Receiving latex and lumps, module 1

TECHNICAL EDUCATION AND SKILLS DEVELOPMENT AUTHORITY

COMPETENCY BASED LEARNING
MATERIALS

Sector:

AGRI-FISHERY

Qualification Title:

RUBBER PROCESSING NC II

Module 1:

RECEIVING LATEX AND LUMPS

Qualifications and Standards Office
TESDA Complex
East Service Road, South Superhighway
Taguig City, Metro Manila
Tel. No. (02) 893-8281, 8938303
www.tesda.gov.ph

Rubber Processing NC II
LIST OF COMPETENCIES

No. Unit of Competency Module Title Code
1 Receive Latex and Lumps
2 Produce blanketed rubber sheet Receiving Latex and Lumps
Producing blanketed rubber
3 Perform rubber drying operation sheet
Performing rubber drying
operation

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HOW TO USE THIS COMPETENCY BASED LEARNING MATERIAL

Welcome to the module in “Receiving Latex and Lumps”. This module contains training
materials and activities for you to complete.

The unit of competency "Receive Latex and Lumps” covers the knowledge, skills,
behavior and motivations required to prepare rooms for guests. The unit assumes that expert
advice will be available in identifying potential emergencies and in formulating the response
plans. It is one of the specialized modules required to complete the course Housekeeping NC II.

You are required to go through a series of learning activities in order to complete each
learning outcome of the module. Each of the learning outcomes is provided with Information
Sheets (Reference Materials for further reading to help you better understand the required
activities). Follow these activities on your own and answer the self-check at the end of each
learning outcome. You may remove a blank answer sheet at the end of each module (or get
one from your facilitator/trainer) to write your answers for each self-check. If you have
questions, don’t hesitate to ask your facilitator for assistance

Recognition of Prior Learning (RPL)

You may already have some or most of the knowledge and skills covered in this learner's
guide because you have:

 been working for some time
 already completed training in this area.

If you can demonstrate to your trainer that you are competent in a particular skill or skills,
talk to him/her about having them formally recognized so you do not have to do the same
training again. If you have a qualification or Certificate of Competency from previous trainings,
show it to your trainer. If the skills you acquired are still current and relevant to the unit/s of
competency they may become part of the evidence you can present for RPL. If you are not sure
about the currency of your skills, discuss this with your trainer.

At the end of this module is a Learner’s Diary. Use this diary to record important dates,
jobs undertaken and other workplace events that will assist you in providing further details to
your trainer or assessor. A Record of Achievement is also provided for your trainer to
complete once you complete the module.

This module was prepared to help you achieve the required competency in Received
Latex for Rubber Processing NC II. This will be the source of information for you to acquire
knowledge and skills in this particular trade independently and at your own pace, with minimum
supervision or help from your instructor.

 Talk to your trainer and agree on how you will both organize the Training of this unit.
Read through the module carefully. It is divided into sections, which cover all the
skills, and knowledge you need to successfully complete this module.

 Work through all the information and complete the activities in each section. Read
information sheets and complete the self-check. Suggested references are included
to supplement the materials provided in this module.

 Most probably your trainer will also be your supervisor or manager. He/she is there to
support you and show you the correct way to do things.

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 Your trainer will tell you about the important things you need to consider when you
are completing activities and it is important that you listen and take notes.

 You will be given plenty of opportunity to ask questions and practice on the job. Make
sure you practice your new skills during regular work shifts. This way you will improve
both your speed and memory and also your confidence.

 Talk to more experience workmates and ask for their guidance.
 Use the self-check questions at the end of each section to test your own progress.
 When you are ready, ask your trainer to watch you perform the activities outlined in

this module.
 As you work through the activities, ask for written feedback on your progress. Your

trainer keeps feedback/ pre-assessment reports for this reason. When you have
successfully completed each element, ask your trainer to mark on the reports that you
are ready for assessment.
 When you have completed this module (or several modules), and feel confident that
you have had sufficient practice, your trainer will arrange an appointment with
registered assessor to assess you. The results of your assessment will be recorded in
your competency Achievement Record.

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INFORMATION SHEET #1.1
LO1. Receive Latex
Explore Rubber Latex
Objectives:

After reading this Learning material the learner/trainee should be able to:
1. Determine the composition of Natural Rubber Latex
2. Tell the preservation of Latex for processing
Introduction
Latex has a tendency to deteriorate rapidly and coagulate within a few hours of tapping,
but it may be preserved with ammonia to limit bacterial contamination ("latex preservation"). A
small quantity of latex dries on the bark and collected the next morning before tapping ("scrap").

Natural rubber (polymer designation cis-1-4 polyisoprene, empirical formula (C5H8n) is
obtained from the sap ("latex") of several rubber-yielding plants (e.g., Hevea Brasiliensis and
Parthenia argentatum) by coagulation with chemicals, drying, electrical coagulation, and other
processes.

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Latex is a polydispersed colloidal system of rubber particles in an aqueous phase. With
Hevea latex, the dry rubber content varies between approximately 28-40%, although it may rise
to 45-50% after a long period of non-tapping (the statistical purposes, figures for natural rubber
may include the dry rubber content of latex). The rubber produced from latex contains
hydrocarbons and relative small quantities of protein, carbohydrates, resin-like substances,
mineral salts, and fatty acids.

