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BERAT JENIS DAN
KERAPATAN KAYU
Fakultas Kehutanan
Universitas Tanjungpura
Friana Sari
G1011211245
Fisika Kayu Kelas G
DEFINISI BERAT JENIS
• Beratjenisadalahrasioantarakerapatansuatu
bahandengankerapatanair.
• Beratjenis: kerapatanrelatif(Tsoumis, 1991)
• Beratjeniskayu: rasioantarakerapatankayu(atas
dasarberatkeringtanurdanvolume padaKA tertentu)
dengankerapatanair padakondisianomaliair (suhu4,4°C.
Dimanakerapatanair padakondisitersebutsebesar1
g/cm3
• BJ = kerapatankayu/kerapatanair suhu4,4
• Kerapatankayu= Beratkayu/Volume
Berat Jenis
• Kerapatan didefinisikan sebagai massa atau
berat per satuan volume ™
Dinyatakan dalam
kg/m3 atau g/cm3 Kerapatan = berat (g)
volume (cm3)
KERAPATAN
Berat kayu merupakan jumlah berat
dari :
–Zatkayu(dindingsel)
–Ekstraktif
–Jumlahair yang adadidalamkayu.
Pada umumnya berat jenis kayu
bergantung kepada:
•Besarnyasel
•tebalnyadindingsel
BERAT KAYU
BJ dan
Porositas Kayu
• Kerapatan kayu berhubungan
langsung dengan
porositas(proporsivolume
ronggakosong)
• Hubungan langsungan taraproporsi
volume rongga dalam kayu(porositas)
dan kerapatan terjadi, karena
kerapatan zat kayu kering kira-kira
sama utk semua spesies, yaitu
sebesar1,5 g/cm3
• Berat jenis(BJ) zat kayu kering untuk
semua jenis kayu sebesar1,5.
• Vol. rongga= (1–BJKT/1,5) x 100 %
ZAT KAYU
• Kayu terdiri dari sel-sel dan
rangka sel sel(dinding sel) yang
terdiri atas zat kayu.
• Karena itu untuk kayu kering
tanur dengan berat dan volume
tertentu merupakan petunjuk
banyaknya zat kayu (jika
variasiadanya ekstraktif
diabaikan) dan juga petunjuk
volume udara yang ada dalam
rongga ronggasel yang kosong
Banyaknya zat kayu merupakan
petunjuk tentang :
• Kekuatan kayu, sifat
pengerjaan dan finishingnya•
• Rongga dalam kayu, yang
banyak
menentukanbanyaknya air
yang dapat diabsorbsi•
• Kerapatan kayu yang sangat
menentukanperubahan –
perubahan pada dimensi
kayu, yangdisebabkan karena
perubahan pada kadar airnya.
PENTINGN
YA BERAT
JENIS • Berat jenis: sifatfisikayang paling penting.
• Kebanyakansifatmekanikkayusangatberhub
ungandenganberatjenisdankerapatan.
• Kekuatandankekakuankayunaikdengannaik
nyaberatjenis.
• Hasilproduksipulp per satuanvolume
secaralangsungberhubungandenganberatje
nis.
PENENTUAN BERAT JENIS
• BJ = kerapatankayu/kerapatanair suhu
4,4o c
• Kerapatankayu= Beratkayu/Volume
• BJ kayubisadiukurpadavolume basah,
keringtanurataukeringudara(KA 12%)
• Berdasarkanvolume basah, BJ
kayumencerminkanberatkayunya(BJ
Standard)
• Kayuringan: BJ < 0,30
• Kayusedang: BJ 0,36- ,56
• Kayuberat: BJ > 0,56
PROSEDUR PENENTUAN BERAT JEN
• Prosedur penentuan berat jenis suatu
contoh uji kayu ™
Contoh uji berukuran
2×2×2 cm dalam kondisi segar (Ka diatas
TJS) atau direndam dalam air 3×24 jam
untuk memperoleh kadar air maksimum.
• ™
Volume contoh uji dapat diukur dengan
metode celup atau rendam (immersion
method) atau juga displacement method
VARIASI BERAT JENIS
.Umurpohon:semakintuaumurpohon,kerapatansemaki
ntinggi.
•Tempattumbuh(site) : tipe tanah, ketinggiantempat,
topografi, komposisitegakan, jaraktanam
•Posisikayudalambatang:
bagianpangkalbatangmemilikikerapatan(BJ)
lebihtinggidaripadabagianujung
•Kecepatantumbuh: semakincepatpertumbuhankayu,
kerapatansemakinkecil
KESIMPULAN
Kerapatan dan Kadar Air Kayu Berat jenis dan
atau kerapatan kayu merupakan salah satu sifat
fisik utama disamping kadar air kayu yang
mempunyai korelasi kuat dengan sifat mekanik
atau kekuatan kayu. Berat Jenis yang tinggi pada
suatu kayu maka kerapatan pada kayu tersebut
juga tinggi dan sifat fisika kayu tersebut juga
kuat dan bagus , begitupun sebaliknya.
