blades, both straight and curved, stored in the handle.
Nama alatan : Andas
Jenis alatan : Alat memegang
Fungsi : Digunakan untuk menyokong benda kerja semasa kerja membentuk
Nama alatan : Perengkuh soket
Jenis alatan : Peralatan menyambung atau mengikat
Fungsi : Digunakan untuk memiuh atau memegang kepala bolt atau nat
Alatan bergabung
Nama alatan : Kunci Allen
Jenis alatan : Alatan memasang
Fungsi : Membuka dan memasang skru berkepala Allen
Nama alatan : Alat bergabung T
Jenis alatan : Alat memotong
Fungsi :Melakukan pemotongan untuk semua jenis dan saiz bahan yang kecil
Terdiri daripada : -tukul spring
-pemotong wayar
-pemotong wayar keras
-pisau
-gunting
-pemutar skru philiphs
Nama alatan : Alat bergabung tangan
Jenis alatan : Alat memotong
Fungsi : Memotong benda kerja seperti wayar
Terdiri daripada : -tukul spring
-pemotong wayar keras
-pemotong wayar
-pisau
-gunting
-pemutar skru philips
Nama alatan : Pisau pelbagai guna
Jenis alatan : Alatan memotong
Fungsi alatan : Membuka nat,memutar skru dan membuka tin
Penyimpanan alat
Nama alatan : Tool racks
Fungsi : Menyimpan dan mengelaskan alatan tangan
Nama alatan : WM369 super wrist magnet
Fungsi : Menyimpan alatan di tangan untuk memudahkan kerja
Nama alatan : Pegboard
Fungsi : Tempat menyimpan alat yang diletakkan di atas papan tergantung
Nama alatan : Meja kerja dan rak
Fungsi : Mengatur kedudukan dan mengelaskan bahan kerja serta alatan
(sumbangan Md Zuhairi Bin Md Saiaan Harry)

SUKATAN MATA PELAJARAN

REKA BENTUK DAN TEKNOLOGI I

Pensyarah : MOHD ALI BIN JEMALI
Sukatan mata pelajaran : Asas Binaan Awam
( 1 kredit – 15 jam teori )
klik2x untuk lihat lebih jelas.