Composition and Types of Natural Rubber

Composition of latex

Table No.1 Table No.2

Elements Percent Constituent %Composition

Proteins 2-2.7% Rubber particles (Cis1, 4 30.0 - 40.0
polyisoprene)
Resins 1.5-3.5%

Sugars 1-2% Protein 2.0 – 3.0

Ash 0.4-0.7% Water 55.0 - 65.0
Steril glycosides 0.1 – 0.5
Steril glycosides 0.07- Resins 1.5 – 3.5
0.47% Ash 0.5 – 1.0
Sugar 0.5 – 1.0
Water 55-65%

Source: K.F. Heinisch, Dictionary of Source: S. S. Ochigbo, et al., Research Paper,
Rubber, 1974 May 2011

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Table 3. Composition of fresh latex- The biological liquid, latex
Norme coagulates within a few hours of
tapping at the instance of naturally
Composition of latex % occurring agents ("field coagulum").
Rubber hydrocarbon 36.00 Coagulation may be prevented by the
Dry rubber content 39.00 addition of preservatives, which offset
Proteinous substances 1.40 enzymatic and bacterial influences. The
Neutral Lipids 1.00 most widely used preservative has
Phospholipids 0.60 been ammonia (the advantage of
Ash 0.50 ammonia lies in the possibility of
Inositols & Carbohydrates 1.60 removing it by aeration for processes
where low ammonia content is
Other Nitrogen compounds 0.30 required).

Total solids content (latex) 41.50 Natural rubber is either exported
as "latex concentrates" or processed
Composition of field latex 41.50 into "dry/solid rubber" (in sheet, crepe
latex or block forms). Latex concentrate is
made from freshly tapped field latex,
uncoagulated; while, dry rubber is
prepared from coagulated field latex
(sheet rubbers and pale crepes) or
remilled rubber sheets (estate brown,
thin brown, thick blanket, and flat bark
crepes). Dry rubber is either visually
graded (sheets and crepes) or
classified by instruments (block rubber).

Water 58.50

Total 100.00

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Types of NR Natural rubber has
Source: UNCTAD secretariat outstanding resilience and
tensile strength, as well as low
heat build-up. The NR latex
has excellent tack (that is, the
ability to stick to itself and to
other materials), which makes
it best suited for pressure-
sensitive adhesives and
excellent water resistance
(where some synthetics
absorb water). The drawback
of natural rubber is moderate
to environmental resistance
factors such as oxidation and
ozone. Moreover, it is scarce
resistance to chemicals,
including gasoline, kerosene,
hydraulic fluids, degreasers,
synthetic lubricants, and
solvents.

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ASSIGNMENT SHEET #1.1

LO1. Receive Latex

Explore Rubber Latex

Objectives:

At the end of this activity, the learner/trainee should be able to:

1. Classify the different approach/procedure in processing
2. Simplify the grade of rubber products after processing

Assignment:

After learning the procedure of rubber processing, find out in your area the process of
natural rubber. Indicate check (‘/) marks for the availability of processing plant with the

following:

Criteria Yes No
Field Latex
Latex concentrates is used in processing area such as:

 Centrifuging process in processing area
 Creaming process in processing area
 Evaporation process in processing area

Criteria Yes No
Field Coagulum
Dry/Solid Rubber in processing area such as:

 Rubber Sheets
o Ribbed Smoke Sheets (RSS)
o Air Dried Sheets (ADS)
o Unsmoked Sheets (USS)

 Crepe Rubber or Milled Rubber

 Block Rubber-Technically Specified Rubber (TSR)

Comments: ________________________________________________________________

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SELF-CHECK SHEET #1.1

LO1. Receive Latex

Explore Rubber Latex

Direction: Answer the following questions and write your answer on the space provided.

___________1. Name at least 2 composition of rubber latex out of 6 compositions.
___________2. The acronym of RSS means?
___________3. What is the Sap of rubber that can be exported in a liquid?
___________4. Additives for the preservation of latex from bacterial contamination.
___________5. The acronym of TSR means?

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KEY ANSWER #1.1

LO1. Receive Latex

Explore Rubber Latex

1. (Name 2 out of 6)-Proteins, Resins, Sugars, Ash, Steril glycosides, Water
2. Ribbed Smoked Sheets
3. Latex Concentrates
4. Coagulum
5. Technically Specified Rubber

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INFORMATION SHEET #1.2

LO1. Receive Latex

Explore Quality Latex for Processing

Objectives:

At the end of this reading activity the learner/trainee should be able to:

1. Classify the different rubber standards
2. Differentiate each of the rubber standards and grades

Introduction

The distinction between industry, national, and international standards is for conceptual
clarity. The Industry standards are incorporated in national and international (ISO) standards.
Testing for compliance under most domestic schemes shall follow ISO methodologies. ISO
standards are used as such or implemented through incorporation in the national standards of
individual countries.

Differences in type/s and grade/s are the major commercial significance. The NR market
is highly fragmented by types, grades, and sizeable variations in trade flows and price
movements (http://unctad.org, 2012).