THANK YOU
HTTPS://WWW.SCRIBD.COM/PRESENT
ATION/608926845/BERAT-JENIS-DAN-
KERAPATAN-KAYU-FAKULTAS-
KEHUTANAN-UNIVERSITAS-
TANJUNGPURA

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Bagi BERAT JENIS DAN KERAPATAN KAYU (1).pptx

  • 1. BERAT JENIS DAN KERAPATAN KAYU Fakultas Kehutanan Universitas Tanjungpura
  • 3. DEFINISI BERAT JENIS • Beratjenisadalahrasioantarakerapatansuatu bahandengankerapatanair. • Beratjenis: kerapatanrelatif(Tsoumis, 1991) • Beratjeniskayu: rasioantarakerapatankayu(atas dasarberatkeringtanurdanvolume padaKA tertentu) dengankerapatanair padakondisianomaliair (suhu4,4°C. Dimanakerapatanair padakondisitersebutsebesar1 g/cm3 • BJ = kerapatankayu/kerapatanair suhu4,4 • Kerapatankayu= Beratkayu/Volume Berat Jenis
  • 4. • Kerapatan didefinisikan sebagai massa atau berat per satuan volume ™ Dinyatakan dalam kg/m3 atau g/cm3 Kerapatan = berat (g) volume (cm3) KERAPATAN
  • 5. Berat kayu merupakan jumlah berat dari : –Zatkayu(dindingsel) –Ekstraktif –Jumlahair yang adadidalamkayu. Pada umumnya berat jenis kayu bergantung kepada: •Besarnyasel •tebalnyadindingsel BERAT KAYU BJ dan Porositas Kayu • Kerapatan kayu berhubungan langsung dengan porositas(proporsivolume ronggakosong) • Hubungan langsungan taraproporsi volume rongga dalam kayu(porositas) dan kerapatan terjadi, karena kerapatan zat kayu kering kira-kira sama utk semua spesies, yaitu sebesar1,5 g/cm3 • Berat jenis(BJ) zat kayu kering untuk semua jenis kayu sebesar1,5. • Vol. rongga= (1–BJKT/1,5) x 100 %
  • 6. ZAT KAYU • Kayu terdiri dari sel-sel dan rangka sel sel(dinding sel) yang terdiri atas zat kayu. • Karena itu untuk kayu kering tanur dengan berat dan volume tertentu merupakan petunjuk banyaknya zat kayu (jika variasiadanya ekstraktif diabaikan) dan juga petunjuk volume udara yang ada dalam rongga ronggasel yang kosong Banyaknya zat kayu merupakan petunjuk tentang : • Kekuatan kayu, sifat pengerjaan dan finishingnya• • Rongga dalam kayu, yang banyak menentukanbanyaknya air yang dapat diabsorbsi• • Kerapatan kayu yang sangat menentukanperubahan – perubahan pada dimensi kayu, yangdisebabkan karena perubahan pada kadar airnya.
  • 7. PENTINGN YA BERAT JENIS • Berat jenis: sifatfisikayang paling penting. • Kebanyakansifatmekanikkayusangatberhub ungandenganberatjenisdankerapatan. • Kekuatandankekakuankayunaikdengannaik nyaberatjenis. • Hasilproduksipulp per satuanvolume secaralangsungberhubungandenganberatje nis.
  • 8. PENENTUAN BERAT JENIS • BJ = kerapatankayu/kerapatanair suhu 4,4o c • Kerapatankayu= Beratkayu/Volume • BJ kayubisadiukurpadavolume basah, keringtanurataukeringudara(KA 12%) • Berdasarkanvolume basah, BJ kayumencerminkanberatkayunya(BJ Standard) • Kayuringan: BJ < 0,30 • Kayusedang: BJ 0,36- ,56 • Kayuberat: BJ > 0,56
  • 9. PROSEDUR PENENTUAN BERAT JEN • Prosedur penentuan berat jenis suatu contoh uji kayu ™ Contoh uji berukuran 2×2×2 cm dalam kondisi segar (Ka diatas TJS) atau direndam dalam air 3×24 jam untuk memperoleh kadar air maksimum. • ™ Volume contoh uji dapat diukur dengan metode celup atau rendam (immersion method) atau juga displacement method
  • 10. VARIASI BERAT JENIS .Umurpohon:semakintuaumurpohon,kerapatansemaki ntinggi. •Tempattumbuh(site) : tipe tanah, ketinggiantempat, topografi, komposisitegakan, jaraktanam •Posisikayudalambatang: bagianpangkalbatangmemilikikerapatan(BJ) lebihtinggidaripadabagianujung •Kecepatantumbuh: semakincepatpertumbuhankayu, kerapatansemakinkecil
  • 11. KESIMPULAN Kerapatan dan Kadar Air Kayu Berat jenis dan atau kerapatan kayu merupakan salah satu sifat fisik utama disamping kadar air kayu yang mempunyai korelasi kuat dengan sifat mekanik atau kekuatan kayu. Berat Jenis yang tinggi pada suatu kayu maka kerapatan pada kayu tersebut juga tinggi dan sifat fisika kayu tersebut juga kuat dan bagus , begitupun sebaliknya.