ISO Standards

To date, ISO's work has resulted in some 127 international standards for "rubber"; 55
standards for "latex and raw rubber"; 30 standards for "rubber compounding ingredients".
Standards have been enacted for all the following fields:

ICS fields Coverage
83.040 Raw materials for rubber and plastics
83.040.01
Raw materials for rubber and plastics in general
83.040.20
Rubber compounding ingredients (Including carbon black, kaolin clay,
83.060 etc.)
Rubber
83.140 Rubber and plastics products (Including films and sheets, laminated
sheets, hoses, seals, etc.)
83.160 Tyres (Including tubes and valves)
83.180 Adhesives
83.200 Equipment for the rubber and plastics industries

Source: UNCTAD secretariat (ISO Standards browsed by ICS fields-International Classification
for Standards)

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National Standards

Individual rubber producing countries are in charge of setting the acceptable limits for
each grade of rubber they produce. The main rubber producing countries have their own
schemes patterned after the TSR scheme. National schemes conform to specifications laid
down by the International Standards Organization (ISO).

Comparison chart

TSR CV Constant viscosity grade
TSR L Latex rubber
TSR 5 Sheet rubber
TSR 10 Field grade material
TSR 20 Field grade material

Latex Concentrates

Unlike sheet and crepe rubber, latex concentrate is graded according to detailed
technical specifications (as for block rubber). Technical specifications are separately
established by both the American Society for Testing Materials (ASTM) and the British
Standards Institution (BSI). National and international standards are substantially identical in
their requirements. Commercial latex is nowadays mainly prepared by centrifugation, with only
two types made on a large scale:

1. HA (high-ammonia) latex, preserved with 0.7% ammonia
2. LA-TZ (low ammonia) latex, preserved with 0.2% ammonia + 0.025% TMTD/ZnO

+0.04 - 0.05% lauric acid as ammonium laureate.

Industry Standards

Two main grading systems exist:

1. Natural rubber graded by the conventional visual standards given in the "Green Book"
of the International Rubber Quality and Packing Conference" VGT-(Visually Graded
Types).

2. Natural rubber graded by technical specifications TSR-(Technically Specified
Rubbers).

1. Visually graded types

Conventional types of rubber (that is, rubber processed into sheet rubber and various
crepes) are still visually inspected and graded according to quality and packing specifications
set in the "International Standards of Quality and Packing for Natural Rubber Grades (The
Green Book)". These standards were first issued and then revised within the framework of the
"International Rubber and Packing Conference", comprising the world's leading rubber
manufacturers, growers and trade associations. The grading system was based on the
classification first developed in 1928 by the US "Rubber Manufacturers Association" (then
"Rubbers Association of America").

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Sheet and crepe rubbers intended for export shall be classified into one of the following
grades:

Standard international grades of NR

Form Types Grades
1X, 1-5
Sheet rubber Ribbed Smoked Sheet (RSS)

Pale Latex Crepe (PLC), thin and tick 1X, 1-3

Sole Crepe (SC) -

Estate Brown Crepe (EBC), thin and 1X-3X,
tick
Crepe
Rubber Thin Brown Crepe 1-4

Thick Blanket Crepe 2-4

Flat Bark Crepe Standard, hard

Smoked Blanket Crepe Pure

Source: International Standards of Quality and Packing for Natural Rubber Grades (The Green
Book).

 Ribbed Smoked Sheets (RSS)

Ribbed smoked sheets are graded on a visual basis as RSS IX, RSS 1, RSS 2, RSS 3,
RSS 4 and RSS 5. After grading the sheets are packed in 50 kg bales, with the grades marked
on the bales.

 Crepe Rubber

Crepe rubber is either made from latex ("Latex Crepes") or processed from cup lumps,
scrap and cuttings of ribbed sheet rubber ("Field Coagulum Crepes", or "Remilled Crepes").

 Latex crepe is graded as "Pale Latex Crepe" (PLC, from fresh field latex) and "Sole
Crepe" (SC, obtained from dried PLC).

 There are 8 grades under the PLC category, with the purest being 1X (the difference
between thick and thin grades is only in thickness).

 Pale and sole crepes are more specialised than remilled crepes, and yield a higher
premium. With both latex crepes, and especially the sole crepe, the colour represents
an important element in marketing and pricing (a higher premium being obtained with
a lighter coloured product).

Remilled crepe rubber prepared from field coagulum materials fall into five categories
(further graded on a visual basis):

1. Estate Brown Crepe (EBC), thin and tick (made from lump and other high grade
rubber scrap (field coagulam) generated on rubber estates) - 6 grades

2. Thin Brown Crepe (Remills), (derived from wet slab coagulum, unsmoked sheets and
cup lumps) - 4 different grades

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3. Thick Blanket Crepe (Ambers), (wet slabs, unsmoked sheets or other high grade
scraps) - 3 grades

4. Flat Bark Crepe, (processed from all types of low grades scrap including earth scrap)
- 2 grades

5. Pure Smoked Blanket Crepe, (exclusively derived from ribbed smoked sheet or
cuttings).

2. Technically Specified Rubber (TSR)

The conventional grading system outlined above had many disadvantages, in that it was
based on subjective assessments and only recognised visual distinctions that could not have
much technical significance. A major step towards evolving a more sophisticated classification
for rubber was the development of a grading system strictly based on technical specifications.
The move away from visual grading to technical specifications originated in Malaysia in the
1960s with the "Standard Malaysian Rubber" (SMR) scheme. This prompted producers in other
countries (notably, Indonesia and Thailand) to develop similar technical specifications for
grades. "Technically Specified Rubbers" (TSR) - that is, rubbers graded on the basis of
technical parameters - now account for the bulk of traded rubber. Standardized international
contracts for such rubber were first adopted by the International Rubber Association at its
inaugural meeting on 24 September 1971.

Rubber is technically specified according to the following sets of rules, which are
incorporated and detailed in the national standards of individual countries.

Technical specifications: TSR is graded on technical properties, rather than on visual
distinctions. Technical parameters for grading are expressed as either maximum or minimum
thresholds (detailed under national TSR schemes). For each grade, the dirt content, ash
content, volatile matter content, nitrogen content, plasticity, and color are tested by instruments.
Testing for compliance shall follow ISO test methods.

ISO has specified 6 different grades of TSR, namely;

1.) TSR L (high quality and light colored rubber prepared from latex),
2.) TSR CV (viscosity-stabilized high quality latex rubber),
3.) TSR 5 (good quality latex rubber, darker than TSR L),
4&5).TSR 10 and 20 (good quality grades derived from field coagulum, suitable for

general purpose uses),
6.) TSR 50 (up to 0.50 % wt dirt content). The specifications and characteristics of TSR

are detailed in table 1.

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Table 1. Natural Specification - Norme
Limits for grade of Rubber latex

CHARACTERISTICS CV L 5 10 20 50 Test

Method

green green green brown red yellow

Dirt Content (Max) 0.05 0.05 0.05 0.10 0.20 0.50 180 249

Initial plasticity (Min) - 30 30 30 30 30 180
2007

Nitrogen Content (Max) 0.6 0.6 0.6 0.6 0.6 0.6 180
2930

Volatile Matter Content 0.8 0.8 0.8 0.8 0.8 0.8 180

(Max) 1656

Ash content (Max) 0.6 0.6 0.6 0.6 0.6 0.6 180 248

Color index (Max) - 6 - - - - 180 247

Mooney viscosity 60 ₊ 5 180
4460

M (1 ₊ 4) 100 ⁰C 180 289

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OPERATION SHEET #1.2

LO1. Receive Latex

Explore Rubber Latex

Objective:

At the end of this activity, the learner/trainee should be able to:

1. Describe latex to rubber bale process in processing plant set-up.

Introduction:

Latex is a milky colloid produced by some plants. The plants would be ‘tapped’, that is,
an incision made into the bark of the tree and the sticky, milk latex sap collected and refined
into a usable rubber.

Latex needs to be processed before it can be sold as rubber. In the rubber processing
plant, it will undergo several processes such as receiving, filtrating, coagulating, milling,
shredding, drying and packing (See illustration
below).

Procedure

2 3
1

Latex from Processing plant Coagulation refers Milling is done to
rubber tree receives and to the partially remove
plantation the water content
checks quality of solidification
7 field latex process of latex of the lumps
(latex to lumps) (lumps to
6
5 blanketed sheets)

4

Rubber is packed After drying the Shredded rubber Shredding of
and stored. rubber is pressed are dried
Code No. blanketed sheets
into bale.
is done to ensure

and shorten
drying period of

lumps

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Evaluation:

Project

Check the process of processing latex to coagulum in processing plant using the criteria
below (Gaining all “YES” answers indicate that you have observed the job according to the
required standard. Gaining “NO” answer will require you to correct your observation).

Performance

Criteria Yes No
 Tools and Equipment for weighing are in place
 Filtration materials is available using prescribe mesh
 Coagulation tank/pond is clean
 Prescribed coagulation solution/materials are ready and

available

While the personnel performing the activity in processing the latex, it is important to
assess the process using the criteria below (Gaining all “YES” answers indicate that you
observed the job according to the required standard. Gaining “NO” answer will require you to

correct your observation).

Criteria Yes No
 Latex receive are weigh and measure following prescribed

standard
 The latex are strain in a clean filtration mesh
 The dilution and standardization is perform following the

standard procedure
 Latex are coagulate with prescribe coagulating materials in a

tank/pond

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SELF CHECK SHEET #1.2

LO1. Receive Latex

Explore Quality Latex for Processing

Direction: Answer the following questions and write your answer on the space provided.

___________1. Name the 2 types of centrifugation process in latex concentrates.
___________2. Set of guidelines by individual countries for rubber processing.
___________3. Name 3 out of 6 rubber grades base on TSR schemes.
___________4. The acronym PLC means?
___________5. The general international guidelines for Rubber industry

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ANSWER KEY #1.2

LO1. Receive Latex

Receive Latex

Explore Quality Latex for Processing

1. High ammonia & low ammonia
2. National Standard
3. TSR CV, TSR L, TSR 5, TSR 10, TSR 20, and TSR 50-(name 3 out of 6)
4. Pale Latex Crepe
6. ISO Standard

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INFORMATION SHEET 1.3

LO1. Receive Latex

Type of Dry Rubber Content-(DRC) Determination
Source: REJI KUMAR, R., Research Paper, December 2009

Objectives: At the end of this Learning material the learner/trainee should be able to:

 Tell the different theories and practices of instrumentation and measurement
techniques that are fast, accurate and economical for the determination of DRC
in natural rubber latex.

 Discuss the information of testing DRC that are viable and applicable in
processing area.

Introduction

The DRC components can be determine in both processes of field latex materials-the
liquid latex concentrate and solid dry rubber or field coagulum. Dry rubber is obtained by
coagulation which entails treating the latex with suitable agents such as acetic or formic acid to
yield crepe or crumb (Yip and Cacioli, 2002 as stated in Ochigco, 2011).

Importance of Dry Rubber Content (DRC)

Dry Rubber Content or DRC is an important parameter for natural rubber latex (NRL),
which is to be measured quickly for various purposes for the rubber industry. DRC is defined as
the mass in grams of solid rubber present in 100 g of latex. The DRC of latex varies depending
upon season, tapping system, weather, soil conditions, clone of the tree and environmental
conditions. The DRC of Hevea latex is a very familiar term to all in the rubber industry. It is
probably one of the few properties of latex first recognized and widely used for trade and
processing commencing from commercial exploitation of Hevea trees. The DRC is an essential
parameter for ensuring fair prices for latex during commercial exchange. It has been the basis
for incentive payments to tappers who bring in more than the daily agreed pound age of rubber
latex. It is an important parameter that determines the yield of useful rubber latex and a
requirement for various decisions in processing of industrial processes in rubber products
manufacturing.

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Information Sheet 1.3

Techniques to determine DRC of latex

1.) The standard laboratory method

The standard test procedure to obtain DRC is based on “British standard". The procedure
is based on Malaysian Standard MS 3:35:1975 entitled Methods of Sampling and Testing
Concentrated Natural Rubber Latices, the British Standard BS 1672:1972 entitled "Methods
for Testing Natural Rubber Latices”, the American Society for Testing and Materials ASTM D
1076:77 entitled “Rubber - Concentrated, Ammonia Preserved, Creamed and Centrifuged
Natural Latex” and the International Standard ISO 126-1972 (E) 46.

How it is used: The general procedure in the laboratory is to coagulate a known weight of
representative sample of the latex with dilute acetic acid, then, sheet the coagulum and let it dry
in the oven at 75ºC for nearly 12 hours. The DRC of the latex is therefore given by the
percentage by weight of the dry sheet over the weight of latex taken. Contrary to this method
for field used with the following reasons’.

(1) Establishment of a laboratory equipped with an analytical balance, electric oven and
water bath cannot operate in the field where there is not even electricity.

(2) It requires a heavy capital investment for the establishment of electricity and equipment
and beyond the ability of small holders and many small establishments.

(3) The other drawback of this method is that it requires a skilled operator to operate and
maintain the laboratory equipment.

(4) The test method results cannot be obtained on the day of testing because test samples
are required to dry in the oven overnight.

(5) Payments cannot be made to the tappers on the day of tapping due to the reason cited
as (4) above.

(6) The whole operation of test takes more than 16 hours and cannot be performed in the
presence of the tappers, and so the tappers need not accept the test method adopted.

2.) The hydrometer metrolac method

The use of hydrometers to evaluate the DRC in latex appears to have begun with
Eaton's publications' ‘v’-(known as vertical). Hydrometers, usually known at rubber plantations
by the names, Metro/ac, Latexometer or Simp/exometer, are commonly used as the easiest
method of obtaining an approximate estimate of the dry rubber content of latex. Metrolac, is an
instrument use to determine the density difference of rubber and water. It is used for quick
DRC measurement in some estates.

Information Sheet 1.3

How it is used: One part of well stirred field latex is mixed with two parts of water. The
diluted latex is filled in a tall cylindrical jar with a diameter of around 7.5 cm. Air bubbles and
froth remaining on the latex surface is removed by blowing off the surface. The Metrolac, after

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washing in water, is immersed in the latex and allowed to come to rest without touching the side
of the cylinder. The reading on stem is noted. The DRC of the latex is obtained by multiplying
the reading by three (since two parts of water are added) and dividing by ten. The method,
though quick, simple and easy, is not very accurate. The error is in the range of 5 to 10 percent.
However, this method is still in use in rubber estates for assessing the DRC of latex for making
sheets on a large scale and also for calculating the quantity of rubber brought in by a tapper. In
order to minimize the error, a correction factor is applied based on the actual laboratory
estimation of the DRC of bulk latex.

The following reasons of measurement errors using Metrolac

1. The density of the rubber particles in latex is not precisely known, it varies with
what we choose to define rubber. Available evidence indicates that the density of purified
rubber at 29°C is about 0.902 to 0.9035. Further, observations’ on normal latex and on
purified centrifugal concentrates that the density of rubber may increase with decreasing
DRC of the parent latex, presumably due to adsorption of more serum solids. In both
investigations the density of the rubber phase is estimated indirectly. Furthermore, no
reliable data is available showing correlation of densities of normally prepared rubbers
with the DRCs of the latices from which they are coagulated. It should be recognized that
this is to be taken only as an empirical value for this purpose and not as an unbiased
estimate of the true density of rubber.

2. The serum in latex is not a single substance like water, but is a solution of
mixed ingredients, proteins and salts, and unfortunately there is no satisfactory evidence
to show how its density varies between different estates, clones, season etc. However,
available evidence suggests that serum density is not directly correlated to DRC of latex.

3.) The Latex film dialysis

This method is based on the customary 'total solids' determination procedure. The
principle of coagulation dialysis experiments is with an aim to replace washing and rolling
operation. The previous method the coagulum was not passed between rolls but mechanical
treatment is not omitted. Besides, drying is carried out at 70ºC, handling of coagulum differs
from the latex film dialysis method.

Information Sheet 1.3

How it is used: In latex film dialysis method, sample is prepared by adding up to 4 ml of
20% w/v ammonium chloride solution in to a petri dish of 8.5 cm internal diameter. In fresh
ammoniated field latex and fresh unammoniated field latex, 5 ml and 3 ml respectively of 2%
w/v formic acid solutions are used. About 3 grams of concentrate or 5 grams of field latex -
weighed to the third decimal – are slowly added, while swirling the dish constantly. The mixture
is spread as uniformly as possible over the whole bottom of the dish, coagulating in to a well
formed film. Heating in a vented air oven at 100-1050 ºC for about 15 minutes accelerates the
coagulation, completion of which is indicated by the appearance of a clear serum. The film is
further fixed between two pieces of small glass triangle, and then left submerged at the bottom

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of a basin (for 60 minutes if the ammonium chloride coagulant is employed, or for 30 minutes if
the formic acid coagulant is applied). The basin is continuously filled with clean, running water
(only in case of emergency, it could be periodically filled). Thereafter, the film is drawn out of the
water, and its surface moisture is removed by blotting with a clean cloth or filter paper.
Subsequently, it is dried at 100-105 DC for approximately 2 hours in the drying oven, cooled to
room temperature in desiccators, weighed and the DRC determined.

4.) The specific heat method

The 'method of mixtures' measures the initial masses and temperatures of a quantity of
latex or crepe and hot or cold water with which the latex is to be mixed, and final temperature
after mixing in a pre – calibrated vessel. The method of specific heat of latex or crepe is
computed after allowing the heat absorbed by the flask. It is necessary before the determination
of specific heat of any sample, to determine the quantity of heat that will be absorbed by the
material of the flask. The assumption of hot water is to be mixed with the sample

How it is used: Once the flask constant, K, or heat gain factor has been determined by
heat balance using water as calories per degree of centigrade temperature rise, the specific
heat SR of dry rubber samples can be readily obtained by similar heat balances using dry
rubber samples and hot water. Having determined K and SR, the specific heat and DRC of wet
samples or latex can then be obtained by mixing hot water and appropriate heat balances. The
dry rubber content of NR latex or wet crepe was found to be a linear function of specific heat. In
the measurement of DRC using specific heat method is fairly accurate with a standard deviation
of 0.7% for latex and 1% for wet crepe. Operation time for specific heat method is about 7
minutes and about 11 minutes for latex and crepe respectively. The results indicate that the
technique can be utilized for rapid measurement of DRC in the laboratory.

Information Sheet 1.3

5.) The titration method

In NR latex, the rubber particles have on their surface an adsorbed layer of proteins and
other ions that are negatively charged. The quantity of adsorbed anions in turn depends on the
size and number of particles present in unit volume of latex and hence on the DRC of the latex.
Since coagulation is a process in which adsorbed anions formed from different sources in latex
are neutralized by a coagulant, there can be a relation between adsorbed anions and amount of
coagulant utilized for coagulation. If latex can be coagulated immediately, then a correlation can
be found between the dry rubber content and the amount of coagulant required for coagulation.
Normally, fresh latex coagulation is a slow process and hence it has to be sensitized for quick
coagulation. It has been reported that latex containing fatty acid soaps and other surfactants
gets coagulated very fast by addition of acids.

How it is used: When fatty acid soaps are added to latex, the fatty acid anions cause
displacement of protein molecules and get strongly adsorbed on rubber particles, In this way
the protein - stabilized latex gets transformed into soap - stabilized system. When acid is added

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to soap treated latex the adsorbed soap anions react with acid to form unassociated fatty acid,
thus depriving the latex particles of stabilizers, As a consequence, latex coagulates
immediately. Assuming uniform size and spherical shape for rubber particles in latex, the
number of particles present in unit volume of latex (N) and volume fraction of the dispersed
polymer (φ) are related by the equation.

N = 6φ/TT x3..... 1.2

Where:
x is the diameter of the particles
φ is a parameter related to DRC
N is proportional to the quantity of soap adsorbed

The above two assumptions are not fully true for NR latex particles, Even though there
is variation in particle size, it is reported that latices of different clones and different age groups
have maximum number of particles with size in the range of 1 μm, Similarly the shape of rubber
particles may vary but the majority are of spherical shape. Considering these factors, Equation
(1.1) can become valid for fresh NR latex. As DRC of latex increases, the total adsorbed soap
increases and the acid required to coagulate latex also increases. Thus, from the volume of
acid required for coagulation of latex, it is possible to determine the DRC of latex.

Information Sheet 1.3

6.) The dielectric method

An elementary parallel plate capacitor consists of two conducting plates and electrically
isolation from one another by an insulating medium. The capacitance (C) of this elementary
capacitor is proportional to (i) the cross - sectional area A of the plates, (ii) the permittivity (or
dielectric constant K) of the insulating medium and (iii) the reciprocal of the separation, t,
between the plates. The relation is given by:

C = KA. . . . 1.3
t

How it is used: The area of the plates and the separation between them are kept
constant, the capacitance of the capacitor is directly proportional to the dielectric constant or
permittivity of the medium. If there is a direct relation between the DRC and dielectric constant
of latex, then the same relationship holds good for the capacitance and DRC of rubber latex
used as the dielectric. Hence it is possible to calculate the DRC of latex by measuring the
capacitance of latex using capacitive techniques.

7.) The microwave technique

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Feb. 1, 2012 24

The parameter of related to non-magnetic materials which describes their interaction with
an electromagnetic field is the permittivity ɛ = ɛ'- j ɛ", where E' is the dielectric constant and
the imaginary part ‘E’ is the loss factor. The permittivity is a measure of the polarization in an
applied electromagnetic field. As the frequency of the applied field increases, the molecules are
unable to re-orient completely before the field reverses. At these frequencies, the orientation of
permanent dipoles no longer contributes to the dielectric constant and it is dissipated as heat.
Physically, the dielectric constant represents the ability of a material to store electric energy
while dielectric loss represents the loss of electric field energy in the material.

8.) The low resolution pulse NMR technique

The basic theory of NMR and the determination of the solid contents of rubber latex by
means’ of pulsed NMR99 spectrometer using Bruker Minispec spectrometer. The brief
description of the method of pulsed NMR is necessary to understand based on its uses and
technique. This is the most expensive of all DRC testing method.

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Self check 1.3
LO1. Receive Latex

Type of Dry Rubber Content-(DRC) Determination

Direction: Answer the following questions and write your answer on the space provided.

________ 1. The most expensive process of determining DRC by using resolution
pulse.

________ 2. The process of determining DRC which is the weight percentage from
taken coagulum over the dry sheet from oven.

________ 3. The DRC content using electric conductor.
________ 4. The DRC reading acquired when an instrument submerge into the

mixture of latex with two parts of water solution.
________ 5. The cost of price of rubber in commercial exchange is dependent on

the content of latex.

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Answer Sheet 1.3
LO1. Receive Latex

Type of Dry Rubber Content-(DRC) Determination

1. NMR technique
2. Standard Laboratory method
3. Dielectric technique
4. Hydrometer Metrolac method
5. DRC

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Feb. 1, 2012 27

Assignment Sheet 1.3
LO1. Receive Latex

Type of Dry Rubber Content-(DRC) Determination

Objectives: At the end of this learning activity the learner/trainee should be able to:

 Perform instruction in getting DRC using Standard Laboratory Method
 Demonstrate the determination of DRC

Assignment: After learning the procedure of getting the DRC of Latex using Standard
Laboratory Method, you are in title to perform on your own.

1. Take a portion of diluted latex (1 cup) in coagulating pond/container.
2. Sheet the coagulum to remove excess water and acid.
3. Weigh the sheet coagulum in order to certain the weight of rubber for recording.
4. Dry the sheet rubber in the oven for 75ºC for about 12 hours.
5. Weigh and record the weight of dry sheet.
6. Used the formulation derive from the percentage of weight of rubber;

 DRC % = Weight in grams of Dry Rubber X 100
 Weight in grams of rubber taken

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Feb. 1, 2012 28

Evaluation:

Project
Check your work using the criteria below (Gaining all ”YES” answers indicate that

you have done to the required standard. Gaining “NO” answer will require you to correct your

work).

Criteria YES NO
 Well function weighing scale
 Availability of oven and electricity
 Taken portion of coagulum is already weighed
 Availability of roller machine for sheeting of

coagulum
 Availability of water supply
 Recording materials for documentation

Performance

In performing the activity, it is important that you assess your performance
following the criteria. Your overall performance of “YES” means that you are ready to proceed
to next learning level. Having performances of “NO” means you need to repeat the activity to

improve your performance.

Criteria YES NO
 Sheets the coagulum following prescribe

procedure
 Portion of taken coagulum is weighed following

prescribed procedure
 Oven is pre-heated following safety practices
 DRC is attained based on standard procedure
 Proper housekeeping and cleanliness is

practiced at all times

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Information Sheet 2.1

LO-2 Explore Rubber Lumps

Objectives: At the end of this learning activity, the learner/trainee should be able to:
 Distinguish the properties of field coagula
 Tell the classification of lumps

Introduction
The natural rubber processing factories obtain the raw materials collected from trees

either in large plantations or from smaller independent holdings, in one of two forms, field
coagula or field latex. The lower grades of material are prepared from field coagula. Field
coagula consist of cup lump, tree lace or cup lace, smallholders lump and earth scrap. Each of
these four types has significantly different properties.
The Field Coagula
* Cup-lump is produced when the latex is left

uncollected and, due to bacterial
action, is allowed to coagulate on the
side of the collecting cup.

* Lace is the coagulum strip that the tapper peels
off the previous cut before making a
new cut. This is the coagulated
residue left around the bark of the tree
where the cut has been made for
tapping. The formation of lace seals the
latex vessels and stops the flow of
rubber latex. It would typically be
processed with cup-lump.

Information Sheet 2.1

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Feb. 1, 2012 30

* Smallholders’ lump is a lump produced by
smallholders who collect rubber from
trees a long way away from the nearest
factory. Many smallholders’ grow in
remote areas, tap dispersed trees on
their way to work in the fields and
collect the latex (or the coagulated
latex). It is often impossible to preserve
the latex sufficiently to get it into a
factory for latex processing, in time to
be used for a high quality products, and
as the latex would anyway have
coagulated by the time it reached the
factory.

* Earth scrap is the material that gathers around
the base of the tree. It arises from latex
overflowing from the cut and running
down the bark of the tree; spillage from
tappers’ buckets during collection. It
contains earth and other contaminants
and has variable rubber content
depending on the amount of
contaminants mixed. Earth scrap is
collected by the field workers two or
three times a year and may be cleaned
in a scrap-washer to recover the
rubber, or sold off to a contractor who
will clean and recover the rubber.

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Information Sheet 2.1
Classifications of cup lumps
Class A – two-weeks old loose cup-lumps

Class B – one month old loose cup-lumps

Class C – more than one month old loose cup-
lumps

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Feb. 1, 2012 32

Self-Check sheet 2.1

Explore Rubber Lumps

Direction: Answer the following questions and write your answer on the space provided.
________1. Lumps produce by farmers in remote areas.
________2. The class of two weeks loose cup-lump in bulking tank.
________3. Latex left uncollected and coagulate in the collecting cup.
________4. A scum left around from the bark of the tree and seals the latex vessels
from flowing.
________5. The classification of a month old loose cup-lump.

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Feb. 1, 2012 33

Key Answer 2.1

Explore Receive Rubber Lumps

1. Smallholders’ lump
2. Class A
3. Cup lump
4. Lace
5. Class C

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Feb. 1, 2012 34

Job sheet 2.1

Receiving Rubber Lumps for processing

Objectives: At the end of this activity, the learner/trainee should be able to:
 Learn to receive lumps and
 Record the weighed lumps

Tools, Materials and Equipment: 1 unit
1 unit
Flatform/Weighing Scale 1 unit
Record books
Storage area/Bulking area

Evaluation:

Project
Check your work using the criteria below (Gaining all “YES” answers indicate that

you have done the job according to the required standard. Gaining “NO” answer will require you
to correct your work.

Procedure:

1. Lumps are segregate according to:
 Owner
 Clone type
 Receive date (optional)
 Weight (optional)

2. Lumps are weigh and record for data
gathering and for documentation
purposes.

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Feb. 1, 2012 35

Evaluation:

Check your work using the criteria below (Gaining all “YES” answers indicate that you
have done the job according to the required standard. Gaining “NO” answer will require you to
correct your work.

Criteria YES NO

 Separate lumps according to owner, clone, etc.

 Weigh cuplumps/lumps and record according to industry
procedure

 Wash cuplumps/lumps in blended tank for processing
 Safety and cleanliness is always observe in receiving area

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Feb. 1, 2012 36

Performance

To perform this activity, it is important to assess your performance following the criteria
below. An overall performance of “YES” means that you are ready to proceed to next learning
level. And for “NO” means you need to repeat the activity to improve your performance.

Criteria YES NO

 Segregated lumps are placed in a bulk of respective owner,
clone, etc.

 Lumps are weighed and weight are recorded according to
industry procedure

 Prepared lumps are washed and blended in tank for processing
 Safety and cleanliness is always observed in receiving area

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Feb. 1, 2012 37

REFERENCES

Published Materials

ALCALA, E.A. et.al. 2007. Rubber: Manual for Rubber Smallholders in the Philippines, USM
and PRBI, Kabacan North Cotabato.

CALLANO, R.S. et.al. 2008. Handbook on Rubber Production: 3rd Edition, PICRI and USM,
Kabacan, North Cotabato.

Unpublished Material(s)

Kumar, R.R. 2009. Design and Development of Instrumentation Systems to determine the Dry
Rubber Content in Natural Rubber Latex, PDF file of Thesis for the degree of
Doctor of Philosophy, Cochin University of Science and Technology, Cochin, Kirala,
India.

On-line Network
Asia’s Standard for Natural Rubber

Available at: http://www.astlettrubber.com/nr/index.html
Date Retrieved: January 2012
International Grade Descriptions for Rubber
Available at: http://rubberboard.org.in/TreeView.asp?selectedid=189&Id
Date Retrieved: February 2012
Latex Preservation and Latex Properties

Available at: http://rubberboard.org.
Date Retrieved: January 2012
Natural Rubber Latex Peripherals
Available at: http://aalatex.com/content/comments.asp?id=193
Date Retrieved: February 2012

Processing of Natural Rubber

Available at: http://ecoport.org

Date Retrieved: January 2012

Quality of Rubber products and Technology of Rubber

Available at: http://unctad.org/infocomm/anglais/rubber/technology.htm

Date Retrieved: January 2012

Rubber Graphics and Pictures

Available at: www.Alibaba.com
www. Mywebsearch.com

Date Retrieved: February 2012

The NR Production
Available at: http://www.bouncing-balls.com/serendipity/pictale.htm
Date Retrieved: January 2012

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Feb. 1, 2012 38

Handouts and Presentation slides

Rubber Processing
Department of Agriculture, Provincial office, Ipil, Zambaonga Sibugay

Rubber Graphics and Pictures
Philippine Tested Rubber

PPRPC, La paz, Zamboanga Sibugay

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Feb. 1, 2012 39

ACKNOWLEDGEMENT

We would like to recognize and give due acknowledgement to the following
writers and trainers of the Kabasalan Institute of Technology, a TESDA-Administered
School in Zamboanga Sibugay, who unselfishly shared their technical expertise in
developing this Competency Based Learning Material to be used in training on Rubber
Production.

Developer/Writer Module
Angelito A. Aballe Establishing rubber budwood and
seedling nursery
Veronica A. Rasonable and Planting rubber trees/ rubber seedlings
Angelito A. Aballe
Performing budding operation
Angelito A. Aballe Harvesting Latex

Salvacion G. Casalem and
Angelito A. Aballe